Abstract
Objective
This study aimed to evaluate the relationship between chronic ankle instability (CAI) and both the anatomical characteristics of the anterior talofibular ligament (ATFL) and the bony morphometry of its attachment sites on the fibula and talus using MRI.
Methods
A total of 94 patients were included in this retrospective study (44 with CAI, 50 controls). Morphometric parameters including ATFL length, width, thickness, and the ATFL/PTFL angle were measured, along with sagittal and coronal widths of the fibula and talus at ATFL attachment levels.
Results
The ATFL was significantly longer, thinner, and narrower in the CAI group compared to controls (p < 0.001). The ATFL/PTFL angle was also significantly greater in the CAI group (p = 0.007). However, no statistically significant differences were observed in the sagittal or coronal widths of the talus and fibula. ROC analysis revealed that ATFL length had the highest diagnostic performance (AUC = 0.881). Logistic regression identified increased ATFL/PTFL angle and decreased ATFL width and thickness as independent predictors of instability.
Conclusion
While the ligamentous characteristics of the ATFL, particularly its length and angulation, are strongly associated with CAI, the morphometric features of its bony attachment sites do not appear to contribute significantly. The ATFL/PTFL angle may be considered a reliable, indirect MRI marker in the assessment of CAI and should be considered in routine evaluations.
1
Introduction
Among the lateral ankle ligament complex structures—including the anterior talofibular ligament (ATFL), posterior talofibular ligament (PTFL), and calcaneofibular ligament—the ATFL is the most frequently injured , . This is particularly common in athletes following lateral ankle sprains, and a significant proportion of these injuries may progress to chronic ankle instability (CAI), even after appropriate treatment , .
In diagnosing ATFL injuries, in addition to physical examination methods such as the anterior drawer test, conventional imaging methods like stress radiographs can also be utilized . Magnetic resonance imaging (MRI) is also widely used in the diagnosis of CAI. However, ATFL can be difficult to visualize on MRI, and MRI has limited sensitivity in diagnosing CAI , . Several studies in the literature have explored the use of indirect MRI findings to facilitate CAI diagnosis ,,, .
In patients with chronic ankle instability, anatomical measurements of the ATFL—such as its length, width, and thickness—have been investigated and shown to differ significantly from those of healthy controls ,, . Furthermore, it has been proposed that ATFL rupture may be associated with changes in the ATFL/PTFL angle, and studies have found a significant increase in this angle in patients with CAI . However, assessing both the anatomical parameters of the ATFL and the ATFL/PTFL angle requires high-resolution MRI scans, and these measurements are relatively complex. Indirect measurements that are more easily obtainable on MRI and still reflect the status of the ATFL would be clinically valuable; nevertheless, the current literature lacks sufficient studies on this topic.
The aim of this study is to investigate the relationship between CAI and parameters such as ATFL length, thickness, and width, along with the ATFL/PTFL angle and the anatomical measurements obtained from the talus and fibula regions where the ATFL attaches.
2
Patients and methods
This is a retrospective study approved by the local ethics committee. The study included patients who presented to our hospital between January 2018 and December 2024 and were diagnosed with CAI. These patients were examined by an orthopedic surgeon specialized in sports surgery and foot and ankle conditions. CAI was diagnosed on the basis of patient history and confirmed by physical examination (anterior drawer and varus stress tests). MRI was applied exclusively for morphological assessment.
Inclusion criteria: Inclusion criteria: Patients with a history of ankle “giving way” or a sense of instability and multiple ankle sprains affecting daily activities, with a duration of less than 3 months since the last sprain, in whom the diagnosis of CAI was confirmed through physical examination (anterior drawer and varus stress tests). Only patients whose MRI scans demonstrated at least one of the following findings were included: ligament discontinuity, a wavy contour of the ATFL, or periligamentous soft tissue edema.
Exclusion criteria: Inability to perform measurements due to missing or inadequate MRI images, deleted records, or cases in which the ATFL had completely disrupted or dissolved so that the morphological parameters of the ligament could not be measured; history of major trauma or surgery in the ankle region; presence of systemic diseases that may cause anatomical changes in the ankle joint (e.g., inflammatory arthritis, tumors, sequelae of fractures); age under 18 or over 65 years.
Based on these criteria, 44 patients diagnosed with CAI were included as the CAI group. The control group consisted of 50 patients who underwent ankle MRI for reasons unrelated to ligamentous injury, such as nonspecific ankle pain, evaluation of suspected bone marrow edema, or cartilage pathology. All control patients were examined for ankle instability by the same orthopedic surgeon who evaluated the CAI group, and no signs of instability were detected in either physical examination or imaging. The exclusion criteria for the control group were the same as those for the CAI group. All MRI measurements were performed by an experienced orthopedic surgeon specialized in sports surgery and foot and ankle conditions.
