The Influence of Ankle Position on Radiographic Diagnosis of Acute Achilles Tendon Rupture.

No previous study has demonstrated the relationship between the ankle position and radiographic diagnosis of acute Achilles tendon rupture. The purpose of this study was to investigate the influence of ankle position in the presence of diagnostic radiographic signs in acute Achilles tendon rupture. A retrospective review of 154 ankle lateral radiographs of acute Achilles tendon rupture was performed. Ankle position was classified as dorsiflexion, neutral, or plantar flexion by measurement of the tibiotalar angle. Kager's triangle, Toygar's angle, Arner's sign, and thickening of the Achilles tendon were assessed as diagnostic radiographic signs, and their relations to ankle position were analyzed. Interobserver reliabilities of radiographic signs were moderate to substantial (kappa value, range 0.41-0.68). All 4 signs were significantly more visible in ankle plantar flexion than dorsiflexion. The presence of Toygar's angle and positive Arner's sign were significantly increased in ankle plantar flexion compared to neutral, while the presence of Kager's triangle, and thickening of the Achilles tendon did not differ according to ankle position. The diagnostic radiographic signs of acute Achilles tendon rupture were better presented in ankle plantar flexion position than neutral and dorsiflexion positions. Neutral and dorsiflexion ankle positions should be avoided when performing lateral radiographs of patients with suspected acute Achilles tendon rupture.