Orthopedic Aspects in Diagnosis, Clinical Management and Therapy of CMT Patients R

14 Orthopedic aspects in diagnosis, clinical management and therapy of CMT patients R. Forst, A. Ingenhorst

Introduction

In the clinical routine treatment of CMT patients, the orthopedic surgeon is confronted predominantly with the nearly constant presence of equinocavovarus deformity of the foot. The equinocavovarus deformity requires in many cases a complex operative treatment taking into account the individual pathology. Problems with hand function, scoliosis, hip dysplasia and recurring luxations of the patella require in some cases orthopedic atten- tion [20]. Consistent physio- and/or occupational therapy, assisted by different procedures of physical therapy is recommended to supplement operative treatment. The main goal of conservative rehabilitation is the improvement of muscle strength and hand function, prevention of joint deformities, pro- motion of mobility, prevention of falls, resolution of psychologic problems, as well as prevention and therapy of pain [65]. Rehabilitative concepts specific for CMT are missing in the current literature. Siegel [69] recommends the use of an elastic bandage on the ankle joint to compensate the kineceptive (sensory/proprioceptive) loss due to CMT for improvement of the stance ± and gait confidence. In a case report [21], the positive effect of transcutaneous electric nerve stimulation (TENS) in alleviating muscle atrophy has been described. An improvement of ankle joint stability and function, a reduction of hand and foot fatigue, advancement of grip strength and improvement in activities of daily living were achieved with daily treatment. Due to progressive resistance training of the proximal leg muscles for several weeks, a significant increase of strength similar to healthy persons has been observed. By using a surface EMG and measuring the maximum voluntary isometric contraction, the increase of muscle strength and leg-related functional performance was found to be based initially on neural factors (additional recruitment of motor units), later on the resulting muscle hypertrophy [28, 29]. 14 Orthopedic aspects in diagnosis, clinical management and therapyof CMT patients z 207

14.1 Upper extremities (Fig. 14.1)

CMT is the most common inherited degenerative peripheral neuropathy af- fecting the upper extremities. About one-half to two-thirds of patients show hand symptoms after a mean disease period of 19 years, which typi- cally occur later than the involvement of the lower extremities. The shoulder and elbow function are only affected in the most severe cases. The majority of the patients report motor deficits with loss of muscle strength (50%), loss of dexterity (15.6%), trembling (4.7%), cramping (4.7%) and in 23% sensory changes [38]. When the disorder involves the upper extremities during the disease progress, most of the strength deterioration occurs in the first five to ten years. A relative stable phase with less progression follows. In contrast, the sensibility and dexterity worsen continuously over time. Interestingly, CMT patients are able to adapt and regulate fine motor movements despite the sensory loss: familiar movement patterns can be carried out without significant differences to healthy persons while novel motor patterns are very difficult to perform, especially if visual control is absent [40]. Clinically, mixed median and ulnar nerve palsies (radial nerve is usually not affected) develop and result in a weakness of the intrinsic muscles of the hand with fingerclawing [70] (Fig. 14.1). The failure of the interossei muscles, such as the primary metacarpophalangeal (MCP) flexors, leads to a hyperextension of the MCP joints due to the overload of the extensors. The dominance of the long finger flexors induces a flexion of the interphalangeal joints. Because of the paresis of the interossei muscles, the lateral finger mobility is also lost. Extrinsic muscles, which can be involved at a later time in the disease process, adopt the intrinsic muscle function only at a physiologic joint position. Therefore, the M. extensor digitorum communis becomes an extensor of the interphalangeal joints only if the MCP joints are not hyperextended.

Fig. 14.1. An 8-year old girl with CMT1: severe hand manifestation and atrophy of the intrinsic muscles 208 z R. Forst, A. Ingenhorst

Table 14.1. Surgical treatment of upper limb deformities. APL abductor pollicis longus, EDC extensor digitorum communis, EI extensor indicis, EPB extensor pollicis brevis, EPL extensor pollicis longus, FDS flexor digitorum superficialis indicis, PL palmaris longus [9, 30, 36, 38, 52, 70] Problem Procedure Comment z decreased conduction velo- carpal tunnel release long-term-effect? ± cityof the median nerve progression of the neuro- (carpal tunnel compression) pathy! z lack of opposition opponensplastyusing FDS or different techniques EPB or EI or EDC + EPL z weak pinch MCP1 joint fusion combined with transfer of EPB or APL transfer EI z clawing of the fingers lasso loop operation using flexor digitorum superficialis (FDS) volar plate tenodese transfer of palmaris longus (PL) prolonged with palmar aponeurosis

