title: Distribution of in vivo and in vitro range of motion following 1-level arthroplasty with the CHARITE artificial disc compared with fusion.
abstract: OBJECTIVE
  One of the goals of lumbar arthroplasty is to restore and maintain range of motion (ROM) and to protect adjacent levels from abnormal motion, which may be a factor in transition syndrome following arthrodesis. In this study, in vitro ROM results were compared with in vivo, 2-year postoperative radiographic ROM evaluations.
  
  
  METHODS
  Radiographs of patients enrolled in the CHARITE investigational device exemption study were analyzed at baseline and at 2 years postoperatively. The ROM in flexion/extension at the implanted and adjacent levels was measured, normalized, and compared with ROM results obtained using cadaver (in vitro) evaluations.
  
  
  RESULTS
  Preoperative ROM distributions in patients enrolled for arthroplasty or fusion at the L4-5 level was as follows: 28% motion was observed at L3-4, 35% at L4-5 and 37% at L5-S1. Following a one-level arthroplasty at L4-5, the in vivo ROM distribution from L-3 to S-1 at the 2-year time point was 36% at L3-4, 30% at L4-5 and 35% at L5-S1. Following a one-level fusion with BAK and pedicle screws at L4-5, the in vivo ROM distribution from L-3 to S-1 at the 2-year time point was 45% at L3-4, 9% at L4-5 and 46% at L5-S1.
  
  
  CONCLUSIONS
  The baseline as well as the 2-year in vivo data confirmed previously published in vitro data. One-level arthroplasty was shown herein to replicate the normal distribution of motion of the intact spine.
authors.affiliation: Spine and Scoliosis Center, St. Joseph's Hospital, Baltimore, Maryland, USA.
authors.forename: Bryan W
authors.initials: BW
authors.lastname: Cunningham
authors.forename: Paul C
authors.initials: PC
authors.lastname: McAfee
authors.forename: Fred H
authors.initials: FH
authors.lastname: Geisler
authors.forename: Gwen
authors.initials: G
authors.lastname: Holsapple
authors.forename: Karen
authors.initials: K
authors.lastname: Adams
authors.forename: Scott L
authors.initials: SL
authors.lastname: Blumenthal
authors.forename: Richard D
authors.initials: RD
authors.lastname: Guyer
authors.forename: Andrew
authors.initials: A
authors.lastname: Cappuccino
authors.forename: John J
authors.initials: JJ
authors.lastname: Regan
authors.forename: Ira L
authors.initials: IL
authors.lastname: Fedder
authors.forename: P Justin
authors.initials: PJ
authors.lastname: Tortolani
mesh_terms: D019643:Arthroplasty, Replacement / Q000379:methods*; D001696:Biomechanical Phenomena; D002102:Cadaver; D015331:Cohort Studies; D005500:Follow-Up Studies; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000601:surgery*; D007595:Joint Prosthesis; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D018583:Pliability; D011446:Prospective Studies; D011474:Prosthesis Design; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology*; D013123:Spinal Fusion / Q000379:methods*