Relationship Between The Accuracy Of Screw And Parameters Of Pedicle In The Treatment Of Thoracic And Lumbar Fracture By Percutaneous Pedicle Screw Fixation

Objective To investigate the relationship between the screw accuracy and the outer pedicle width(OPW),transverse pedicle angle(TPA)of pedicle,cohesion of facet joint on cross-section CT in patients who underwent percutaneous pedicle screw fixation for treatment of thoracic and lumbar fractures.Methods This study retrospectively analyzed 63 patients for the treatment of thoracic and lumbar fractures in a single institution from 2015.08-2019.4.Computed tomography(CT)was performed postoperatively and screw position within the pedicle was assessed.Also,the diameter,angle of pedicle and cohesion of facet joint were measured.Results A total of 380 screws were inserted and 39(10.26%)penetrated pedicle cortex.Thoracic pedicle screws had a lower misplacement rate than lumbar(6.73% vs.11.59%,P>0.05),whereas there is no significant difference.31 screws were penetrated through the lateral wall while 8 were penetrated through the medial wall(P < 0.05).The OPW of the grade 0 group was 8.19±1.31 mm,which was 6.70±1.81 mm of the penetrated group(grade 1,2 and 3)(P< 0.05).The TPA was 8.74±1.37° in the grade 0 group and 9.26±1.73° in the lateral penetrated group(P< 0.05).The ratio of the superior inter facet width(IFW)process to the spinal canal width(SCW)was used to represent cohesion of facet joint,and showed significant difference between grade 0 and lateral penetrated groups(1.85±0.16 vs.1.96±0.18,P<0.05).Also,medial penetrated group has smaller ratio than lateral penetrated group(1.74±0.14 vs.1.96±0.18,P<0.05).Conclusion Percutaneous pedicle screw fixation for the treatment of thoracic and lumbar fractures is consistent with the rate of screw misplacement reported in the literature.The accuracy of screw was related to TPA,OPW and cohesion of facet joint.