What happens in the medium-term to capsule-thickening plasties for iliopsoas impingement after total hip arthroplasty? Evaluation of 14 procedures at 4 years’ follow-up

Introduction: In 2015, we described a capsule-thickening technique via an anterior approach for iliopsoas cup impingement. To our knowledge, medium-term results have not been reported. We therefore retrospectively analyzed all cases in the initial series and those since 2015, to assess this original technique over a longer follow-up: 1) to analyze complications, and 2) to assess functional outcome. Hypothesis: The study hypothesis was that this surgical solution has a success rate sufficient for it to be included in the therapeutic armamentarium for iliopsoas impingement. Material and method: Fourteen patients were included. Nine plasties were in first line, 3 after tenotomy, and 2 after cup exchange. The anterior Hueter approach was used, visualizing anterior cup overhang, sometimes associated with penetration of the anterior capsule, and enabling capsule thickening by a folded VicrylTM mesh. Functional results were analyzed. Results: At a median 4 years’ follow-up (IQR, 2-5; range, 1-9), change over baseline in Oxford score was 7 points (p=0.004), median Medical Research Council thigh flexion strength score was 5 (IQR, 5-5), and 50% of patients (7/14) were satisfied or very satisfied. The major complications rate was 7% (1/14), for 1 irrigation of infected hematoma, cured without recurrence; there was also 1 minor case of injury to the lateral cutaneous nerve of the thigh. 43% of patients (6/14) exhibited a minimal clinically important difference (MCID) and 64% (9/14) a patient-acceptable symptom state (PASS). Median anatomic overhang on anatomic CT transverse slice was 7 mm (IQR, 3-8; range, 0-13). Four patients underwent secondary acetabular component exchange; their median overhang was 7.5 mm (IQR, 7-8) compared to 5 mm (IQR, 2-8) for the other patients (p-value non-calculable). Conclusion: This surgical option seems interesting when acetabular overhang is not too great, especially as it does not affect flexion strength. Level of evidence: IV