Minimally Invasive Lateral Lumbar Interbody Fusion Shows a Lower Incidence of Radiologic Adjacent Segment Pathology Than Conventional Posterior Lumbar Interbody Fusion.

BACKGROUND

Radiologic adjacent segment pathology (R-ASP) is a significant consequence following lumbar spinal fusion, potentially resulting from compromised integrity of posterior structures. Few studies have directly compared the incidence of R-ASP between minimally invasive lateral lumbar interbody fusion (LLIF) and conventional posterior lumbar interbody fusion (PLIF). Thus, the objective of this study was to analyze risk factors for R-ASP and compare clinical outcomes between minimally invasive LLIF supplemented with percutaneous pedicle screw fixation and open conventional PLIF.

METHODS

This study included 107 patients who underwent one- or two-segment spinal fusion for degenerative lumbar disease. Fifty-one patients underwent minimally invasive LLIF and 56 received conventional PLIF. Factors related to occurrence of R-ASP were investigated by analyzing demographic profiles, radiological results, and clinical outcomes. Correlations between clinical results were determined based on fusion methods and the presence of R-ASP. Patient-related factors, preoperative spinal diagnosis, number of fused segments, and radiologic findings were analyzed. Clinical outcomes were also assessed. Cox regression survival analysis was performed to determine risk factors for R-ASP. Annual incidence and cumulative survival rate of R-ASP were calculated using the life-table method and Kaplan-Meier survival curve.

RESULTS

Cox proportional hazards regression analysis identified three significant risk factors for R-ASP: PLIF over LLIF (P = 0.028; hazard ratio [HR], 2.321; 95% confidence interval [CI], 1.096-4.913), postoperative pelvic incidence-lumbar lordotic angle mismatch ≥ 10° (P = 0.022; HR, 2.280; 95% CI, 1.126-4.617), and preoperative facet arthropathy grade ≥ 2 (P = 0.016; HR, 3.491; 95% CI, 1.266-9.629). The predicted incidence of R-ASP was 48.7% (95% CI, 42.1-55.2%) at 5 years post-fusion and 80.7% (95% CI, 73.0-88.5%) at 8 years. Clinical outcomes showed that the final visual analog scale for lower back pain was significantly lower in patients who underwent LLIF and in patients who did not develop R-ASP.

CONCLUSION

Minimally invasive fusion techniques that preserve posterior structures might slow the progression of degenerative changes in adjacent segments. To reduce R-ASP, preoperative assessment of facet degeneration and adequate restoration of sagittal balance during surgery are crucial considerations.