Value of ultrasonography in assessment of recent injury of anterior talofibular ligament in children

Abstract

Introduction

Sprained ankle is a very common injury in children. Proper treatment of ligament injuries enables full recovery. X-ray and US examinations are commonly available diagnostic methods.

Material and methods

Two hundred and six children (113 girls and 93 boys, mean age 10.6) with recent ankle joint sprain (up to 7 days of injury) were subject to a retrospective analysis. All patients underwent an X-ray and US examination of the ankle joint within 7 days of injury. In 19 patients, anterior talofibular ligament reconstruction was conducted.

Results

X-ray failed to visualize a pathology in 129 children (63%); in 24 patients (12%), avulsion fracture of the lateral malleolus was found, and in 36 cases (17%), effusion in the talocrural joint was detected. Ultrasonography failed to visualize a pathology in 19 children (9%); in 60 patients (29%), it showed avulsion fracture of the lateral malleolus involving the attachment of the anterior talofibular ligament (ATFL); in 34 cases (17%), complete ATFL tear was detected, and in 51 patients (25%), partial ATFL injury was found. Other injuries constituted 19%. The surgeries conducted to repair the anterior talofibular ligament (19) confirmed the US/X-ray diagnoses in 100% of cases. Avulsion ATFL injury, i.e. the one that involves the ligament attachment site, is usually found in younger children (median: 8 years of age). Complete ATFL tears (not involving the attachment site) concern older children (median: 14 years of age).

Conclusions

Since X-ray is of limited value in diagnosing ankle joint pathologies in recent sprain injuries in children, soft tissue imaging, i.e. ultrasonography, is the basic examination to assess the ligament complex. Avulsion fractures, which involve the ATFL attachment site and are usually found in younger children, are a consequence of the incomplete ossification and require urgent diagnosis and orthopedic consultation.

Introduction

Ankle joint sprain is a very common and underestimated injury in children⁽¹⁾. The general incidence is approximately 36/10,000 individuals. It is the most common sport-related injury^{(2, 3)}. Sprain injuries are diagnosed in 6% of young people who practice sports⁽²⁾, and the highest risk is associated with the following sports: soccer, rugby, hockey, handball, volleyball, basketball and squash⁽⁴⁾. Most ankle sprain injuries involve the region of the lateral malleolus and its ligament complex (the lateral ligament complex of the ankle joint) which consists of three ligaments: anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL) and posterior talofibular ligament (PTFL). Sprained ankle is a result of the supination movement, i.e. plantar flexion and inversion of the foot⁽⁵⁾. Usually, the anterior talofibular ligament is damaged⁽⁶⁾. This structure is a strong ligament and it is an element of the lateral ligament complex of the ankle joint⁽⁷⁾. It attaches to the distal end of the fibula; the center of the enthesis is localized approximately 10 mm above the apex of the lateral malleolus. The talar enthesis of the ATFL is localized on the lateral surface of the talus bone⁽⁸⁾ (Fig. 1). When the foot is in the anatomic position, the ligament runs nearly horizontally, but in the plantar flexion, the axis of the ligament is nearly parallel to the long axis of the shin bone⁽⁷⁾. An injury to the ligament can concern its fibers (mid-substance complete or partial ligament tear) or the enthesis. In the latter situation, the bony attachment site of the ligament is detached (avulsion fracture of the fibula). Injuries in sprained ankle are assessed by X-ray and ultrasound (US) examinations, both of which are commonly available. The assessment of the degree to which the anterior talofibular ligament is damaged and the evaluation of coexisting injuries are important when planning the treatment. Surgery is indicated, for instance, when the anterior talofibular ligament is torn completely and the patient manifests clinical sings of ankle joint instability or when the ligaments of the ankle joint are damaged with a coexisting osteochondral fracture (e.g. avulsion fracture of the lateral malleolus with the dislocation of an osteochondral fragment in children)⁽³⁾. When untreated, sprain injury can lead to joint instability, early degenerative changes and chronic joint pain. The aim of this paper is to draw attention to the usefulness of the ultrasound examination in the diagnosis of recent sprain injuries of the ankle joint.