Because many of the patients compensate the functional loss well, an operative treatment is rarely required. The various possibilities of treatment with orthopedic support devices, e.g., braces, can efficiently facilitate daily and professional activities [38]. Surgical treatment is only useful in excep- tional cases of advanced clawhand deformities with lack of a vigorous grip and thumb-index pinch, as well as thumb opposition. Different operation techniques are described in the actual literature, among them especially the activity improving tendon transfers (Table 14.1). Before an operative intervention, it has to be taken into consideration that the optimal timing and selection of a motor donor unit to transfer is complicated by the impossibility to predict the individual course of the disease. In addition, the effect of increasing the activity of a motor unit by tendon transfers on the progress of disease is not clear. For this reason, the tendon transfer should be performed in a stable phase of the disease defined by minimal progress [38]. In a study by Mackin et al. [30], it is recommended to carry out an EMG examination before tendon transfers in addition to the clinical examination and biomechanical considerations to optimize the selection of do- nor muscles. Interestingly, important differences among partially dener- vated donor muscles have been observed, which could not be detected in the physical examination by experienced clinical examiners. In every case, a postoperative training therapy has to follow to achieve the maximum of function of the transferred muscle [30]. 14 Orthopedic aspects in diagnosis, clinical management and therapyof CMT patients z 209

14.2 Spine

The incidence of scoliosis in CMT patients vacillates between 10% and 50% in older children. A thoracic curvature of the spine and an increased risk for girls has been described and attributed to their more rapid growth compared to boys. CMT1 patients are more frequently involved than patients with type 2, due to the usually earlier onset of the disease and the in most cases more rapidly progressive course of the disease. Scoliosis is also often associated with Djerine-Sottas syndrome (DSS also called CMT3) [61]. The degree of the deformity is normally mild to moderate (according to Daher et al. [11] average 198 Cobb; Walker et al. [67] 65% between 10± 208 Cobb) and an increased kyphosis occurs in 38% of the patients [67]. Usually, the therapeutical management of these spinal deformities is the same as for patients with idiopathic scoliosis. Only in a few cases is dorsal stabilization necessary [6, 11, 67]. The development of compression syndromes caused by hypertrophic nerve roots is described as a possible but rare complication of CMT [49, 53]. In these cases the clinical findings consist in myelo-/radiculopathy, spinal claudication or conus medullaris-, cauda equina symptoms. Hyper- trophy of the lumbosacral intradural nerve root, signal abnormalities and enhancement have been described in MRI, correlating with an increased amount of onion bulbs in sural nerve biopsies [8]. Conservative procedures and operative treatment (laminectomy with duraplasty) are performed. An MRI examination is recommended if CMT patients complain about persis- tent back or spinal pain!

14.3 Hip joint

An association between partially severe hip dysplasias and CMT in older children and adolescents has been observed with an incidence of 10%, in particular in CMT1 [33, 48, 66]. Often initially asymptomatic, the problem remains unrecognized over years. The pathology affects both the femoral and the acetabular component. Different techniques are described for an operative treatment: an isolated varisation osteotomy, an additional Chiari osteotomy, isolated Chiari osteotomy or a primary triple, double or Salter osteotomy [16, 26, 46±48]. To avoid peripheral nerve lesions, the sensitive peripheral sciatic and peroneal nerves of CMT patients have to be pro- tected against pressure and positional damages perioperatively and during casting. According to the results of Kumar et al. [26], two of ten operated children developed a paresis of the ischiatic nerve with only partial recov- ery. Because of these findings it was necessary to treat the foot paresis in one case with a Lambrinudi triple osteotomy, in the other case with a triple osteotomy in combination with a tibialis posterior transfer. 210 z R. Forst, A. Ingenhorst

In addition, there are indications of an increased risk for postoperative avascular necrosis of the femoral heads for unknown reasons. Therefore, reconstructive operations of the hip should only be performed in sympto- matic patients or in cases with radiological proof of progress of the hip dysplasia or subluxation [6]. Because of the considerable therapeutical consequences, Kumar et al. [26] recommend an X-ray screening for all children affected by CMT re- spectively to rule out a CMT in children affected by a dysplastic hip.

14.4 Knee joint

Contrary to our own observations, there is only one publication in the current literature concerning an increased incidence of recurrent luxations of the patella [20]. In particular the changed axis of the leg due to the foot deformity (external rotation of the malleolus) and the necessity for gait stabilization (see below) with spontaneous compensatory adaptation in hip and knee joints (flexion) as well as in the pelvic region (increased antever- sion) can influence patella centralization. An additional cause could be a primary muscular destabilization due to a weakness of the M. quadriceps femoris. Therapy consists both of conservative muscular stabilizing meth- ods as physiotherapy and bandages and also established operative procedures as reconstructive soft tissue techniques or a tuberosity transfer.

