Spring distraction system to correct early onset scoliosis: 2 year follow-up results from 24 patients.

Current surgical treatment options for Early Onset Scoliosis (EOS), with distraction- or growth-guidance systems, show limited growth and high complication rates. We developed the Spring Distraction System (SDS), which does not have to be periodically lengthened and which provides continuous corrective force to stimulate spinal growth. This study aimed to assess curve correction and maintenance, spinal growth, and complication rate following SDS treatment. All primary- and revision patients (conversion from failed other systems) with SDS and ≥2 years follow-up were included. Outcome measures were coronal Cobb angle, sagittal parameters, spinal length measurements and complications and re-operations. Radiographic parameters were compared pre-operatively, post-operatively and at latest follow-up. Spinal length increase was expressed as mm/year. Twenty-four skeletally immature EOS patients (18 primary and 6 revision cases) were included. There were 5 idiopathic, 7 congenital, 3 syndromic and 9 neuromuscular EOS patients. Mean age at implantation was 9.1 years (primary: 8.4; conversion: 11.2). Major curve improved from 60.3° to 35.3°, and was maintained at 40.6° at latest follow-up. Mean spring length increase during follow-up was 10.4mm/year. T1-S1 length increased 13.6mm/year and the instrumented segment length showed a mean increase of 0.8mm/segment/year. In total, 17 re-operations were performed. Ten re-operations were performed to treat 9 implant-related complications. In addition, 7 patients showed spinal growth that exceeded expected growth velocity; their springs were re-tensioned during a small re-operation. Spring distraction may be feasible as an alternative to current growing spine solutions. Curve correction and growth could be maintained satisfactory without the need for repetitive lengthening procedures. Complications and re-operations could not be prevented, which emphasizes the need for further improvement.