title: The effect of cervical posterior foraminotomy on segmental range of motion in the setting of total disc arthroplasty.
abstract: METHODS
  Human cadaveric biomechanical analysis.
  
  
  OBJECTIVE
  To investigate the effect on cervical spine segmental stability that results from a posterior foraminotomy after cervical disc arthroplasty (CDA).
  
  
  BACKGROUND
  Posterior foraminotomy offers the ability to decompress cervical nerves roots while avoiding the need to extend a previous fusion or revise an arthroplasty to a fusion. However, the safety of a foraminotomy in the setting of CDA is unknown.
  
  
  METHODS
  Segmental nondestructive range of motion (ROM) was analyzed in 9 human cadaveric cervical spine specimens. After intact testing, each specimen was sequentially tested according to the following 4 experimental groups: group 1=C5-C6 CDA, group 2=C5-C6 CDA with unilateral C5-C6 foraminotomy, group 3=C5-C6 CDA with bilateral C5-C6 foraminotomy, and group 4=C5-C6 CDA with C5-C6 and C4-C5 bilateral foraminotomy.
  
  
  RESULTS
  No differences in ROM were found between the intact, CDA, and foraminotomy specimens at C4-C5 or C6-C7. There was a step-wise increase in C5-C6 axial rotation from the intact state (8°) to group 4 (12°), although the difference did not reach statistical significance. At C5-C6, the degree of lateral bending remained relatively constant. Flexion and extension at C5-C6 was significantly higher in the foraminotomy specimens, groups 2 (18.1°), 3 (18.6°), and 4 (18.2°), compared with the intact state, 11.2°. However, no ROM difference was found within foraminotomy groups (2-4) or between the foraminotomy groups and the CDA group (group 1), 15.3°.
  
  
  CONCLUSIONS
  Our results indicate that cervical stability is not significantly decreased by the presence, number, or level of posterior foraminotomies in the setting of CDA. The addition of foraminotomies to specimens with a pre-existing CDA resulted in small and insignificant increases in segmental ROM. Therefore, biomechanically, posterior foraminotomy/foraminotomies may be considered a safe and viable option in the setting of recurrent or adjacent level radiculopathy after cervical disc replacement.
  
  
  METHODS
  N/A.
authors.affiliation: From the Walter Reed National Military Medical Center, Bethesda, MD. Dr. Lehman is now at the Washington University in St. Louis, St. Louis, MO.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Bevevino
authors.forename: Ronald A
authors.initials: RA
authors.lastname: Lehman
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Kang
authors.forename: David E
authors.initials: DE
authors.lastname: Gwinn
authors.forename: Anton E
authors.initials: AE
authors.lastname: Dmitriev
mesh_terms: D000328:Adult; D000368:Aged; D002102:Cadaver; D002574:Cervical Vertebrae / Q000601:surgery*; D005260:Female; D059526:Foraminotomy / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D019736:Prostheses and Implants; D016059:Range of Motion, Articular; D012399:Rotation; D059145:Total Disc Replacement / Q000295:instrumentation / Q000379:methods*