title: A cadaver model that investigates irreducible metacarpophalangeal joint dislocation.
abstract: OBJECTIVE
  Controversy exists over the pathologic anatomy of irreducible dorsal metacarpophalangeal (MCP) dislocation. The aim of this work is to develop a cadaveric model of MCP joint dislocation that closely simulates the clinical situation and to study the structures around the MCP joint and their contribution to irreducibility of the dislocation.
  
  
  METHODS
  Nine fresh-frozen cadaveric specimens were amputated at the radiocarpal joint and stabilized in a specially formulated fixture. The dislocation was created by an impact load delivered by a servohydraulic testing machine, at a displacement rate of 1000 mm/s and with a maximum displacement of 60 mm. An irreducible dislocation was successfully created in 6 index fingers. An attempt at closed reduction was followed by a dissection of the dislocated joint.
  
  
  RESULTS
  In the 6 examined specimens, the flexor tendons were ulnar to the joint in all cases, the radial digital nerve was superficial (5 cases) or radial (5 cases) to the metacarpal head, and the lumbrical was usually radial (5 of 6 cases) to the joint. Division of the superficial transverse metacarpal ligaments, natatory ligaments, flexor tendons, or lumbricals does not aid reduction of the dislocation. Division of the volar plate was necessary for reduction of the dislocation in all 6 cases, whereas division of the deep transverse metacarpal ligaments does not allow reduction of the dislocation.
  
  
  CONCLUSIONS
  We present a model for creating an irreducible MCP joint dislocation using an impact load that simulates the clinical situation. The volar plate is the primary structure preventing reduction of the dislocation. Division of the deep transverse metacarpal ligament is not effective in reducing the dislocation. The flexor tendons, lumbricals, superficial transverse metacarpal ligament and natatory ligaments do not contribute to irreducibility. The anatomy of the structures surrounding the MCP joint is variable, and careful dissection to prevent iatrogenic injuries is mandatory.
authors.affiliation: Department of Plastic Surgery, Cleveland Clinic, Cleveland, OH, USA. ahafifi@yahoo.com
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Afifi
authors.forename: Amanda
authors.initials: A
authors.lastname: Medoro
authors.forename: Christina
authors.initials: C
authors.lastname: Salas
authors.forename: Mahmoud Reda
authors.initials: MR
authors.lastname: Taha
authors.forename: Tahseen
authors.initials: T
authors.lastname: Cheema
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D004204:Joint Dislocations / Q000473:pathology* / Q000601:surgery; D008023:Ligaments, Articular / Q000293:injuries / Q000473:pathology / Q000601:surgery; D008297:Male; D008662:Metacarpophalangeal Joint / Q000293:injuries* / Q000473:pathology / Q000601:surgery; D008875:Middle Aged; D008953:Models, Anatomic; D053401:Palmar Plate / Q000473:pathology / Q000601:surgery