14.5 Ankle joint and foot

14.5.1 Clinical basics

A wide intrafamilial variability, which does not allow reliable prediction of the disease process, and a bilateral, but usually asymmetric foot affection is typical for CMT [17]. For the orthopedic surgeon, the type of CMT is less important than the current grade of paresis in the different muscles and the allocation of the sensomotoric changes. A pes cavus or cavovarus can usually be assessed in an early stage of the disease. Often this deformity is the first reason for a medical examination. Etiologically, the cause for the typical pes cavovarus is a dysbalance between intrinsic foot muscles and extrinsic muscles of the lower leg. In contrast, patients having no active muscle strength below the knee, show a flat, but well balanced foot [61]. In CMT, an imbalance exists between important antagonistic muscles with predominance of the posterior tibial over the peroneus brevis and of the peroneus longus over the anterior tibial resulting in a weakness of eversion and dorsiflexion. Com- 14 Orthopedic aspects in diagnosis, clinical management and therapyof CMT patients z 211 pared with other muscles, these deficits are explained by their early involvement in the disease process and functionally by their more distal insertion points. Considering their lower muscle volume, they are also weaker in healthy people. Initially, the deformity is supple, in later stages of the disease soft tissue contractures occur and bone growth contributes to the altered foot position [61]. The fascial structures crossing the cavus deformity thicken and serve as a deforming force, resulting in a continuous worsening of the foot deformity creating a vicious cycle. Consequently, not only the progress of the neurological disease but also the secondary mechanical factors are important. The distal marked paresis often results in the clinical picture called `stork legs' or `inverted champagne bottle legs' [22]. Rarely a planovalgus deformity can occur, especially in the infant period. According to an investigation of Exner [13], all affected children have a delayed start of walking, so that in such constellations the diagnosis of a hereditary neuropathy has to be confirmed and other neuromuscular diseases have to be ruled out before planning operative treatment. In the examination of Ghanem et al. [17], 17% (of 66 examined CMT children) have a pes valgus or planovalgus, which converts spontaneously in approximate half of the cases to a pes cavovarus. The majority of CMT patients have foot and ankle problems. In a study conducted by Birouk et al. [7], a foot deformity was observed in 95% of the examined CMT1A patients (according to Ghanem et al. [17] 96%). An early disease onset is predictive for a rapid progress: 50% of the patients develop already in the first decade, 70% before the second decade a symp- tomatic involvement of the foot [45]. Foot pain, pressure ulcers and development of calluses caused by ill-fitting shoes [42], growing in of toenails, increasing instability (45% [17]), frequent falls, recurrent ankle distorsions, tiptoe gait, decreased strength and conditions with restriction of the maxi- mal and painless walking distance, impossibility of barefoot walking, diffi- culties regarding shoe shopping and a progressive deformity have been re- ported as subjective complaints. Often flexible or rigid clawtoes exist.

14.5.2 Pathogenesis of the deformities

Two different models explaining the pathogenesis of foot deformities exist in the current literature. According to Sabir and Lyttle [55, 56], the muscles supplied by the longest axons of the sciatic nerve are affected first. Muscles above the knee joint are rarely involved. Muscles with small volume be- come weak faster, e.g., the peroneal muscles are involved before the triceps surae is affected. Degeneration follows a centripetal pattern beginning in the intrinsic foot muscles (especially the musculi lumbricales) and later the flexor digitorum longus and brevis, flexor hallucis longus, extensor hallucis longus and brevis, finally the peroneal muscles, extensor hallucis longus and brevis, tibialis posterior and tibialis anterior will be affected. 212 z R. Forst, A. Ingenhorst

Mann and Missirian [32] found in muscle function tests divergent results: a marked weakness of the anterior tibial, peroneus brevis and the intrinsic foot muscles, as well as a good to normal strength of the posterior calf muscles, the peroneus longus and the long foot flexors has been observed. In the development of the paresis, the peroneal and intrinsic muscles, the tibialis anterior, extensor digitorum longus and then all other foot muscles are affected in succession. The specific pattern of paresis leads to the structural deformity, which is characterized by the unopposed action of the peroneus longus (= forefoot equinus with first ray plantarflexion) caused by relative weakness of the anterior tibial and the functional loss of the peroneus brevis which permits the tibialis posterior (= hindfoot varus) to act unopposed. The deformity is enhanced by the progressive contracture of the intrinsic foot muscles and the plantar fascia. The absence of prospective, longitudinal data makes the interpretation of those discrepant results difficult. Perhaps the problem will be solved with the help of techniques examining the recruitment of motor units and the use of imaging

