Examination: MRI of the elbow. Axial T1 and T2, Coronal T1 and T2, Sagittal T2 spur.

Findings: Discontinuous hypointensity within the biceps tendon sheath with intact lacertus fibrousus. Thickened and wavy biceps tendon retracted to the level of olecronon. Small areas of intramedullary contusion in the trochlea and radius. Mild sprain of the lateral collateral ligament and common extensor tendon.
 
Diagnosis: Biceps tendon rupture with preservation of the aponeurosis.

Discussion: The biceps long and short head tendons originate on the scapula. The muscle travels down the arm and attaches distally on the radial tuberosity. The distal tendon is invested within an aponeurosis (biceps aponeurosis or lacertus fibrosus).

Rupture of the distal biceps tendon is rare; it makes up about only 3% of all biceps tendon injuries. It typically occurs at the attachment radial tuberosity. MRI findings of a complete biceps tendon rupture include: 1) irregular tendon diameter, 2) discontinuous tendon signal, 3) peritendinous inflammation, 4) tendon retraction, 5) possible radial tuberosity avulsion. In this case blood partially filled the tendon sheath and gave the appearance of an intact tendon.

The differential diagnosis of a distal biceps tendon rupture include: 1) biceps or brachialis tendonopathy, 2) bicipital radial bursitis, 3) biceps mass.

1. Chew ML, Giuffre BM. Disorders of the distal biceps brachii tendon. RadioGraphics 2005; 25:1227-1237.
2. Falchook FS, Zlathkin MB, Erbacher GE, Moulton JS, Bisset GS, Murphy BJ. Rupture of the distal biceps tendon: evaluation with MR imaging. Radiology 1994; 190:659-663.
3. Stoller DW, Tirman TJ, Bredella MA. Diagnostic Imaging Orthopaedics. Amirsys Inc. Salt Lake City, UT. 2004.