Charcot-Marei-Tooth disease (CTM disease) is a hereditary, progressive neurological myasthenic syndrome first described clinically in 1886 by two French neurologists, Jean Martin Charcot and Pierre Marie, and an English scholar, Howard Henry Tooth. At least 50% of patients with high arched feet have CTM disease, making it the most common cause of high arched feet. In the past, it was often referred to as peroneal muscular dystrophy, hereditary peroneal muscular dystrophy, and neurogenic muscular dystrophy. However, the lesions of this disease are not only limited to the peroneal muscles, but the intrinsic muscles of the foot and upper limb muscles are also often involved. Peroneal muscular dystrophy is not accurate. It is now often referred to as hereditary motor-sensory neuropathies (HMSNs) in the foreign literature. The incidence of HMSNs is reported in the foreign literature to be 10-40 per 100,000. The main clinical features are progressive muscle weakness and atrophy of the distal extremities with sensory impairment.
I. Etiology and pathology: CMT disease is a neurological disorder caused by hereditary single gene mutation. Its occurrence is closely related to specific genetic variants. More than 30 genes associated with CTM have been identified. In addition, there are various forms of inheritance, such as autosomal dominant, autosomal recessive, X-linked dominant , and X-linked recessive.
CTM foot deformity occurs due to imbalance of the foot muscles caused by peripheral neuropathy. The weakness of the short peroneal tendon causes the relatively strong antagonist muscle, the posterior tibial muscle, to pull the foot inward; the weakness of the anterior tibial muscle causes the relatively strong antagonist muscle, the long peroneal muscle, to cause plantarflexion deformity of the first metatarsal, causing the medial longitudinal arch to increase, and over time, forefoot valgus, inversion and contracture of the metatarsal tendon membrane occur. Due to the change of the “tripod structure” of the weight-bearing foot, the forefoot valgus deformity causes compensatory hindfoot valgus. Weakness of the anterior tibialis muscle causes the triceps calf muscle to cause foot drop. The weakness of the intrinsic muscles of the foot makes the relatively strong extrinsic muscles cause the typical claw toe deformity.
Second, the typing. According to the clinical and electrophysiological characteristics, CMT can be divided into 5 types:
(1) CMT type 1 (demyelinating type): autosomal dominant. The onset of the disease is early, with more than 3/4 of the cases starting before the age of 20. The incidence of high arched feet is 20% in children and up to 67% in young adults. The nerve conduction velocity is slowed (median nerve motor conduction velocity < 38 m/s). Nerve biopsy shows extensive segmental demyelination and myelin hyperplasia forming "onion head" like structures. This type accounts for 50% of CTM disease.
(2) CMT type 2 (axonal type): The genetic form is unclear. The onset of the disease is late, with half of the cases starting after the age of 20 years, and the nerve conduction velocity is normal or mildly reduced (median nerve motor conduction velocity > 38 m/s). Sensory damage is mild. Nerve biopsies show axonal degeneration, and rarely demyelination. This type accounts for 20% of CTM disease.
(3) CTM type 3: Dejerine-Sottas syndrome. It is recessive and rare. It often develops in infancy. It often has spinal deformity, ataxia, and severe sensory impairment.
(4) CTM4 type: autosomal recessive inheritance. Rarely seen.
(5) CTM-X: an X-chromosome linked form of inheritance. It is more common in males. It accounts for about 10%-20% of CTM disease.
Clinical manifestations
(a) Clinical features.
（Nagai investigated the diagnosis of 148 outpatient cases of children with bilateral high arched clubfoot by means of nerve conduction velocity testing and genetic examination. If the presence or absence of family history was excluded, 116 cases (78%) were diagnosed with CTM disease. And the diagnosis rose to 91% in children with a family history. In China, Zhang Fufeng reported 110 cases, 6316% of which had a family history.
(2) Onset in childhood to adolescence.
(3) The incidence rate reported in China is 1 /2,500 to 1 /10,000.
(4) There are more males than females, and the ratio of males to females in this group is 2.03:1.
(5) Symmetrical distal lower limb muscle weakness and myasthenia gravis.
(6) The lower extremities are in the shape of inverted bottle, or crane legs.
(7) Some patients may have atrophy of the distal muscles of both upper limbs.
(8) No or only slight sensory impairment, terminal type sensory impairment and a series of autonomic dysfunction may appear in the extremities.
(9) High arched foot, spinal deformity, and clubfoot. Chen Rong and Liang Xiuling summarized 338 cases of CTM disease in China in 1996 and found that 72 cases (85.7%) of type I 105 cases and 7 cases (46.7%) of type II 15 cases with high arched feet.
(ii) Clinical examination
(1) Soft deformity or rigid deformity? Flexible deformity has normal or mostly normal joint movement. The short fibular and anterior tibial muscles are often the first to be involved in CTM disease. The posterior tibial muscle is the last to be involved.
Fenton found that in CTM disease the muscles were affected in 81% of the short fibularis, 81% of the anterior tibialis, 83% of the extensor digitorum longus, 91% of the extensor digitorum longus, 100% of the third fibularis, 42% of the long fibularis, and 20% of the posterior tibialis.
(2) Toe deformity: bunions often have hammer toes, and other lateral toes often have claw toe deformities. Determine whether the toe deformity is a reversible or a rigid deformity?
(3) Forefoot deformity: After correction of hindfoot pronation, the forefoot often shows valgus deformity or 1st metatarsal plantarflexion deformity. In addition, full metatarsal plantarflexion can form a high arch foot.
