Iliopsoas tendonitis following total hip replacement in highly dysplastic hips: a retrospective study

BACKGROUND: As a recognized cause of groin pain following total hip arthroplasty, iliopsoas tendonitis probably results from different factors. Given the anatomic disadvantage, dysplastic hips theoretically make acetabular component relatively retroverted or oversized, screws implanted frequently, and iliopsoas tendonitis more likely. However, the prevalence and mechanism of iliopsoas tendonitis following total hip replacement in dysplastic hips are not fully understood. METHODS: One hundred and thirty-three total hip arthroplasties for Crowe type 2 to 4 dysplastic hips were compared with 126 total hip arthroplasties for hips without dysplasia in this study. Preoperative patient demographic data were well matched between the groups. Clinical and radiographic evaluations were performed. RESULTS: A significantly higher frequency of protruded screws (24.8% vs 0), anterior overhang of acetabular components (30.8% vs 4.0%), and increased leg lengthening (3.6 [2.0–6.8] vs 0.5 [0–1.8]) was found in the dysplastic group (all p values < 0.05). However, the femoral offset and inclination and anteversion of acetabular components between the groups did not differ significantly. No difference in the prevalence of iliopsoas tendonitis was found between the groups. A new cause of iliopsoas tendonitis following total hip arthroplasty was detected in the dysplastic group. The iliopsoas tendonitis was irritated by an instable artificial femoral head. CONCLUSIONS: The dysplastic hips did not present a higher incidence of postoperative iliopsoas tendonitis in this study. Iliopsoas tendonitis could be somewhat prevented by smaller size of acetabular components and soft tissue release in dysplastic hips, but irritated by an instable artificial femoral head.