ABSTRACT
We report the case of a 45 year-old woman who presented to the Emergency Department (ED) with ankle pain after an acute inversion injury from a fall. After history and physical exam suggested a potential fracture, point of care (POC) ultrasound was performed at bedside and demonstrated an obvious cortical defect of the distal left fibula, consistent with fracture. Plain film radiographs were then performed, which failed to demonstrate a fracture. Later, the fracture was further characterized as a non-displaced Weber B distal fibular fracture by stress view radiography. This case reviews the evaluation of acute ankle injuries in the ED, and demonstrates the utility of point of care ultrasound. Although not the current standard of care in the evaluation of potential fracture, point of care ultrasound is emerging as a valuable imaging modality capable of supplementing radiography and enhancing detection of fracture.
INTRODUCTION
Ankle injuries are a very common presenting complaint in the emergency department.. If indicated by history and physical exam, plain radiography is currently the standard of care for the evaluation and diagnosis of ankle fracture. However, plain film radiography is not completely sensitive for ankle fracture. Additionally, radiographic imaging necessitates radiation exposure and additional cost. This paper describes the value of bedside ultrasound as a supplemental imaging modality in the evaluation of ankle injuries to aid in making the diagnosis of ankle fracture.
CASE REPORT
A 45-year-old previously healthy woman presented to the ED with a chief complaint of left ankle pain after a fall while roller skating, resulting in an inversion injury to the left ankle. The patient presented approximately 1 hour after the injury. Examination of the left ankle revealed an intact skin barrier and mild edema. There was tenderness to palpation over the distal aspect of the left lateral malleolus and the calcaneofibular and anterior talofibular ligaments. There was mild tenderness over the medial malleolus, and no tenderness to the base of the 5th metatarsal. Sensation was intact over the foot and ankle and the pedal pulses were intact. POC ultrasound was performed in the ED. Longitudinal views of the left distal fibula demonstrated an obvious cortical defect of the left lateral malleolus consistent with fracture (Figure 1). Plain radiographs of the left ankle, foot and lower leg were then obtained, which failed to demonstrate evidence of left fibular fracture (Figure 2). Due to the ultrasound findings suggestive of fracture, stress view radiographs of the left foot, ankle and leg were obtained with orthopedic consultation. These views demonstrated a non-displaced Weber B fracture of the left fibula (Figure 3). Given this diagnosis, the patient was managed with a medical walking boot, Tylenol #3 for pain and outpatient orthopedic follow-up in 2-3 days. At follow-up the recommendation was given by orthopedics to continue use of the walking boot for 4-6 weeks.
DISCUSSION
While ankle injuries are a very common presenting complaint in the ED, only 15% of undifferentiated patients presenting with ankle injury can be expected to have evidence of ankle fracture on plain radiographs1. Therefore, efforts have been made in recent years to rule-out ankle fracture by means other than radiography, most notably through the use of the Ottawa Ankle Rules (OARs). These clinical decision rules have a high sensitivity, but a very low specificity, resulting in a large number of normal radiographs despite positive OAR findings1. .
A 2014 meta-analysis suggested that after normal plain radiography the occult fracture rate may be as high as 24%3.
Previous studies have analyzed cases where ankle fracture was falsely ruled out by clinical exam or plain radiography, but detected by POC ultrasound, with occult fracture rates ranging from 3.51-8.96%4,5,6. More recent studies have found sensitivities of 87.3-100% and specificities of 96.4-99.1% for the evaluation of ankle fracture by ultrasound7,8.
Stress view radiography should be obtained to determine ankle stability, as unstable Type B fractures frequently require surgical fixation.
POC ultrasound can play a critical role in identifying and correctly characterizing ankle fracture.
CONCLUSION
POC ultrasound is an important imaging modality in fracture assessment due to its availability at the patient’s bedside, ease of use, and multiplanar diagnostic capabilities.
Use of ultrasound in Undergraduate Medical Education , Technology , New Uses
