Accuracy and Safety of Image Guided Percutaneous Injection of Gelified Ethanol (Discogel®) in the Intervertebral Disc in Dogs

Accuracy of image guided injection of the intervertebral discs and the distribution and safety of a gelified ethanol product was investigated in two phases. In the first phase, the ability to accurately perform percutaneous injection of gelified ethanol into intervertebral discs of cadaver dogs using three imaging modalities was evaluated (n=14). Injections were performed at random sites along the vertebral column (n=78 discs). Systematic dissection was performed to confirm the location of the injected preparation. The material was successfully delivered to the nucleus pulposus in 55 of 78 (71%) intervertebral discs. Forty-nine of 78 (63%) injections had leakage of the injected material including 10 (13%) with material in the vertebral canal. The success of injections did not differ by site (p=0.9337) or body weight (p=0.3273). The odds of a successful injection without significant leakage were 12 times higher when using computed tomography (CT) compared to ultrasound (p=0.0026), and trended towards significantly higher with CT than fluoroscopy (p=0.0620). In the second phase, the feasibility of image guided injection developed in phase I was tested in 10 healthy dogs at the lumbosacral disc. Successful injection of the gelified ethanol was achieved in all 10 dogs, with material evident in the vertebral canal in 4 dogs. Short-term (n=10) and long-term (n=5) follow-up CT and magnetic resonance imaging (MRI) as well as neurological examinations were used to evaluate the effects of the injection. All dogs tolerated the injection well; there were no clinical adverse reactions noted over the study period. The long term follow up CT and MRI studies revealed a static appearance in 3 of 5 dogs with evidence of redistribution of the injected preparation in 2 of 5 dogs. In conclusion, percutaneous injection of the intervertebral discs is achievable with multiple imaging modalities but is most accurate using CT guidance. Injection of gelified ethanol into the lumbosacral disc of healthy dogs is well tolerated with no adverse effects noted, even with mild leakage of material from the disc. This work provides a solid foundation for the development of this technique as a potential treatment option for dogs with intervertebral disc protrusions.