Assessment of Accuracy of Ultrasonography in Diagnosis of Non-osseous Lateral Ankle Instability in Comparison With Magnetic Resonance Imaging

Chronic ankle instability (CAI) is a condition that often develops after repeated ankle sprains, increasing the susceptibility of the ankle to move into excessive inversion when walking on unsteady surfaces. Approximately 74% of acute ankle sprains result in persistent symptoms, 30% of which progress to chronic ankle instability. Arthroscopic examination and magnetic resonance imaging (MRI) are considered the two most accurate methods of diagnosing injuries to lateral collateral ligaments. Ultrasound has been proven able to detect soft tissue injuries, However, the use of ultrasound and its' ability to accurately diagnose CAI is still under debate. The aim of this study is to investigate the diagnostic accuracy of ultrasonography for the assessment of non-osseous lateral ankle instability in comparison with magnetic resonance imaging (MRI).

Chronic ankle instability (CAI) is a condition that often develops after repeated ankle sprains, increasing the susceptibility of the ankle to move into excessive inversion when walking on unsteady surfaces. Approximately 74% of acute ankle sprains result in persistent symptoms, 30% of which progress to chronic ankle instability.\[1-3\] CAI is diagnosed in individuals who report pain and tenderness on the lateral aspect of the ankle, or persistent swelling and discomfort for greater than six months with a history of re-injury or clinical instability of the ankle joint.\[4, 5\] The primary cause of damage to the structural stability of the ankle joint is trauma by forced inversion and plantarflexion. The lateral collateral ligaments, which are more commonly affected by acute sprains, include the anterior talofibular ligament (ATFL), the calcaneofibular ligament (CFL), and the posterior talofibular ligament (PTFL). The ATFL is primarily responsible for preventing excessive supination and anterior translation, while also restricting plantar flexion and internal rotation.

Common diagnostic tools used to identify ankle instability include clinical testing (like Anterior Drawer Test), imaging and arthroscopy. Arthroscopic examination and magnetic resonance imaging (MRI) are considered the two most accurate methods of diagnosing injuries to lateral collateral ligaments. \[7\] In a retrospective study conducted by Joshy et al., in which 24 patients underwent arthroscopy and MRI of the ankle, MRI was found to have both high specificity (100%) and high sensitivity (100%) for ATFL disruption. \[8-10\] Ultrasound has been proven able to detect soft tissue injuries, and has even become the gold standard for the detection of injuries to the patellar and Achilles tendons. \[2, 11\] However, the use of ultrasound and its' ability to accurately diagnose CAI is still under debate.

When imaging the ankle, ultrasound should be able to detect synovial lesions, ligamentous injury, and distinguish soft tissue from osseous impingement.\[8\] Dynamic ultrasound should be also used to discover dislocation of the peroneal tendons, or intra-sheath dislocation, which is indicated by an intact retinaculum with subluxation of the peroneal tendons within the groove.\[11\] Aim of the work: The aim of this study is to investigate the diagnostic accuracy of ultrasonography for the assessment of non-osseous lateral ankle instability in comparison with magnetic resonance imaging (MRI).

Patients and Methods:

fifty four patients complaining of acute or chronic lateral ankle instability will be included in this study.

Inclusion criteria:

Patients complaining of acute or chronic lateral ankle instability.

Exclusion criteria:

* Previous ankle surgery
* Interventional intra-articular procedures (previous arthroscope, injections)
* Systemic inflammatory disorders (collagen diseases)
* Diagnosed osseous lesions.

Methods:

All patients will be subjected to:

Thorough history taking and clinical provisional diagnosis. Plain X-ray of the affected ankle in AP and lateral views to exclude any osseous lesions.

Real-time high resolution ultrasonography of the affected ankle joint MRI for the affected ankle joint.

Ultrasound Technique:

The ultrasonographic examination of the ankle begins with the patient in supine position. Longitudinal scanning of the ankle was first performed to get an overall view of the tibio-talar joint and to detect joint effusion. Thereafter, slight inversion of the foot is performed while the patient in the same position to examine the lateral collateral ligaments and peroneal tendons. The Anterior talo-fibular ligament (ATFL) is first examined in oblique transverse plane from the tip of lateral malleolus, antero-medially and slightly downward, till the talus. Then, the Calcaneo Fibular ligament (CFL) is examined in oblique longitudinal plane from the lateral malleolar tip downward and slightly backward to the lateral surface of the calcaneus.

Regarding the peroneal tendons, they are examined from their supra-malleolar musculo-tendinous junction, and then just behind the lateral malleolus till their infra-malleolar course in both longitudinal and transverse planes.

MRI examination All patients will have MRI imaging of the affected ankle(s) on a high field-strength scanners.

Positioning:

Every patient lies supine with the ankle and foot in neutral position and plantar flexion of 20-30 degrees for reducing the "magic angle" artifact. No movement allowed during examination by supporting the ankle using pads.

Protocol:

The patients are examined by different pulse sequences including T1, T2, proton density, gradient echo and STIR. The examinations will be done in different planes.

Our usual protocol of examination is Sagittal T1WIs, Axial T1WIs T2WIs and proton density images, coronal T1WIs as well as Sagittal or coronal STIR.

Other parameters applied include slice thickness ranged from 3 to 5 mm, matrix 256/192 or 512/224, number of excitation 2 to 3 and field of view ranged from 12 to 16 cm, better kept \<14 cm.

Eligibility Criteria:
Inclusion Criteria:

* Patients complaining of acute or chronic lateral ankle pain and instability.

Exclusion Criteria:

* Previous ankle surgery
* Interventional intra-articular procedures (previous arthroscope, injections)
* Systemic inflammatory disorders (collagen diseases)
* Diagnosed osseous lesion