Establishing an easily accessible testing system for bone hardness

Abstract

Introduction: Hardness and Young’s modulus are two mechanical properties that influence bone quality, such as bone hardness and Young’s modulus. Bone hardness refers to the ability of bones to resist the pressing of hard objects into their surface, and Young’s modulus quantifies the shape-independent resistance of bone to elastic (reversible) deformation. Objective: To examine the true bone hardness intraoperatively, it is necessary to establish an easily accessible testing system for bone hardness. Materials and Methods: The trabecular hardness of four human cadaveric samples of proximal tibia and distal femurs with osteoporosis were tested with shore durometer. The femoral head and the tibia joint surface were surgically removed to mimic the joint replacement surgeries. 24 tests of the hardness were performed for each sample. The bone densities were measured using clinical CT with a phantom. Results: The average trabecular bone hardness for each sample was 40.4 HD, 31.0 HD, 38.2 HA, and 57.7 HA. By calculating the difference (∇) between average trabecular bone hardness (α) and average trabecular bone hardness where we eliminated abnormal testing value during the calculation process (β), the frequency of those points with abnormal hardness value could be well reflected. Conclusion: Large variance exists in the same sample for different testing spot of the trabecular at the surgical site and a high degree of consistency exists in the same testing spot for different sample. Thus, the current assumption of measuring bone quality by hardness and establishing an easily accessible testing system for bone hardness is reasonable.