From the Guidelines
Diagnosing an elbow dislocation on X-ray requires a systematic evaluation of radiographic images, including anteroposterior (AP) and lateral views, to identify disruption of the normal articulation between the distal humerus and the proximal radius and ulna. According to the most recent guidelines from the Journal of the American College of Radiology 1, conventional radiographs are often the first-imaging modality used to exclude a fracture or dislocation. On a lateral view, the coronoid process of the ulna should normally sit in the coronoid fossa of the humerus, and the radial head should articulate with the capitellum. In a posterior dislocation (most common type), the olecranon is displaced posteriorly relative to the humerus.
Some key findings to look for on X-ray include:
- Disruption of the normal articulation between the distal humerus and the proximal radius and ulna
- Joint effusion, which can be identified by the presence of posterior and anterior fat pad elevation 1
- Fat pad signs, particularly the posterior fat pad, which is always abnormal when visible
- Associated fractures, such as coronoid process, radial head, or medial epicondyle fractures, which occur in approximately 10-20% of cases and may affect management
It is essential to compare the affected elbow with the contralateral elbow if available and look for subtle dislocations or subluxations. After identifying a dislocation, carefully assess for associated fractures, as they may require additional management. CT imaging may be necessary for complex cases or when fractures are suspected but not clearly visible on plain radiographs, as recommended by the American College of Radiology 1.
From the Research
Diagnosis of Elbow Dislocation on X-ray
- Elbow dislocations can be diagnosed on X-ray, and the initial assessment typically involves radiographic evaluation 2.
- A complete series of radiographs is typically used to evaluate the elbow and assist in preoperative planning 3.
- X-ray can help identify associated bone injuries, such as radial head fractures or coronoid fractures, which can occur in conjunction with elbow dislocations 3, 4.
- While X-ray is useful for diagnosing elbow dislocations, other imaging modalities like MRI can provide additional information on ligament tears and soft tissue injuries 4.
- MRI can help identify specific ligament tears, such as lateral ulnar collateral ligament (LUCL) tears, radial collateral ligament (RCL) tears, annular ligament (AL) tears, and ulnar collateral ligament (UCL) tears, which can inform surgical decision-making 4.
Limitations of X-ray in Diagnosing Elbow Dislocation
- X-ray may not provide detailed information on soft tissue injuries, such as ligament tears, which can be important for determining the appropriate treatment approach 4.
- MRI is more sensitive than X-ray for detecting ligament tears and other soft tissue injuries, and can provide valuable information for preoperative planning 4.
- The diagnosis of elbow dislocation on X-ray should be complemented with a thorough clinical evaluation, including a complete neurovascular examination and assessment of the entire involved upper extremity 5.