Puncture of a lumbar intervertebral disc induces changes in spontaneous pain behavior

Study Design. Changes in spontaneous behavior was studied in rats after a controlled puncture of a lumbar intervertebral disc. Objective. To study if puncture of a lumbar disc would induce recordable changes in spontaneous pain behavior. Summary of Background Data. Anular tears are common and may be found both in patients with low back pain and in asymptomatic patients. It has been suggested that anular injury may relate to low back pain either by stimulation of local sensory receptors in the posterior part of the anulus fibrosus or by ingrowth of newly formed nerve fibers into the deeper parts of the disc. The objective of the study was to analyze if a controlled puncture of a lumbar intervertebral disc might induce recordable changes in spontaneous behavior of rats. Methods. After anesthesia, the L4-L5 disc was punctured in 10 rats. Ten other rats received sham surgery. Spontaneous behavior was assessed at days 1, 3, 7, 14, and 21 after surgery. Results. Statistically significant differences in behavior were seen at all days analyzed. Most consistent were increases in grooming and in wet-dog shakes. Conclusion. Puncture of a lumbar intervertebral disc in the rat produces changes in spontaneous behavior mainly seen as increased grooming and wet-dog shakes, 2 behaviors that have been suggested to indicate stress and pain.