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Operative Orthopaedics. Second Edition" edited by Michael W. Chapman . . ]. B. lippincott Company. Philadelphia © 1993. CHAPTER 61 DEFORMITY' CORRECTION BY THE ILIZAROV TECHNIQUE Dror Paley Kevin D. Tetsworth Definition of Deformity Evaluation of Lower Limb Deformities Indications for Correction of Lower Limb Deformities Preoperative Planning Planning the Level of Osteotomy Other Factors in Determining the Level of the Osteotomy Determining the True Plane of the Deformity Translation Deformities . Angulation/Translation Deformities Multi-Apical Angular Deformities Joint Laxity Deformities of the Knee Indications for Distraction Osteotomy Versus Conventional Osteotomy . Basic Principles of Deformity Correction Using Circular External Fixation Center of Rotation Hinge Technique Push/PullConstructs Construct Considerations for Rotational Deformities Translational Deformity Correction Order of Correction for Complex Deformities Rate of Correction Deflnition of Deformity A limb deformity is a deviation from normal anatomy. The' deformity may include abnormalities of length, rotation, translation, or angulation (fable 61-1). Several other com- ponents of limb deformity should also be considered in in- dividual cases: deficiency, malformation, contour, circum- ference, and proportion. . To define a deformity, we need a concept of normal anat- omy for comparison. In the lower limb, this usually is eval- uated from long standing anteroposterior and lateral radio- graphs. The two considerations in evaluating the frontal plane mechanical axis of the lower extremity are joint alignment and joint orientation. 30 The normal alignment of the hip, knee, and ankle joint centers is colinear. Frontal plane de- formities lead to a mechanical axis deviation, which primarily affects the knee but also affects the subtalar, ankle, and hip joints. Normally the line of weight-bearing force from the ankle to the hip joint passes through the medial tibial spine in the center of the knee. 12 23 In mechanical axis deviation, . it passes medial or lateralto the center of the knee. The second consideration is, the orientation of each joint to the mechanical axis line. Each joint has a normal ana- tomical inclination to both the mechanical and anatomical axis of the limb segment (Fig. 61_1).30 In the tibia the me- chanical and anatomical axes are the same, but in the femur they are different. The mechanical axis of tHe femur is defined as the line from the center of the hip to 'the center of the knee. This usually sub tends a6 0 angle to the anatomical axis of the femur, which runs from the piriformis fossa to . the center of the knee joint. The knee joint line. has been measured to be about 3 ° off the perpendicular such that the distal femur is in slight valgus and the tibial diaphysis in slight varus. Krackow feels that the 3° inclination evolved to keep the knee joint horizontal (parallel to the ground) with walking. 19 On walking the feet progress along the same line, with the leg inclined to the vertical at about 3°. Due to the 3 0 of varus attitude of the lower limbs, the knee joint maintains a parallel inclination to the ground during gait. In stance with the feet as wide apart as the pelvis and. the 883
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Page 1: DEFORMITY' CORRECTION BY THE ILIZAROV TECHNIQUE

Operative Orthopaedics. Second Edition"edited by Michael W. Chapman .

. ]. B. lippincott Company. Philadelphia © 1993.

CHAPTER 61

DEFORMITY' CORRECTIONBY THE ILIZAROV TECHNIQUEDror PaleyKevin D. Tetsworth

Definition of DeformityEvaluation of Lower Limb DeformitiesIndications for Correction of Lower Limb DeformitiesPreoperative Planning

Planning the Level of OsteotomyOther Factors in Determining the Level of the OsteotomyDetermining the True Plane of the Deformity

Translation Deformities .Angulation/Translation DeformitiesMulti-Apical Angular DeformitiesJoint Laxity Deformities of the KneeIndications for Distraction Osteotomy Versus

Conventional Osteotomy .Basic Principles of Deformity Correction Using Circular

External FixationCenter of Rotation Hinge TechniquePush/PullConstructsConstruct Considerations for Rotational DeformitiesTranslational Deformity CorrectionOrder of Correction for Complex DeformitiesRate of Correction

Deflnition of DeformityA limb deformity is a deviation from normal anatomy. The'deformity may include abnormalities of length, rotation,translation, or angulation (fable 61-1). Several other com-ponents of limb deformity should also be considered in in-dividual cases: deficiency, malformation, contour, circum-ference, and proportion. .

To define a deformity, we need a concept of normal anat-omy for comparison. In the lower limb, this usually is eval-uated from long standing anteroposterior and lateral radio-graphs. The two considerations in evaluating the frontal planemechanical axis of the lower extremity are joint alignmentand joint orientation. 30 The normal alignment of the hip,knee, and ankle joint centers is colinear. Frontal plane de-formities lead to a mechanical axis deviation, which primarilyaffects the knee but also affects the subtalar, ankle, and hipjoints. Normally the line of weight-bearing force from theankle to the hip joint passes through the medial tibial spinein the center of the knee.12•23 In mechanical axis deviation,

. it passes medial or lateralto the center of the knee.The second consideration is, the orientation of each joint

to the mechanical axis line. Each joint has a normal ana-tomical inclination to both the mechanical and anatomicalaxis of the limb segment (Fig. 61_1).30 In the tibia the me-chanical and anatomical axes are the same, but in the femurthey are different. The mechanical axis of tHe femur is definedas the line from the center of the hip to 'the center of theknee. This usually sub tends a 60 angle to the anatomicalaxis of the femur, which runs from the piriformis fossa to .the center of the knee joint. The knee joint line. has beenmeasured to be about 3° off the perpendicular such that thedistal femur is in slight valgus and the tibial diaphysis inslight varus. Krackow feels that the 3° inclination evolvedto keep the knee joint horizontal (parallel to the ground)with walking. 19 On walking the feet progress along the sameline, with the leg inclined to the vertical at about 3°. Dueto the 30 of varus attitude of the lower limbs, the knee jointmaintains a parallel inclination to the ground during gait.In stance with the feet as wide apart as the pelvis and. the

883

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886 RING FIXATION AND DISTRACTION TECHNIQUES

TABLE 61-2. Clinical Evaluation Algorithms for Lower Limb Deformity

Position 1: Standing face forward

1. Frontal plane alignmenta. Pelvic tiltb. Genu varurn/valgumc. Foot varus/valgus/abducrus, adducrus/supinadon/pronationd. Obvious diaphyseal deformitye. Trendelenburg sign (immediate; delayed)

2. Rotation alignment. a. Patellar orientation (forward, in, out)b. Foot oriemation (forward, in, out)

3. Length discrepancya. Pelvic tiltb. Knee flexion long legc. Equinus stance short legd. Blocks for measurement

Position 2: Standing Lateral Views1. Sagittal plane alignment

a. Spine lordosis/kyphosisb. Hips: flexion deformityc. Knees: flexion or recurvatum deformityd. Ankles: equinus or calcaneuse. Foot arch: cavus or flatf. Obvious diaphyseal deformity

position 3: Standing Posterior View

1. Frontal plane alignmenta. Scoliosisb. Pelvic tiltc. Genu varurn/valgumd. Heel varus, valgus, equinus

Position 4: Walking1. Foot progression angle/patellar progression angle2. Gait pattern (stance/swing), eg Trendelenburg, antalgic, short leg, lurch

may be necessary in both flexion and extension to evaluatelimitation of motion and its etiology (bone or soft tissue).

Torsional deformities can be quantified using some specialradiographic views or CT scanning.16,26 Clinical examinationis still the best method to evaluate and quantify torsionaldeformity (Fig. 61-7) .ll,26 Three-dimensional reconsnuctionCT scans are useful for the assessment of intra-articular de-formities, especially those associated with joint deficiencies.Three-dimensionalCT scans may one day be useful for plan-ning deformity corrections.

Stress x-rays, arthrographic studies, and MRI may be usefulto visualize the contour of the joint surface and assess jointlaxity, contracture, and luxation. .

It is also important to .evaluate lateral and medial laxityof the knee joint (Fig. 61-8). The joint-lines of the distalfemur and proximal tibia will be at an angle to each otheron a standing radiograph; stress views will reveal the fullextent of the laxity. If this is not corrected together with thedeformity, then abnormal loading of the plateaus will con-tinue despite limb realignment.

Indications for Correctionof Lower Limb Deformities

Deformities of the lower limb may be symptomatic orasymptomatic. Deformity symptoms include pain and in- .

Position 5: Sitting1. Examination of the foot

a. Subtalar range of motion (ROM)b. Ankle range of motion/stabilityc. Forefoot and toesd. Malleolar position (medial vs lateral)

Postion 6: Supine1. Knee ROM: flex/extension2. Hip ROM

a. Abduction/adductionb .. Flexionc. Thomas test for fixed flexion deforrniry

3. Patellar orientation relative to foot4 .. Knee stability exam (tibiofernoral, patellofemoral)5. Neurovascular exam6. Limb length measurement7. Femoral length (Galleazzi's sign)8. Tibial length (knee heights)9. Hamstring muscle length tests.. a. Straight leg raising limit

b. Popliteal angle .10. Calf and thigh circumference

Position 7: Prone1. Ely test2. Hip rotation (internal/external)3. Hip extension limit comparison4. Tibial rotation (internal/external)5. Thigh foot angle .6. Prone leg length, which includes tibia and foot height7. Foot length, width .

flammation around joints, apparent or real joint restrictionof motion, and gait dysfunction or alteration. Patients alsopresent with aesthetic and psychosocial complaints regardinglimb deformities. .

In general, the goals in correcting a deformity are to relievesymptoms if present and to protect adjacent joints from de-velopment of osteoarthrosis secondary to the deformity.Without good data about the natural history of asymptomaticdeformities and their contribution to later joint degeneration,it is difficult to specify exact indications for surgical treatmentof asymptomatic deformities.8•9,13.20,21,24,31,36-38 Isolated ro-tational deformities should not be treated unless symptom-atic. They should be corrected as part of a comprehensiveapproach to the treatment of lower limb alignment.

The following deformities should be considered for treat-ment, even in asymptomatic patients: distal femoral me-chanical valgus greater than 5 0, proximal tibial mechanicalvarus greater than 50, and mechanical axis deviation greaterthan 15 rom. Other asymptomatic deformities should beconsidered for correction prophylactically if radiographicevidence of degenerative joint disease is seen or if only clin-ical signs are detected (eg, positive Trendelenburg sign in adysplastic hip, lateral thrust in a varus knee). Other defor-mities that should be considered for treatment include pro-curvatum deformity of the distal tibia greater than 150

, re-curvarum deformity of the distal tibia greater than 100

, andvarus or valgus deformity of the distal tibia greater than 100

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FIGURE 61-4. A 51-inch cassette is used to assess most adults. Thisprovides a radiograph extending from the ground to the top of thepelvis. Notice that the patella should be centered over the middle ofthe femur to ensure proper alignment (left knee). If the patella pointsinward or outward (right knee) the alignment measurements will bemisleading.

when subtalar joint motion is restricted. Although theseguidelines for deformity correction are based on the availableliterature, each patient must be evaluated individually.

It is important to identify and treat the correct deformityand not create a deformity in an effort to treat a deformity.The best example is distal femoral valgus. Recommendedtreatment for genu valgum has included distal femoral os-teotomy or proximal tibial osteotomy (Fig. 61_9).7.10.34 Anisolated deformity in the femur should never be treated bya corrective osteotomy of a normal tibia. This will lead topersistent joint inclination and eventual subluxation. Cookeand colleagues demonstrated that for combined distal fem-oral and proximal tibial deformities, the best operation is a

DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 887

FIGURE 61-5. When there is subluxation of the knee the radio-graphic changes may be subtle. Subluxation of the knee can be definedon the lateral radiograph as a step in the midpoint of the femoraland tibial condyles. Normally, these two points are opposite eachother (A). When there is a subluxation of the knee the midpoint ofthe tibia will displace anteriorly or posteriorly away from the midpointof the femur with the knee in extension (8).

corrective osteotomy at both levels.4.5 The first step in de-formitv correction, therefore, is to assess the deformity byaccurately defining and describing the deformity (see Tables61-1 and 61-2); then preoperative planning begins.

Preoperative Planning

The apical level of diaphyseal deformities is obvious, whilethe apex of metaphyseal and especially juxta-articular de-formities are subtle or less clear (Fig. 61-10). The first stepis to determine the level of the apex of the angular deformity.With diaphyseal deformities, a line can be drawn down theconcave or convex cortex proximal and distal to the apex.The intersection of these two cortical lines is the true apexof deformity. For juxta-articular and metaphyseal deformitiesa more complex system is necessary to accurately determinethe level of the deformity's apex.

We have developed a "malalignment test" for frontal planemechanical axis deviation (Fig. 61-11). Required materialsare a standing radiograph with the patella pointing forward,knee in extension, from hips to ankles, of both lower limbs,and a pencil,. a long straight edge, and a goniometer orprotractor.

If a mechanical axis deviation is detected in step 0, thensteps 1 to 3 will indicate whether the deviation is in thefemur or tibia, respectively. If lines FC and TP are not par-allel, then there is an intra-articular component to the me-chanical axis deviation.

