Clinical and radiological outcomes of selective fusion for rotatory olisthesis in degenerative lumbar scoliosis: a retrospective cohort study.

Study design: Retrospective cohort study.

Purpose: To investigate the long-term clinical and radiological outcomes of selective fusion for rotatory olisthesis (RO) in degenerative lumbar scoliosis (DLS).

Overview of literature: DLS is often associated with RO, and selective fusion of RO is a common surgical treatment option. However, the clinical and radiological outcomes remain controversial.

Methods: A cohort of 54 consecutive patients with DLS and RO was included in the study. All the included patients underwent selective RO fusion and at least 2 years of follow-up. They were divided into two groups: group 1 with a curve <30° and group 2 with a curve ≥30°. The clinical outcomes were evaluated by the Oswestry Disability Index (ODI) and Numerical Rating Scale. The radiological assessment included RO location, offset and subluxated-disc orientation, Cobb angle, and coronal as well as sagittal alignments.

Results: The offset value was greater in group 2 than in group 1 (13.4±4.7 mm vs. 9.3±3.5 mm, p<0.001). The subluxated disc was mainly oriented to the concave side in group 2 (15/21) but to the convex side in group 1 (20/33) (p =0.022). Group 2 had a higher rate of postoperative adjacent RO than group 1 (14/21 vs. 1/33, p<0.001). The ODI was comparable between both groups preoperatively but higher at the final follow-up in group 2 (34.9±9.5) than in group 1 (24.4±6.2). In the multiple logistic regression analysis, the thoracolumbar/lumbar curve was identified as the risk factor for postoperative adjacent RO (odds ratio, 1.400; p=0.007). The receiver operating characteristic analysis verified it with an area under the curve of 0.960 (p<0.001).

Conclusions: The clinical and radiological outcomes were maintained well in group 1 but not in group 2. Selective RO fusion in DLS with a lumbar curve <30° is a rational option. However, it should be avoided in those with a lumbar curve >30° because of a higher complication rate and a worse clinical outcome at the final follow-up.