P105. The influence of standalone cage versus plate-augmented single-level ACDF on global and local cervical sagittal alignment

Abstract

BACKGROUND CONTEXT Prior studies have demonstrated that the postoperative sagittal alignment parameters of the cervical spine influence clinical outcomes and patient-reported outcome scores. For example, increased C2-C7 sagittal vertical axis (SVA) has been shown to decease neck disability index (NDI) scores. One recent study characterized the influence that different implant choices (particularly standalone versus plate-augmented constructs) had on cervical alignment parameters for 2-level ACDFs, and found that plate-augmented devices were better at restoring cervical lordosis. PURPOSE There is a paucity of literature investigating sagittal alignment parameters for single level constructs, and thus we sought to compare the ACDF-plate and ACDF-cage constructs in terms of their influence on sagittal parameters for single level fusions. STUDY DESIGN/SETTING This is a retrospective cohort study comparing patients who underwent ACDF with a plate-augmented construct to those who underwent ACDF with a standalone interbody device. PATIENT SAMPLE We identified 43 patients who underwent ACDF during the period studied. Of those, 17 underwent ACDF with a standalone device, whereas 26 underwent plate-augmented ACDF. OUTCOME MEASURES Demographic and perioperative factors were collected. Radiographic parameters of C2-C7 SVA, C2-C7 lordosis, segmental cobb angle, T1 slope, and T1 slope minus C2-C7 lordosis were measured on preoperative and postoperative images. METHODS We retrospectively analyzed the preoperative and most recent postoperative radiographs from patients who underwent a single-level ACDF for degenerative cervical spondylosis at our institution between May 2014 and July 2019. The average follow-up time was 10.5 months. Patients were separated into groups based on the construct used (ACDF-cage and ACDF-plate). Demographic and perioperative factors were collected. Radiographic parameters of C2-C7 SVA, C2-C7 lordosis, segmental cobb angle, T1 slope, and T1 slope minus C2-C7 lordosis were measured on preoperative and postoperative images. Patient demographic, perioperative and radiographic factors were compared using Pearson's chi-square test for categorical and independent samples t-test for continuous variables. RESULTS We identified 43 patients who underwent ACDF during the period studied. Of those, 17 underwent ACDF with a standalone device, whereas 26 underwent plate-augmented ACDF. There was no significant difference between groups in terms of age (52.0 vs 48.8, p = >0.05) or which levels were fused (p = 0.615). We did not find a significant difference between groups in the final postoperative sagittal alignment parameters (SVA 28.6 vs 33.7, cervical lordosis 10.2 vs 12.4, segmental angle 4.9 vs 4.3, T1 slope 25.8 vs 27.7, T1 slope minus cervical lordosis 0.83 vs 4.03, p>0.05). We also compared the change from preoperative to postoperative alignment between groups, and again found no significant difference when comparing ACDF-plate to ACDF-cage constructs. CONCLUSIONS Our data has failed to demonstrate a difference in radiologic alignment outcomes between plate-augmented and standalone single-level ACDF constructs. This is not consistent with a prior study comparing these constructs in patients with 2-level ACDFs, which found better postoperative cervical alignment with the use of an ACDF with an anterior plate. However, a recent meta-analysis comparing single-level ACDF-plate to ACDF-cage constructs also found no difference between groups in terms of C2-C7 lordosis or segmental cobb angle, but that study did not examine other parameters such as C2-C7 SVA. Thus, our data, taken in tandem with the existing literature, seem to support the conclusion that the effects of construct on cervical alignment are significant for fusions of at least two levels, but may not reach significance for single level fusions. However, the power of our study to detect small but significant differences between groups is limited due to the number of cases analyzed, and thus further study is still needed to make definitive conclusions regarding ACDF construct choice. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.