Isolated rupture of a single bundle of a bifid distal biceps brachii tendon

Abstract

I njury of the biceps tendon nearly always affects the proximal biceps tendon, usually in the setting of rotator cuff injury with involvement of the restraints of the long head of the biceps. Significant injury to the distal biceps tendon is far less common, with an estimated rate of 1.2 per 100,000 patients per year. In these patients, differentiation between a partial and complete tear is of central importance in the determination of subsequent management. Unfortunately, even in the presence of tendon retraction owing to disruption of the bicipital aponeurosis or lacertus fibrosis, identification of complete rupture can be confounded by associated hemorrhage, edema, bursitis, or scarring in the setting of an acute or chronic injury. Furthermore, accurate characterization of distal biceps tendon injury can be complicated by the presence of normal variants of conventional biceps tendon anatomy. For instance, with bifid insertion of the distal biceps tendon, isolated rupture of a single bundle of a bifid tendon can mimic a partial tear of a nonbifurcated tendon. In such patients, MRI may offer the only noninvasive means to identify anatomic variations and their associated injuries. In this article, we describe a rare MRI diagnosis of isolated tendon rupture confined to the medial bundle of a congenitally bifid distal biceps tendon and provide radiographic-pathologic correlation in the form of intraoperative photographs that confirm the imaging findings. To our knowledge, this is only the fifth such case to be reported in the literature, and only the second with operative correlation. Potential implications of this anatomic variation on subsequent management are discussed. The patient gave consent to publish this case. CASE REPORT