Biomechanic Comparison of 3 Tendon Transfers for Supination of the Forearm

PurposeFlexion–pronation of the hand and the forearm is a common deformity when the upper extremity is affected by cerebral palsy. Solutions used to improve the pronation deformity and increase supination include transfer of the flexor carpi ulnaris to the extensor carpi radialis brevis, pronator teres rerouting, and brachioradialis rerouting. The purpose of this study was to compare the biomechanic efficacy of these 3 tendon transfers in simulated supination in cadaveric forearms.MethodsTen fresh-frozen adult cadaveric above-elbow upper extremities were used. In each specimen the 3 tendon transfers were performed sequentially in random order and were loaded in increments of 4 N (1 lb) to a maximum of 36 N (8 lb). Measurements were recorded from the starting point of 90° of pronation. Statistical analysis of the data included the Student t test with the Bonferoni correction.ResultsFor all transfers, supination increased in a nonlinear manner as the load was increased in a nonlinear manner. For the flexor carpi ulnaris transfer, the forearm reached its neutral position at a load of 9 N (2 lb). The forearm continued to rotate to up to 84° of supination with 36 N (8 lb) of load. With the brachioradialis transfer, the forearm reached its neutral position at 13 N (3 lb) of load and continued to rotate to up to 33° of supination with 36 N of load. With the pronator teres transfer, the forearm never reached the neutral position. Under a maximum load of 36 N, only 55° of rotation from full pronation was obtained.ConclusionsTransfer of the flexor carpi ulnaris to the extensor carpi radialis brevis proved to be the most effective transfer for producing supination in cadavers. The brachioradialis transfer was second best. The pronator teres rerouting was the least effective transfer in effecting simulated supination in this experiment.