Zero-Profile Stand-Alone Cages versus Cage-and-Plate in Single and Multi-level Anterior Cervical Discectomy and Fusion: a Propensity-Matched Analysis Using Validated Fusion Assessment Methods
Research Fellow Hospital for Special Surgery Hospital for Special Surgery
Introduction: Zero-profile stand-alone (SA) constructs and cage-and-plate (ACP) are popular approaches to anterior cervical discectomy and fusion (ACDF). However, differences in fusion rates are unclear, and existing studies lack patient-reported outcomes (PROMs) and propensity-matching. Also, fusion assessment methods differ between studies, with varying sensitivity, specificity, and agreement between assessors. We compare fusion rates between propensity-matched SA versus ACP using a method validated by intraoperative motion testing during revision surgery. We also compare sagittal alignment, perioperative outcomes, and PROMs. We hypothesize that SA and ACP will have similar fusion rates for single-level, but ACP will have higher fusion rates in multi-level ACDF. Sagittal alignment, perioperative outcomes, and patient-reported outcomes (PROMs) will be comparable between ACP and SA.
Methods: Patients 18 > years who underwent primary ACDF were included. Two-to-one propensity score matching for age, sex, body mass index, Charlson comorbidity index, and number of surgical levels was used. Fusion was assessed at 1 year. Patients were fused if they 1) had less than 1mm of interspinous motion per fused level between flexion and extension radiographs, or 2) had 3 slices showing bridging bone on computed tomography.
Results: There were 153 patients (51 SA; 102 ACP) after matching, with no differences in 1-year fusion rates overall or by number of surgical levels. There were no differences in adjacent level ossification (ALOD) rates or ALOD grade. Segmental lordosis, overall cervical lordosis, T1 slope, T1 slope minus lordosis (TS-CL), and PROMs (Neck Disability Index, 12-Item short form survey physical component, visual analog scale for neck and arm pain) were not different at any time point up through postoperative 2-years. Operative time and blood loss were greater with ACP (p = 0.001), with no differences in complications or dysphagia.
Conclusion : This study is the first to compare fusion rates of single and multi-level SA versus ACP with comparison of PROMs and sagittal alignment, using a validated fusion assessment method. Fusion rates, PROMs, radiographic outcomes, complications, and rate of dysphagia were all comparable after single and multi-level ACDF regardless of SA or ACP. These findings may allow surgeons more flexibility in implant and technique selection based on individual patient characteristics.