title: Biomechanical comparison of instrumented and uninstrumented multilevel cervical discectomy versus corpectomy.
abstract: METHODS
  In vitro flexibility test comparing biomechanics of cervical corpectomy versus discectomy with and without instrumentation.
  
  
  OBJECTIVE
  To evaluate whether the additional effort required to perform multilevel discectomies instead of corpectomies is worthwhile biomechanically.
  
  
  BACKGROUND
  Both cervical corpectomy and discectomy have been shown to be effective clinically. No previous biomechanical comparison exists.
  
  
  METHODS
  Fourteen human cadaveric cervical spines were studied: 1) intact, 2) after discectomy and wedge grafting at C4-C5, C5-C6, and C6-C7 (Group 1) or corpectomy and strut grafting of C5 and C6 (Group 2), 3) after attaching a locking metal plate from C4-C7, and 4) after adding posterior locking lateral mass screw/rod instrumentation across C4-C7. Non-constraining, nondestructive torques induced flexion, extension, lateral bending, and axial rotation (maximum, 1.5 Nm) while angular motion was measured stereophotogrammetrically.
  
  
  RESULTS
  Discectomy and grafting did not alter the range of motion (ROM) significantly from normal during any loading mode (P > 0.11). Corpectomy and grafting allowed a significantly greater range of motion than normal during flexion, lateral bending, and axial rotation (P < 0.05). Addition of an anterior plate reduced ROM to significantly less than normal during all loading modes in both groups (P < 0.005). Addition of posterior instrumentation further reduced ROM significantly in both groups (P < 0.01). There was no significant difference in ROM between corpectomy and discectomy groups in any loading mode whether uninstrumented (P > 0.18), anteriorly plated (P > 0.33), or anteriorly and posteriorly instrumented (P > 0.30).
  
  
  CONCLUSIONS
  Less difference in stability was observed than was predicted between specimens receiving multilevel discectomy versus multilevel corpectomy, regardless of whether specimens were left unplated, plated anteriorly, or fixated with combined anterior/posterior instrumentation.
authors.affiliation: Spinal Biomechanics, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, AZ 85013, USA.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Galler
authors.forename: Seref
authors.initials: S
authors.lastname: Dogan
authors.forename: Mary S
authors.initials: MS
authors.lastname: Fifield
authors.forename: Hakan
authors.initials: H
authors.lastname: Bozkus
authors.forename: Robert H
authors.initials: RH
authors.lastname: Chamberlain
authors.forename: Volker K H
authors.initials: VK
authors.lastname: Sonntag
authors.forename: Neil R
authors.initials: NR
authors.lastname: Crawford
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D016025:Bone Transplantation; D002102:Cadaver; D002574:Cervical Vertebrae; D019299:Decompression, Surgical / Q000295:instrumentation*; D017586:Diskectomy / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000503:physiopathology / Q000601:surgery*; D007593:Joint Instability / Q000503:physiopathology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D009984:Orthopedic Fixation Devices; D019637:Orthopedic Procedures / Q000295:instrumentation; D016059:Range of Motion, Articular; D012107:Research Design; D012399:Rotation