Charcot-Marie-Tooth Disease: Surgical Management of a Progressive Disease State

In 1886, Charcot and Marie described a progressive and slow form of muscular dystrophy characterized by weakness and wasting of the feet and legs followed by hand involvement. In that same year, Tooth independently described a progressive form of peroneal muscular atrophy. Thus, Tooth correctively described the inherited disease state, before the discovery of Mendelian genetic laws, as a neuropathy.^1,2

Charcot-Marie-Tooth (CMT) disease is the most common inherited disorder of the peripheral nervous system. One must remember this is a progressive neuromuscular disease. It has been divided into 2 large described groups. Charcot-Marie-Tooth type 1 is the demyelinating variant, which comprises 80% of CMT diagnoses. Charcot-Marie-Tooth type 2 is the neuronal variant, comprising 20% of CMT.^1,2

Charcot-Marie-Tooth type 1 represents the demyelinating form, with severe reduction of nerve conduction velocities, absent muscle stretch reflexes, and “onion bulb” formation on microscopic nerve biopsy. Charcot-Marie-Tooth type 2, the neuronal form of the disease, demonstrates normal or mildly reduced nerve conduction velocities, significantly decreased peripheral nerve amplitudes, normal muscle reflexes, and non-hypertrophic forms of myelin proliferation on microscopic biopsies.^1,2

Charcot-Marie-Tooth demonstrates a slowly progressive weakness of the distal limb musculature. Symptoms normally occur in the late first and early second decades of life. The muscle weakness occurs initially in the feet and legs. Target musculature initially includes the tibialis anterior and peroneus brevis muscle tendons. Patients may frequently trip over objects on the floor. Foot drop typically leads to a steppage or equinus gait. Slow, progressive atrophy of the leg muscles leads to a “stork leg” appearance or an “inverted champagne bottle” appearance. This is secondary to significant lower extremity atrophy below the knee. With maintenance of normal muscle tone and function above the knee, leg cramps occur with extended periods of walking. Pes cavus itself is not significantly present in the initial presentation, but tends to develop with the aging process.²

Insight into Management of the Lower Extremity in CMT

For patients demonstrating only mild cavus deformities in the first and second decades, conservative care with calf stretching, paired with orthotic care, can be effective. In the early phases of development of cavus deformity, heel varus and plantarflexion of the first metatarsal can occur. More significant presentations will be reveal a “peek-a-boo” heel sign (Figure 1). This indicates a more significant varus heel position, visible in front of the ankle.

The Coleman block test is instrumental in determining the biomechanical apex of the deformity. When the first metatarsal drops off the block, if the heel varus position comes to vertical or a slightly increased valgus position, this then denotes that the first metatarsal is the driving force. However, if in a case where the first metatarsal drops off the block, the heel remains in a fixed varus position, then the restricted motion can be due to abnormal subtalar joint axis deviations.

So, in the first case, we would plan orthotic construction for the patient involving a deep heel seat with molding of the longitudinal arch, and a first metatarsal head cut-out. In the second case, the orthotic would include a deep heel seat with an extrinsic rearfoot post, a molded longitudinal arch, and a first metatarsal head cut-out. Thus, in the first case, we have a forefoot-driven heel varus creating a cavus deformity. In the second case we have a rearfoot-driven cavus deformity. 

Biomechanics of Progressive CMT and Applied Surgical Principles

As mentioned earlier, the initial neuromuscular weakness of this condition manifests anteriorly (tibialis anterior) as well as in the intrinsic musculature (lumbricales and interossei). The peroneus brevis also loses its function early in the disease state. The forefoot manifestations include hammertoe deformities due to loss of proximal phalangeal instability. The flexor digitorum longus tendon creates this instability by overpowering the extensor digitorum longus tendons.

The hallux develops a malleus deformity through loss of strength of the tibialis anterior with weakness of the intrinsics (flexor hallucis brevis, abductor hallucis, adductor hallucis). This then leads to an increased antagonistic force to the peroneus longus muscle and tendon, which in turn leads to plantarflexion of the first metatarsal. The apex of this force occurs at the navicular-medial cuneiform joint. This is further enhanced by the weakness of the tibialis anterior muscle and tendon with loss of the function of the peroneus brevis.

The tibialis posterior, flexor digitorum longus, and flexor digitorum brevis produce a significant adduction force across the midfoot. This force centers along the talonavicular and subtalar joints. This leads to midfoot supination, and with retrograde force across the talonavicular joint, external rotation of the tibia and fibula occurs via closed kinetic chain supination. Varus positioning of the heel with an associated potential equinus is created by the varus neuromuscular force. Equinus, if present, is always passive in relation to the position of the calcaneus. As the calcaneal varus increases due to the position of the subtalar joint, the more likely surgical intervention becomes.^3–6

Case Studies in Charcot-Marie-Tooth Disease

Case 1. A 19-year-old male noted some progressive hammertoe deformities that caused him problems with ambulation and shoe gear beginning at age 12. He had to give up soccer because of instability and ankle sprains in sports.

