L5-S1 Pseudoarthrosis Rate with ALIF Versus TLIF in Adult Spinal Deformity Surgeries: A Retrospective Analysis of 100 Patients.

OBJECTIVE: Lumbosacral pseudoarthrosis is a common complication following adult spine deformity (ASD) surgery. This study assessed the reoperation rate for L5-S1 pseudoarthrosis in the ASD population. Compared with transforaminal lumbar interbody fusions (TLIFs), we hypothesized that anterior lumbar interbody fusion (ALIF) would result in lower rates of L5-S1 pseudarthrosis. METHODS: This is a single center study with patient data retrieved from a prospective ASD database. The patients had a long-segment fusion, ALIF or TLIF at the L5-S1 level with a 2-year follow-up and were divided into 2 groups (TLIF and ALIF). The study's primary outcome was to assess the difference in the reoperation rate for clinical pseudoarthrosis between the TLIF and the ALIF groups. The secondary outcomes measured the radiological pseudoarthrosis rate and identified risks for L5-S1 pseudoarthrosis development. RESULTS: A total of 100 patients were included; 49 patients (mean age, 62.9 years; 77.5% females) were in TLIF and 51 patients (mean age, 64.4 years; 70.6% females) were in the ALIF group. Baseline characteristics were similar in both groups. Thirteen (13%) patients with L5-S1 pseudoarthrosis required reoperation. Clinical pseudoarthrosis was higher in the TLIF group than in the ALIF group (12/49 vs. 1/51; P < 0.001). Univariate analysis demonstrated a higher risk of L5-S1 pseudoarthrosis with TLIF than ALIF (risk ratio, 12.4; 95% confidence interval: 1.68-92.4; P < 0.001). Multivariate analysis revealed 4.86 times the risk of L5-S1 clinical pseudoarthrosis with TLIF than with ALIF (risk ratio, 4.86; 95% confidence interval 0.57-47; P = 0.17), but this ratio did not reach statistical significance. CONCLUSIONS: No difference in reoperation risk for L5-S1 pseudarthrosis was observed based on the method of IF. rhBMP-2 was noted as a significant predictor.