Radial Nerve

Issues

 

1. Loss of wrist extension

2. Loss of finger extension

3. Loss of thumb extension

 

Aetiology

 

High lesion (loss of wrist extension)

- humeral fracture (Holstein Lewis)

- compression (Saturday night palsy)

 

Low lesion (PIN - wrist extension intact)

- fracture / dislocation elbow

- trauma / laceration

- iatrogenic - ORIF proximal radius

 

Clinical Features

 

High lesion

- triceps weakness uncommon (lesion usually past triceps innervation)

- wrist drop (ECRL, ECRB)

- inability to extend MCPJ (EDC)

- inability to extend thumb (EPL, EPB)

- sensory defect in anatomical snuffbox

 

Low lesion

- triceps intact

- wrist extension ECRB / ECRL intact

- no sensory deficit

- inability to extend MCPJ (EDC)

- inability to extend thumb (EPL, EPB)

 

Splints

 

1.  Radial Splint / Lively splint

- rubber bands & outrigger

- bands replace EPL / ECRB / EDC

 

2.  Simple static extension splint

- passive ROM to maintain supple joints

 

Investigation

 

NCS at 3/52 

- SNAP intact - neuropraxia

 

EMG at 3/12

- no reinnervation potentials

- poor prognosis

 

Options

 

1.  Explore at 4/12 if no recovery

 

Terzis et al Plast Recon Surg 2011

- surgical repair in 35 radial nerves

- 77% good outcome

 

Lee J Hand Surg Am 2008

- sural nerve grafting of high radial nerve injury

- 80% good or excellent results in regards motor function

 

2.  Tendon transfers

 

Indications

- no recovery at 6 - 9/12

- usually 1 mm / day

- should see ECRL by 6 months

 

Tendon Transfers

 

Goals

 

1.  Wrist Extension / ECRB

 

Pronator Teres

 

2.  Digit Extension / EDC

 

A. FCU

 

Problem

- is the most important wrist flexor

- only ulnar deviator / may result in radial deviation

 

B.  FDS middle finger

 

C.  FCR

- many authors favour 

- gives strong grasp 

 

3.  Thumb Extension / Abduction

 

A.  PL to EPL 

- line of pull via 1st dorsal compartment

- works well as gives some abduction

 

B.  FDS to RF (if no PL)

- can pass through intra-osseous membrane or tunnel subcutaneously

 

High Radial Nerve Transfers

 

Basis is use of PT for wrist extension

 

Jones Transfer

1.  PT to ECRL / ECRB

2.  FCU to EDC

3.  FCR to EPL (+ EPB & APL)

 

Problem is that both wrist flexors are transferred

- loss of FCU may lead to radial deviation

 

Brand Transfer

1.  PT to ECRB

2.  FCR to EDC

3.  PL to rerouted EPL

 

Problem 

- PL absent in 20% 

- alternative FDS RF / MF

- take through interosseous membrane or tunnel subcutaneously

 

Boyes

1.  PT to ECRL / ECRB

2.  FCR to EPB & APL

3.  FDS MF / EDC

4.  FDS RF / EPL & EIP

 

Technique Brand Transfer

 

Set up

- tourniquet

- arm table

 

Incisions

 

1.  PT incision

- over insertion on midportion radius

- dissect between ECRL and ECRB

- take entire periosteal insertion off radius

- need to keep long

 

2.  FCR / PL incision

- distal volar incision

- take both tendons as distal as possible

 

FDS RF

- make incision in palm over A1 pulley of RF

- if need FDS to RF must take proximal to bifurcation

 

3.  Dorsal incision

- proximal to extensor retinaculum, expose EDC and EPL

 

Transfers / Tensioning

 

1.  PL to EPL

- tunnel PL / FDS subcutaneously under SRN to EPL

- place thumb abducted and extended

- pulve taft weave

- through tendon 4 times at 90 degrees to each other 

- 4.0 ticron stitches at each pass

- check tension

 

2.  FCR to EDC

- pass FCR through all 4 tendons of EDC

- may need to take through EDMB

- check tension

- fingers should be in cascade in wrist flexion

- full extension with wrist extension

 

3.  PT to ECRB

- PT passed through ECRB with wrist in full extension

- again check tension

 

Post op

 

0 - 4 weeks splint

- wrist and MCPJ extension

- active finger extension (DIPJ, PIPJ)

 

4 - 6 weeks

- active MCPJ extension

 

Wrist flexor to finger extensor

- teach patient to flex wrist & extend fingers

- after a while they can extend fingers without flexing fingers

 

Pin Palsy Transfers

 

Wrist extension not required

 

Transfers

- FCR to EDC

- PL to EPL