Load-deformation properties of the ligament of the head of femur in situ.

The ligament of the head of femur (LHF) or ligamentum teres has been reported to tense during hip adduction and also to provide mechanical stability to the joint. LHF injury is more common in females and also in right hip joints compared with left ones. Although this could be due to leg dominance, pelvic size or muscle strength, there is no study that has looked into these differences. This cadaveric biomechanical study aimed to compare potential differences in the mechanical behavior of the LHF between neutral and 20° adducted hip joints, sex, and sides. Tensile tests of the LHF were performed on 25 hip joints (mean age at death of 85.7 ± 7.5 years; 9 females, 4 males; 13 left, 12 right), positioned either neutrally or in adduction. The maximum force required to rupture the ligament, its strain at failure, tensile strength, linear stiffness, and elastic modulus were obtained and statistically compared between analysis groups. The maximum force the LHF could withstand before rupture averaged 57 ± 37 N, strain at failure of 59 ± 33%, tensile strength of 2.9 ± 1.8 MPa, linear stiffness of 5.4 ± 3.5 N/mm, and elastic modulus of 7.2 ± 3.8 MPa. The LHF length at failure was significantly greater in males compared with females (P = 0.02). Irrespective of joint position, there were no statistical differences in the stress-strain properties of the LHF between females and males, or sides. There may be other anatomical, functional, and demographic factors that could render the ligament tissue vulnerable to injury in these groups. Clin. Anat., 33:705-713, 2020. © 2019 Wiley Periodicals, Inc.