Scoliosis is a common deformity in many types of neuromuscular diseases (see the image below). It is generally most severe in nonambulatory patients. Severe curves of the vertebral column cause difficulties in sitting. Bracing neuromuscular curves does not affect the natural history of scoliosis and is not definitive treatment. Surgical stabilization constitutes the mainstay of treatment for neuromuscular scoliosis. Progressive curves require surgical correction and stabilization.
Neuromuscular scoliosis can be defined as a coronal and sagittal plane deformity of the spine in patients with abnormalities of the myoneural pathways of the body. In neuromuscular spinal deformities, progression occurs much more frequently than in idiopathic scoliosis.
In addition, progression often continues into adulthood. The long-term effects of the spinal deformity in patients with neuromuscular conditions can be disabling. Loss of the ability to sit occurs, as does an accompanying decrease in overall function. In addition, pulmonary function is markedly affected.
Understanding the anatomy of the spine is crucial for safe and efficient exposure with a posterior approach. The incision is made from the spinous process above the most proximal vertebra to be instrumented to the most caudal extent of the proposed instrumented area. Identifying and staying in the midline is important so that muscle is not cut, which would lead to bleeding. The midline is identified by a thin line, which is actually the interspinous ligaments connecting the spinous processes.
Each vertebral level is exposed in a similar manner. An elevator is used to pull the soft tissue off of the spinous process, lamina, and transverse process of each respective level. To minimize blood loss, expose each segment completely the first time; do not leave soft tissue on the bone that will have to be removed later.
The pathophysiology is not well understood.  It seems logical to assume that scoliosis in these conditions is caused by muscle weakness, but this conclusion is difficult to support because some conditions are accompanied by spasticity and others by flaccidity. Furthermore, no consistent pattern of scoliosis is associated with a particular pattern of weakness.
Scoliosis associated with neuromuscular disorders has been classified by the Scoliosis Research Society into neuropathic and myopathic types.
The neuropathic conditions have been subdivided into those with upper and lower motor neuron lesions. The group with upper motor neuron lesions includes diseases such as cerebral palsy, syringomyelia, and spinal cord trauma; the group with lower motor neuron lesions includes poliomyelitis and spinal muscular atrophy. The myopathic conditions include arthrogryposis, muscular dystrophy, and other forms of myopathy.
Because neuromuscular scoliosis has so many causes, the patterns and incidence vary greatly. However, the prevalence of spinal deformity in the patient with a neuromuscular disorder is much higher than in the general population. It ranges from 20% in children with cerebral palsy to 60% in patients with myelodysplasia. The prevalence rises to 90% in males with Duchenne muscular dystrophy. In general, the greater the neuromuscular involvement, the greater the likelihood and severity of scoliosis.
With care in surgical technique and adequate postoperative care, complications can be minimized. The patient can return to the preoperative functional level with a successful surgical result, which consists of a solidly fused spine in balance in the coronal and sagittal planes over a level pelvis.
Myung et al conducted a retrospective review of the use of posterior-only spinal instrumentation and fusion to the pelvis with iliac screws in 41 patients with neuromuscular scoliosis (mean age, 14 years).  The fixation in the pelvis failed in 12 of the 41 (29%). No failures occurred if there were at least six screws in L5, S1, and pelvis (0/7); if there were fewer than six screws in L5, S1, and pelvis, the failure rate was 35% (12/34).
When traditional iliac screws with connectors to rods were used, all constructs had fewer than 6 screws in L5, S1, and pelvis.  Only one failure occurred when S2 iliac screws were used, but that failure was without clinical consequence. The mean time from surgery to failure was 18 months (range, 1-49). The authors concluded that not placing bilateral pedicle screws at L5 and S1, in addition to two iliac screws, was associated with a 35% early failure rate of pelvic fixation.
Awwad et al conducted a retrospective analysis to evaluate the safety and efficacy of maximum-width segmental sacropelvic fixation to correct severe pelvic obliquity in 20 patients with neuromuscular scoliosis (mean age, 13 years).  All 20 patients underwent spinal fusion with instrumentation extending to the pelvis; 14 underwent primary operations; and six had undergone previous spinal fusion above the pelvis requiring extension to the pelvis. The mean preoperative Cobb angle was 84° (range, 56°–135°), corrected to 41° (range, 8°–75°) postoperatively.
At the final follow-up, the mean spinal curve remained at 42° (range, 10°-75°).  The mean preoperative pelvic obliquity was 42° (range, 15°–105°), which was corrected by 78% to 9° (range, 0°-49°) postoperatively, with a pelvic obliquity of 10° (range, 2°-49°) at final follow-up. The authors concluded that maximum-width segmental sacropelvic fixation, utilizing iliosacral screws and/or iliac screws, provides superior correction of severe pelvic obliquity in patients with neuromuscular scoliosis.