title: Fracture originated at the tip of heterotopic ossification of femur by minor external force: report of two cases.
abstract: Fracture of femur without evidence of severe osteoporosis rarely occurs as a result of minor external force such as a gentle passive or an active range of motion exercises. We report two cases of femoral shaft fracture occurred at the tip of heterotopic ossification of femur by a minor external force, in which the involved femur shows no evidence of remarkable osteoporosis. The possible mechanism inferred by authors is as follows: 1) heterotopic ossification limits range of motion of the hip joint; 2) a new lever arm is formed at the tip of heterotopic ossification where energy can be concentrated; 3) therefore, fractures develop even by a minor external force. Search for similar cases and further discussions on possible mechanisms and prevention of femoral fractures in patients with heterotopic ossification will be necessary.
authors.affiliation: Department of Physical Medicine and Rehabilitation, Ajou University School of Medicine, Suwon, Korea. syyim@madang.ajou.ac.kr
authors.forename: S Y
authors.initials: SY
authors.lastname: Yim
authors.forename: S H
authors.initials: SH
authors.lastname: Yoon
authors.forename: I Y
authors.initials: IY
authors.lastname: Lee
authors.forename: U W
authors.initials: UW
authors.lastname: Rah
authors.forename: H W
authors.initials: HW
authors.lastname: Moon
mesh_terms: D000328:Adult; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000209:etiology*; D006801:Humans; D008297:Male; D009999:Ossification, Heterotopic; D011859:Radiography