Establishment And Evaluation Of The Animal Model Of Denervated Osteoporosis

Objective: By directly cutting the left brachial plexus to rabbit left upper limb disability in order to establish the animal model of disuse osteoporosis by direct surgical intervention,to investigate the effect of peripheral nerve injury or disease of the local bone,so as to provide a good experimental vehicle for the study of disuse osteoporosis and nerve growth factor on drugs.Methods : 8 month old male New Zealand white rabbits were randomly divided into 3 groups(n=8).The incision was taken from the left mandible through the neck down to the 2/3 skin in the middle of the pectoralis major muscle.The pectoralis major muscle was exposed,and the pectoralis major and the pectoralis minor muscle were severed and the left clavicle was exposed.Carefully separate subclavian tissue(if necessary,cut off the clavicle by a wire saw),Under the microscope,the total brachial plexus nerve was dissected to the nerve root hole and clipped closely to the proximal root.The nerve root was excised from the proximal part of the nerve root to the distal part for about 2 cm.The brachial plexus root injury model was constructed as an experiment side.The right side to take the same surgical method to expose the brachial plexus to the nerve root hole,but the brachial plexus nerve was not cut off or injured,which was used as the sham operation control group.Bone mineral density(BMD)of bilateral humerus was measured by dual energy X-ray absorptiometry at 4,8 and 12 weeks postoperatively respectively.Eight experimental animals were sacrificed at the above three time points,and after measuring the humerus length,it was fixed in 10% neutral formalin solution,and then subjected to three-point bending test on a WDW-20 electronic universal testing machine to measure the biomechanical properties.The left and right humerus marks of equal length in each group were placed on an electronic scale with accuracy of 0.0001 grams to weigh their dry weights.The proximal humeral metaphysis was selected on both sides of experimental group and Sham operation control side,HE staining and Masson staining were performed respectively,and the morphological changes of bone in each group were observed.Results: Compared with the Sham operation control side,As the bone denervated nutrition dominated the extension of time,the experimental side of the bone mineral density and bone dry weight decreased,with significant statistical difference(P <0.05).Each set of experiments the maximum side load,modulus of elasticity,flexural strength,elastic stress,elastic strain,maximum stress and maximum strain values were lower than the control side,the difference was statistically significant(P <0.05);Comparison between the experimental groups in each side group,the longer the bone denervation of the time at their disposal,each of the variable value decreased more significant degree,the more significant difference(P<0.05).The thickness of trabecular bone,the number of trabeculae,the space between trabeculae,the number of bone trabecular junction points,the size of medullary cavity and the number of osteoclasts in each group were significantly decreased compared with the control side..Masson staining showed that the number of dystrophin in the denervated limbs decreased significantly with the increase of the waste time.Conclusions: Brachial plexus neurotomy is an effective way to establish the animal model of osteoporosis for denervation.With the prolongation of the innervation time of denervation,the density,dry weight and strength of bone are increased.The biomechanical properties and histomorphology of the tissues were changed in different degrees,the bone mass and the ability of bone regeneration were decreased,the brittleness of bone and the risk of fracture were greatly increased.