Type I HMSN is the classic and most common presentation of CMT disease; up to two thirds of these patients have a cavus foot by adulthood. The most common pattern of inheritance is autosomal dominant, although autosomal recessive forms have also been reported.⁴⁵ The disease is characterized by slow nerve conduction velocities, and it usually presents during the second decade of life. Genetic research has shown that the disease group demonstrates wide genetic heterogeneity, with 29 genes and more than 30 loci involved. Specific genetic sequences have been associated with a subset of type I patients, further defining this spectrum of disorders with future implications, not only diagnostic and prognostic but also potentially therapeutic.²³ The majority of type I presentations have been linked to chromosome 17 and are designated CMT-1A.⁸⁵ The most common abnormality identified on chromosome 17 is a duplication of a part of the PMP22 gene, but other variants have been identified. Type II HMSN has a similar presentation but is less pronounced and usually appears later in life. In type II, the rate of impulse transfer is normal, but the magnitude of the impulse is decreased, as manifested by the loss of sensory- and motor nerve–evoked response amplitudes. Nerve conduction velocities are seldom slowed and, if so, only mildly.⁶

The most common lower extremity presentation is bilateral pes cavovarus deformities with leg weakness (Fig. 34-1). Because a majority of these are autosomal dominant diseases, they occur as a familial disorder. Despite this, the variability within families can be so great that individual family members can become symptomatic earlier or later and show significant disparity in the amount of disability secondary to the disorder. In addition to the common presentation of the bilateral pes cavus, the orthopaedist must be aware of progressive weakness in the upper extremities, which usually occurs later than the foot findings. In general, CMT disease affects the longest nerves to the smallest muscles first, hence the symptomatic presentation of feet before hands. Hip dysplasia and scoliosis also are significant presentations in this diagnosis.³³ Patients have a variety of complaints, including metatarsalgia, claw toes, tarsal prominence, and recurrent ankle sprains.^2,60

Figure 34-1 Foot and ankle images of a patient with Charcot-Marie-Tooth disease demonstrating peek-a-boo heel, consistent with hindfoot varus, a plantar-flexed first ray, and clawing of the lesser toes. Note the significant leg musculature wasting.

The cavovarus presentation is the result of motor imbalance between pairs of muscles around the foot and ankle ¹²¹ (Fig. 34-2). A common early finding is significant weakness of the tibialis anterior and peroneus brevis muscles.^90,151 As a result of tibialis anterior weakness, the first ray is plantar flexed by the stronger peroneus longus, creating a relative forefoot valgus. Compensation for this on weight bearing, considering the foot as a tripod, is a compensatory hindfoot varus. This hindfoot varus is further exaggerated by the unopposed pull of the posterior tibialis muscle against the weakened peroneus brevis. Factoring in intrinsic wasting that causes an intrinsic minus deformity at the metatarsophalangeal (MTP) and interphalangeal (IP) joints, the clinician sees the clinical presentation of hindfoot varus, to midfoot cavus and forefoot valgus, to clawing of the toes. Attempts by the extensor hallucis longus and digitorum longus muscles to dorsiflex the foot further exacerbate toe clawing.^60,90

Figure 34-2 Computer tomography reconstruction of a patient with Charcot-Marie-Tooth disease demonstrating a severely plantar-flexed first ray consistent with overpull of the peroneus longus relative to the tibialis anterior.

Although determining the pattern of muscle weakness is important to understanding the basic deformity of the cavovarus foot and for considering treatment alternatives, an equally important factor to remember is that CMT is also a sensory neuropathy. The early sensory changes can be subtle, primarily with loss of proprioceptive and vibratory sense. As with the different presentations of motor weakness, however, sensory presentations can vary greatly. Patients are less inclined to recognize or acknowledge the diminished sensation, but this loss limits their ability to balance properly.

As with all other neuromuscular conditions leading to some level of diminished sensation of the foot and ankle, education is a primary concern. Patients must be taught to examine their feet carefully once they have significantly diminished sensation and must consistently protect their feet with appropriate footwear (Fig. 34-3). Severe deformities and fusions are potentially problematic in the sensory-impaired foot and ankle.⁹⁴

Figure 34-3 Plantar view of a patient with Charcot-Marie-Tooth disease and associated sensory neuropathy with lateral midfoot ulceration secondary to lack of protective sensation and mechanical overload.

A thorough neurologic evaluation of these patients is essential, starting with a careful motor examination. Weakness of the anterior tibialis and peroneus brevis muscles is commonly observed, but each muscle of the leg must be assessed as the relative strengths determine the options for management. The original descriptions of CMT emphasized the asymmetry that is commonly observed clinically. The sensory impairment appears later and is usually not as severe. Up to 25% of patients do have significant sensory impairment.¹⁴⁰ Vibration, two-point discrimination, and proprioception are the first factors to be affected.

