Surgical treatment for severe and rigid scoliosis: a case-matched study between idiopathic scoliosis and syringomyelia-associated scoliosis

Background Context Treatment guidelines for severe and rigid syringomyelia-associated scoliosis (SRSMS) are limited. Typically, surgeons apply practice guidelines for severe and rigid idiopathic scoliosis (SRIS) to treat SRSMS. No study has directly compared the results of surgical treatment between patients with SRSMS and those with SRIS. Purpose The present study was performed to compare the outcomes of surgical correction of SRSMS and SRIS from clinical and radiographic perspectives. Study Design This is a retrospective, case-matched, single-center, institutional review board-approved study. Patient Sample A total of 26 patients with SRSMS or SRIS treated by an anterior and posterior vertebral column resection approach or an internal distraction approach were enrolled. Outcome Measures The SRSMS and SRIS groups were compared on the following variables: fusion length, screw number, operation time, estimated blood loss, follow-up duration, different radiological parameters (including main thoracic curve, cranial compensatory curve, caudal compensatory curve, thoracic kyphosis, lumbar lordosis, thoracic apical vertebral translation, coronal balance, and sagittal vertical axis), Scoliosis Research Society (SRS)-22 scores, and complication rate. Methods Thirteen patients with SRSMS were matched with patients with SRIS on curve magnitude, the flexibility of the main curve, surgical procedure, age, and gender. All patients had a minimum of 2 years of follow-up. The radiographic parameters and demographic data from patients were evaluated before surgery, immediately after surgery, and at the latest follow-up. Results The case matches were relatively ideal except one pair with the main curve in the opposite direction. There was no significant difference in fusion length, screw number, operation time, estimated blood loss, or follow-up duration between the two groups. No significant differences were found between the two groups in the main curve or caudal compensatory curve before surgery, immediately after the operation, or at the final follow-up. The correction of thoracic apical vertebral translation in the SRIS group was better than that in the SRSMS group. The SRSMS group had a larger preoperative, postoperative, and final follow-up cranial compensatory curve and a lower correction rate than did the SRIS group. There was no significant difference in preoperative coronal balance between the two groups. After surgery, the coronal balance in the SRSMS and SRIS groups averaged 24.4±13.2 mm and 12.1±7.9 mm, respectively, which was significantly different (p=.04). At the most recent follow-up, the coronal balance in the SRSMS group improved to 14.8±12.6 mm, and it was 11.8±8.6 mm in the SRIS group. No significant difference was found between the two groups (p=.56). There was no significant difference in thoracic kyphosis, lumbar lordosis, or sagittal vertical axis before surgery, immediately after the operation, or at the final follow-up. Before surgery and at the final follow-up, the two groups had similar scores on function, pain, self-image, mental health, and satisfaction. There was no significant difference in complication rates between the two groups. Conclusions Typically, surgical correction outcomes are similar in patients with SRSMS and SRIS. Patients with SRIS tended to have a smaller cranial compensatory curve and better correction of the cranial compensatory curve and thoracic apical vertebral translation. Patients with SRSMS tended to have a higher proportion and greater amount of postoperative coronal imbalance, which may be improved during follow-up.