2.1
Measurement of soft tissue parameters
All images were acquired using a 1.5 T MRI scanner (Siemens, Germany) with the patients in the supine position and the ankle in a neutral position. Images were transferred to a medical imaging software (DataMed Angora, Ankara, Turkey) for analysis.
The ATFL/PTFL angle was measured as described by Zhang et al. . After identifying both ligaments on the same axial image, the angle between them was recorded as the ATFL/PTFL angle ( Fig. 1 ). The length of the ATFL was measured on the axial image where the ligament appeared most distinct, defined as the distance between its fibular and talar attachment points. The width of the ATFL was measured at the midpoint (thickest region) of the ligament on the same axial image. The thickness of the ATFL was measured on coronal MRI images as the distance between the talus and fibula ( Fig. 1 ).
MRI-based morphometric evaluation of the anterior talofibular ligament (ATFL) and posterior talofibular ligament (PTFL). (a) ATFL length was measured on the axial image as the distance between its fibular and talar attachment points. (b) ATFL width was measured at the midpoint of the ligament on the same axial image. (c) ATFL thickness was assessed on coronal images as the distance between the talus and fibula. (d) The angle between the ATFL and PTFL was measured on the axial image where both ligaments were simultaneously visible.
2.2
Measurement of bony parameters
Fibular sagittal width: On sagittal images, after identifying the fibular attachment of the ATFL, the anteroposterior length of the fibula at that level was measured and recorded. Fibular coronal width: On coronal images, after identifying the ATFL attachment site, the mediolateral width of the fibula at the same level was measured and recorded. Talar sagittal width: After identifying the ATFL attachment site on the talus, the anteroposterior width of the talus at that level was measured and recorded. Talar coronal width: On coronal images, the mediolateral width of the talus at the ATFL attachment level was measured and recorded ( Fig. 2 ).
Bone morphometric measurements at the ATFL attachment level. (a) Fibular coronal width: largest mediolateral dimension of the fibula at the ATFL attachment site on coronal images. (b) Fibular sagittal width: largest anteroposterior dimension of the fibula at the same level on sagittal images. (c) Talar coronal width: largest mediolateral dimension of the talus at the ATFL attachment site on coronal images. (d) Talar sagittal width: largest anteroposterior dimension of the talus at the same level on sagittal images.
3
Results
The mean age in the CAI group was 36.2 ± 13.4 years, while it was 35.8 ± 12.2 years in the control group. The CAI group included 28 female and 16 male patients; the control group had 27 females and 23 males. In the CAI group, instability was observed in the right ankle in 30 patients and in the left ankle in 14 patients. In the control group, measurements were taken from 31 right and 19 left ankles. The mean BMI was 24.0 ± 4.52 in the CAI group and 23.2 ± 4.32 in the control group. There were no statistically significant differences in demographic characteristics between the groups (p > 0.05).
The values for ATFL length, ATFL width, ATFL thickness, ATFL–PTFL angle, fibular sagittal width, fibular coronal width, talar sagittal width, and talar coronal width were compared between the CAI and control groups. In the CAI group, the ATFL was significantly longer, narrower, and thinner compared to the control group (p < 0.001 for all). The ATFL/PTFL angle was also significantly higher in the CAI group than in the control group (p = 0.007). No statistically significant differences were found in the remaining parameters ( Table 1 ).
Table 1
Comparison of morphometric parameters between CAI and control groups.
| Parameter | Group | Mean ± SD | p-value |
|---|---|---|---|
| ATFL Length | CAI | 23.50 ± 2.815 | <.001 |
| Control | 19.62 ± 1.915 | ||
| ATFL Width | CAI | 2.34 ± 0.545 | <.001 |
| Control | 3.60 ± 0.654 | ||
| ATFL Thickness | CAI | 2.01 ± 0.394 | <.001 |
| Control | 3.10 ± 0.683 | ||
| ATFL-PTFL Angle | CAI | 90.82 ± 8.973 | 0.007 |
| Control | 84.87 ± 9.272 | ||
| Fibula Sagittal Width | CAI | 24.25 ± 2.213 | 0.394 |
| Control | 24.66 ± 2.324 | ||
| Fibula Coronal Width | CAI | 20.15 ± 1.631 | 0.514 |
| Control | 20.42 ± 1.863 | ||
| Talus Sagittal Width | CAI | 56.93 ± 1.651 | 0.235 |
| Control | 56.64 ± 1.555 | ||
| Talus Coronal Width | CAI | 36.41 ± 4.070 | 0.345 |
| Control | 35.59 ± 3.755 |
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