ORTHOPAEDIC MANAGEMENT FOR MUSCULAR DYSTROPHY
The primary goal is to prevent development of contractures and maintain functional ambulation for as long as possible. A regular program of physiotherapy and use of orthotics prevents joint contractures and dynamic orthosis can aid in ambulation as well.
Once muscle contracture develops and walking becomes increasing difficult, soft tissue surgery is indicated to maintain the limb alignment and joint position. Surgery improves the walking balance, and prolongs the ability of the child to walk.
Shapiro and Specht classified surgery for DMD:
The Early-Extensive ambulatory approach consists of muscle releases at hip, hamstring, heel cords and tibials posterior before the onset of contractures. The Moderate ambulatory approach involves ankle and knee release when the Palliative approach child get difficulty in walking. The minimum ambulatory approach involves only correction of equinus, the Rehabilitative approach is used when the child ceases to walk and the aim of surgery is to re-establish walking and lastly the Palliative approach where the child is wheel-chair bound and surgery is only done for relief of pain, comfort, ease of nursing care and for shoe wear.
The timing of surgery is controversial. Most agree that there is a window period of 3 – 6 months after the child ceases to walk, to perform surgery to re-establish ambulation. Rideau et al recommend surgery before the contractures develop and they propose that the quality of ambulation is enhanced without orthoses. Other advocate surgery as soon as the contractures develop. Early surgery at the onset of contractures can prolong ambulation by two – three years than patients that didn’t undergo surgery.
Delayed operations after the child has stopped walking for more than a year will not establish ambulation. Also, obesity, osteoporosis and poor cardiovascular status are risk factors for surgery.
Ankle surgery comprises of percutaneous heel cord tenotomy, “Z” lengthening, and recession or transfer of tibialis posterior to correct dynamic varus. Knee surgery consists of hamstring lengthening, or tenotomy. . Soft tissue surgery is required when knee deformity exceeds 20 degrees of flexion. Hamstring lengthening and long leg bracing will suffice to correct this degree of deformity. Rarely a supracondylar osteotomy with rigid fixation is required.
Hip flexion release involves recession of the anterior hip muscles including the sartorius, rectus and tensor fasciae latae.
Post-operative rehabilitation should be aggressive and weight bearing should start on first post-operative day gradually progression to assisted ambulation as soon as possible. Any bed rest or immobilization enhances the muscle weakness and thus casting should be avoided as far as possible. Immediate fitting of orthosis helps in early ambulation thus persevering muscle strength.
Almost all children with DMD will develop scoliosis once they are non-ambulatory. Thus preservation of walking ability is paramount. Spinal screening for scoliosis is mandatory for all children with DMD.
Spinal deformity is common in teenaged boys with Duchenne dystrophy. Approximately 90% of boys with DMD will develop severe scoliosis, which is not amenable to control by nonsurgical means such as bracing or adaptive seating. Surgical stabilization of scoliosis is usually recommended when the curve exceeds 20 degrees before deterioration of pulmonary function obviates surgical intervention.
The typical curve pattern is a long sweeping thoraco-lumbar scoliosis, flexible and associated with pelvic obliquity.
Mild curves < 10 degrees should be watched closely and as the cobb angle exceeds 20 – 30 degrees, surgery should be contemplated. Bracing is not recommended as the muscle weakness will progress and bracing will delay surgery once the respiratory function is compromised.
Forced vital capacity decreases by 4`% each year and by 4 % for each 10 degrees of curve. Thus progression of scoliosis and deterioration of pulmonary function go side by side making delayed surgery precarious and unsafe.
Specially designed screws and rods are use to fix the spine and this provides good stability allowing better correction of the spinal curve.
Surgery improves the seating ability of the child, preserves pulmonary function, and prevents skin break down due to improper posture.
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