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DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 889

FIGURE 61-8. (A) The lateral collateral ligament is lax (left). On single-leg stanceauring gait theadductor moment arm leads to a varus deformity through the knee joint. The lateral joint line opensto the point that the lateral collateral ligament becomes tight (center). With descent of the fibularhead the lateral collateral ligament can be tightened to correct the articular varus deformity (right).(B) The medial collateral ligament is lax (left). Associated with a valgus deformity the tibia subluxeslaterally (middle). The medial collateral ligament can be retensioned by distraction of an osteotomylocated proximal to its insertion (right). The distal end of the osteotomy runs distal to the tibialtubercle to avoid pulli[lg the patellar tendon down.

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890 RING FIXATION AND DISTRACTION TECHNIQUES

FIGURE 61-9. A high tibial osteotomy was performed to correct avalgus deformity of the distal femur. In addition to the sloped jointorientation that was present preoperatively the patient is now de-veloping collapse into varus and lateral subluxation. This illustrateswhy a normal tibia should not be osteotomized to correct for a de-formity in the distal femur.

PLANNING THE LEVEL OF OSTEOTOMY ANDHINGE PLACEMENTThe optimal level for an osteotomy is usually at the apex ofan angular deformity. The choice of level is influenced bythe proximity to the adjacent joint, the type of fixation, skincoverage, bone quality, and, in children, thephysis. A de- .formity apex within the bone's metaphysis or diaphysis issuitable for osteotomy and fixation. A juxta-articular defor-mity apex presents difficulties with both the osteotomy andfixation. In children, correcting a juxta-articular deformitywould cause a transphyseal separation, whereas in adultssuch a correction would necessitate a peri-articular or intra-

articular osteotomy. Therefore, the practical level for oste-otomy is usually within the metaphysis in these deformities.For this reason, the metaphyseal and diaphyseal deformitieswill be grouped together under the name metadiaphyseal;the juxta-articular type of deformity will be consideredseparately.

After identifying the deformed and normal bone(s) usingthe above test, ascertain the apex of deformity. The oste-otomy level can then be determined, taking into consider-ation the limitations imposed by the joint and physis andby the fixation method. Preoperative determination of tibialdeformity with a normal femur is shown in Figures 61-12and 61-13.

Preoperative planning for a deformity of the femur witha normal tibia is shown in Figures 61-14 through 61-17.When the apex of the deformity is metadiaphyseal, the os-teotomy is done at the level of the apex, and the hinge isalso placed at the level of the apex. The correction angulatesthe bone ends.

For a juxta-articular deformity apex, the osteotomy is per-formed in the metaphysis at a different level than the apex.The hinge is"placed at the level of the apex. The correctioncauses translation and angulation of the bone ends.

OTHER FACTORS IN DETERMINING THE LEVEL"OF THE OSTEOTOMYSeveral other factors must be considered in determining thelevel of the osteotomy. The apex may not always be theoptimal level or even a possible place to perform the oste-otomy for several reasons. In developmental and congenitaldeformities, the deformity is often at the level of the growthplate or joint and, therefore, is inaccessible for fixation orosteotomy. Angular corrections performed as opening orclosing wedges not at the level of the apex of the deformitycreate secondary translational deformities (Fig. 61-18). Toavoid this, the bone ends should be translated either acutelyor using a translation hinge. The translation needed can beminimized by performing the osteotomy as close as tech-nically feasible to the true apex of deformity. An alternativetechnique uses a hinge at the level of the osteotomy, cor-recting angulation first, followed by translation by modifyingthe frame.

Other situations where the osteotomy is contraindicatedat the apex include soft-tissue coverage problems or thepresence of avascular, sclerotic, or previously infected bone(suboptimal for osteotomy). A translational correction of theosteotomy at a level above or below the apex is required.

If lengthening is a major consideration, the optimal levelfor lengthening is in the proximal or distal metaphysis. Itmay be preferable to perform a metaphyseal-level corticot-omy followed by a translational correction to realign themechanical axis for both angulation and translation or toperform two osteotomies, one for lengthening and one fordeformity correction.

Malunions often present with combinations of angular andtranslational deformities. The translational component mayeither compensate or aggravate the mechanical axis deviationproduced by the angular deformity. In the tibia, if translationis in the direction opposite of the angular deformity, thenthe translation will produce a compensatory effect on" the

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FIGURE 61-10. (A) Subtle deformity: juxta-articularand metaphyseal level deformities are relatively occultradiographically. This is particularly true when an iso-lated radiograph of a single bone is examined ratherthan an alignment x-ray of the entire lower limb. fnthis example the valgus of the distal femur is barelynoticeable, even on the alignment x-ray. For clarifi-cation, cover up the tibia and look at the femur inisolation. The valgus of the distal femur is further hid-den by this maneuver. (B) In contrast, this diaphysealdeformity is obvious. Arms of the deformity extendfrom either end of the apex. In the juxta-artlcular de-formity there is no arm extending away from the de-formity at the articular end.

DEFORMITY CORRECTION BY THE 11iZAROV TECHNIQUE 891

mechanical axis deviation. While this translation may notcompletely realign the mechanical axis, it will reduce theamount of deviation (Fig. 61-19). On the other hand, if thetranslation is in the same direction as the angular deformity,the mechanical axis deviation will be aggravated. The apexof the deformity in these cases is not at the malunited levelof the two bone segments. Because of the translation, thetrue apex of the deformity will be either proximal or distal,depending on whether the translation is aggravating or com-pensatory. In the tibia, compensatory deformities will havean apex distal to the level of the malunion, but aggravatingtranslational angulation deformities will have a true apexproximal to the level of the malunion.

In the femur the opposite relationship exists (Fig. 61-20).By performing the osteotomy at the level of the true apex-the intersection point of the mechanical axis-the limb willrealign both angulation and translation through a single hinge(Fig. 61-21). A translating hinge apex offers the added ad-vantage of allowing an osteotomy through healthy bonerather than through a sclerotic, avascular, previously open,or infected region at the deformity's apex.

Most diaphyseal deformities can be corrected by an os-teotomy at the level of the true apex. An osteotomy at the

. true apex corrects both angulation and translation of themalalignment simultaneously, but does not correct anycontour deformity created by the translated bone ends (Fig.61-22). If the contour deformity is significant, then the os-

teotomy should be done at the level of the malunion. Trans-lation and angulation must be corrected separately.

DETERMINING THE TRUE PLANEOF THE DEFORMITYOrthopaedic surgeons often describe angular deformities asvarus; valgus, procurvatum, and recurvaturn of the distalsegment relative to the proximal segment. The terms varusand valgus describe angular deformities in the frontal plane;procurvatum and recurvatum describe angular deformities inthe sagittal plane. Using this convention, a deformity withvarus and recurvarum is described as a biplanar deformity.Careful analysis of most biplanar deformities reveals thatthey have but a single apex; moreover, the deformity lies inan oblique plane, somewhere between the frontal and sagittalplanes (Fig. 61_23).28,30 We perceive the deformity as bi-planar because the standard radiographic views are obtainedin the anatomic reference planes, which may be differentfrom the plane of angulation. Geometrically speaking, how-ever, two lines can sub tend only one plane. If we considereach bone segment as a line, these two lines can form anangle with each other only in one plane, irrespective of thepresence of angulation, rotation, translation, or length de-formities. A second plane of angulation can exist only if asecond angular deformity at another level is introduced intothese bone segments or lines.

Text continued on page 900

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892 RING FIXATIONAND DISTRACTIONTECHNIQUES

H

(

AA

Step 0H

c

H

(

Step 1 Step 2

H

K

A

Step 0 Step 1

(

Step 3

A

Step 2 Step 3

H H

Step 0 Step 1

c

Step 2 Step 3

FIGURE 61-11. The malalignment test. This test determinesthe origin of frontal plane malalignment. Step 0, Draw HA, themechanical axis line of the lower limb, from the center of thefemoral head to the center of the ankle plafond. If this linepasses medial to the medial tibial spine there is medial me-chanical axis deviation (MAD). If it passes lateral to the centerof the knee there is lateral MAD.Step 1: Draw HK,the mechanicalaxis of the femur, from the center of the femoral head to thecenter of the knee. Draw FC, the femoral condyle line. Measurethe lateral angle HKF.This should be SJO ± 2°. Outside theselimits the femur is contributing to the MAD. Step 2: Draw KA,the tibial mechanical axis line, from the center of the knee tothe center of the ankle. Draw the tibial plateau line TP. Measurethe medial angle AKP. This should be SJO ± 2°. Outside theselimits the tibia is contributing to the MAD.Step 3: Compare theorientation of Fe to TP. These should be parallel to each other.If they diverge more than 1o to 2°, there is joint laxity contrib-uting to MAD. (A) Femoral malalignment. (B)Tibial malalignment.(C) Joint laxity mal alignment. -

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DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 893

26"

A Step 0 Step 1 Step 2A

FIGURE 61-12. The apparatus for correction of thisangular deformity is preconstructed with two levelsof fixation on either side of the hinge. The hinge level,plane, magnitude, and direction are built into the ap-paratus. Tibial diaphyseal deformity with a normal fe-mur. Step 0: Draw the mechanical axis line to dem-onstrate the degree of mechanical axis deviationcreated by the obvious tibial diaphyseal deformity.The mal alignment test was performed to confirm thatthe orientation of the distal femur is normal. Step 1:Since the femur is normal, draw the line from the cen-ter of the hip through the center of the knee and ex-tend it distally. This is the mechanical axis of the prox-imal tibia. Step 2: Draw a line from the center of theplafond extending proximally in line with the anatomicaxis of the tibia. This is the' mechanical axis of thedistal tibia. The center of rotation of angulation is atthe intersection of the two mechanical axis lines. Theangular deformity measures 26°. Step 2b: The alter-native method is to draw a line down the convex cor-tices of the deformity. These lines intersect at thesame level and also demonstrate a 26° deformity. Step3a: The deformity correction is performed on paper

,at the level of the apex of the deformity for a totalof 26°. This realigns and overlaps the mechanical axislines to reestablish the colinearity of the hip-knee-ankle axis. Step 3b: After opening wedge correction.This osteotomy also realigns the diaphyseal line of theconvex cortex so that it is colin ear.

Step 3A Step 26 Step 36

\,

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894 RING FIXATION AND DISTRACTIONTECHNIQUES

Step 0 Step 1 Step 2

A Step 3A Step 38 Step 3C Step 3D

FIGURE61-13. (A) Juxta-articular tibial deformity with a normalfemur. Step 0: Draw the mechanical axis line from the center ofthe femoral head to the center of the ankle. The malalignment testwas performed to confirm that the varus mechanical axis deviationis que only to the tibia and that the femur is normal. Step 1: Drawthe mechanical axis line of the femur and extend it distally. This isthe mechanical axis of the proximal tibia. Step 2: Draw the linefrom the center of the ankle plafond extending proximally parallelto the anatomic axis of the tibia. This is the mechanical axis of thedistal tibia. Note the level of intersection of the two mechanicalaxis lines is at the level of the growth plate. The angular deformitymeasures 37°. Step 3a: The deformity may be corrected by a 37°opening wedge through the grow!h plate, thus realigning the me-chanical axis and reestablishing normal joint orientation. Step 3b:Correction of the deformity at the level of the tibial metaphysisrequires a50° correction to realign the mechanical axis. This createsa malorientation of the knee and ankle. Notice that the mechanicalaxis now subtends a 96° orientation to the ankle joint instead ofthe normal 90°. Step 3c: If only 37° of deformity are corrected,then there is persistent varus mechanical axis deviation. The kneeand ankle are oriented correctly one to the other but the mechanicalaxis is deviated due to a persistent translational deformity (T).Step3d: To realign the mechanical axis at the level of the metaphysiswhich is distal to the apex of the deformity, the correction shouldinclude both 37" of angular correction and lateral translation in theamount of T. The magnitude of T increases as the level of osteotomymoves farther away from the apex of the deformity. (8) If the hingeis placed at the level of the osteotomy, overcorrection is requiredto eliminate mechanical axis deviation. Note that the rings are notparallel at the end of correction because of overcorrection. (C)Theapparatus is preconstructed with the hinge at the level of the centerof rotation of angulation. This leads to angulation and translation.The rings are parallel at the end of correction.

FIGURE 61-14. (A) Diaphyseal femoral deformity with a normal tibia. Step 0: Draw the line from JIthe center of the femoral head to the center of the ankle, demonstrating a valgus mechanical axisdisplacement. The malalignment test confirms a normal tibial alignment. Step 1: Draw the mechanicalaxis line of the tibia from the center of the ankle to the center of the knee and extend it proximally.This is the mechanical axis of the distal femur. Step 2a: Draw the mechanical axis line of the femuron the opposite normal side. Draw the anatomic axis line of the normal side down the midshaft ofthe proximal femur. Measure the angle between the mechanical and anatomic axes (a). Draw theanatomic axis of the proximal femor on the deformed side. Draw a line from the center of the hipparallel to the anatomic axis. Step 2b: Draw a line from the center of the hip extending distally ata degrees to the last line. This is the mechanical axis of the proximal femur. This line intersects thedistal mechanical axis line at the apex of the deformity, demonstrating a 15° angular deformation.Step 3: Correct the angular deformity through an osteotomy at the level of the apex of the deformity.The angular correction required to realign the mechanical axis is 15°. (8) Apparatus before and afteropen wedge correction with hinge-at osteotomy level. .