On evaluation, vascular perfusion was normal. Hair growth and skin integrity were within normal limits. Neurologically, there were some deficits to 2-point discrimination, and sharp-dull and vibratory sensation were decreased to the level of the LisFranc joint proximally. The patient could perceive a Semmes-Weinstein monofilament to the plantar foot and proximal to the LisFranc joint dorsally. The muscular strength exam was as follows: tibialis anterior strength was 3/5; extensor hallucis longus and extensor digitorum longus were 5/5; intrinsics (hallux and digital intrinsics) were 0/5; peroneus longus was 5/5; and peroneus brevis was 3/5. The tibialis posterior, flexor hallucis longus and flexor digitorum longus were 5/5. The gastrocsoleus complex was 5/5. There was no evidence of inverted champagne bottle deformity to the lower extremity and no signs of hand involvement.

Clinically, rigid hammertoes of digits 2–5 were noted on the right, as was hallux malleus and a semi-rigid plantarflexed first metatarsal. In relaxed calcaneal stance, a “peek-a-boo” heel sign is present. On the Coleman block test, the first metatarsal, when dropped off, indicated a persistence of the varus position of the heel. No significant midfoot adduction was noted. The position of the fibula showed a mild posterior displacement in relation to the vertical bisection of the tibia.

The surgical plan included the following: a Jones sling and muscle tendon transfer of the extensor hallucis longus to the first metatarsal neck of the right foot; a Taylor-type proximal interphalangeal joint fusion with capsulotomies of digits 2–5 utilizing a 0.045-inch K-wire fixation to the right extremity; and a Hibbs extensor digitorum longus transfer to offload the metatarsophalangeal joint to assist the weakened tibialis anterior with dorsiflexion.

Equinus was not present despite the varus heel position. We chose a Dwyer calcaneal osteotomy due to the presence of the fixed varus, which was present on the Coleman block test. In cases where the cavus deformity does not involve the ankle, one addresses the cavus foot structurally. Initially, the patient is placed prone and determination of equinus (gastroc-soleus) is made by the Silfverskiöld test. If present, a gastrocnemius resection or tendo-Achilles lengthening is made. The next step is to evaluate the position of the first metatarsal in plantarflexion. If the plantarflexion is still present after the equinus release, a peroneus longus to brevis transfer is performed. If the first metatarsal remains plantarflexed, a dorsiflexory wedge osteotomy of the first metatarsal or a first-metatarsal-cuneiform arthrodesis is performed (Figure 2).^6,7

Postoperatively the patient was placed in a posterior splint at 90 degrees with sutures removed at 3 weeks postop. The patient then used a controlled ankle motion (CAM) boot but still maintained non-weight-bearing for 1 more week. Then at 4 weeks postoperative, the patient was allowed full weight-bearing and the K-wires in the toes were removed at that time. At 8 weeks postoperative, the patient was sent to physical therapy and converted to normal shoe-wear. By 4 months postoperative he was fully ambulatory with minimal swelling and pain. The patient and team have since begun planning for intervention for the contralateral limb.

Case 2. A 46-year-old White male presented with rigid equino-cavo-varus deformity, manifested primarily in his left foot. He had seen 3 prior physicians, but he was diagnosed with congenital clubfoot deformity. The last physician, who evaluated the patient in his 30s, told him he had a form of Charcot deformity despite a lack of apparent risk factors for the condition.

During the initial evaluation by the senior author, the patient was in an Arizona brace and had a history of frequent ulcerations to the plantar lateral fifth metatarsal styloid. He also had a large bursa formation (8 x 9 cm) with a small sinus that required surgical excision.

His neuromuscular exam, along with the fact that the patient denied having the deformity involving his feet in the early first decade of life, led to neurology referral and subsequent diagnosis of advanced Charcot-Marie-Tooth disease type 1.

On examination of the patient’s left lower extremity, one could note significant chronic lymphedema from numerous soft tissue infections and ulcerations. His pulses were non-palpable due to this state, but arterial Doppler noted triphasic waveforms to the dorsalis pedis, posterior tibial, and peroneal arteries. On neurologic exam, he was unable to perceive a Semmes-Weinstein monofilament to above the ankle joint, indicating a significant peripheral sensory neuropathy.

