The impact of increasing interbody fusion levels at the fractional curve on lordosis, curve correction, and complications in adult patients with scoliosis.

Objective: Radiculopathy from the fractional curve, usually from L3 to S1, can create severe disability. However, treatment methods of the curve vary. The authors evaluated the effect of adding more levels of interbody fusion during treatment of the fractional curve.

Methods: A single-institution retrospective review of adult patients treated for scoliosis between 2006 and 2016 was performed. Inclusion criteria were as follows: fractional curves from L3 to S1 > 10°, ipsilateral radicular symptoms concordant on the fractional curve concavity side, patients who underwent at least 1 interbody fusion at the level of the fractional curve, and a minimum 1-year follow-up. Primary outcomes included changes in fractional curve correction, lumbar lordosis change, pelvic incidence - lumbar lordosis mismatch change, scoliosis major curve correction, and rates of revision surgery and postoperative complications. Secondary analysis compared the same outcomes among patients undergoing posterior, anterior, and lateral approaches for their interbody fusion.

Results: A total of 78 patients were included. There were no significant differences in age, sex, BMI, prior surgery, fractional curve degree, pelvic tilt, pelvic incidence, pelvic incidence - lumbar lordosis mismatch, sagittal vertical axis, coronal balance, scoliotic curve magnitude, proportion of patients undergoing an osteotomy, or average number of levels fused among the groups. The mean follow-up was 35.8 months (range 12-150 months). Patients undergoing more levels of interbody fusion had more fractional curve correction (7.4° vs 12.3° vs 12.1° for 1, 2, and 3 levels; p = 0.009); greater increase in lumbar lordosis (-1.8° vs 6.2° vs 13.7°, p = 0.003); and more scoliosis major curve correction (13.0° vs 13.7° vs 24.4°, p = 0.01). There were no statistically significant differences among the groups with regard to postoperative complications (overall rate 47.4%, p = 0.85) or need for revision surgery (overall rate 30.7%, p = 0.25). In the secondary analysis, patients undergoing anterior lumbar interbody fusion (ALIF) had a greater increase in lumbar lordosis (9.1° vs -0.87° for ALIF vs transforaminal lumbar interbody fusion [TLIF], p = 0.028), but also higher revision surgery rates unrelated to adjacent-segment pathology (25% vs 4.3%, p = 0.046). Higher ALIF revision surgery rates were driven by rod fracture in the majority (55%) of cases.

Conclusions: More levels of interbody fusion resulted in increased lordosis, scoliosis curve correction, and fractional curve correction. However, additional levels of interbody fusion up to 3 levels did not result in more postoperative complications or morbidity. ALIF resulted in a greater lumbar lordosis increase than TLIF, but ALIF had higher revision surgery rates.