Ultrasound Parameters for Human Osteoarthritic Subchondral Bone ex Vivo: Comparison with Micro-Computed Tomography Parameters

The aim of this study was to identify ultrasound parameters reflecting subchondral porosity (Po), subchondral plate thickness (Tpl) and bone volume fraction at the trabecular bone region (BV/TVTb). Sixteen osteoarthritic human lateral femoral condyles were evaluated ex vivo using a 15-MHz pulsed-echo ultrasound 3-D scanning system. The cartilage-subchondral bone (C-B) surface region (layer 1) and inner subchondral bone region (layer 2) were analyzed; we newly introduced entropy (ENT) and correlation (COR) of ultrasound texture parameters of the parallel (x) or perpendicular (z) direction to the C-B interface for this analysis. Po, Tpl and BV/TVTb were evaluated as reference measurements using micro-computed tomography. ENTL1x (ENT of layer 1, x-direction) and ENTL1z were significantly correlated with Po (both r values = 0.58), CORL2x with Tpl (r = -0.73) and CORL2z with BV/TVTb (r = -0.66). These are efficient indicators of the characteristics of osteoarthritis-related subchondral bone; the other texture parameters were not significant.