Analysis of Rod Fracture at the Lumbosacral Junction Following Surgery for Adult Spinal Deformity.

Study design: Retrospective study.

Purpose: This study aimed to investigate the differences in the characteristics of patients with rod fracture (RF) at the lumbosacral junction from those without RF following adult spinal deformity (ASD) surgery.

Overview of literature: RF is a major complication following ASD surgery and may require reoperation because of pain and correction loss. The lumbosacral junction is a common RF site. However, risk factors for RFs at the lumbosacral junction remain unknown.

Methods: The study included data from 100 patients who underwent ASD surgery between 2012 and 2020. Fifteen of these patients presented with RFs. Patient demographics, clinical outcomes, and radiographic parameters were evaluated in each group.

Results: RFs were significantly more frequent in patients with a medical history of total hip arthroplasty (THA; p=0.01) or severe obesity (p=0.04). However, no significant differences in clinical outcomes, preoperative or postoperative measurements, or changes were found between pre- and postoperative radiographic parameters within the groups. Both pre- (p=0.01) and postoperative (p=0.02) anterior disc heights were significantly greater in the RF group than in the non-RF group. In the RF group, the postoperative lordotic angles of the lumbosacral junction significantly decreased compared with preoperative angles (p=0.02). Multiple logistic regression analysis demonstrated that a THA history (odds ratio, 34.2), severe obesity (odds ratio, 14.0), and preoperative anterior disc height (odds ratio, 1.2) were significant risk factors for RFs.

Conclusions: In this study, the greatest risk factors for postoperative lumbosacral RF after ASD surgery were THA history, severe obesity, and postoperative anterior disc height of ≥10. For patients at higher risk, the use of multirods is considered necessary.