Orthopedic Surgery for Spinal Muscular Atrophy
Children with SMA face several orthopedic challenges including scoliosis, joint flexion contractures, subluxations and dislocations of the hip, and bone fractures. By far the most common orthopedic problem in SMA patients is progressive neuromuscular scoliosis. Spinal abnormalities further compound respiratory issues brought on by weakness of the intracostal muscles, which puts patients at great risk for restrictive pulmonary disease and various respiratory co-morbidities.
Chest Deformity, Hip Instability, Contractures, and Fractures
Patients with SMA also experienced chest deformities that can lead to thoracic insufficiency and compromise pulmonary health. Hip instability is common, as are muscle contractures and bone fractures.
Patients with progressive neuromuscular diseases like Spinal Muscular Atrophy (SMA) have extremity weakness that can predispose to contractures, which affects the range of motion in the joints, muscles, and soft tissue. The etiology of contractures in SMA is multifactorial and includes muscle fiber loss, fatty infiltration of muscle, imbalances of agonist and antagonist muscles’ relative strengths, and static positioning.
The combination of low mobility, osteoporosis, and low vitamin D levels increases the risk of fractures in SMA. A consortium of SMA experts recommends prevention of fractures through a comprehensive bone health program including optimized nutrition (sufficient calcium and vitamin D), physical therapy to avoid disuse, monitoring of bone density with imaging, and obtaining regular vitamin D serum levels.
Scoliosis is an early orthopedic complication of SMA. Patients with SMA have poor respiratory effort due to weakness creating less respiratory resistance to scoliotic changes and an accelerated rate of deformity. Scoliosis reduces respiratory capacity in patients with SMA and worsens their respiratory impairment. Scoliosis can exacerbate sitting difficulties.