Table 14.2. Pathogenesis of isolated foot-deformities in Charcot-Marie-Tooth disease Deformity Pathogenesis z Pes cavus Unopposed peroneus longus (weak tibialis anterior) causes first ray plantarflexion, forefoot equinus and clinical-cavus and leads to forefoot pronation ± probablyall metatarsales are involved (= global anterior cavus) / an additional contracture of the gastrocnemii a hindfoot equinus Overweight of the tibialis posterior (weak peroneus brevis) with inversion of the subtalar joint Fibrosis and shortening of the short plantar muscles and secondary contracture of the plantar fascia (increase the rigidityof the deformity) z Pes adductus Overpower of the tibialis posterior and long toe-flexors (forefoot adduction is found in the metatarsal joints or in the transverse tarsal joint (talonavicular/calcaneocuboid) z Hindfoot varus Overweight of the tibialis posterior and long toe-flexors As a secondarydeformity:a fixed forefoot pronation (due to the first rayplantarflexion) leads obligatoryto a compensatoryhindfoot varus in stance (tripod effect) and increases the plantar pressure on the lateral border of the foot z Clawtoes Weak musculi lumbricales/interossei with preponderance of the long extensors and flexors lead to MTP extension and IP flexion Deformityworsens in swing phase due to the function of the long toe-extensors as an additional ankle-extensor z Ankle instabilityWeak peroneus brevis Hindfoot varus results in an increased risk for lateral ankle inversion- type injuries 14 Orthopedic aspects in diagnosis, clinical management and therapyof CMT patients z 213 techniques. In comparison to the peroneus brevis, the soleus and gastrocnemii muscles remain stronger for a long time because more motor units exist in cross-section [22]. MRI examinations show a relative increase of the size of the peroneal compartment in comparison to the anterior compartment, which can be interpreted as dominance of the peroneus longus over the anterior tibial muscle. The components which play a role in the pathogenesis of the typical foot deformities are summarized in Table 14.2.

14.5.3 Special diagnostic tests

In gait analysis, a complex disturbance of the gait pattern has been described [32, 56]. The existing foot drop, the muscle weakness, the sensory alterations and a decreased proprioception have to be compensated while walking. Pa- tients do often not show a typical steppage, but a marionette gait. During the swing phase, a pelvic shift and elevation combined with a moderate hip and knee flexion to regulate the foot drop has to be compensated by a lateral bending of the upper trunk to the stance side for balancing. In addition, a hyperextension in the metatarsophalangeal (MTP) joints (at MT1 corre- sponding to the cock-up deformity) and a recruitment of the long extensor muscles supporting the dorsal flexion appear. Due to the foot drop, heel strike is impossible. Different grades of lateral ankle instability with a tendency for inverting the hindfoot have been observed during walking and, in addition, the midfoot and the subtarsal joints were blocked. In differentiated gait pattern analysis, during tiptoe walking an early inversion of the foot and heel, during heel walking a weakness of dorsalflexors and evertors have been observed. The patients walk on the lateral side of the fifth ray and the sole. A deformity per- sisting in stance indicates that secondary structural bone and tendon deformities have developed [61]. At the beginning, it is only visible during active dorsal flexion. Regarding the pathogenesis the ground reaction forces on the loaded foot have to be taken into consideration. The restricted muscular stabilization of the foot skeleton during weight-bearing leads to further deformities, intensified by motion induced thrust and shear forces [12]. The impor- tance of the toe function in walking also has to be pointed out. A reduced contact time of the toes and consequently a diminished area taking load increase the pressure under the metatarsal heads [35]. Additional indications exist for an often detectable weakness of the hip abductor muscles, which causes asymmetric hip moments (= vector sum of forces acting at the joint) and a truncal instability in the mediolateral plane during ambulation [27]. The dynamic pedobarography is an additional diagnostic technique for analyzing mild to moderate foot deformities which is helpful in planning and assessment of therapy. The gait line, contact areas, peak pressures and pressure time integral can be determined. The reliability of this method is limited in severe foot deformities and marked muscular discoordination, and the cause of increased or decreased peak plantar pressure remains still undeterminable [10]. It is impossible to distinguish between flexible and 214 z R. Forst, A. Ingenhorst

Fig. 14.2a, b. Lateral block test: correction of the heel varus demonstrates the flexibilityof the hindfoot

fixed deformities. Metaxiotis et al. [35] examined 15 CMT patients pre- and postoperatively and separated them into three groups: z ªantegrade walkerº with heel-toe pattern (clinically predominant cavus foot), z ªretrograde walkerº with toe-heel pattern (clinically predominant forefoot equinus) and z ªinversion contact patternº with main load under the fifth metatarsal bone (clinically predominant hindfoot varus).

