Complete rupture of the distal biceps tendon is often an avulsion from the radial attachment and clinically evident. However, differentiation of complete from partial tears is sometimes difficult clinically, particularly if the bicipital aponeurosis remains intact. Most tears occur 1–2 cm above the radial tuberosity, where there is relative hypovascularity and a histologic structural transition point . Degeneration secondary to hypoxic tendinopathy occurs in this region. In complete rupture of the distal biceps tendon, there is discontinuity with or without retraction. The longitudinal view of the tendon. acquired with FABS imaging often best demonstrates the discontinuity . , FABS imaging (flexed elbow, abducted shoulder, supinated forearm with arm overhead and patient lyinn prone) provides a detailed view of the distal biceps tendon, including the difficult-to-assess region near its insertion on the radial tuberosity and is often helpful in differentiating partial from complete tears.
The proximal tendon is enlarged and demonstrates abnormal signal intensity. If the bicipital aponeurosis is intact, there may be no retraction, and at clinical examination the patient may even appear to retain some flexion and supination capability. The axial view is best for appreciating an intact bicipital aponeurosis. In partial tears, findings include a change (usually an increase) in caliber and abnormal contour of the tendon. Abnormal intratendinous signal intensity is seen at MR imaging. The US equivalent, reduced echogenicity, is often more difficult to confidently assess. Peritendinous fluid (edema, bursitis, or hemorrhage) may also be visible.
In our case , biceps can be traced upto its insertion site at the radial head with enlargement and thickening of proximal tendon. Abnormal intratendinous signal intensity can be appreciated in PD fat suppressed images along with peritendinous fluid signals. The conventional views (as in our case) don’t give a true longitudinal view of the tendon, FABS imaging is advised to differentiate distal biceps tendon partial tear from complete tear.