Laminectomy Adjacent to Instrumented Fusion Increases Adjacent Segment Disease.

STUDY DESIGN: Retrospective cohort.

OBJECTIVE: To determine if performing a simultaneous laminectomy at an unfused level adjacent to an instrumented fusion increases the risk of adjacent segment disease(ASD).

SUMMARY OF BACKGROUND DATA: Laminectomy adjacent to instrumented fusion has uncertain outcomes. The increased mechanical forces at the unfused laminectomy may lead to more ASD. Few studies have examined the development of ASD with regards to laminectomy performed adjacent to instrumented fusions.

METHODS: 789 patients underwent instrumented lumbar fusion and laminectomy at the same level(s) (n=676) or with an additional adjacent level laminectomy (n=113) with a minimum of 2-year follow-up. Diagnoses were degenerative spondylosis (n=241), degenerative spondylolisthesis (n=485) and isthmic spondylolisthesis (n=63) in addition to central stenosis. Primary outcome measures included development of ASD, time to development of ASD, revision surgery, and time to revision surgery.

RESULTS: The adjacent laminectomy group developed ASD at a significantly greater rate of 57.5% (n=65), compared with 35.2% (n=238) of the non-adjacent laminectomy group (P<0.001). Revision surgery rate was also greater in the adjacent laminectomy group (22.1% v 13.5%, P<0.001). There was no difference in time to revision surgery (31.1 v 32.6 mo, P=0.71) or time to ASD development (31.2 v 32.3 mo, P=0.72). ODI and VAS scores did not differ, nor did patient baseline demographics including sex, BMI, Charleston Comorbidity Index, and tobacco use. The exception was the adjacent laminectomy group average age was 67.6 while the non-adjacent laminectomy group average age was 62.3 (P<0.001). However, age was not found to be an independent predictor of ASD development (P=0.44).

CONCLUSION: Surgeons should be cautious when performing a laminectomy adjacent to an instrumented fusion, as this increases the rate of ASD as well as revision surgery.