Purpose: The purpose of this prospective work was to determine: 1) the frequency of iliopsoas conflicts with prosthetic acetabular material in patients with a painful total hip arthroplasty, and 2) to determine the diagnostic features of this conflict and the results of an adapted therapeutic approach.

Material and methods: This prospective study was conducted between 1988 and 2000 in 206 painful total hip arthroplasties. Nine patients (4.%), mean age 50 years (38–65) had a highly suggestive clinical presentation (eight press-fit cups without cement, one metal-backed cemented cup). Mean delay to onset after implantation of the total hip arthroplasty was 7.3 months (1–48). The predominant clinical sign was groin pain triggered by active flexion of the hip with pain from 3° to 70°. For these nine patients, there was no sign of loosening and puncture had ruled out infection. The diagnosis was confirmed by sedation of the pain after extra-articular infiltration in contact with the anterior acetabular rim (rim overhang in six out of nine cases) under computed tomographic guidance.

Results: Therapeutic infiltration (xylocaine-slow release corticosteroids) under computed tomographic guidance provided complete sedation in four out of nine cases and partial sedation in one. Four patients experienced recurrence leading to terminal tenotomy of the iliopsoas which provided complete sedation in three and partial sedation in one. In all, seven of the nine patients achieved complete pain relief (four after infiltration including one recurrent case, and three after tenotomy). Physical examination at last follow-up did not disclose any loss of flexion amplitude of the thigh.

Discussion and conclusion: The delay to symptom onset was variable, but a symptom-free interval was always observed after implantation of the total hip arthroplasty. An anatomic factor (anterior cup rim) was not indispensable for diagnosis as it was confirmed in one of three cases with a positive infiltration test without rim overhang. The infiltration test was essential to confirm diagnosis and constituted the first therapeutic attempt which allowed complete cure in four of the nine patients. Tenotomy, indicated in case of recurrence, achieved complete cure in three of the four cases. The cup does not have to be changed necessarily to treat iliopsoas conflicts since infiltration or simple tenotomy provided complete cure in seven out of nine cases.