In the patient with a cavovarus foot, standing examination clearly shows the relative hindfoot varus, atrophy of the medial longitudinal arch, tarsal bossing, and some degree of toe clawing. In addition, the patient’s legs show significant atrophy below the knee (Fig. 34-4). On the seated biomechanical examination, reduction of the foot into a neutral subtalar position allows the examiner to observe a relatively flexible hindfoot, indicating that the hindfoot varus is compensatory for a fixed forefoot valgus. The primary deformity of the forefoot is a plantar-flexed first ray, but over time, the second and third rays may be similarly depressed in relation to the foot’s lateral border. In the long-standing deformity, because of the relative parallelism between the long axis of the talus and the calcaneus (the varus position of the hindfoot is a result of the medial rotation of the calcaneus beneath the talus), limited dorsiflexion is present because of an abutment of the talar neck against the anterior tibia (Fig. 34-5). The examiner must be sure to evaluate the motion of the talonavicular joint to determine if there is a mechanical block to abduction or a palpable prominence on the lateral aspect of the talar neck that precludes reduction of the midfoot to the hindfoot. When the patient is asked to ambulate, a combination of dorsiflexion weakness, fixed equinus, and difficulties with proprioception give a characteristic steppage gait.

Figure 34-4 Lower extremity coronal image of a patient with Charcot-Marie-Tooth type 1A with apparent bilateral cavovarus foot shape, apparent anterior tibial and peroneal atrophy, and clawing of the toes.

Figure 34-5 Lateral radiographs before (top) and after (bottom) medial column dorsiflexion osteotomy. With dorsiflexion, ankle or talonavicular, abutment can occur.

The Coleman block test remains the fundamental tool of clinical assessment of the patient with a cavus foot deformity. This classic test described by Coleman and Chestnut ²⁸ is useful in examining these patients clinically (Fig. 34-6). The block test is performed by supporting the heel and the foot’s lateral border with a block but allowing the first ray to drop over the edge of the block, and the relative flexibility of the hindfoot is then evaluated. If the hindfoot corrects to neutral or slight valgus, the implication is a compensatory (i.e., “forefoot driven”) hindfoot varus, and that dorsiflexion of the plantar-flexed first ray will correct the hindfoot deformity. If the heel moves only slightly or fails to move at all, the hindfoot deformity is fixed and must be addressed directly, which usually demands a calcaneal osteotomy or hindfoot fusion procedure. This relative hindfoot rigidity, however, is not necessarily the end stage of an algorithm requiring triple arthrodesis.

Figure 34-6 Viewed from the posterior, a foot upon a Coleman block, with the heel and lateral forefoot supported and resultant hindfoot valgus, is observed after allowing the first ray to plantar flex relative to the lateral forefoot.

Treatment Approach

Treatment begins with an accurate diagnosis, and in early stages, this might only require observation. Physical therapy has a limited role, but occasionally, in a young child with early loss of motion, range can be improved with aggressive therapy. Objective support for physical therapy has been reported in patients with CMT.¹²² Orthotic management and shoe modification do have a role in the treatment of CMT disease and the cavovarus foot. In the foot with significant early involvement, an orthotic device may be used to hold the foot in a more normal position by allowing for plantar flexion of the first ray, with relative posting of the lateral forefoot. An additional lateral heel wedge can also be effective. Ankle–foot orthoses can be used to support the more involved leg and foot deformity, and many adult patients tolerate this for years. However, it is important to note that this may be only a temporary measure because the neuropathy and corresponding deformity will likely continue to progress.

Orthotic devices have a role in the adult patient who has substantial paralysis of the foot or significant footdrop. Orthoses may be used to accommodate foot deformity, protect the insensate foot, and to reduce some of the energy expenditure of a steppage gait. Orthoses can be used to some degree to prevent or delay deformity but cannot be used to correct rigid deformity. Severe and rigid deformities often make the use of an orthosis untenable, and surgery may be considered with the goal of creating a foot shape that allows an orthosis to be used to support ambulation.

Radiographic assessment is important in preoperative planning (Fig. 34-7). A series of weight-bearing radiographs should be taken of both feet and ankles. Because of the severity of many of these deformities, particularly midfoot adductus, obtaining a good lateral view of the foot can be difficult. To obtain a true talar lateral view and a good assessment of the hindfoot, the axis of the medial and lateral malleoli should be parallel to the x-ray beam. This, however, makes the midfoot and forefoot difficult to assess, so a second lateral view may be necessary to for a true lateral view of the forefoot. Studies of the ankle are important, particularly in long-standing severe varus hindfoot, in which case, the lateral ligamentous structures may be compromised. Finally, because this is a sensory neuropathy, radiographic images are useful in the evaluation of possible Charcot neuroarthropathy changes in the foot and ankle.

