Progression of Coronal Cobb Angle After Short-Segment Lumbar Interbody Fusion in Patients with Degenerative Lumbar Stenosis.

OBJECTIVE: The progression of scoliosis after fusion surgery is a poor prognostic factor of long-term outcomes in patients with degenerative lumbar stenosis (DLS). In this study we aimed to investigate changes in coronal alignment and identify risk factors related to progression of scoliosis after fusion.

METHODS: There were 540 patients with symptomatic DLS treated by short-segment lumbar fusion surgery. Among them, 50 patients had coronal Cobb angles >10° at the final follow-up. Sixteen patients had increases >5° (progression group), and 34 patients had increases <5° (nonprogression group). Radiologic parameters that may affect the progression of scoliosis were compared.

RESULTS: The mean progression of the Cobb angle was 7.92° in the progression group and 1.25° in the nonprogression group. The progression group had significantly longer follow-up periods and a lower preoperative Cobb angle. The apical vertebra (AV) of the major curve was more frequently thoracic in the progression group. Progression of the Cobb angle was correlated with the follow-up period, preoperative Cobb angle, and location of the AV. Multivariate regression analysis showed that progression of the Cobb angle was significantly associated with a lower preoperative Cobb angle, and both facet degeneration of the upper instrumented vertebra at the fusion site and vertebral spur formation on the concave side also appeared to be associated with progression of the Cobb angle.

CONCLUSIONS: The global magnitude of progression of the Cobb angle after short-segment lumbar fusion surgery in patients with DLS is similar to the natural curve progression of adult degenerative scoliosis.