title: The intermetacarpal angle screening test for ulnar-sided carpometacarpal fracture-dislocations.
abstract: OBJECTIVE
  Ulnar-sided carpometacarpal injuries can be difficult to diagnose radiographically. We hypothesized that the resting position of the normal hand during lateral radiography provides a consistent relationship between the rays and that dorsal subluxation of the metacarpal base in fracture-dislocations increases the angle between the uninjured index and long metacarpals and the injured small metacarpal.
  
  
  METHODS
  A control group of 100 consecutive patients with normal hand radiographs and a series of 12 patients with known carpometacarpal fracture-dislocations were examined. Angles between the index and small metacarpal shaft (I-S IMA) and between the long and small metacarpal shaft (L-S IMA) were measured on the lateral hand radiograph.
  
  
  RESULTS
  In the control group, the mean I-S IMA and L-S IMA were both 6°. In the study group, the mean I-S IMA was 18°, and the mean L-S IMA was 16°. Intraobserver and interobserver reliability was good to excellent for both groups, and a statistical difference existed between the normal and study groups. Based on box-plot analysis of normal and abnormal IMAs, a natural dividing line existed at 10°. With this dividing line, the I-S IMA had a sensitivity of 92% and a specificity of 81%, and the L-S IMA had a sensitivity of 83% and a specificity of 84%.
  
  
  CONCLUSIONS
  Both the I-S IMA and the L-S IMA were useful screening measurements on lateral hand radiographs for detection of ulnar-sided carpometacarpal fracture-dislocations. When evaluating posttraumatic ulnar-sided hand pain, advanced imaging should be considered if the I-S IMA or the L-S IMA is greater than 10°.
authors.affiliation: Department of Orthopaedic Surgery, Naval Medical Center San Diego, San Diego, CA 92134-1112, USA. lucas.mcdonald@med.navy.mil
authors.forename: Lucas S
authors.initials: LS
authors.lastname: McDonald
authors.forename: Paul G
authors.initials: PG
authors.lastname: Shupe
authors.forename: Nathan
authors.initials: N
authors.lastname: Hammel
authors.forename: Leo T
authors.initials: LT
authors.lastname: Kroonen
mesh_terms: D000328:Adult; D052737:Carpometacarpal Joints / Q000000981:diagnostic imaging* / Q000293:injuries* / Q000601:surgery; D003937:Diagnosis, Differential; D005260:Female; D051225:Hamate Bone / Q000000981:diagnostic imaging* / Q000293:injuries* / Q000601:surgery; D006230:Hand Injuries / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D057072:Intra-Articular Fractures / Q000000981:diagnostic imaging* / Q000601:surgery; D004204:Joint Dislocations / Q000000981:diagnostic imaging* / Q000601:surgery; D008297:Male; D008403:Mass Screening; D050279:Metacarpal Bones / Q000000981:diagnostic imaging; D012016:Reference Values; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed