The contribution of the ligamentum teres to the hip fluid seal: A biomechanics study.

Background: The suction seal of the hip plays an important role in maintaining hip stability; however, the function of the ligamentum teres in maintaining this seal remains poorly understood. This study aimed to evaluate the effectiveness of the hip suction seal in ligamentum teres deficient hips for joint positions occurring during gait.

Methods: Six fresh-frozen human cadaveric hips were dissected and mounted to an Instron materials test system. Each specimen was analyzed for average peak distraction force, stiffness, and total energy during hip displacement. Testing was performed in the native intact ligamentum teres state and the deficient ligamentum teres state. Specimens were examined in 20° of flexion, neutral, and 10° of extension.

Findings: In the neutral position, the ligamentum teres deficient state displayed a significant decrease in peak distraction force (mean difference: 33.2 N, p < 0.001), average stiffness (mean difference: 63.7 N/mm, p = 0.016), and total energy (mean difference: 82.3 mJ, p = 0.022) compared to the intact controls. In extension, the deficient state exhibited a significant decrease in peak distraction force (mean difference: 42.8 N, p < 0.001) and total energy (mean difference: 72.9 mJ, p = 0.007). In flexion, the deficient state displayed a significant decrease in peak distraction force relative to contols (mean difference: 7.1 N, p = 0.003).

Interpretation: The ligamentum teres plays a significant role in maintaining the suction seal of the hip, with its effect being most prominent when the hip is in neural alignment or in extension. The findings suggest that ligamentum teres deficiency may be a relevant treatment target in the clinical setting.