Ankle sprains are the most common sport-related acute injuries presented to the emergency department.1 The cost incurred in the emergency department was reported as $1,008 per lateral ankle sprain.2 Residual symptoms have been reported in 72% of those who have sustained an ankle sprain 6 to 18 months after injury.3 Of those who reported residual symptoms, 40% reported at least one moderate to severe symptom, which included: perceived ankle weakness, perceived ankle instability, pain, and swelling. Factors that were associated with moderate to severe symptoms were reinjury of the ankle, activity restriction longer than 1 week, and limited weight-bearing longer than 28 days.3 One year after an acute lateral ankle sprain, up to 33% of patients still experienced pain.4 Those who have sprained their ankle but have no residual symptoms are defined as “copers” using self-assessed disability questionnaires such as the Foot and Ankle Disability Index.5 A high percentage (70%) of patients who suffer multiple ankle sprains after the first initial sprain will go on to develop chronic ankle instability (CAI).6
Tanen et al7 identified 23% of a cohort of more than 500 high school and collegiate athletes had CAI, with half of those having bilateral CAI. Collegiate athletes with CAI suffered more from unilateral than bilateral CAI (57.6% vs 42.4%). Ultimately, those who develop CAI and continue to have long-term issues may develop post-traumatic ankle osteoarthritis.8,9 In a study by Hintermann et al,9 cartilage damage was noted in 66% of ankles with lateral ligament injuries. Currently, most acute lateral ankle sprains are treated nonoperatively, with surgical repair primarily used for patients with chronic and symptomatic ankle joint laxity.10 However, 50% of patients who suffer an ankle sprain do not seek any medical treatment or evaluation.6 It is extremely important for appropriate evaluation, management, and treatment of acute ankle sprains to occur to reduce the possibility of improper healing and decreased function, ultimately leading to CAI.
Patients with CAI and decreased self-reported function have been seen to decrease their step count overall compared to healthy individuals.11 After one single ankle sprain, a significant decrease in physical activity across the lifespan has been seen specifically in mice.12 In older adults with a history of sustaining at least one knee or ankle injury, a negative impact was observed on physical quality of life.13 If an ankle sprain is mistreated at the onset and the individual develops CAI, short-term deficits in function and activity may be seen that may lead to the potential for long-term health and activity effects.11,14
In a systematic review of the functional anatomy, pathomechanics, and pathophysiology of lateral ankle instability, Hertel15 described mechanical instability of the ankle complex as a result of anatomic changes that occur after an initial ankle sprain. He identified the changes that occur as pathologic laxity, impaired arthrokinematics, synovial changes, and potential development of degenerative joint disease. These mechanisms can follow an initial ankle sprain, leading to recurrent ankle injuries and the development of CAI. Pathologic laxity depends on the amount of ligamentous damage to the specific lateral ankle ligaments, whereby pain, symptoms of “giving-way,” and perceived instability may be associated.
After an initial evaluation of the injury occurs, the clinician will grade the injury (I, II, or III) depending on the severity of the injury and the symptoms presented (pain, swelling, and inability to bear weight). Instability of the talocrural joint is caused by damage to the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL).16 Damage to the ATFL is commonly assessed manually or by an instrumented stress using the anterior drawer test, which provides anterior translation of the talus and calcaneus while the tibia and fibula remain stabilized. Damage to the CFL is assessed manually or by an instrumented stress of the talar tilt test, which inverts the rearfoot with the talocrural joint in a dorsiflexed position. Grading typically will occur following manual stress tests, such as the anterior drawer test and talar tilt test. Manual stress tests have been shown to be less reliable in determining stability of the talocrural joint, thus making the clinical decision of injury severity less accurate.17 This can be problematic because understanding the severity of an ankle sprain plays a significant role in the clinician's reasoning for specific rehabilitation protocols and time to return-to-play.
