Abstract: Objective To study the changes of biochemistry indexes in blood serum and bone mineral density (BMD) of secondary osteoporosis after spinal cord injury (SCI) in rats. Methods 120 male Wistar rats were divided randomly into 12 groups (n=10). The rats in control groups were only removed larmina with dura intact, without spinal cord injury at the level of the tenth thoracic vertebrae, the rats in experimental groups were also removed larmina, then paraplegic model was made by the method of Allen's (60gcm). The changes of biochemistry indexes in blood serum and BMD were observed. Results Compared with control groups, the concentrations of alkaline phophatase (ALP) were decreased at the 1st and the 3rd week in experimental groups (P<0.05), increased significantly at the 7th week in experimental groups (P<0.01). the concentrations of phosphorus were increased at the 1st and the 2nd week in experimental groups (P<0.01); the concentrations of calcium were increased at the 1st ， 2nd and 3rd week in experimental groups (P<0.01); then the concentrations of calcium and phosphorus declined to a little higher than normal. Compared with control group, the BMD of humerus were decreased at the 3rd, 7th and 11th week in experimental group (P<0.01), especially at the 3rd week; BMD of femur was decreased at the 7th week in experimental group (P<0.01), there was no difference between the 11th week group and control group (P>0.05). BMD of tibia was decreased at the 7th and 11th week in experimental group (P<0.01), but there was no difference between the 7th and the 11th week in experimental groups. Conclusion The changes of biochemistry indexes in blood serum fluctuated after spinal cord injury can be found , osteoporosis is found in bones both superlesion and sublesion, and bone superl esion rehabilitate early in paraplegic rats

Key words: Wistar, spinal cord injuries, osteoporosis, bone density