A physiological antegrade heel-toe pattern with increased contact areas could be restored postoperatively by different operative procedures and in a few cases over corrections were detected [35]. The reliability of X-ray diagnosis is also considerably restricted in com- paring pre- and postoperative metric analysis, because as a result of the variability of the foot deformity it is not possible to define a reproducible standardized view. Regardless of these findings in the current literature a lateral radiograph is taken in the weight bearing technique to assess the medial arc, an a.p. projection to assess the forefoot adduction and a posterior projection to assess the heel varus. In the lateral standing radiograph, the calcaneus pitch, instep, MT1-inclination, inferior cortex of calcaneus- MT1, talo-MT1 (Meary's angle), talo-calcaneal, tibio-calcaneal, tibio-talar, first-fifth-MT angles and additionally the height of the longtitudinal arch can be measured. In the lateral radiograph the fibula stands relatively posterior to the tibia, which is related to a rotation of the tibia caused by the hindfoot varus. A calcaneo-cavus is atypical for the CMT disease and therefore the calcaneus pitch angle is below 308. The standing a.p. radiograph allows evaluation of the talo-MT1, talo-MT2, calcaneo-MT1 and the calcaneo-MT2 angles [1±3, 35, 58±59, 61, 69]. 14 Orthopedic aspects in diagnosis, clinical management and therapyof CMT patients z 215

Table 14.3. Subjects of the decision-making process in the management of foot deformities in Charcot-Marie-Tooth disease Problem Strategy ± Consideration z Is CMT responsible Demand for an exact differential diagnosis ± necessaryespecially for the deformity? in young patients with progressive foot deformities before therapy The ªidiopathicº cavus foot is rare and probablythe onlysymptom of a non-classified neurologic disorder. 2/3 pes cavus patients have neurologic problems, 50% of them are CMT disease [2, 61, 69] z Is the deformity Need for a careful examination and analysis of function! fixed or flexible? The typical pes cavovaro-adductus consists of several components: Primaryor ± lateral view: the heel does not touch the floor secondary? ± dorsal: calcaneus inversion, prominence of the lateral malleolus, forefoot adduction ± ventral: forefoot adduction, clawtoes ± medial: cavus and supination of the foot Demand for an isolated inspection of the ankle (flexion/extension), subtalar joint (inversion/eversion), transverse tarsal joint (abduction/adduction), MTP and IP joints. The ªlateral block testº (Cole- man and Chesnut, Fig. 14.2) differentiates a flexible from a fixed hindfoot varus. An equinus deformityis often the result from a forefoot seldom a hindfoot equinus. Clavus develop normallyat the plantar basis of the V. MT and caput ossis metatarsales z What are the Demand for a pre-operative exact clinical examination and deforming forces strength testing to identifypowerful muscles to be transferred and the deficits? and to balance the foot ± no routine tendon transfers! Fixed bony deformities can be themselves deforming forces (1st rayplantarflexion ± hindfoot varus) z Are the clawtoes Fixed toe-deformities require bonyand soft tissue procedures fixed or flexible? z Is the ankle unstable? z What are the Individual conditions of life have to be respected patient's goals?

14.5.4 Therapy

A careful clinical and neurological foot examination with an independent assessment of the fore-, mid- and hindfoot in weight-bearing and non- weight-bearing position, survey of the vascular status, documentation of the plantar callosities, check-up of the integrity of the metatarsal fat pad and radiographs are necessary prior to therapeutical interventions [54, 61]. In some studies, a standardized questionnaire, e.g., Maryland Foot Score (MFS), is used for pre- and postoperative evaluation. Different questions, which have to be taken into consideration before the decision about operative procedures is made, are compiled in Table 14.3 [2, 22, 24, 32]. 216 z R. Forst, A. Ingenhorst

z Conservative therapy High ankle-foot orthoses (below the knee) can be used to compensate the foot drop and prevent the fatigue of the leg muscles in patients with marked ataxia or abnormal position sense [61]. Some authors recommend night-splinting to avoid fixed deformities [17] and extra-deep shoes to compensate clawtoes with support to unload the metatarsal heads. Metatar- salgias can also be soothed by soft bedding and using a surface material for insoles like for diabetic patients. Patients with a plantar-flexed first ray and compensatory flexible hindfoot varus may benefit from lateral support at the forefoot (in shoes or inserts), which pronates the foot and stabilizes the lateral ankle area [2]. Additionally pressure relief below the MT1 head decreases pressure and reduces the longitudinal arch. In advanced cases orthopedic shoes may be useful. In long-term observations, a lack of dur- able prophylaxis of foot deformities by conservative treatment is described as well as the impossibility to correct the basic deformity [22, 58].