Figure 34-7 Lateral radiograph of a juvenile patient with Charcot-Marie-Tooth disease demonstrating a severely plantar-flexed first metatarsal and oblique ankle, resulting from midfoot adduction relative to hindfoot.

Surgical Treatment

Considerations for surgical treatment in these patients can be complex.5,24,27,58,66,83,143 The patient’s goals, expectations, and demands are the primary concern. Young persons who wear high-top athletic shoes that provide some ankle support and have a large toe box that accommodates clawing of the toes might not require much more than this.

In the patient who is considered a surgical candidate, the following three questions are important:

n. What is the motor status of each muscle around the foot and ankle?

n. Are the deformities fixed or flexible in terms of joint motion?

n. What degree of sensory impairment is present?

Plantar Fascia Release

Complete plantar fascia release of the cavus foot is seldom performed in isolation but is commonly performed as an initial step during soft tissue and bone reconstruction in patients with CMT.51,70,119,142 In the earliest presentation of mild flexible cavus, the plantar fascia should not be released. The question arises: Can early soft tissue procedures (complete plantar fascia release) combined with tendon transfers (transfer of the peroneus longus to the lateral portion of the foot) alter the pathologic modeling of the immature foot? Are bony abnormalities observed in patients with CMT genetically driven or only the result of neuromotor imbalance?

Surgical Technique (Video Clip 47)

1. The plantar fascia is approached through a medial skin incision approximately 3 cm long at the junction between the plantar and medial skin, beginning at approximately the level of the medial tuberosity and extending distally.

2. Sharp dissection is done down to the abductor hallucis muscle. The plantar fascia is easily palpable by using a blunt Mayo scissor, and the tissue above and below the fascia is dissected off the fascia. In long-standing disease, the abductor muscle may show signs of significant atrophy and fibrosis.

3. Once the muscle is retracted, the thickened lateral fascia of the abductor halluces is encountered, which blends plantarly into the plantar fascia and intrinsic musculature. The leading edge of this fascia is found cephalad and carefully transected. A Freer elevator is placed behind this to protect the lateral plantar nerve, which is often visible during this approach. Care must be taken throughout this procedure to avoid manipulation of the nerve.

4. When the abductor fascia is out of the way, the lateral plantar nerve can be seen crossing over to the lateral portion of the foot with a somewhat distal trajectory. The intrinsic musculature and plantar fascia should be clearly visualized and then can be sharply divided.

5. Because this is seldom done as an isolated procedure and is often combined with a calcaneal osteotomy, it is important to ensure that the plantar fascia is completely released so that the tuberosity can easily be mobilized during deformity correction.

Lateralizing Calcaneal Tuberosity Osteotomy

This procedure is performed to correct hindfoot varus alignment. If the Coleman block test shows some degree of correction but does not allow the hindfoot to correct to slight valgus, or if physical examination reveals well-preserved subtalar motion, a lateralizing calcaneal osteotomy is indicated 51,123,124 (Fig. 34-8). Ankle instability may also be present in patients with long-standing deformities and can be confused with subtalar motion. Preoperative standing radiographs of the ankle are important in addition to a careful examination.

Figure 34-8 A, Calcaneal slide osteotomy. The skin incision is performed halfway between the Achilles tendon and the palpable peroneal tendons. Sharp dissection is performed down to the calcaneus, with care taken to protect the sural nerve. B, Orientation of the calcaneal osteotomy is generally 45 degrees to the plane of the floor. By decreasing this angle, more length can be obtained on the calcaneus, if necessary. The tuberosity fragment is moved laterally to bring the weight-bearing force slightly medial to the midpoint of the calcaneal tuberosity, correcting any varus inclination. Moving the tuberosity cephalad helps decrease the calcaneal pitch, decreasing the cavus component. In patients with a severe varus hindfoot, it is often necessary to perform an additional Dwyer closing-wedge osteotomy.

Surgical Technique

1. A curvilinear incision is made beginning 1 cm above the palpable calcaneal tuberosity between the Achilles tendon and the peroneal tendons. This curves down and ends at the junction between the lateral skin and plantar skin at the level of the peroneal sulcus.

2. Sharp dissection is performed straight down to bone because the skin incision is away from the major trunk of the sural nerve and the peroneal tendons.

3. A curved retractor is placed over the top of the tuberosity and another under the calcaneus. An oblique osteotomy is performed perpendicular to the lateral face of the calcaneus from the midportion of the tuberosity to approximately 1 cm past the weight-bearing portion of the calcaneus plantarly (Fig. 34-9).

