Medicolegal aspects of peripheral nerve injury - PowerPoint Presentation

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Medicolegal aspects of peripheral nerve injury

Alistair Ross MB FRCSConsultant Orthopaedic Surgeon, Bath, UKAssociate Editor The Bone & Joint Journal

Cambridge Annual Medico-Legal Conference

Peterhouse,Cambridge,2016Slide2

Peripheral nerve: organisationSlide3

Peripheral nerve: structureSlide4

Peripheral nerve injury: classification

Neurapraxia Axonotmesis NeurotmesisSeddon HJ Three types of nerve

injury

Brain

1943, 66 (4): 238-283

ἀπραξία:

inaction

τμησις:

a cutting (of)Slide5

Peripheral nerve injury: neurapraxia

Neurapraxia: a non-degenerative lesion of a nerve characterised by a complete or partial failure to propagate an action potential (conduction defect) along the nerve resulting in motor and/or sensory loss. Slide6

Peripheral nerve injury: neurapraxia

Usually caused by compression or ischaemia, resulting in ischaemia of the myelin sheath.Can be reversed if the injurious agent is removed. Nerve remains intact. Wallerian degeneration does not occur. Slide7

Peripheral nerve injury: neurapraxia

Stimulation of the distal segment of the nerve evokes a response.Normal motor action potential expected distal to the site of injury by day 10. Recovers by re-myelination of distal segmentTime to recovery: 2-12 weeksSlide8

Peripheral nerve injury: neurapraxia

The assumption that a lesion is a neurapraxia rather than a more severe injury leads to delay in diagnosis and a poorer outcome.A potentially dangerous diagnosis to make particularly in the presence of persistent pain which suggests that the injurious agent is continuing to act.Diagnosis should not be made in the presence of a strong Tinel test which indicates that axons have been ruptured. Slide9

Peripheral nerve injury: axonotmesis

Axonotmesis: disruption of the axon and its myelin sheath. The supporting structures, Schwann cells, endoneurium, perineurium and epineurium, remain intact. Slide10

Peripheral nerve injury: axonotmesis

Usually the result of severe compression or crush.Wallerian degeneration occurs distally and proximally to the closest node of Ranvier.Repair is by a combination of collateral sprouting in lesser injuries and axonal regeneration in more severe injuries. The latter occurs at 1-2mm per day. Time to recovery: 2 to 6 monthsSlide11

Peripheral nerve injury: axonotmesis

Nerve conduction studies show a loss of conduction in the distal segment 3-4 days after injury (demyelination).Small or absent compound muscle or sensory nerve action potentials (axon loss)EMG studies

show fibrillation potentials and sharp waves 2-3 weeks after injury (axon loss).

Degree of recovery depends on the age of the patient, the site of injury and the amount of fibrosis that occurs.Slide12

Peripheral nerve injury: neurotmesis

Neurotmesis: the complete disruption of a peripheral nerve by any means.Slide13

Peripheral nerve injury: neurotmesis

Wallerian degeneration occurs distal to the lesion.Nerve conduction studies show a loss of conduction in the distal segment 3-4 days after injury.EMG studies show fibrillation potentials and sharp waves 2-3 weeks after injury.Surgical intervention is required to repair the nerve, whether by direct suture or grafting.

Time to recovery 2 to 18 monthsSlide14

Peripheral nerve injury: causes

ClosedIschaemia (A/C)Crush / Compression (A/C)TractionThermal injuryElectric shockVibrationRadiation

Open

Injection

LacerationSlide15

Iatrogenic peripheral nerve injury

…or iatropathic…or iatrogenous…but caused by those treating a patientSlide16

Iatrogenic peripheral nerve injury

“When a patient enters hospital without a nerve lesion and emerges with one, it is seldom possible to resist an allegation of negligence.”

Bonney GLW

Iatrogenic injuries of nerves

J Bone Joint Surg 1986; 68B: 9-13Slide17

“If there is an incision over the line of a main nerve and if, after operation, there is complete paralysis (including vasomotor and sudomotor paralysis) in the distribution of that nerve, speculation is unnecessary: the nerve has been cut, and there will be no recovery unless it is explored and repaired.”

Bonney GLWIatrogenic injuries of nervesJ Bone Joint Surg 1986; 68B: 9-13

Iatrogenic peripheral nerve injurySlide18

Bonney GLWIatrogenic injuries of nerves

J Bone Joint Surg 1986; 68B: 9-13“When pressure on a nerve has been followed by partial paralysis in its distribution, but stimulation below the level of the lesion produces a motor response, it is reasonable to assume that there has been a conduction block which will recover.”

