3. Fatigue analysis of multilevel anterior cervical fusion with stand-alone anchored spacer vs interbody cage with anterior plate

Abstract

BACKGROUND CONTEXT Anterior cervical discectomy and fusion (ACDF) is the surgical standard for treating anterior based cervical spine pathology with interbody spacers and plating most common. Complications are more prevalent in multilevel cases. Stand-alone anchored spacers were designed to resolve these issues. For 1-level ACDF they provide similar clinical results, fewer implant related complications and decreased compensatory motion at adjacent levels. Reporting on fatigue analysis of multilevel plating vs anchored spacers is limited. PURPOSE Perform fatigue analysis and compare spinal stability of 3-level cervical ACDF constructs using either anchored spacers or standard cages with anterior plating. STUDY DESIGN/SETTING In-vitro biomechanical study. OUTCOME MEASURES Range of motion (ROM) of index levels, adjacent segments, and overall construct. METHODS Spinal stability testing was performed on cadaveric cervical spines (C2-T2) in sagittal, coronal and transverse planes. Specimens tested intact and assigned to either anchored spacer or anterior plate group. Each had a 3-level discectomy (C4/5, C5/6, and C6/7), followed by assigned instrumentation. Specimens retested followed by a fatigue protocol of 5k cycles of flexion/extension and then 5k cycles of axial rotation. Spinal stability testing was performed following each 5k cycles of fatigue. ROM was measured from the index levels, adjacent segments, and overall construct. Peak directional ROMs were compared between groups and analyzed with ANOVA and post hoc t-tests. RESULTS There were similar and significant (p CONCLUSIONS For 3-level ACDF, there was a significant increase in ROM in the index levels using anchored spacers with no significant change in adjacent segment ROM when compared to standard cages and anterior plate. After fatigue, an increase in index ROM and adjacent segment ROM was seen with the anchored spacer compared to anterior plating. Future studies are needed to determine if differences in motion have any clinical significance regarding fusion in 3-level ACDF. FDA DEVICE/DRUG STATUS Stand-alone anchored spacer (Approved for this indication), interbody cage with anterior place (Approved for this indication)