椎間関節の炎症は神経根障害を惹起するか？―ラット腰椎椎間関節炎モデルによる検討

Does Inflammation of the Facet Joint Induce Radiculopathy? : Experimental Model of an Inflammatory Facet Joint

　ラットの腰椎椎間関節炎モデルを作成して，椎間関節の炎症が神経根障害を惹起するという仮説の妥当性を検証した．椎間関節内にアジュバントを挿入して，組織学的検討と行動学的検討を行った．その結果，椎間関節軟骨の変性は，術後3日より認められた．硬膜外腔に浸潤した炎症性細胞数は，術後3日で有意に多かった．行動学的検討では，術後3，5，7日で下肢疼痛閾値の低下を認めた．以上の結果から，椎間関節に炎症が生じると，急性期には炎症反応が神経根に波及して神経根障害を惹起するという病態が存在しうる可能性が示唆された．

　The purpose of this study was to produce an experimental model of an inflammatory facet joint, and test the hypothesis that inflammation of the facet joint induces radiculopathy. Complete adjuvant was inserted into the facet joint in rats. Saline was used in the control group. The changes in the cartilage were assessed histologically using the modified Mankin's score. The number of inflammatory cells infiltrating into the epidural space were counted. Mechanical allodynia was determined by the von Frey test. Degeneration of the cartilage was found from 3 days after surgery and prolonged over time. The number of inflammatory cells infiltrating into the epidural space was significantly larger in the inflammatory joint group at 3 days. Mechanical allodynia was observed in the inflammatory joint group from 3 days after surgery and gradually recovered during a 28-day period. This finding suggests the possibility that inflammation of the facet joint spreads to the epidural space and induces radiculopathy.