Comparison of microstructural and mechanical properties of trabeculae in femoral head from osteoporosis patients with and without cartilage lesions: a case-control study

Background: Degeneration of cartilage will change load distribution, affecting bone remodeling progress and trabecular structure and strength. However, in human primary osteoporosis, whether cartilage lesions would also affect properties beneath trabecular bone remains unknown. In this study, we explored the differences in local trabecular properties between osteoporosis patients with and without cartilage lesions. Methods: Eighteen pairs of femoral heads with and without cartilage lesions in a weight-bearing area were collected from senile femoral neck fracture patients. The Mankin score and glycosaminoglycan (GAG) content were used to evaluate the severity of the cartilage lesions. Micro-CT and compression tests were used to obtain structural and mechanical characteristics of each trabecular column. Multivariate linear regression was performed to evaluate the association between mechanical parameters and the degree of cartilage lesion. Results: In osteoporosis patients with cartilage lesions, the bone volume fraction (BV/TV) and trabecular thickness (Tb.Th) of the trabecular column were significantly higher than that of osteoporotic control patients (all P < 0.05), while the Young's modulus was lower (P = 0.024). Multivariable linear regression indicated that in both groups, bone mineral density (BMD) significantly correlated with Young's modulus (all P < 0.05). While in patients with cartilage lesion, GAG content was also correlated with Young's modulus (standardized coefficient 0.443, P < 0.01). Conclusions: Osteoporosis patients with cartilage lesions exhibited a weaker mechanical property of trabeculae. The intimate association of cartilage lesions and impairment of trabecular mechanical properties indicate that cartilage and trabeculae belong to an interdependent functional unit. Previously proposed adaptive mechanisms in osteoarthritis might also be applicable to the progression of osteoporosis.