Fig. 1.

Anatomical model of the right ankle joint. The course of the anterior talofibular ligament (arrows)

Material and methods

The retrospective analysis involved 206 patients (113 girls and 93 boys) who reported to the trauma outpatient clinic with recent ankle joint sprain. The average age of the patients was 10.6. All of them were instantly examined with X-ray and US (within 7 days of sustaining injury). X-ray examinations were conducted with the use of a Philips Digital Diagnost V.2 system with Eleva Workspot V.2 software. Ultrasound examinations were conducted with the use of a GE Voluson E8 system using linear probes SP10-16D with the frequency of 7–18 MHz and an 11 L-D probe with the frequency of 4–10 MHz.

X-ray examinations of the ankle joint were conducted in three views: A-P, lateral and “mortise view” (used for the assessment of the width of the tibiofibular syndesmosis and for the optimization of the talocrural joint space imaging). Moreover, images of the contralateral ankle were obtained for comparison. X-ray pictures were assessed by four radiologists experienced in diagnosing conditions within the muscoskeletal system.

Ultrasound images were assessed by five radiologists experienced in diagnosing conditions within the muscoskeletal system. The following signs were assessed in each US examination: the presence of fluid/hematoma in the ankle joint, the image of the synovial membrane and the presence of injuries to the ligaments of the ankle joint: anterior and posterior tibiofibular ligament, anterior talofibular ligament, calcaneofibular ligament, medial ligament, Chopart's joint ligaments (talonavicular and bifurcate ligament), as well as tendons of the peroneus muscles, tibialis muscles, extensor and flexor digitorum longus as well as the region of the epiphyseal cartilage of the fibula and the tuberosity of the fifth metatarsal bone. Moreover, bone fragments that could be detached in the mechanism of avulsion were actively searched for.

The severity of ligament injury was assessed on a 3-grade scale. Grade 1 referred to ligament edema/thickening, which results from elastic deformation of its fibers without the loss of their continuity (commonly known as “stretched” ligament; the ligament remains stable and its structure is homogeneous). Grade 2 was defined as injury in which some fibers are torn (edema, blurred fibrillar echotexture, areas of decreased echogenicity). Finally, Grade 3 referred to complete rupture of the ligament (edema and ligament thickening, no evidence of fiber continuity, failure of function in a dynamic examination: ligament stumps or torn fibers move away from each other). A hematoma at the site of the ligament can be present for several days after sustaining injury. Avulsion fracture, i.e. injury involving the attachment site, is a specific type of grade 3 damage. The structure of the ligament itself is usually assessed as normal or as in grade I injuries.

Based on the clinical assessment and imaging findings, 19 patients were scheduled for a surgery to repair the anterior talofibular ligament.

Results

X-ray failed to visualize a pathology in 129 children (63%) (Fig. 2). In 24 patients (12%), avulsion fracture of the lateral malleolus was found (Fig. 3), and in 36 cases (17%), the examinations showed evidence of effusion in the ankle joint or thickening of the soft tissues adjacent to the lateral malleolus (Fig. 4 and 5). The remaining diagnoses constituted 8% of cases (Fig. 2).

Fig. 2.

X-ray findings

Fig. 3.

X-ray picture of the right ankle joint in the mortise view. Avulsion fracture of the apex of the fibular epiphysis. A slight detached bone fragment, separated from the fibular outline, can be seen

Fig. 4.

X-ray picture of the right ankle joint in the AP view. Thickening of the soft tissues adjacent to the lateral malleolus (arrow)

Fig. 5.

X-ray picture of the right ankle joint in the lateral view. Radiological evidence of effusion in the talocrural joint (arrow)

A US examination failed to visualize a pathology in 19 children (9%) (Fig. 6; Fig. 7). In 60 patients (29%), avulsion fracture of the lateral malleolus involving the ATFL enthesis was found (Fig. 6; Fig. 8). In 34 patients (17%), the ATFL was found completely torn (Fig. 9), i.e. the ligament itself was torn (not involving the enthesis). Partial ATFL injury was diagnosed in 51 patients (25%), and other injuries – in 19% of cases (Fig. 6).

