Health & Medicine
PRINCIPLES OF DEFORMITY CORRECTION
Prepared by: Supervised by:Dr. Abdullah K. Ghafour Dr. Hamid Ahmed Jaff3rd year IBFMS trainee
frontal plane-mechanical frontal plane-anatomical sagittal plane-anatomical
Introduction Deformity: It’s the position of a limb/Joint, from
which it cannot be brought back to its normal anatomical position.
Described as abnormalities of : Length Angulation Rotation Translation Combination
Introduction Evaluation of Deformity:
History Clinical examination Radiological Examination
X-rays o Long films (51 Inches)o Frontal plane (AP view)o Sagittal plane (Lateral view)
CT Scanso CT Scanogram
Malalignment refers to the loss of collinearity of the hip, knee, and ankle in the frontal plane.
Therefore, if the MAD exceeds the normal range, there is malalignment
Frontal plane MAD may arise from four anatomic sources:1. femoral frontal plane deformity2. tibial frontal plane deformity3. frontal plane knee joint laxity4. femoral or tibial condylar
Malalignment and Malorientation
Malalignment and Malorientation
Paley and Tetsworth (1992) designed a malalignment test (MAT) to identify the source(s) of the MAD. MAT identifies only which bone or joint source contributes to the MAD that is measured. It does not identify the level of deformity in the femur or tibia
Steps of MAT: Step 0: Measure the MAD
normal range is 1-15 mm medial Varus > 15mm – 1mm< valgus
Step 1: Measure the mLDFA normal range is 85°-90° outside the normal range femur
is contributing to the MAD. Varus > 85° - 90° < valgus
Malalignment and Malorientation
Step 2: Measure the MPTA normal range is 85°-90° outside the normal range tibia
is contributing to the MAD. Valgus > 85° - 90° < varus
Step 3: Measure the JLCA normal range is 0°_2° medial Medial JLCA > 2° means varus lateral JLCA > 2° means valgus outside the normal range loss
of cartilage height and ligamentous laxity is contributing to the MAD.
Malalignment and Malorientation Addendum 1: Rule Out
Knee Joint Subluxation
Compare the midpoints of the femoral and tibial knee joint orientation lines.Normally, they should be within 3 mm of each other.
Malalignment and Malorientation Addendum 2: Rule Out Condylar
Compare the joint lines of the medial and lateral plateaus with each other. They should be collinear.Comparethe lines tangential to the medial and lateral femoral condyles. They should be collinear.
Malalignment and Malorientation Malorientation of the ankle
or hip joints usually leads to minimal or no MAD because the deformity apex is at or near the ends of the mechanical axis of the lower limb.
Ankle joint orientation assessed by measuring mLDTA and aLDTA.
Hip joint orientation assessed by measuring mLPFA, aMPFA and aMNSA.
center of rotation of angulation When a bone is divided and
angulated, the mechanical and anatomic axes of the bone are also divided into proximal and distal segments.
The pairs of proximal and distal axis lines intersect to form an angle, this point is called the center of rotation of angulation (CORA).
center of rotation of angulation CORA Method:
Step 0: malalignment test (MAT)Step 1: draw PAA and PMAStep 2: draw DAA and DMAStep 3: Decide whether this is uniapical or multiapical angulation:mark the CORA(s), and measure the magnitude(s)
Sagittal Plane Deformities the sagittal plane alignment of the hip,
knee, and ankle changes with normal knee motion and gait.
The line from the center of rotation of the hip to the center of rotation of the ankle is the mechanical axis of the lower limb in the sagittal plane.
With the knee in full extension, it passes anterior to the center of rotation of the knee joint while it become collinear at approximately 5°_10° of knee flexion
Sagittal Plane Deformities Knee malalignment in the sagittal
plane is better tolerated than in the frontal plane because all three joints move in the sagittal plane and can therefore compensate for sagittal malalignment.
Flexion malalignment is present when the mechanical axis of the lower limb does not pass anterior to the center of rotation of the knee in maximum extension.
Extension malalignment is present when the knee can be hyperextended passively more than 5°
Sagittal Plane Deformities Knee Joint Malorientation: The joint
orientation of the distal femur and of the proximal tibia is measured to the adjacent anatomic axis line by using PDFA (83±4°) and PPTA (81 ±4°).
PDFA < 79°, there is overall procurvatum deformity of the distal femoral joint line
PDFA > 87°, there is overall recurvatum deformity of the distal femoral joint line
Knee Joint Malorientation:
PPTA < 77°, there is overall procurvatum deformity of the proximal tibial joint line.
