The Sacroiliac Joint Fusion Patient Population and Its Prevalence of Total Hip Arthroplasty

Introduction: The prevalence of sacroiliac joint (SIJ) pathology generating lower back pain is increasing, often requiring SI joint fusion in refractory cases. Similarly, total hip arthroplasty (THA) is an increasing procedure in the older growing population. Prior SIJ fusion in patients undergoing THA has increased hip dislocation. This study aims to determine the prevalence of preexisting THA in SIJ fusion patients at our institution. Methods: After institutional review board approval, we completed a retrospective review of consecutive SIJ fusion cases performed by fellowship-trained orthopaedic spine surgeons between October 2019 and June 2022. The senior surgeon reviewed pelvis radiographs to determine whether a THA was present. Patient demographics, surgical history, SIJ fusion date, and laterality information from study participants' medical records were collected and analyzed. Results: We screened 157 consecutive cases and excluded 45 not meeting the inclusion criteria. One hundred twelve radiographs were reviewed, with seven additional patients excluded. The final analysis consisted of 105 patients (33M:72F). The mean age was 50.4 ± 13.8 years, and the mean body mass index was 29.1 ± 6.1 kg/m 2 . SIJ fusion laterality included 51 right (48.6%), 44 left (41.9%), and 10 bilateral (9.5%). One patient (0.95%) had a preexisting right THA, and two patients (1.9%) underwent ipsilateral THA after SIJ fusion. Conclusions: This study demonstrated a low prevalence (0.95%) of preexisting THA in SIJ fusion patients at our institution, similar to the THA prevalence of the total US population. Additional research is needed to determine the outcomes of patients with preexisting THA undergoing SIJ fusion.