The short arrows on image 1a identify a thickened distal biceps tendon with increased signal, indicating tendinosis/tendonopathy. The long arrow identifies hypertrophy of the radial tubercle insertion site.
The arrows on image 2a identify a thickened distal biceps tendon with increased intrasubstance signal indicating tendinosis/tendonopathy.
Diagnosis:
Tendinosis/tendonopathy of the distal biceps tendon, without tear,
and with associated hypertrophy of the radial tubercle insertion site.
Discussion:
The biceps muscle has a dual origin. The short head originates
from the coracoid process of the scapula. The long head originates from the
supraglenoid tubercle of the scapula. The single distal tendon insertion is
on the radial tuberosity of the radius. The distal myotendinous junction of
the biceps muscle is located at the level of the distal arm. The distal approximately
7cm of tendon is therefore bare as it courses anteriorly through the level
of elbow joint, just lateral to the pronator teres muscle. This distal bare
7cm of tendon also rotates through the antecubital fossa area so that the
anterior surface is facing laterally at the radial tuberosity insertion. See
image 3
The biceps is an elbow flexor and a forearm supinator. Most biceps tendon
ruptures occur in the proximal (origin) tendons usually involving the long
head tendon at the shoulder. Distal tendon rupture is approximately 5% of
all biceps tendon ruptures. These distal tears are almost always at the radial
tuberosity insertion point and not at the distal myotendinous junction. The
tears are most commonly caused by a single acute event when the elbow is in
flexion with applied extension resistance/force, or from sudden forceful extension
against resistance.
