title: Adjacent segment degeneration and disease following cervical arthroplasty: a systematic review and meta-analysis.
abstract: BACKGROUND
  Cervical arthroplasty is an increasingly popular alternative for the treatment of cervical radiculopathy and myelopathy. This technique preserves motion at the index and adjacent disc levels, avoiding the restraints of fusion and potentially minimizing adjacent segment pathology onset during the postoperative period.
  
  
  OBJECTIVE
  This study aimed to identify all prospective studies reporting adjacent segment pathology rates for cervical arthroplasty.
  
  
  METHODS
  Systematic review and meta-analysis were carried out.
  
  
  METHODS
  Studies reporting adjacent segment degeneration (ASDegeneration) and adjacent segment disease (ASDisease) rates in patients who underwent cervical arthroplasty comprised the patient sample.
  
  
  METHODS
  Outcomes of interest included reported ASDegeneration and ASDisease events after cervical arthroplasty.
  
  
  METHODS
  We conducted a MEDLINE, SCOPUS, and Web of Science search for studies reporting ASDegeneration or ASDisease following cervical arthroplasty. A meta-analysis was performed to calculate effect summary values, 95% confidence intervals (CIs), Q values, and I(2) values. Forest plots were constructed for each analysis group.
  
  
  RESULTS
  Of the 1,891 retrieved articles, 32 met inclusion criteria. The patient incidence of ASDegeneration and ASDisease was 8.3% (95% CI 3.8%-12.7%) and 0.9% (95% CI 0.1%-1.7%), respectively. The rate of ASDegeneration and ASDisease at individual levels was 10.5% (95% CI 6.1%-14.9%) and 0.2% (95% CI -0.1% to 0.5%), respectively. Studies following patients for 12-24 months reported a 5.1% (95% CI 2.1%-8.1%) incidence of ASDegeneration and 0.2% (95% CI 0.1%-0.2%) incidence of ASDisease. Conversely, studies following patients for greater than 24 months reported a 16.6% (5.8%-27.4%) incidence of ASDegeneration and 2.6% (95% CI 1.0%-4.2%) of ASDisease. This identified a statistically significant increase in ASDisease diagnosis with lengthier follow-up. Additionally, 1- and 2-level procedures resulted in a 7.4% (95% CI 3.3%-11.4%) and15.6% (95 CI-9.2% to 40.4%) incidence of ASDegeneration, respectively. Although there was an 8.2% increase in ASDegeneration following 2-level operations (relative to 1-level), it did not reach statistical significance. We were unable to analyze ASDisease incidence following 2-level arthroplasty (too few cases), but 1-level operations resulted in an ASDisease incidence of 0.8% (95% CI 0.1%-1.5%).
  
  
  CONCLUSIONS
  This review represents a comprehensive estimation of the actual incidence of ASDegeneration and ASDisease across a heterogeneous group of surgeons, patients, and arthroplasty techniques. Our investigation should serve as a framework for individual surgeons to understand the impact of various cervical arthroplasty techniques, follow-up duration, and surgical levels on the incidence of ASDegeneration and ASDisease during the postoperative period.
authors.affiliation: School of Medicine, Case Western Reserve University, 2109 Adelbert Rd., Cleveland, OH 44106, USA. Electronic address: mfs82@case.edu.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Shriver
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University, 1800 Orleans St., Baltimore, MD 21287, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Lubelski
authors.affiliation: School of Medicine, Case Western Reserve University, 2109 Adelbert Rd., Cleveland, OH 44106, USA.
authors.forename: Akshay M
authors.initials: AM
authors.lastname: Sharma
authors.affiliation: Department of Neurosurgery, Neurological Institute, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, USA; Center for Spine Health, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Steinmetz
authors.affiliation: Department of Neurosurgery, Neurological Institute, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, USA; Center for Spine Health, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, USA.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Benzel
authors.affiliation: Center for Spine Health, Cleveland Clinic, 9500 Euclid Ave., Cleveland, OH 44195, USA; Department of Orthopaedic Surgery, 9500 Euclid Ave., Cleveland Clinic, Cleveland, OH 44195, USA.
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Mroz
mesh_terms: D001178:Arthroplasty / Q000009:adverse effects* / Q000379:methods; D002574:Cervical Vertebrae / Q000601:surgery*; D017586:Diskectomy / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000209:etiology*; D008297:Male; D013123:Spinal Fusion / Q000009:adverse effects* / Q000379:methods
keywords: Adjacent segment degeneration; Adjacent segment disease; Artificial disc replacement; Cervical arthroplasty; Meta-analysis; Systematic review