Figure 34-9 Intraoperative photograph taken immediately after the osteotomy of the calcaneus but before it is shifted laterally out of varus.

4. The primary displacement of the tuberosity fragment is laterally into a valgus position. The midaxis of the tibia should fall just to the medial side of the midpoint of the calcaneal tuberosity.

5. The calcaneus may be shifted slightly cephalad (i.e., more vertical) to diminish the calcaneal pitch. Care must be taken not to shift this too far, or impingement of the neck of the talus into the anterior lip of the tibia will result.

6. By changing the obliquity of the osteotomy from more vertical to horizontal, more or less length can be obtained from the calcaneus as necessary, as opposed to more correction of the calcaneal pitch with the more vertical cut.

7. At times, the varus deformity is severe enough that it is necessary to remove a secondary wedge (Dwyer osteotomy)⁴³ (Fig. 34-10). This wedge is generally 1 cm wide laterally, tapering to emerge at the medial cortex, coincident with the first cut. The wedge is usually taken off the distal fragment of the calcaneus.

Figure 34-10 Dwyer calcaneal osteotomy. A, Skin incision is made halfway between the palpable Achilles tendon and the peroneal tendons, after the sweep of the peroneal tendons. The sural nerve must be identified and protected. B, Two oblique osteotomies are carried out as closing-wedge procedures. The base of the closing wedge increases to correct the increasing varus deformity. C, The wedge is removed, the osteotomy site is closed, and internal fixation is accomplished.

8. Fixation is accomplished with one or two screws inserted just off the heel pad posteriorly. Attempts should be made to keep the shaft–screw interface as far from the osteotomy as possible because this is the most common site of hardware failure. Both lateral and axial fluoroscopic image can be useful to confirm screw position.

9. In cases where a more significant deformity is addressed, a multiplanar osteotomy (“Malerba” type) may be used. This Z-shaped osteotomy has the potential advantage of allowing for translation, angulation, and rotation (Fig. 34-11).

Figure 34-11 Intraoperative lateral fluoroscopic image demonstrating Z-shaped osteotomy with internal fixation in a patient with cavovarus foot correction surgery.

Metatarsal Osteotomy (Video Clip 118)

When the hindfoot corrects completely to slight valgus with the Coleman block test and the medial ray is fixed in plantar flexion, a medial column dorsiflexion osteotomy is indicated 24,27,155 (Fig. 34-12). Careful examination of the forefoot will reveal whether this deformity is limited to a plantar-flexed first ray, or if the second and sometimes the third rays are also involved. When only the first metatarsal is plantar flexed, a dorsal closing-wedge osteotomy of the medial cuneiform can be performed. In general, the osteotomy should be located at the apex of the midfoot as seen on the standing lateral radiograph. In some presentations, a dorsal closing-wedge osteotomy across the midfoot (navicular/cuneiforms/cuboid) is necessary. If there is an adductus component, this can require a biplanar osteotomy (dorsal–lateral). It should be noted that the reliability of achieving bony compression is greatest for the first metatarsal osteotomy, so one must consider whether the quality of the bone to be compressed will allow adequate fixation if a cuneiform or other osteotomy is contemplated.

Figure 34-12 First metatarsal closing-wedge osteotomy is appropriately sized. The surgeon must be careful not to cut through the plantar cortex to help maintain stability. Rigid internal fixation is used.

Surgical Technique

1. The proximal first metatarsal is isolated through a medial incision. In the skeletally immature foot, the proximal location of the first metatarsal growth plate must be identified and protected. The anterior tibial tendon must also be protected.

2. A dorsal closing-wedge osteotomy is most useful. Care is taken to maintain the plantar cortex. The first ray is dorsiflexed, and the overall alignment is assessed.

3. Fixation is generally with a smooth pin in the skeletally immature patient and with a distal-to-proximal screw or dorsal-medial plate in the skeletally mature patient.

4. An alternative method for stabilization is to approach the base of the first metatarsal dorsally and perform a closing-wedge osteotomy from the top. This can be stabilized with a tension band wire placed around a post created with a 2.4-mm screw adjacent to the metatarsocuneiform articulation. A 22-gauge wire is sufficient (Fig. 34-13).

Figure 34-13 Anteroposterior (top) and lateral (bottom) fluoroscopic images of dorsal closing-wedge osteotomy of the first metatarsal with tension band fixation technique.

5. Careful assessment is then made of the second and third metatarsals. If further deformity correction is required, an incision is made between the proximal half of the second and third metatarsals. The proximal portion of the second metatarsal is exposed subperiosteally, and a long oblique osteotomy is performed. Then the distal portion of the second metatarsal is allowed to float into its corrected position. A small amount of cancellous bone graft obtained from the calcaneus can be used to enhance bone healing around the first and second metatarsal osteotomies.

