Objective: To describe changes to the cancellous structure of femoral bone from patients with severe primary osteoarthritis by comparison with age and sex matched controls.
Method: Specimens were taken from 18 male and 18 female pairs. One of each pair was a normal control, the other having severe primary osteoarthritis which required hip arthroplasty. Undecalcified cancellous bone blocks were embedded in resin, sectioned and impregnated with silver. Histoquantitation was performed using image analysis. Using a plate model for the trabecular structure of bone, an estimate was made of bone volume, bone surface, trabecular thickness, trabecular separation and trabecular number.
Results: In osteoarthritis, pooled male and female data show a significant decrease in trabecular number together with an increase in trabecular thickness and separation. The statistical variance in the histomorphometric variables for each of the study groups was calculated and expressed as the ratio of osteoarthritic to control. This ratio shows that the variance of the osteoarthritic groups is significantly increased for each variable in the pooled data. The same trend is evident in the male and female groups.
Conclusions: This quantitative study of cancellous bone architecture in the femoral head, infero-medial to the fovea, has found increased trabecular thickness and decreased trabecular number in patients with primary osteoarthritis. Increased morphometric variance has shown that severe osteoarthritis, contrary to osteoporosis, is associated with heterogeneous bone structures. These findings provide some basis for understanding how osteoarthritis may contribute to the prevention of osteoporotic fracture.