Biomechanical study of lumbosacral spine fixation with double pedicle crew system by anterolateral approach in one stage / 中华骨科杂志

ABSTRACT

Objective To conduct the biomechanical evaluation of the effect of the new operative method,one stageanterior debridement and fusion combined withtitanium cage and dual screw-rod anterior instrumentation inter-fixation on the reconstruction of lumbosacral spine stability and provide biomechanical support for its further promotion in clinical practice.Methods Fifteen lumbosacral spine specimens were obtained from the department of anatomy,Xi'an Jiaotong University Health Science Center.Fracture,deformity and osteoporosis were removed by CT and bone density examination.The remaining specimens were randomly divided into intact group,anterior fixation group and posterior fixation group.L5 vertebral body and adjacent intervertebraldisc subtotal resection were performed on all specimens in the anterior fixation group and the posterior fixation group.The specimens in the anterior fixation group were fixed through titanium cage and dual screw-rod from front approach and the specimens inthe posterior group were fixed by dual screw-rod from posterior approach.Specimens in the intact group were not treated.All specimens were examined by X-ray and thin-slice CT after surgery to determine whether implant placement was appropriate andwhether there was spinal cord compression or not.Three groups of lumbosacral spine specimens were subjected to mechanical testsunder the conditions of flexion and extension,lateral bending,axial torsion and axial compression to evaluate the mechanical effect of anterior dual screw-rod system combined with titanium cage on the fixation of lumbosacral spine.Results All lumbosacralspine specimens were free of fractures,deformities,osteoporosis and other diseases.Postoperative imaging examination showed thatthe implant was in normal position and no adverse phenomena such as pedicle screw insertion into the spinal canal and spinalcord compression were observed.Mechanical test results in vitro showed that the load required for maximum loading displacement (5 mm) or rotation angle (5°) of the specimens in the intact group was less than that of the specimens in anterior and posterior fixation group in flexion,lateral bending and axial compression and torsion direction (Fflexion=1335.989,Pflexion=0.000;Fextenxion=166.688,Pextenxion=0.000;Fleft latebending=258.872,Pleft lateral bending=0.000;Fright lateral bending=335.766,Pright lateral bending=0.000;Faxial compression=481.444,Paxial compression =0.000;Fleft rotation=21.682,Pleft totation=0.000;Fright rolation=34.990,Pright rotation=0.000).When the maximum loading displacement (5 mm) was reached,the load required for the specimens in anterior fixation group was significantly greater than that for specimens in posterior fixation groupin the direction of flexion,left and right lateral bending and axial compression (Pflexion=0.000;Pleft lateral bending=0.006;Pright lateral bending=0.016;Paxial compression=0.000).However,the load required to reach the maximum loading displacement (5 mm) in the anterior fixation group in the direction of extension was significantly lower than that in the posterior fixation group (P=0.000).When the maximum load angle (5°) was reached intorsion direction,the required load of the specimens in both anterior and posterior fixation groups was similar (Pleft rotation=0.820;Pright rotation=0.259).Conclusion The anterior fixation of lumbosacral spine specimens with titanium cage combined with dualscrew rod can provide better immediate stability and its stability in flexion,lateral bending and axial compression is better than that of back double nailing rodfixed.