Partial tears of the distal biceps tendon: MR appearance and associated clinical findings.

Purpose: To describe the magnetic resonance (MR) appearance and associated clinical findings of partial distal biceps tendon tears.
Design: Twenty elbow MR images at 1.5 T, performed over a 7 year period, were reviewed for an appearance of partial tears in the distal biceps. These images were assessed by two musculoskeletal radiologists for the extent of: (a) abnormal signal intensity within the tendon, and the presence of (b) bicipitoradial bursitis, and (c) bony microavulsive injury of the radial tuberosity. Medical records for nine of the 20 cases were reviewed for the clinical findings of ecchymosis, trauma, sensation of a "pop", loss of function, and acuity of onset.
Results: Twenty partial distal biceps tendon tears were seen. All displayed an abnormally increased signal in the distal biceps tendon. Three of 20 (15%) showed a 25% to 50% tear, ten of 20 (50%) showed a 50% tear, and seven of 20 (35%) showed a 75% to 90% tear. Bicipitoradial bursitis was seen in 11 of 20 (55%) cases. Bony microavulsive injury of the radial tuberosity was observed in 10 of 20 (50%). Of the nine cases reviewed for associated clinical findings, surprisingly, only three (33%) experienced an acute traumatic episode with an abrupt onset of pain. An insidious onset was reported in four of nine (44%). Sensation of a "pop" was recorded in only two of nine (22%) cases. Ecchymosis and loss of function were not seen in any of the cases. Finally, surgical conformation was obtained for three cases.
Conclusion: Partial distal biceps tendon tears have a characteristic MR appearance, demonstrate little functional deficit, and may be attritional in their etiology due to the observation of a low number of patients reporting trauma or an acute onset.