title: Appearance of the weight-bearing lateral radiograph in retrocalcaneal bursitis.
abstract: OBJECTIVE
  A retrocalcaneal bursitis is caused by repetitive impingement of the bursa between the Achilles tendon and the posterosuperior calcaneus. The bursa is situated in the posteroinferior corner of Kager's triangle (retrocalcaneal recess), which is a radiolucency with sharp borders on the lateral radiograph of the ankle. If there is inflammation, the fluid-filled bursa is less radiolucent, making it difficult to delineate the retrocalcaneal recess. We assessed whether the radiographic appearance of the retrocalcaneal recess on plain digital (filmless) radiographs could be used in the diagnosis of a retrocalcaneal bursitis.
  
  
  METHODS
  Whether or not there was obliteration of the retrocalcaneal recess (yes/no) on 74 digital weight-bearing lateral radiographs of the ankle was independently assessed by 2 observers. The radiographs were from 24 patients (25 heels) with retrocalcaneal bursitis (confirmed on endoscopic calcaneoplasty); the control group consisted of 50 patients (59 heels).
  
  
  RESULTS
  The sensitivity of the test was 83% for observer 1 and 79% for observer 2. Specificity was 100% and 98%, respectively. The kappa value of the interobserver reliability test was 0.86. For observer 1, intraobserver reliability was 0.96 and for observer 2 it was 0.92.
  
  
  CONCLUSIONS
  On digital weight-bearing lateral radiographs of a retrocalcaneal bursitis, the retrocalcaneal recess has a typical appearance.
authors.affiliation: Department of Orthopaedic Surgery,Academic Medical Center, University of Amsterdam, the Netherlands. m.n.vansterkenburg@amc.uva.nl
authors.forename: Maayke N
authors.initials: MN
authors.lastname: van Sterkenburg
authors.forename: Bart
authors.initials: B
authors.lastname: Muller
authors.forename: Mario
authors.initials: M
authors.lastname: Maas
authors.forename: Inger N
authors.initials: IN
authors.lastname: Sierevelt
authors.forename: C Niek
authors.initials: CN
authors.lastname: van Dijk
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002062:Bursitis / Q000000981:diagnostic imaging*; D002111:Calcaneus / Q000000981:diagnostic imaging*; D006801:Humans; D008875:Middle Aged; D015588:Observer Variation; D011859:Radiography; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016474:Weight-Bearing; D055815:Young Adult
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