Patient with a history of blunt/compressive trauma to the right distal upper arm 2 months ago, caused by direct impact from a horizontally tensioned steel cable against the biceps brachii muscle. Clinically, there is an abnormal contour of the muscle belly, resembling a reversed Popeye deformity. The patient reports no pain and no functional impairment, but is concerned about the cosmetic appearance.
Ultrasound of the right elbow and distal upper arm was performed, including assessment of the flexor muscles, extensor muscles, supinator muscle, lateral elbow structures including the common extensor tendon and annular ligament of the radius, radial nerve, posterior interosseous nerve, distal biceps tendon protocol, and elbow joints.
At the distal biceps brachii muscle, there is a large partial rupture of the muscle belly. The defect measures approximately 21.4 mm in width, 4.8 mm in thickness, and 41.1 mm in length. The defect contains anechoic fluid, compatible with an organizing hematoma or seroma. The findings are consistent with a posttraumatic muscle fiber rupture with residual intramuscular or subfascial fluid.
The distal biceps tendon itself shows no described features of a complete distal biceps tendon rupture. The ultrasound appearance correlates with the clinically visible contour abnormality of the muscle belly. Given the size of the muscle defect, persistent local indentation, asymmetry, or contour deformity may remain despite good recovery of pain and function.
1. Final diagnosis
Large posttraumatic partial rupture of the distal biceps brachii muscle belly with an intramuscular or subfascial anechoic hematoma/seroma, caused by direct compression trauma from a steel cable.
2. Differential diagnosis
The most likely diagnosis is a posttraumatic partial rupture of the distal biceps brachii muscle belly with organizing hematoma or seroma. Additional considerations include injury at the musculotendinous junction, intramuscular hematoma after contusion, fascial defect with local muscle contour change, and later-stage posttraumatic fibrosis or scar formation. If progressive hardening or calcification develops, posttraumatic myositis ossificans may be considered, for which radiography or CT can help confirm mineralization.
3. Teaching points
Ultrasound can clearly demonstrate partial muscle belly rupture, local fiber discontinuity, and associated fluid collections such as hematoma or seroma. In muscle trauma, echogenicity may vary depending on the age of hemorrhage and the degree of organization. A visible contour deformity may persist when there is substantial muscle fiber loss, scarring, or local displacement of muscle tissue, even when pain and function recover well.
4. Injury/disease information
Direct blunt or compressive trauma to the biceps brachii can cause partial muscle rupture without complete distal tendon avulsion. Conservative management is usually appropriate when there is no pain, strength loss, or functional limitation. Clinical documentation of elbow flexion strength, supination strength, endurance, and fatigue with repetitive loading is useful. MRI may be considered if symptoms progress, if neurological complaints develop, if there is uncertainty about the full anatomical extent, or if reconstructive or cosmetic treatment is being discussed.
Marc is founder of, and trainer at, SonoSkills. SonoSkills is an organization dedicated to MSK ultrasound education. He's also an MSK Sonographer at EchoConsult in Roermond, the Netherlands.
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