Intradiscal and intramuscular injection of discogel(®) - radiopaque gelified ethanol: pathological evaluation

This study assessed the impact and modification of intradiscal, intraforaminal, epidural and intramuscular swine injection of a new material, Discogel(®)- radiopaque gelified ethanol- recently introduced for the mini-invasive treatment of herniated disc. Discogel(®) is a sterile viscous solution containing ethyl alcohol, cellulose derivative product, added to a radio-opaque element, tungsten. The pig was sedated and under fluoroscopy guidance a needle was positioned within disc L1-L2 followed by intradiscal, intraforaminal, epidural and intramuscular injection of 1 ml of Discogel. As disc control level L4-L5 was considered where nothing was injected. The pig was sacrifed 48 h after injection of discogel and the spine from D10 to S1 was removed and fixed in 10% buffered formalin. The anatomical specimens were cut with an electric saw and analyzed by routine technique then stained with formalin. The specimens containing bone material were treated by DEKAL solution. The specimens were stained with hematoxylin-eosin method and then analyzed by histochemical (Masson -Van Gieson PAS and trichromic stains ) and immunochemical methods. Morphostructural examination disclosed a granular material coloured black by hematoxylin-eosin method (tungsten) in paravertebral tissue both in the muscular and connective tissue. Some inflammatory elements like lymphomonocyte cells and venous stasis were found. No alteration was found where discogel was injected, and the nucleus pulposus, disc, chondromixoid and root ganglium were normal. After intradiscal, intraforaminal, epidural and intramuscular injection of Discogel(®) no morpho-structural changes in nuclear tissue and annulus were found. Further studies on pigs with immunohistochemical analysis after treatment will confirm the morphological alterations induced by discogel and its action.