Tendon transfer for the restoration of thumb opposition: The effects of friction and pulley location

BACKGROUND: The authors compared the gliding resistance among three commonly used pulley sites used for oppositional transfers. METHODS: Eight fresh-frozen cadaver forearms were studied. The ring finger's flexor digitorum superficialis was used as a donor tendon in all specimens. An oppositional transfer was created to the thumb using three pulley sites: the Royle-Thompson, the Guyon canal, and the flexor carpi ulnaris tendon loop pulleys. The flexor digitorum superficialis was inserted into the palmar radial portion of the abductor pollicis brevis in all cases. Gliding resistance was then measured and compared. Final thumb position was measured to assess the amount of thumb palmar abduction and opposition created with each pulley configuration. RESULTS: The average gliding resistance of tendons passed within the Royle-Thompson, Guyon canal, and flexor carpi ulnaris loop pulley were 1.27, 0.58, and 0.44 N, respectively. Gliding resistance for the Royle-Thompson pulley was found to be significantly higher than that for the Guyon canal or flexor carpi ulnaris loop pulley (p < 0.05). There was no significant difference between the Guyon canal and flexor carpi ulnaris loop pulleys with regard to gliding resistance. The flexor carpi ulnaris loop pulley produced the greatest amount of palmar abduction (p < 0.05), whereas the Guyon canal and Royle-Thompson pulleys produced the greatest amount of thumb opposition. CONCLUSIONS: The Guyon canal and flexor carpi ulnaris loop pulleys produced lower friction than the Royle-Thompson pulley. The Guyon canal pulley produced greater thumb opposition compared with the flexor carpi ulnaris loop pulley and represents an ideal pulley site for restoration of thumb opposition.