A model for chronic nerve root compression studies. Presentation of a porcine model for controlled, slow-onset compression with analyses of anatomic aspects, compression onset rate, and morphologic and neurophysiologic effects.
METHODS
Compression onset rate, anatomic aspects, and morphologic and neurophysiologic effects in spinal nerve roots were studied in a nerve root compression model in pigs.


OBJECTIVE
To analyze the compression onset rate by measuring the gradual reduction of the inner diameter of the constrictor, the motor nerve conduction velocity by electromyography, the morphologic changes by light microscopy, and the gross and vascular anatomy by dissection and ink injections, respectively, in a model for experimental chronic nerve root compression.


BACKGROUND
Chronic nerve root compression is recognized to be related to back pain syndromes, including sciatica. Various aspects of morphologic and physiologic changes have been studied previously in models for acute compression and chronic nerve root irritation, but a controlled, graded chronic nerve root compression model has not been described.


METHODS
An ameroid constrictor was applied around a spinal nerve root just cranial to the dorsal root ganglion. The inner diameter of this constrictor gradually becomes reduced. After 1 week or 4 weeks, electromyographic measurements were performed, and tissue samples were harvested for histologic analyses. The gross and vascular anatomy of the pigs' spinal nerve roots were studied by dissection and ink injections.


RESULTS
There was a statistically significant decrease in the nerve conduction velocity in compressed compared with noncompressed spinal nerve roots after 1 week and after 4 weeks. The ameroid constrictors induced nerve fiber damage, endoneural hyperemia, bleeding, and inflammation at the compression zone. There was often a severe reduction in the number of myelinated fibers after 4 weeks.


CONCLUSIONS
A model for controlled, chronic, partial nerve root injury using a gradual compression-onset constrictor is presented. This model allows for induction of a controlled graded chronic nerve root injury and can be used for research on basic pathophysiologic mechanisms and on the effects of various interventions on nerve root injury development.
Cornefjord
M
M
Department of Orthopaedics, Sahlgren University Hospital, Gothenburg, Sweden.
Sato
K
K
Olmarker
K
K
Rydevik
B
B
Nordborg
C
C
D000818:Animals; D001672:Biocompatible Materials; D002364:Caseins; D002420:Cauda Equina / Q000098:blood supply / Q000473:pathology; D004195:Disease Models, Animal; D005727:Ganglia, Spinal / Q000033:anatomy & histology / Q000473:pathology; D020100:Hydrogels; D009408:Nerve Compression Syndromes / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D009431:Neural Conduction / Q000502:physiology*; D012447:Sacrum / Q000033:anatomy & histology; D013126:Spinal Nerve Roots / Q000033:anatomy & histology / Q000473:pathology*; D013552:Swine
D001672:Biocompatible Materials; D002364:Caseins; D020100:Hydrogels; C009719:ameroid