PURPOSE: Preoperative planning for lumbar fusion involves careful consideration of segmental and regional spinopelvic alignment. However, whether anterior lumbar interbody fusion (ALIF) reliably delivers planned lordosis is incompletely understood. The purpose of this study was to evaluate the ability of L5-S1 ALIF to restore regional L4-S1 and segmental L5-S1 lordosis according to preoperative plan.
METHODS: Adult patients who underwent L5-S1 ALIF with posterior fusion by a single surgeon, had a documented preoperative plan, and received UNiD patient-specific rods were included. Demographics, preoperative and 3-month postoperative spinopelvic alignment, and deviation from ideal postoperative alignment were assessed. Two one-sample t-tests (TOST) were performed to evaluate equivalence of planned and postoperative lordosis. Sub-analysis by L4-L5 correction status (no fusion, screws, interbody) was also performed.
RESULTS: Among 102 patients, mean age was 61.2 years, 45% were female, mean levels fused were 4.5. Preoperatively, mean PI-LL was 10.8°, SVA was 61.6 mm, L4-S1 was 29.8°, L5-S1 was 11.2°, and L4-S1 LDI was 63%. Postoperatively, mean PI-LL was corrected to 6.4°, SVA to 33.5 mm, L4-S1 to 38.3°, L5-S1 to 20.7°, and L4-S1 LDI to 79%, and reciprocal TK change was 8.3° (all p < 0.05). Mean L4-S1 lordosis was 1.1° below plan and L5-S1 lordosis was 0.8° above plan (p > 0.05). TOST testing revealed that mean plan-achieved difference for L4-S1 and L5-S1 lordosis were statistically equivalent within the predefined equivalence margin of ± 2.5° (p < 0.05). In total, 76% and 95% of ideally planned patients achieved at least 35° L4-S1 lordosis and 50% L4-S1 LDI postoperatively, respectively. Fusion approach at L4-L5 was not associated with postoperative L4-S1 lordosis or plan success (p > 0.05).
CONCLUSION: L5-S1 ALIF delivers reliable early correction of regional L4-S1 and segmental L5-S1 lordosis that closely matches preoperative planning parameters, regardless of fusion technique at L4-L5. The reliability of other fusion techniques at L4-S1 to achieve planned lordosis should be similarly examined.
LEVEL OF EVIDENCE: IV.
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