Hyaluronic acid (HA) is a naturally occurring polysaccharide that has been shown to be beneficial in various clinical settings, such as in opthalmic surgery or for intra-articular injections. This study was designed to evaluate the effect of epidurally injected HA as an agent for decreasing pain in an animal model of chronic dorsal root ganglion compression.

A small stainless steel rod was inserted into L4-5 intervertebral foramen in the rat, to develop intervertebral foramen stenosis and chronic DRG compression. Twenty-seven rats were assigned to the saline group (n = 9), HA group (n = 9), or the no treatment (control) group (n = 9). In the saline group and the HA group, 0.1 ml of 0.9% saline and the same volume of HA were injected into the epidural space through an epidural catheter. Behavioral tests for thermal hyperalgesia was performed for five weeks after epidural injection.

The hindpaw on the injured side in the control group and in the saline group showed a significant reduction in the latency of foot withdrawal to noxious heat. Rats in the HA group showed a significant reduction of hyperalgesia in the thermal test (P < 0.05).

Our findings suggest the epidurally administered HA may be effective for relieving lumbar radicular pain and low back pain produced by chronic DRG compression in the clinical setting.