INTRODUCTION: Selection of fusion levels remains controversial in the surgical treatment of degenerative lumbar scoliosis. We reviewed radiographic and clinical outcomes of posterior short‐segment fusion for degenerative lumbar scoliosis, and analyzed risk factors for postoperative curve progression and decompensation.
METHODS: 51 patients who had undergone instrumented posterior short‐segment fusion for degenerative lumbar scoliosis were reviewed retrospectively. Number of fusion levels were 1.6 segments on average, and mean follow‐up period was 23 months. Radiographic parameters were assessed using standing whole spine radiographs, which included Cobb angle of scoliosis, progression of residual curve, lateral slip and tilt of vertebra proximal to fusion, plumb line deviation, and fusion status. Clinical outcomes were evaluated using JOA score.
RESULTS: Mean Cobb angle was 16.1 degrees preoperatively, 9.8 degrees immediate postoperatively, and 15.1 degrees at the final follow‐up. Fusion rate was 96%. JOA score was 14/29 before surgery, which improved to 22/29 immediately after surgery and 20/29 at the final follow‐up. Residual scoliosis was 8.1 degrees immediately after surgery, and 16.5 degrees at the final follow‐up. More than 10 degrees of curve progression were observed in five patients (10%), who showed poor clinical outcomes (JOA score=13/29). Multiple logistic regression analysis demonstrated that anterior deviation of plumb line (p=0.03, odds ratio=1.05) and lateral tilt of proximal vertebra (p=0.07, odds ratio=1.33) were related to curve progression. Relative risk for curve progression increased 4.9 times by 30 mm of anterior deviation of plumb line, and 4.1 times by 5 degrees of lateral tilt of proximal vertebra.
DISCUSSION: Although degenerative lumbar scoliosis was successfully treated in 90 % by posterior short‐segment fusion, larger anterior deviation of plumb line and lateral tilt of proximal vertebra were risk factors for curve progression and decompensation. We recommend that vertebra with more than 10 degrees of lateral tilt should be included into fusion levels.