Several previous pathoanatomical and biomechanical studies focused primarily on the cam morphology as the primary contributor to symptoms of femoroacetabular impingement (FAI) and limited range of motion. However, there is a growing population of individuals with asymptomatic cam morphologies who show no clinical signs; thus, the cam deformity, alone, may not fully delineate an individual's symptomatology or limited motion. These studies expanded beyond the cam morphology, to determine how additional anatomical characteristics could contribute to symptoms and influence functional mobility, using: 1) in vivo analyses, where we asked how specific anatomical parameters (in addition to the cam morphology) can predict individuals at risk of symptoms; 2) In silico simulations, where we examined how pathoanatomical features contributed to adverse loading conditions, resulting in higher risks of hip joint degeneration; 3) In vitro cadaveric experiments, where we examined the contributions of the cam morphology and encapsulating ligaments to joint mechanics and microinstability. This research further highlights that more emphasis should be placed on proper patient selection. There are implications of how structural anatomy can affect musculature, joint loading and stability, which should all be closely examined to improve the effectiveness of hip preservation surgery as well as the understanding of non-surgical management

We dissected 20 cadaver hips in order to investigate the anatomy and excursion of the trochanteric muscles in relation to the posterior approach for total hip replacement. String models of each muscle were created and their excursion measured while the femur was moved between its anatomical position and the dislocated position. The position of the hip was determined by computer navigation.

In contrast to previous studies which showed a separate insertion of piriformis and obturator internus, our findings indicated that piriformis inserted onto the superior and anterior margins of the greater trochanter through a conjoint tendon with obturator internus, and had connections to gluteus medius posteriorly. Division of these connections allowed lateral mobilisation of gluteus medius with minimal retraction. Analysis of the excursion of these muscles revealed that positioning the thigh for preparation of the femur through this approach elongated piriformis to a maximum of 182%, obturator internus to 185% and obturator externus to 220% of their resting lengths, which are above the thresholds for rupture of these muscles.

Our findings suggested that gluteus medius may be protected from overstretching by release of its connection with the conjoint tendon. In addition, failure to detach piriformis or the obturators during a posterior approach for total hip replacement could potentially produce damage to these muscles because of over-stretching, obturator externus being the most vulnerable.