Surgical outcomes after posterior lumbar interbody fusion using traditional trajectory screw fixation or cortical bone trajectory screw fixation: A comparative study between the polyetheretherketone cage and the same shape titanium-coated polyetheretherketone cage

Abstract

ObjectiveTo investigate whether or not the fusion rate after posterior lumbar interbody fusion with cortical bone trajectory screw fixation (CBT-PLIF) is lower than after PLIF using traditional trajectory screw fixation (TT-PLIF) and whether or not the titanium-coated polyetheretherketone (PEEK) cage (TiP cage) improves fusion status compared to the same shape uncoated PEEK cage (P cage). MethodsThe subjects were 37 patients undergoing TT-PLIF using P cages (P-TT group), 24 patients undergoing CBT-PLIF using P cages (P-CBT group), 32 patients undergoing TT-PLIF using TiP cages (TiP-TT group), and 20 patients undergoing CBT-PLIF using TiP cages (TiP-CBT group). All patients from the 4 groups underwent our unified PLIF procedure (total facetectomy, subtotal discectomy, and the same bone graft technique using the same shape cages) except for the screw trajectories and the surface materials of the cages. Clinical symptoms were assessed using the Japanese Orthopedic Association (JOA) score before surgery and at 2-year postoperatively. None of age at the time of surgery, gender, fused segment and preoperative JOA score showed significant differences among the 4 groups. On multiplanar reconstruction computed tomography (MPR-CT) at 6months after surgery, vertebral end plate cysts were evaluated and classified into local or diffuse cysts. Fusion status was assessed using both dynamic plain radiographs and MPR-CT at postoperative 2-year. ResultsNeither the mean JOA score nor the mean recovery rate of the JOA score at 2-year after surgery showed significant differences among the 4 groups. The incidence of the diffuse cyst (a known predictor of non-union) was 27.0% in the P-TT group, 29.2% in the P-CBT group, 25.0% in the TiP-TT group and 25.0% in the TiP-CBT group (P > 0.05). The fusion rate was 89.2% in the P-TT group, 91.7% in the P-CBT group, 90.6% in the TiP-TT group and 90.0% in the TiP-CBT group (P > 0.05). ConclusionsAfter our unified PLIF procedure except for the screw trajectories and the surface materials of the cages, CBT-PLIF resulted in the equivalent fusion rate to TT-PLIF and the TiP cage did not lead to the improved fusion rate compared to the same shape P cage.