Tendon Transfer Principles
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Direct answer
A tendon transfer moves a working muscle-tendon unit to a new insertion to restore a lost function, most often after a peripheral nerve palsy that will not recover. The donor must be expendable, with adequate power of at least grade 4 and matched excursion, and it must pull in a straight line. Stable joints, full passive movement and an intact sensory supply are prerequisites for a good result.
What you must remember
- One muscle, one function: each transfer should restore a single action, because a donor cannot do two jobs after transfer.
- Expendable donor: the donor muscle should be a synergist whose loss does not leave a deficit, and it should have MRC power of grade 4 or 5.
- Matched excursion and power: the donor's range of movement and strength should suit the recipient's needs, otherwise the result is weak or restricted.
- Straight line of pull: the transfer should follow a path that gives a direct pull, using pulleys where a bend is unavoidable.
- Prerequisites: a stable, correctly positioned joint, full passive range, good soft tissue and an intact sensory and motor supply.
- Radial palsy: pronator teres to extensor carpi radialis brevis restores wrist extension, and a flexor to extensor digitorum communis transfer restores finger extension.
- Ulnar claw: a Zancolli lasso loops flexor digitorum superficialis through the A1 pulley to stop hyperextension and add flexion at the metacarpophalangeal joints, and transfers such as Brand's or Fowler's restore finger function.
Planning a transfer in four steps
The sequence matters because a transfer that ignores any single principle is likely to fail, and the choice of donor follows from the recipient function that must be restored. The steps below follow the usual planning sequence.
- Define the function: decide exactly which movement is lost, such as wrist extension, finger extension or thumb opposition, and aim the transfer at it.
- Test the donor: check the candidate muscle for power, excursion and whether its loss is acceptable, using the rule of one muscle for one function.
- Prepare the joints: stabilise the wrist or joint, make sure the passive range is full and correct any contracture before the transfer.
- Set the tension: position the joint correctly during suturing, since over-tensioning causes a fixed deformity and under-tensioning gives weak function.
| Nerve palsy | Lost function | Common transfer |
|---|---|---|
| Radial | Wrist and finger extension | Pronator teres to extensor carpi radialis brevis; flexor to extensor digitorum communis |
| Median | Thumb opposition | Palmaris longus or ring finger flexor digitorum superficialis to abductor pollicis brevis |
| Ulnar | Claw correction and intrinsic function | Zancolli lasso (FDS looped through A1 pulley); Brand or Fowler transfers |
Wrist stability comes first in radial palsy, because a stable wrist is needed for a power grip before finger extension is restored. Texts differ on the preferred donor for finger extension and for opposition, so the principles are the answer the exam tests.
Where the exam tries to catch you
Most lost marks come from using an unsuitable donor or from transferring into a stiff joint.
- Trap: the flexor carpi ulnaris is the default donor for every transfer. Correct: the donor is chosen for power and excursion in that patient, and flexor carpi radialis is sometimes preferred for finger extension to keep the ulnar stabilising unit.
- Trap: a transfer is performed into a joint that is still stiff, since the tendon will restore the movement. Correct: the joint must have full passive range first, or the transfer will be restricted and fail.
- Trap: a stronger muscle is always the better donor. Correct: a donor with the right excursion and an expendable role is preferred, since power alone cannot make a poor line of pull work.
Frequently asked questions
What are the basic principles of tendon transfer?
The basic principles of tendon transfer are one muscle for one function, an expendable donor with power of grade 4 or 5, matched excursion and a straight line of pull. The joints must also be stable with full passive range before the transfer.
Which transfer restores wrist extension in radial nerve palsy?
Pronator teres transfer to extensor carpi radialis brevis is the standard transfer to restore wrist extension in radial nerve palsy. Stabilising the wrist first is the priority, because a stable wrist is needed for a power grip.
What is a Zancolli lasso?
A Zancolli lasso is a procedure for flexible ulnar claw in which a flexor digitorum superficialis slip is looped through the A1 pulley and sutured to itself. It stops hyperextension and adds active flexion at the metacarpophalangeal joints.
Why is a full passive range needed before tendon transfer?
A full passive range is needed before tendon transfer because the transferred muscle can only move a joint through the range it already has. A stiff joint will not gain movement from a transfer and the result is restricted or failed.