title: Direction of the oblique medial malleolar osteotomy for exposure of the talus.
abstract: BACKGROUND
  A medial malleolar osteotomy is often indicated for operative exposure of posteromedial osteochondral defects and fractures of the talus. To obtain a congruent joint surface after refixation, the oblique osteotomy should be directed perpendicularly to the articular surface of the tibia at the intersection between the tibial plafond and medial malleolus. The purpose of this study was to determine this perpendicular direction in relation to the longitudinal tibial axis for use during surgery.
  
  
  METHODS
  Using anteroposterior mortise radiographs and coronal computed tomography (CT) scans of 46 ankles (45 patients) with an osteochondral lesion of the talus, two observers independently measured the intersection angle between the tibial plafond and medial malleolus. The bisector of this angle indicated the osteotomy perpendicular to the tibial articular surface. This osteotomy was measured relative to the longitudinal tibial axis on radiographs. Intraclass correlation coefficients (ICC) were calculated to assess reliability.
  
  
  RESULTS
  The mean osteotomy was 57.2 ± 3.2° relative to the tibial plafond on radiographs and 56.5 ± 2.8 on CT scans. This osteotomy corresponded to 30.4 ± 3.7° relative to the longitudinal tibial axis. The intraobserver (ICC, 0.90-0.93) and interobserver (ICC, 0.65-0.91) reliability of these measurements were good to excellent.
  
  
  CONCLUSIONS
  A medial malleolar osteotomy directed at a mean 30° relative to the tibial axis enters the joint perpendicularly to the tibial cartilage, and will likely result in a congruent joint surface after reduction.
authors.affiliation: Department of Orthopaedic Surgery, Orthopaedic Research Center Amsterdam, Academic Medical Center, University of Amsterdam, Meibergdreef 9, 1105 AZ, Amsterdam, The Netherlands. c.j.vanbergen@amc.nl
authors.forename: Christiaan J A
authors.initials: CJ
authors.lastname: van Bergen
authors.forename: Gabriëlle J M
authors.initials: GJ
authors.lastname: Tuijthof
authors.forename: Inger N
authors.initials: IN
authors.lastname: Sierevelt
authors.forename: C Niek
authors.initials: CN
authors.lastname: van Dijk
mesh_terms: D000328:Adult; D016512:Ankle Injuries / Q000000981:diagnostic imaging* / Q000601:surgery; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D017102:Fracture Healing / Q000502:physiology; D050723:Fractures, Bone / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010027:Osteotomy / Q000379:methods*; D011300:Preoperative Care / Q000379:methods; D016059:Range of Motion, Articular / Q000502:physiology; D012189:Retrospective Studies; D018570:Risk Assessment; D013628:Talus / Q000000981:diagnostic imaging* / Q000293:injuries / Q000601:surgery*; D014057:Tomography, X-Ray Computed / Q000379:methods; D016896:Treatment Outcome; D055815:Young Adult