Introduction: Achilles tendon rupture (ATR) is a common sports injury, but approximately 20% of acute ATR cases are misdiagnosed as ankle sprains at first presentation. This study aimed to investigate the diagnostic value of lateral ankle radiography in the diagnosis of acute ATR.
Methods: This was a retrospective case-control study in which the lateral ankle radiographs of patients who presented to the emergency department between January 1, 2015 and December 31, 2019 were examined. The study included a total of 154 patients with acute ATR, who underwent lateral ankle radiography at the presentation and were surgically or magnetic resonance imaging (MRI) confirmed to have ATR in our hospital. The lateral ankle radiographs of the patients were examined by 2 clinicians blinded to clinical data for the following 3 findings: Kager's fat pad sign, tibio-first metatarsal angle, and tibiocalcaneal angle. The same procedure was repeated for 308 controls who underwent lateral ankle radiography and were diagnosed with ankle sprain.
Results: Kager's fat pad sign was detected in 133 (86.4%) of the 154 patients with ATR and 26 (8.4%) of the 308 patients in the control group. The Kager's fat pad sign, tibio-first metatarsal angle, and tibiocalcaneal angle sensitivity values for the diagnosis of ATR were 86.4%, 61.7%, and 65.6%, respectively, and their specificity values were 91.6%, 78.9%, and 56.2%, respectively. Interobserver reliability was determined to be good for all 3 radiographic findings.
Conclusion: Clinicians should be particularly aware of Kager's fat pad sign when examining lateral ankle radiographs for ankle injury.
Levels of evidence: Level IV: Case control study.
Keywords: Achilles tendon; ankle; diagnosis; radiography; rupture.