In this review, advanced imaging techniques for identifying talocrural joint laxity in those who are classified as CAI, coper, or acute sprain will be examined. The purpose of this review was to outline the existing evidence regarding imaging methods of determining ankle joint laxity. The specific techniques used in research and clinical settings are stress ultrasonography, stress radiography, and stress magnetic resonance imaging (MRI). The primary aim of this review was to identify the specificity, sensitivity, and accuracy of each method and outline previous research that had used these methods in the CAI population. Our secondary aim was to provide clinical recommendations on the use of these techniques to accurately identify ankle joint laxity in those with a previous ankle sprain.
How to Perform. Stress ultrasonography is performed by using a method of stress to the talocrural and subtalar joints of the ankle. Common stress methods use a Telos stress device (LigMaster; Sport Tech, Inc), placing the ankle into the inversion/talar tilt (Figure 1) and anterior drawer (Figure 2) positions using 150 N of force, or a manual stress provided by the clinician placing the ankle into the talar tilt and anterior drawer test positions. Musculoskeletal ultrasound is performed over the ATFL with a probe taking images with a 12-Hz frequency and 1.5-mm depth. Simple measurements can be taken on the ultrasound unit, using the measuring tool, of the length of the ATFL, in millimeters, between the peak of the talus and the peak fibula in a stressed position (Figures 1–2). These measures have been identified as indicators for CAI and acute injury to have an increased ATFL length in a stressed position.18,19
Common stress method placing the ankle into an inversion/talar tilt test position.
Common stress method placing the ankle into an anterior drawer test position.
Diagnostic Accuracy. In the eight articles that assessed the sensitivity, specificity, and accuracy of stress ultrasonography, the sensitivity ranged between 74% and 100%.20–27 The articles that were assessed used different methods in determining stress, either with a device like the Telos, or manually, which may lead us to a larger range between the studies. The specificity of stress ultrasonography ranged between 38% and 100%, with the majority between 90% and 100%. The accuracy of stress ultrasonography ranged between 84.2% and 100% (Table A, available in the online version of this article). In a recent review by Cao et al,28 the authors determined that in diagnosing chronic ankle injuries, ultrasonography without stress was greater than 90% for sensitivity and specificity.
Reliability, Sensitivity, Specificity, and Accuracy of Ultrasound, Radiograph, and MRI in the Ankle
Six articles used stress ultrasonography, alone or in conjunction with another method, to identify differences in chronically unstable ankles, copers, or those who had sustained acute lateral ankle sprains compared to healthy uninjured ankles (Table B, available in the online version of this article).18,19,21,29–31 To assess the stability of the ATFL, stress was performed in two positions: anterior drawer and talar tilt/inversion tests. Patients in the CAI and/or copers groups demonstrated greater joint laxity in both positions compared to a healthy, uninjured ankle. Those with CAI were included if they experienced chronic ankle pain or laxity for at least 3 months after the last injury.
Advanced Imaging Techniques to Detect Ankle Joint Laxity
As Cai et al32 showed with their examination of ultrasound images, patients with CAI can be divided into six types based on their type of injury to the ATFL. For clinicians, using the ultrasound as a part of the examination process will be useful in understanding the type and severity of injury patients may have. Understanding the type of injury will not only help in the rehabilitation process and return-to-play decision, but also in decision making to refer the patient to a physician or specialist early.
Clinical Recommendation. Stress ultrasonography is accurate in detecting ankle joint laxity in those with CAI. However, the limitation to this method is the experience and knowledge of the clinician using the tool. Although training is required, the overall benefits of identifying the amount of laxity of the joint in patients will aid in the clinicians' decision making in rehabilitation, time to return-to-play, and time to physician referral.
How to Perform. Like stress ultrasonography, the stress is performed manually or by a Telos stress device in the inversion/talar tilt and anterior drawer test positions while a radiograph is completed. The stress and radiographs are performed separately by experienced radiologists and clinicians. Static and stressed radiographs would be taken to determine the translation or ankle joint laxity. Multiple views with a radiograph are necessary to view the inversion/talar tilt and anterior drawer test positions. Precautions must be taken for the patients involved in radiographs due to radiation exposure. Unlike ultrasonography, radiography can help our understanding of bone positioning during these stressed positions. Understanding the position of the talus, for example, may be important in those with CAI because Wikstrom and Hubbard33 noted that the talus is positioned significantly more anterior without stress in an involved CAI limb than an uninvolved CAI limb, which, in turn, limits ankle dorsiflexion.
