BracingZOrthotic Management and Orthopaedic Surgical Management of Limb Deformity

Management in Neuromuscular Diseases With Proximal Weakness

The prototypical disorder in which bracing and sur­gical management of contractures for prolonged ambulation has been applied is Duchenne muscular dystrophy.

The ankle deformity may be corrected by either a tendo-Achilles lengthening (TAL) or a TAL combined with a surgical transfer of the posterior tibialis muscle tendon to the dorsum of the foot.

Orthopedic surgical release of these contractures allows the DMD patient to be braced in lightweight polypropylene KAFOs with the sole and ankle set at 90 degrees, drop-lock knee joints, and ischial weight­bearing polypropylene upper thigh component. DMD patients who are braced may or may not require a walker for additional support. At times, DMD patients who have had excellent home stretching programs can be placed immediately into KAFO bracing without surgical tenotomies.

While DMD subjects are still ambulating indepen­dently without orthotics, they often use their ankle equinus posturing from the gastrocnemius-soleus group to create a knee extension moment at foot con­tact, thus stabilizing the knee when the quadriceps muscle is weak. Several authors have cautioned against isolated heel cord tenotomies while DMD patients are still ambulating independently. Overcorrection of the heel cord contracture in a DMD patient may result in immediate loss of the ability to walk without bracing unless the quadriceps are grade 4 or better (131).

The duration of ambulation in DMD has been successfully prolonged by prompt surgery and brac­ing, immediately implemented following loss of independent ambulation. Generally, the gains in add­itional walking time have been variable, but generally reported between two and three years.

Long-term benefits of prolonged walking include decreased severity of heel cord and knee flexion con­tractures at age 16 (137). This may ultimately improve shoe wear tolerance and foot positioning on the wheel­chair leg rests. Prolonged ambulation by lower extrem­ity bracing in DMD has never been documented to be an independent factor in the prevention of scoliosis. Disadvantages of braced ambulation center around the excessive energy cost of braced ambulation and safety concerns in the event of falls.

Weakness is the major cause of loss of ambulation in DMD, not contracture formation. Thus, the primary indication of orthopedic surgical tenotomies and pos­terior tibialis tendon transfers likely is the provision of optimal alignment for KAFO bracing. Little evi­dence supports the efficacy of early prophylactic lower extremity surgery in DMD for independently produc­ing prolonged ambulation (9,131,138).

In general, with the increased utilization of corti­costeroids in DMD, there has been a trend over the past two decades towards reduced use of lower extremity surgery and long leg bracing to prolong ambulation.

Management of NMD Patients With Distal Lower Extremity Weakness

Ankle dorsiflexors are often clinically weaker than ankle plantar flexors in neuromuscular disease because of selective involvement of the peroneal nerve in many neopathies and isolated anterior and lateral compart­ment weakness in several myopathic conditions such as FSHD, scapuloperoneal distribution LGMD, DMD, and Emery-Dreifuss muscular dystrophy. Ankle foot orthotics (AFOs) often are used for patients with distal weakness. AFOs are generally contraindicated in situ­ations where NMD patients utilize equinus posturing with forefoot initial contact to maintain a knee exten­sion moment in the setting of quadriceps weakness. Heel cord contractures may need to be surgically lengthened to allow for AFO or KAFO bracing. Cavus feet are common in peripheral neuropathies. Intrinsic muscle weakness of the foot results in hyperextension at the metatarsophalangeal joints and flexion at the interphalangeal joints with resultant claw toe defor­mities. This constellation of deformities may cause difficulty in walking, lack of balance and painful cal­losities. Treatment of the cavus foot depends on the patient's age, flexibility of the foot, bony deformity, and muscle imbalance. A supple foot can be managed nonoperatively by serial casting in a walking cast, fol­lowed by an AFO with a solid ankle in neutral posi­tion and a lateral heel wedge if significant hindfoot varus exists. Fixed soft tissue or bony deformity may require orthopedic surgery to produce a plantigrade foot. In skeletally immature children, triple arthrod­esis is contraindicated. Triple arthrodesis should only be considered as a salvage procedure for severe heel varus and severe midfoot deformity, with the goal being achievement of hindfoot stability in a skeletally mature patient.