Microstructural properties of the distal growth plate of the rabbit radius and ulna: biomechanical, biochemical, and morphological studies.

The purposes of this study were to define the tensile properties of each zone of the rabbit growth plate and to correlate them with the microarchitecture and biochemical composition of the zones. The epiphysis-growth plate-metaphysis complex was obtained from the radius and ulna of 20 8-week-old rabbits. Four dye markers were placed on the growth plate. The complex was loaded to failure with a tensile testing machine, and the strain behavior was recorded simultaneously with a microscope, a charge-coupled device camera, and a video dimension-analyzer system. The collagenous fiber architecture of each zone was examined with a microscope, and the collagen content of each zone was also determined. The tangent modulus of the resting zone was 75% stiffer than that of the other two zones. The highest values for strain at failure and energy absorbed to failure were observed in the hypertrophic zone, and the total collagen content was highest in the proliferating zone. The collagen fibers were more randomly aligned in the resting zone than in the other two zones. The diversity observed in the microarchitecture of the rabbit growth plate correlates with the zone-dependent differences in its mechanical properties.