title: Sagittal cervical alignment after cervical disc arthroplasty and anterior cervical discectomy and fusion: results of a prospective, randomized, controlled trial.
abstract: METHODS
  Radiographic results of a multicenter, prospective randomized study comparing 1-level cervical total disc replacement (TDR-C) with anterior cervical discectomy and fusion (ACDF).
  
  
  OBJECTIVE
  To evaluate the effect on device-level lordosis, cranial and caudal adjacent level lordosis, and overall cervical sagittal alignment (C2-C6) after TDR-C or ACDF.
  
  
  BACKGROUND
  Cervical total disc replacement (TDR-C) has emerged as a promising alternative to ACDF in a select group of patients. The maintenance and/or improvement of sagittal balance is essential in preserving functionality after reconstructive spinal procedures. Recent studies have documented changes in spinal alignment after TDR-C, however, no studies have compared these changes to those noted in matched group of patients that have undergone ACDF.
  
  
  METHODS
  Radiographic data were obtained from the randomized group of a multicenter, randomized, prospective, controlled study comparing TDR-C (ProDisc-C, Synthes Spine, West Chester, PA) with ACDF in the treatment of 1-level cervical disc disease. Complete radiographic data were available for 89 TDR-C patients (average age: 42.2 years) and 91 ACDF patients (average age: 41.7 years). Cervical lordosis at the device level, cranial and caudal adjacent levels, and total cervical lordosis (C2-C6) were independently measured before surgery and 2 years after surgery using custom image stabilization software (Quantitative Motion Analysis, Medical Metrics, Inc, Houston, TX).
  
  
  RESULTS
  C5-C6 was the most common operative level (TDR-C: 54%; ACDF: 55%). At 2 years after surgery, the TDR-C group experienced statistically significant changes in lordosis of 3.0 degrees (P < 0.001), 0.90 degrees (P = 0.006), and -1.9 degrees (P < 0.001) at the operative, cranial, and caudal adj-acent levels, respectively. ACDF experienced changes in lordosis of 4.2 degrees (P < 0.001), 1.0 degrees (P = 0.001), and -1.5 degrees (P = 0.001), respectively. The between-group differences were significant at the operative level (P = 0.03) and the caudal adjacent level (P = 0.05). Total cervical lordosis increased in both TDR-C and ACDF by 3.1 degrees and 3.8 degrees , respectively (P = 0.49).
  
  
  CONCLUSIONS
  In both TDR-C and ACDF, lordosis increased at the device-level, cranial adjacent level, and in total cervical lordosis, while lordosis decreased at the caudal adjacent level. Although ACDF facilitated a greater increase in device level lordosis (+1.25 degrees ) and less loss of lordosis at the caudal adjacent level compared with TDR-C (-0.39 degrees ), the clinical relevance of the small differences remain unknown.
authors.affiliation: Department of Orthopaedic Surgery, The University of Pennsylvania, Philadelphia, USA.
authors.forename: Okechukwu A
authors.initials: OA
authors.lastname: Anakwenze
authors.forename: Joshua D
authors.initials: JD
authors.lastname: Auerbach
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Milby
authors.forename: Baron S
authors.initials: BS
authors.lastname: Lonner
authors.forename: Richard A
authors.initials: RA
authors.lastname: Balderston
mesh_terms: D000328:Adult; D019643:Arthroplasty, Replacement / Q000295:instrumentation; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D017586:Diskectomy; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D007595:Joint Prosthesis; D008141:Lordosis / Q000209:etiology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011857:Radiographic Image Interpretation, Computer-Assisted; D016059:Range of Motion, Articular; D013122:Spinal Diseases / Q000150:complications / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D013123:Spinal Fusion; D013997:Time Factors; D016896:Treatment Outcome; D014481:United States