The Sonographic Ottawa Foot and Ankle Rules Study (the SOFAR Study)

Introduction: Foot and ankle injuries are common in the Emergency Department (ED). Of those requiring radiographs in accordance with the Ottawa Foot and Ankle Rules, approximately 22% have a fracture. Ultrasound is developing as a tool for emergency musculoskeletal assessment - it is inexpensive and rapid, and visualises soft tissue and bony structures. Methods: This diagnostic cohort study examined if ultrasound could detect acute bony foot and ankle injuries. Ottawa Rules-positive patients over 16 years were eligible. An ultrasound scan (USS) was performed blind to radiograph findings by an ED member. Patient management was according to radiograph. Significant fractures were defined as per the Ottawa Foot and Ankle Rules study group. All radiographic reporting was conducted blind to USS findings. All USS operators received specific 2-day training in musculoskeletal ultrasound. Results: 110 subjects were recruited. 11 had significant radiological fractures, and 10 were seen on ultrasound. The single missed fracture arose due to the operator not scanning proximally enough on the fibula. On rescanning following radiograph review, the fracture was clearly seen. The sensitivity of USS is 90.9% (95% CI 65.7 to 98.3), and the specificity is 90.9% (95% CI 88.1 to 91.7). The positive predictive value is 0.526 (95% CI 0.380 to 0.569). The negative predictive value is 0.989 (95% CI 0.959 to 0.998). The positive likelihood ratio is 10.00 (95% CI 5.526 to 11.901), and the negative likelihood ratio is 0.100 (95% CI 0.018 to 0.389). Conclusion: This pilot study demonstrates that ultrasound shows great promise for the sensitive detection of foot and ankle fractures, thus identifying patients who require radiographic evaluation more efficiently.