The capsular ligaments provide greater rotational stability than the acetabular labrum and the ligamentum teres

In a recently published study in The Bone And Joint Journal, researchers examined in cadaveric hips which soft-tissue structures are most responsible for the rotational stability of the joint. A total of nine cadaveric hips were placed in a special apparatus which allowed torque and rotational forces to be applied in all six degrees of freedom. The hip was rotated through a full range of movement and the contribution of the iliofemoral, pubofemoral and ischiofemoral ligaments, as well as of the ligamentum teres, to rotational stability was assessed by removing one ligament at a time and measuring the reduction in the torque required to reach the same angular position compared with the state before sectioning. The contribution of the labrum of the acetabulum was also measured. Each of the capsular ligaments acted as a primary rotational stabiliser of the hip, and the ligamentum teres acted as a secondary stabiliser in deep flexion, abduction and external rotation. The lever arm of the iliofemoral ligament and the ischiofemoral ligament were the principal stabilisers in 2/3 of the positions examined. The researchers concluded that recognising the importance of these structures in preventing excessive rotation of the hip and the impending femoroacetabular impingement-instability may bear on the practice of surgeons during hip joint-preserving procedures (arthroscopy or osteotomies) and hip arthroplasty.