Pediatric tethered cord syndrome: response of scoliosis to untethering procedures

Abstract

Tethered cord syndrome (TCS) is frequently associated with scoliosis in the pediatric population. Following spinal cord untethering, many patients continue to experience progression of spinal deformity. However, the incidence rate, time course, and risk factors for scoliosis progression following tethered cord release remain unclear. The aim of this study was to determine factors associated with scoliosis progression and whether tethered cord release alone would halt curve progression in pediatric TCS. The authors retrospectively reviewed 27 consecutive pediatric cases of spinal cord untethering associated with scoliosis. The incidence rate and factors associated with scoliosis progression (> 10 degrees increased Cobb angle) after untethering were evaluated using the Kaplan-Meier method. The mean age of the patients was 8.9 years. All patients underwent cord untethering for lower-extremity weakness, back and leg pain, or bowel and bladder changes. Mean +/- SD of the Cobb angle at presentation was 41 +/- 16 degrees . The cause of the spinal cord tethering included previous myelomeningocele repair in 14 patients (52%), fatty filum in 5 (18.5%), lipomeningocele in 3 (11%), diastematomyelia in 2 (7.4%), arthrogryposis in 1 (3.7%), imperforate anus with an S-2 hemivertebra in 1 (3.7%), and lipomyelomeningocele with occult dysraphism in 1 (3.7%). Mean follow-up was 6 +/- 2 years. Twelve patients (44%) experienced scoliosis progression occurring a median of 2.4 years postoperatively and 8 (30%) required subsequent fusion for progression. At the time of untethering, scoliosis < 40 degrees was associated with a 32% incidence of progression, whereas scoliosis > 40 degrees was associated with a 75% incidence of progression (p < 0.01). Patients with Risser Grades 0-2 were also more likely to experience scoliosis progression compared with Risser Grades 3-5 (p < 0.05). Whereas nearly all patients with Risser Grades 0-2 with curves > 40 degrees showed scoliosis progression (83%), 54% of patients with Risser Grades 0-2 with curves < 40 degrees progressed, and no patients with Risser Grades 3-5 with curves < 40 degrees progressed following spinal cord untethering. In this experience with pediatric TCS-associated scoliosis, patients with Risser Grades 3-5 and Cobb angles < 40 degrees did not experience curve progression after tethered cord release. Patients with Risser Grades 0-2 and Cobb angles > 40 degrees were at greatest risk of curve progression after cord untethering. Pediatric patients with TCS-associated scoliosis should be monitored closely for curve progression using standing radiographs after spinal cord untethering, particularly those with curves > 40 degrees or who have Risser Grades 0-2.