Opposition transfer

To improve thumb opposition in congenital thumb hypoplasia, an opposition transfer should be considered. This entails moving an expendable musculotendinous unit from another local site to augment thumb abduction and pronation. Classical opposition transfers include:

• Huber transfer:
  • the abductor digit minimi is approached through an incision on the ulnar side of the hand
  • it is released distally and tunneled subcutaneously across the palm to the thumb base
  • it is inserted into the extensor mechanism and capsule of the MCPJ or the residual abductor pollicis brevis tendon
  • care is taken to avoid damage to the ulnar nerve near the pisiform bone
• flexor digitorum superficialis transfer:
  • FDS to the middle or ring finger is accessed via an incision at the level of the proximal interphalangeal joint
  • the tendon is retracted back to and brought out of an incision in the mid-palm
  • it is then subcutaneously tunnelled to around the distal border of the transverse retinacular ligament and inserted into the same position on the MCPJ of the thumb like a Huber transfer
  • an advantage of this transfer is that a small slip of the tendon can be re-routed around the MCPJ to reinforce or reconstruct the ulnar collateral ligament