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B

Step 0

A

Step 1

Step 2b

FIGURE 61-13. (Continued)

Step 2a

Step 3a B

FIGURE 61-14.

895

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896 RING FIXATION AND DISTRACTIONTECHNIQUES

Step 0

A Step 2b

Step 1

7

Step 3

Step 2a

Step 3a Step 3b B

FIGURE61-15. (A) Juxta-articular femoral deformity with a normal tibia. Step 0: Draw the mechanicalaxis line from the center of the hip to the center of the ankle. This line passes lateral to the centerof the knee, indicating a valgus mechanical axis deviation. The malalignment test confirms that thetibial alignment is normal. Step 1: Draw the mechanical axis line from the center of the ankle throughthe center of the knee and extend it proximally. This is the mechanical axis of the distal femur. Step2a: Draw the mechanical axis line of the femur on the opposite normal side. Draw the anatomic axisline of the normal side down the midshaft of the proximal femur. Measure the angle between themechanical and anatomic axes (a). Draw the anatomic axis of the proximal femur on the deformedside. Draw a line from the center of the hip parallel to the anatomic axis. Step 2b: Draw a line fromthe center of the hip extending distally at a degrees to the last line. This is the mechanical axis ofthe proximal femur. This line intersects the distal mechanical axis line at the knee joint, indicatinga juxta-articular deformity measuring 110

• Step 3a: Since it is not possible to do an osteotomy sodistal, the osteotomy is performed at the level of the distal metaphysis. Correction of the mechanicalaxis alignment by a pure angular correction at this level requires 140 since the. osteotomy is not atthe level of the apex of the deformity. As in the tibial example, this produces a slight malorientationof the hip to knee joint lines. Step 3b: The correction of only 110 results in persistent valgus mechanicalaxis deviation. The deformity that remains is purely a translational one of amount T. Step 3c: Themost accurate correction through a metaphyseal osteotomy is to combine 110 of angulation withlateral translation of amount T. T increases as the distance of the ostoetomy to the true apex of thedeformity increases. (B) Apparatus with hinge at juxta-articular center of rotation. Angulation andtranslation correction occur since the hinge is at a different level fr.om the osteotomy.

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FIGURE61-16. Anatomic axis methodof preoperative planning. for femur.Step 0: There is a MADdue to a femoraldeformity. Since there is a cup arthro-plasty, the center of the femoral head,which is essential for mechanical axisplanning, cannot be used. Therefore,anatomic planning is used. Step 1:Draw the anatomic axis line on thenormal side down the midfemur andmeasure the lateral angle it subtendsto the knee (830

). Step 2: Draw an 830

line from the center of the knee on thedeformed side. This is the anatomicaxis of the distal femur. Step 3: Drawthe anatomic axis line of the proximalfemur on the deformed side (midlineproximal femur shaft). The intersectionpoint of the two anatomic axis linesis the center of rotation of theangulation. Step 0

FIGURE 61-17. Combined femoral and tibial defor-mities in the absence of a normal opposite side. Step0: Draw the mechanical axis line from the center of thehip to the center of the ankle. This line passes medialto the center of the knee, indicating a varus malalign-ment. Step 0,: the mal alignment test demonstrates adeformity in both tibia and femur. Step 1: Draw a line87° to the knee orientation line. Extend this line bothproximally and distally. Step 2: Draw a line perpendicularto the ankle plafond (or distal tibial shaft) and extendthis line proximally. Step 3: Correct the tibial deformityat the level of the apex of the deformity, realigning thetibial mechanical axis and reorienting the ankle andknee. Extend the normalized tibial mechanical axisproximally. Step 4: Draw the mechanical axis of theproximal femur. If there is a normal opposite femur tocompare to, use the angle measured from the oppositeside. If there is not a normal angle, use 900

• The inter-section point indicates the apex of the deformity. StepSa: Draw the osteotomy at the level of the apex of thedeformity, realigning the femoral mechanical axis withthat of the tibia. Since this deformity is a bowing of thefemur and not truly a uniapical angular deformity, thecorrection produces a sharp angulation in the cortex ofthe femur which may be associated with a cosmeticdeformity. Step Sb: The osteotomy may be performedat a lower level combined with translation in order tominimize the angulation in the shaft of the femur. Thisproduces a better aesthetic appearance. The center ofrotation of the second osteotomy (b) is still at level a.

Step 0

.'•

•I••

Step 1

Step 1

Step 4 StepS

IIII

Step 2

Step 2

Step SA

•III

Step 3

Step 3

90·

Step 58897

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898 RING FIXATiON AND DISTRACTION TECHNIQUES

FIGURE 61-18. Secondary translational deformities. (A) The so-called golf club deformity of thedistal femur is a result of repeated closing wedge varus osteotomies in the supracondylar metaphysealregion of the femur for the treatment of a juxta-articular deformity of the distal femur. This producesa progressive medial translational deformity with each successive osteotomy. (B) Medial translationaldeformities of the tibia are the result of repeated valgus osteotomies at the metaphyseal diaphysealjunction for the treatment of these juxta-articular deformities of the tibia. In the right tibia, over-correction was carried out to realign the mechanical axis similar to that described in Figure 61·13,step 3b. On the left the ankle and knee joints were reoriented but the mechanical axis was not fullycorrected, leading to a persistent varus from the translational component of the deformity. (C) Avarus deformity of the distal tibia due to a malunion was treated by a supramalleolar osteotomy inorder to realign the ankle to the knee joint. This correction ignores the mechanical axis deviationcreated by the malunion. It demonstrates again that angular correction not at the level of the apexof an angular deformity leads to a translational deformity.

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DEFOHMITY CORRECTION BY THE ILiZAROV TECHNIQUE 899

COMPENSATORY NO AGGRAVATINGTRANSLATION TRANSLATION TRANSLATION

FIGURE 61-19. Angular malunions of the tibia lead to varying degrees of mechanical axis deviation,depending on the degree of angulation, the level of the malunion, and the magnitude and directionof any associated translational deformity. These three varus malunions differ only in the magnitudeand direction of the translational component of the malunion. The center malunion has pure angulationwithout translation of the bone ends. The malunion to the left of center has the same degree ofangulation combined with translation towards the convexity of the deformity. The malunion to theright of center has the same degree of angulation combined with translation towards the concavityof the deformity. Notice the amount of mechanical axis deviation in all three examples. The mechanicalaxis deviation is decreased when the translation is towards the convexity and increased when it istowards the concavity. The former is called compensatory translation, whereas the latter is calledaggravating translation. Notice the point of intersection of the mechanical axis lines of the proximaland distal tibia. When there is no translation, the intersection is at the level of the malunion. Whenthere is a compensatory translation the intersection point is distal to the malunion. When there isaggravating translation the intersection point is proximal to the malunion. The intersection point isconsidered to be the true apex of the angulation/translation deformity, while the malunion is con.sidered to be the apparent apex.

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900 RING FIXATION AND DISTRACTIONTECHNIQUES

FIGURE61-20. Varus malunions of the femur areillustrated with and without aggravating or com-pensatory translation. Notice that in the femurtranslation towards the convexity is aggravatingwhile translation towards the concavity is com-pensatory. The reason for this is that by conventionwe refer to translation as the distal fragment rel-ative to the proximal. If we think of the-proximalfragment of the femur as the one that is translating,then the rules are similar to that described in thetibia (see Fig. 61-19). Notice that the translationaldeformity shifts the true apex of the deformity ei-ther proximal or distal to the apparent apex at thelevel of the malunion.

COMPENSATORYTRANSLATION

There are several ways to determine the magnitude andtrue plane of a deformity in a plane oblique to the frontalplane. The simplest method is to rotate the limb until itappears straight (Fig. 61_24).28 The true plane of deformityis the plane where the projection of a deformed limb appearsstraight. The plane 900 to this projection should demonstratethe maximum angulation profile of the deformity. Radio-graphs taken in these two planes can be used to determinethe orientation of this plane and the magnitude of the truedeformity.

The orientation of the oblique plane angular deformitycan be calculated using trigonometric equations or a no-mograni." The graphic method requires only a pencil and

NOTRANSLATION

AGGRAVATINGTRANSLATION

goniometer to calculate the magnitude and direction of theoblique plane deformity (Fig. 61-25). Bar and Breitfuss havepublished a nomogram to determine the true angular defor-mity and its oblique plane. 1 llizarov plots the apical deviationfrom the axial midline on the anteroposterior and lateralviews as x and y coordinates and determines the plane ofdeformity graphically (Fig. 61-26). The Ilizarov apparatusallows the surgeon to make use 'of these calculations. Bydetermining the true plane of deformity the surgeon can alsodetermine the axis of the deformity's apex. The axis of thedeformity is always perpendicular to the plane of the defor-mity (Fig. 61-27). By applying a hinge at the true apex ofan oblique plane deformity perpendicular to the true plane

FIGURE 61-21. (A) Varus malunion of the middiaphysis of the tibia with compensatory lateraltranslation. (B)The frame was applied with the hinges at the level of the true apex of the deformity,and the corticotomy was carried out at that level. (C) Distraction of the concavity led to realignmentof the tibia through an open wedge correction. Notice the simultaneous correction of the angulationand translation, as demonstrated by the co linearity of the medial tibial diaphysis. The hinges arenow straight and the rings are parallel, indicating completion of the deformity correction. (D) Aftercompletion of the angular correction, the parallel rings were distracted to lengthen the tibia. (E)Final AP standing radiograph demonstrates the alignment of the correctedrnalunion. There is apersistent leg length discrepancy of 2 em, which was accepted due to slow healing in this patient.

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DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 901

FIGURE 61-21.

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902 RING FIXATION AND DISTRACTION TECHNIQUES

FIGURE 61-21. (Continued)

of this deformity, the surgeon can simultaneously correctthe anteroposterior and lateral projections of this deformity(Fig. 61-28). Alternatively, the apparatus could be appliedto correct the deformity in the anteroposterior plane; after-ward, the hinges would be reoriented to correct the deformityin the lateral plane. This is more time-consuming and lessefficient method, but it is accurate.

TRANSLATION DEFORMITIES

A translation deformity may also appear in both perpendic-ular planes (Fig. 61-29). The direction of the true transla-tional deformity can be calculated using the methods de-scribed above (see Fig. 61-29). Since translation is a directlinear measurement and not an angular deviation, the Py-thagorean or graphic methods described above are both ac-curate for the asse::.sment of translation deformities in planesoblique to the frontal projection. Both the magnitude andthe true plane of translation can be determined. .

ANGULATION/TRANSLATION DEFORMITIES

When angulation and translation occur together, the planeof angulation may be the same or different than the plane

of translation. If angulation and translation are in the sameplane, they can be characterized as a single apex of angulation(Fig. 61-31). If this is in one of the anatomic planes (frontalor sagittal), one view will show angulation and translationwhile the other shows no deformity. If both are in the sameoblique plane, the center of rotation will be at the same levelon both AP and lateral radiographs. If angulation and trans-lation are in different planes 90° apart, there will be oneplane with only angulation and one with only translation(Fig. 61-32). This is readily appreciated when the defor-mations correspond to the anatomic planes; translation onlyis seen on one view and angulation only on the other view.If they are in different oblique planes, then both angulationand translation are present in both AP and lateral views. Todifferentiate this from angulationltranslation in the sameoblique plane, one must examine the levels of the center ofrotation of the angulation on AP and lateral views. Whenboth are in different planes, then the center of rotation is ata different level on AP than on lateral views, usually oneapex above and cine below the fracture level. Angulation andtranslation may also be in different planes that are less than90° apart (Fig. 61-32). The graphic method of oblique planedeformity assessment can be used to plot the plane of an-gulation and the plane of translation on the same graph (Fig.61-24). The difference in planes between angulation andtranslation can then be measured off the graph.

The relationship between the plane of angulation andtranslation has ramifications on treatment. When both arein the same plane, there is a single center of rotation pointthat will correct both deformities by angulation alone. Innonunions the hinge can be placed at this angulation/trans-lation point, and after distracting the ends apart the angu-lation and translation are corrected by angulation aroundthis hinge. If there is a malunion, an osteotomy may beperformed at this level with opening or closing wedge cor-rection. This corrects both angulation and translation to-gether (see Fig. 61-21),

If angulation and translation are in different planes, thenseveral strategies may be pursued. Angulation may be cor-rected at the apical level on the AP, lateral, or oblique views(Fig. 61-24). Translation, if significant, will not correct withthe angulation and requires a separate correction in the lat-eral, AP, or oblique planes, respectively (see Fig. 61-24).Alternatively, a double level osteotomy can be performed,correcting angulation and translation in the frontal planewith one osteotomy at the AP angulation translation pointand one osteotomy at the LAT angulation translation point.This deformity is the only true "biplanar" deformity from asingle fracture level.

