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Regression of Retro-odontoid Pseudotumor Using External Orthosis without Atlantoaxial Fusion

A Case Report

Nakazawa, Toshiyuki MD, PhD1; Inoue, Gen MD, PhD1; Imura, Takayuki MD1; Miyagi, Masayuki MD, PhD1; Saito, Wataru MD, PhD1; Shirasawa, Eiki MD1; Kawakubo, Ayumu MD1; Takaso, Masashi MD, PhD1

doi: 10.2106/JBJS.CC.18.00329
Case Reports

Case: We treated an 87-year-old woman with noninflammatory retro-odontoid pseudotumor induced by atlantoaxial instability (AAI) using only a Philadelphia collar. Because of perioperative risk factors, fusion surgery was canceled; nevertheless, the neurological symptoms improved gradually. After 11 months of nonoperative treatment, the follow-up magnetic resonance imaging demonstrated that the pseudotumor's size was obviously diminished. Orthosis was applied for 2 years, and after its removal, the pseudotumor's size remained the same at the final 7-year follow-up.

Conclusions: External orthosis is one treatment option for pseudotumor with AAI, especially in patients with significant comorbidities for whom surgical procedures are relatively contraindicated.

1Department of Orthopaedic Surgery, Kitasato University School of Medicine, Kanagawa, Japan

E-mail address for G. Inoue:

Investigation performed at Department of Orthopaedic Surgery, Kitasato University School of Medicine, Kanagawa, Japan

Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (

Copyright © 2019 by The Journal of Bone and Joint Surgery, Incorporated
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