Establishment Of Experimental Rabbit Models Of Nonunion In The Study On Biological Mechanism Of Nonunion Treatment With The “accordion Technique”

Objective: The “accordion technique” is a new technique developed in recent years for treatment of bone nonunion. This technique has became a kind of relatively simple、minimally invasive and effective therypy method and very good prospects in clinical application.At present,the "accordion technique" in the treatment of nonunion of fracture has been in a few clinical cases of application and success, but still lacks of corresponding research on basic theory of concrete.This thesis intends to make a study of the theory on the basis of the technical,and provide a theoretical basis for the clinical application of the technology.The research first needs to establish an objective, reliable animal model.This experiment is the first part of the study on biological mechanism of Nonunion Treatment with the “accordion technique”.To successfully establish an objective and reliable experimental animal model of bone nonunion.To lay the experimental foundation in the study on biological mechanism of nonunion.Methods: This study selected healthy New Zealand white rabbits.The rabbit models of femoral bone nonunion were caused by the bone defects.The method is as follows: 1 Rabbit femurs were cutted as specimens to observe the morphology and the related indicators were measured:The study randomly selected 5 healthy New Zealand white rabbits,without limiting the female and male.5 rabbits were executed to achieve 10 complete femur specimens.The morphological features of the femur of rabbits were investigated and the femur length、the transverse diameter of the femoral middle section, the sagittal diameter of thefemoral middle section were measured. All the measured data were statistically analyzed, used to guide the preparation of model. 2 The pre experiment:To observe the anesthesia of the rabbits、the exposure of the operation incision、the method and technique of the placement of outside fixing frame and the osteotomy. 1 New Zealand rabbit was randomly selected to take part in the pre experiment.All the experimental rabbits were anesthesia through ear vein injection.The operation area was disinfectioned by iodophor,and sterile surgical drapes were shopped.Taking the experimental rabbit unilateral femoral lateral central longitudinal incision,and turning the incision of skin, subcutaneous tissue and fascia. The muscle gap between the femoral head two muscle and vastus lateralis muscle and expose the middle of the femoral shaft was dissectioned. The length of femur osteotomy was marked. The length of femur osteotomy of one thigh was 10 mm and the length of femur osteotomy of the other thigh was 15 mm.4 pieces of fixed needle were respectively fixed on both sides of bone osteotomy.The aperture was 1.5mm and interval was 5mm.Then the external fixation was connectted.The bone defects of 10 and 15 mm were made respectively in the femoral shafts.Muscle and skin were sutured by 4-0 suture. 3 Establishment of New Zealand white rabbit models of femoral bone nonunion:10 New Zealand white rabbits were randomly divided into 2 groups :the control group and the experimental group.According to the operation method of the pre experiment,the experiment were conducted.The osteotomy length of the experimental group was 15 mm. Stump periosteal was stripped and osteotomy stump was closured with bone wax.The osteotomy length of the control group was 10 mm.Stump periosteal was reserved,and osteotomy stump was not closured.X-ray was taken for all the specimen from the matched group and the experimental group at 8 weeks,12 weeks after the defects were treated. At the same time,the condition of defect heal was observed. The histology condition was observed at 8 weeks, 12 weeks after the defects were treated.Results:1 The data results of anatomical study of the rabbit femur:The average length of the femur is 93.89mm;The average length of the diameter of the femur is 7.48mm;The average length of sagittal diameter of the femur is 5.89 mm.The cross section shape of the middle femur is flat ellipse.Therefore,the thread needles of diameter 1.5mm are chosen.They do not cause bone splitting.After femoral osteotomy,there is still sufficient length placed external fixator. 2 Operation experiences of the pre experiment:Operation incision should be located in the anterior lateral of rabbit.Femur is revealed easily, the bleeding is less.Femur bone of rabbit is more brittle.The entry point should be located at the midpoints of wide Department of backbone. The drilling operation should be gentle. 3 The results of establishment of animal models:The X-ray results after 12 weeks of operation:There are 4 cases have a large amount of bone callus appeared in the femoral defect,canalization of the medullary cavity appears again,and realized the osseous healing at last in the control group.There are 1 cases have the fuzzied fracture line, a small amount of callus formation in the control group.There are 5 cases all without continuous callus growth in the femoral defect area, hardened in the broken end, closed in medullary cavity in the experimental group.The histology condition after 12 weeks of operation:There are 4 cases have maturation development of bone tissue, the uniform of the morphology and size at last in the control group.There are 5 cases all have fibrous connective tissue in the bone defect,and lack of bone formation in the experimental group.Conclusion: The method of the length of osteotomy is 15 mm,bone stump is sealed with bone wax,and external fixation maintain the osteotomy length can establish the experimental rabbit models of nonunion.This method is reliable, simple, and repeatable.It can lay the experimental foundation in the study on biological mechanism of nonunion with the "accordion technique".