INTRODUCTION: With increase in numbers of spinal fusions performed in recent years, adjacent segment degeneration (ASD) has become a concern. Purpose of this study is to evaluate risk factors of radiological ASD in patients with L4 degenerative spondylolisthesis who underwent either anterior lumbar interbody fusion (ALIF) or posterior lumbar interbody fusion (PLIF).
METHODS: Clinical records of 72 patients with L4 degenerative spondylolisthesis treated by single level ALIF (38 patients) or PLIF (34 patients) were reviewed retrospectively. Most ALIF procedures were done before 1995, and PLIF was mostly indicated after 1996. ASD was defined as L3‐4 lesion that was not present preoperatively; 1) loss of disc height of more than 20%, 2) listhesis greater than 3 mm on lateral radiographs. Age, sex, operative procedures (ALIF or PLIF), lamina inclination angle, osteophyte formation, pre‐existing disc degeneration at L3‐4, lordosis angle at fused segment and change in disc height at fused segment were evaluated for potential risk factors related to ASD.
RESULTS: ASD was found in 14(19%) patients. Pre‐existing disc degeneration (p<0.001) and female (p<0.01) was significantly associated with ASD, however, age, operative procedures, lamina inclination angle, osteophyte formation, lordosis angle at fused segment and change in disc height at fused segment were not significantly associated with ASD.
DISCUSSION: Although many risk factors for ASD have been reported, the actual significance of these risks remains uncertain. Our study demonstrated that pre‐existing disc degeneration appear to be a relatively major risk factor of ASD after L4‐5 lumbar fusion for degenerative spondylolisthesis and these data might provide useful information about avoidance of additional surgery.