title: Effect of prosthesis endplate lordosis angles on L5-S1 kinematics after disc arthroplasty.
abstract: OBJECTIVE
  We hypothesized that L5-S1 kinematics will not be affected by the lordosis distribution between the prosthesis endplates.
  
  
  METHODS
  Twelve cadaveric lumbosacral spines (51.3 ± 9.8 years) were implanted with 6° or 11° prostheses (ProDisc-L) with four combinations of superior/inferior lordosis (6°/0°, 3°/3°, 11°/0°, 3°/8°). Specimens were tested intact and after prostheses implantation with different lordosis distributions. Center of rotation (COR) and range of motion (ROM) were quantified.
  
  
  RESULTS
  Six-degree lordosis prostheses (n = 7) showed no difference in flexion-extension ROM, regardless of design (6°/0° or 3°/3°) (p > 0.05). In lateral bending (LB), both designs reduced ROM (p < 0.05). In axial rotation, only the 3°/3° design reduced ROM (p < 0.05). Eleven-degree lordosis prostheses (n = 5) showed no difference in flexion-extension ROM for either design (p > 0.05). LB ROM decreased with distributed lordosis prostheses (3°/8°) (p < 0.05). Overall, L5-S1 range of motion was not markedly influenced by lordosis distribution among the two prosthesis endplates. The ProDisc-L prosthesis design where all lordosis is concentrated in the superior endplate yielded COR locations that were anterior and caudal to intact controls. The prosthesis with lordosis distributed between the two endplates yielded a COR that tended to be closer to intact.
  
  
  CONCLUSIONS
  Further clinical and biomechanical studies are needed to assess the long-term impact of lordosis angle distribution on the fate of the facet joints.
authors.affiliation: Musculoskeletal Biomechanics Laboratory, Edward Hines Jr VA Hospital, Hines, IL, USA.
authors.forename: Parmenion P
authors.initials: PP
authors.lastname: Tsitsopoulos
authors.forename: Bartosz
authors.initials: B
authors.lastname: Wojewnik
authors.forename: Leonard I
authors.initials: LI
authors.lastname: Voronov
authors.forename: Robert M
authors.initials: RM
authors.lastname: Havey
authors.forename: Susan M
authors.initials: SM
authors.lastname: Renner
authors.forename: Julia
authors.initials: J
authors.lastname: Zelenakova
authors.forename: Braden
authors.initials: B
authors.lastname: McIntosh
authors.forename: Gerard
authors.initials: G
authors.lastname: Carandang
authors.forename: Celeste
authors.initials: C
authors.lastname: Abjornson
authors.forename: Avinash G
authors.initials: AG
authors.lastname: Patwardhan
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D002102:Cadaver; D017586:Diskectomy / Q000379:methods; D006801:Humans; D007403:Intervertebral Disc / Q000502:physiology / Q000601:surgery*; D008141:Lordosis / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control; D008159:Lumbar Vertebrae / Q000502:physiology / Q000601:surgery*; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D011474:Prosthesis Design / Q000379:methods; D016059:Range of Motion, Articular / Q000502:physiology; D012447:Sacrum / Q000502:physiology / Q000601:surgery*; D059145:Total Disc Replacement / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D021801:Zygapophyseal Joint / Q000502:physiology / Q000601:surgery