[Objective]To investigate the biomechanical pathogenesis of lumbar spondylolysis,and to provide theoretical basis and scientific foundation for the treatment prevention of lumbar spondylolysis.[Method]The three dimension analytical method of finite element was used to set up a 3-D finite element model of whole lumbar vertebral column and to investigate the stress distribution of seven different posture in isthmus of lumbar spine.[Result]The stress of vertebral isthmus increased from L_(1~5) gradually.The concentration phenomenon of the stress prominently appeared in anteflexion and postextension,with the largest postextension position.[Conclusion]Spondylolysis may be caused by the long-term hazard stress on the lumbar isthmus,in high relation with postextension of lumbar spine.

Objective To adopt a three-dimensional limited element analytic method to research into the cause and mechanism of the complications taking place after resection of head radius.Method To adopt a three-dimensional limited element analytic method to research into the stress transmission action of the head radi-us and the distribution alteration of the stress transmission after resection of head radius impacting on the stability of elbow and wrist.Result In normal cases,the stress value transmitted via head of radius takes 58% of the stress placed,36.85% via humeroulnar joint.The head of radius places a leading role in the stress transmission of the elbow joint.After rasection of the head of radius,the lateral of humeroulnar joint bears about 43% of the stress placed while the medial part bears about 21.6% of the stress.To compare with that before the resection of the head of radius the stress on the lateral is obviously increased more than the medial part.Conclusions The head of radius places a leading role in the stress transm ission of the el-bow joint.The resection of the head radius breaks the normal distribution of the stress on the elbow joint and produces great effect on the stability of the elbow joint and wrist joint.Therefore,in clinics we should pay great attention to the indication of rasection of the head of radius.

BACKGROUND: Fracture of humeral ectocondyle is a kind of articular epiphyseal fracture. It is one of the most prevalent disorder of cubital articulation. The occurrence of fracture and the mechanical mechanism of treatment is not very well cognized in clinic.OBJECTIVE: To analyze the stress distribution of the humeral ectocondyle in different postures so as to investigate the treatment mechanism of the humeral ectocondyle fracture.DESIGN: Computer simulation study on stress.SETTING: Department of Experimental Mechanics, Fuzhou University, and Department of Orthopedics, Third Affiliated Hospital of Peking University.MATERIALS: This experiment was conducted in the Fujian Experimental Mechanic Committee of Fuzhou University between January 2000 and December 2002. Humerus from a 6-year-old. corpse (Provided by the Department of Anatomy of Fujian College of Traditional Chinese Medicine). Instruments were computer, SUPER-SAP93 software, material sickle and measuring instrument and so on.METHODS: 9 kinds of loading conditions were simulated and added on three dimensional finite elemental model of humerus in SUPER-SAP93software, and then the stress distribution was filed out and analyzed.MAIN OUTCOME MEASURES: The average Mises stress of lateral condylar area and humeral trochlea area.RESULTS: At flection posture of elbow, the average Mises stress of lateral condylar area was the largest while at extension posture the stresses of nodes affected by extensor tendon were larger than those of lateral condyle.CONCLUSION: At the flection posture of elbow, the fracture of lateral condyle of humerus was resulted from c9llision occurring when radius and ulna struck humerus while at extension posture, it was chiefly due to extensor tractive force. We can use extensor tractive force to reduce the fracture of lateral condyle and avoid extensor tractive force to fix it.