z Operative therapy (Fig. 14.3) Because of the variable complexity of the deformity, no standardized thera- peutic algorithm exists [19]. The decision for an operative treatment has to be made considering the following individual factors: age of the patient, flexibility of the deformity, severity and vector of the deforming forces and the sensory status. Dæderlein [12] points out the trias ªcorrect ± stabilize ± balanceº for the treatment of neuromuscular foot deformities. In children the operative goal is, apart from recovering a plantigrade foot position with good function, the prevention of a progress or the development of a fixed deformity. Soft tissue procedures are used isolated or in combination with bony procedures [17]. In flexible foot deformities, an early soft tissue release and tendon transfers are advantageous because the remaining foot deformities are less marked if the operation is performed before skeletal maturity is reached. An early intervention leads not only to the preservation of the normal biomechanics and foot position, but also avoids an even more invasive treatment. On the other hand, it is impossible to correct fixed deformities only with dynamic tendon transfers. The performance of tendon transfers in an imbalanced paresis can lead to unexpected results. A tendon that is transferred will lose one grade in muscle power [58]. Ghanem et al. [17] propose an age-related concept for therapy: avoidance of clawtoe surgery before the age of six; in severe deformities performance of a medial and plantar release combined with an osteotomy before reaching the age of 10, in addition, a tibialis posterior transfer in cases with peroneal muscle atrophy; above the age of 14 indication to tarsectomy under following conditions: experienced surgeon, reducible hindfoot varus, absence of subtalar instability and normal form. Around the age of 40, an atrophy of the plantar fat pad often occurs and consecutively painful calluses develop under 14 Orthopedic aspects in diagnosis, clinical management and therapyof CMT patients z 217

Fig. 14.3a±d. A 25-year old man with CMT1: pre- (a, b) and postoperative (c, d) clinical and radiological findings after correction of a rigid pes cavovaro-adductus byan Imhåuser osteotomy the metatarsal heads. At this stage every kind of an operative correction is no longer optimal. For these cases an individualized shoe- and/or orthosis support should be preferred. The cavus deformity due to CMT is among all cavus feet the most difficult to treat and the most prone to recurrence because of the progressive nature of the muscular imbalance [2]. Generally, an increasing rigid foot deformity requires complex corrective surgery. To ensure optimal patient management, it should be pointed out to the patient preoperatively that perhaps in a later stage of the disease additional operative treatment may be necessary. Results of an operative intervention are difficult to interpret due to the wide spectrum of neurological dysfunctions, the lack of standardized assessment criteria and the number of possible surgical procedures. Regular controls of the disease progress, in at least yearly intervals, are necessary because of the risk of recurrence or deterioration especially during the growth period [12]. An overview of the operative soft tissue and bony procedures for correction of the individual foot deformity is shown in Table 14.4a and b. 218 z R. Forst, A. Ingenhorst

Table 14.4a. Soft tissue procedures to correct foot-deformities in Charcot-Marie-Tooth disease Deformity Procedure Comment z Plantar fascia Plantar (fascia) Usuallyadditional; a compensation in the lateral contracture release block test demonstrates the hindfoot flexibilty± in this case, it is possible to achieve a spontaneous correction of the hindfoot with an isolated correction of the forefoot. Samilson [37] recommend for a fixed varus deformitya radical posteromedial plantar and selectivelya medial tarsal release. In children, Olney[24] corrects a marked proximal cavus using a dome-osteotomycombined with a plantar release (plantar fascia, abductor hallucis, abductor digiti quinti, plantar intrinsic muscles, short and long plantar ligaments) z Reduced ankle- Achilles tendon Often combined with tendon transfers or bony extension lengthening procedures (Achilles tendon Resulting from foot drop and contracture of the tri- shortening) ceps surae due to the muscular imbalance between extensors and flexors z Flexible [22, 35, 61±62, 68] The possibilityof spontaneous correction of flexible clawtoes II±IV clawtoes after midfoot osteotomies has to be considered [2] Hibbs procedure Improves ankle dorsiflexion; sometimes combined (=extensor digit. with interphalangeal (IP) joint fusions long. transfer to 3rd cuneiform) Lengthening of extensors Lengthening of flexors Plantar flexorteno- tomies, dermotomies Dorsal capsulotomy of MTP joints z Flexible Jones procedure Improves ankle dorsiflexion and eliminates its de- clawtoe I (=extensor hallucis forming force in hallux MTP extension deformity longus transfer to 1st MTP neck) Flexor hall. longus lengthening Flexor to extensor transfer 14 Orthopedic aspects in diagnosis, clinical management and therapyof CMT patients z 219

Table 14.4a (contiuned) Deformity Procedure Comment z Flexible pes Peroneus longus Strengthens eversion and eliminates 1st rayplantar- cavovaro- to brevis transfer flexing force; rare indication for transfer of peroneus adductus longus to achilles tendon Tibialis posterior Strengthens ankle dorsiflexion, reduces cavusprodu- transfer cing vector, stabilizes hindfoot. Best effect in early stages of the deformity[37, 72]; seldom indication for a split transfer [15, 35] Tibialis anterior Not advisable due to a greater involvement of the transfer muscle and the disease progress