Diagnostic Accuracy. Two studies assessed these areas for stress radiography and reported sensitivity of 68%, specificity of 71%, and accuracy of 67%.26,27 Lee et al34 also used bilateral manual stress radiographs and found the reliability of this measure in detecting ankle joint laxity in a combined ATFL and CFL injury had an intraclass correlation of 0.51 to 0.91 for interrater and intrarater agreement in talar rotation and anterior talar translation (Table A). Stress radiography was examined in four articles and saw the same increase in ankle joint laxity in both positions for those designated as CAI, coper, or acute sprain29,30,35,36 (Table B). Cho et al29 showed that stress radiography detected a greater percentage of ankle instability during anterior translation than on a manual anterior drawer test.
Clinical Recommendation. Stress radiography can be used to detect ankle joint laxity in those classified as CAI, coper, or acute sprain; however, it has not been used as widely in this population. This method may be a better option for a patient who may have a suspected talar position deviation, which would be difficult to detect on an ultrasound.
How to Perform. The T1 open high-field–strength MRI system (Panorama HFO, Philips Healthcare) is the MRI system previously used by Seebauer et al.37 Coronal, axial, and 45-degree paraxial T2-weighted fast spin-echo images were used for the inversion stress test and sagittal images were used for the anterior drawer test. Inversion/talar tilt stress images were measured with two independent tangent lines by an experienced radiologist: inferior articular surface of the tibia and most proximal talar contour. Subtalar tilt was also measured using the angle between the talus and the calcaneus in the lower ankle joint. In the sagittal plane images, anterior talus translation was measured as the shortest distance between the posterior lip of the distal tibial joint surface and talar dome. Anterior calcaneus translation was also measured as the distance from the upper posterior aspect of the calcaneus to the inferior head of the talus.
Diagnostic Accuracy. To our knowledge, only one study has used a novel stress device during an MRI in this population (Table A). The authors determined the accuracy of this method to be 97%. In patients with CAI and healthy, uninjured individuals, they found significant differences in the two groups in talar tilt, subtalar tilt, anterior talus translation, anterior calcaneus translation, and medial talocalcaneal translation, and a decrease in diameters of CFL and posterior talofibular ligament.37
Clinical Recommendation. Measurement of subtalar joint laxity is important in assessing the stability of the lower ankle joint, especially when considering multiple planes using MRI. Stress MRI offers clear images in the evaluation of mechanically unstable ankles and simultaneous comparison with the upper ankle joint.37 Even though, to date, there has only been one study completed using MRI, this method is accurate in detecting laxity of the ankle joint. Ultimately, the cost and time it would take to complete this evaluation on one patient would be warranted in certain circumstances that require information about the translation of the joint in those two positions.
