CHAPTER 3THE COLIAPSING PES VALGO PLANUS FOOTKieran T. Maban, M.5., D.P.M.

It can be considered bold to designate anyone asthe Father of any particular aspect of foot andankle surgery. In the case of flatfoot surgery, I feelconfident that there would be little disagreementwith the statement that E. Dalton McGlamry, DPMis the father of modern collapsing pes valgo planus(CP\?) surgery. More important than his introduc-tion and popularization of cefiain procedures hasbeen his consistent underlying philosophy regard-ing the significance of the pathology. Much of themedical community has looked upon CPVP surgeryas a cosmetic exercise, seeing little functionalimportance. Early on, Dr. McGlamry recognized thedestructive effects of equinus and CP\? along withthe dysfunctional pain they inflict upon patients.lPerhaps now, with the much greater awareness oftibialis posterior dysfunction (TPD) in the adult, wecan see that CPVP is the precursor in a continuumof failure of the stabilizing mechanisms of the footwith eventual collapse.

PATHOLOGY

Equinus is a severely destructive force, either as aprimary aspect of the deformity or as a secondaryresult of the CP\?. Vhen the equinus is the pri-mary deforming force, compensation will occur indistal joints such as the subtalar joint (SU) and themidtarsal joints. How that compensation becomesexpressed in a particular way is unclear. Thehypothesis of planal dominance is helpful inexplaining some forms of compensation.'Z Thishypothesis is based on two premises: 1. The axis ofmotion of the STJ can vary widely, with extremesbeing a vefiical, horizonlal, or longitudinal axis.The average STJ axis of 42 degrees up from thetransverse plane, 15 degrees medial from the lon-gitudinal axis, may in fact exist. More common is alarge amount of variation from the normal.2. Compensation occurs in a plane perpendicularto the STJ axis. Thus a STJ with a verticaT axis willcompensate in the transverse plane.

There are difficulties with the planal domi-nance hypothesis. First, it is clear that the motion of

the STJ is much more complex and dynamic thancan be explained with planal dominance. Second,the axis of the STJ can only be infered clinicallyand not measured. \7e infer the axis of motionbased upon radiographic and clinical findings.Radiographically, some joint relationships arethought to be representative of certain axes. Forexample, a high cuboid abduction angle combinedwith reduced talo-navicular articulation are inter-preted to be representative of transverse planecompensation from a vefiical axis. Clinically, onecan place the STJ through its range of motion andappreciate, in some patients, a tendency for motionto occur predominantly in one plane. Nonetheless,the planal dominance hypothesis is a useful way toinitially look at feet with CP\?.

Regardless of where the pathology occurs, theprimary element of the pathology is instabiliry. Themedial column is most often visible as the arca ofgreatest instabiliry. This is apparcnt in static stanceas a lowered medial arch with heel valgus. In gait,the medial column is seen to be initially stable withcollapse of the arch during midstance and heel-off.Vithin the medial column, the instability can occurat the talo-navicular joinl, the navicular cuneiformjoint, or the first metatarsocuneiform joint. In theseverely collapsed foot (usually an adult), instabil-i\r can also occur at the ankle level, with stretchingand failure of the deltold ligament. In the child,compensation seems to occur more often at lhetalo-navicular joint. Medial column instabilicy wasonce thought to be the primary deformity, and con-sequently was the subject of numerous surgicalapproaches. These included soft tissue re-balancingprocedures such as the Kidner or Young, andfusions such as the Hoke and the Miller. TheLowman procedure combined elements of both.3

Other approaches addressed the rearfooteither through the orientation of the calcaneus(Silver, Kontsogiannis) or by blocking of excesssubtalar motion (Gleich). Although lateral openingwedge osteotomies seem logical for frontal planedominant CP\?, they have diminished in popular-ity in recent years because of the greater

I8 CHAPTER 3

multi-planar changes effected by the Evansosteotomy. The subtalar blocking approachremains popular with the use of a variety ofarthroeresis devices.

ETIOLOGY

Donald R. Green, DPM, San Diego, California, haswritten and lectured extensively on the biome-chanics of CP\?. He describes the following asetiologies of CPVP:31. Forefoot varus2. Flexible forefoot valgus3. Equinus4. Congenital talipes calcaneovalgus5. Torsional abnormalities6. Muscle imbalance7. Ligamentous laxityB. Neurotrophic feet9. Any factor (such as obesity) that produces a

medial shift in weight bearing

EVAIUAIION

Evaluation of the CP\? foot is complex. It iscritical to identfi the primary deforming force andthe primary site of compensation. These componentsof evaluation include structural examination, muscleinventory, biomechanical evaluation, radiographicanalysis, Hubscher maneuvet clinical gait analysis,and quantitative gait analysis.

Once the evaluation is complete, thephysician can consider the benefits of surgicalversus conservative care. Indications for surgicalrepair include pain unrelieved by conservative care,progression of the deformity, instability, anddeformity. These indications are modfied by thepatient's age, weight, degree of pathology, functionaldemands, and response to conserwative care.