Malrotation may also be a component of the deformity.Rotation is simply an angular deformity in the axial plane.Since all single-level angular deformities can be resolvedinto a single plane and a single axis of deformity, it shouldbe possible to resolve the rotational component togetherwith the angulation and translation. Sangeorzan and asso-ciates and other authors have demonstrated that combina-tions of angulation and rotation deformities can be resolvedinto a single axis of deformity using complex trigonometriccomputations and tables."

This geometric problem can also be solved in a simplerfashion. This x-y-z axis deformity can be computed as a

Text continued on page 909

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DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 903

FIGURE 61-22. (A) Valgus malunion of the middiaphysis of the tibiawith aggravating lateral translation. There was a significant contour de-formity created by the malunion. Preoperative planning demonstrates thatthe true apex of the deformity is proximal to the level of the malunion.Angular correction at this level simultaneous corrects for the translationalcomponent of the deformity. (8) This leaves a persistent contour deformitywhich was unacceptable to the patient. (C) Therefore, the alternative isto perform the correction at the level of the malunion to correct separatelythe angulation, translation, and the contour deformities. The radiographdemonstrates the angular and translational correction which were per-formed acutely followed by distraction to lengthen the tibia. (D) The finalradiograph demonstrates elimination of the angulation-translation and,as a result, of the contour deformity. The acute translational maneuvershould be avoided because it contributes to delayed consolidation by dis-rupting the periosteum. It is preferable to correct the angulation gradually,followed by distraction to lengthen the tibia, followed by gradualtranslation.

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904

I

III

~---

Y·I.../

./

/1. /1I

I

I..•.•

".J

AP

8 AP LAT

LAT

A OBL

FIGURE61-23. (A) Oblique plane deformity of the tibia.(B) The AP projection of this tibia demonstrates a valgusdeformity. (C) The lateral projection of this tibia dem-onstrates a recurvatum deformity. The trigonometric ex-act formulae and graphic approximate formulae to cal-culate the magnitude (obi) and orientation of the obliqueplane to the frontal plane (pin) are as follow:

trigonometric: obi = tan' Vtan2 ap + tan- lat

, tan latpin = tan- --

tan ap

graphic: obi = var+tl:f- (phythagorean Theorem)

latpin = tan " - .ap .

1I

l

C AP LAT

FIGURE61-24. (A) Malunion of the tibia with 200 of varus and 13 mm lateral translation. (B) The IIIlateral projection demonstrates 250 of procurvatum and 10 mm posterior translation. (C) Observationof the patient from the front demonstrates the varus deformity of the tibia. (0) When the patientturns his foot inwards, the varus deformity seems to disappear and the tibia appears straight. (E)Examination from the side demonstrates the procurvatum deformity of the tibia. (F) When the patientturns his foot inward again, the maximum angular profile of the deformity is seen. (G) The maximumangular profile is captured radiographically on this lateral oblique view of the tibia. It measures 32

c•

(H) An internal rotation AP oblique radiograph. In the plane of the deformity the tibia appearsstraight. The translational component of the deformity can be appreciated on this view. (I) Themeasurement of 20c varus and 25c procurvatum were plotted on a graph. The vector obtained bythe point 20-25 represents the magnitude 32c and true orientation 51.50

, to frontal plane of theoblique plane angular deformity. Superimposed on this graph the magnitude of translation on theAP and LATare plotted. The magnitude of the oblique plane translation is 16 mm oriented 35

cto

the frontal plane. The translation and angulation planes are 88c apart. This confirms the radiographicfindings. (1)The malunion was split obliquely. (K)Notice the appearance of the apparatus in relationshipto the left. The hinges have been placed relative to the apex of the oblique plane deformity. Noticethat the distance of the hinge rods to the central bolts differs for the medial and the lateral hinge,demonstrating that the hinges are oriented obliquely to the anatomic planes. (L)A true lateral viewof the deformity aligns the hinges with the apex in the oblique plane. (M) In this manner distradion

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FIGURE 61-24. (Continued) of the concavity leads to realignment of the diaphysis on the lateralview of the tibia simultaneous with realignment on the AP view. (N) All that remains is to correctthe translational deformity. (0) By applying translational rods, the tibia was narrowed, bringing thecortical ends together side to side. (P) Appearance of the callus at the time of the removal of theapparatus 23 weeks after application. Notice that there is no corticalization of the callus betweenthe bone ends. The patient was, therefore, protected in a PTBcast. The final AP (Q) and lateral (R)radiographs demonstrate the recurrence of deformity that occurred due to premature removal ofthe apparatus prior to complete corticalization of the distraction callus. Notice in addition the ringsequestrum from one of the pin sites (arrow). (see following pages)

905

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906 RING FIXATION AND DISTRACTION TECHNIQUES

A50

.!f Angulation Plane

..............40

30

M L____a; 20 ) 30

•••/360..~Translation Plane

PFIGURE 61-24. (Continued)

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DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 907

FIGURE 61-24. (Continued)

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908 RING FIXATION AND DISTRACTION TECHNIQUES

FIGURE 61-24. (Continued)

Page 25: DEFORMITY' CORRECTION BY THE ILIZAROV TECHNIQUE

Apical Direction Graphs

Ant (Procurvaturn) Ant

DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 909

A

Mea '-"'1,:Lat +-+--+--II--+-f+--t---'I--+-:: Med • -+--+--t--1'-\-4-.-II-+--+--+- 1M

(Varus) (Valgus)

B'~ ~~ p

FIGURE 61-25. (A) Mark direction of apex of angulation on axes of the graph (as if looking down at one's own feet). (8) Mark magnitudeof AP and LAT angles (1 mm = 1°; AP, x axis, LAT, y axis). The resultant vector represents plane, magnitude, and apical direction.

Post (Recurvatum)

A

AP

LATb

__ ~ __ .J,....;..-AP

Post

LAT

FIGURE 61-26. IIizarov's method for determination of the plane ofthe oblique deformity. A line is drawn from the center of the knee'to the center of the ankle on both the AP and lateral views. Thedistance from this line to the apex of the deformity is measured onboth views. These are plotted on a graph, and the orientation of theresultant vector from the AP or lateral plane is measured. This rep-resents the plane of the apex of the deformity.

simple extension of the method detailed above (see Fig. 61-33). This method is a reasonable approximation for defor-mities of up to 45° in the anteroposterior, lateral, or axialdirections. Since most angular deformities are much less than'45°, the computation described above is a useful methodand does not require trigonometry or complex nomograms.

Combinations of angulation and rotation can be correctedeither through a single hinge or sequentially. The correctionrequires a hinge that is oriented not in the transverse planebut inclined, in a vertical plane. This vertical inclined hingewill simultaneously correct the angular and rotational de-formities (Fig. 61-34). If the osteotomy is done at the an-gulation/translation point, angulation, translation, and ro-tation are corrected simultaneously. The alternative, whichis simpler, is to correct the angular deformity first, then tocorrect the rotational deformity using a derotation mecha-nism. While this method is more time-consuming, it is easierfor most surgeons to understand. However, some transla-tional correction may be needed after derotation because ofthe eccentric location of the bones within the ring. The ad-vantage of the single-hinge method is that no maltranslationresults from the deformity correction.

Conventional osteotomies also make use of these princi-ples. By producing a single osteotomy in a vertical obliqueplane, a surgeon can correct all of these deformities by slidingthe bone surfaces perpendicular to the plane of theosteotomy.32,33

MUL TI·APICAL ANGULAR DEFORMITIES

A more complex situation exists when there is more thanone level of angulation. Each level and each plane of defor-mity must be delineated for each apex. Sometimes a singleosteotomy can be used to correct a multi-apical angular de-formity, but usually more than one osteotomy is needed.Often one of the apices is obvious, while the other is subtle.This happens when one of the deformities is diaphyseal and

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910 RING FIXATION AND DISTRACTIONTECHNIQUES

A A

i~-dr!rrieiejr-!

Covex cortex 1(apax)~1

Step 1p

A

p

Step 2P

FIGURE 61-27. Graphic preoperative planning of hinge placementin oblique plane deformities. Step 1: Measure the diameter of thetibia on the AP and LATviews and mark on the graph as shown. Thelateral aspect of the tibia should be marked on the upper side of they axis and the width on the AP should be marked to the minus orplus side on the x axis for right and left legs respectively. Thesemarkings should be to normal scale with 1 mm on the radiographequal to 1 mm on the graph. The points on the x and y axes areconnected with a line to form a triangle. This represents the crosssection of the tibia at the level of the apex of angulation. If a differentlevel or bone is chosen, the representative x section for that apicallevel should similarly be centered. Step 2: The hinge axis is alwaysperpendicular to the plane of angulation. If an opening wedge hingeplacement is chosen, it should be placed at the convex edge of thebone. The direction of the convexity is shown by the arrow. Thehinge axis is therefore drawn perpendicular to the plane of angulationaxis passing tangential to the convex cortex of the bone. Step 3: Inorder to determine the hinge holes a ring of the appropriate size forthe limb should be placed on the graph. To center the ring the ref·erence marks of the ring must be defined. The line connecting thecentral bolts represents the AP axis of the frame. Since the rings arenormally centered over the lateral edge of the central bolts of thering should be placed on the y axis. The ring is normally spaced 2fingerbreadths from the anterior skin of the leg. This can be markedon the graph by noting the thickness of the anterior skin followedby a 2·fingerbreadth space anterior to that. The position of the ringon the y axis fixes it in place. The hinges are placed in the holeswhere the hinge line intersects the ring. The distraction rod on theconcavity is places where the plane axis line intersects the ring onthe concave side of the angulation.

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~~6 3nOlNHJ31 J\OH\tZ1l1 3Hl A8 NOllJ3'tlHOJ AlIIAIHO:l3G

38os

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l/\oi 02 080vOS

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912 RING FIXATION AND DISTRACTIONTECHNIQUES

FIGURE 61-28. (A)Valgus malunion of the tibia with aggravating lateral translation. (B)The deformitymeasures 22° of valgus with an apex proximal to the level of the malunion. (C) On the lateral viewthere is an 11° deformity, indicating that this is an oblique planar deformity with angulation andtranslation. (0) The maximum profile of deformity is demonstrated on this oblique lateral radiographand measures 24°. (E) The radiograph in the plane of the deformity illustrates the translationalcomponent in the absence of angulation. (F) Graphic determination of the magnitude and plane ofthe oblique deformity on a left leg graph demonstrates a 24.5° deformity oriented 26.7° from thefrontal plane. This is the same example shown in Figs. 61 -23, 61-24, and 61 -27. (G) The apparatusis applied so that the hinges are at the level of the true apex of the deformity which is proximal tothe malunion. The corticotomy is performed at the same level. (H) An open wedge correction wascarried out, realigning the mechanical axis of the lower limb. Note that all of the rings are paralleland the hinges are straight. (I) On the lateral view one can also appreciate the open wedge anteriorlywith the correction of the recurvatum deformity. The rings are parallel on the lateral at the end ofthe correction. The follow-up AP (J) and lateral (K) radiographs demonstrate the restoration of APand lateral alignment of the tibia.

the other is juxta-articular. Examples are anteromedial andposterolateral bows ofthe tibia (Fig. 61-35). Usually a varusor valgus diaphyseal deformity exists with a compensatoryjuxta-articular angular deformity at the level of the proximaltibial physis. Correction requires two osteotomies: angula-tion-translation in the proximal tibia and angulation in themid-diaphyseal region. These are called compensatory bow-ing deformities because one deformity compensates for theother. There is usually little deviation of the mechanical axis.

True (noncompensatory) bowing is a continuous, multi-apical deformity that develops in soft bone such as in rickets,Paget's, and osteogenesis imperfecta (Fig. 61-36 through 61-38). Whether due to remodeling or ongoing multiple stressfractures, these deformities demonstrate no single or doubleapex. While a bow can be considered as having a singleapex, realignment through the apex corrects only the me-chanical axis and does not improve the anatomical axis ofthe bone. It is preferable to perform at least two osteotomies

to straighten a bowed bone. An alternative is to perform anosteotomy at a different level than the apex of the bow andcombine this with a translational correction so as to eliminatesome of the anatomical axis deformity.

The steps for preoperative planning of multi-apical angulardeformities of the femur and/or tibia are shown in Figure61-39. The clue that there is more than one apex of angu-lation is that the single center of rotation determined by theintersection of the proximal and distal mechanical axis linesis at a level where there is no "obvious" angulation (see Fig.61-39, step 1). In multiapical deformities there is usuallyone obvious (diaphyseal, hip, or ankle) apex and one lessobvious angulation apex. The obvious apex should be cor-rected first. The apex of this level may be chosen based oncortical or midbone lines, or, in the case of hip or ankledeformities, we know the apex is at the center of the joint.Once the first apex of angulation is corrected it will pointto the second apex.