Overall, each method is accurate in detecting ankle joint laxity in those classified as CAI, copers, or acute sprain; however, the accessibility and cost of each of these methods must be considered. According to Feger et al,38 the average cost is $78 for a complete ankle xray and $1,055 for an MRI per visit/treatment in the United States. Both radiograph and MRI methods must be administered by a lab technician or specialist because training is needed to correctly implement. Ultrasound has been noted to cost $111 per visit/treatment.27 Ultrasound can be easily administered by a clinician and used daily without having to the leave the clinic, and is also less invasive than radiographs and MRI. Ultrasound provides advantages to clinicians, such as dynamic imaging with immediate feedback, noninvasiveness, lower overall cost limiting the number of repeated visits, and quicker scan times. However, a down side of ultrasound in the evaluation of the lateral ankle ligaments is that it is highly operator dependent. The operator must understand the scanning technique, potential pitfalls, and how to recognize a normal versus an injured ligament.39
Stress ultrasonography, radiography, and MRI are all accurate measures in detecting ankle joint laxity in those classified as CAI, copers, and acute sprains. Stress ultrasonography has the highest reported accuracy of the three measures and is one of the lower cost options after an ultrasound unit is purchased. This method is best used on patients who have chronic symptoms, such as repetitive sprains, pain, and swelling, to determine ankle joint laxity and thickness of the ATFL. Stress radiography has moderate accuracy compared to ultrasonography and MRI. This method may be best used when available for patients with CAI who may have a talar position deviation to detect without stress. As Seebauer et al37 described, stress MRI is a reliable method at 97%; however, it is the most cost prohibitive and least used in this population in research. Although there is no consensus on a gold standard for imaging of detecting ankle joint laxity in current research, stress ultrasonography is the most commonly used, whereas radiograph and MRI are less commonly used due to cost, radiation exposure, and limited access and training using the equipment.
In the future, these techniques for detecting ankle joint laxity should be implemented to detect the need for further intervention. Using these techniques can assist clinicians in educating patients and giving them immediate feedback on their current condition. Having access to at least one of these methods would assist in the communication with the entire medical team regarding the diagnosis and treatment process.
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Reliability, Sensitivity, Specificity, and Accuracy of Ultrasound, Radiograph, and MRI in the Ankle
|Research Study||Study Design||Participants||Inclusion Criteria||Measurements||Results|
|Cheng et al20||Prospective||120 ankles in 120 patients||Symptoms present for at least 6 weeks complaining of lateral ankle pain with or without swelling and point tenderness over the lateral portion of the ankle. 75% CAI in preoperative clinical diagnosis||Ultrasonography of the ankle prior to surgery and results compared to operative findings||Sensitivity = 98.9%, Specificity = 96.2%, and accuracy = 84.2% for injury to ATFL and Sensitivity = 93.8%, Specificity = 90.9%, and accuracy = 83.3%for injury to CFL.|
|Croy et al21||Prospective, blinded, diagnostic-accuracy||86 subjects (ankle-injured: n=66, control: n=20)||Ankle-injured: history of lateral ankle sprain from plantar flexion/inversion movement. Control: free from any history of ankle injury or reports of instability||Talocrural joint laxity during anterior drawer test (ADT), talofibular interval using stress ultrasonography||53% of subjects anterior talocrural joint laxity at reference standard of 2.3 mm or greater, 36% at 3.7 mm or greater. Sensitivity of ADT was 0.74 at 2.3 mm or greater, and 0.83 at 3.7 mm or greater. Specificity was 0.38 and 0.40, respectively. Positive likelihood ratios were 0.66 and 0.41, respectively.|
|Guillodo et al22||Diagnostic accuracy||56 CAI patients||After sports-related acute ankle sprain with symptoms present for at least 3 months||ATFL damage by ultrasonography and computed arthrotomography and agreement between the two methods||ATFL damage was detected in 61% by ultrasound and 71% by computed arthrotomography. Agreement was substantial (K = 0.76) for assessing the ATFL.|
