Predictors for Minimal Clinically Important Difference after Single Level Anterior Lumbar Interbody Fusion (L5-S1): A Predictive Analysis of Preoperative Radiographic and Clinical Factors.

Introduction: To determine the preoperative predictive factors for minimal clinically important difference (MCID) after single-level L5-S1 ALIF.

Methods: A retrospective analysis was conducted to identify patients who underwent isolated L5-S1 ALIF between 2017-2022. Inclusion criteria were: 1) ≥ one-ye ar clinical follow-up, 2) pre- and postoperative standing scoliosis films, and 3) preoperative MRI. Demographic, clinical, and radiographic data were collected for each patient. Oswestry disability index (ODI) and visual analog scale (VAS) back and leg scores were analyzed pre- and postoperatively for MCID achievement. Patients were classified as achieving MCID if they experienced an improvement by 12.8 points for ODI, 1.2 points for VAS back, or 1.6 points for VAS leg at the last follow-up. Differences between groups were assessed using independent sample t-tests and the Fisher Exact test as appropriate. Binary and multivariable regressions (expressed in odd-ratios [OR]) were performed to determine predictive factors for MCID achievement

Results: Forty-five single-level L5-S1 ALIFs were included in the analysis. Patient demographic distribution exposed a mea n age of 55 ±13 years, a male-female ratio of 25:20, and mean clinical and radiographic follow-ups of 1.6 years (range: 0.95 to 3.96) and 1.8 ±0.47 months. Of these, 36 patients (80%) achieved MCID on one or more PROs. No differences were observed comparing preoperative PROs between groups. Differences in preoperative anterior disc height (ADH: 8.8 ±2.2 vs 11.7 ±4.5, p=0.009), posterior disc height (PDH: 5.42 ±1.57 vs. 4.45 ±1.2, p= 0.049), and foraminal height (FH: 12.2 ±2.6 vs. 14.7±2.2, p=0.01) at L5-S1 was observed between MCID and no MCID groups, respectively. However, only FH: [OR= 0.73, B= -0.43 p=0.02]) and ADH: [OR= 0.64, B= -0.31, p=0.02] were found to be predictors for MCID achievement. Of the 79 variables evaluated, no other exposed predictive relationships.

Conclusion : Our clinical results demonstrate that patients undergoing isolated L5-S1 ALIF with or without posterior instrumentation achieve a high rate of MCID (80%). Decreased preoperative foraminal height and anterior disc height were associated with lower chances of achieving MCID.