Introduction: Foot and ankle injuries are common in the Emergency Department (ED)1. Of those which require radiographs, in accordance with the Ottawa Foot and Ankle Rules, approximately 22% have a fracture.2 In the last decade ultrasound has been developing as a tool for emergency musculoskeletal assessment – it is inexpensive, rapid and visualises soft tissue and bony structures.
Methods: This diagnostic cohort study was designed to determine whether ultrasound could detect acute bony and non-bony foot and ankle injuries. Ottawa Rules positive patients over 16 year of age without obvious dislocation/compound fracture were eligible. An ultrasound scan (USS) for bony injury was performed by a member of the ED, blinded to radiographic findings. Patient management was determined according to the radiographs. Significant fractures were defined as a breadth greater than 3 mm (as per the Ottawa Foot &
Ankle Rules study group)3. All radiographic reporting was conducted blind to the results of the USS. All USS operators received a specific 2-day training in musculoskeletal ultrasound prior to the trial.
Results: One hundred and ten subjects were recruited. eleven had significant radiological fractures, ten of which were seen on ultrasound. The single missed fracture arose due to the operator not scanning proximally enough on the fibula. On re-scanning following radiographic review the fracture was clearly seen on ultrasound. To date the sensitivity of USS is 90.9%, with 95% CI (65.7, 98.3). The specificity is 90.9% with 95% CI (88.1, 91.7). The positive predictive value is 0.526, with a 95% CI (0.380, 0.569). The negative predictive value is 0.989, with a 95% CI (0.959, 0.998). The positive likelihood ratio is 10.00, with a 95% CI (5.526, 11.901) and the negative likelihood ratio is 0.100, with a 95% CI (0.018, 0.389).
Conclusion: Our pilot study demonstrates that ultrasound shows great promise for the sensitive detection of foot and ankle fractures.
