Median Nerve Palsy - Rob Lee 20/10/2005

Low Median Nerve Palsy
 
The motor deficit primarily involves loss of opposition of the thumb
FPL provides most of the strength in flexion
Loss of the radial two lumbricals is not clinically significant
Opposition is a composite of many movements including rotation of the thumb into pronation and abduction or lifting of the thumb away from the palm. 
APB is the most important muscle that is lost. Thumb abduction strength decreases on average by 70%
 
In general, 1/3 of patients do not need opponensplasty since adequate thumb abduction is gained from other muscles
Treatment – Restore thumb opposition – see below
 
High Median Nerve Palsy
 
As above but also loss of pronation of forearm, wrist flexors, index & long finger flexion and thumb flexion
 
Accessory transfers in high median nerve lesions:
I.          FPL is reinforced by brachioradialis
II.        FDP of index & long fingers are reinforced by transfer of ECRL
III.       FDP of ring and small fingers are anchored to FDP of index and middle fingers using side to side repair
 
Opponensplasty – EIP transfered to APB (Burkhalter)
 
Accessory procedures include either arthrodesis of the MCP joint or the distal IPJ of the thumb, depending of the stability
 
 
Opponensplasty
 
Many procedures described
Common factor is selection of extrinsic tendon and trasfer to suitable point to provide correct angle for opposition
Sometimes pulley required to provide direction
Need stable metacarpophalangeal joint (w/ adequate extension) (if this is not case, then consider a concomitant MCP fusion)
With any attempted opponensplasty, it is important the transfer lie in the direction of the APB
 
 
Riordan Opponensplasty (Ring FDS to APB)
 
Contraindicated if flexor tendons have been previously lacerated
Provides opposition, improves pinch, & ensures better utilization of extensor and flexor muscles
Ring FDS is transected at base of digit & is isolated at wrist
Tendon is passed around the FCU, and then through a pulley (created from 1/2 of the FCU tendon at its insertion) and is then passed subcutaneously to the proximal phalanx of the thumb
 
Proprius extensor tendon opponensplasties (EIP to APB)
 
Burkhalter. JBJS Vol 55-A. 1973. 725.
 
Procedure of choice if finger flexors had previously been cut and required tendon repair.
Transfer of choice with a high median nerve palsy and in insensate thumb
Tendon is elevated thru several short incisions until there is complete mobilization up to the musculocutaneous junction
Tendon is passed around the ulnar border of the ulna and then across the palm
         
 
Huber opponensplasty (Abductor Digiti Quinti to APB)
Littler And Cooley.   JBJS Vol 45-A. 1963. P 1389
 
 Reserved for high median nerve palsy or for congenital deficiencies
ADQ will probably provide only 25% of the normal APB strength, but does provide a cosmetic fullness that is lost with thenar atrophy
This may be combined with FDS transfer
A possible complication includes iatrogenic ulnar tunnel syndrome
 
Other opponensplasties
 
Groves and Goldner – FCU with FDS
Camitz – PL to APB


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