![]() ![]() During SUS, the elbow is placed into flexion and the medial UHJ space (width) deep to the mUCL is measured at baseline and under valgus stress to replicate the functional load on the elbow during throwing (Fig. One of the primary benefits of US is the ability to perform dynamic evaluation of mUCL function under stress to gauge ulnohumeral joint (UHJ) laxity related to mUCL insufficiency or tearing. The unique capabilities of US in mUCL evaluation allow for direct visualization of pathology, dynamic assessment of ligament function, and measurement of tissue elasticity. US has been shown to be a low cost, efficient, and non-invasive method to evaluate the mUCL in throwing athletes. The diagnosis is aided by various imaging modalities, including static radiographs, stress radiographs, computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US). On physical exam, patients often have tenderness along the medial elbow at or near the mUCL origin with positive provocative testing, including the moving valgus stress test and milking maneuver. Patients will typically report acute on chronic medial elbow pain or a single episode of sudden onset pain and an associated “pop” after a throw. Diagnosis of mUCL injuries relies on an accurate history and physical exam. The incidence of mUCL injuries is increasing, highlighting the importance of gaining better understanding of mUCL structure and function and improving diagnostic assessment. These injuries most often occur in baseball pitchers but have also been reported in overhead athletes, such as football quarterbacks, javelin throwers, and softball players. Repetitive stress from overhead throwing can lead to chronic overuse injuries of the mUCL and eventual partial or complete tearing. ![]() The medial ulnar collateral ligament (mUCL) of the elbow, specifically the anterior bundle, is the primary passive restraint to valgus stress on the elbow (Fig. Finally, preliminary work suggests that shear wave elastography may be helpful in evaluating the biomechanical properties of the mUCL, but additional research is needed. Currently, an SD of 2.4 mm and an SDD of 1 mm provide the best diagnostic accuracy for mUCL tears requiring surgery. Sonologists should consider how their US techniques compare with published methods and use caution when applying diagnostic criteria outside of those circumstances. US imaging is a powerful and widely accessible tool in the evaluation elbow mUCL injuries. Recent studies have suggested an injured elbow stress delta (SD-change in ulnohumeral joint (UHJ) space with valgus stress) of 2.4 mm and a stress delta difference (SDD-side-side difference in SD) of 1 mm each denote abnormal UHJ laxity due to mUCL injury. Variability exists in terminology, elbow flexion angle, amount of stress applied, and technique of stress testing. Stress US (SUS) can aid in the diagnosis of mUCL tears and may help identify athletes at risk of mUCL injury. Recent Findingsīoth acute and chronic throwing loads in overhead athletes cause the mUCL to become thicker and more lax on stress testing, and these changes tend to revert after a period of prolonged rest. ![]() This review summarizes the literature on sonographic evaluation of the mUCL and outlines recommendations for consistent descriptive terminology, as well as future clinical and research applications. This has resulted in variable and often ambiguous US diagnostic criteria for mUCL injury. Although ultrasound (US) imaging is commonly used to evaluate the elbow medial ulnar collateral ligament (mUCL) in throwing athletes, significant technical heterogeneity exists in the published literature and in practice. ![]()
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