Stress Ultrasound of the UCL
The ulnar collateral ligament (UCL) is the primary valgus restraint in the elbow (1). The UCL is comprised of the anterior oblique, posterior oblique, and transverse bundle (2,3).
The repetitive valgus stress that occurs across the elbow during throwing can lead to partial and complete tears of the anterior oblique bundle of the UCL (3). Within the anterior oblique bundle, there is an anterior and posterior band and the anterior band is thought to be the valgus stabilizer between 30 and 90 degrees of elbow flexion (3). The anterior band of the anterior oblique bundle of the UCL originates from the medial epicondyle and inserts on the sublime tubercle of the ulna (3).
Diagnostic tests used to evaluate the UCL include magnetic resonance imaging and ultrasound. MRI has been found to be highly sensitive for diagnosis of complete UCL tears (3). However, the sensitivity of an MRI decreases in the diagnosis of partial thickness tears (3). Addition of contrast with the MRI can improve the sensitivity in diagnosis of partial tears, but this does require the patient to first receive a contrast injection (3). Ultrasound is also used in making the diagnosis of a UCL injury. Static measurements and assessment of the UCL can provide information on ligament quality, but the moving valgus stress test (MVST) is a more accurate clinical test (2). A moving valgus stress test will measure joint gapping in both elbows and assess for any difference (4). An increase greater than 1.5mm between an unstressed and stressed elbow typically suggests injury to the ligament (5).
Evaluation of the ulnar collateral ligament is typically assessed with a linear array transducer, but some studies have also used a hockey stick transducer (1).
The patient is typically placed supine and the elbow is placed at thirty degrees of flexion, as this is the angle the UCL acts as the primary valgus restraint (1,4). The shoulder will be placed in external rotation with 45 degrees of abduction (4).
Starting position for UCL evaluation (4)
In order to add valgus stress, an assistant can be used or an attached weight with 150 newtons of force can be added (5). The image below shows an assistant using a handheld dynamometer to apply 5.5lbs of valgus stress to the elbow (8). Then, as noted above, providers will compare the ulnohumeral joint gap of both elbows and compare them to the ulnohumeral joint gap after a valgus stress is applied.
The anterior band of the anterior oblique bundle of the UCL is the primary restraint of valgus stress across the elbow. The band is prone to damage during throwing and injury can lead to a dramatic drop in performance. MRI can help assess full thickness tears, but stress ultrasound can better assess for partial tears. Above, we outlined the process of evaluating the UCL with an ultrasound stress test.
By Gregory Rubin, DO
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1) Atanda, Alfred, et al. “Early Anatomic Changes of the Ulnar Collateral Ligament Identified by Stress Ultrasound of the Elbow in Young Professional Baseball Pitchers.” The American Journal of Sports Medicine, vol. 43, no. 12, Dec. 2015, pp. 2943–49. PubMed, https://doi.org/10.1177/0363546515605042
2) Wigton, Michael D., et al. “The Moving Valgus Stress Test Produces More Ulnar Collateral Ligament Change in Length during Extension than during Flexion: A Biomechanical Study.” Journal of Shoulder and Elbow Surgery, vol. 29, no. 6, June 2020, pp. 1230–35. PubMed, https://doi.org/10.1016/j.jse.2019.12.025
3) Yoshida, Masahito, et al. “Anterior and Posterior Bands of the Anterior Bundle in the Elbow Ulnar Collateral Ligament: Ultrasound Anatomy.” Journal of Shoulder and Elbow Surgery, vol. 26, no. 10, Oct. 2017, pp. 1803–09. PubMed, https://doi.org/10.1016/j.jse.2017.05.025.
4) Park, Jin-Young, et al. “Valgus Stress Ultrasound for Medial Ulnar Collateral Ligament Injuries in Athletes: Is Ultrasound Alone Enough for Diagnosis?” Journal of Shoulder and Elbow Surgery, vol. 29, no. 3, Mar. 2020, pp. 578–86. PubMed, https://doi.org/10.1016/j.jse.2019.12.005.
5) Ciccotti, Michael C., and Michael G. Ciccotti. “Ulnar Collateral Ligament Evaluation and Diagnostics.” Clinics in Sports Medicine, vol. 39, no. 3, July 2020, pp. 503–22. PubMed, https://doi.org/10.1016/j.csm.2020.02.002
6) Ciccotti, Michael G., et al. “Stress Sonography of the Ulnar Collateral Ligament of the Elbow in Professional Baseball Pitchers: A 10-Year Study.” The American Journal of Sports Medicine, vol. 42, no. 3, Mar. 2014, pp. 544–51. PubMed, https://doi.org/10.1177/0363546513516592.
7) Cinque, Mark E., et al. “Review of Anatomy of the Medial Ulnar Collateral Ligament Complex of the Elbow.” Current Reviews in Musculoskeletal Medicine, vol. 13, no. 1, Feb. 2020, pp. 96–102. PubMed, https://doi.org/10.1007/s12178-020-09609-z.
8) Shanley, Ellen, et al. “Using Stress Ultrasonography to Understand the Risk of UCL Injury Among Professional Baseball Pitchers Based on Ligament Morphology and Dynamic Abnormalities.” Orthopaedic Journal of Sports Medicine, vol. 6, no. 8, Aug. 2018, p. 2325967118788847. PubMed, https://doi.org/10.1177/2325967118788847.