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MI---+-+----+-~-+--+---,--+-----l

FIGURE 61-29. (A, B) Translational deformity may also be seen in two planes. This tibial nonunionhas a posterior and lateral translational deformity. (C) The posterior translation measures 2 em, whilethe lateral translation measures 2.7 em. When these are plotted on a graph, it demonstrates thatthe true translation is 33 mm in a plane oriented 36° to the frontal plane. This graph is drawn as for

a right leg.

c

JOINT LAXITY DEFORMITIES OF THE KNEE

If lateral laxity of the knee is a cause of symptoms or mal-alignment, it should be corrected together with the tibial orfemoral varus angulation. With conventional techniques, thehead of the fibula can be osteotomized and moved distally.By the Ilizarov method, the proximal fibula is pulled downto tighten (even over-tighten) the lateral complex (see Figs.61-8 and 61-36). The medial collateral ligament can also betightened by distracting the tibia through an osteotomyproximal to the insertion of the medial collateral ligament.In order to tighten the medial collateral ligament withoutpulling down the patellar tendon, the osteotomy of the tibiashould be directed obliquely distally and laterally to exitbelow the tibial tuberosity (Fig. 61-8).

INDICATIONS FOR DISTRACTION OSTEOTOMYVERSUS CONVENTIONAL OSTEOTOMY

An angular deformity of a bone may be corrected by openingwedge, dome, closing wedge, or angular displacement os-teotomies. Both distraction and conventional methods useali of these osteotomy types. With conventional osteotomy,the correction is achieved acutely in the operating room;stability is achieved with internal or external fixation. Theclosing wedge technique is preferred because of the good

DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 913

A

10 20 30 40L

10 \)360

20 "30 '""40

P

bone-to-bone contact possible. Conventional opening wedgemethods are plagued with union problems and often requirea bone graft. The dome osteotomy is a compromise betweenthe opening and closing wedge, avoiding the length loss ofthe closing wedge method and offering some adjustability.The complications with these techniques include nonunion,osteomyelitis, compartment syndrome, nerve injury, andvascular injury." Accuracy of correction is often a problem,especially with the closing wedge technique. Even with me-ticulous planning, factors such as x-ray magnification, rotatedx-rays, measurement error, the thickness of the saw blade,and the expertise of the surgeon all contribute to inaccuracywith conventional methods." After the operation there isno nonoperative way to adjust incomplete correction;n,22

Distraction osteotomies are less nsky and more accurate.Since Ilizarov's technique is percutaneous, there is little riskof compartment syndrome, nerve injury, vessel injury, non-union, or osteomyelitis. The correction is performed eitheracutely for small deformities or gradually for larger defer- .mities." Gradual distraction prevents nerve stretch injuries,as can occur in the correction of a valgus tibial deformity.The distraction method is as accurate as one can measureon a radiograph, perhaps the greatest advantage'ofIlizarov'ste\:hnique. Even after acute corrections, adjustments can bemade to fine-tune the correction until the exact alignmentof the limb is achieved.

Text continued on page 923

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914 RING FIXATION AND DISTRACTION TECHNIQUES

. FIGURE 61·30. (A) Frontal plane translation.Translation is seen on the AP only. There is no de-formity on the-lateral. (B) Oblique plane translation.Translation is seen on both AP and LAT. The axialview (floor) shows the orientation of the obliqueplane of translation. The magnitude of the obliqueplane translation is larger than that seen on eitherAP or LAT view.

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FIGURE 61-31. Angulation-translation deformity inthe same plane. (A) Frontal plane angulation andtranslation. Angulation and translation are both inthe frontal plane. No deformity is seen in the sagittalplane. Note that the center of rotation of the an-gulation is proximal to the fracture level. (B)Obliqueplane angulation and translation: same plane. An-gulation and translation are seen on both AP andLATviews. The center of rotation of the angulationis the same on both views. This indicates that bothangulation and translation are in the same obliqueplane (see axial). The apical direction of angulationis marked with an arrow A and the direction oftranslation marked T. This represents the same de-formity shown in part A rotated into an obliqueplane.

DEFORMITYCORRECTIONBY THE ILlZAROVTECHNIQUE 915

A@Maryland Canter for Umb LengthBnins & Raconstruclian

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916

FIGURE 61 -32. Angulation-translation deformity indifferent planes. (A) Frontal plane angulation withsagittal plane translation. The AP shows angulationwithout translation while the LATshows translationwithout angulation. The axiai view shows the directionof the apex of angulation A relative to translation T.In this example they are 90° apart. (B) Oblique planeangulation-translation: different planes 90° apart. An-gulation and translation are seen on both AP and LATviews. Note that the center of rotation is at a differentlevel on the AP than on the LAT.On the AP it is prox-imal to the osteotomy while on the LAT it is distal.This is the tipoff that the two are in different planes.On the axial view the direction of angulation A andof translation Tare 90° apart. This represents the samedeformityshown in A rotated into an' oblique plane.(C) Oblique plane anqulatlon-translatlon: differentplanes less than 90° apart. The AP and LATprojectionsare as before with angulation and translation seen onboth views. The difference is that the plane of angu-lation A and translation T are different but less than90° apart. This is one of the most common clinicalsituations.

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FIGURE 61-33. If one adds rotation to the evaluation of angulardeformity, then an XYZ graph can be used to determine the orien-tation of the axis and magnitude of the deformity. The oblique planedeformity is calculated first in the method described above. One theriplots theoblique plane magnitude on the X axis and the rotationalmagnitude on the Z or axial axis. In the example illustrated there isa 25° varus angulation and 25° procurvatum angulation, producinga 35° oblique plane deformity oriented 45° to the frontal plane. Inaddition, there is a 34° rotational deformity. This is plotted on theaxial axis. The graph demonstrates a 39° angular deformity orientedat a 44.5° inclination to the transverse plane. This axis can be furtherqualified as oriented at 45° to the frontal plane on the transversecut.

20

AXIAL40

A30

10

f---t---t---l---I'E---+--+--t--4>----1 OBLlQU E20 3004010

FIGURE 61-34. (A) Vertical inclined plane hinge. When the paper is folded with the tibia marked, on it along a vertical oblique axis, the tibial diaphysis is both realigned as to its angular deformation

and de rotated. (8) This principle can be applied to the lIizarov apparatus. By using universal hinges,two rings can be connected by hinges at different levels. The axis of rotation is no longer parallelto the plane of the rings, but rather is in a plane which is vertically oblique to the rings. (C) In thissimulation the upper ring can be seen to pivot through the vertical oblique axis. Notice the positionof the central bolt connecting the half rings on the moving ring relative to the central bolt on thestationary ring. In this reduced position the central bolts are properly aligned. In the flexed positionthe central bolts are rotated with respect to each other.

917

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918 RING FIXATION AND DISTRACTION TECHNIQUES

FIGURE 61-35.

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FIGURE 61-35. Anteromedial tibial bow. (A) The frontal plane alignment of the tibia demonstratesan obvious varus deformity of the mid diaphysis and a subtle valgus deformity of the juxta-articularregion of the tibia. There is also a very mild distal femoral valgus and a leg length discrepancy. (8)The osteotomies were performed in the proximal metaphysis and in the mid diaphysis. The distalosteotomy is for the correction of the varus and the procurvatum deformities; the proximal osteotomyis for the correction of the juxta-articular valgus deformity. Notice the pattern .of the olive wires,which provide the necessary fulcrums and distraction points for this correction. (<:) The apparatusis shown in the immediate postoperative period. Each ring is oriented perpendicular to its own bonesegment. The mid diaphyseal hinge is properly located. The proximal tibial hinge was incorrectlylocated at the level of the osteotomy. This was one of the authors' earliest cases before completeunderstanding of the principles of angulation plus translation for juxta-articular deformities. (D) Atthe end of the correction, all of the rings are parallel and the hinges are straight. (E) The AP andlateral radiographs demonstrate the realignment of the tibia on both views as well as double levellengthening to equalize the limb length in equality. (F) The final radiograph demonstrates the reoalignment of the tibia with slight undercorrection of the distal angular deformity and slight over-correction of the proximal angular deformity. which made up for the lack of translation at theproximal osteotomy. The preoperative planning of this case is illustrated in Figure 61-39.

FIGURE 61-36. (A) Back view of an 18-year-old woman with severe bowleggedness from hypo- ~phosphatemic rickets. (8) The radiographs demonstrate the severity of the preoperative deformity.Both legs do not fit on the width of a normal film, even when the legs are crossed. Notice thebowing in the femur. Notice that the bowing in the femur is diffusely distributed throughout thelength of the femur, as is the bowing in the tibia. Notice also the lateral compartment joint laxityin the knee, which contributes the varus deformity. (C) The apparatus.is shown during constructionin the operating room. The femoral apparatus is applied first, followed by the tibial apparatus. Thetwo devices need to be coordinated to allow at least 900 of free flexion of the knee. Care must betaken so that the most distal femoral.and most proximal tibial rings do not collide. For this reasonincomplete rings (SJa rings) open posteriorly are applied adjacent to the knee. (D) The tibial apparatusfrom the frontal view. The hinges are locked at the measured deformity. The incision for the distalcorticotomy of the tibia is shown adjacent to the hinge. There are two levels of fixation within theproximal and distal segments. (E) At the completion of the realignment all of the rings of both thefemur and the tibia are parallel. Notice the axial increase in length from realignment of these severelybowed bones. (F) After removal of the apparatus the patient was left with a 10-cm leg-lengthdiscrepancy. The realigned limb stands in marked contrast to the uncorrected side. (G) The secondside was corrected after a 4-month hiatus. Notice that the left tibia was slightly overcorrected totry to compensate for the lateral knee joint laxity. On the right side the proximal fibula was pulleddown 1 em to tighten the lateral knee joint. Notice that even in bipedal stance the lateral knee jointis wider on the left than on the right leg. Notice also that the fibular head lies more distally on theright then on the left side. (H) The final clinical appearance of both legs shows normal alignmentwith an excellent cosmetic and functional result.

919

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920 RING FIXATION AND DISTRACTION TECHNIQUES

FIGURE 61-36.

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DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 921

FIGURE 61-36. (Continued)

FIGURE 61-37.

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922 RING FIXATION AND DISTRACTION TECHNIQUES

FIGURE 61-37. (A) A lateral photograph of the marked anterior bow("saber shin") deformity of the leg in a 75-year-old woman. (B)The lateralradiograph demonstrates monostotic Paget's disease with two levels ofununited stress fractures and an intact posterior fibular strut. (C) A pushconstruct was applied to the tibia. Notice the single level of fixation inthe proximal and distal tibia and three floating levels of fixation on oppositesides of the stress fractures. Anteriorly, a sliding plate suspends the threefloating half rings. The threaded rods off this plate are used to push in theapex of the deformity. On the concave side there are two distraction rods,of which only one can be seen on the photograph. Both a knee and an.ankle Dynasplint unit were used to help prevent joint contractures. (D)The apparatus is shown in situ at the beginning of the deformity correction.A fibular osteotomy was performed. The posterior aspect of the two non-unions can be seen to open slightly as the combined distraction and apicaltranslation are carried out. (E) At the end of the deformity correctionthere is an opening wedge at both nonunion sites. The proximal and distaltibial rings as well as the three floating half rings are all parallel. (F) Theapparatus was removed when a complete wall of cortical bone was seenposteriorly and when the fibula had united. This correction also equalizedthe patient's leg length. (G) The clinical appearance is excellent.

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DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 923

FIGURE 61-38. (A) Bilateral genu varum from varus deformities of both femurs and the right tibia.Both tibias have been previously operated upon. The right tibia still has a varus deformity. Thepreoperative planning of the right side of this deformity was illustrated in Figure 61·17. (B) A singlelevel of osteotomy was chosen for both the tibia and the femur. One could justify two levels ofosteotomy within each bone; however, since the amount of bowing in each bone was not severe,it was felt that this could be treated as a single apex angular deformity, recognizing that it trulywas a multi-apex angular deformity. Therefore, we chose to ignore the anatomic axis of the tibiaand realign both the mechanical axis of the tibia and the joint orientation of the knee and ankle.This gives the patient a result similar to that achieved on the plated left side. The alternative wouldhave been a combined proximal and distal tibial osteotomy, which would normalize both the anatomicand the mechanical axis of the tibia. An acute correction was performed in the femur at a level distalto the apex of the deformity, as described in Figure 61-17, to minimize the lateral indentation ofthe side that would result from a single-level more proximal osteotomy at the apex. (C) The resultdemonstrates complete realignment of the hip, knee, and ankle joint orientations as well as themechanical axis. On the opposite side the osteotomy was performed slightly distal to the apex ofthe deformity and, therefore, a lesser amount of translation was needed. The result in terms of jointalignment and orientation is identical.

