Interbody Cage Placement Without Plate Supplementation Adjacent to Plated Segments in Multilevel Anterior Cervical Decompression and Fusion

Abstract

Study Design. A retrospective cohort study. Objective. To evaluate the clinical efficacy and safety of hybrid anterior cervical fixation, focusing on stand-alone segments. Summary of Background Data. In the treatment of multilevel cervical stenosis, the number of segments fixed using a plate is limited by placing an interbody cage without plate supplementation at one end of the surgical segment to reduce long plate-related problems. However, the stand-alone segment may experience cage extrusion, subsidence, cervical alignment deterioration, and nonunion. Methods. Patients who underwent three-segment or four-segment fixation for cervical degenerative disease and completed one-year follow-up were included in this study. Patients were divided into two groups: a cranial group, with stand-alone segments located at the cranial end adjacent to plated segments, and a caudal group, with stand-alone segments located at the caudal end. Differences in radiographic outcomes between the groups were evaluated. Fusion was defined using dynamic radiographs or computed tomography. To identify factors associated with nonunion in stand-alone segments, multivariable logistic regression analyses were performed. To identify factors associated with cage subsidence, multiple regression analyses were performed. Results. A total of 116 patients (mean age, 59±11 y; 72% male; mean fixed segments, 3.7±0.5 segments) were included in this study. No case showed cage extrusion or plate dislodgement. In stand-alone segments, the fusion rate was significantly lower in the caudal group than in the cranial group (76% vs. 93%, P=0.019). Change in the cervical sagittal vertical axis was worse in the caudal group than in the cranial group (2.7±12.3 mm vs. −2.7±8.1 mm, P=0.006). One caudal group patient required additional surgery because of nonunion at the stand-alone segment. Multivariable logistic regression indicated factors associated with nonunion included the location of the stand-alone segment (caudal end: OR 4.67, 95% CI, 1.29–16.90), larger pre-disk space range of motion (OR 1.15, 95% CI, 1.04–1.27), and lower preoperative disk space height (OR 0.57, 95% CI, 0.37–0.87). Multiple regression analysis indicated that higher cage height and lower pre-disk space height were associated with cage subsidence. Conclusion. Hybrid anterior cervical fixation with stand-alone interbody cage placement adjacent to plated segments may avoid long plate-related problems. Our results suggest that the cranial end of the construct may be more suitable for the stand-alone segment than the caudal end.