Assessment of function and muscle strength after endoscopic iliopsoas tenotomy to treat iliopsoas impingement after total hip arthroplasty

Purpose The objective of this study was to evaluate the functional outcome during follow-up (FU) after endoscopic tenotomy for iliopsoas (IP)-cup impingement and to quantitatively analyze the hip flexion strength. Methods This was a monocentric, retrospective cohort study of a single surgeon series. Functional assessment was based on the modified Harris score, the Oxford score and the visual analog scale score. Strength was measured with a handheld dynamometer in the sitting and lying position. Results Thirty-six IP tenotomies for cup impingement were performed between May 2013 and November 2021. Seven (19%) patients were lost to FU. At the time of tenotomy, the mean (standard deviation) age was 62,6 (12,2) and BMI was 26,5 (4,1). The mean FU time after tenotomy to the last FU was 3,6 (0,8) years. All three outcome scores improved from preoperatively to six months postoperatively (p < 0.001). There were no significant change from six months to last FU. The minimal clinically important difference (MCID) of the modified Harris score was set at 25. 20 (69%) patients had values that exceeded the threshold at one month and six months and neutral 19 (65.5%) had values that exceeded the threshold at the last FU. The limp symmetry index concerning hip flexion strength was 63% at 90 degrees and 40% at 30 degrees at the last FU. Conclusion Most patients significantly improved their outcome scores after endoscopic iliopsoas tenotomy, with results remaining consistently stable over time. Despite a significant loss in hip flexion strength, the majority of patients did not report any impairment of their quality of life.