Oblique plane angular deformities are just as easy to cor-rect as frontal or sagittal plane ones. More complex defor-mities including rotation, translation, and limb-length dis-crepancy can all be managed simultaneously. Multilevel andmultibone corrections can be done since there is little bloodloss and the apparatus can be applied to multiple levels andbones simultaneously. Lengthening is performed for smalland large discrepancies, as needed, at one or more levels.Associated problems of nonunion, contracture, and osteo-myelitis can be treated at the same time. The apparatus allowsfor unrestricted weight-bearing and personal hygiene;weight-bearing is usually restricted with internal fixation andbathing is difficult if a protective cast is used.

The main disadvantages of Ilizarov's method are thoserelated to external fixation, including wearing a bulky ap-paratus for a prolonged period, pin infections, muscle trans-fixion, loss of joint range of motion, and pain. With properapplication of the device, the latter three problems shouldbe minimal. More recently with the use of half pins insteadof transfixion wires these problems have been significantlyreduced.

Obviously, the distraction osteotomy is most advantageousin treating complex deformities. Nevertheless, it still offersmany advantages even for simple deformities that have agood conventional alternative, such as high tibial osteotomy.The decision to use Ilizarov's distraction method compared

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924 RING FIXATION AND DISTRACTIONTECHNIQUES

A Step 0 Step 1 Step 2A Step 28

B

to a conventional osteotomy and fixation depends on all ofthese factors, not the least of which is the surgeon's expe-rience in the application of the distraction osteotomy.

Basic Principlesof Deformity CorrectionUsing Circular External Fixation

There are two types of constructs for correcting deformity:focal hinges, and push/pull constructs.

Step 3A Step 38

FIGURE61·39. (A) Multi-apical an-gular deformity of the tibia with anormal femur. Step 0: Draw the me- .chanical axis line from the center ofthe hip to the center of the ankle,demonstrating minimal varus me-chanical axis deviation. The mal-alignment test was performed, dem-onstrating a normal distal femoralalignment. Step 1: Draw the proximaland distal tibial mechanical axis lines.Note that the intersection point is ata non-deformed level. The intersec-tion of these two lines is not at thelevel of the obvious deformity. Noticethat the proximal tibia also does notlie on this line. This indicates thatthere is a second apex of deformity.Step 2a: Draw the perpendicular tothe middle segnient of the tibia andextend this line proximally and dis-tally. This should intersect the me-chanical axis of the distal tibia at thelevel of the true apex of deformity.Step 2b: The same center of rotationis located by the convex cortexmethod. Step 3a: Correct the first de-formity at the level of the obviousapex. Extend the corrected distalmechanical axis line proximally. Thisintersects the proximal tibial me-chanica I line at the growth plate. Thisis the second apex. The second os-teotomy is of angulation and trans-lation to realign the tibia. (B)The ap-paratus before and after correction.

CENTER OF ROTATION HINGE TECHNIQUE

The basic construct for angular deformity correction usinghinges consists of two levels of fixation proximal and twolevels distal to the apex of deformity (Fig. 61-41). Each levelof fixation is perpendicular to either the anatomical or me-chanical axis of the bone fragment to which it is affixed. Thehinge connects the proximal and distal blocks of fixation,articulating between them at the desired center of rotationfor correcting the angular deformity."

If the hinge is placed at the apex of the deformity on theconvex side, then distraction of the concavity will lead to

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926 RING FIXATIONAND DISTRACTIONTECHNIQUES

FIGURE 61-41. (A) Center of rotation hinge apparatus. There are two levels of fixation in eachbone segment on. opposite sides of the osteotomy. The rings are applied perpendicular to theirrespective bone segment. The hinge lies perpendicular to the ring. In this example the hinge isapplied over the apex of the deformity, with the hinge rod overlying the medial convex cortex ofthe tibia. On the concave aspect there is a distraction rod connected by two twisted plates and asuspending post. The post connection to the twisted plate allows for self-adjustment of the distractionrod angle to that of the ring. (8) After the correction is completed all of the rings are parallel andthe hinge rods are colinear. Notice the open wedge correction of the tibia and fibula and the changein angle between the distraction rod and the ring. (C) For a juxta-articular deformity of the tibia, theapparatus employs a translation hinge. Notice that the hinge is located over the level of the tibialphysis. This is proximal to the upper ring. Two levels of fixation were achieved in each bone segmenton opposite sides of the osteotomy. (D) At the end of the correction there is an angulation andtranslation of the bone segments at the level of the osteotomy. The rings are now parallel and thehinge rod is straight. Notice again the change in orientation of the distraction rod to the rings.

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A

c

DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 927

an opening wedge correction (see Figs. 61-28 and 61-42A).If the hinge is placed at a distance from the convex side ofthe apex of the deformity, then lengthening will occur to-gether with correction of angular deformity (Figs. 61-42Band 61-43). Placing the hinge on the concave side of thedeformity will lead to compression of the bone ends withangular correction (Figs. 61-42C and 61-44). 1£the hinge isplaced either proximal or distal to the level of the osteotomy,then translation of the bone ends will occur with angularcorrection during distraction of the concavity (Figs. 61-42Dand 61-45).

Therefore, it is important to keep the hinge at the levelof the osteotomy to avoid any translation of the bone endswith respect to each other, unless translation is planned aspart of the correction." Conversely, if translation of the bone

B

oFIGURE 61-42. (A) Opening wedge hinge. The hinge is located at the level of the osteotomyoverlying the convex cortex of the bone. Distraction of the concavity leads to an opening wedgecorrection without separation of the convex cortices of the bone. (6) Distraction hinge. The hingeis located away from the convex cortex of the bone but still at the level of the osteotomy. Distractionof the concavity leads to simultaneous lengthening with angular correction. The regenerate has theappearance of a trapezoid, with a wider separation on the concave side than on the convex side.(C) Compression hinge. If the hinge is located at the level of the osteotomy but on the concave sideof the bone, distraction of the concavity will lead to compression of the bone ends. If the bone endsallow, this will produce a closing wedge type of correction. (0) Translation hinge. If the hinge islocated proximal or distal to the level of the osteotomy, distraction of the concavity will lead totranslation of the bone ends. In this example the hinge is located at the intersection point of theconvex cortices of the two bones and, therefore, distraction of the concavity leads to correction ofthe angulation and translation of the bone ends.

o

ends is desired, then the proper level of the hinge shouldbe selected. The level of the hinge is also governed by thebisector line of the angular deformity (Fig. 61-46).

To ensure that the desired correction is produced, thebone must be prevented from slipping along the wires (Fig.61-47). The bone must be locked into the apparatus in sucha way that the bone ends will follow the angular correctionof the rings. To create such a constrained system, the ap-propriate fulcrum and distraction points must be built in.The positions of fulcrum and distraction points is best de-scribed as a four-point bending maneuver (Fig. 61-48). The"rule of thumbs" is used to determine the location of thefulcrum and distraction points for simple angular correctionswithout translation of the bone ends.28,30 In coronal planedeformities, olive wires in the frontal plane are inserted ac-

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928 RING FIXATION AND DISTRACTION TECHNIQUES

FIGURE 61-43.

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~,:.J:II!_-.

FIGURE 61-44. Application of compression hinge. (A) Valgus defor-mity with nonunion of knee arthrodesis site. (8) The apparatus wasapplied with a hinge overlying the center of the knee joint so thatdistraction of the concavity would produce compression of the medialaspect of the nonunion and distraction of the lateral aspect of thenonunion. (C) The final result demonstrates correction of deformityand union.

...•••• FIGURE 61-43. Application of distraction hinges for lengthening and correction of deformity. (A)A 5-year-old girl with bilateral genu varum and shortening due to meningiococcemia septic emboli.She has skin grafts adherent to the bone and, therefore, distraction must be performed very gently.(8) Standing radiographs show the deformities and the preoperative planning markings for the place-ment of olive wires. (C) The apparatus has a hinge located lateral to the convex aspect of theosteotomy. To augment the stability of the fixation the distal hinge has a threaded rod appliedthrough the center of the anterior and posterior hinge point. This can be performed only withdistraction hinges. (D) Toward the end of the correction notice the increased length achieved throughthe distraction hinges without lengthening on the hinge rods. All of the lengthening is performedby distraction of the concavity. Notice that this method is gentle on the skin and there were no skinproblems. (E)The final radiographs demonstrate 8 em of lengthening of both tibias with realignment.Notice the bilateral triangular shaped tali. Both feet were plantigrade at the end of the correction.(F) The final appearance of both legs at the end of the lengthening and correction of deformities.

929

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930 RING FIXATION AND DISTRACTIONTECHNIQUES

FIGURE 61-45. (A) Application of translation hinge. Equinus malunion of ankle arthrodesis. (B)Thiswas treated by a supramalleolar osteotomy with application of a translation hinge. The hinge waslocated at the level of the calcaneotibial fusion; the osteotomy was performed 3 cm proximal tothat. (C) Simultaneous lengthening, angulation and translation were carried out. Notice the positionof the tibia overlying the mid-foot. The entire foot has translated posteriorly to give this girl a heeland to shorten the stiff forefoot, improving her ambulation. Notice the translational pattern of thetrabeculae.

FIGURE 61-46. Determination of hinge placement level' by the bi-sector concept. A, distraction hinge; B, opening wedge hinqe: C,compression hinge.

,,,\,

cording to the four-point bending rule of thumbs (see Fig.61-48). For sagittal plane deformities, transverse smoothwires in the frontal plane are used at all four levels of therule of thumbs instead of olive wires (Fig. 61-49). Alterna-tively, threaded half-pins can serve as fulcrums for eithersagittal or coronal plane deformities. It is preferable to usetwo olives counteropposed on the same side as the fulcrumor distraction point whenever possible. In the femur,threaded half-pins often substitute for olive wires.

For pure frontal plane translational correction, the olivesare placed counteropposed between blocks but on the sameside of the two levels of fixation within a block (Fig. 61-50).30 Therefore, the proximal twO olive wires are on thesame side and the distal two olive wires on the counterop-posed side. In this pattern, the olives act to push the bone'sdistal segment from its translated position toward the prop-erly aligned proximal segment.

For a combined angular and translational deformity cor-rection using a hinge, the olive wires are placed in a modifiedrule of thumbs to effect both translation and angulation (Fig.61- 51).28 This requires the addition. of a third olive wire onthe side without the hinge. The third olive wire is the trans-lation wire that forces the translational correction simulta-neous with the angular correction. If half-pins are used theyact to constrain the construct, thus replacing the need forolive wires.

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DEFORMITYCORRECTION BY THE ILIZAROVTECHNIQUE 931

cFIGURE 61-47. The principle of constraint of the apparatus to the bone. (A. B) If smooth wiresonly are used, distraction of the concavity of a deformity will lead to slippage on the smooth wires.The bone does not want to elongate with the correction but would rather move toward a part ofthe apparatus in which there is less elongation. Therefore, the bone moves from the convex side ofthe apparatus toward the concave side of the apparatus. This slippage leads to incomplete correctionof the bone by the time the rings are in a corrected position, and it may lead to impingement ofthe skin against the ring on the convex side of the deformity. (C.D) Applying olives over the apexof the deformity prevents slipping. The concave bone and soft tissues are forced to elongate.

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932 RING FIXATIONAND DISTRACTIONTECHNIQUES

FIGURE 61-48. The rule of thumbs. Four-point bending is the prin-ciple of correction in angular deformities. Olive wires are placed atthe fulcrum point on opposite sides of the apex of the deformity andat the distraction points at either end of the bone. The location ofthe olive wires can be remembered by thinking of the four pointbending rule of thumbs; the olive is located at the points where thethumbs press on the apex and the index fingers press on the endsof the bone.

In preoperative planning, first determine the level of os-teotomy and identify the magnitude and true plane of thedeformity. Construct an apparatus to correct the deformity.Two blocks of fixation are constructed, each with two levelsof fixation. The spacing between levels is planned accordingto the strategy of correction. If only angular correction isrequired, then the blocks should be as wide as possible, withonly a handbreadth separating the blocks at the level of thedeformity. If significant lengthening is planned, the distancebetween blocks must be greater to avoid skin entrapment.In this situation, the width of each block is narrower.

The hinge is placed in the axis of rotation of the angulardeformity, perpendicular to the plane of deformity. In ad-dition to the plane of the hinge axis, the level of the hingeand its function must be chosen. A hinge is placed either atthe level of the osteotomy or at a different level. The latterwill produce a translational effect during correction. Usuallythe hinge is placed at the level of the deformity'S apex and

FIGURE 61-49. In sagittal plane deformities the transverse wiresact to constrain the system in much the same way as olives do forfrontal plane deformities.

the osteotomy is done as close to that level as other consid-erations permit. The function of the hinge as opening wedgeor distraction will determine its distance from the center ofthe ring.

Once the hinge location is determined, the hinge is set atthe calculated magnitude of angular deformity and lockedin that position. A distraction rod is also placed betweenadjacent rings at a point halfway between the hinges on the

FIGURE61-50. For translational deformities, the olives should becounteropposed.

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FIGURE61-51. The modified rule of thumbs helps determine thelocation of the olives for combined angulation translational correc-tions. While one fragment is held as usual between the index andthumb, the other fragment is held with the thumb and index at thesame level on opposite sides of the bone and the middle finger inthe previous location of the index finqer, The olive pattern is illustratedin Figure 61-42D.