6. The dorsal closing-wedge osteotomy of the medial cuneiform is performed through a slightly more proximal incision. The tibialis anterior will be crossing over a portion of the cuneiform and must be protected. The first osteotomy is parallel to the distal articular surface of the cuneiform at about the distal two thirds. Make the second cut, creating and removing the appropriate-size wedge. Dorsiflex the first ray and use internal fixation. Remember that the medial cuneiform is wedge shaped and narrower at the base.

Peroneus Longus Tendon Transfer

In general, the peroneus longus tendon maintains its strength well into the disease process. It is a primary deforming force and therefore an excellent choice for tendon transfer, which removes a deforming force while providing a useful and functional motor for transfer.2,60,7 Specifically, the goal is to oppose adduction by the posterior tibialis tendon and/or to aid in dorsiflexion of the foot.¹³⁹ The latter is accomplished by tendon transfer around the fibula into the cuboid and the former by tenodesis to the peroneus brevis tendon.

Surgical Technique (Video Clip 49)

1. The incision for the calcaneal slide osteotomy is extended to the base of the fifth metatarsal, staying dorsal to the plantar skin.

2. The abductor digiti quinti muscle is encountered first and retracted. The peroneus brevis tendon is identified and retracted, and the peroneus longus tendon is found deep to it against the groove in the cuboid.

3. The peroneus longus tendon is brought into the wound’s more superficial aspect with a right-angled instrument, the transection site is selected, and a suture is placed just distal to this and tied into the insertion of the peroneus brevis.

4. An incision is made approximately 10 cm proximal to the tip of the lateral malleolus just behind the fibula, with sharp dissection down through the skin and subcutaneous tissues. The peroneal sheath is opened. A slight tug on the peroneus longus distally identifies the tendon proximally. The tendon is then brought into the proximal wound.

5. An incision is made over the cuboid in line with the fourth metatarsal, and the peroneus longus tendon is transferred subcutaneously to this level.

6. The transferred tendon is secured using soft tissue anchors and heavy absorbable suture.

7. An alternative peroneus longus transfer is to the peroneus brevis tendon. Tenodesis can be accomplished over the last 3 to 4 cm of the peroneus brevis before its insertion into the fifth metatarsal. If a fixed adductus deformity exists, however, a medial release or midfoot osteotomies must be considered.

Posterior Tibial Tendon Transfer

After the triceps surae musculature, which almost always maintains some strength, the posterior tibial tendon is the second strongest motor around the foot and ankle. Therefore it is usually a late deforming force and a motor with enough residual power to be considered for transfer. The posterior tibial tendon is transferred through the interosseous membrane (Fig. 34-14) in patients with a foot that is essentially paralyzed except for the posterior tibial tendon tendon and the triceps surae. A lengthening of the triceps surae may be necessary if an equinus contracture is present, but in the absence of equinus or if a calcaneocavus deformity is present, lengthening is typically not necessary.

Figure 34-14 Medial approach to the left foot. The tibialis posterior tendon is transferred through the interosseous membrane. A, The medial malleolus is to the left, and toes are to right. The superior hemostat is holding the tibialis posterior, which has been released from the navicular and its plantar attachments. B, The view in this photograph is from the medial aspect. The tibialis posterior tendon is brought up through this proximal medial incision, awaiting transfer posterior to the tibia through the interosseous membrane. Note the oval of cartilage at the end of the tibialis posterior tendon. This is a portion of the navicular on this skeletally immature patient; it was later debrided before the tendon was implanted into the midfoot. C, The view in this photograph is from the medial aspect. The retractor is resting on the interosseous membrane. A window has been created in the interosseous membrane. D, The view in this photograph is from the medial aspect. The tendon is passed directly posterior to the tibia through this opening. E, The view in this photograph is from the lateral aspect. The tibialis posterior tendon is brought subcutaneously down to an incision over the cuboid in line with the fourth metatarsal. The cuboid insertion site is prepared by raising a periosteal flap, which is then sewn over the tendon after it has been fixed to the bone. Note the outline of the tendon as it passes from the proximal anterior incision across the ankle to the distal incision over the cuboid.

When dealing with the posterior tibial tendon as a deforming force in the presence of significant midfoot adductus, the flexible deformity may be corrected with a medial release and transfer of the peroneus longus to the peroneus brevis tendon. In the fixed deformity, correction of the metatarsus adductus may require midfoot osteotomies (Fig. 34-15).

Figure 34-15 Clinical photograph of a patient who has undergone left cavovarus foot reconstruction with calcaneal and metatarsal osteotomies and posterior tibial tendon transfer for cavovarus foot deformity secondary to Charcot-Marie-Tooth disease. The right foot is untreated so far.

