Risk of total hip arthroplasty following lumbar fusion surgery in a nationwide cohort study.

Alterations in spinopelvic alignment following lumbar fusion surgery (LFS) have been suggested to influence hip biomechanics, yet long-term population-based evidence regarding the risk of total hip arthroplasty (THA) remains limited. Using a nationwide cohort from the Korean National Health Insurance Service, we conducted a retrospective study applying a 3-year washout period and up to 10 years of follow-up. Patients who underwent LFS with deformity correction or sacropelvic fixation were propensity score-matched to individuals without LFS. The primary outcome was incident THA, while total knee arthroplasty (TKA) was evaluated as a comparison outcome. Cox proportional hazards models were used to estimate adjusted hazard ratios, with subgroup analyses performed according to age, sex, body mass index, and income. Patients undergoing LFS showed a significantly increased risk of THA compared with matched controls (adjusted hazard ratio 2.26; 95% confidence interval 1.33-3.82), with greater risk observed among older adults, women, individuals with higher body mass index, and those with higher income. In contrast, the association between LFS and TKA was weaker and not statistically significant. These findings suggest that the hip joint may be particularly vulnerable to biomechanical changes following lumbar fusion, highlighting the importance of long-term monitoring of hip health in patients undergoing LFS.