Isolated traumatic rupture of the brachialis muscle in a 9-year-old girl

Clinical History

A 9-year-old girl presented at the Emergency Room after she fell on her left elbow during a soccer game at school. Besides pain in the elbow, she presented with her elbow in a 90 degrees flexion with diffuse swelling and tenderness.

Imaging Findings

Initial elbow X-ray showed moderate intraarticular effusion without fractures. MRI of the elbow showed no sign of fracture, but confirmed the effusion in elbow joint previously seen on the X-ray examination. Furthermore it showed severe signal changes in the brachialis muscle, representing an almost complete rupture of the brachialis muscle fibres.

Discussion

Background: Among elbow injuries in children, fractures and dislocations are the most common type, where as muscle tears are particularly rare in this age group. Tears of the biceps muscle represent the most frequent muscle injuries around the elbow, while isolated tears of the brachialis muscle are very rare [1, 2]. Review of the literature shows that only few cases of brachialis muscle tears have been reported [3]. These are mainly adults or teenagers, who are particularly active in different sport disciplines [4], or were even elite sportsmen [5].

Clinical Perspective: Fractures around the elbow are the most frequent traumatic injury of this region in children, while muscle tears are uncommon in this age group.

Imaging Perspective: In some previously reported cases of brachialis muscle injuries, the patients could attribute the injury to a particular sports activity, but without knowledge of a specific moment when the injury may have occurred. That's why in some of these cases a neoplasm was initially suspected on MRI [4]. In our case the patient could easily relate the trauma to the practiced sports activity and she could precisely point out the time of accident. Furthermore the MRI report showed, without any doubt, an almost complete tear of brachialis muscle.
An anterioposterior and lateral view X-ray is the standard modality for diagnosing such an injury. The presence of joint effusion in an acutely injured paediatric elbow should be considered evidence of fracture until proved otherwise [6]. MRI is known as the golden standard in diagnosing soft tissue injuries in adults, and it should be considered as a diagnostic modality in children and adolescents trauma as well [7].

Outcome: After 2 weeks treatment with the cast, the patient had some pain from active movement of the elbow. At the last follow up after 6 weeks, the patient was pain free normal range of movements of the elbow.

Take Home Message, Teaching Points: Although they are rare, muscle tears in children can be a diagnostic challenge for X-ray in the acute phase. Therefore MRI in the sub acute phase should be considered. The use of open MR scanners can increase children's compliance and thus better diagnostic results in this age group. To the best of our knowledge, brachialis muscle tear in young children is not described in the literature.

Differential Diagnosis List

Final Diagnosis

Complete rupture of the left brachialis muscle

URL:	https://www.eurorad.org/case/9983
DOI:	10.1594/EURORAD/CASE.9983
ISSN:	1563-4086