Abnormally High Dislocation Rates of Total Hip Arthroplasty After Spinal Deformity Surgery

Background The purpose of this study was to determine the prevalence of concurrent spinopelvic fusion and THA and identify the risk of THA dislocation in patients with concurrent spinopelvic fusion. Methods We retrospectively reviewed an institutional database of spinal deformity patients and the Humana Inc data set to identify patients with concurrent THA and spinopelvic fusion. The prevalence of concurrent THA and spinopelvic fusion was identified, as was the risk of dislocation for all cohorts. Results Of 328 patients with spinopelvic fusions at our institution, 15 patients (4.6%) were found to have concurrent THA. Similarly, within the Humana database among 1049 patients with spinopelvic fusion, 4.6% had a concurrent THA. Among the 58,692 THA patients identified, only 0.1% had a concurrent spinopelvic fusion. A THA dislocation was observed in 3 of 15 patients (20.0%) and 3 of 18 THA (16.7%) within our institutional review. Within the Humana database, 8.3% of patients with THA and spinopelvic fusion went on to have a dislocation of their THA compared to 2.9% of patients with THA and no history of spinopelvic fusion (relative risk: 2.9 [1.2-7.6]). Conclusion Among patients with spinopelvic fusion, the prevalence of concurrent THA is 4.6%, and among primary THA patients, the prevalence of concurrent spinopelvic fusion is 0.1%. An alarmingly high THA dislocation rate has been demonstrated among THA patients with concurrent spinopelvic fusion at our institution (20%) and within a large national database (8.3%).