Factors affecting Reduction of Slippage in Posterolateral Fusion for Spondylolytic Spondylolisthesis / 대한척추외과학회지

ABSTRACT

STUDY DESIGN: A retrospective study. OBJECTIVES: The purpose of this study was to analyze the reduction of spondylolisthesis after postural reduction and pedicle screw instrumentation for low-grade spondylolytic spondylolisthesis, and to determine the factors affecting reduction. MATERIALS AND METHODS: Twenty patients (mean age 52.5 years old; range, 30-71 years old), who underwent pedicle screw instrumentation and posterolateral fusion after wide laminectomy and facetectomy, were reviewed. The minimum follow-up period was 2 years. The percentage of slippage was measured on lateral radiographs by the Taillard method. We measured the slip angle, sacral inclination, lumbar lordosis, disc height, and angulation and translation on flexion-extension stress views. These radiological parameters were analyzed statistically for correlation with the reduction of slippage. RESULTS: In these passive reduction surgeries, no forceful reduction was attempted. The average percentage of slippage was 20.6% preoperatively, 13.0% after instrumentation, and 19.5% at the last visit. The reduction of slippage had a correlation with hypermobile angulation on flexion-extension radiographs (p=0.02). There were no significant correlations between the amount of reduction and translation on flexion-extension radiographs (P=0.99), slip angle (P=0.79), disc space height (P=0.6), lumbar lordosis (P=0.68), and sacral inclination (P=0.35). CONCLUSION: Loss of reduction that was achieved by postural reduction with pedicle screw instrumentation for spondylolytic spondylolisthesis occurred at the final follow-up. There was a negative correlation between the reduction of slippage and hypermobile angulation on flexion-extension dynamic radiographs.