Etiology and severity of impingement injuries of the acetabular labrum: what is the role of femoral morphology?

Injuries to the acetabular labrum have been seen in association with femoroacetabular impingement, but recent studies have reported labral pathology in patients with normal hip morphology. The hypothesis of the current study was that labral lesions could occur without femoroacetabular impingement but that labral pathology would occur more commonly and more severely in hip joints that exhibit reduced head-neck offset. The presence, location, and severity of labral injury were recorded in 22 cadaveric specimens. Computed tomography was used to define the anatomic parameters of proximal femoral morphology. Three-dimensional modeling was used to simulate hip positions that typically cause labral impingement, including high flexion and internal rotation. Femoral morphology was compared between specimens with and without labral pathology using descriptive statistics. Labral pathology was seen in 15 of 22 specimens and was located in the anterosuperior portion of the labrum. No difference existed in age, femoral neck shaft angle, anteversion, acetabular depth, head diameter, alpha angle, or beta angle between specimens with and without labral pathology. The severity of labral pathology correlated with the alpha angle of the proximal femur. This study demonstrates that damage to the labrum may occur in hips with normal proximal femur morphology. However, the findings also indicate that the presence of morphologic features that increase the risk of impingement may predispose the hip joint to a characteristic pattern or severity of labral pathology. The results confirm the importance of considering both femoral morphology and athletic-type activities of the hip when determining the mechanism responsible for injury of the acetabular labrum.