Variables affecting disc size in the lumbar spine of rabbits: Anesthesia, paralysis, and disc injury

Abstract

Methods have been developed that permit repetitive radiographic measurement of the lumbar intervertebral disc space in a rostral-caudal direction (width) in the anesthetized laboratory rabbit. Using isolated control discs and injured discs in which narrowing has been induced for chronic and acute periods, the widths of the lumbar intervertebral disc spaces determined ratio-graphically correlate with widths determined histologically (p less than 0.000, r = 0.75). Both an increase (widening) and a decrease (narrowing) in disc width were observed using radiography after different experimental treatments. Anesthesia and lower-body paralysis (an experimentally induced inability to bear weight on and to perceive a pinch stimulus in hind limbs) caused widening of the discs: anesthesia causing a general widening throughout the lumbar spine and lower-body paralysis causing a specific widening low in the lumbar spine. Both disc injection and piercing the disc with needles to recover nucleus pulposus material caused narrowing of the discs. Acridine-orange injection induced a narrowing accompanied by osteophytosis. Experimentally induced narrowing at L4-5 (the result of injury to the disc) resulted in narrowing also at L2-3. These findings are consistent with the hypothesis that in vivo disc-width size in the young rabbit depends on both the quantity of nucleus pulposus material and the force-generating activities of the adjacent spinal muscles, and that disc injury at one level stimulates narrowing at other levels.

Are animal models useful for studying human disc disorders/degeneration?

“…However, Oshima et al reported that the swelling pressure in bovine tail discs is similar to that in human lumbar discs, indicating that the prevailing compressive stress of the tail discs is probably of similar magnitude to lumbar discs. Anaesthesia [110,135] produces a similar increase in disc thickness as that which results from applying distraction forces of 60% bodyweight (c. 0.25 MPa) to the tail, which suggests that the ambient loading is of similar magnitude. 2.…”

Experimental model of multidirectional disc hernia in rats

“…We have found limitation of mobility in the herniated segment [13], which could correspond to increased forces applied through the spinal muscles [11]. An association between annular fracture and discal protrusion has already been described [6,17], but this may not be correct because of possible histological artefacts [5].…”

“…Bipedal rats have been used to reproduce the human situation [15], the maintenance of forced bending of the spine has been studied [9,11] and cyclical changes have been applied to the disc [1,7,9]. Others have used direct action on the disc by damaging the annulus [8], increasing disc pressure by the injection of liquid [11], or resection of the posterior arch to produce instability [13]. Takenaka produced an acute disc hernia by bending the rat's tail [14], but this method is difficult to reproduce or quantify.…”

“…The aim of our work is to use an experimental model which will reliably reproduce disc herniations, and to evaluate the structural and histological changes [5,10,11,17].…”

Technique and method development for intervertebral disc (IVD) research

“…For instance, the swelling pressure of bovine tail discs is similar to that of human lumbar discs [80] and the loading in bovine discs is similar to that of human [81,82]. Besides, bovine tail discs are also less gel-like compared to immature porcine discs which resemble discs in developed human more closely.…”