Cervical arthroplasty: a critical review of the literature.
BACKGROUND
Cervical disc arthroplasty (CDA) is a motion-preserving procedure that is an alternative to fusion. Proponents of arthroplasty assert that it will maintain cervical motion and prevent or reduce adjacent segment degeneration. Accordingly, CDA, compared with fusion, would have the potential to improve clinical outcomes. Published studies have varying conclusions on whether CDA reduces complications and/or improves outcomes. As many of these previous studies have been funded by CDA manufacturers, we wanted to ascertain whether there was a greater likelihood for these studies to report positive results.


OBJECTIVE
To critically assess the available literature on cervical arthroplasty with a focus on the time of publication and conflict of interest (COI).


METHODS
Review of the literature.


METHODS
All clinical articles about CDA published in English through August 1, 2013 were identified on Medline. Any article that presented CDA clinical results was included. Study design, sample size, type of disc, length of follow-up, use of statistical analysis, quality-of-life (QOL) outcome scores, COI, and complications were recorded. A meta-analysis was conducted stratifying studies by COI and publication date to identify differences in complication rates reported.


RESULTS
Seventy-four studies were included that investigated 8 types of disc prosthesis and 22 met the criteria for a randomized controlled trial (RCT). All Level Ib RCTs reported superior quality-of-life outcomes for CDA versus anterior cervical discectomy and fusion (ACDF) at 24 months. Fifty of the 74 articles (68%) had a disclosure section, including all Level Ib RCTs, which had significant COIs related to the respective studies. Those studies without a COI reported mean weighted average adjacent segment disease rates of 6.3% with CDA and 6.2% with ACDF. In contrast, the reverse was reported by studies with a COI, for which the averages were 2.5% with CDA and 6.3% with ACDF. Those studies with a COI (n=31) had an overall weighted average heterotopic ossification rate of 22%, whereas those studies with no COI (n=43) had a rate of 46%.


CONCLUSIONS
Associated COIs did not influence QOL outcomes. Conflicts of interest were more likely to be present in studies published after 2008, and those with a COI reported greater adjacent segment disease rates for ACDF than CDA. In addition, heterotopic ossification rates were much lower in studies with COI versus those without COI. Thus, COIs did not affect QOL outcomes but were associated with lower complication rates.
Neurological Institute, Center for Spine Health, Department of Orthopaedic and Neurological Surgery, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA; Case Western Reserve University School of Medicine, 10900 Euclid Ave, Cleveland, OH 44106, USA.
Matthew D
MD
Alvin
Neurological Institute, Center for Spine Health, Department of Orthopaedic and Neurological Surgery, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA; Department of Neurological Surgery, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA.
E Emily
EE
Abbott
Neurological Institute, Center for Spine Health, Department of Orthopaedic and Neurological Surgery, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA; Cleveland Clinic Lerner College of Medicine, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA.
Daniel
D
Lubelski
Neurological Institute, Center for Spine Health, Department of Orthopaedic and Neurological Surgery, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA; Case Western Reserve University School of Medicine, 10900 Euclid Ave, Cleveland, OH 44106, USA.
Benjamin
B
Kuhns
Cleveland Clinic Lerner College of Medicine, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA; Department of Quantitative Health Sciences, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA.
Amy S
AS
Nowacki
Neurological Institute, Center for Spine Health, Department of Orthopaedic and Neurological Surgery, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA; Department of Neurosciences, MetroHealth Medical Center, 2500 Metrohealth Dr., Cleveland, OH 44109, USA.
Michael P
MP
Steinmetz
Neurological Institute, Center for Spine Health, Department of Orthopaedic and Neurological Surgery, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA; Department of Neurological Surgery, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA; Cleveland Clinic Lerner College of Medicine, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA.
Edward C
EC
Benzel
Neurological Institute, Center for Spine Health, Department of Orthopaedic and Neurological Surgery, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA; Department of Neurological Surgery, Cleveland Clinic, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA; Cleveland Clinic Lerner College of Medicine, 9500 Euclid Ave., S-80, Cleveland, OH 44195, USA. Electronic address: mrozt@ccf.org.
Thomas E
TE
Mroz
D000368:Aged; D001178:Arthroplasty / Q000009:adverse effects / Q000379:methods*; D002574:Cervical Vertebrae / Q000601:surgery*; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery*; D055959:Intervertebral Disc Degeneration / Q000601:surgery*; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000009:adverse effects / Q000379:methods; D016896:Treatment Outcome
Adjacent segment disease; Arthroplasty; Cervical disc arthroplasty; Fusion; Heterotopic ossification; Outcomes