Cross-sectional analysis of the iliopsoas tendon and its relationship to the acetabular labrum: an anatomic study.

BACKGROUND Hip pain in patients with normal bony anatomy and anterior labral injury may be related to compression of the iliopsoas tendon across the anterior capsulolabral complex. No attempts to characterize the 3-dimensional anatomy of the iliopsoas tendon and its relationship to the acetabular labrum have been reported to date. HYPOTHESIS The iliopsoas tendon directly overlies the capsulolabral complex. Contribution of the muscle belly and tendon to the overall circumference at the level of the labrum is approximately the same. STUDY DESIGN Descriptive laboratory study. MATERIALS AND METHODS Eight hip joints were dissected and cross-sectional measurements of the iliopsoas muscle-tendon complex were performed using digital calipers and image analysis software. RESULTS The iliopsoas tendon in all specimens was located directly anterior to the anterosuperior capsulolabral complex at the 2 to 3 o'clock position. The overall length of the iliopsoas tendon from the lesser trochanter to the acetabular labrum was 75.4 +/- 0.9 mm. The circumference of the iliopsoas tendon at the lesser trochanter was 25.5 +/- 2.6 mm, the iliopsoas tendon at the level of the labrum was 28.4 +/- 2.8 mm, and the iliopsoas tendon-muscle belly complex at the level of the labrum was 63.8 +/- 7.4 mm. At the level of the labrum, the iliopsoas is composed of 44.5% tendon and 55.5% muscle belly. CONCLUSION The close anatomic relationship of the iliopsoas tendon to the anterior capsulolabral complex suggests that iliopsoas pathologic changes at this level may lead to labral injury. Additionally, these data suggest that at the level of the labrum, 45% of the tendon-muscle belly complex should be released to release the entire tendinous portion. CLINICAL RELEVANCE Knowledge of the cross-sectional anatomy of the iliopsoas tendon and its relationship to the acetabular labrum will better assist surgeons in treating lesions associated with iliopsoas injury.