The Analysis Of Risk Factors Of Spondylolysis By Measurement Of Isthmic Strain

Objectives:The purpose of the present study was to evaluate the effects of postures on the isthmic when the specimens were applied with constant bending moment.The evaluation will be helpful in estimating the risk factors of spondylolysis.Methods:Two motion segments(C₃-C₅,C₆-T₁) were dissected from the porcine cervical spines.Each specimen was loaded with bending moment of 1.2J under the postures of flexion,extension,neutral position,left /right lateral bending,and extension/flexion combined with left/right lateral bending,respectively.The strain gages attached to the bilateral isthmic of middle vertebrae were used to measure the strain response in situ.T-test was used to exam the significantly effective postures and estimate the risk factors of spondylolysis.Results:The isthmic strain was greatest when specimens were under extension combined with lateral bending,followed by lateral bending,extension,flexion combined with lateral bending,flexion,and neutral position.Any one of the former three postures led to much greater isthmic strain than any one of the latter three postures.As for contralateral side,the greatest strain occurred when the specimens were under extension combined with lateral bending.The difference of ipsilateral and contralateral isthmic strain was significant when the specimens were under lateral bending and extension combined with lateral bending.Conclusion:Extension,lateral bending and extension combined with lateral bending appear to endanger the isthmic.The latter two postures are less highlighted before; however,the present study proves they should be taken into considerations when it comes to the prevention and treatment of the spondylolysis.