Capsular ligaments provide a passive stabilizing force to protect the hip against edge loading

Abstract

Aims In the native hip, the hip capsular ligaments tighten at the limits of range of hip motion and may provide a passive stabilizing force to protect the hip against edge loading. In this study we quantified the stabilizing force vectors generated by capsular ligaments at extreme range of motion (ROM), and examined their ability to prevent edge loading. Methods Torque-rotation curves were obtained from nine cadaveric hips to define the rotational restraint contributions of the capsular ligaments in 36 positions. A ligament model was developed to determine the line-of-action and effective moment arms of the medial/lateral iliofemoral, ischiofemoral, and pubofemoral ligaments in all positions. The functioning ligament forces and stiffness were determined at 5 Nm rotational restraint. In each position, the contribution of engaged capsular ligaments to the joint reaction force was used to evaluate the net force vector generated by the capsule. Results The medial and lateral arms of the iliofemoral ligament generated the highest inbound force vector in positions combining extension and adduction providing anterior stability. The ischiofemoral ligament generated the highest inbound force in flexion with adduction and internal rotation (FADIR), reducing the risk of posterior dislocation. In this position the hip joint reaction force moved 0.8° inbound per Nm of internal capsular restraint, preventing edge loading. Conclusion The capsular ligaments contribute to keep the joint force vector inbound from the edge of the acetabulum at extreme ROM. Preservation and appropriate tensioning of these structures following any type of hip surgery may be crucial to minimizing complications related to joint instability. Cite this article: Bone Joint Res 2021;10(9):594–601.

Femoral impingement in maximal hip flexion is anterior-inferior distal to the cam deformity in femoroacetabular impingement patients with femoral retroversion

“…This study also has limitations: first, although the software used for impingement simulation is based on bone segmentation and calculates the osseous ROM, it was impossible to take into account soft-tissue such as acetabular labrum, 47 muscles, cartilage, ligaments, 53 or the pulvinar in the acetabular fossa. 54 This prevents direct comparison to motion capture studies.…”

Hip joint contact pressure and force: a scoping review of in vivo and cadaver studies

“…There are several limitations in these cadaveric studies: the soft-tissues and capsule excision, which influences joint biomechanics, 44 are necessary to adapt the flat sensor to the hip joint geometry. Furthermore, the intra-articular presence of the sensor may interfere with the joint biomechanics and dynamics, leading to inaccuracies in the data recorded.…”

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Instantaneous Generation of Subject-Specific Finite Element Models of the Hip Capsule

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