Acetabular revision for iliopsoas impingement: a study of 55 cases at 3 years of follow-up. Does the procedure achieve the Minimal Clinically Important Difference (MCID) in the Oxford-12 score in more than 80% of cases?

Introduction: Several surgical options can be offered to manage iliopsoas impingement. Research published on cup replacements often concerns a small population size or multicentre studies, suggesting a variety of indications. We conducted a retrospective single centre study screening according to a specific protocol of a population of patients who had a cup replacement for iliopsoas impingement. The objectives were: 1) to specify the functional outcomes and the achievement of the Minimal Clinically Important Difference (MCID) and the Patient Acceptable Symptom State (PASS) according to the Oxford-12 score, and 2) to assess the complication rate.

Hypothesis: Our hypothesis was that acetabular replacements achieve a Minimal Clinically Important Difference (MCID) in more than 80% of cases.

Patients and methods: Fifty-five hips underwent acetabular revision between 2011 and 2020. Forty-three were performed as first-line surgery, eight after failed tenotomy and four after failed anterior hip capsule thickening plasty. A CT scan of all the hips revealed a median overhang of 9 mm (7; 12) and a 7 ° cup anteversion (2; 19). Follow-up included assessment of the Oxford-12 score using MCID and PASS, the Merle d'Aubigné score, an assessment of hip flexion muscle strength using the Medical Research Council scale, and an assessment of satisfaction and complications.

Results: At a mean follow-up of 3 years (2-10), the difference in the Oxford score before and at follow-up was 18 points (15; 27) (p < 0.001), the median Medical Research Council score was 4.5 (4; 5) and patients were satisfied or very satisfied in 73% of cases (40/55). The MCID was achieved for 87% of the hips (48/55), and the PASS was achieved in 67% of cases (33/55). The rate of complications involving surgical revision was 10.9% (6/55) with respectively: two anterior dislocations, one early infection on day 10 resolved after wound irrigation and appropriate antibiotic therapy, one intraoperative fracture of the trochanter requiring osteosynthesis and one arthroscopic revision to remove a free cement fragment.

Conclusion: Due to a good functional outcome but a high complication rate, a cup replacement can be offered for iliopsoas impingement associated with acetabular malposition or significant overhang.

Level of evidence: IV.