STATICALLY EQUIVALENT LOAD AND SUPPORT CONDITIONS PRODUCE DIFFERENT HIP-JOINT CONTACT PRESSURES AND PERIACETABULAR STRAINS

The hip is a common site of orthopaedic trauma and disease, and consid erable research has been directed toward understanding the development of contact pressures within the joint. Virtually all experimental stu dies to date have employed proximal Femurs compressed along the joint reaction force vector into acetabulae explanted from cadaver pelves. T his approach presumes that deformations of the acetabulum are highly l ocalized, and that the pelvis is functionally a rigid body. We have de veloped a methodology that uses intact pelves loaded through simulatio n of the abductor mechanism. A direct comparison of the two techniques revealed significantly different joint contact characteristics and pe riacetabular strains. Fuji film measurements of contact area and press ure were more widely distributed across the acetabulum for the intact pelvis, with significant pressure development in anterior and posterio r regions. Contact patterns in the explanted acetabulae were concentra ted in the superior portion of the joint. Principal strains from three rosette gages placed near the acetabular rim were also significantly different for the two testing techniques, but were not substantially a ltered by the presence of Fuji film within the joint. The results indi cate that deformation of the entire pelvis and the manner in which loa ds are applied significantly affect development of contact pressures w ithin the hip joint, and that Fuji film is a suitable technique for re cording those patterns. Copyright (C) 1996 Elsevier Science Ltd.