Histopathologic Features of the Acetabular Labrum in Femoroacetabular Impingement

This paper summarizes clinical and histopathologic findings derived from 25 patients who had surgery for symptomatic femoroacetabular impingement. We explored if observed pathologic features were consistent with hypothesized mechanisms of injury, if severity of osteoarthritis and labral degeneration were associated, and if labral refixation would present an alternative. Clinically, all patients presented with limited range of motion at the hip attributable to pain and a positive impingement test. Magnetic resonance arthrography and surgical observations showed degenerated or ruptured labra or both in the anterior and/or superior regions of the acetabular rim (24 of 25 specimens) which correlated with pain provocation, limited range of motion, and anatomic deformities. Histologically, labra were mostly hyperplastic with disorganized cystic matrices. No inflammation was observed. Spatial distribution of degenerated labral matrices was not different for the two femoroacetabular impingement mechanisms. Labral degeneration and severity of osteoarthritis observed on radiographs did not correlate. In patients having only joint debridement, the labral matrix at the tip, near its vascular supply, was normal. Femoroacetabular impingement is a gentle chronic irritation of the labra located at the site of rupture that elicits a degenerative reaction. In early stages of the disease, the labral tip is not involved, providing the possibility of labral refixation after resection of the degenerated portion.