CHANGES IN BONE IN A MODEL OF SPINAL-CORD INJURY

Bone calcium, histomorphometry, and mechanical strength were evaluated in a model of spinal cord injury. Cortical bone area and rates of for mation and apposition at the tibiofibular junction (TFJ) and midshaft of the humerus were measured at 35-42, 42-77, and 77-94 days after tra nsection of the spinal cord. All comparisons were between the animals with a spinal lesion and control animals. A 0.34% difference in the le ngth of the tibia of the two groups of animals was observed, the dry w eight of the tibia was 28.4% less in rats with a lesion, and there was no significant difference in the amount of calcium per milligram of b one. At 35 days after surgery, the cortical area in the midshaft of th e humerus was slightly less (11%) in rats with a lesion, but by 94 day s there was no difference in cortical or medullary area. Tle final (da y 94) cortical area at the TFJ in rats with a lesion was less than tha t in the controls. Bone formation at the TFJ was similar in both group s in the period of 35-42 days and was similar at 77-94 days in the ani mals with a lesion, and rates of formation and apposition were greater in the humerus of rats with a lesion; the rates did not differ signif icantly between groups at either site. At 94 days, trabecular bone are a in the tibial metaphysis was 41% less in rats with a lesion. Mechani cal parameters were significantly less in the femora, but not the hume ri, of rats with a lesion.