Table 14.4b. Bonyprocedures to correct foot-deformities in Charcot-Marie-Tooth disease Deformity Procedure Comment z Fixed clawtoes Interphalangeal Arthrodesis of the Vth toe has to be avoided due to fusion (PIP joint) the risk of pressure problems in unyielding shoes [14] Fusion of the great toe with 2 crossing Kirschner wires or one screw [5], in some cases combined with metatarsophalangeal capsulotomies and extensor tendon lengthening, in marked deformities of young patients with flexor to extensor transfer, can be combined also with the Jones procedure [62] Hohmann procedure Decreases pressure under metatarsal heads [35] (toe II±V) Helal procedure (toe II±V) z Fixed hindfoot Dwyer (lateral No influence of the deforming pathology; enlarges varus (child- closing wedge) contact area hood) calcaneal osteotomy Used to correct skeletallyimmature patients as young as 7 years old without influence on heel growth and sometimes with amelioration of the cavus deformity. Children younger than 10 years with mild deformities should be operated without wedge resection, in older children or in marked deformities a lateral closing wedge osteotomywould be useful. Skeletallymatured patients with pes cavovaro-adductus should be treated with a dorsal wedge intertarsal osteotomyand a Dwyerprocedure [61±62] Siegel [63] combines a modified Dwyer osteotomy with a Mitchell procedure (plantar fasciotomywith proximal displacement of calcaneal osteotomy) in order to lengthen the heel and facilitate the fitting for a shoe or brace. Gould [18] adds proximal dorsal closing wedge metatarsal osteotomies 220 z R. Forst, A. Ingenhorst

Table 14.4b (continued) Deformity Procedure Comment Superolateral sliding No disadvantages in midtarsal or tarsometatarsal calcaneal osteotomy function, it is combined with a metatarsal dorsolat- eral closing wedge osteotomy(alwaysMT1, option- allyother metatarsalia) and a plantar release. Advantages: full joint mobilityand flexibility,full shock absorbing function. A non-union, delayed union and degenerative intertarsal joint diseases postoperativelywere rarelyfound [59] z Fixed metatar- Metatarsal (Of the MT1 alone or of all metatarsalia); corrects a sus adductus osteotomies: metatarsus adductus or a rigid forefoot equinus [5, (fixed mild pes Proximal dorsal 18, 35, 61±62]; at toe II±V without fixation (plantar cavovaro- closing wedge continuity), the osteotomy of toe I will be performed adductus) greenstick at last and stabilized with a screw. It has to be metatarsal considered that this procedure does not reach the osteotomies deformitycenter and is able to increase the pressure on the head of the 2nd MT. Risk: overcorrection (forefoot ªrockerbottomº) and painful callosities Dorsal wedge Osteotomyconcerning the tarsometatarsal joints, osteotomy Jahss removes more bone from the 2nd and 3rd me- (Jahss procedure) tatarsal bases than from the 1st metatarsocunei- form, 4th- and 5th- tarsometatarsal joint. The bone wedges are obtained proximal to painful callus and should be taken from painful, stiff, arthritic, unstable or functionless joints [24]. Risk: overcorrection with abduction malposition and forefoot ªrockerbottomº [58]. Additional disadvantage: loss of motion and shock absorbing effect of the metatarsal-cuneiform-cuboid complex [59] z Fixed pes Midfoot (mid-tarsal) Disadvantage of all mid-tarsal osteotomies: they cavovaro- osteotomies: span the navicular-cuneiform-cuboid complex and adductus reduce the midtarsal joint motion [59]. In mild de- (adult) formities, a plantar-based opening wedge osteo- tomyof the medial cuneiform without the need for an internal fixation maybe combined with the shortening of the lateral column or procedures of the medial column ± advantage of this procedure: full motion of the subtalar joint [39] Dorsal wedge Removal of a dorsallyand slightlylaterallybased intertarsal wedge (proximal cut through naviculare and cu- osteotomy boid, distal cut through cuboid and the cuneifor- mia); corrects a mild or moderate cavus and adductus deformity[62] 14 Orthopedic aspects in diagnosis, clinical management and therapyof CMT patients z 221