Iatrogenic peripheral nerve injurySlide19

Bonney GLWIatrogenic injuries of nerves

J Bone Joint Surg 1986; 68B: 9-13“Between these extremes, precise diagnosis is much more difficult.”

Iatrogenic peripheral nerve injurySlide20

“Failure to make the diagnosis of a nerve injury, and failure to treat that complication of the first surgery, the iatrogenic nerve injury, is as much a cause for concern as the initial injury to the peripheral nerve.”

Dellon AL Invited discussion: management strategies for iatrogenic peripheral nerve lesions.Annals of Plastic Surgery 2005,54: 140-42Iatrogenic peripheral nerve injurySlide21

Iatrogenic PNI: incidence

Overall incidence unknownNHS Litigation Authority does not specifically record cases under the heading ‘peripheral nerve injury’Slide22

Iatrogenic PNI: incidence

1990 to 1998722 consecutive cases of peripheral nerve injury126 iatrogenic (17.5%)Usually resulting from orthopaedic surgery, trauma or hand surgery‘Lumps and bumps’ surgery

Kretschmer T et

al

Evaluation of iatrogenic lesions in 722 surgically treated cases of peripheral nerve trauma

J Neurosurg 94:905–912, 2001Slide23

Adequate outcome data available for 97/126 patients

Results:Very good: 24%Good: 46%Unchanged: 26%Worse: 4%Kretschmer T et al

Evaluation of iatrogenic lesions in 722 surgically treated cases of peripheral nerve trauma

J Neurosurg 94:905–912, 2001

Iatrogenic PNI: incidenceSlide24

Iatrogenic PNI: incidence

1991 to 1998612 cases of iatrogenic PNI291 subsequently explored144 the subject of litigation

Khan R & Birch R

Iatropathic injuries of peripheral nerves

J Bone Joint Surg 2001, 83B(7); 1145-1148Slide25

Iatrogenic PNI: causes

Excision of tumour or cyst 67Lymph-node biopsy 52Internal fixation of fracture 48Varicose vein/arterial surgery 20

Carpal tunnel decompression

18

Shoulder stabilisation 16

Total 231 Slide26

‘Lumps and bumps’: SchwannomaSlide27

Lymph node biopsySlide28

Iatrogenic PNI: by specialty

Orthopaedics 174General surgery 70Vascular surgery 11Obs / Gynae 9Plastic surgery

7

Cardiothoracic 5

ENT surgery

5

Anaesthetics

4

Neurosurgery

4

Maxillofacial surgery

2

Total

291Slide29

Anaesthesia-related perioperative PNI

Defined as a new (within 48 hours) sensory and/or motor deficit in any patient who had been sedated or anaesthetisedInjuries as a result of the surgical procedure itself excludedOverall incidence: 0.03% (112 / 380,680 ops)

Welch MB et al

Perioperative Peripheral Nerve Injuries. A Retrospective Study of 380,680 Cases during a 10-year Period at a Single Institution

Anesthesiology 2009; 111:490–7Slide30

Anaesthesia-related perioperative PNI

Most commonly affected nerves:Ulnar (28%)Brachial plexus (20%)Lumbosacral nerve root (16%)Spinal cord (13%)Slide31

Anaesthesia-related perioperative PNI:principal causes

Poor padding and positioning of limbsNeedle trauma secondary to regional anaesthesiaHaematoma surrounding a nerveLocal anaesthetic agents: toxicity and direct damage from intraneural injectionSlide32

Anaesthesia-related perioperative PNI:principal causes

Pre-existing diseaseDiabetesSmokingHypertensionPre-existing neuropathy Perioperative problemsHypovolaemia, dehydration, hypotension,

Hypoxaemia, electrolyte disturbance & hypothermiaSlide33

PNI: Tourniquets

Bruner's ten rules for the safe use of tourniquet (Modified by Braithwaite and KlenermanJ Med Def Unions 1996;12:14-15)Slide34

Peripheral nerve injury: management

Diagnosis is the responsibility of the treating clinician.Nerve repair is the business of a sub-specialist. Slide35

Peripheral nerve injury: management

The earlier a peripheral nerve injury is diagnosed and treated the betterEase of recognition of injuryEase with which the nerve stumps can be mobilised and approximatedLack of scarring and distortion of the anatomyBest results achieved by early direct nerve repairSlide36

PNI: delay in repair

A delay of two months halves the number of axons crossing a repair and halves their rate of growth.Further deterioration occurs with longer delay.Motor

end plate loss progresses even after repair and is near total after

one

year (for a proximal

repair).

