Biomechanical analysis of multilevel fixation methods in the lumbar spine.
METHODS
The authors measured and compared the stiffness of cadaveric lumbar spines stabilized with several anterior interbody fusion devices. The information obtained provides a foundation for determining how methods of anterior lumbar fixation can maximize rigidity and promote development of bony fusion.


OBJECTIVE
To compare the utility of three anterior spinal instrumentation systems for stabilizing the lumbar spine.


BACKGROUND
Anterior spinal instrumentation is used to prevent progressive spinal deformity and maintain correction after spinal fusion surgery. Newer instrumentation systems developed for anterior interbody fusions can be inserted by minimally invasive procedures. The stability of these systems has not been tested adequately in human cadaveric specimens.


METHODS
Fusion constructs were evaluated in 12 human cadaveric specimens sequentially loaded in axial compression and torsion, flexion and extension, and lateral bending. The fusion constructs used were 1) two anterior bilateral threaded interbody fusion devices, 2) lateral hollow interbody screws (Texas Scottish Rite Hospital-B screws), and 3) femoral allograft and conventional anterior Texas Scottish Rite Hospital instrumentation.


RESULTS
The construct with Texas Scottish Rite Hospital-B screws connected by a rod produced stiffness comparable with that produced by conventional Texas Scottish Rite Hospital instrumentation with femoral ring allografts. The threaded interbody fusion device stiffness tested in axial rotation was comparable with that achieved with Texas Scottish Rite Hospital instrumentation.


CONCLUSIONS
Our data demonstrate the effectiveness of threaded interbody fusion device and the Texas Scottish Rite Hospital-B screw in immobilizing the L3-L4 and L4-L5 disc spaces. Rigidity of fixation in the lumbar spine may aid in the maintenance of lordosis.
Glazer
P A
PA
Department of Orthopaedic Surgery, University of California, San Francisco, USA.
Colliou
O
O
Klisch
S M
SM
Bradfore
D S
DS
Bueff
H U
HU
Lotz
J C
JC
D015502:Absorptiometry, Photon; D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D001863:Bone Screws; D016025:Bone Transplantation / Q000379:methods*; D005260:Female; D005269:Femur; D006801:Humans; D016268:Internal Fixators; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D018583:Pliability; D012399:Rotation; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods