Factors associated with favorable outcomes of floating fusion or lumbosacral spinal fusion in adult spinal deformity surgery: an analysis of the incidence of mechanical complications from a multicenter study.

PURPOSE: Lumbosacral fusion (LSF) is the standard approach in adult spinal deformity (ASD) surgery but is frequently associated with proximal junctional kyphosis. Floating fusion (FF) has been proposed as an alternative approach. This study examined factors influencing the selection of FF and identified postoperative adverse factors associated with each surgical approach.

METHODS

This multicenter study retrospectively reviewed the records of patients who underwent surgery for ASD. They were divided into FF and LSF groups and compared by baseline patient characteristics and radiological parameters. Each group was further divided and compared according to mechanical complications (MC).

RESULTS

The number of fusion levels (odds ratio [OR] = 0.50, 95% confidence interval [CI]: 0.41-0.61, P < 0.01), thoracic kyphosis (OR = 1.03, 95% CI: 1.00-1.06, P = 0.045), and lower lumbar lordosis (LL) (OR = 1.07, 95% CI: 1.03-1.10, P < 0.01) were independently associated with FF. In FF, the correction amounts for LL and PI - LL were lower in the MC subgroup (LL: no MC, 9.3 ± 12.5; MC, 2.1 ± 16.1, P = 0.04 and PI - LL: no MC, - 10.6 ± 12.3; MC, - 2.1 ± 14.1, P = 0.02). In LSF, the preoperative SVA was higher in the MC subgroup (no MC, 82.5 ± 55.4; MC, 103.1 ± 46.7; P = 0.049).

CONCLUSION

FF outcomes were more favorable in patients undergoing short-segment fusion who retained TK or lower lumbar lordosis. Various procedural demands influenced postoperative MC: FF requires LL proportional to the PI, whereas LSF focuses on global alignment correction.