Dynamic femoral head translations in dysplastic hips

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BackgroundDevelopmental dysplasia of the hip is an important disease leading to osteoarthritis. Recently, researchers have focused on hip instability as a potentially important dynamic factor for osteoarthritis, but the detailed kinematics of dysplastic hips during weight-bearing gait have not been reported. The purpose of this research is to contrast femoral translation in contralateral healthy hips and dysplastic hips during weight-bearing stepping.MethodsTwelve dysplastic hips and eight healthy hips were investigated. Hip joint kinematics were analyzed using 3D-2D model-image registration with dynamic fluoroscopic images of each hip during a stepping-in-place activity. Femoral translation relative to the acetabular center was quantified as instability.FindingsTotal femoral head translations were significantly different between dysplastic and contralateral healthy hips. Mean translation was 1.0 mm in dysplastic hips and 0.4 mm in contralateral healthy hips during swing-phase, and consisted of inferior translation during early swing phase with a complementary superior translation just before foot strike. Total femoral translation was significantly correlated to several radiographic indices of hip dysplasia.InterpretationSuperior translations of the femur during the end of swing phase may result in altered articular contact mechanics, abnormal stresses on the labrum and lost lubricant sealing. All of these factors may contribute to joint degeneration and osteoarthritis in dysplastic hips.HighlightsFemoral head displacement in capsule was measured by 2D-3D registration method.Distal translation was more remarkable in dysplastic hip patient.Osteoarthritis may advance due to dynamic instability as well as poor bony formation.

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