Is Sacro-iliac Joint Degeneration Associated With Inferior Outcome Post-Total Hip Arthroplasty?

Abstract

Osteoarthritis (OA) of the hip is known to be associated with OA in adjacent areas such as the sacro-iliac joint (SIJ). This study aimed to: 1) describe the prevalence of SIJ OA in a cohort of patients undergoing total hip arthroplasty (THA), 2) test for an association between the degree of hip OA and SIJ OA, and 3) examine if the degree of SIJ OA is associated with outcomes post-THA. This is a retrospective analysis of prospective databases from two tertiary academic centers. There were 1,154 THA cases from 2018 to 2022. The mean age and body mass index were 67 years and 28.7, respectively. Preoperative radiographs were assessed for hip OA via the Tönnis grade, with 0 being the lowest severity and 3 being the highest. The SIJ OA was graded using the Modified New York criteria (mNYC), ranging from 0: normal to 4: ankylosis. All patients had pre and postoperative Oxford Hip Score (OHS) measurements, with follow up at 1 year. A subset of 589 patients also had 5-level EuroQol 5-Dimension pre- and postoperative as a lifestyle measure. Complications, reoperations, and revisions were recorded. Data were analyzed using Statistical Analysis System version 9.4 (SAS Institute Inc., Cary, North Carolina, USA). There was a high prevalence of advanced SIJ OA, with 39.3% (453) mNYC three cases and 1.4% (16) mNYC four cases. The association between Tönnis grade and mNYC was weak but significant (ρ = 0.19, P = 0.047). There was no difference in OHS at 1 year when accounting for age, hip OA, or baseline OHS (P < 0.216). There is a high prevalence of SIJ pathology in patients undergoing THA, but a weak association between SIJ and hip OA. The SIJ pathology and outcomes following THA had no association, indicating that for patients presenting with concurrent hip and SIJ OA, the SIJ should not direct treatment.