Diagnostic accuracy of high-resolution ultrasonography in acute ankle ligament injuries

Authors

Abstract

Aim This study aimed to investigate the diagnostic accuracy of ultrasonography in diagnosing lateral ankle ligament ruptures in patients with acute ankle trauma, comparing it with magnetic resonance imaging (MRI).
Materials and Methods Twenty-five patients with acute ankle trauma were included in the study. All patients underwent ultrasonography with a high-resolution linear probe (13 MHz) and a 1.5 Tesla MRI examination. Anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and anterior inferior tibiofibular ligament (AITFL) were evaluated. Ultrasonographic findings were compared with MRI findings, and diagnostic accuracy parameters were calculated.
Results The study found that ultrasonography demonstrated high sensitivity and specificity in diagnosing ankle ligament injuries. Specifically, 17 of the 18 ATFL ruptures diagnosed by MRI were confirmed by ultrasonography, with a sensitivity of 94% and specificity of 100%. All five CFL ruptures and both AITFL ruptures were correctly diagnosed by ultrasonography. The most frequently injured ligament was the ATFL (72%), followed by the CFL (20%) and the AITFL (8%). Multiple ligament injuries were detected in six patients.
Discussion High-resolution ultrasound demonstrates high diagnostic performance in detecting acute ankle ligament injuries. With reported sensitivities reaching 94% and specificities of 100%, which are comparable to those of MRI, ultrasonography emerges as a promising first-line imaging tool in acute ankle trauma. Its lower cost, rapid application, and wide availability not only make it a potential alternative to MRI but also offer significant cost savings.

Keywords

Introduction

Ankle injuries account for nearly 10% of all presentations to emergency departments and are recognized as the most common type of sports-related injury [1, 2]. Most cases result from an inversion mechanism that involves the lateral collateral ligament complex, which includes the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and posterior talofibular ligament (PTFL) [3, 4].
The most frequently injured ligament is ATFL, followed by CFL and the anterior inferior tibiofibular ligament (AITFL) [5, 6]. Trauma can cause simple stretching, partial tear, or complete rupture. Accurate determination of injury severity is critically important for effective treatment planning [7, 8].
Traditional diagnosis relies on physical examination, routine radiographs, and stress radiographs. However, these methods cannot directly visualize injured ligaments and have limited diagnostic value [9, 10]. During acute periods, the reliability of physical examination decreases due to pain and edema [11, 12]. Magnetic resonance imaging (MRI) is the gold standard for evaluating ankle ligament injuries due to its superior capabilities for imaging soft tissue [13, 14]. Recent technological advances in ultrasonographic equipment and high-resolution probes (≥10 MHz) have enabled the visualization of the lateral collateral ligament of the ankle [15, 16].
Recent studies demonstrate high ultrasonographic sensitivity and specificity for ankle ligament ruptures [17, 18]. Kocsis et al.’s 2024 meta-analysis showed that ultrasonography and MRI provide similar diagnostic accuracy in evaluating acute lateral ankle ligament injuries, supporting the role of ultrasound as an alternative imaging method [1].

Materials and Methods

Study Design and Participants
This prospective comparative study was conducted between January 2011 and December 2011. Twenty-five patients aged 18-65 years who presented to our emergency department with acute ankle trauma were included. Inclusion criteria were: acute inversion-type ankle sprain within the last 7 days, clinical suspicion of lateral ligament injury, and ability to provide informed consent. Exclusion criteria included: previous ankle surgery, chronic ankle instability, fractures detected on plain radiographs, pregnancy, and contraindications to MRI. This article is derived from the specialty thesis of Dr. Ali Uludağ, conducted as part of his residency training in Radiology.
Imaging Protocols
All patients underwent both ultrasonography and MRI within 7 days of trauma. Ultrasonographic examinations were performed using a high-resolution linear probe (13 MHz), specifically designed for musculoskeletal imaging, by two independent radiologists (with 4 and 10 years of musculoskeletal ultrasound experience, respectively). The readers were blinded to MRI results and to each other. In cases of disagreement, a senior radiologist adjudicated the final decision. MRI examinations were performed using a 1.5 Tesla scanner with a dedicated ankle coil, and the results were read in a blinded manner compared to US findings.
For ultrasonographic assessment, subjects lay supine with the ankle maintained in a neutral position. The anterior talofibular ligament (ATFL) was imaged axially at the lateral malleolus, the calcaneofibular ligament (CFL) was evaluated coronally behind the lateral malleolus, and the anterior inferior tibiofibular ligament (AITFL) was visualized axially at the syndesmosis. Dynamic evaluations were conducted using stress maneuvers, including the anterior drawer and inversion tests.
MRI protocol included T1-weighted, T2-weighted, and STIR sequences in axial, coronal, and sagittal planes. The time interval between US and MRI was 24-48 hours.
Statistical Analysis
Diagnostic parameters—sensitivity (the proportion of true positives that are correctly identified), specificity (the proportion of true negatives that are correctly identified), PPV (positive predictive value, the proportion of positive test results that are true positives), and NPV (negative predictive value, the proportion of negative test results that are true negatives)—were computed with 95% confidence intervals (CI), taking MRI as the gold standard [19]. Confidence intervals were derived using the Clopper-Pearson method [20], while agreement between observers was evaluated using Cohen’s kappa statistic [21]. Comparisons of paired diagnostic outcomes were conducted with the McNemar test [22]. Receiver operating characteristic (ROC) curve analysis was used to evaluate diagnostic performance [23]. Statistical analyses were performed with SPSS version 25.0, and a p-value <0.05 was considered statistically significant.
For language editing, table formatting, and verification of academic writing standards, ChatGPT 5.0 (OpenAI) was utilized. The tool was employed solely for editorial support and did not influence the study design, data analysis, or interpretation.
Ethical Approval
This study was approved by the Ethics Committee of Sağlık Bilimleri University Taksim Training and Research Hospital (Date: 2010-11-29, No: 747985).

