Anatomy, histologic features, and vascularity of the adult acetabular labrum

Acetabular labrum tears have been implicated as a cause of hip pain in adul t patients. Few studies describe the anatomy, histologic features, and micr ovasculature of the acetabular labrum and labral tears. Fifty-five embalmed and 12 fresh-frozen adult hips with a mean age of 78 years (range, 61-98 y ears) were studied. Of these, 96% (53 of 55) of the hips had labral tears, with 74% of the tears located in the anterosuperior quadrant. Histologicall y, the fibrocartilaginous labrum was contiguous with the acetabular articul ar cartilage through a 1- to 2-mm zone of transition. A consistent projecti on of bone extends from the bony acetabulum into the substance of the labru m that is attached via a zone of calcified cartilage with a well-defined ti demark. Two distinct types of tears of the labrum were identified histologi cally. The first consisted of a detachment of the fibrocartilaginous labrum from the articular hyaline cartilage at the transition zone. The second co nsisted of one or more cleavage planes of variable depth within the substan ce of the labrum. Both types of labral tears were associated with increased microvessel formation seen within the tear. The acetabular labrum tear app ears to be an acquired condition that is highly prevalent in aging adult hi ps. Labral tears occur early in the arthritic process of the hip and may be one of the causes of degenerative hip disease.