title: Unexpected angular or rotational deformity after corrective osteotomy.
abstract: BACKGROUND
  Codman's paradox reveals a misunderstanding of geometry in orthopedic practice. Physicians often encounter situations that cannot be understood intuitively during orthopedic interventions such as corrective osteotomy. Occasionally, unexpected angular or rotational deformity occurs during surgery.This study aimed to draw the attention of orthopedic surgeons toward the concepts of orientation and rotation and demonstrate the potential for unexpected deformity after orthopedic interventions. This study focused on three situations: shoulder arthrodesis, femoral varization derotational osteotomy, and femoral derotation osteotomy.
  
  
  METHODS
  First, a shoulder model was generated to calculate unexpected rotational deformity to demonstrate Codman's paradox. Second, femoral varization derotational osteotomy was simulated using a cylinder model. Third, a reconstructed femoral model was used to calculate unexpected angular or rotational deformity during femoral derotation osteotomy.
  
  
  RESULTS
  Unexpected external rotation was found after forward elevation and abduction of the shoulder joint. In the varization and derotation model, closed-wedge osteotomy and additional derotation resulted in an unexpected extension and valgus deformity, namely, under-correction of coxa valga. After femoral derotational osteotomy, varization and extension of the distal fragment occurred, although the extension was negligible.
  
  
  CONCLUSIONS
  Surgeons should be aware of unexpected angular deformity after surgical procedure involving bony areas. The degree of deformity differs depending on the context of the surgical procedure. However, this study reveals that notable deformities can be expected during orthopedic procedures such as femoral varization derotational osteotomy.
authors.forename: Seung Yeol
authors.initials: SY
authors.lastname: Lee
authors.forename: Jiwon
authors.initials: J
authors.lastname: Jeong
authors.forename: Kyungho
authors.initials: K
authors.lastname: Lee
authors.forename: Chin Youb
authors.initials: CY
authors.lastname: Chung
authors.forename: Kyoung Min
authors.initials: KM
authors.lastname: Lee
authors.forename: Soon-Sun
authors.initials: SS
authors.lastname: Kwon
authors.forename: Young
authors.initials: Y
authors.lastname: Choi
authors.forename: Tae Gyun
authors.initials: TG
authors.lastname: Kim
authors.forename: Jeong Ik
authors.initials: JI
authors.lastname: Lee
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea. jehee@mrl.snu.ac.kr.
authors.forename: Jehee
authors.initials: J
authors.lastname: Lee
authors.forename: Moon Seok
authors.initials: MS
authors.lastname: Park
mesh_terms: D001174:Arthrodesis / Q000009:adverse effects; D006801:Humans; D008297:Male; D008954:Models, Biological; D010003:Osteoarthritis / Q000175:diagnosis / Q000601:surgery*; D010027:Osteotomy / Q000009:adverse effects*; D016059:Range of Motion, Articular / Q000502:physiology; D019651:Plastic Surgery Procedures / Q000009:adverse effects*; D012399:Rotation / Q000009:adverse effects; D012785:Shoulder Joint / Q000473:pathology / Q000601:surgery*