Regression of Retro-odontoid Pseudotumor Using External Orthosis without Atlantoaxial Fusion. - Toshiyuki Nakazawa; Gen Inoue; Takayuki Imura; Masayuki Miyagi; Wataru Saito; Eiki Shirasawa; Ayumu Kawakubo; Masashi Takaso (JBJS Case Connector, 2019)