Takafumi Kumano

Regional difference of tensile properties of the human acetabular labrum in various hip disorders

Background Most acetabular labral tears have been shown to occur in the anterosuperior quadrant of the acetabulum. This region may represent a weak area that predisposes the labrum to detachments later in age. Labral detachments may be potentiated by acetabular dysplasia as well. We examined tensile properties and histological appearance of human acetabular labra for regional differences. Methods Human acetabular labra were harvested from 45 patients who underwent total hip arthroplasty for the treatment of secondary osteoarthritis caused by developmental dysplasia of the hip (DDH), primary osteoarthritis or idiopathic necrosis of the femoral head. Thereafter, the tensile properties of the human acetabular labra were investigated using a uniaxial tension testing apparatus. In addition, the pathological findings of the harvested labra were observed. Results For all specimens, the mean tensile stresses at failure of the anterosuperior and posteroinferior labra were 4.0 ± 1.6 MPa and 4.6 ± 1.8 MPa, the mean strains were 31.9 ± 28.3% and 22.3 ± 5.4%, and the mean tensile moduli were 38.3 ± 16.9 MPa and 47.3 ± 22.2 MPa, respectively. No significant difference was found between the tensile properties of the anterosuperior and posteroinferior labra. Moreover, no significant differences were found among the tensile properties in the three groups. However, a negative correlation was found between the tensile stress at failure of the anterosuperior labrum and age in DDH group (P = 0.004, R2 = 0.392). In addition, the pathological findings revealed that the degeneration of the anterosuperior labrum was more severe than that of the posteroinferior labrum in the DDH group. Our results further revealed that the tensile stress at failure of the anterosuperior or posteroinferior labrum was frailer than that of the posterosuperior labrum in a similar group in a previous study. Conclusions The degenerative changes observed in the anterosuperior labrum may influence the occurrence of labral tears in DDH.