A 3-dimensional MRI analysis of the <i>in vivo</i> femoral head centre translation in multiple static hip joint positions in subjects with femoroacetabular impingement

Background: Recent research questions the view of the hip joint as a ball-and-socket joint, yet many studies still use this model to quantify hip joint kinematics. This paper challenges that assumption and proposes a coupling mechanism between hip rotation and femoral head translation. Methods: 5 elite badminton players, all affected by femoroacetabular impingement, underwent MRI of the hip joint in 7 predefined positions per side. A model registration approach was used to quantify the hip joint rotation and femoral head translation of the femoral head in each condition. Results: 1 significant coupling mechanism was detected, hip flexion leads to an anterior translation of the femoral head centre of 0.024 mm per degree flexion (induvial R 2 : 0.72–0.91, conditional R 2 : 0.58, p &lt; 0.05). No significant couplings of other hip joint rotations and femoral head centre translation were detected. Conclusions: The findings emphasise the importance of incorporating femoral head centre translation, based on hip flexion angles, into biomechanical models and surgical simulations for femoroacetabular impingement patients to enhance the accuracy of simulation results.