Risk factors for screw loosening in patients with lumbar degenerative spondylolisthesis treated with Dynesys dynamic stabilization.

Abstract

Background: Posterior decompression with Dynesys dynamic stabilization (DDS) is an effective treatment option for degenerative spondylolisthesis. However, postoperative pedicle screw loosening (PSL) often results in poor outcomes. Determining possible risk factors may aid in making informed decisions. This study aimed to evaluate the incidence and risk factors for PSL in patients who underwent elective DDS.

Methods: We conducted a retrospective analysis of 94 patients with L4-L5 grade I degenerative spondylolisthesis who underwent DSS at a single academic institution between May 2008 and February 2015. Screw loosening was defined as the presence of a halo or double-halo sign on plain radiography.

Results: The rate of screw loosening was 4.8% among screws and 11.7% among patients. Multivariable analysis revealed that age >65 years, smoking, segmental range of motion (ROM) >13°, and L1 vertebral body Hounsfield unit <110 were risk factors for PSL after DDS. Five reoperations were performed; however, no instances of screw breakage were observed.

Conclusion: Our study identified risk factors for PSL after DDS, including older age, smoking, larger preoperative segmental ROM, and lower L1 vertebral body HU, which could assist in preoperative decision-making and surgical planning.