Spencer-Gardner, Luke

Abstract Purpose Iliopsoas tendinitis following total hip arthroplasty (THA) has been described to result from acetabular component overhang as well as prominent femoral collars. Yet, a portion of patients experience iliopsoas tendinitis in the setting of well-positioned components. The purpose of this study was to assess anatomic factors predisposing to iliopsoas tendinitis after THA. Methods Patients with THAs performed at three academic institutions who subsequently underwent arthroscopic iliopsoas release were retrospectively reviewed from 2015 to 2025 and propensity matched in a 1:3 fashion to a control group of THAs without subsequent iliopsoas release. Controls were matched by age, surgery date, laterality, sex, surgical approach, and implanted femoral component. Patients with iliopsoas tendinitis and subsequent release (THA-IP) were evaluated for anterior acetabular component overhang and femoral collar overhang, when a collar was present. We also evaluated the absolute and relative profile of the lesser trochanter on anteroposterior radiographs, understanding that when less of the lesser trochanter is visualized, the trochanter is anatomically displaced posterolaterally, resulting in a more arduous route from the inner pelvic origin of the iliopsoas to its insertion on the femur. Results Forty-five patients (mean age: 57±11; 71% female; 19 direct anterior, 10 anterolateral, 16 posterior approach) undergoing THA-IP were analyzed and matched to 135 controls. Both groups demonstrated a median cup size of 54 mm and head size of 36 mm. Average time to iliopsoas release after THA was 4 years. Anterior cup overhang of >2 mm was present in 49% of THA-IP patients, with 18% having collared femoral components, and 9% demonstrating collar overhang of >2 mm. Overall, 19 THA-IP patients had <2 mm of cup and collar overhang and 26 patients had >2 mm of overhang. THA-IP patients with <2 mm of cup and collar overhang had significantly greater relative posterolateralization of the lesser trochanter compared to those with overhang of >2 mm (p=0.010) and to controls (p=0.037). Conclusion Visualizing “Less of the Lesser” on anteroposterior hip radiographs and associated posterolateralization of the lesser trochanter may be an anatomic risk factor for iliopsoas tendinitis following THA, even in the presence of satisfactorily positioned components.