L5-S1 Transforaminal Lumbar Interbody Fusion (TLIF) Is Associated with Increased Revisions Compared to L4-L5 TLIF at Two Years.

STUDY DESIGN: Retrospective cohort study.

OBJECTIVE: Compare outcomes in patients undergoing one-level transforaminal lumbar interbody fusion (TLIF) at L4-S1.

BACKGROUND: TLIF is frequently performed at L4-S1 to treat degenerative lumbar pathologies. However, the native alignment and biomechanics differ across L4-L5 and L5-S1, and there is limited data regarding comparative radiographic outcomes.

METHODS: Patients who underwent one-level TLIF at L4-L5 or L5-S1 at a single academic institution were identified. Baseline demographics, procedural characteristics, change in postoperative spinopelvic alignment and patient-reported outcome measures (PROMs), and two-year postoperative surgical complications were compared. Multivariate regression analyses, accounting for age, gender, Charlson Comorbidity Index (CCI), and body mass index (BMI), were also performed.

RESULTS: Across the 175 included patients, 125 had L4-L5 TLIF and 50 had L5-S1 TLIF. The mean age was 57.8 years, 56.6% were female, mean CCI was 0.9, and mean follow-up was 26.7 months. In the hospital, the two cohorts were not statistically different with regards to EBL and LOS. Two years postoperatively, multivariate linear regression analyses revealed that L5-S1 TLIF achieved 6.0° higher correction in L4-S1 lordosis ( P =0.012) than L4-L5 TLIF. At the same time, however, L5-S1 TLIF patients experienced significantly higher rates of pseudoarthrosis (8.0% vs 1.6%, P =0.036) and subsequent spine surgery (18.0% vs. 7.2%, P =0.034), specifically for pseudoarthrosis (6.0% vs. 0.0%, P =0.006), with this cohort having 8.7 times higher odds of subsequent spine surgery for pseudoarthrosis ( P =0.015) than L4-L5 TLIF patients on multivariate logistic analyses. PROMs, on the other hand, were not different across the two cohorts.

CONCLUSIONS: Although L5-S1 TLIF yielded good radiographic correction, it was associated with higher rates of subsequent spine surgery for pseudoarthrosis compared to L4-L5 TLIF. These findings may be related to differences in native segmental alignment and biomechanics across the L4-L5 and L5-S1 motion segments and are important to consider during surgical planning.

LEVEL OF EVIDENCE: IV.