|Gün et al23||Prospective, diagnostic-accuracy||65 emergency department patients||Over 18 years old with inversion-type ankle injury (ATFL). ATFL injury was defined at sonography when discontinuity of ligament or hypoechoic lesion exists.||Bedside ultrasonography (BUS), X-ray, Magnetic resonance imaging (MRI) of ATFL injury||BUS: Sensitivity = 93.8%, Specificity = 100%, positive predictive value = 100%, negative predictive value = 94.3%, and negative likelihood ratio = 0.06%. The diagnostic accuracy of BUS was not statistically different from MRI (K = 0.938, P = 0.001)|
|Hua et al24||Prospective, diagnostic-accuracy||83 patients||Authors did not identify. Ultrasound was agreed to by patients with a preoperative diagnosis, where 44% had CAI, and the remaining had different types of chronic ankle diagnoses with pain.||Ultrasound examination for diagnosis of ATFL injury and subsequent ankle arthroscopy for reference||Accuracy for detection of ATFL injury was 95.2%, sensitivity = 97.7%, specificity = 92.3%, positive predictive value = 93.5%, negative predictive value = 97.3%, positive likelihood ratio = 12.7, and negative likelihood ratio = 0.025|
|Lee and Yun25||Prospective, cross-sectional||85 patients||Physically active adults aged 18–40 years with acute ankle sprain, history of ipsilateral recurrent ankle sprain (>3 episodes), ankle instability (anterolateral drawer and talar tilt tests) despite conservative treatment for 6 months, and ankle MRI performed within one month for preoperative evaluation.||Point-of-care ankle ultrasound of ATFL, CFL, ATiFL, deltoid, and Achilles. MRI used as reference standard.||Ultrasound showed acceptable sensitivity (96.4–100%), specificity (95–100%), and accuracy (96.5–100%).|
|Oae et al26||Prospective, diagnostic-accuracy||34 patients||Consecutive patients who needed an operation due to severe problems, except fractures. Acute or chronic injury was identified.||Stress radiography (X-P), ultrasound (US), MRI, and arthroscopy for comparison to determine accuracy of ATFL injury detection||88% showed ATFL injury in the arthroscopy. The diagnosis of ATFL injury with stress X-P, US, MRI were with an accuracy of 67%, 91%, and 97%, respectively. US and MRI had the same location of injury as arthroscopy in 63% and 93%, respectively.|
|van Dijk et al27||Prospective||160 patients||Ages 18 to 40 years of age presented to emergency department within 2 days after acute inversion injury of the ankle||Physical examination within 2 days and 5 days after inversion trauma, arthrography, stress radiography, and ultrasonography||Ultrasound used alone showed 92% sensitivity, 64% specificity, and cost $111. Stress radiographs used alone showed 68% sensitivity, 71% specificity, and cost $78. Numbers decreased when physical exam took place < 48 hours from injury but increased when included with the physical exam 5 days after injury.|
|Lee et al30||Prospective cohort||66 patients||Combined ATFL and CFL injury||Bilateral manual stress radiographs. Anterior talar translation (mm), talar tilt (°), and talar rotation (%) in injured vs uninjured ankles. Intraobserver and interobserver reliability was measured||Ankle stress radiographic intraobserver and interobserver agreement was ICC = 0.91 and 0.82 for talar rotation, ICC = 0.64 and 0.51 for anterior talar translation, and ICC = 0.78 and 0.71 for talar tilt angle, respectively.|
Advanced Imaging Techniques to Detect Ankle Joint Laxity
|Research Study||Study Design||Participants||Inclusion Criteria||Measurements||Results|
|Cho et al29||Retrospective||28 patients||Require surgery with pain or giving way associated with lateral ankle instability resulting in repetitive inversion sprains. Conservative treatment failed to alleviate symptoms for at least 3 months.||Manual anterior drawer test, stress radiography, MRI, and stress ultrasound to assess the ATFL prior to surgery||Grade 3 lateral instability was verified arthroscopically in 100% of cases. 78.6% showed grade III instability on manual anterior drawer test. 86% displayed anterior translation exceeding 5 mm on stress radiography, and 11% talar tilt angle exceeding 15 degrees. Lax and wavy ATFL was evident on stress ultrasound in all cases (100%).|
