Two-level spinal stenosis in minipigs. Hemodynamic effects of exercise.
METHODS
Twenty-two Göttingen minipigs were trained to run on a treadmill. Two-level lumbar spinal stenosis was created in 12 pigs, 10 were unoperated control subjects. Blood flow of the spinal cord and nerve roots was determined with microspheres at rest, during exercise, and after exercise.


OBJECTIVE
To study the effect of lumbar spinal stenosis and exercise on blood flow of spinal neural tissue.


BACKGROUND
Neurogenic claudication, the key symptom of lumbar spinal stenosis, may be caused by vascular impairment or mechanical distress of neural tissue during exercise. Experimental compression of the cauda equina causes reversible nerve root edema, stasis, blood flow decrease, and compromised neural function. The vascular pathophysiology of spinal stenosis during exercise has not been studied previously.


METHODS
Pigs were trained daily for 3 months. Two-level 25% lumbar spinal stenosis was introduced by placement of stenosing bands around the dural sac. Neurologic function was monitored before surgery by evoked potentials and after surgery by the Tarlov score. Regional blood flow in lumbosacral neural tissue was measured 3 days after chronic catheterization using microspheres at rest, during exercise at 3 km/h for 15 minutes, and at rest 30 minutes after exercise.


RESULTS
Blood flow of grey and white matter increased during exercise in both groups, with no differences between groups. slight hyperemia prevailed after exercise in white matter of the stenotic area but not in grey matter. Nerve root blood flow was largely unchanged in control subjects during exercise but was reduced in spinal stenosis at rest, further depressed during exercise, and normalized after exercise. Dural blood flow was elevated throughout.


CONCLUSIONS
The study suggests that exercise-induced impairment of spinal nerve root blood flow plays a role in the pathophysiology of neurogenic claudication.
Jespersen
S M
SM
Department of Orthopaedics, University of Aarhus, Denmark.
Hansen
E S
ES
Høy
K
K
Christensen
K O
KO
Lindblad
B E
BE
Ahrensberg
J
J
Bünger
C
C
D000818:Animals; D004195:Disease Models, Animal; D004388:Dura Mater / Q000098:blood supply / Q000502:physiology; D005071:Evoked Potentials; D005080:Exercise Test; D006439:Hemodynamics / Q000502:physiology; D008161:Lumbosacral Region / Q000098:blood supply / Q000294:innervation / Q000502:physiology; D005082:Physical Exertion / Q000502:physiology; D013116:Spinal Cord / Q000098:blood supply / Q000502:physiology; D013126:Spinal Nerve Roots / Q000098:blood supply / Q000502:physiology; D013130:Spinal Stenosis / Q000503:physiopathology*; D013552:Swine; D013556:Swine, Miniature