Results

Study Flow and Patient Characteristics
Twenty-five patients (14 male, 11 female) were included in the study with a mean age of 28.4 ± 8.2 years (Table 1). The mean time from trauma to presentation was 4.2 ± 2.1 days. All patients had acute inversion-type ankle sprains with lateral ankle swelling present in all cases (Table 1).
Ligament-Specific Diagnostic Performance
MRI diagnosed ATFL rupture in 18 of 25 patients (72%). Ultrasonography confirmed the diagnosis of rupture in 17 of the 18 patients, with a sensitivity of 94.4% and a specificity of 100% (Table 2). All five CFL ruptures and both AITFL ruptures detected by MRI were correctly diagnosed by ultrasonography, achieving 100% sensitivity and specificity for both ligaments (Table 2).
Inter-Observer Agreement
High inter-observer agreement was achieved for all ligaments, with Cohen’s kappa values of 0.92 for ATFL and 1.00 for both CFL and AITFL (Table 3). Overall agreement was 96% for ATFL, 100% for CFL, and 100% for AITFL (Table 3).
ROC Analysis
ROC curve analysis was performed to evaluate the diagnostic performance of ultrasonography (Figure 1). The AUC value for ATFL was calculated as 0.915 (95% CI: 0.915-1.000), indicating high diagnostic accuracy. AUC values for CFL and AITFL were both 1.00, indicating perfect diagnostic performance (Figure 1). Inter-observer agreement between the to radiologists was almost perfect for ATFL=(0.92, 95% CI: 0.78-1.00) and perfect for CFL and AITFL=(0.92, 95% CI: 1.00-1.00).
Agreement Analysis
Bland-Altman analysis was performed to evaluate agreement between ultrasonography and MRI (Figure 2). The mean difference (bias) between the two methods was calculated as 0.04 ± 0.28. Limits of agreement were found to be between -0.51 and +0.59, indicating that the observed limits of agreement were clinically acceptable in this cohort.
Multiple Ligament Injuries
Multiple ligament injuries were detected in 6 patients (24%), with ATFL involvement in all cases. Combined ATFL and CFL rupture was observed in 5 patients (20%), while combined ATFL and AITFL rupture was detected in 1 patient (4%). Isolated ATFL injury occurred in 11 patients (44%), and no injury was detected in 8 patients (32%). Overall performance followed Table 2: ATFL showed one false negative (sensitivity 94.4%), whereas CFL and AITFL had no misclassification in this cohort.
Associated Findings
MRI detected lateral malleolar fracture in 2 patients (8%). One patient with a lateral malleolar fracture had only ATFL rupture, while the other had both ATFL and AITFL ruptures. CFL was intact in both cases. An avulsion fracture at the fibular attachment level was present in 1 patient (4%) with ATFL rupture.

Discussion

This study compared the diagnostic accuracy of high-resolution ultrasonography with MRI in acute ankle ligament injuries, demonstrating the high performance of ultrasonography. Findings support the use of ultrasonography as an alternative imaging method to MRI [1, 8].
Diagnostic Performance
ATFL injury sensitivity (94.4%) and specificity (100%) with ROC analysis support (AUC = 0.915) demonstrate high ultrasonographic diagnostic performance (Figure 1). Results align with the literature, although our values are higher, likely due to the use of standardized protocols and high-resolution probes [7, 24].
The ATFL specificity of 100% reflects the absence of false positive cases. The single false negative involved a partial rupture examined on day 5 post-trauma, where the surrounding edema may have affected visualization.
Bland-Altman analysis revealed clinically acceptable agreement (bias: 0.04 ± 0.28), supporting the interchangeable use of the two methods (Figure 2).
Literature Comparison
In this cohort, ATFL sensitivity reached 94.4% and specificity 100%, findings that are generally consistent with those reported by Kocsis and colleagues in their 2024 meta-analysis [1]. Their pooled analysis documented sensitivity and specificity values of 92% and 94%, respectively, for ultrasonographic evaluation of ATFL injuries.
CFL achieved 100% sensitivity and specificity, consistent with Seok et al.’s 2020 meta-analysis; however, the wide confidence intervals (47.8-100.0%) reflect the small sample size (n = 5) [9]. Advantages of Ultrasonography
Ultrasound offers several advantages over MRI, including greater cost-effectiveness, shorter assessment times (15 minutes compared to 45 minutes), wider accessibility, and dynamic evaluation capabilities with real-time stress testing [6, 11].

Limitations

This study is subject to several limitations. First, the overall sample size was modest (n = 25), which restricted statistical power, particularly for CFL (n = 5) and AITFL (n = 2) injuries, as indicated by the broad confidence intervals. Second, although ultrasonography was interpreted independently by two radiologists, the single-center design may limit the generalizability of the findings. Third, spectrum bias may be present, as only patients with clinical suspicion were included. Finally, the time interval between trauma and imaging (up to 7 days) may have affected diagnostic accuracy.

Conclusion

Our findings suggest that high-resolution ultrasonography may achieve diagnostic performance in acute ankle ligament injuries that is comparable to that of MRI. Sensitivity and specificity results, supported by 95% confidence intervals, highlight its reliability in informing clinical practice. Considering its lower cost, short examination time, broad accessibility, and ability to provide dynamic assessments, ultrasound may represent a potential first-line imaging option. Our results suggest that ultrasonography could serve as an alternative to MRI in selected cases, which may help reduce healthcare expenditures and improve patient management efficiency.

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