The Mechanical Effects Of The Titanium Plate Length On Single ACDF Segment And Adjacent Discs

Objective This study examined the von Mises stress of adjacent intervertebral disc,and fusion segment bone graft,titanium plate and screws using finite-element method to evaluate the biomechanical effect of different length titanium plates on fusion and adjacent intervertebral discs after C5/C6 anterior cervical discectomy and fusion(ACDF).Methods We constructed 10 preoperative finite element models of intact C4–C7 segments based on computed tomography(CT)images of 10 volunteers and validated them in the present study.Based on 10 preoperative models,three C5/C6 ACDF postoperative models using three different length titanium plates were constructed.We used the plateto-endplate distance(PED)to define the length of the cervical anterior titanium plate.They are 0 mm,5 mm,10 mm,respectively.ACDF surgery with three different length titanium plates fixed were simulated based on the 10 preoperative models in software.So the postoperative models were divided into three groups: long plate(PED=0 mm);middle plate(PED=5 mm);and short plate(PED=10 mm).The changes in the von Mises stress of adjacent intervertebral disc,bone graft,titanium plate and screws in different PED groups in flexion,extension,axial rotation,and lateral bending conditions were analyzed.Results The von Mises stress of the intervertebral discs of upper adjacent segment C4/C5 and lower adjacent segment C6/C7 have no significant differences(P>0.05)in three different length plate groups.The von Mises stress of titanium plate have significant differences(P<0.05)in three different length plate groups.Additionally,the von Mises stress of titanium plate increased as the length of plate increased.The Mises stress of bone graft and screws are significantly different(P<0.05)in three different length plate groups.In addition,the Mises stress of bone graft and screws decreased as the length of plate increased(P<0.05).Conclusion The length of titanium plate has no obvious effect on adjacent intervertebral disc stress,but it is an important factor that affecting the stress of bone graft,titanium plate and screw after ACDF.Longer plate does not increase the adjacent intervertebral disc stress.Additionally,longer plate can reduce the stress on screws and bone graft,which may be helpful to prevent cage subsidence,pseudarthrosis and screw failure.However,we do not advocate the use of plates that can invade adjacent segments.