A biomechanical basis for tears of the human acetabular labrum.

ABSTRACT

OBJECTIVE: Acetabular labral tears predominantly affect young patients and are a source of hip pain in the athlete. Four causes of the initiation of labral tears have been proposed; trauma, hypolaxity of the anterior capsule, dysplasia and bony impingement. A further cause could be reduced biomechanical properties in the area most susceptible to tears. However, no work has defined these properties. DESIGN: 32 compressive and 32 tensile test samples were harvested from fresh-frozen cadaveric acetabula. The labrum was divided into eight areas to allow comparison around its circumference. Semiconfined compressive testing and tensile testing were performed at a displacement rate of 10 mm/min in a controlled environment of 100% humidity at 37 (SD 1) degrees C. SETTING: Cadaveric study. RESULTS: The mean compressive stiffness was 31.75 (SD 16.7) MPa, and the mean tensile elastic modulus was 24.7 (SD 10.8) MPa. The anterosuperior region had a significantly lower compressive elastic modulus than either of the posterior quadrants (p<0.05) and a significantly lower tensile modulus to the anterioinferior area (p<0.05). CONCLUSIONS: The biomechanical properties in the anterosuperior region may be a contributing factor to the initiation of labral tears.