Correlation of Adjacent Segmental Disease with Tilt Angles of the Upper and Lower Instrumented Vertebra in the Degenerative Lumbar Scoliosis

Abstract

Study Design: Retrospective study. Objectives: To evaluate the correlation of adjacent segmental disease with tilt angles of the upper and lower instrumented vertebra after instrumented posterolateral fusion for degenerative lumbar scoliosis. Summary of Literature Review: There has been no study of radiologic measurement and decision of fusion level using the angle of pedicle screws inserted for treatment of degenerative lumbar scoliosis. Materials and Methods: From 2004 to 2008, 74 patients that underwent decompression and posterolateral fusion for degenerative lumbar scoliosis were included in this study. In all cases, instrumentation and posterolateral fusion were both performed. The sex ratio was 31:43, the mean age was 68.7 years and the mean follow up duration was 37.4 months. The angle between each upper end plate of the upper vertebral body and lower end plate of the lower vertebral body of the fusion, and the line parallel to the axis of the sagittal line of vertebrae was each defined as UIV-a and LIV-b. The correlation of development of adjacent segment disease and UIV-a, and LIV-b angle was investigated. Results: Sum of the absolute value of UIV-a and LIV-b had a statistically significant positive correlation with that of adjacent segment disease. Also, UIV-a alone, had a statistically positive correlation with the development of proximal adjacent segment disease. Conclusions: Since it is proven that adjacent segment disease has positive correlation with the sum of the absolute value of UIV-a and LIV-b, the extent of fusion should be adjusted to make the line parallel to the line perpendicular to the sagittal surface.