Impact of subsidence on clinical outcomes and radiographic fusion rates in anterior cervical discectomy and fusion: a systematic review.
METHODS
Systematic review.


OBJECTIVE
To provide a systematic review of published literature on the impact of subsidence on clinical outcomes and radiographic fusion rates after anterior cervical discectomy and fusion with plates or without plates.


BACKGROUND
Subsidence of interbody implants is common after anterior cervical spine fusions. The impact of subsidence on fusion rates and clinical outcomes is unknown.


METHODS
Systematic literature review on published articles on anterior cervical discectomy and fusion, which objectively measured graft subsidence, radiographic fusion rates, and clinical outcomes between April 1966 and December 2010.


RESULTS
A total of 35 articles that measured subsidence and provided fusion rates and/or clinical outcomes were selected for inclusion. The mean subsidence rate ranged from 19.3% to 42.5%. The rate of subsidence based on the type of implant ranged from 22.8% to 35.9%. The incidence of subsidence was not impacted by the type of implant (P=0.98). The overall fusion rate of the combined studies was 92.8% and was not impacted by subsidence irrespective of subsidence definition or the measurement technique used (P=0.19). Clinical outcomes were evaluated in 27 of 35 studies with all studies reporting an improvement in patient outcomes postoperatively.


CONCLUSIONS
Subsidence irrespective of the measurement technique or definition does not appear to have an impact on successful fusion and/or clinical outcomes. A validated definition and standard measurement technique for subsidence is needed to determine the actual incidence of subsidence and its impact on radiographic and clinical outcomes.
Division of Neurosurgery, Duke University Medical Center, Durham, NC.
Isaac O
IO
Karikari
Deeptee
D
Jain
Timothy Ryan
TR
Owens
Oren
O
Gottfried
Tiffany R
TR
Hodges
Shahid M
SM
Nimjee
Carlos A
CA
Bagley
D001696:Biomechanical Phenomena; D001860:Bone Plates; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery*; D003710:Demography; D017586:Diskectomy / Q000379:methods*; D006801:Humans; D011859:Radiography; D013123:Spinal Fusion / Q000379:methods*; D016896:Treatment Outcome