Regional material properties of the human hip joint capsule ligaments

The hip joint capsule functions to constrain translation between the femur and acetabulum while allowing rotational and planar movements. Despite the crucial role it plays in the pathogenesis of hip instability, little is kno wn about its biomechanical properties. The goal of this study was to determ ine the regional material properties of the iliofemoral and ischiofemoral l igaments of the capsule. Ten human cadaveric specimens of each ligament were tested to failure in te nsion. The stress at failure, strain at Failure, strain energy density at f ailure, toe- and linear-region elastic moduli, and the Poisson's ratio were measured for each ligament. The strain to Failure was greatest in the ischiofemoral ligament, while no significant difference was noted in failure stress by region or ligament. T he Young's moduli of elasticity ranged from 76.1 to 285.8 MPa among the dif ferent ligaments, and were generally consistent with properties previously reported for the shoulder capsule. The elastic moduli and strain energy den sity at failure differed by region. No significant differences in Poisson's ratio were found by region or ligament. The average Poisson's ratio was ap proximately 1.4, consistent with anisotropic behavior of ligamentous tissue s. Understanding the material properties of the hip capsule may help the ortho paedic surgeon better understand normal ligament function, acid thereby cho ose a surgical approach or strategy of repair. Furthermore, knowledge of th e normal mechanical function of the hip capsule ligaments could assist in t he evaluation of the success of a repair. (C) 2001 Orthopaedic Research Soc iety. Published by Elsevier Science Ltd. All rights reserved.