Fig. 6.

US findings

Fig. 7.

Ultrasound image of the normal anterior talofibular ligament. The course of the ligament (arrows) and ligament attachment sites (arrowheads). Marked fibrillar structure; stretched in a resting position

Fig. 8.

Avulsion injury of the anterior talofibular ligament at the fibular enthesis. Detached bone fragment (arrow), separated from the fibular enthesis outline. The ligament is thickened; the fibrillar structure is slightly blurred. Bone entheses are marked with arrowheads

Fig. 9.

Ultrasound image of complete tear of the anterior talofibular ligament. Swollen ligament stumps (arrows) bridged by thin scars

The surgeries (19) conducted confirmed the US/X-ray diagnoses in 100% of cases (Fig. 10).

Fig. 10.

Arthroscopic image of complete tear of the anterior talofibular ligament. Ligament stumps (arrowheads)

Based on the data, it can be concluded that avulsion ATFL injuries are usually found in younger children (median: 8 years of age) in whom the ligament entheses are partially chondral attachments. Complete ATFL tears concern older children (median: 14 years of age).

Discussion

In most cases (over 60%), the result of an X-ray examination was normal – no visible structural changes within the joint, which considerably contrasts with the number of normal ultrasound results (9%) (Fig. 2 and 6).

Effusion in the ankle joint or thickened shadow of the soft tissues at the ankle level (Fig. 3) detected in a radiogram should indicate a need for an extended diagnosis.

ATFL injuries, both those of the ligament only and those involving the enthesis (avulsion fractures), accounted for 70% of cases. Some patients with these injuries were scheduled for a surgery.

It must be observed that in 36 patients, avulsion fracture was occult in X-ray, which accounts for 60% of patients with this injury.

The authors are aware that X-ray is not intended for ligament assessment. It merely enables one to make conclusions concerning soft tissue injuries based on the presence of joint effusion or soft tissue thickening.

The sensitivity and specificity of both modalities (X-ray and US) can be compared only with respect to avulsion injuries when a separated bone fragment is visible in an X-ray picture.

	X-ray	US
sensitivity	40%	100%

X-ray examinations helped establish the correct diagnosis in 40% of cases with avulsion injury whereas this value reached 100% for a US examination.

The specificity of both methods in detecting avulsion fractures is as follows:

	X-ray	US
specificity	100%	100%

All patients without avulsion fracture were diagnosed correctly, i.e. they obtained a negative result both in an X-ray and US examination. This means that there were no patients in this population with false positive results.

Ultrasonography is a valuable method to assess avulsion fractures, tiny fractures due to compression injury as well as coexistent soft tissue injuries in the ankle joint⁽⁹⁾. Ultrasound examinations provide clinicians with valuable information for further treatment. Ultrasonography, as an inexpensive, easily available and noninvasive method, can be broadly used particularly in pediatric radiology, and its findings can significantly influence the therapeutic process^{(9, 10)}. The final decision concerning the treatment is made by an orthopedists on the basis of the whole clinical picture, current patient condition and own experience.

Soft tissues can also be assessed in magnetic resonance imaging (MRI). However, it is not used routinely to assess recent sprain injuries of the ankle joint in children because of its limited availability and long duration of scanning. Ultrasonography can be useful in the initial assessment of whether patients need an MRI examination. The literature reports demonstrate that US and MRI are equally sensitive in detecting ligament injuries in the ankle joint⁽¹¹⁾.

Conclusions

1. X-ray and US examinations are used for the assessment of sprain injuries of the ankle joint in children and should be used as complementary tests in the emergency department.

2. A US examination of the ankle joint is characterized by greater sensitivity in assessing avulsion injuries.

3. Ultrasonography should be therefore considered the primary modality for the assessment of ligament injuries in the ankle joint since its findings can change the therapeutic process.

Conflict of interest

Authors do not report any financial or personal links with other persons and organizations, which might affect negatively the content of this publication and/or claim authorship rights to this publication.