BACKGROUND:It is very nscessary for the prevention and treatment of ostaoarthritis(OA)to understand the tensile mechanical properties of lateral collateral ligaments(LCLs)of knee joints with osteoarthritis,while reports on it are still few.OBJECTIVE:To compare the LCL tensile mechanical property indexes of knee joints between normal animals and OA medels established for this purpose,and to provide qualitative and quantitative referential data about effects of OA on the LCL tensile mechanical properties of animal knee joints.DESlGN,TIME AND SETTING:A randomized controlled trial was finished at the Mechanical Expedmental Center of Jilin University from December 20th to 30th in 2008.MATERIALS:A total of 20 male SD rats of 6 months old were divided into a normal control group and a model group,with 10ones in each group.METHOOS:Rats in the model group were copied into OA models.after which test on tensile was performed to each of the ten rats in the two groups at the speed of 5mm/min on Universal Testing Machine,Shimadzu.Data obtained from the test were processed in polynomial though least square method.MAIN OUTCOME MEASURES:Tensile maximum load.maximum displacement,maximum stress,maximum strain and stress-strain curves.RESULTS:The tensile maximum load,maximum stress,maximum displacement and maximum strain in the normal control group and the model group were(12.754±2.795)N,(27.681±5.832)MPa,(2.754±0.707)mm,(11.679±2.373)%and (7.183±1.817)N,(16.162±3.403)MPa,(1.827±0.768)mm,(8.019±2.811)% respectively,from which we could see that each index in the normal control group was greater than that in the model group obviously (P＜0.05).CONCLUSION:The tensile maximum load,maximum stress,maximum displacement and maximum strain all decreased after OA,which indicates that osteoarthritis has certain effects on tensile mechanical properties of LCLs of knee joints as well as stress relaxation.

BACKGROUND:Thoracic or lumbar spine fracture and dislocation mainly treated by internal/external fixation devices with surgical methods.Fixation methods in treating spine fracture and dislocation is an important subject for scholars.OBJECTIVE:To quantitative analyze the treatment of spinal fracture and dislocation using pedicle screw and plate fixation,and to provide mechanical parameters for clinical application.METHODS:Shimadzu electronic universal testing machine was used to simulate L_1 lumbar fracture and dislocation treated by plate fixation and pedicle screw fixations,specimens were underwent flexion,extension,compression,as well as torsion tests,with speed of 5 mm/min.The torsion test was performed on the torsion machine with speed of 0.05 (°) / s.All the experimental data were analyzed by statistical analysis and paired t test.RESULTS AND CONCLUSION:The results demonstrated that the outcomes of compression test had no significant differences between 2 groups (P>0.05).The left and right torsion angle of the pedicle screw fixation group was smaller than that of the plate fixation group (P<0.05),and the flexion and extension displacements was smaller in the pedicle screw fixation group than in the plate fixation group (P<0.05).It suggested that plate fixation is worse than pedicle screw fixation,while pedicle screw fixation is conductive to bone healing,thus,pedicle screw fixation is a better internal fixation device.

Objective To compare the mechanical properties of animal knee lateral collateral ligament tensile between the normal and atherosclerotic animal model of osteoarthritis,and to identify if there are effects of osteoarthritis on the animal knee lateral collateral ligament tensile mechanical properties.Methods The experimental rats were provided by the Changchun High Medical Center for animal experiments.The 6-month-old male rats were the copying model of osteoarthritis.The tensile experiments at electron Shimadzu universal testing machine was carried out on ten of normal and pathological specimens.The speed of the tensile experiments was 5mm/min.Experimental data were processed by polynomial least square method.Results The tensile maximum load of normal control group was(26.12?4.00)N,maximum stress was(40.93?6.71)MPa,maximum displacement was(3.08?0.77)mm,and maximum strain was(9.51?2.36)%.The tensile maximum load of model group was(12.05?2.07)N,maximum stress was(21.28?4.17)MPa,maximum displacement was(2.32?0.56)mm,and maximum strain was(7.04?1.79)%.Conclusion The tensile performance of normal control group was significantly greater than that of the model group(P