50. Sagittal parameters poorly predict clinical outcomes following anterior cervical discectomy and fusion

Abstract

BACKGROUND CONTEXT While attention to sagittal parameters in the cervical spine is increasing, the relationship between these radiographic measurements and clinical outcomes is less clear. PURPOSE The aim of the present study was to characterize independent associations between cervical spine radiographic parameters and clinical outcomes following anterior cervical discectomy and fusion (ACDF). STUDY DESIGN/SETTING Retrospective cohort analysis. PATIENT SAMPLE Analysis of consecutive patients who underwent a single-level ACDF at an academic institution between 2008 and 2015 for cervical radiculopathy and/or myelopathy, with a minimum of 6 months of clinical and radiographic follow-up. OUTCOME MEASURES Disc height was measured as the anterior vertebral distance (AVD), mid-vertebral distance (MVD), and posterior vertebral distance (PVD) on preoperative and immediate postoperative radiographs. Sagittal parameters were also measured, and included C2-C7 lordosis, T1 angle, fusion segment lordosis, sagittal vertical axis (SVA), proximal and distal adjacent segment lordosis. Preoperative and final visual analog scale (VAS) neck, VAS arm, and Neck Disability Index (NDI) scores were collected. The rates of reoperation, successful fusion, and subsidence (postoperative disc space collapse >2 mm) were determined. METHODS Preoperative, postoperative, and final radiographs were reviewed. Radiographic parameters were tested for association with patient-reported outcomes, reoperation, fusion, and subsidence using multivariate linear regression and multivariate logistic regression for continuous and binary outcomes, respectively. Multivariate regressions controlled for potential confounding variables in order to identify independent risk factors for each outcome. The Sidak-Holm method was used to adjust p-values in order to correct for multiple statistical comparisons. The threshold for statistical significance was set at p RESULTS A total of 381 patients met inclusion criteria. Average follow-up length was 28 months, average age was 50.2 years, average body mass index was 28.7, and 49.2% of patients were female. Of these patients, 93.7% achieved successful fusion, 6.6% had graft subsidence, and 4.99% had a reoperation. Preoperative and postoperative radiographic measurements and patient-reported outcomes were collected. Preoperative radiographic measurements poorly predicted clinical outcomes. Increased preoperative lordosis at the adjacent unfused segment proximal to the eventual fusion mass was found to be associated with increased final NDI (corrected p=0.018), and increased final proximal lordosis was associated with increased final NDI (corrected p=0.049). However, no other radiographic parameters were associated with any patient-reported clinical outcomes. Subsidence rates were increased with greater change in proximal lordosis from preoperative to postoperative (OR 1.30, corrected p=0.007) and from preoperative to final follow-up (OR 1.17, corrected p=0.044). Subsidence was negatively associated with increased change in lordosis across the fused segments from preoperative to postoperative (OR 0.88, corrected p=0.032) and from preoperative to final follow-up (OR 0.86, corrected p=0.017). CONCLUSIONS The present study found that sagittal parameters were poorly predictive of clinical outcomes. Increased preoperative lordosis at the adjacent segment proximal to the fusion mass was associated with worse final NDI scores, and was the only preoperative radiographic parameter associated with clinical outcomes. Further research should attempt to identify other preoperative factors or radiographic parameters that are more closely associated with clinical outcomes. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.