The Biomechanic Analysis Of Instrumentation Growing Rods Of Sliding Pedicle Screw System

ObjectiveComparing the biomechanics in growing rod techniques of sliding pedicle screwsystem and the universal spine system(USS)to improve this system and provide theclinical theoretical basis in the future.MethodThis first part of this paper twelve fresh porcine thoracic spines containing6fnctional spinal unit (FSU) were divided into2groups randomly, sliding pediclescrew system group (normal attachment screws in the3rd,4th vertebra and slidingpedicle screws in1st,6th vertebra),universal spine system group (normal attachmentscrews in the1st,3rd,4th,6th vertebra).One implanted with the growing rodtechniques of sliding pedicle screw system and the other with USS.The range ofmotion of one to three vertebral flexion/extension,left/right lateral bending andleft/right axial rotations were tested.All the statistics were analyzed by SPSS18.0. Thesecond part using twelve fresh porcine thoracic spines containing3FSU to divide into2groups randomly, sliding pedicle screw system group (normal attachment screws inthe3rd vertebra and sliding pedicle screws in1st vertebra),universal spine systemgroup (normal attachment screws in the1st,3rd vertebra).One implanted with thegrowing rod techniques of sliding pedicle screw system and the other with USS.Thelimit load of vertebral flexion state and axial rotations state were tested. All thestatistics were analyzed by SPSS18.0.ResultThere is no significant change in the ROM after fixation both with the growingrod techniques of sliding pedicle screw system and the universal spine system.(pï¹¥0.05)The screw loosening occurs on flexion state at400N in sliding pedicle screw system group,while at1800N in universal spine system group.(p<0.05)The screw loosening occurs on axial rotations state at5degrees in sliding pediclescrew system group,while at10degrees in universal spine system group.(p<0.05)ConclusionThe growing rod techniques of sliding pedicle screw system can achieve thesame orthopedic effect and biomechanical stability.The limit loading of the sliding pedicle screw system is smaller than that ofUSS.It demonstrated that the sliding pedicle screw system has some deficiencieswhich needed to be further optimized in order to increase the strength of the fixation.