Regrowth of the psoas tendon after arthroscopic tenotomy: a magnetic resonance imaging study.

PURPOSE The purpose of this study was to evaluate whether the psoas tendon regenerates after arthroscopic tenotomy through the central compartment of the hip in patients with internal snapping hip. METHODS Twenty-seven patients with a snapping hip, aged 18 to 54 years (mean, 37.47 years), underwent arthroscopic tenotomy through the central compartment of the hip; all patients had symptomatic femoroacetabular impingement as well. The degree of regeneration was evaluated by preoperative and postoperative measurements of the tendon perimeter with a magnetic resonance imaging protocol in patients with more than 6 months' follow-up. In addition, function was assessed preoperatively and postoperatively with the Western Ontario and McMaster Universities Osteoarthritis Index score. Postoperative active flexion force was graded clinically between 1 and 5 with the Medical Research Council score. RESULTS Eight patients had less than 6 months' follow-up, and they were excluded. The remaining 19 patients were evaluated after a mean follow-up period of 23.16 months (SD, 12.95 months). Tendon regeneration occurred in all patients. Compared with preoperative measurement, the psoas tendon circumference had recovered by 84.3% on average (55.44 ± 5.68 mm v 46.71 ± 6.05 mm, P < .001). Pain improved in all patients, and the mean Western Ontario and McMaster Universities Osteoarthritis Index score fell from 49 ± 15.9 points to 10.74 ± 11.35 points (P < .001). Muscle force recovered completely in all cases. CONCLUSIONS There is a process of tissular repair after psoas tenotomy, and the findings on magnetic resonance imaging suggest that tendon tissue regrowth occurs. LEVEL OF EVIDENCE Level IV, therapeutic case series.