Bone density does not reflect mechanical properties in early-stage arthrosis

Subchondral cancellous bone specimens were removed from 10 human postmortem early-stage arthrotic proximal tibiae (mean age 73 (63-81) years) and 10 a ge- and gender-matched normal proximal tibiae, The early-stage arthrosis wa s confirmed histologically and the specimens were divided into 4 groups: me dial arthrosis, lateral control, normal medial and normal lateral controls. The specimens were tested in compression to determine mechanical propertie s and then physical/compositional properties. Compared to the normal medial control, we found reductions in ultimate stre ss, Young's modulus, and failure energy, and an increase in ultimate strain of arthrotic cancellous bone. Bone volume fraction, apparent density, appa rent ash density, and collagen density were higher in cancellous bone with arthrosis, but no differences were found in tissue density, mineral and col lagen concentrations between arthrotic cancellous bone and the 3 controls. None of the mechanical properties of arthrotic cancellous bone could be pre dicted by the physical/compositional properties measured. The increase in b one tissue in early-stage arthrotic cancellous bone did not make up for the loss of mechanical properties, which suggests a deterioration in the quali ty of arthrotic cancellous bone.