PPTA > 85°, there is overall recurvatum deformity of the proximal tibial joint line.
Sagittal Plane Deformities
Sagittal Plane Deformities Hip Joint Malorientation:• The aPPFA is normally 90°.• The anterior NSA (ANSA) is
normally 170±5°. • The proximal and distal mid-
diaphyseal lines of the femur intersect in the mid-femur. The normal (MDA) is approximately 10°.
Sagittal Plane Deformities Ankle Joint Malorientation: Draw the distal mid-
diaphyseal line of the tibia, and measure the ADTA. If the ADTA is less than 78° or greater than 85°, there is malorientation of the ankle joint line relative to the DAA line.
CORA in sagittal plane Step 1:Draw the mid-diaphyseal line(s) to
represent the diaphysis of the bone. Step 2:Decide whether the joint orientation angles
are normal (PPTA,ADTA) foe tibia and PDFA for femur.
Step 3:Decide whether this is uniapical or multiapical angulation. Mark the CORA(s) and measure the magnitude(s)
Oblique Plane Deformities The apical direction of an oblique plane
angulation is either anterolateral, anteromedial, posterolateral, or posteromedial.
If a radiograph could be obtained exactly perpendicular to the oblique plane, the magnitude could be measured directly.
Oblique Plane Deformities Knowing the magnitudes of
angulation measured off the AP and LAT radiographs, the magnitude of the true angulation in the oblique plane can be calculated by:
Translation Deformity Translation deformity refers to displacement
deformity. It occurs secondary to fractures and osteotomies.
Translation deformity parameters: (a) plane, (b) direction, (c) magnitude, and (d) level.
Osteotomy Concepts There are two basic osteotomy types for angular
deformity correction: 1. angulation-only osteotomies
opening wedge closing wedge
2. angulation with translation osteotomies. circular cut (dome) Oblique cut
The axis line around which the correction is performed is the Angulation Correction Axis (ACA)
Osteotomy Concepts A line passing through the CORA dividing the
transverse angle into two equal parts is called the transverse bisector line (tBL)
Each point on tBL line can be considered a CORA When the ACA passes through CORA the point is called an ACA-CORA
Osteotomy Concepts Osteotomy Rules: Osteotomy rule 1: When the osteotomy
and ACA pass through any of the CORAs, realignment occurs without translation.
Osteotomy Concepts Osteotomy Rules: Osteotomy rule 2: When the ACA is
through the CORA but the osteotomy is at a different level, the axis will realign by angulation and translation at the osteotomy site.
Osteotomy Concepts Osteotomy Rules: Osteotomy rule 3: When the
osteotomy and ACA are at a level above or below the CORAs the proximal and distal axes of the bone will be parallel but translational deformity will result.
Osteotomy types Opening Wedge Osteotomy: The CORA and ACA lie on the
cortex on the convex side of the deformity.
The cortex on the concave side of the deformity is distracted to restore alignment, opening an empty wedge that traverses the diameter of the bone.
Opening wedge osteotomy increases final bone length.
Osteotomy types Closing Wedge Osteotomy: The CORA and ACA lie on the
concave cortex of the deformity. The cortex on the convex side
of the deformity is compressed to restore alignment, requiring removal of a bone wedge across the entire bone diameter.
A closing wedge osteotomy decreases final bone length.
Osteotomy types Neutral wedge osteotomy: The CORA and ACA lie in the middle of the bone. The concave side cortex is distracted and the
convex side cortex is compressed. A bone wedge is removed from the convex side. Neutral wedge osteotomy has no effect on final
Osteotomy types Focal Dome Osteotomy: The osteotomy is a cylindrical
shaped cut in three dimensions .
the osteotomy site cannot pass through both the CORA and the correction axis. Thus, translation will always occur when using a dome osteotomy.
Translation deformity correction Translational deformities may be
corrected in one of three ways. Transverse cut osteotomy:
Oblique cut osteotomy:
Length discrepancy correction Acute distraction or
compression methods obtain immediate correction of limb length by acute lengthening with bone grafting or acute shortening, respectively
Gradual correction techniques for length deformities typically use Ilizarov external fixation/ LRS
PRINCIPLES OF DEFORMITY CORRECTION
For more information please read this genius book for (Dr. DROR PALEY).
References • Paley D., Herzenberg J. E. (editorial assistance),  Principles
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