Table 14.4b (continued) Deformity Procedure Comment Imhåuser Possibilityof a total correction of all deformitycom- osteotomy ponents: dorsallyand laterallybased wedge resection of the Chopart joint, in marked cases an entire navicular resection has to be done; the procedure leads to an elevation of the forefoot, reduces the cavus and corrects the forefoot adduction. In most cases the clawtoes straighten themselves spontaneously, sometimes postoperatively patients are able to wear ready-made shoes; additional tendon transfers should be useful (tibialis posterior, peroneus longus) [23] Other mid-tarsal ± Steindler: dorsallybased osteotomyincluding the osteotomies talar neck combined with a plantar release (Steindler, Cole, ± Cole: anterior tarsal wedge osteotomy(great risk Wilcox, Japas) (30%) of pseudarthrosis and earlyarthropathy) ± Wilcox: midtarsal dome-osteotomy ± Japas: V-shaped-osteotomy, corrects nearly the apex of the deformity z Severe pes Triple arthrodesis Salvage procedure! Reserved for older patients cavovaro- (fusion of the Long-term outcome: often deteriorates with time adductus talonavicular-, due to the development of late-onset complications. (adult) subtalar-, calcaneo- In recent studies, the average age at surgerywas 12± cuboid joint; e.g. 19 years [31, 41, 58]. Often, other procedures were Ryerson, performed before without total correction and Lambrinudi) sometimes soft tissue procedures were added to a triple arthrodesis before or afterwards. Most sur- geons use this method in advanced, rigid and ma- tured cavovarus. A discrepancybetween the patient satisfaction and the objective assessment in long- term follow-ups has been described [4, 22, 41]. In- dependentlyof the chosen method, in the follow-up >10±20 years the operation may lead to the development of late-onset lesions [4, 60, 71]. In several studies, the postoperative result was classified bythe surgeon as fair or poor in 28±47% [4, 41, 68] The problem is usuallyfunctional impairment and the necessityfor postoperative bracing [62]. A high incidence of degenerative changes in the ankle and midfoot (up to 100% 44 years postoperatively [57]), pseudarthrosis (up to 23% [4]) or delayed fusions, avascular necrosis of the talus and residual deformities (up to 62% [4]) with need for revision (8% [31]), neuropathic ankle [34, 68], instability, pain and callosities were described. A veryrigid equinovarus preoperativelyleads to the worst results. A risk of under- or overcorrection (up to 60% [71]) and foot 222 z R. Forst, A. Ingenhorst

Table 14.4b (continued) Deformity Procedure Comment shortening [18, 58] was found. Patients with painful pseudarthrosis, recurrent or residual deformities re- ceived additional foot or ankle joint fusions. The good result of the studyof Saltzman et al. 1999 was explained with the inhomogeneityof the patient collective (high percentage (55%) of polio patients with a stabile foot situation, muscle balance and lack of progression and sensorylesions, not comparable to CMT). The reduced tarsal joint motion increased bythe progressive loss of proprioception and balance stresses the ankle and leads to osteoarthritic changes and ligamental laxity External fixators Raikin 2002 recommends the avoidance of exces- sive bonyor wedge resection and the use of rigid internal fixation to diminish the pseudarthrosis and deformityrecurrence rate. Alternative procedures like the Imhåuser osteotomypermit a more flexible plantigrade foot position and treat the main apex of the deformity There is a need for a preventive therapeutical strat- egywith earlysoft tissue procedures and probably bracing to avoid triple arthrodesis; this implies continuous patient care in order to detect deformities prior to need for treatment Volkov-Oganesyan-Povarov hinged distraction apparatus: corrects 3-dimensionallya severe equinocavovarus deformityin an average distraction time of 3±13 weeks depending on the rigidityand severity of the deformity, secondary changes in the joints and soft tissue and patient tolerance. In cases with reduced or absent ankle motion, an additional ankle compression can be used for a non-invasive fusion. Advantages: slowlyand gradual distraction of foot capsules and ligaments, avoidance of an open procedure and of wedge resection with mainte- nance of the original foot length. Disadvantages: long therapyduration, risk of pin track infection, osteomyelitis with precocious apparatus removal, skin problems, reduction of ankle motion, reduced success rate in CMT due to the disease progression, difficult technique [43, 44] Ilizarov method: combined with V-shaped osteotomy, sometimes with additional procedures; advantages: obtainment of a stable, plantigrade painless foot, correction of all deformitycompo- nents; disadvantages: pin tract problems, skin necrosis with residual deformity, toe contractures, technicallydifficult [25] 14 Orthopedic aspects in diagnosis, clinical management and therapyof CMT patients z 223

14.6 Fractures

In the present literature, no systematic studies exist about the incidence and therapy of fractures in CMT. It has to be presumed that in advanced disease stages with considerable restriction of the mobility an osteoporosis caused by inactivity occurs, leading to an increased risk of fractures. In a case report Quintart et al. [50] described a pathologic tibia fracture of a CMT patient. On the X-rays a narrowing of the shaft with thinning of the cortex, rarefaction at the end of long bones and a relative widening of the medullary cavity were observed. The muscular atrophy was made responsible for these radiographic bony changes. It is important to consider that consolidation of fractures require approximately the same time as in healthy individuals and that the fracture should be immobilized as short as possible, just as in other patients with neuromuscular disease.

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