Osteoporosis influences the middle and late periods of fracture healing in a rat osteoporotic model.
OBJECTIVE
To evaluate the influence of osteoporosis on the middle and late periods of fracture healing process through observing the histomorphological changes, bone mineral density and biomechanical properties in ovariectomized rats.


METHODS
Eighty-four female SD rats of 4 months old were randomly divided into osteoporosis group and sham operation group, 42 in each. Rats in osteoporosis group were performed ovariectomy operation while those in sham operation group were given sham operation. A midshaft tibia fracture model was established 10 weeks after ovariectomy. Tibias were harvested 2, 4, 6, 12, 18 weeks after fracture for bone mineral density, histomorphological and biomechanical evaluation.


RESULTS
Compared with the sham operation group, callus bone mineral density was 12.8%, 18.0%, 17.0% lower in osteoporosis group 6, 12, 18 weeks after fracture, respectively (P<0.05); callus failure load was 24.3%, 31.5%, 26.6%, 28.8% lower in osteoporosis group, and callus failure stress was 23.9%, 33.6%, 19.1%, 24.9% lower in osteoporosis group 4, 6, 12, 18 weeks after fracture, respectively (P<0.05). In osteoporosis group, endochondral bone formation was delayed, more osteoclast cells could be seen around the trabecula, and the new bone trabecula arranged loosely and irregularly.


CONCLUSIONS
Osteoporosis influences the middle and late periods of fracture healing in the rat osteoporotic model. The impairment is considered to be the result of combined effects of prolonged endochondral calcification, high activated osteoclast cell and the deceleration of the increase in bone mineral density.
Wang
Jian-wei
JW
Department of Orthopaedics, Second Affiliated Hospital, Medical College of Zhejiang University, Hangzhou 310009, China.
Li
Wei
W
Xu
Shao-wen
SW
Yang
Di-sheng
DS
Wang
Yun
Y
Lin
Min
M
Zhao
Guang-feng
GF
D000818:Animals; D001696:Biomechanical Phenomena; D001835:Body Weight; D015519:Bone Density; D004195:Disease Models, Animal; D005260:Female; D017102:Fracture Healing; D010024:Osteoporosis / Q000150:complications* / Q000473:pathology / Q000503:physiopathology*; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D012016:Reference Values; D013978:Tibial Fractures / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology*