Biomechanical evaluation of new posterior occipitocervical instrumentation system.
Twelve fresh-frozen cadaveric occipitocervical specimens were randomized based on dual energy xray absorptiometry analysis of bone mineral density. The specimens were subjected to physiologic loads in a device that applied pure unconstrained flexion and extension, lateral bending, and axial rotational moments. The spines were tested intact and after major injury simulating transoral decompression of the dens. Biomechanical testing using pure moments with physiologic loads (< 1.5 N-m) was used to compare stability of posterior occipitocervical plates and screws, loop and cable construct, and new cervical rod and screw system. The injury created significantly less stiffness and greater range of motion and neutral zone at C1-C2 in flexion and extension and lateral bending and greater range of motion and neutral zone in axial rotation than the intact state. In lateral bending, the new rod construct had significantly lower mean values for range of motion than the loop and the plate construct. In axial rotation, the rod construct had a significantly higher mean value for stiffness than the other two devices and a significantly lower mean value for range of motion than the loop. The new rod-based instrumentation system for occipitocervical fixation is biomechanically equivalent or superior to a plate and screw construct and a rod and cable system.
Currier
Bradford L
BL
Department of Orthopedic Surgery, Mayo Clinic, Rochester, MN 55905, USA. currier.bradford@mayo.edu
Papagelopoulos
Panayiotis J
PJ
Neale
Patricia G
PG
Andreshak
John L
JL
Hokari
Yukitaka
Y
Berglund
Lawrence J
LJ
Larson
Dirk R
DR
Fisher
Dean R
DR
An
Kai-Nan
KN
D015502:Absorptiometry, Photon; D000328:Adult; D001696:Biomechanical Phenomena; D015519:Bone Density; D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D002574:Cervical Vertebrae / Q000601:surgery*; D006801:Humans; D016268:Internal Fixators; D009777:Occipital Bone / Q000601:surgery*; D016059:Range of Motion, Articular; D013124:Spinal Injuries / Q000601:surgery*; D013314:Stress, Mechanical