Bedside ultrasonography by emergency physicians for anterior talofibular ligament injury.

OBJECTIVE: Our objective was to study the accuracy of emergency physician (EP) performed bedside ultrasonography (BUS) in patients with suspected anterior talofibular ligament (ATFL) injury.
MATERIALS AND METHODS: After a 6-h training program, from January to December 2011, an EP used BUS to prospectively evaluate patients presenting to the emergency department (ED) with suspected ATFL injury. Then, patients underwent ankle X-ray and Magnetic Resonance (MR) imaging. Outcome was determined by official radiology reports of the MR imaging. BUS and MR imaging results were compared using Chi-square testing.
RESULTS: Of the 65 enrolled patients, 30 patients were BUS positive. Of these, MR imaging results agreed with the BUS findings in 30 patients. In 35 cases, BUS was negative, and 33 of these were corroborated by MR imaging. The sensitivity, specificity, positive predictive value, negative predictive value, and negative likelihood ratio for BUS were 93.8%, 100%, 100%, 94.3%, and 0.06%, respectively. The diagnostic accuracy of BUS was not statistically different from MR imaging (K = 0.938, P = 0.001).
CONCLUSION: BUS for the diagnosis of ATFL injury is another application of BUS in the ED. EPs can diagnose ATFL injury using BUS with a high degree of accuracy.

INTRODUCTION

Traumatic injury of the ankle is a common reason for patients to visit an emergency department (ED). The evaluation of ankle injury generally consists of taking a history and performing a physical examination, which is frequently complemented with radiography. Generally, this type of evaluation is suitable for the detection of fractures, but it is considerably less suitable for the assessment of ligament lesions.[12] The lateral collateral ligament complex of the ankle comprises the anterior talofibular ligament (ATFL), calcaneofibular ligament, and posterior talofibular ligament. The ATFL originates at the anterior border of the lateral malleolus (LM), and follows an oblique anteromedial course to insert at the lateral surface of the talar neck. It is the weakest of the three lateral ligaments and the most commonly injured ligament of this complex. It is ruptured in 66% of cases of inversion-type injuries.[34] Lateral stress radiography may give some information about the ligament injury of the ankle joint (AJ), but in the acute phase, pain often prevents complete physical examination and the value of ankle X-ray is debatable.[1234] Magnetic resonance (MR) imaging is a more appropriate modality for the demonstration of ligament injury of the AJ, but the high costs and limited availability, as well as the long duration of the examination, have been a major hindrance to a wide application of MR imaging for acute ankle injury. Bedside ultrasonography (BUS) is a modality which is increasingly being used by emergency physicians (EPs) to diagnose and expedite the treatment of patients with blunt trauma, shock, pericardial effusion, pneumothorax, small bowel obstruction, and heart failure.[5678910] Ultrasonography (US) can be performed quickly at the patient's bedside in the ED. In the case of ATFL injury, US performed by a radiologist is 100% sensitive and 50% specific, with a 95% accuracy in acute situations.[11] In this study, we aimed to determine the accuracy of EP-performed BUS in patients with a history of ankle inversion and suspected ATFL injury.

MATERIALS AND METHODS

The Ethics Committee of a local tertiary care government teaching hospital approved our study protocol. An EP underwent 3 h of didactic and 3 h of hands-on training by a radiologist for AJ ultrasound and diagnosis of ATFL injury. ATFL injury was considered to be present at sonography when[1] discontinuity of the ligament and/or[2] a hypoechoic lesion existed at the screening area.

Between January and December 2011, during shifts when one of the trained EPs was working in the ED, patients over 18-year old with an inversion-type ankle injury were approached for participation in the study. Patients with fractures, open wounds in the ankle area, and below the age of 18 years were ineligible for the study. In those granting consent, the EP performed BUS using a Mindray® DC three model ultrasound machine with a 7.5 MHz linear transducer (Mindray Bio-medical Electronics Co., Shenzen, China), and B-mode static views were recorded; this procedure took less than 5 min. The transducer was placed sequentially over the ATFL and parallel to the sole of the foot to assess the tearing of the ligament.

During BUS, the ankle was placed in moderate inversion and plantar flexion to achieve a comfortable position for the patient. In this position, the ATFL is slightly stretched, which affords good visualization. The normal ligaments are depicted as hyperechoic bundles. In the case of ruptured ligaments, the torn ends are seen as a discontinuity of the bundles. Even if the torn ends are not separated, we can still depict the abnormality of the ligament as a hypoechoic lesion [Figure 1]. Ankle X-rays and the MR images of the ankle were obtained in all patients, after physical examination and BUS were completed. Radiologist's official reports of MR images were accepted as the gold standards for this study.

