The capsular ligaments provide more hip rotational restraint than the acetabular labrum and the ligamentum teres

Abstract

In this in vitro study of the hip joint we examined which soft tissues act as primary and secondary passive rotational restraints when the hip joint is functionally loaded. A total of nine cadaveric left hips were mounted in a testing rig that allowed the application of forces, torques and rotations in all six degrees of freedom. The hip was rotated throughout a complete range of movement (ROM) and the contributions of the iliofemoral (medial and lateral arms), pubofemoral and ischiofemoral ligaments and the ligamentum teres to rotational restraint was determined by resecting a ligament and measuring the reduced torque required to achieve the same angular position as before resection. The contribution from the acetabular labrum was also measured. Each of the capsular ligaments acted as the primary hip rotation restraint somewhere within the complete ROM, and the ligamentum teres acted as a secondary restraint in high flexion, adduction and external rotation. The iliofemoral lateral arm and the ischiofemoral ligaments were primary restraints in two-thirds of the positions tested. Appreciation of the importance of these structures in preventing excessive hip rotation and subsequent impingement/instability may be relevant for surgeons undertaking both hip joint preserving surgery and hip arthroplasty.Cite this article: Bone Joint J 2015; 97-B:484–91.

Increased Hip Stresses Resulting From a Cam Deformity and Decreased Femoral Neck-Shaft Angle During Level Walking

“…Taut hip ligaments would properly seat the femoral head into the acetabulum at more neutral positions, but may restrain hip ROM in individuals with cam morphology. However, knowing that capsular ligaments also play a vital role in minimizing edge loading [59,60], poorly functioning ligaments may be unable to prevent adverse contact loading at higher amplitudes of motion. Therefore, it would be imperative to further examine the effects of the surrounding capsule on limiting adverse stresses and microinstability [20,32].…”

Basic biomechanics of the hip

“…Researchers have used cadaveric hips to measure the contribution of each ligament using range of motion (ROM) testing, by measuring the reduction in measured torque when the ligaments had been removed 3 . In this manner the IF and ISF ligaments were found to have an essential role in restraining rotational hip movement.…”

Capsular Ligament Function After Total Hip Arthroplasty

“…2) using an established protocol 24 . This rig adopted the International Society of Biomechanics coordinate system 25 and allowed either for flexionextension or abduction-adduction torques to be applied through pulleys with hanging weight couples, or for these axes to be fixed at specific angular positions with screw clamps 19,22 . Internal-external rotations were applied using the rotating axes of a dual-axis servohydraulic materials testing machine (model 8874; Instron) equipped with a 2-degrees-of-freedom (tension-torque) load-cell, thus allowing the passive restraint to hip rotation from the capsular ligaments to be measured 19,22 .…”

“…There is no tension to resist extreme range of motion and no sling protecting against subluxation. 18,2018 Translations were free to occur in response to applied load and/or movement 19,22 . For each specimen, the hip joint center was registered to the rig by moving the hip throughout its range of motion and iteratively repositioning it until the error between the functional hip center and the rig center was <1 mm.…”

“…Capsule preservation and repair can help to lower dislocation rates 6,7,10,[13][14][15][16][17][18] , and may also maintain the defenses of the native hip against hypermobility, impingement, subluxation, and edge-loading [19][20][21][22] . Preserving a capsular ligament increases surgical complexity: it requires more precise incision, and it limits exposure.…”