Mechanical evaluation of the Pronator Teres rerouting tendon transfer.

We simulated pronator teres rerouting using a three-dimensional biomechanical model of the arm. Simulations comprised the evaluation of changes in muscle length and the moment arm of pronator teres with changes in forearm axial rotation and elbow flexion. The rerouting of Pronator Teres was simulated by defining a path for it through the interosseous membrane with re-attachment to its original insertion. However the effect of moving the insertion to new positions, 2 cm below and above, the original position was also assessed. The effect on total internal rotation and external rotation capacity was determined by calculating the potential moments for pronator teres, supinator, pronator quadratus, biceps brachii and brachioradialis. Pronator teres was found to be a weak internal rotator in extreme pronation, but a strong internal rotator in neutral rotation and in supination. After rerouting pronator teres was only a strong external rotator in full pronation and not at other forearm positions, where the effect of rerouting was comparable to a release procedure.