– Planning – must know strength, amplitude of excursion, and consider the expendability
– muscles typically lose one grade when transferred
– tendon transfers should be surrounded in fat
– passive range of motion should be maintained
– the straighter the new course of tendon, the better
SPECIFIC FUNCTIONAL GOALS
Restoration of Pinch – Restoration of Thumb Opposition
– Restoration of Thumb Adduction
Restoration of Index Finger Adduction
Restoration of Intrinsic Function
Restoration of Pinch – Restoring Thumb Opposition
– Thumb opposition is the ability of the thumb to move across the palm and oppose the other finger tips. This is a complex motion which is the result of coordinated function of all the long and short muscles of the thumb. There includes the actions of thumb abduction, MCP flexion, thumb pronation, proximal phalangeal radial deviation, and motion of the thumb towards the fingers.
– Conceptually, the act of “pinch” requires that the thumb be positioned, then a force be applied. Think of “opposition” as functioning predominantly to get the thumb into position, and “adduction” as functioning to exert power.
– Opposition is lost in low median nerve injuries and in polio – usually the loss is partial.
– The most important muscle in thumb apposition is the abductor pollicis brevis (median nerve); restoration of opposition is focused on restoring APB function.
APB – internally rotates and abducts the thumb away from the index metacarpal, abducts and internally rotates the thumb proximal phalanx on its metacarpal, and assists EPL in extending the IP joint
Before doing anything to restore the APB, you must consider any deformities and correct these first or concurrently. The EPL begins to act as an adductor in order to assist in pinch – this may draw the tendon into the web space, closing it, and leaving an external rotation deformity to the thumb. Correct the web-space contracture with Z-plasty, and get the thumb into position with a CMC arthroplasty or arthrodesis. Thumb MP or IP arthrodesis may also have to be performed.
Techniques to restore opposition
Many techniques – all have in common the selection of one extrinsic expendable tendon brough from an ulnar direction and transferred to a point on the thumb at a suitable angle to pull the thumb into opposition.
Riordan – FDS of ring finger brought through a loop in FCU, then to the base of thumb
Brand – FDS of ring finger brought through a subcutaneous tunnel just supeficial to the hook of the hamate
Burkhalter – extensor indices proprius brought volarly along the ulnar aspect of the wrist just superficial to pisoform, then across the palm to the base of the thumb
Restoration of Pinch – Restoring Thumb Adduction
Opposition is the refined, unique movement that places the thumb within the flexion arc of the fingers so that the tips of the thumb and fingers can oppose; adduction is the force that stabilizes the thumb in the desired position.
When the adductor pollicis is paralyzed (ulnar nerve palsy), firm pinch between the pulps of the thumb and the flexed index and middle fingers is impossible, and the thumb cannot be brought across the palm to contact the 4th and 5th.
Pinch against the index finger is facilitated by FPL in this case (produces Froment’s sign)
Techniques to restore adduction
Brand – FDS of ring finger through the natural openings of the fascia between the ring and long fingers at the distal third of the palm, then subcutaneously into the radial aspect of the thumb
Boyes – brachioradialis or ECRL to a free tendon graft (plantaris or palmaris longus) dorsally, through the 3-4 webspace, then across the palm to the base of the thumb.
Royle-Thompson (modified) – FDS of ring finger split into two limbs, then tunneled subcutaneously to the base of the thumb, with one slip going to EPL, the other going dorsally to the tendon of adductor pollicis.
Restoring Index Finger Abduction
Abduction of the index finger is important for