Biomechanical Study Of The Endplate Angle Of Pedicle Screw Imbedding

Objective: To evaluate the initial stability,effective length,stiffness stability in different directions and safety of the treatment of lumbar burst fracture with the angle of the pedicle screw under the endplate,and to provide a theoretical basis for clinical application.Methods: 16 adult embalmed T12~L5 samples were selected as the research object,which there were 10 males and 6 females,The left and right sides of each specimen were randomly divided into the control group and the observation group,each group of 96 sides.The control group used the traditional pedicle screw placement and endplate parallel way,namely crista lambdoidalis vertex method;the observation group adopted the endplate angle of pedicle screw imbedding,pedicle screw and end plate at an angle of 30 degrees.which with convenient operation,and was not easy to break the le vertebral endplate.Before and after the test,X-ray radiography was performed on the vertebral body,pedicle screw placement of each vertebral body met the requirements,and no screw overflow or abnormal angle was found.After the test,all the screws were located in the pedicle of the vertebral canal,and no obvious damage to the surrounding bone wall was found.The effective fixation length of two groups of specimens were measured,and the effective fixation length difference between the two groups was compared;the lateral flexion stiffness values of 5 physiological activities of two groups were respectively tested in axial compression,flexion,posterior extension,decompression side lateriflexion and decompression side contralateral flexion,and compared specific changes;the axial pull out test of two groups of specimens were tested,and the axial pullout capacity of the two groups were compared.Results:(1)the effective fixation length: the observation group pedicle screw placement can increase the effective length of pedicle screw fixation was about 5.4mm,the increase rate was 10.8%.the average difference was 5.4 + 0.14 mm,compared with the control group,there was significant difference(P < 0.05);(2)the average axial maximum pullout force of the observation group was 1255.3(+ 128.1)N,while the control group was(1010.8 + 120.1)N,the increase rate was 20.7%,the difference between the two groups was statistically significant(P<0.05);(3)compared with the control group,the lateral flexion stiffness values of 5 physiological activities of the observation group specimens were significantly different in axial compression,flexion,posterior extension,decompression side lateriflexion and decompression side contralateral flexion(P < 0.05),the value of the stiffness changes were respectively(115.1 +.)N/mm,(126.1 +.)N/mm,(45.1 +.30.9)N/mm,(+ + 10.6)N/mm and(+ 45.2 +.)N/mm,the increase rates were 44.2%,38.3%,27.5%,30.4%,29.3% respectively.Conclusion: the method of the endplate angle of pedicle screw imbedding provid a new access channel,ensure the mechanical stability,also can increase the effective fixed length and the pullout force,improve pedicle screw fixation in flexion,lateral flexion,axial direction stiffness values obviously,furthermore,the ability of bearing the spine is improved.It is helpful to the initial stability of the recovery period,and it can improve the success probability of the screw placement.