External fixation of the lumbar spine in a canine model.
OBJECTIVE
To compare the mechanical properties of two types of external skeletal fixation of the lumbar spine with polymethylmethacrylate (PMMA)/Steinmann pin fixation in a canine unstable spine model.


METHODS
Cadaver study.


METHODS
Lumbar spines of 17 mature large-breed dogs.


METHODS
Spine stiffness (N-m/deg) in flexion, extension, and rotation under physiological loading conditions and spine strength (N-m) in flexion were determined. Spines were destabilized at L3-L4, instrumented and retested. Fixation techniques included four-pin PMMA (PMMA4), eight-pin PMMA (PMMA8), eight-pin biplanar type I external skeletal fixator (ESF) (SK), and eight-pin spinal arch ESF (ARCHES).


RESULTS
All fixation groups were as stiff as intact spines in extension and rotation and were significantly stiffer in flexion. In flexion, both PMMA8 and ARCHES were significantly stiffer than SK, and PMMA8 was significantly stiffer than PMMA4. In rotation, PMMA8 and ARCHES were significantly stiffer than SK, and in flexion to failure, PMMA8 and ARCHES were significantly stiffer than PMMA4.


CONCLUSIONS
External skeletal spinal fixation (ESSF) has mechanical properties comparable to more commonly used PMMA/pin internal fixation techniques.


CONCLUSIONS
External fixation of the canine spine has several potential advantages over internal fixation including minimal dissection for pin placement, the ability to span affected vertebrae with placement of implants distant from the site of injury, postoperative adjustability, and complete removal of implants after healing. This study supports the biomechanical stability ESSF of the canine lumbar spine. Further studies are indicated to evaluate zones of consistently safe and secure placement of pins and clinical efficacy.
Walker
Tamara M
TM
Department of Clinical Sciences, Veterinary Teaching Hospital, Washington State University, Pullman, WA 99163, USA.
Pierce
William A
WA
Welch
Robert D
RD
D000818:Animals; D001696:Biomechanical Phenomena; D002102:Cadaver; D004285:Dogs / Q000293:injuries / Q000601:surgery*; D016267:External Fixators / Q000662:veterinary*; D005592:Fracture Fixation / Q000662:veterinary*; D008159:Lumbar Vertebrae / Q000293:injuries / Q000601:surgery*; D023421:Models, Animal