Risk Factors of Adjacent Segment Disease After Transforaminal Inter-Body Fusion for Degenerative Lumbar Disease.

Study Design: A retrospective study.

Objective: The purpose of this study was to determine the incidence and risk factors of adjacent segment disease (ASD) after transforaminal inter-body fusion (TLIF) for degenerative lumbar disease.

Summary Of Background Data: ASD is a major complication after spinal fusion. Many reports have been published concerning the risk factors for ASD after TLIF. A number of quantitative relationships to spino-pelvic parameters have been established. A retrospective cohort study was carried out to investigate spino-pelvic alignment in patients with ASD after TLIF.

Methods: This study evaluated 263 subjects (150 subjects undergoing floating fusion (FF group), and 113 patients undergoing lumbosacral fusion (LF group)) who underwent TLIF from 2009 to 2012. The mean follow-up period was 37.6 months. Several parameters were measured using pre- and postoperative full-length free-standing radiographs, including lumbar lordosis (LL), sacral slope (SS), pelvic incidence (PI), pelvic tilt (PT), and PI-LL. Multivariate logistic regression analysis was performed to evaluate these parameters as potential risk factors of early onset radiographic ASD.

Results: Radiographic ASD was found in 65 cases (43.3%) in the FF group, and 49 cases (43.3%) in the LF group. LL improved by 7.5° and 3.9° in each group respectively after TLIF. However, PT worsened by 6.4° in the LF group. When comparing with ASD positive cases and ASD negative cases, a significant difference in preoperative PT was observed in both FF (P = 0.001) and LF groups (P = 0.0001). Logistic regression analysis and receiver operating characteristic analysis revealed that preoperative PT of more than 22.5° was a significant risk factor of the incidence of ASD after TLIF (P = 0.02; odds ratio: 5.1, 95% CI: 1.62-9.03).

Conclusion: Patients with preoperative sagittal imbalance have a statistically significant increased risk of ASD. The risk of ASD incidence was 5.1 times greater in subjects with preoperative PT of more than 22.5°.