| Disuse osteoporosis is caused because of mechanical stress works on bone decreased, which lead to bone quality decrease and local or the whole body bone mass lose. Weight loading and movement are mechanical stimulus on skeletal growth, reconstruction and maintenance of bone mass. The low level or totally lose of this kind of mechanical stimulus on bone would induce bone resorption mediated by ostoclast and would inhibit bone formation mediated by osteoblast, which lead to the lost of bone mass. This kind of disuse ostoporosis progresses according to the changes of time. There always seldom has clear exterior appearance untill pathological fracture happens. Lying in bed needed by therapy, paraplegia after spinal cord injury or paresis of the lower extremities, hemiplegia or light hemiplegia caused by stroke, local immobilization caused by plaster to treat bone fracture or traumaand weightlessness all could lead to disuse osteoporosis, of which, lying in bed and immobilization of the extremities are the main cause of disuse osteoporosis. Disuse osteoporosis is quite common in clinical. This kind of disease always brings body pain to the patient and economic burden to the society.1. Establishment and its appraisement of disuse osteoporosis animal model.- Botulinum toxin A (BTXA) could works on periphery nerve endings and the synapses where nerve and muscle connect with each other and inhibit the frontal membrane of the synapses from releasing nerve medium acetylcholin, which lead to muscle relaxant paralysis. According to this character, we established disuse osteoporosis rat model. BXTA was injected into rat quadriceps femoris muscle, which caused acetylcholine inhibition and lead to one side quadriceps femoris muscle paralysis. Disuse osteoporosis model was then established. After 1 to 3 months observation, the model was detected by biochemical, biomechanical and bone norphometry methods and the measurement of bone density. Compared with the control animals, dry weight of femur in the experimental group decreased 10.7-18%, the weight of bone ash decreased 14.9-21.3%. The femoral biggest loading, energy resorption, elastic modulus and the utmost strength decreased 12.2-44.7%. About the static parameters, bone volume(BV/TV%) decreased 19-30.4%, the thickness of bone trabaculae (Tb.Th) decreased 15.9-23.8%, the number of bone trabaculae (Tb.N) decreased 17.2-25.7%, the separate degree of bone trabaculae (Tb.Sp) increased 25.5-34%. As long as the development parameter, bone mineral deposition rate decreased 24.1-30.1%. Bone density of the disused femur decreased 11.1% and 15.5%, respectively. According to the changes of above parameters, injection of BXTA into quadriceps femoris muscle could successfully establish rat disuse osteoporosis model with corresponding bone mass and biomechanical changes. Of the bilateral rat femurs in the model, the bone density, the content of bone minerals and femoral mechanical character in the disused side all lower than that of the normal side. The difference was obvious statistically (p<0.05). The above parameter of the normal side has no obvious difference with that of the normal animals. The parameter of the lumber spine in the model groups has no difference compared with that of the normal animals. The above result suggest that one side disuse of the extremity would not lead to the decrease of bone mechanical character and would not lead to disuse osteoporosis at the normal active extremities and the spine. The reason maybe the normal extremities and the spine still have normal activity.2. The effect of diphosphate on the prophylaxis of disuse osteoporosis taken orally. Disuse osteoporosis animal models established according to the method above were divided randomly into experimental group and control group. The experimental animals were given diphophate orally and animals in the control group only given saline orally. Normal animals were given saline orally as the normal control group. Norphometry, biomechanical methods and bon...
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