Introduction: This study aims to evaluate operative factors potentially associated with occurrence of adjacent segment disease (ASD) after elective single-level lumbar fusion for degenerative spinal disease.
Methods: A retrospective review was performed on patients who underwent single-level lumbar fusion for stenosis, spondylolisthesis or disc degeneration between 2007 and 2016. Patients without follow-up were excluded from the study. Effects of demographic (age, gender, smoking status, osteoporosis, diebetes) and technical factors (surgical approach, type of procedure, performing decompression in any segments without fusion, type of bone graft) on ASD rates were analyzed.
Results: 369 patients met our inclusion criteria, 83 (22.5%) of whom were re-operated for ASD. Mean follow-up was 3.24 years, and mean time to ASD was 5.69 years. Univariate analysis showed significant association of using combined autograft and allograft with lower rates of ASD (P=0.016), and there was a tendency towards significance for anterior interbody fusion approach (P=0.052), discectomy (P=0.057), and unfused decompression adjacent to the fused segment (P=0.120). There was no statistically significant association between fusion technique (pedicular screw only vs. interbody fusion only vs. both), surgical approach (anterior vs. posterior vs. circumferential), smoking, osteoporosis or diabetes and ASD. Multivariate analysis identified that presence of unfused decompression adjacent to the fused segments (OR=2.84, P=0.030), anterior interbody fusion (OR=0.13, P=0.007) and combined use of bone autograft and allograft (OR=0.37, P<0.001) were associated with ASD rate.
Conclusions: No difference in ASD rates was identified between pedicular screw fixation with and without interbody fusion. However, unfused decompression of the adjacent levels was associated with higher ASD rates. When interbody fusion was performed, anterior approach was associated with lower ASD rates. Lastly, use of combined autograft and allograft was associated with lower ASD rates.
Patient Care: This research identifies technical details regarding single-level lumbar spinal fusion, which should be highlighted and can be improved upon in the future, to decrease risk of adjacent segment disease.
Learning Objectives: By the conclusion of this session, participants should be able to: 1) Describe the factors predicting adjacent segment disease after single-level lumbar fusion for degenerative spinal disease; 2) Discuss, in small groups which operative techniques may influence ASD rates; 3) Identify an effective management plan for degenerative spinal disease to potentially decrease ASD rates.