The anatomy of the distal biceps tendon and aponeurosis has not been studied in detail.
Seventeen cadaver elbows were dissected with loupe magnification to identify the details of the distal biceps tendon and the lacertus fibrosus.
In ten of the seventeen specimens, the distal biceps tendon was in two distinct parts, each a continuation of the long and short heads of the muscle. The remaining seven specimens showed interdigitation of the muscle distally. The tendon continued from each muscle belly. The short head inserted distal to the radial tuberosity and was positioned to be a more powerful flexor of the elbow, while the tendon of the long head inserted on the tuberosity further from the axis of rotation of the forearm and was positioned to be a stronger supinator. The bicipital aponeurosis consisted of three layers and completely encircled the ulnar forearm flexor muscles. The aponeurosis may be important in stabilizing the tendons distally.
The double tendon insertion may allow an element of independent function of each portion of the biceps, and, during repair of an avulsion, the surgeon should ensure correct orientation of both tendon components.