title: Does joint architecture influence the nature of intra-articular fractures?
abstract: BACKGROUND
  The architecture of joints has potentially the greatest influence on the nature of intra-articular fractures. We analysed a large number of intra-articular fractures with two aims: (1) to determine if the pattern of injuries observed supports our conjecture that the local skeletal architecture is an important factor and (2) to investigate whether associated dislocations further affect the fracture pattern.
  
  
  METHODS
  A retrospective study of intra-articular fractures over a 3.5-year period; 1003 joints met inclusion criteria and were analysed. Three independent investigators determined if fractures affected the convex dome, the concave socket, or if both joint surfaces were involved. Further review determined if a joint dislocation occurred with the initial injury. Statistical analysis was performed using a one-way frequency table, and the χ(2) test was used to compare the frequencies of concave and convex surface fractures. The odds ratios (ORs) were calculated to establish the association between the frequencies of concave and convex surface fractures, as well as between dislocation and either fracture surface involvement.
  
  
  RESULTS
  Of the 1003 fractures analysed, 956 (95.3%) involved only the concavity of the joint; in 21 fractures (2.1%) both joint surfaces were involved; and in 26 fractures (2.6%) only the convexity was involved (χ(2)=1654.9, df=2, p<0.0001). As expected, the concavity was 20.8 times more likely to fail than the convexity (11.2-36.6, 95% CI). However, the risk of fracturing the convex surface was 18.6 times higher (9.8-35.2, 95% CI) in association with a simultaneous joint dislocation, compared to those cases without a joint dislocation.
  
  
  CONCLUSIONS
  These results very strongly support the study hypotheses: the skeletal architecture of joints clearly plays a highly significant role in determining the nature of intra-articular fractures. Intra-articular fractures involving the convexity are much more likely to be associated with a concurrent joint dislocation.
authors.affiliation: Department of Orthopaedic Surgery, The Royal Brisbane and Women's Hospital, Brisbane, Australia; University of Queensland School of Medicine, Brisbane, Australia.
authors.forename: R A
authors.initials: RA
authors.lastname: Steer
authors.affiliation: Department of Orthopaedic Surgery, The Royal Brisbane and Women's Hospital, Brisbane, Australia.
authors.forename: S D
authors.initials: SD
authors.lastname: Smith
authors.affiliation: Department of Orthopaedic Surgery, The Royal Brisbane and Women's Hospital, Brisbane, Australia.
authors.forename: A
authors.initials: A
authors.lastname: Lang
authors.affiliation: Musculoskeletal Research Unit, Central Queensland University, Rockhampton, Australia; University of Queensland School of Medicine, Brisbane, Australia; Orthopaedic Research Centre of Australia, Brisbane, Australia.
authors.forename: E
authors.initials: E
authors.lastname: Hohmann
authors.affiliation: Department of Orthopaedic Surgery, The Royal Brisbane and Women's Hospital, Brisbane, Australia; Orthopaedic Research Centre of Australia, Brisbane, Australia. Electronic address: kevin_tetsworth@health.qld.gov.au.
authors.forename: K D
authors.initials: KD
authors.lastname: Tetsworth
mesh_terms: D001696:Biomechanical Phenomena; D006801:Humans; D021621:Imaging, Three-Dimensional; D057072:Intra-Articular Fractures / Q000000981:diagnostic imaging / Q000473:pathology*; D004204:Joint Dislocations / Q000000981:diagnostic imaging / Q000473:pathology*; D007596:Joints / Q000033:anatomy & histology* / Q000503:physiopathology; D011859:Radiography; D012189:Retrospective Studies
keywords: Biomechanics; Intra-articular fractures; Trauma