WordNet

(mechanics) the equal and opposite force that is produced when any force is applied to a body; "every action has an equal and opposite reaction"
a response that reveals a persons feelings or attitude; "he was pleased by the audiences reaction to his performance"; "John feared his mothers reaction when she saw the broken lamp"
a bodily process occurring due to the effect of some antecedent stimulus or agent; "a bad reaction to the medicine"; "his responses have slowed with age" (同)response
doing something in opposition to another way of doing it that you dont like; "his style of painting was a reaction against cubism"
an idea evoked by some experience; "his reaction to the news was to start planning what to do"
extreme conservatism in political or social matters; "the forces of reaction carried the election"

PrepTutorEJDIC

{名}(…に対する)『反応』《+『to』+『名』》 / 〈U〉(…に対する)(政治的・社会的な)『反動』,逆コース《+『against』+『名』》 / 〈U〉〈C〉化学反応,化学変化 / 〈U〉〈C〉(物理学で)反作用

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/05/07 15:32:09」(JST)

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A periosteal reaction is the formation of new bone in response to injury or other stimuli of the periosteum surrounding the bone.^[1] It is most often identified on X-ray films of the bones.

Etiology

Examples of periosteal reactive bone in selected specimens of Triceratops

A periosteal reaction can result from a large number of causes, including injury and chronic irritation due to a medical condition such as hypertrophic osteopathy, bone healing in response to fracture, chronic stress injuries, subperiosteal hematomas, osteomyelitis, and cancer of the bone. It may also occur as part of thyroid acropachy, a severe sign of the autoimmune thyroid disorder Grave's disease.

Other causes include Menkes kinky hair syndrome and hypervitaminosis A.^[2]

It can take about three weeks to appear.^[3]

Diagnosis

The morphological appearance can be helpful in determining the cause of a periosteal reaction (for example, if other features of periostitis are present), but is usually not enough to be definitive. Diagnosis can be helped by establishing if bone formation is localized to a specific point or generalized to a broad area. The appearance of the adjacent bone will give clues as to which of these is the most likely cause.

Appearances include solid, laminated, spiculated, and Codman's triangle.^[4]

References

^ Ved N, Haller JO (November 2002). "Periosteal reaction with normal-appearing underlying bone: a child abuse mimicker". Emerg Radiol 9 (5): 278–82. doi:10.1007/s10140-002-0252-5. PMID 15290554.
^ Wood W. Lovell; Robert B. Winter; Raymond T. Morrissy; Stuart L. Weinstein (2006). Lovell and Winter's pediatric orthopaedics. Lippincott Williams & Wilkins. pp. 196–. ISBN 978-0-7817-5358-6. Retrieved 15 April 2010.
^ Francis A. Burgener; Martti Kormano; Tomi Pudas (23 November 2005). Bone and Joint Disorders. Thieme. pp. 41–. ISBN 978-1-58890-445-4. Retrieved 15 April 2010.
^ Richard H. Daffner (1 February 2007). Clinical radiology: the essentials. Lippincott Williams & Wilkins. pp. 405–. ISBN 978-0-7817-9968-3. Retrieved 15 April 2010.

UpToDate Contents

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1. 脛骨および腓骨のストレス骨折 stress fractures of the tibia and fibula
2. 成人における骨髄炎の概要 overview of osteomyelitis in adults
3. 児童虐待の整形外科的側面 orthopedic aspects of child abuse
4. 骨髄炎の疑いがある状況での画像検査法 approach to imaging modalities in the setting of suspected osteomyelitis
5. 小児および思春期における良性骨腫瘍：概要 benign bone tumors in children and adolescents an overview

English Journal

MRI of chondromyxoid fibroma.

Kim HS, Jee WH, Ryu KN, Cho KH, Suh JS, Cho JH, Choi YS, Lee SM, Lee JM, Sung MS, Kim JY, Jung ES, Chung YG, Ok IY.SourceDepartment of Radiology, Seoul St Mary's Hospital, School of Medicine, The Catholic University of Korea, Seoul.
Acta radiologica (Stockholm, Sweden : 1987).Acta Radiol.2011 Aug 11. [Epub ahead of print]
Background Chondromyxoid fibroma is a rare benign primary bone tumor of cartilage. Despite a characteristic radiographic appearance, chondromyxoid fibroma with atypical radiographic findings may mimic more common tumors. Purpose To describe the MR findings of chondromyxoid fibroma. Material and Meth
PMID 21835889