ABSTRACT
BACKGROUND:The angle of screw placement in anterior cervical discectomy and fusion plays a crucial role in determining the stability of the internal fixation system. OBJECTIVE:To predict the impact of different screw placement angles on the stress experienced by the internal fixation system in anterior cervical discectomy and fusion utilizing finite element analysis,with the ultimate goal of identifying the optimal screw placement angle. METHODS:A three-dimensional reconstruction method was employed to establish a mechanical model of the cervical spine,enabling the simulation of three distinct working conditions:scoliosis,uprightness,and forward flexion.In SolidWorks 2017,the anterior cervical plate and screw models were built according to different placement angles of the screws,with a as the inward offset,b as the ideal position,c as the outward offset,d as the downward offset,and e as the upward offset.The stress distribution of internal fixation system at different screw placement angles was observed,and the stress and displacement were recorded. RESULTS AND CONCLUSION:(1)By constructing a finite element model of the entire cervical spine and incorporating an anterior titanium plate,it was found that the biomechanical changes in the spine did not significantly differ based on the various angles of screw insertion on the titanium plate under the same working conditions.(2)However,microscopic analysis revealed that the outward offset(c)screw position exhibited the most effective resistance against side bending,while the downward offset(d)screw demonstrated optimal load-bearing capacity in the upright condition.Additionally,the outward deviation(c)screw displayed superior anti-bending effects in the reverse buckling condition.(3)The fixation effect of the internal fixation device remained relatively stable across different motion conditions.Although there was a 10％variation in the internal fixation effect under the three working conditions when the screw was placed inward,outward,downward,or upward,the displacement changes were minimal.These findings suggest that the requirements of load bearing,bending resistance,and flexion resistance could be simultaneously met without a specific optimal screw location in clinical practice.(4)The placement direction of titanium plate screw in anterior cervical disc-resection and fusion has little effect on the mechanical stability of the cervical spine.The screw angles in different directions have little influence on the stability of the internal fixation device in the lateral,upright,and forward flexion movements of the cervical spine.There is no need to pursue the direction of screw placement in clinical operations.