Surgical Technique

1. A short medial incision is made over the talonavicular joint. The posterior tibial tendon is identified and sharply excised from the navicular and cuneiform, obtaining as much length as possible.

2. Another short incision is made approximately 10 cm above the medial malleolus just behind the tibia. The posterior tibial tendon is readily identified proximally and then brought into this wound. The flexor digitalis longus (FDL) tendon is typically the first tendon visualized through this incision.

3. At the same level, approximately 10 to 12 cm above the ankle, a straight anterior incision is made just lateral to the crest of the tibia. The anterior compartment along with the neurovascular bundle is then retracted laterally. The interosseous membrane is then identified between the fibula and tibia.

4. A window approximately 3 cm wide is made in the interosseous membrane. An instrument is then passed through the interosseous membrane, remaining on the tibial cortex, transferring the posterior tibial tendon deep to all other structures and through the window.

5. The tendon is then passed subcutaneously or subretinacularly down to the level of the cuboid and anchored using a soft tissue anchor and absorbable suture. Alternatively, the tendon can be fixed with a tenodesis screw if there is sufficient length. The tendon may be also sutured to the peroneus tertius.

Modified Jones Procedure

Correction of clawing of the great toe with transfer of the extensor hallucis longus (EHL) tendon is often indicated for the symptomatic deformity. This also improves the role of the EHL as an ankle dorsiflexor.151,70

Surgical Technique (Video Clip 57)

1. A midline incision is made over the dorsum, exposing the MTP and IP joints of the hallux. With the EHL tendon protected, cartilage is removed at the IP joint and fixed with a single screw from distal to proximal (Fig 34-16).

Figure 34-16 First toe Jones procedure moves pull of extensor hallucis longus tendon from the great toe into the neck of the first metatarsal. Interphalangeal joint arthrodesis of the hallux is performed. This procedure results in elevation of first metatarsal and thus eliminates the cock-up deformity of the first metatarsophalangeal joint.

2. The EHL tendon is then transected, leaving enough tendon to allow tenodesis of the MTP joint in a neutral position.

3. The EHL tendon is then tenodesed into the distal portion of the first metatarsal through a drill hole, with the foot held in a neutral position at the ankle to apply appropriate tension (see the technique for the Jones procedure in Chapter 26).

Correction of Lesser Toes

If the extensor digitorum communis tendon is a deforming force acting to dorsiflex the foot, it could be tenodesed to the dorsum of the foot, again making sure that appropriate tension is achieved.24,103 If the toe deformities are flexible, a Girdlestone-Taylor¹⁴⁸ transfer may be performed. If significant clawing is present, an MTP capsulotomy transecting the collateral ligaments will be necessary to achieve realignment. If the deformities are fixed, a Girdlestone-Taylor procedure may still be done, but resection of the proximal interphalangeal joint (PIP) may be indicated (see the technique for the Girdlestone-Taylor tendon transfer in Chapter 7).

Salvage Procedures

For any procedure used to correct a progressive neuromuscular condition, the outcome is difficult to evaluate. Evaluation of triple arthrodesis, which for years has been a hallmark procedure in the treatment of the severe cavovarus foot deformity in this diagnosis, would indicate mixed results at best.94,88,159 Triple arthrodesis should be used only as a salvage procedure for a rigid deformity that shows signs of degenerative joint disease of the hindfoot. It is particularly important to ensure that concomitant ankle instability is addressed with ligamentous reconstruction, with or without anterior ankle debridement, and that the hindfoot is positioned in a neutral position if a triple arthrodesis is deemed necessary.

The triple arthrodesis can be an excellent salvage procedure. The concept of removing wedges to perform this arthrodesis is rarely beneficial.136,137,154,165 The key to successful correction of the deformity is derotation of the calcaneus under the talus, allowing the talus to plantar flex and the hindfoot varus to move into slight valgus.

A variety of midfoot osteotomies have been described, the rationale being that the midfoot is the apex of the deformity. The Japas procedure ⁶⁷ is essentially a vertical chevron osteotomy through the midtarsal region. The Jahss procedure⁶⁵ is a truncated wedge osteotomy through the midtarsal region at the apex of the deformity; however, the foot must have appropriate muscular balance.

Extraarticular corrections are preferred. The cavus deformity in the sagittal plane typically is readily correctable with calcaneal and first metatarsal osteotomies. If present, the adductus deformity in the transverse plane can be corrected with closing-wedge cuboid and opening-wedge cuneiform osteotomies. For the most severe deformities, a biplanar closing-wedge osteotomy through the midfoot (navicular/cuneiform/cuboid) is used.