|Croy et al19||Cohort||25 participants with 27 acute, lateral ankle sprains||Suffered a lateral ankle sprain within 14 days before the baseline visit and agreed to follow-up visits at 3 and 6 weeks from injury||Bilateral stress ultrasound imaging at baseline (<7 days), 3 weeks, 6 weeks from injury in 3 positions: neutral, anterior drawer, and inversion. Talofibular interval (mm) and FAAM-ADL and FAAM-sport||Talofibular interval increased with anterior drawer stress in involved ankle over the uninvolved ankle at baseline. Inversion stress greater interval changes in the involved than the uninvolved ankles. A significant reduction in talofibular interval between baseline and week 3 inversion measurements only.|
|Croy et al18||Cross-sectional||60 ankles (control: n=20, copers: n=20, CAI: n=20)||Control: no history of ankle injury or no reported ankle instability. Coper: history of 1 ankle sprain more than 1 year ago and no residual symptoms of instability of giving way. CAI: reported history of recurrent ankle sprains and reported instability on at least 2 of 5 questions on AII||Ligament length change, Anterior drawer test and end range ankle inversion||Anterior drawer test length changes greater in CAI and copers compared to control. Ankle inversion greater ligament-length change in CAI and copers compared to controls.|
|Croy et al21||Prospective, blinded, diagnostic-accuracy||86 subjects (ankle-injured: n=66, control: n=20)||Ankle-injured: history of lateral ankle sprain from plantar flexion/inversion movement. Control: free from any history of ankle injury or reports of instability||Talocrural joint laxity during anterior drawer test (ADT), talofibular interval||53% of subjects anterior talocrural joint laxity at reference standard of 2.3 mm or greater, 36% at 3.7 mm or greater. Sensitivity of ADT was 0.74 at 2.3 mm or greater, and 0.83 at 3.7 mm or greater. Specificity was 0.38 and 0.40, respectively. Positive likelihood ratios were 0.66 and 0.41, respectively.|
|Lee et al30||Prospective||73 patients||Chronic ankle pain or laxity after remote ankle sprain which was defined with symptoms persisting for at least 3 months after injury.||Standardized physical examination (manual anterior drawer test), stress radiography and stress ultrasonography to assess ATFL||Significant difference for ATFL length (ATFL stress) and ATFL ratio (stress/resting) (p <0.001) between the three groups (Grade I, Grade II, Grade III by anterior drawer test).|
|Mizrahi et al31||Prospective/Retr ospective||54 patients (asymptomatic : n=20, symptomatic: n=34)||Asymptomatic: no history of a sprain, other trauma, or surgery to either ankle. Symptomatic: Clinically evaluated and diagnosed with CAI from history and physical examination by foot and ankle surgeons.||Sonography of the ATFL to determine length in neutral and manual inversion stress positions||Significant increase in mean change in ATFL length (laxity) in the symptomatic group (1.26mm, P<.0001).|
|Hubbard et al8||Cohort||51 subjects||Self-reported unilateral functional ankle instability (FAI) answering “yes” to specific questions on the 11 question questionnaire||Ankle-subtalar joint motion for total anteroposterior (AP) displacement and total inversion-eversion rotation using an instrumented ankle arthrometer. Anterior and lateral stress for anterior displacement and talar tilt using stress radiographs.||Arthrometry of anterior and total AP displacement and radiography of anterior displacement were greater (p < 0.05) in the FAI ankles when compared with uninjured ankles|
|Dowling et al36||Cohort||46 participants (76 ankles)||No history of ankle fracture or surgery for ankle instability or history of previous ankle sprain||Stress radiography of anterior drawer test and talar tilt test||Mean anterior drawer 2.0 ± 1.7 mm and talar tilt 3.4°± 2.7° in the normal ankle.|
|Seebauer et al37||Prospective pilot||50 subjects (72 stable ankles in 37 subjects, 28 ankles in 15 subjects with CAI)||18 years and older and either symptomatic instability of the ankle joint for inclusion in instability group (B) or absence of pathologic findings in the ankle for inclusion in control group (A).||Inversion and anterior drawer test performed under 4 views using MRI to assess talar tilt, subtalar tilt, anterior talus translation, anterior calcaneus translation, medial talocalcaneal translation, and diameters of lateral ankle ligaments||Significant differences between groups A and B (p < 0.05) were found in talar tilt, subtalar tilt, anterior talus translation, anterior calcaneus translation, medial talocalcaneal translation, and decrease in diameters of CFL and PTFL.|