Terminal bifurcation of the biceps brachii muscle and tendon: anatomic considerations and clinical implications.

OBJECTIVE: The objective of our study was to describe the anatomic variation of a bifurcated distal biceps tendon with MRI, histology, and dissection in cadavers and to report the MR appearance of superimposed lesions in a patient population with this anatomic variant.

MATERIALS AND METHODS: Visual and histologic examinations of the distal biceps brachii tendon in eight sectioned fresh-frozen elbow specimens were performed. Dissection of 17 elbow specimens was performed to describe the distal biceps brachii tendon. In addition, all elbow MRI reports over a 3-year period (n = 411) were retrospectively reviewed to determine the presence of bifurcation of the distal biceps brachii tendon.

RESULTS: The distal biceps brachii tendon appeared bifurcated in 25% of the sectioned specimens, and these findings were confirmed histologically. The distal biceps brachii tendon was completely separable into two components-that is, a short head and long head- throughout their proximal to distal extent in 41.2% of the dissected specimens. The distal biceps brachii tendon appeared bifurcated in 11.8% of 68 clinical cases that showed distal biceps brachii tendon abnormalities or injuries. The following patterns of injury were noted: complete rupture of both tendons (n = 1), complete rupture of the short head and normal insertion of the long head (n = 2), complete rupture of the short head and partial tear of the long head (n = 2), partial tear of both tendons (n = 2), and complete rupture of the short head and tendinosis in the long head (n = 1).

CONCLUSION: A bifurcated distal biceps brachii tendon is an anatomic variant that arises from persistent division between the short head and long head of the distal biceps brachii tendon and can be characterized with MRI. Knowledge of a bifurcated distal biceps brachii tendon is important to characterize injury to the components and to avoid pitfalls in imaging diagnosis.