FIGURE 61-52. Push construct. (A) Thepush construct is shown applied to a pro-curvatum deformity of the tibia, similar to .the example illustrated in Figure 61-37. Theproximal and distal rings are perpendicularto their individual bone segments. The mid-dle half-rings are suspended off an anteriorplate. The plate, connected via buckles to aperpendicular shorter plate, pivots on thering on a hinge. The buckles allow the hor-izontal plates to slide up and down whilethe hinges allow the horizontal plate to alterits orientation to the ring as the deformitygradually corrects. The half-rings are con-nected. by threaded rods from posts on ei-ther side of the Icingplate. On the concavitythere are two distraction rods connectedby twisted plates and posts to allow autoadjustment at either end. Only a single wireis needed on each of the floating half rings,and two wires are used at either end on thefull ring. (B) By coordinating the distractionon the concavity with the translation on theconvexity, the deformity is gradually cor-rected. Notice that the buckles have movedtoward each other on the long plate.

DEFORMITY CORRECTION BY THE ILIZAROV TECHNIQUE 933

opposite side of the limb. The pre constructed frame is thenready for application.

PUSH/PULL CONSTRUCTS

The push/pull construct uses one fixed level within eachbone fragment and one floating level in each bone fragment(FIgs. 61-52 and 61-53).28 The proximal-most and distal-most levels are each affixed to a ring; distraction rods areapplied on the frame's concavity. On the convex side, therings are articulated with a long plate. The articulation onthe plate acts as both a pivot and a sliding joint. The apexof the deformity is either pushed or pulled into the concavity.A push construct uses smooth wires perpendicular to theplane of the deformity (see Fig. 61-52). A pull construct usesolive wires in the plane of deformity. The push wires areconnected to a translational apparatus. The pull olive wiresare connected using a slotted threaded rod translation ap-paratus (see Fig. 61-53).

Because there is only one fixed level within each bonesegment, this construct is less stable than the hinge construct.Therefore, this frame should be applied only to relativelystable pathologies such as stiff nonunions, bowing deformitieswith a large resistive tension band of soft tissue on the con-cavity (see Fig. 61-37), and bones that do not have greatloads applied to them, such as the forearm.

The most stable configuration for angular deformity cor-rection is constructed by a mix of push and hinged constructs(Fig. 61-54). Two levels of fixation within each bone segmentarticulated with hinges and a distraction rod on the concavity

Text continued on page 937

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934 RING FIXATION AND DISTRACTIONTECHNIQUES

n/

B

FIGURE 61-53. Pull construct. (A) The apparatus at thebeginning of the correction, with olive wires on slottedthreaded rods. The olive wires pull in the apex of the de-formity, much like the way the push wires push in the apexof the deformity. In the minor deformity shown, conicalwashers are used at either end for distraction. Alternatively,a focal hinge or twisted plate at either end could be used.(B)The appearance of the construct at the end of correction.(C) Preoperative AP roentgenograph of CPT previouslytreated by a nail and onlay grafting. Note the valgus ankleand proximal migration of the fibula. (D) Distraction of thestiff pseudoarthrosis using a pull construct to correct thedeformity. (E) Union, lengthening, and realignment wereall achieved. The fibula was transported distally. It wastransfixed with a screw to keep it from proximal migrationand a bone graft applied to synostose it to the tibia. Itremains united two years later. (C, D, E from Paley, D.,Catagni, M., Argnani, F., et al: Treatment of CongenitalPseudoarthrosis of the Tibia. Using the lIizarov Technique:Clin. Orthop. 280:91, 1992).

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DEFO.RMITY CORRECTION BY THE ILiZAROV TECHNIQUE 935

FIGURE 61-54. Combination hinge andpush constructs. (A) The strongest con-struct of all combines the two levels offixation of the hinge construct with the

. push construct. (B) This shows the con-struct at the end of deformity correction.(C) The construct shown in A and B wasapplied to a congenital pseudoarthrosis,which had malunited, in an effort tofracture the bone without an osteotomy.(0) I1izarov calls this method metaphy-sealysis. It can be used to focus largeconcentrated forces on weak, narrow-diameter bone regions. Notice the frac-ture of the bone that has occurred. (E)The final result, showing union and cor-rection of the deformity.

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Page 52: DEFORMITY' CORRECTION BY THE ILIZAROV TECHNIQUE

936 RING FIXATION AND DISTRACTION TECHNIQUEs

FIGURE 61-54. (Continued)

Page 53: DEFORMITY' CORRECTION BY THE ILIZAROV TECHNIQUE

FIGURE 61-55. (A) Acute rotational correctioncan be achieved by moving the rods around thering the same number of holes and then acutelytightening the nuts at either end of the rods, forc-ing the rods to become perpendicular to the ringand thus derotating the ring. (B, C, D) Acute der-otation can also be performed by advancing all thewires in the same direction by the same numberof holes and then tensioning them acutely. This isvery difficult, time-consuming, and painful, and israrely used.

are augmented by a push construct on the apical two ringsof the deformity to achieve augmented fixation and aug-mented constraints on the deformity.

CONSTRUCT CONSIDERATIONS.FOR ROTATIONAL DEFORMITIES

Most rotational deformities are corrected by rotational mod-ifications of the basic hinge frame. The rotational verticalinclined plane hinge, while a theoretical possibility, is usuallytoo complex to be readily applied (see Fig. 61-45). Twotypes of rotational corrections can be achieved with the cir-cular frame: acute and gradual.

The rotational correction -can be performed acutely bydisconnecting the frame and rotating one section with respectto the other. This can be done at the time of surgery. Becauseacute correction is too painful in most outpatient situations,a controlled acute method is preferable. One of these meth-ods is to angle the rods between one ring and the other andthen tighten them. If all the rods are angled one or two holesover, then an acute derotation of one or two holes is achieved(Fig. 61-55A,B), resulting in 5° to 10° of derotation, de-pending on the ring diameter. This can be repeated every

DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 937

few days until the correction is completed, usually with min-imal discomfort. An alternative method is to shift the wireon the ring (Fig. 61-55C,D) so as to bow each end of thewire in an opposite direction like a pinwheel; when the wiresare tensioned, the bone rotates. This method is usually toocomplex, time-consuming, and painful, since all the wiresneed to be loosened and retensioned.

The gradual method can be applied in one of many con-structs (Fig. 61-56A,B) at a set rate and rhythm determinedby bone and soft-tissue considerations. The gradual methodis the safest and involves the least amount of discomfort.

Since derotation occurs between adjacent rings, the con-figuration's center of the rotation is at the center of theserings. If the bone is located at the center of the ring, thenthe derotation will occur around the central axis of the bone.In most cases, however, the bone does not lie 'in the centerof the ring: in both the thigh and the shank, the bone iseccentrically located within the soft-tissue mass. To centerthe bone within a ring, a ring of very large diameter wouldbe needed, increasing the system's instability (Fig. 61-57).

As the derotation occurs around the center of a ring, aneccentrically placed bone will move sideways during rotation(Fig. 61-58). External rotation of the tibia leads to lateral

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938 RING FIXATION AND DISTRACTION TECHNIQUES

FIGURE 61-56. Gradual derotation canbe carried out by a variety of constructs.(A) One method uses horizontal threadedrods articulating between a post on onering and a threaded rod coming from theother ring. The threaded rod is connectedby two nuts to one ring, while at the otherend a buckle is attached to allow for axialsupport. Alternatively, a threaded rod canbe connected between two posts, but thisis less stable. Three of these constructsare connected around the ring. (B) Anothermethod of derotation is the ring within aring. With this method the proximal blockis connected to the outer ring and the dis-tal block to the inner ring. The articulationbetween the ring is by means of a pair ofplates protruding from three or four ID-eations. The plates are fixed to the innerring but not to the outer ring. They sand-wich the outer ring between either plate.A single horizontal threaded rod is usedto motor the derotation.

The translation-rotation point is on the bisector of the centerof each bone segment. Where this bisector crosses the ringis the location of the rotation center.

translation and internal rotation to medial rranslation.r" Toa lesser extent, internal rotation is associated with posteriortranslation and external rotation with anterior translation.In the femur with its anterior location, the same relationshipshold.

If significant translation occurs with derotation, a separatetranslational correction may be needed after derotation witheither a translation device or a derotation-translation device.The former uses a translation frame modification to movethe bone into the reduced position. The latter uses the trans-lation-rotation point to reduce the fragments (Fig. 61-59).

TRANSLATIONAL DEFORMITY CORRECTION

Translational deformity in combination with angulation wasdiscussed earlier. Translation may also be corrected inde-pendently of angulation, either acutely or gradually. Acutetranslational correction may be achieved with olive wiresand acute displacement using a wire tensioner (Fig. 61-60).

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FIGURE61-57. (A) The ring is nor-mally centered around the leg so thatthere is a minimum of two finger-breadths (3-4 cm) space between theinner edge of the ring and the skin.Notice that the center of the ring liesposterior and lateral to the center ofthe tibia. (B) To center the ring onthe bone it would be necessary touse a much larger ring to allow a min-imum of two fingerbreadths spacebetween the ring and the skin. Thisleads to less stable fixation.

A

DEFORMITYCORRECTIONBY THE ILIZAROVTECHNIQUE 939·

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FIGURE61-58. (A) Rotation of a ring that is centered on the leg.and not on the bone leads to (B)lateral translation of the bone. (C) This malunion required a correction of varus and rotation. Therewas also a lateral translational deformity. Notice that there are two lateral translations and onemedial translation of the united fragments. The net result is lateral translation. (0) A corticotomy atthe junction of the proximal and middle thirds of the tibia was performed, and the angular deformitycorrected at that level. The bone was then lengthened and derotated. Because the ring was centeredon the leg and not on the bone, a medial translational deformity, which can be seen, occurred. Inthis particular case this was therapeutic because it realigned the translation of the tibia. Therefore,the translational effect of the derotation in some cases can be used to achieve a desired translationalcorrection. Since the center of the ring is posterior to the tibia, internal rotation leads to medialtranslation while external rotation leads to lateral translation. This deformity must be factored intothe realignment of the leg, especially in large derotations.

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940 RING FIXATION AND DISTRACTION TECHNIQUES

••

FIGURE 61-58. (Continued)

FIGURE 61-59. (A) To correct the translational deformity created by a derotation, one can useeither conventional translational constructs or the more accurate translation rotation point. Thispoint is located on the ring equidistant from the center of the two bone ends. The true plane of thetranslation must be identified, and then a point between on the line connecting the centers of thetwo bones is projected to the ring as the right bisector of that line. (B) A threaded rod is connectedbetween the adjacent rings at that point and the rings are derotated around that threaded rod torotate one bone fragment into the other. This leads to reduction in the translational deformitywithout loss of the rotational correction.

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Alternatively, acute correction will occur when tensioningan arced wire from both ends. Gradual translational correc-tion can be achieved using gradual distraction on olive orarced wires using slotted threaded rods.

The most controlled way to correct translation is to usetranslational threaded rods articulating between parallel rings(Fig. 61-61). This allows very gradual translational movementin any direction. Unlike the rotational rods, which are ori-

FIGURE 61-60. (A) Acute trans-lational correction. Acute transla-tiona I correction can be performedby olive or arced wires. An olivewire can be pulled from the nono-live end to translate the bone frag-ment. (B) The same effect can becreated perpendicular to the wireby using the arced wire. The wireis displaced one hole in the direc-tion of the desired translation. (C)Tensioners are applied to both sidesof the wire to pull out the arc andthus displace the bone into theconcavity of the arc. (0) For largedisplacements, the original Russianwire tensioners are used. (E) An-other acute method of effecting atranslational correction is similar tothe acute rotational method by dis-placing the threaded rods. (F) Theacute translational correction isperformed by tighte~ng the nutsin the threaded rods.

DEFORMITY CORRECTION BY THE ILIZAROV TECHNIQUE 941

ented tangential to the ring, the translational rods are ori-ented parallel to each other in the direction of translation.

ORDER OF CORRECTIONFOR COMPLEX DEFORMITIESComplex deformities may have components of angulation,rotation, translation, and shortening. In correcting combi-

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_.942 RING FIXATION AND DISTRACTION TECHNIQUES

nations of deformity, the order of corrections is important.Complex deformities can be divided into two groups: thosewith and those without bone segments that must translatewith respect to each other. Unlike lines on paper, segmentsof bone cannot slide past each other without colliding.Therefore, any manipulation that will lead to collision of onebone segment with another will cause obstruction and jam-ming of the system.

