Effect of capsular sparing versus capsular resection on pressure changes under the tendon of the iliopsoas muscle: An experimental cadaveric study.

Abstract

Although several risk factors for iliopsoas impingement after total hip arthroplasty have been determined, limited data are available whether resection or preservation of the joint capsule affects the pressure underneath the iliopsoas tendon. Therefore, this study aims to test our hypothesis that capsular resection increases the pressure forced by the iliopsoas tendon at the iliopsoas notch. Ten cadaveric hips were used for measuring the pressure changes under the iliopsoas tendon. First, measurements were taken in a neutral position of the hip with an increasing load applied onto the iliopsoas muscle (0-70 N). Second experiment was conducted at 10° of extension, 0°, and 30° of flexion, both with and without muscle load of 20 N. In both experiments, the pressure was tested in a capsule preserving setting, and then the same measurements were obtained after capsulectomy. Capsular resection increased mean subtendinous pressure in the neutral hip position (P < 0.0001). Significant differences were recorded with muscle load greater than 10 N (all P < 0.02). At 10° of hip extension, the subtendinous pressure in hips with intact capsules differed significantly from those after capsulectomy, both with and without applied load (both P < 0.0001). At 30° of hip flexion, significant difference was observed only between loaded and unloaded hips with capsulectomy (P = 0.0176). This study suggests that capsular resection during total hip arthroplasty alters the physiological pressures at the iliopsoas notch. Based on these findings, capsular sparing could decrease the risk of iliopsoas impingement after total hip arthroplasty.