title: Cage deviation in the subaxial cervical spine in relation to implant position in the sagittal plane.
abstract: Subsidence of interbody cages is a frequently observed and relevant complication in anterior cervical discectomy and fusion (ACDF). Only a handful of studies concentrated on the modality of subsidence and its clinical impact. We performed a retrospective analysis of ACDF patients from 2004 to 2010. Numeric analog scale (NAS) score pre-op and post-op, Oswestry Disability Index (ODI) on x-rays, endplate (EP) and cage dimensions, implant position, lordotic/kyphotic subsidence patterns (>5°), and cervical alignment were recorded. Subsidence was defined as height loss >40%. Patients were grouped into single segment (SS), double segment (DS), and plated procedures. We included 214 patients. Prevalence of subsidence was 44.9% overall, 40.9% for SS, and 54.8% for DS. Subsidence presented mostly for dorsal (40.7%) and mid-endplate position (46.3%, p < 0.01); dorsal placement resulted in kyphotic (73.7%) and central placement in balanced implant migration (53.3%, p < 0.01). Larger cages (>65% EP) showed less subsidence (64.6 vs. 35.4%, p < 0.01). There was no impact of subsidence on ODI or alignment. NAS was better for subsided implants in SS (p = 0.06). Cages should be placed at the anterior endplate rim in order to reduce the risk of subsidence. Spacers should be adequately sized for the respective segment measuring at least 65% of the segment dimensions. The cage frame should not rest on the vulnerable central endplate. For multilevel surgery, ventral plating may be beneficial regarding construct stability. The reduction of micro-instability or over-distraction may explain lower NAS for subsided implants.
authors.affiliation: Department of Neurosurgery, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany. c.mende@uke.de.
authors.forename: Klaus Christian
authors.initials: KC
authors.lastname: Mende
authors.affiliation: Department of Neurosurgery, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
authors.forename: Sven Oliver
authors.initials: SO
authors.lastname: Eicker
authors.affiliation: Praxis für Neurochirurgie und Wirbelsäulentherapie, Bertram Blankstr. 8b, 51427, Bergisch Gladbach, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Weber
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002574:Cervical Vertebrae / Q000601:surgery*; D017586:Diskectomy / Q000009:adverse effects*; D005260:Female; D006801:Humans; D016268:Internal Fixators; D055959:Intervertebral Disc Degeneration / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011788:Quality of Life; D011859:Radiography; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000009:adverse effects* / Q000295:instrumentation* / Q000379:methods; D016896:Treatment Outcome; D055815:Young Adult
keywords: ACDF; Cage size; Degenerative disc disease; Outcome; Subsidence