The supination effect of tendon transfer of the flexor carpi ulnaris to the extensor carpi radialis brevis or longus: A cadaveric study

Flexor carpi ulnaris (FCU) transfer to the extensor carpi radialis brevis ( ECRB) and/or the extensor carpi radialis longus (ECRL) has been commonly us ed to provide wrist extension. The ability of this wrist extension transfer to also provide forearm supination has been inferred but not formally inve stigated. This laboratory study investigated the forearm supination effect of FCU transfer to the ECRB and to the ECRL in a cadaveric model. Two vecto rs of pull were investigated: freeing either the distal one third or the di stal two thirds of the FCU ulnar origin. Five fresh-frozen, above-elbow, no nmatched cadaveric specimens placed in a mounting device that allowed the a rm to rotate about its ulnar axis starting from a full pronated position we re measured for resultant supination after tendon transfer and loading. Thi s study showed that the transfer of the FCU into either the ECRB or the ECR L resulted in no significant difference in maximum supination. The vector o f origin, however, did significantly affect the maximum supination obtained . Releasing the distal two thirds of the FCU ulnar origin resulted in a mea n supination that was significantly greater than the mean supination achiev ed with releasing the distal one third of the FCU ulnar origin. We conclude d that in the cadaveric model, transfer of the FCU into either the ECRB or ECRL provided similar resultant supination and that freeing the distal two thirds of the FCU ulnar origin provided significantly more supination than freeing only the distal one third. For the hand surgeon treating wrist flex ion in combination with forearm pronation deformity, transfer of the FCU in to the ECRB and/or the ECRL can be used to concomitantly provide wrist exte nsion and forearm supination. (I Hand Surg 1999;24A:1091-1096. Copyright (C ) 1999 by the American Society for Surgery of the Hand.).