EFFECTS ON ADJACENT SEGMENT AFTER MINIMUM FIVE-YEARS FOLLOWING INSTRUMENTED LUMBAR SPINAL FUSION IN INDIAN POPULATION

Abstract

Adjacent segment degeneration [ASD] after instrumented lumbar spinal fusion has been studied extensively in non-Indian population. Present study attempts to evaluate incidence of and factors predisposing to ASD in the Indian population. This was a retrospective study with the inclusion criteria being: patients who underwent lumbar spinal fusion for spondylolisthesis, trauma, infection or deformity with a minimum five-year follow-up. Exclusion criteria: postoperative iatrogenic surgical-site infections, revision surgeries, postoperative implant failure and pseudarthrosis. Radiographs reviewed immediate postoperatively, and at final follow-up. Global lumbar lordosis from L1-S1; and angulation and translation of spinal motion segment immediately adjacent [cranial and caudal] to fused segment were studied. ASD was defined using White and Panjabi’s criteria. At final follow-up, VAS for lower back as well as lower limbs was noted separately along with walking distance. Twenty patients [49.4+17.4years] included [six males, fourteen females]. ASD was seen in 13 of 20 [65%] patients. Age>50years at the time of surgery and global lumbar lordosis <40° in the immediate postoperative period were identified as significant risk factors for ASD [p=0.02 and 0.03, respectively]. However, no significant correlation was noted between development of ASD and extension of fusion to sacrum. Nor was there any correlation between ASD and gender or length of fusion. It was also notable that no significant differences were identified in VAS scores and walking distance between patients with and without ASD. To conclude, among the various factors studied, age>50years at the time of surgery and immediate postoperative global lumbar lordosis <400 were significantly associated with development of ASD after a minimum follow-up of five years.