Are femoroacetabular impingement tomographic angles associated with the histological assessment of labral tears? A cadaveric study.

PURPOSE: This study sought to investigate the association between tomographic femoroacetabular impingement (FAI) angles and histologically evaluated labral tears. The authors hypothesized that cadavers presenting with cam and pincer morphologies would present a higher prevalence of acetabular labral tears.

METHODS: Twenty fresh cadavers were submitted to computed tomography. Standard FAI angles were measured, including the alpha angle, femoral version, acetabular version, Tonnis angle and center-edge angle. A cam lesion was defined as an alpha angle greater than 50o. A pincer lesion was defined as a center-edge angle greater than 40o, a Tonnis angle less than 0o or acetabular version less than 0o. After dissection, three fragments of each acetabulum, corresponding to the antero-superior, superior and postero-superior acetabular rim, were obtained. These fragments were submitted to routine histological preparation. Each slide was evaluated for possible labral tears. Tears were classified according to their Seldes type.

RESULTS: The mean age of the cadavers was 50.2 years (SD: 7.4; 13 males). Sixteen (80%) of the cadavers had a cam lesion, and eight cadavers (40%) had a pincer lesion. Histologically, 16 (80%) of the cadavers had a labral tear in at least one region. According to the Seldes classification, 60.7% and 28.6% of these labral tears were type 1 and type 2, respectively. A mixed type of labral tear (10.7%), which represented a new form of Seldes tear, was described. Cadavers with a labral tear had significantly higher alpha angles than other cadavers (53.29o vs 49.33o, p = 0.01). Pincer lesions were not associated with labral tears. We found no association between pincer or cam lesions and Seldes classification.

CONCLUSION: Cadavers presenting with higher alpha angles had a higher incidence of labral tears. No association was found between FAI and Seldes classification.

CLINICAL RELEVANCE: This study demonstrated a high prevalence of FAI abnormalities associated with histological alterations in a cadaveric sample. Joint damage may be present in the early stages of FAI.