Femoral anteversion change is associated with ischiofemoral impingement after total hip arthroplasty: a retrospective CT evaluation.

OBJECTIVES: We evaluated the relationship between femoral anteversion (FA), FA change, and ischiofemoral impingement (IFI) and the relationship between FA, femoral offset (FO), and greater trochanteric pain syndrome (GTPS) after total hip arthroplasty (THA). MATERIALS AND METHODS: In this retrospective study, two readers assessed FA and FO on CT images of 197 patients following primary THA with an anterior surgical approach between 2014 and 2021. FA change was calculated relative to preoperative CT, while FO change was calculated relative to preoperative radiographs and classified as decreased (≥-5 mm), increased (≥ + 5 mm), or restored (± 5 mm). Clinical and imaging data were analyzed for IFI and GTPS after surgery. Group differences were evaluated using Student's t-test, chi-square analysis, and receiver operating characteristic (ROC) analysis. RESULTS: The change in FA was 3.6 ± 3.3° to a postoperative FA of 22.5 ± 6.8°, while FO increased by 1.7 ± 3.5 mm to a postoperative FO of 42.9 ± 7.1 mm. FA and FA change were higher in patients with IFI (p ≤ 0.006), while no significant difference was observed for patients with and without GTPS (p ≥ 0.122). IFI was more common in females (p = 0.023). In the ROC analysis, an AUC of 0.859 was observed for FA change to predict IFI, whereas the AUC value was 0.726 for FA alone. No significant difference was found for FO change in patients with and without IFI or GTPS (p ≥ 0.187). CONCLUSION: Postoperative FA, FA change, and female sex were associated with IFI after anterior-approached THA. The change in FA was a better predictor of IFI than absolute postoperative FA alone. CLINICAL RELEVANCE STATEMENT: The findings of this study suggest that preservation of the preoperative femoral anteversion may reduce postoperative ischiofemoral impingement in patients undergoing total hip arthroplasty. KEY POINTS: • Higher postoperative femoral anteversion and anteversion change were associated with ischiofemoral impingement. • Femoral anteversion change was a better predictor of impingement than absolute postoperative anteversion. • No significant association was found between femoral offset and postoperative hip pain.