Ankle instability must be documented and some form of treatment instituted. When the cavovarus foot is reconstructed, a lateral ligamentous reconstruction can be performed as well. This can be done with local tissues or autologous tendon (see the discussion of ankle reconstruction in Chapter 30).

Myelomeningocele

Myelomeningocele is a congenital malformation of the CNS, resulting in dysplasia of the vertebral elements as well as the spinal cord. Early closure of the meningocele with placement of a ventricular peritoneal shunt has vastly improved these patients’ survivability. Vitamin treatment for pregnant woman has lowered the risk of this condition. These patients can be classified by their level of involvement into four basic groups: thoracic, upper lumbar, lower lumbar, and sacral. The thoracic and upper lumbar patients are, by definition, paralyzed below the knee but might have involuntary motors affecting foot position. The pattern of sensory and motor loss is seldom symmetric. This is a CNS disorder, and both lower motor neuron (flaccid paralysis and lack of sensation) and upper motor neuron (spasticity) abnormalities must be considered. Growth can also change the basic neurologic picture because of tethering of the cord from soft tissue scars or bony anomalies within the vertebral column.

Treatment of this disorder involves a range of deformities, from congenital presentations to modeling changes in the growing foot and conditions in the skeletally mature patient. Up to one half of children with myelomeningocele have some type of significant foot deformity.⁴⁰ The most common congenital foot deformity is talipes equinovarus (clubfoot) deformity.¹³⁰ Vertical talus is also noted with this diagnosis. Other deformities include calcaneus and equinus of the hindfoot with components of valgus or varus. The primary goal in treatment of these foot deformities is a relatively supple plantigrade foot. Because of the highly variable paralytic and sensory deficit and variable functional capacity, treatment of these patients must be determined carefully. It is just as important for the nonambulatory patient to have a plantigrade, shoeable foot that fits on the footrest of a wheelchair as it is for a low lumbar patient with good quadriceps function to have a plantigrade and braceable foot and ankle.

Sensory Deficits

Although the early emphasis in these children is on functional motor level (i.e., whether they will ultimately ambulate), an important long-term prognostic factor is foot sensibility. The majority of these children have an insensate foot and loss of proprioception; only patients with the lowest lumbar and sacral levels have any preservation of plantar skin sensation. Early patient and parent education focuses on careful inspection of feet, socks, and footwear. All children with this diagnosis should wear some type of orthosis as a protective measure for the insensate foot and a preventive measure against the deforming forces that can lead to fixed contractures and deformities.¹⁶³ These children must never be barefoot and, even when swimming, must wear some appropriate form of protective footwear.

Discussions of foot sensory deficits with patients and their parents must also include the need for preservation of a plantigrade foot. Deformity that limits the weight-bearing contact surface of the foot’s plantar aspect increases focal pressures and can result in ulcerations.⁵⁵ The correction of deformity alone is not enough; deforming forces around the foot and ankle must be balanced as well.

Treatment Approach

Arthrodesis to correct deformities of the foot and ankle in these patients should be avoided.¹⁸ Rigidity of the foot and ankle reduces the foot’s ability to accommodate to irregularities of the ground. This can result in increased pressure on the foot’s plantar surface and on the joints adjacent to the sites of fusion.⁹¹ This increased pressure through the remaining articulations of the foot and ankle can result in the Charcot neuropathic arthropathy.⁵⁶ Although triple arthrodesis is an excellent procedure for the correction of severe deformities of the foot, it is not appropriate in patients with sensory compromise. In these patients, tendon transfers and extraarticular osteotomies can be used to reduce pressure on the calcaneus.¹⁰⁷ However, in the older or nonambulatory patient who has trouble fitting shoes or braces, triple arthrodesis is a good compromise to obtain a plantigrade foot. Even then, a limited fusion is preferable.¹⁷

Cast Treatment

Use of casting in these patients should be reserved for healing of ulcerations and for the protection of soft tissues after surgical reconstructive procedures. Serial casting of deformities can be problematic because of the insensate nature of the foot. The casting of the congenital deformities in these patients must be carefully considered.¹⁵³ The majority of these feet will eventually need surgical correction. If no correction is found after short-term casting, the clinician should consider the use of holding splints until the child’s foot is mature enough to undergo surgery. Postoperative casting must be lightweight, be carefully padded, and have room for swelling. The cast should be used only to support the soft tissues and not to achieve foot correction.

When an insensate foot is covered with a cast, there must be a low threshold for removal of the cast and for inspection of the soft tissue envelope of the foot. Whenever persistent fever occurs with no evidence of a respiratory or urologic cause, the cast must be removed and the foot examined. Total-contact healing casts are the most common type of casting used in the patient with myelomeningocele. The first cast should be changed after 1 week and then changed every 1 or 2 weeks after that. The total contact equally distributes plantar pressure and helps diminish swelling.