(4) Midfoot deformity: tarsal plantarflexion.
(5) Hindfoot deformity: the hindfoot often has valgus deformity and high arch deformity (heel tilt angle >30°). The Coleman lateral wood block test can be used to identify whether the hindfoot pronation is caused by forefoot valgus. That is, whether or not the pronation can be corrected. When the forefoot is placed in the valgus position and the hindfoot inversion is corrected, it is called forefoot-derived hindfoot inversion. Hindfoot high arch is mostly pseudo-high arch, that is, a compensatory phenomenon of forefoot plantarflexion deformity.
(6) extensor muscle weakness foot drop. The anterior tibial muscle and extensor tendon are weak.
(7) Contracture of the Achilles tendon or gastrocnemius muscle.
(8) Sensory condition.
(4) Auxiliary examinations: Routine frontal and lateral examination of the foot and ankle in weight-bearing position. Measure the Meary angle, heel tilt angle, Hibbs angle, etc. Observe whether there is dislocation and degeneration of the joint. Other tests should be used according to the situation (1) electromyography (2) genetic testing (3) muscle biopsy (4) MRI.
V. Surgical treatment.
Since CTM disease can have multiple manifestations depending on the condition. The principle of surgical reconstruction is to correct all deformities, establish the muscle balance of the foot and ankle, and prevent the recurrence of deformities. An individualized treatment plan should be developed according to the patient’s specific situation. Restrictions should be distinguished between flexible and rigid deformities, in addition to other considerations such as patient age, prognosis, muscle strength, and patient expectations. For example, flexible deformities should be preserved as much as possible, while stiff deformities may require fusion of the joint. However, if the patient is younger than 12 years of age, the joint should be preserved if possible, regardless of stiffness. If all muscle strengths are below grade 4, tendon transposition cannot be performed, and the joint should be fused even though it is a flexible deformity. Preoperative communication with the patient should be adequate. The disease may continue to progress and the surgical outcome may change over time.
(i) Soft tissue balancing surgery.
Metatarsal tendon lengthening or severing.
Achilles or gastrocnemius tendon lengthening.
Extension tendon lengthening or severing, or displacement proximal to the extensor tendon.
Displacement of the peroneus longus tendon to the peroneus shortus tendon.
Displacement of the posterior tibial tendon to the dorsum of the foot.
Flexor tendon transposition for claw toe (Girdlestone-Taylor procedure).
(ii) Bone surgery.
Interphalangeal joint fusion.
Dorsal extension osteotomy of the metatarsal.
Mid-tarsal osteotomy: Japas osteotomy, Cole osteotomy.
Heel osteotomy: Dwyer’s osteotomy, heel exostosis osteotomy.
Triple joint fusion.
Tibial talar heel fusion.
(C) Surgical options
(1) Treatment of soft deformity
If there is still some muscle strength, joint movement should be preserved as much as possible. If the muscle strength is basically lost or the joint has degenerated, joint fusion surgery is needed to stabilize the joint.
These patients often have forefoot pronation or first metatarsal plantarflexion deformity. Hindfoot inversion deformity. Metatarsal tendon lengthening or severance is usually required. In early stage patients with a strong peroneal long tendon, the peroneal long tendon is displaced to the peroneal short tendon to eliminate the deformity force and increase the external rotation force of the foot. In patients with plantar flexion of the first metatarsal, a dorsal closed osteotomy of the base of the first metatarsal is performed to elevate the first metatarsal head. Dorsal extension osteotomies of the first, second, and third metatarsals may be required in patients with forefoot pronation.
If forefoot pronation is significant, a midtarsal osteotomy may be performed. If the bunion has a stiff hammertoe, an additional Jones procedure is required, which involves fusing the interphalangeal joint and relocating the extensor hallucis longus tendon to the proximal end of the first metatarsal. Heel osteotomy is performed for inversion deformities that cannot be corrected in the hindfoot.
(2) Treatment of toe deformity
It can be divided into the treatment of metatarsophalangeal joint and interphalangeal joint. For interphalangeal joint flexion deformity, interphalangeal joint fusion is possible. For dorsiflexion deformity of the metatarsophalangeal joint, unless it is a particularly mild deformity, extension of the extensor tendon alone is not effective. Girdlestone-Taylor surgery is indicated for reducible deformities of the metatarsophalangeal joint with extension tendon lengthening, dorsal capsulotomy, and metatarsal plate release. Complete dorsal stiffness dislocation requires shortening of the metatarsal bone.
(3) Management of extensor weakness foot drop. Displacement of the posterior tibial tendon to the first or second cuneiform. If the strength of the anterior tibial muscle is basically normal and the other extensor muscles are weak, this can cause inversion of the foot and requires an external displacement of the anterior tibial tendon.
(4) Contracture of the Achilles tendon or gastrocnemius muscle. The contracture of the Achilles tendon or gastrocnemius muscle is prolonged.
(5) Management of midfoot stiffness deformity
Metatarsal cuneiform joint fusion, mid-tarsal joint osteotomy (Japas, Cole, Jahss osteotomy)
(6) Treatment of hindfoot deformity
Flexural deformity: forefoot surgery.
Stiff deformity: triple joint fusion or tibial talar heel fusion. Severe deformity using an external fixator to gradually correct the deformity combined with joint fusion can avoid complications caused by a single orthopaedic surgery.