Laboratory Studies
Laboratory studies are not indicated during the workup of UCL injuries.
Imaging Studies
Radiography
Findings from routine radiography can occasionally be diagnostic if an avulsion fragment is seen, and in a minority of patients, this study can also reveal secondary findings that are suggestive of UCL injury, such as ossification of the ligament. Plain radiographs are also helpful to rule out other causes of elbow pain, such as epitrochlear osteophytes, epicondylar fractures, posterior olecranon fossa loose bodies, ligamentous calcification, or capitellar lesions. [8]
Manual or instrumented valgus stress radiography can be used to document increased joint opening and ligamentous laxity. Significant asymmetry may be observed in traumatic elbow injuries such as dislocations, whereas laxity in a throwing athlete may not be so obvious, with only a very subtle asymmetry.
Gravity stress radiography—with the patient supine, the shoulder in maximal external rotation, and the weight of the forearm resisted by the UCL—may also be helpful. [9]
Plain arthrography
This imaging modality is not indicated because dye leak has been shown to be inconsistent in cases of chronic laxity, and only an acute event may be anticipated to exhibit a positive finding.
Magnetic resonance imaging (MRI)
Plain MRI is a useful study; however, because of the relatively small size of the UCL, the overall sensitivity of MRI is 57-79% [10]
MR arthrography
This is the most useful imaging modality, with a sensitivity of 97% for UCL injury, and can provide detailed definition of the UCL and associated injuries. [11] Partial-thickness tears can be differentiated from complete tears with MR arthrography. Partial tears demonstrate high signal intensity in the ligament and may show disruption of some fibers, and full-thickness tears are often seen either in the middle of the UCL or at either the distal attachment on the coronoid or at the origin at the medial epicondyle. [12]
Ultrasonography
This modality allows for rapid evaluation of the UCL. A ruptured UCL on an ultrasound appears as a discontinuity of the ligament with fluid in the gap between ends or as nonvisualization of the ligament. Sprains appear as thickening, decreased echogenicity of the ligament, and/or edema when compared with the normal ligament. [13]
Computed tomography scanning (CT) with intra-articular contrast
This technique has been studied in small numbers of patients. CT scanning with intra-articular contrast appears to be highly sensitive and specific for both acute and chronic injuries, [10] but more data are needed before widespread use can be recommended.
Procedures
Arthroscopy is believed by some authors to be the most specific diagnostic procedure because it allows visualization of the medial compartment while valgus stress is applied; however, clinical suspicion of a UCL injury via a good history and physical examination is probably the most reliable in making the diagnosis.
