title: Anatomical predisposition of the ankle joint for lateral sprain or lateral malleolar fracture evaluated by radiographic measurements.
abstract: BACKGROUND
  Injury mechanism and the amount of force are important factors determining whether a fracture or sprain occurs at the time of an ankle inversion injury. However, the anatomical differences between the ankle fracture and sprain have not been investigated sufficiently. This study was performed to investigate whether an anatomical predisposition of the ankle joint results in a lateral malleolar fracture or lateral ankle sprain.
  
  
  METHODS
  Two groups of consecutive patients, one with lateral malleolar fracture (274 patients, mean age 49.0 years) and the other with lateral ankle sprain (400 patients, mean age 38.4 years), were evaluated. Ankle radiographs were examined for 7 measures: distal tibial articular surface (DTAS) angle, bimalleolar tilt (BT), medial malleolar relative length (MMRL), lateral malleolar relative length (LMRL), medial malleolar slip angle (MMSA), anterior inclination of tibia (AI), and fibular position (FP). After an interobserver reliability test, the radiographic measurements were compared between the 2 groups. Linear regression analysis was performed to correct for age and sex effects between the groups.
  
  
  RESULTS
  The fracture group and the sprain group showed significant differences in BT (P = .001), MMSA (P < .001), AI (P = .023), and FP (P < .001). In multiple regression analysis, after adjusting for age and sex effects, fracture and sprain groups showed a significant difference in BT (P = .001), MMRL (P < .001), MMSA (P < .001), and FP (P < .001).
  
  
  CONCLUSIONS
  The lateral malleolar fracture group tended to show more bony constraint than that of the lateral ankle sprain group. Further 3-dimensional assessment of the bony structure and subsequent biomechanical studies are needed to elucidate the mechanism of injury according to the various types of ankle fractures and ankle sprain.
  
  
  METHODS
  Level III, retrospective comparative study.
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea.
authors.forename: Kyoung Min
authors.initials: KM
authors.lastname: Lee
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea.
authors.forename: Chin Youb
authors.initials: CY
authors.lastname: Chung
authors.affiliation: Department of Orthopaedic Surgery, Kwandong University Myongji Hospital, Kyungki, Korea.
authors.forename: Ki Hyuk
authors.initials: KH
authors.lastname: Sung
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea.
authors.forename: SeungYeol
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea.
authors.forename: Tae Gyun
authors.initials: TG
authors.lastname: Kim
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea.
authors.forename: Young
authors.initials: Y
authors.lastname: Choi
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea overmas99@hanmai.net.
authors.forename: Ki Jin
authors.initials: KJ
authors.lastname: Jung
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea.
authors.forename: Yeon Ho
authors.initials: YH
authors.lastname: Kim
authors.affiliation: School of Mechanical Engineering, Chung-Ang University, Seoul, Korea.
authors.forename: Seung Bum
authors.initials: SB
authors.lastname: Koo
authors.affiliation: Department of Orthopaedic Surgery, Seoul National University Bundang Hospital, Kyungki, Korea.
authors.forename: Moon Seok
authors.initials: MS
authors.lastname: Park
mesh_terms: D000328:Adult; D000368:Aged; D064386:Ankle Fractures / Q000000981:diagnostic imaging* / Q000473:pathology; D016512:Ankle Injuries / Q000000981:diagnostic imaging* / Q000473:pathology; D000843:Ankle Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012189:Retrospective Studies
keywords: anatomical predisposition; ankle fracture; ankle sprain; radiographs