On X-ray, Meary’s angles revealed bisection proximal to the talonavicular joint, which was dislocated. Meary’s angle bisection was also noted proximally at the ankle joint. The forefoot medially not purchasing the ground with an elevated first metatarsal and a plantarflexed hallux. Weight-bearing occurred along the lateral midfoot and rearfoot resulting in a non-plantigrade foot.

The surgical plan included a talectomy with calcaneonavicular arthrodesis, a fibular osteotomy and resection with utilization of allograft and autograft with bone marrow aspirate. Grafting back-filled any residual non-contact sites at the arthrodesis. Finally, multiple 3.5mm screws were utilized for the fusion (Figure 3).

The patient was non-weight-bearing in a posterior splint for 12 weeks. Due to continuous oozing of blood, we maintained his sutures for 4 weeks. At this time we reapplied the posterior splint with incisions healing well and oozing ceased. At 12 weeks, he began to use a CAM boot with partial weight-bearing and physical therapy. At 4 months, the patient is ambulating well with good maintenance of his corrected position and a plantigrade foot position.

In the case of rigid equinovarus in which subluxation of the talonavicular and ankle joint occurs, surgical correction can be obtained with a Lambrinudi procedure if the tibiotalar subluxation is manually reducible. This would then allow maintenance of the arthrodesis at the foot level. One could then produce a plantigrade foot at is at the talocuneiform joint. In cases of severe dislocation, as seen in this case, the Meary’s angle bisection occurs proximal to the talonavicular joint.

The severe dislocation that was seen in this location in this foot was due to unopposed neuromuscular imbalance created by the Charcot-Marie-Tooth disease state. Chiefly, the deep flexors (flexor digitorum longus and flexor hallucis longus) loss of function of the peroneus brevis while maintenance of tibialis posterior function led to severe closed kinetic chain supination of the subtalar joint. Literally, the talus was forced into an abducted, dorsiflexed and inverted position subluxing the talus from the ankle and from the talonavicular joint. This dislocation in combination with creates a severe external rotation of the tibia and fibula that help dislocate the calcaneus in a fixed varus position, leading to a severe non-plantigrade foot. The rigidity can only be addressed in this case by talectomy to allow the navicular then to be aligned with the tibia and then the calcaneus with the tibia, thus noting on the axial view a plantigrade foot.^3,4

In Conclusion

Charcot-Marie-Tooth disease is an insidious and slowly progressing neuromuscular condition that ultimately results in the deformity of the lower extremities. The foot deformities common in Charcot-Marie-Tooth disease often fail conservative therapy and must be managed surgically. Here, we examined two Charcot-Marie-Tooth type 1 patients with significant lower extremity deformity secondary to their condition. The patients in both cases failed conservative therapy and required bilateral surgical reconstructions. These patients would both achieve a favorable outcome, obtaining functional, pain-free, plantigrade feet.

Harry John Visser, DPM, FACFAS is the Director of SSM Health Podiatric Surgical Residency in St. Louis.

Harrison James Gilley, DPM is a second year resident at SSM Health Podiatric Surgical Residency in St. Louis.

Brittany Ryan Staples, DPM is certified by ABFAS and is a former resident of SSM Health Podiatric Surgical Residency in St. Louis.

References
1.    Murakami T, Garcia CA, Reiter LT, Lupski JR. Charcot-Marie-Tooth disease and related inherited neuropathies. Medicine (Baltimore). 1996;75(5):233-250.      
2.    Rambelli C, Mazzoli D, Galletti M, et al. Foot assessment clinical scales in Charcot-Marie-Tooth patients: a scoping review. Front Hum Neurosci. 2022;16:914340.
3.     Georgiev H, Georgiev GP. Talectomy for equinovarus deformity in family members with hereditary motor and sensory neuropathy type I. Case Rep Orthop. 2014;2014:643480.
4.     Kim BS. Reconstruction of cavus foot: a review. Open Orthop J. 2017;11:651-659.
5.     Oesman I, Sari CM. Neglected neurogenic clubfoot treated with Achilles tendon lengthening using Z-plasty, total talectomy, and tibiocalcaneal arthrodesis. Int J Surg Case Rep. 2021;84:106051.
6.     Sprinchorn AE, Beischer AD. Cavovarus foot surgery including a peroneus longus transfer: a 2- to 6-year follow-up. Foot Ankle Orthop. 2021;6(3):24730114211021030.
7.     Love B, Alexander B, Ray J, et al. Outcomes of tibiocalcaneal arthrodesis in high-risk patients: an institutional cohort of 18 patients. Indian J Orthop. 2020;54(1):14-21.
8.     Gaber K, Mir B, Shehab M, Kishta W. Updates in the surgical management of recurrent clubfoot deformity: a scoping review. Curr Rev Musculoskelet Med. 2022;15(2):75-81.