Contribution of the Ligamentum Teres to Hip Stability in the Presence of an Intact Capsule: A Cadaveric Study.

PURPOSE: To determine the contribution of the ligamentum teres (LT) to hip stability in the presence of an intact capsule with special attention to the change in range of motion and femoral head translation.

METHODS: Seven fresh-frozen cadaveric pelvises were used. Following visual inspection of the LT at different hip positions, internal rotation angles were measured at 10° of extension and at 0° of flexion, while external rotation was measured at 60°, 90°, and 110° of flexion with different hip abduction angles using electromagnetic motion tracking sensor. Femoral head translations were measured simultaneously. The tests were repeated after resection of the LT. The capsule was left intact for all test conditions. The results were compared between intact and LT resected conditions when torque of 2 and 4 Nm was applied.

RESULTS: Compared with the intact hip, the LT resected hip showed no significant difference when 2 Nm torque was applied in all scenarios. With 4 Nm torque application, significant increase in external rotation was found at 60° and at 90° of flexion (1.7° ± 0.8° and 2.1° ± 1.0°, respectively). Significant difference was also noted at 60°, 90°, and 110° of flexion when the hip was in the adducted position while at 90° in the abducted hip. However, LT resection did not show significant change in internal rotation. There was no significant difference in the translation distance of the femoral head in the intact hip compared with the LT resected hip (0.77-1.11 mm vs 0.79-1.29 mm).

CONCLUSIONS: Our results indicate that within the physiologic range of motion, LT can minimally limit external rotation when the hip is in the flexed position but does not contribute to translation stability.

CLINICAL RELEVANCE: In the hip with intact capsule, LT deficiency can result in a slight increase in range of motion, but its contribution to stability is questionable.