Recurrent plantar ulcerations require patient education and careful evaluation of the foot and ankle for deformities causing increased pressure on the foot’s plantar surface. If a bony prominence cannot be protected with the orthosis, surgery is indicated. Surgery must be performed in a latex-free environment; that is, nothing that comes into contact with the patient may contain latex.

Talipes Equinovarus

The clubfoot deformity (Fig. 34-17) is generally seen in myelomeningocele of the third lumbar level or above.^130,34 At this level, the foot is essentially completely paralyzed and insensate, with occasionally some anterior tibial function. In the infant, it is very difficult to assess any voluntary or involuntary motor function around the foot and ankle. Repeat examinations are helpful, as is family input, but often family members mistake hip flexion for foot motion. The difficulty with motor function assessment is evident in the patient whose unrecognized posterior tibial function results in progressive clubfoot deformity.

Figure 34-17 A 9-year-old with a low lumbar-level myelodysplasia, who received no treatment for his bilateral clubfeet, now has severe rigid equinovarus deformities. Note the calf atrophy and the callosities over the bilateral midfoot and hindfoot regions that correspond to his weight-bearing surface.

Conservative Treatment

Because of the insensate nature of these feet and their relative stiffness on presentation, cast treatment should be used carefully.153,96 The majority of these feet do ultimately require surgery; however, casting should attempted initially. The foot should first be manipulated and then a holding cast applied. The cast itself should not be used to get further correction after it has been applied (Fig. 34-18). If casting is successful, splints must be worn full time until the child is standing. The authors’ preference is to stop casting at 3 months if the foot is not corrected, and perform surgery at approximately 9 months. Surgery at this age usually allows the patient to be up and standing or walking at approximately 1 year of age. This helps maintain the patient’s development and the plantigrade nature of the correction.

Figure 34-18 A 1-month-old child with myelodysplasia and bilateral clubfoot deformities undergoing initial casting. The foot is first manipulated, and then a cast is applied, holding this position with no further correction applied after the cast is placed.

Surgical Treatment (Video Clip 91)

The clubfoot deformity in myelomeningocele cannot be corrected by limited surgery (Fig. 34-19). The use of the complete subtalar release is necessary.⁹³ Only in sacral-level deformities should tendon lengthening be performed. At all other levels, the tendons should be resected; if not, scarring of the lengthened tendons will result in recurrence of the deformities. It is easier in the long term to brace a flaccid foot. The main concern at surgery and in the immediate postoperative period is the soft tissue envelope and the potential for significant loss of skin (see the discussion of surgery for clubfoot in Chapter 33).

Figure 34-19 A 9-month-old undergoing surgical correction of a right clubfoot, using the Carroll two-incision surgical approach. An intraoperative view is seen of the posterior ankle and hindfoot. The lengthened Achilles tendon is retracted at the top and bottom of the operative field. The muscle belly of the peroneus brevis is seen on the right, and the tendon of the flexor hallucis longus is seen on the left. The probe is centered on the subtalar joint with the ankle joint just superior.

In late childhood and adolescence, with a fixed bony deformity, osteotomies should be considered before a triple arthrodesis or a talectomy.¹⁶¹ Although a talectomy will correct the deformity, the position is difficult to maintain with orthotics, and plantar pressure will not be evenly distributed.^{38,97,128,133,134} Careful evaluation of bony deformity and any residual motors that may be causing recurrent deformation must be factored into the surgical plan. This, combined with the patient’s functional needs, provides some rationale as to how aggressive the surgeon must be to obtain a completely plantigrade or a near-plantigrade foot.⁹⁶

Correction of Clubfoot

Surgical Technique

1. The most common surgical incision is the Cincinnati incision.³¹ This approach provides excellent visualization from the medial midfoot around the posterior aspect of the hindfoot to the lateral midfoot. The primary difficulty with this incision in the foot with a severe equinus deformity is sloughing of the posterior skin. After correction of the foot deformity and closure of the skin, careful assessment of skin tension should be evaluated. By leaving the foot in a plantigrade position and performing slow, gentle serial casting after postoperative swelling has subsided, this risk of skin slough may be avoided.

2. When too much tension still exists, to obtain posterior skin closure, a vertical posterolateral incision can be made. After mobilizing the posteromedial skin and rotating it to achieve coverage, the posterolateral skin is mobilized and rotated, leaving a skin defect over the extensor brevis muscle dorsolaterally, which can be covered with a split-thickness skin graft.

3. The two-incision surgical approach of Carroll,²¹ which combines a vertical posterolateral incision and an S-shaped medial incision, is an excellent alternative. This provides good exposure and has been effective with even the most severe deformities.