Figure 1

Ultrasound image in transverse plane over anterolateral ankle. Yellow arrow shows a hypoechoic area demonstrating hemorrhage into the anterior talofibular ligament

Data analysis

Sensitivities, specificities, positive predictive values (PPVs), and negative predictive values (NPVs) of BUS were calculated and analyzed using SPSS 15.0® (SPSS, Inc., Chicago, USA) with Chi-square testing and calculation of the kappa statistic for comparing EPs.

RESULTS

During the study period, 65 patients with suspected ATFL injuries were evaluated by the study physicians in our ED, and all 65 (37% female, mean age: 34.03 ± 12.85 years, range: 18-72) agreed to participate in the study. Characteristics of the injured ankles and trauma types are listed in Table 1. Thirty patients had positive BUS findings for ATFL injury. Of these, 30 were corroborated by MR images (true positives), and none were found to be negative [false positive, Table 2]. In 35 cases, BUS was negative for ATFL injury: 33 were determined not to have an ATFL injury (true negatives), whereas two were found to have an ATFL injury by MR imaging reports [false negatives; Table 2]. Results for BUS for diagnosis of ATFL injury are listed in Table 3. The diagnostic accuracy of BUS and MR imaging was not significantly different from each other (K = 0.938, P = 0.001). A receiver operating characteristic curve (ROC) analysis was conducted to show the performance of BUS for the diagnosis of ATFL injury [Figure 2].

Table 1

Characteristics of the injured ankles and trauma types

Table 2

Comparison of magnetic resonance image and bedside ultrasonography findings in the diagnosis of anterior talofibular ligament injury

Table 3

Results for bedside ultrasonography for diagnosis of anterior talofibular ligament injury

Figure 2

Receiver operating curve analysis to find the best performance of bedside ultrasonography. Dotted lines mark confidence intervals

DISCUSSION

EPs have used BUS to evaluate trauma patients since the early 1980s.[12131415] There is a growing body of evidence which suggests that patient care improves when ultrasound is included in the diagnostic workup of multiple trauma patients.[1617] Deployment of ultrasound in the ED could potentially provide critical information about traumatized patients and thereby optimize the patient care. US has been widely used by EPs to diagnose many disease processes accurately at the bedside with high sensitivity and specificity.[56188] Improvements in ultrasound technology and increasing clinical experience with US have led to its common use in situations such as thoracoabdominal trauma, ectopic pregnancy, abdominal aortic aneurysm, pericardial effusion, cardiac arrest, biliary disease, renal tract disease, small bowel obstruction, and procedures such as lumbar puncture, arthrocentesis, and central venous access.[81019] As a result, the frequent presentation of acutely ill or injured patients requiring immediate treatment, means that the EP is in the ideal position to use ultrasound technology at the patient's bedside.

Traumatic injuries of the extremities are one of the most common reasons for patients to visit an ED. The technological development of ultrasound equipment and the availability of high-frequency electronic transducers allow accurate evaluation of the ankle.[2021] As a result, our study is one of the first studies to show the accuracy of the EP when performing BUS to evaluate the ankle. Previous studies of US performed by radiologists have demonstrated a sensitivity of 100% and a specificity of 50% with an overall accuracy of 95%.[11] The results of our study suggest that the accuracy of BUS performed by EPs trained in ankle US is comparable to radiologist-performed US and this was well correlated in the previous study as well. To our knowledge, this is the first study to assess the accuracy of BUS when performed by EPs, trained in the performance and interpretation of BUS for AJs. We found that our results were closely correlated with this study as well as with US performed by a musculoskeletal radiologist in another study.

One of the limitations of our study was that EP was not blinded to the clinics of the patients. Since the EPs knew that they were being evaluated, they were more motivated to enhance their performance with regard to the criteria being studied. Because no standards exist for training EPs in BUS for AJ evaluation, we cannot assume that our training program was adequate. Further research needs to be performed to validate our suggested BUS for ATFL injury.

In conclusion, emergency BUS for AJ evaluation has the potential to improve time to diagnosis and early prompt care of patients with ankle trauma. Our study shows that EPs can perform BUS for ATFL injury in the ED with a high degree of accuracy.