Common Peroneal Nerve Palsy / Footdrop

Incidence

 

Most common lower limb neuropathy

 

Aetiology

 

Valgus TKR - 3%

 

HTO - 10%

 

Direct Trauma / Compression

 

Knee Dislocation

 

Tibial fracture

 

Cast / Dressing

 

Lateral Meniscus Repair

 

Anatomy

 

Bound to periosteum of fibula in proximal 40mm 

- safe between 40-70 mm

- high risk 70 - 160

 

Perform osteotomy between 40-70mm from head or >160mm

 

CPN

- L4,5 S1,2

- runs along biceps femoris (supplies short head)

- over lateral head gastrocnemius

- penetrates posterior intermuscular septum

- adherent to periosteum of fibular neck

- divides into superficial and deep peroneal nerves

 

SPN

- passes between PL and PB (supplies them)

- runs along lateral cortex of fibula

- runs between EDL and PLB

- pierces fascia 10-12 cm above lateral malleolus

- at some points is only 5mm from anterolateral fibula

- 6 cm above distal fibula, divides into intermediate and medial dorsal cutaneous nerves

 

DPN

- courses anteriorly around fibula neck

- runs along anterior cortex of fibular for 3-4 cm

- passes under intermuscular septum between lateral and anterior compartments

- enters the anterior compartment

- quite tethered here so is more at risk that SPN

- supplies muscles of the anterior compartment

- Tibialis anterior is first branch off DPN

- runs with anterior tibial artery between EHL and EDL (Tom Had A Night Down Town)

- passes under the extensor retinaculum

- branch to EDB, sensation to first web space

 

Clinical

 

Injury to CPN & DPN both cause foot drop

 

Injury to CPN 

- foot drop & supination deformity during swing phase 

- loss of T nnt (DF) 

- loss of peroneus longus / brevis (evertor)

 

Injury to Deep Peroneal 

- only foot drop 

- peronei supplied by SPN

 

Injury in THR

- sciatic nerve has tibial & peroneal components

- in sciatic nerve palsy usually lose one or the other

- tibial nerve supplies all hamstrings except short head biceps

 

At hip only 20% of volume of sciatic nerve is nerve fibres

- remainder is adipose tissue

- repair here often fails as unable to oppose nerve fibres

 

DDx

 

DDx CPN at fibula head vs Peroneal component of sciatic nerve at hip

- EMG of short head of biceps 

- denervation means sciatic nerve

 

DDx CPN v L5 nerve root

- abductor function lost with L5 nerve root injury

 

NHx

 

Some authors report resolution of palsy if left long enough

 

Dee  

- 30% recover

- 10% partial recovery

- 60% no recovery

 

Rose, Ranawat and Insall 1982

- 6/23 cases who had motor loss recovered completely

 

Asp and Rand

- 26 palsies 8998 TKR

- complete motor and sensory only 7/19 full recovery

 

Management

 

Non operative Management

 

Valgus TKR with immediate post-op palsy

 

Remove all constricting dressings

- flex to 30-40°

- ensure no compartment syndrome

- evacuate haematoma if present

 

Operative Management

 

1.  Neurolysis

 

A.  Krackow 1996

- patients with CPN palsy post TKR

- EMG and NCS at 3/52 / repeat at 3/12

 

Operative exploration at 4/12 if persistent dysfunction 

- release of nerve

- findings at surgery 

- epineural fibrosis

- bands of fibrous tissue constricting nerve at fibula head / proximal origin peroneus longus

- felt CPN palsy was not unlike peripheral compressions elsewhere & therefore treat as CTS

- 31 patients minimum 2 months post-op

- 97% improved post decompression 

 

Full recovery of motor function regards time from injury

- < 6/12        8/8

- 6 - 12/12    4/5

- 1-2 year      7/11

- > 2 years     6/7

 

Non operative

- only 3 of 9 treated non-op reported improvement

 

B.  Kim et al Neurosurg 2004

- neurolysis if recordable action potential

- 107/121 (88%) recovered useful function

 

2.  Nerve repair

 

Kim et al Neurosurg 2004

- 318 injuries

- 19 patients with end to end

- 16/19 good results at 2 years

 

3.  Nerve grafting

 

Siedel et al Neurosurg 2008

- 70% good results in patients with nerve in continuity (nerve stimulator)

- had external or internal neurolysis

- only 28% good functional result from sural nerve grafting

- related to graft length

- good result in 44% if graft < 6 cm (4/9)

- good result in 11% if graft > 6 cm (1/9)

 

4.  Tendon transfers

 

Tibialis posterior transfer

- passed through interosseous membrane

- sutured to T ant, EHL, EDL

 

Tibialis Posterior HarvestTibialis Posterior Transfer

 

Results

 

Ozkan et al J Reconstr Microsurg 2009

- 34/35 achieved DF to or above neutral

 

Diagnostic Dilemmas

 

1.  No anterior / lateral / posterior compartment working

 

DDx

 

A.  Compartment syndrome

- all 4 compartments

- huge compartment syndrome

 

B.  Sciatic Nerve

- no hamstrings

 

C.  Spine 

- taken out L4,5 & S1

- massive disc on MRI

 

2.  No anterior / lateral

 

DDx

 

A.  CPN knee

- normal short head biceps EMG

 

B.  CPN higher

- abnormal short head biceps EMG

 

3.  No posterior compartment

 

DDx

 

A.  Compartment syndrome

- deep and superficial posterior

 

B.  Tibial Nerve

- no hamstring function

 

C.  Spine

- S1 compression

- peroneals should be gone as well

 

4.  No Posterior / Lateral

 

DDx

 

A.  Spine

- S1 compression

 

B.  Compartment syndrome

 

5.  No Anterior

 

DDx

 

A.  Compartment syndrome

 

B.  Deep peroneal injury