Master of Science
The hip capsule, labrum, and bone contribute to hip stability. Abnormalities in these structures are associated with pain and microinstability. Previous studies have quantified the individual stabilizing roles of the capsule and labrum and have associated cam over-resection with decreased hip stability.
The first objective of this thesis was to identify the relative biomechanical contributions of the capsule, labrum, and bone to the hip suction seal, as a representation of hip stability. The second objective was to assess the effectiveness of a labral reconstruction in restoring the suction seal after a cam over-resection.
Ten human cadaveric hips were tested in a combination of different capsule, labrum, and bony conditions. The initial resistive strength of native tissues cannot be recovered after a capsulotomy and labral tear are made, despite a complete repair of all structures. A labral reconstruction after cam over-resection partially restores the suction seal, but not to normal levels.
Summary for Lay Audience
The hip joint is made up of bony and soft tissue structures. The capsule is an outer covering that surrounds the femoral head and socket creating a watertight seal between the joint and overlying muscle. The labrum is a circumferential cartilage layer attached to the rim of the acetabulum that deepens the acetabular socket.
The most common anatomic abnormality of the hip is femoroacetabular impingement (FAI). FAI refers to an abnormal bump of bone at the edge of the femoral head and/or an abnormal bump of bone at the socket rim. When the hip is placed in certain positions, these bumps hit each other and cause pain, labral tears and early wear of the cartilage leading to arthritis. To treat this, the abnormal bumps of bone are surgically removed, and labral tears are repaired.
Previous research has shown that the capsule, labrum, and bone all stabilize the hip and that if too much bone is taken away during surgery, the hip becomes destabilized. However, no research has measured how much each structure contributes to hip stability, or the best way to treat a hip where too much bone has been removed. Therefore, our first goal was to measure how much each structure contributes to hip stability. Our second goal was to see if placing a tendon graft where the labrum used to be helps restore the suction seal when too much bone had been taken away previously. To do this, we completed two studies that tested the force required to break the suction seal in a series of different capsule, labrum, and bony situations. We used hips from people that donated their bodies to research, which were tested by pulling the femoral head away from the socket and measuring the force it took to break the seal in each situation. Overall, we found that as soon as the normal capsule, labrum, and bone was altered, the suction seal would never be as strong. We also found that while a tendon graft improves the suction seal after too much bone has been removed, it does not restore it to a normal level.
Hoffer, Alexander J., "The Shared Contributions of the Capsule, Labrum, and Bone on the Suction Seal of the Hip" (2023). Electronic Thesis and Dissertation Repository. 9536.
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