PODIATRY INSTITUTE EVOLUTION

The Podiatry Institute approach has evolved con-siderably over the past25 years. Initially, the Youngsuspension was used, based on outstanding resultsreported in ihe European literature. The responsewas good, particularly for creating some plan-tarflexion of the first rzy, and stabilizing thenavicular cuneiform joint. Advancement of tibialisposterior was then added to create some transverse

plane stability. Later, additional tendon work wasrecommended, including flexor digitorum longustransfer and peroneus brevis to longusanastomosis. Tendo Achillis lengthening was addedearly on to reduce the deforming forces created byequinus. Later still, the Evans calcaneal osteotomywas added, after James V. Ganley DPM hadintroduced it to the profession.'

TREATMENT

The Evans calcaneal osteotomy is an impressiveprocedure that creates significant stability in therearfoot and midfoot without arthrodesis.Originally described by Dillwyn Evans as a proce-dure for treatment of over-corrected clubfoot andrigid flatfoot, the procedure became useful as atreatment for CP\?.i The procedure involves ananterior calcaneal osteotomy with lengthening ofthe lateral column with a bone graft. This proce-dure has become the dominant flatfoot procedureamong The Podiatry Institute faculty.

Some critical elements for success of theEvans calcaneal osteotomy include:1. Oblique incision, with careful attention to avoid

the sural and intermediate dorsal cutaneousnerves.

2. Reflection of the EDB muscle be11y, being care-ful not to disturb ligamentous attachments at thedorsal calcaneal cuboid joint.

3. Through-and-through calcaneal osteotomy,about 1 cm proximal to the calcaneal cuboidjoint. It should be angulated slightly distal aswell.

4. Distraction of the osteotomy with a baby laminaspreader or with pins and distractor to facilitateinsefiion of a truncated wedge of aliogeneic orautogenous iliac crest (tri-cortical bone). Thegraft is usually about 1 cm at its widest part andtapers to 7 mm medially. An additional piece ofgraft can be applied to fill the remainder of thedefect, although it is not mandatory.

5. Fixation of the graft is left to the judgement ofthe surgeon.

6. Check the sagittal plane alignment, parlicularlylaterally. Check the patient for equinus andcorrect as necessary.

7. Maintain the patient in a non-weight-bearingcast for B weeks and allow protected weightbearing after that point, if radiographs showgood consolidation.

CHAPTER 3 I9

The sagittal plane correction in the lateralcolumn occurs with plantarflexion of the cuboid onthe calcaneus. The mechanism for this plantarflex-ion originates with the plantar calcaneal cuboidligaments. As the lateral column is lengthened, theligaments become stretched, and the cuboid andcalcaneus are drawn toward each other, resulting inan increase in the calcaneal pitch. The procedure iseffective in realigning ihe talo-navicular joint, andreducing the cuboid abduction ang1e.6

Can the Evans be performed as an isolatedprocedure? Yes, howevet, the author rarelyperforms it alone. Augmentation by medial columnfusions and tendon balancing procedures will helpreduce the forefoot varus and increase stabilitywithin the medial coiumn. The author usuallyperforms the medial column tendon suspension,consisting of the Young suspension of tibialis ante-rior through the navicular, advancement of tibialisposterior, and possibly tightening of the springligament. In sequence, the lateral osteotomy isperformed first, and then the medial column ischecked for position and stability with the laminaspreader holding the osteotomy open. The medialcolumn is then opened if necessary, and the sus-pension performed. The procedure is easier toperform before the Evans bone graft has beeninserted, which reduces mobility of the midfoot.Mosca6 uses a medial cuneiform osteotomy toaddress medial column position and adductus ofthe forefoot (skewfoot).

SUMMARY

The CPVP foot is a surgical challenge. Recognitionof the morbidity created by instability in the footand ankle is increasing, but the general medicalcommunity is still generally Lrnaware of the signifi-cance of CP\?. The Evans is a powerful andimportant procedure for stabilizing the foot. Themedial column suspension improves both positionand stability.

REFERENCES

1. Beck E, McGlamry ED: Modified Young tendosuspension for theflatfoot. J Am Pod.id* Assoc 63:582-604. 1973.

2. Pressman MM: Biomechanics and surgical criteria for flexible pesvalgtrs. J Am Pod Med Assoc 77:7-13, 1987.

3, Mahan KT: Pes planovalgus deformiry. In McGlamry ED, BanksAS, Downey N4S, eds. Comprebensiue Textbook of Foctt Surgery.2nd ed. Baltimore. Md: $f illiams and Wilkins; f992: 769'817.

4. Mahan KT, McGlamry ED: Evans calcaneal osteotomy for flexiblepes valgus deformity. Clin Pod Mcd Surg 1:137-751", L987.

5. Evans D: Calcaneo-vaigus deformity. / BoneJoint Surg 57(.8):270-278, 7975.

6. Mosca VS: Calcaneal lengthening for valgus deformity of thehindfoot. J Bone Joint Sutg 77 (A) :500-572, 1995.