Central

cord changes also progress prior to repair and become less reversible with time

.

British Orthopaedic Association ‘Blue Book’ 2011Slide37

PNI: management of neurotmesis

If complete or partial laceration to nerve identified at operation (whether the result of trauma or iatrogenic injury):

Trained

nerve surgeon: primary epineural suture.

Untrained surgeon: attempt to oppose ends; gentle mobilisation of nerve if necessary; tag nerve end/s with coloured epineural sutures.Slide38

Clear, accurate documentation of the injury and action taken.

Prompt discussion with, and referral to, a nerve surgeon.Discussion with/explanation to patientAccurate early postoperative assessment and documentation of neurological deficitPNI: management of neurotmesisSlide39

Peripheral nerve injury: management

If patient found to have neurological deficit postoperatively:Clear, accurate documentation of neurological deficitInform patient of possible nerve injuryDiscussion with/referral to nerve surgeonSlide40

Peripheral nerve injury: management

If patient found to have neurological deficit postoperatively:At this stage it is unclear of the nature of the lesionIf the nerve is thought to have been divided (cf

Bonney) :

re-explore with a view to repair

If not, EMG and NCS at three weeksSlide41

Iatrogenic PNI: indications for surgery

Clinical evidence of neurotmesisFailure of recovery from presumed axonotmesis at the predicted timeDeterioration of lesion while under observationPersistent, intractable painSlide42

Iatrogenic PNI: aim of surgery

Establish diagnosis Relieve pain Improve function Slide43

PNI: Electrodiagnosis: timing of studies

Baseline study (0–7 days)Usually unnecessaryCan only determine whether or not a nerve has been injured, not the degree of injuryBaseline for later comparisonDocuments nerve continuity with

presence of

voluntary motor units on

EMG

NB. If fibrillation potentials or sharp waves are seen at this stage, this implies pre-existing disease/injury

After: Quan.D

. & Bird SJ

Nerve

Conduction Studies and Electromyography in the

Evaluation of Peripheral Nerve Injuries

The

University of Pennsylvania Orthopaedic Journal

12: 45–51, 1999Slide44

PNI: Electrodiagnosis: timing of studies

Initial study (10–21 days)Distinguishes lesions with predominant demyelination from those with substantial axonal lossAssesses extent of axonal loss (

reduced CMAP

amplitude and number of

motor units

recruited with maximum effort)

Follow-up study (

3–6 months

)

Documents

extent of reinnervation

in markedly

weak muscles

If necessary, intraoperative studies

assess presence

of axonal regeneration

through the

injured segmentSlide45

Iatrogenic PNI: indications for non-operative treatment

Clinical improvement on presentationProlonged delay in presentationPalliative treatment preferredPain relief possible by non-operative means

(Outstanding claims for compensation)Slide46

Peripheral nerve injury: mismanagement

Inadequate informed consent Avoidable damage to nerves/nerves Delay in diagnosis / missed diagnosis Delay in referral Delay in treatment

Inappropriate treatment

Slide47

Peripheral nerve injury: informed consent

Now subject to MontgomeryShould be discussed in detail if the proposed operation puts a named nerve at more than a remote risk of damage e.g.:Excision of lump from posterior triangle of neckFracture fixation / removal of metalworkDiscectomy / spinal decompressionExcision of lump from or close to a nerve

Etc.

Discussion

should be

clearly recordedSlide48

Intraoperative PNI need not be negligent

“It must be accepted that despite careful surgery nerve injury during operation may occur. Recognition and prompt remedial action after the event are the keys.”British Orthopaedic Association ‘Blue Book’ 2011Slide49

Iatrogenic PNI: Conclusions

Properly informed consent more important than everA thorough knowledge of the local anatomy reduces the risk of inadvertent nerve damageIdentify any PNI promptlyDocument neurology accuratelyDiscuss situation with patient

Discuss with / refer to an expert earlySlide50

Iatrogenic PNI: Conclusions

Inadequate consentAvoidable damage to trunk / sensory nervesDelay in diagnosis /missed diagnosisDelay in referral to expertDelay in treatmentInappropriate treatmentSlide51