Diagnostic Approaches for Snapping Elbow

Primary Alternative: MRI Elbow

The American College of Radiology recommends MRI without IV contrast as the most appropriate alternative imaging modality when dynamic ultrasound is unavailable or contraindicated for evaluating snapping elbow, with a focus on T2-weighted MR neurography for ulnar nerve pathology 1
T2-weighted MR neurography is the reference standard for imaging ulnar nerve entrapment, demonstrating high signal intensity and nerve enlargement as the most common findings, with diagnostic confidence increasing with diffusion-tensor imaging 2
MRI evaluates radial nerve, median nerve, and other entrapment syndromes comprehensively, but static MRI may miss dynamic pathology that causes snapping symptoms, particularly ulnar nerve dislocation and snapping triceps syndrome that occur only with elbow movement 2

CT axial images in flexion and extension can demonstrate recurrent ulnar nerve dislocation caused by snapping of the medial head of the triceps, and should be considered when dynamic pathology is suspected but ultrasound is unavailable, or when bony abnormalities need evaluation alongside soft tissue assessment 1
The American College of Radiology suggests considering CT when MRI is contraindicated, such as in patients with pacemakers, severe claustrophobia, or metallic implants 1

Dynamic ultrasound has a sensitivity of 96% and specificity of 81% for detecting ulnar nerve dislocation and snapping triceps syndrome, and accurately demonstrates hourglass constriction of the nerve and nerve dislocation in real-time 1
MRI has high accuracy for static nerve pathology but cannot assess dynamic instability during movement, and is superior for detecting nerve signal changes, enlargement, and associated soft tissue edema 2

MR arthrography at 3T is more accurate than standard MRI for detecting collateral ligament injuries if ligamentous pathology contributes to snapping, and should be considered when mechanical symptoms suggest intra-articular pathology beyond nerve instability 1
Shear-wave elastography (ultrasound-based) has 100% specificity, sensitivity, and positive/negative predictive value reported for ulnar neuropathy at the elbow, and is a newer method that may be available if standard dynamic ultrasound is not 1

The American College of Radiology recommends plain radiographs first to rule out bony abnormalities, fractures, or heterotopic ossification, followed by MRI elbow without IV contrast as the primary alternative for comprehensive soft tissue evaluation if dynamic ultrasound is unavailable 1, 2
If MRI is non-diagnostic, CT in flexion and extension should be considered to capture dynamic ulnar nerve dislocation, or referral to a facility with dynamic ultrasound capability if symptoms persist despite negative static imaging 1