Abstract:

BACKGROUND: Studies have demonstrated that osteoporosis is a complex pathophysiological process involves changes of type Ⅰ collagen number and physical or chemical properties. However, reports addressing correlations between type Ⅰ and Ⅱ collagen expression are few.  
OBJECTIVE: To disclose the change rules of type Ⅰ and Ⅱ collagen protein during osteoporotic fracture healing in rats and the correlation of them with mechanical strength.
METHODS: Rats were randomly divided into osteoporotic fracture and general fracture groups. Rats in the former group received ovariectomy. The expressions of type Ⅰ, Ⅱ collagen were observed by Western blot at 1, 2, 4, 5, 8 and 12 weeks. The bone mineral density was examined by dual-energy X-ray absorptiometry, and biomechanical testing were performed at 4, 8, 12 and 16 weeks postoperatively.
RESULTS AND CONCLUSION: There were significant differences between the osteoporotic fracture group and general fracture group in type Ⅰ and Ⅱ collagen expression and bone mineral density at different time points after injury (P < 0.05). With the injury time prolonged, the downward trend was more obviously. The type Ⅰ and Ⅱ collagen were correlated with maximum torque, elastic modulus, and maximum torsion angle in the osteoporotic fracture group (P < 0.05). The results showed that abnormal secretion of type Ⅰ and Ⅱ collagen osteoporotic fracture healing decreases mechanical strength and reduce the quality of fracture healing, which is the main reason for re-fracture.