Therefore, the order of correction can be planned de-pending on the likelihood of potential segment collision andjamming (Fig. 61-62). Collision and jamming may occurwhen translation or rotation of bone fragments is requiredas part of the correction. The propensity for collision andjamming depends on the configuration of the bone fragmentswith respect to each other and the contour of their boneends. Obviously, a transverse osteotomy through a bone withno overlap of the bone segment will allow movements ofangulation, rotation, translation, and lengthening withoutcollision and damage. On the other hand, if the two bonesegments overlap, translation or angulation will be ob-structed. In such a situation, the surgeon must first lengthenthe limb and then correct angulation and translation together(see Figs. 61-62 and 61-63). When there is an oblique orspiral osteotomy and rotational correction is required,lengthening must be done first to avoid collision and jammingof the oblique bone segments with each other.

The order of correction also depends on the expected rateof healing of the bone or the patient. In younger children,the expected rate of healing is faster than in adults. Openwedge angulation correction carries a risk of premature con-solidation on the convex side; this would prevent subsequentlengthening. This risk is small in adults but significant inchildren. Therefore, the order of correction in adults andchildren may be different.

FIGURE 61·61. (A) Gradual translationalcorrections are carried out by connectinghorizontal threaded rods all parallel to eachother. Three of these connections arenecessary. (8) The end of the translationalcorrection.

In patients with no risk of jamming and collision and inwhom premature consolidation is not a concern, the orderof correction is angulation, lengthening, rotation, and trans-lation (see Fig. 61-63A).

In patients with no risk for jamming and collision but atrisk for premature consolidation, the order is angulation andlengthening, rotation, and translation (see Fig. 61-63B). Inthese patients the angulation and lengthening may be donesimultaneously using a distraction hinge or lengthening onthe hinged rods at differential rates from the distraction rods.In this situation some of the length and some of the angu-lation are corrected simultaneously until the angular defor-mity or the length discrepancy is completely corrected,leaving either residual angular or length deformity to correct.This is followed by derotation and translation.

If jamming and collision are expected, the order of cor-rection is lengthenmg, angulation, remaining lengthening,rotation, and translation (see Fig. 61-63C).

It is preferable to carry out both rotation and translationthrough long segments of regenerate new bone, where theshearing effect of these displacements can be distributedalong the soft bone and blood vessels. There is far greatershear between bone ends of an undisrracted osteotomy(leading to disruption of medullary and periosteal tissuesduring translation or rotation) than there is between boneends that are separated several centimeters.

Translation should be carried out after rotation because atranslational displacement may occur during derotation ofan eccentrically located bone. This displacement may beused to the surgeon's advantage if both the translational de-formity and the rotational deformity are in the same direc-tion. In these cases, the bone ends can be rotated, therebycorrecting translation and rotation simultaneously.

If the bone is rapidly consolidating, the rotational correc-

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FIGURE 61-62. (A) When a translational correction is to .be performed at the same time as an angular correctionby means of a translational hinge, jamming of the boneends may occur. (B) A valgus malnonunion of the distaltibia. A translational distraction hinge is in place to correctthe length, angulation, and translation simultaneously. (C)Notice that the angulation was corrected but the translationwas not correctable because of jamming of the bone ends.The deformity should have been distracted first to separatethe bone ends, and then the hinge should have beenactivated.

tion can be performed last, since rotation is possible withsignificantly consolidated regenerate bone. Correction oftranslation is difficult in the presence of advanced consoli-dation. Angulation is feasible even later than rotation in theface of advanced consolidation. Therefore, the order of de-formity correction may need to be altered if the bone seg-ments show evidence of premature or advanced consoli-dation. In these cases, the surgeon may want to correcttranslation first, derotate next, and finally correct theangulation.

RATE OF CORRECTIONThe accepted average rate of distraction for osteogenesisand soft-tissue neohistogenesis is 1 mm/day in O.25-mmintervals."?" In limb lengthening, all the distraction rodscan be lengthened at this rate to create a separation of thebone fragments of 1 mmJday. In angular correction, a cal-

DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 943

culation must be made to obtain a rate of distraction of 1mm/day of the osteotomy site. We use the geometric rule ofsimilar triangles (Fig. 61-64), which allows us to calculatethe rate of distraction of the threaded rods that will producea 1 mmJday distraction rate at the level of the bone.r" Asthe lengthening proceeds, the rule of similar triangles mustbe recalculated because the distraction rod approaches theconcave aspect of the bone. For small deformities this isinconsequential, but with large deformities it is significant.

The deformity correction actually follows concentric cir-cles (rather than triangles) that radiate around the hingepoint. The calculation of the length of arc followed by theconcentric circle at the radius R from the hinge is an ap-proximation of the length of time needed to correct the de-formity (Fig. 61-65).11

The bone is not always the tissue that determines the rateof lengthening. For example, in a contracture of the knee,correction may be adjusted so that the sciatic nerve is dis-

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944 RING FIXATION AND DISTRACTION TECHNIQUES

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C, 4FIGURE 61.63. Order of derormity correction. The order of correction depends on the risk ofpremature consolidation and the propensity for jamming of the bone ends. (A) Order I: 1) angulation;2) lengthening; 3) derotation; 4) translation. (8) Order II: 1) simultaneous angular correction andlengthening; 2) derotation; 3) translation. (C) Order III: 1) partial lengthening; 2) angulation; 3)lengthening; 4) derotation; 5) translation.

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Page 61: DEFORMITY' CORRECTION BY THE ILIZAROV TECHNIQUE

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DEFORMITY CORRECTION BY THE ILiZAROV TECHNIQUE 945

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FIGURE 61-64. Rule of similar triangles. The rate of distraction of tne distraction rod D that willproduce 1 mm of opening wedge at the concave cortex of the tibia T is calculated based on similartriangles. In the example shown the ratio is 4:1. Therefore, it takes 4 mm of distraction at thedistraction rod to produce 1 mm of opening wedge of the tibia. In contrast, the fibula lies halfwaybetween the distraction rod and the hinge. Therefore, at 4 mmjday distraction, the fibula willlengthen 2 mmjday. Because the peroneal nerve is at the level of the fibula, it may be preferableto open the wedge relative to a 1 mm rate of the fibula rather than the tibia.

tracted at a maximum of 1 mmlday (Fig. 61-66). The cal-culation of the length R is made from the center of the hingeto the sciatic nerve. Similarly, in valgus corrections of thetibia, the peroneal nerve may be the structure determiningthe rate of distraction.

Sometimes it is important to calculate not only the rateof distraction, but also the rate of compression on the bone'sopposite side. This can be done by the reciprocal rule ofttiangles (Fig. 61-67). In most cases, distracting one side atthe rate of similar triangles and allowing the apparatus toself-adjust on the compression side avoids any errors of rateadjustment between the two sides.

Another method to calculate the time required for defor-mity correction is to measure the distance between the ringsat the level of the hinge and the distance between the ringsat the level of the distraction rod. The distance betweenrings at the hinge will change little before and after deformity

correction if no distraction is carried out on the hinge rods.The difference between the hinge rod width and the dis-traction rod width divided by the rate of correction is anaccurate approximation of the time needed for correction(see Fig. 61-67). At the end of correction the rings shouldbe parallel if the apparatus was properly applied. Therefore,the difference between the distraction rod width and thehinged rod width will eventually be zero.

The rate of correction is also important for the push con-struct (Fig. 61-68). In the push construct, the apex of thedeformity is being translated while the ends of the deformityare distracted.

Correction of a pure translational deformity should bedone at a rate of 0.5 to 1.0 mm/day. When translation isdone through a lengthy distraction gap, 1 mm/day is used;0.5 mm/day is used when translation is done through a nar-row distraction gap or through an undistracted osteotomy.

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946 RING FIXATION AND DISTRACTION TECHNIQUES

-

FIGURE 61-65. The rule of concentric circles. Because the de-formity correction is occurring around a hinge, the true patternof correction follows the path of an arc of radius r where ris thewidth of the bone at the level of the osteotomy. Because the rate

. of correction is set to 1 rum/day at the concave cortex of thetibia, the length of the arc across the concave cortex is equal tothe number of days it will take to correct the angular deformity.Arc length can be calculated as the number of degrees subtendedby the arc divided by 360 times the circumference of the circle(27rr). For a deformity of magnitude 0:, the number of days toachieve correction of deformity is 211'r0:/360.

FIGURE 61-66. Reciprocal rule of triangles. It is sometimes necessary to distract on one side of adeformity and compress on the other side. For example, in this knee contracture the rate of distractionof the concave distraction rod is calculated by the rule of similar triangles. The rate of compressionof the convex rod is a factor of r3 to r2, the rate of the distraction rod. In the example shown, therate of distraction or compression are related to stretching of the most important tissue which inthis case is the sciatic nerve. The sciatic nerve is located at a distance of r' from the center ofrotation. The length r' is used in the calculation of similar triangles.

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DEFORMITYCORRECTIONBY THE ILIZAROVTECHNIQ'UE 947

TJ

FIGURE61-67. Alternate method for calculating the treatment timefor angular correction. A quick and simple method for calculatingthe total number of days of distraction until the rings become parallelis to subtract the length of the distraction rod between its connectionpoint on the ring from the length of the hinge rods. (A) When thehinge lies on the ring, the space between the rings is used as thelength d'. (B)When the hinge lies between the rings, the limb aboveand below the hinge are added (d' + d2) and then d3 is subtractedfrom the sum of the other two. The difference d4 is then divided bythe rate of distraction of rod d3 to calculate the total treatment time.

A

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FIGURE61-68. Coordinate the rate of apical transla-tion with that of concavity distraction. Step 1: Use therule of similar triangles to calculate the rate of distrac-tion at the distraction rod. Step 2: Use the 211"ra/360calculation to determine the number of days until com-plete deformity correction. Step 3: Measure the distancefor complete apical translation from the center of thebone at the level of the apex to the line connecting thecenter of the joint above with the center of the jointbelow. Step 4: Divide the total distance to be translated(T)by the number of days of correction. This will be therate for apical translation. A

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948 RING FIXATION AND DISTRACTION TECHNIQUES

The rate of correction for a rotational deformity is about1 mm/day at the surface of the bone. The number of degreesof rotation to keep the surface rotation rate to 1 mm/daydepends on the diameter of the bone: 12° for a l-cm-diameter bone, 6° for a 2-cm-diameter bone, 4° for a 3-ern-diameter bone, and 3° for a 4-cm-diameter bone. Therate should be adjusted for small and large bones.

The rate of rotational correction using the gradual tech-nique depends on the ring size. The number of degrees be-tween adjacent holes is equal to 360° divided by the totalnumber of holes. (The count should include the solid portionof the rings adjacent to the flare [four per ring, two per half-ring].) Dividing the number of millimeters per hole by thenumber of degrees per hole gives the number of millimetersper degree of arc. Multiply this by the number of degreespermissible for different diameter bones to get the rate ofcorrection. Divide this number by three or four times perday to split the rate into a dosed rhythm of correction. Inmost cases this works out to be 1 mm three to five timesper day.

It is important not to exceed these guidelines except whenabove-average bone formation is seen. These guidelines serveto optimize the new bone formation according to the basicbiological principles of Ilizarov.!" They must be altered insituations of hypo trophic and hypertrophic bone formation.In the former the rate may be cut by 25% to 50% as needed,while in the latter the rate may be increased by similaramounts.

.Acknowledgment

We would like to thank Michael Leonard and Stacy Lund for allthe work they put into the preparation of illustrations.

REFERENCES1. Bar, H.F., and Breitfuss, H.: Analysis of Angular Deformities on Radio-

graphs. j. Bone jt. Surg. 7l-B:710, 1989.2. Bombelli, R.: Osteoarthritis of the Hip, 2nd ed. Berlin, Springer-Verlag,

1983.3. Chao, E.Y.S., Paley, D., et al.: Mechanical Axis Alignment and joint

Orientation of the Hip, Knee and Ankle (in preparation).4. Cooke, T.D.V.,Pichora, D., Siu, D., Scudamore, RA, and Bryant, ].T.:

Surgical Implications of Varus Deformity of the Knee with Obliquityof joint Surfaces.]. Bone jt. Surg. 7l-B:560, 1989.

5. Cooke, T.D.V., Siu, D., and Fisher, B.: The Use of Standardized Ra-diographs to Identify the Deformities Associated with Osteoarthritis.In Noble,]., and Galasko, C.S.B. (eds.): Recent Developments in Or-thopedic Surgery. Manchester University Press, 1987.

6. Coventry, M.B.:Upper Tibial Osteotomy for Osteoarthritis.]. Bone jt,Surg. 67-A:1l36, 1985.

7. Coventry, M.B.:Proximal Tibial Varus Osteotomy for Osteoarthritis ofthe Lateral Compartment of the Knee. j. Bone jt. Surg. 69-A:32, 1987.

8. Halpern, A.A.,Tanner,]., and Rinsky, L.: Does Persistent Fetal FemoralAnteversion Contribute to Osteoarthritis? Clin. Orthop. 145:213, 1979.

9. Harrington, 1.].: Static and Dynamic Loading Patterns in Knee jointswith Deformities. ]. Bone jt. Surg. 65-A:247, 1983.

10. Healy, W.L., Anglen,].O., Wasilewski, SA, and Krackow, K.A.:DistalFemoral Varus Osteotomy.]. Bone jt. Surg. 70-A:I02, 1988.

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