The Journal of Bone and Joint Surgery

Image Quiz

Trauma to the Elbow Caused by Lifting¹
(continued)

Answer: Isolated tear of the brachialis muscle.

Fig. 1

Fig. 1: T2-weighted magnetic resonance coronal image of the distal aspect of the humerus, showing a linear tear (curved arrow) and surrounding edema in the distal aspect of the brachialis. The brachialis insertion (straight arrow) is intact. An elbow joint effusion and normal marrow signal are also visible.

For larger view click on image

Serial clinical examinations and follow-up magnetic resonance imaging were performed. Over the next four weeks, the mass became less tender but caused an occasional burning sensation. The size of the mass was unchanged, and no warmth or erythema was noted. The findings on motor strength examination were 5 of 5 throughout.

Six weeks after the injury, repeat magnetic resonance imaging (with and without contrast medium) revealed increased signal within, and thickening of, the distal brachialis muscle. The plane of cleavage and the retracted muscle fibers were consistent with a partial rupture of the brachialis muscle, suggesting a traumatic injury rather than a malignant lesion.

Ten months after the initial presentation, the mass was smaller and nontender and the findings on physical examination were otherwise normal.

Discussion

Isolated rupture of the brachialis muscle appears to be a rare injury that has not been well documented. The current case involved a partial distal brachialis tear that responded to nonoperative treatment. Muscle injuries are common and can usually be diagnosed on the basis of the medical history and the physical examination. On examination, localized tenderness and pain with muscle activation are usually present. Our patient had a muscle tear just proximal to the musculotendinous junction that presented as a moderately painful mass. Magnetic resonance imaging is recommended only when a diagnosis cannot be made on the basis of the history and the physical examination². Magnetic resonance imaging can demonstrate both acute and chronic muscle tears. T1-weighted images may show disruption of the normal architecture of the muscle belly or the tendinous junction. T2-weighted images will show the increased signal related to edema and hemorrhage. These areas of abnormal signal can have a varied appearance ranging from linear to more mass-like³.

References:

1. Van den Berghe GR, Queenan JF, Murphy DA. Isolated rupture of the brachialis. A case report. J Bone Joint Surg Am. 2001;83:1074-5.
2. Noonan TJ, Garrett WE Jr. Muscle strain injury: diagnosis and treatment. J Am Acad Orthop Surg. 1999;7:262-9.
3. De Smet AA, Fisher DR, Heiner JP, Keene JS. Magnetic resonance imaging of muscle tears. Skeletal Radiol. 1990;19:283-6.