Post-operative Nerve Injury

Introduction

Orthopaedic surgery is the most common cause of iatrogenic nerve injury but its incidence is not widely documented. This is particularly lacking in foot and ankle literature. It is important to carefully examine and document the status of peripheral nerves prior to operative intervention, as well as understand the pre-clinical study of nerve injury and the evaluation and treatment options for iatrogenic nerve injuries.

 

Aetiology

  • Missed pre-operative injury from index trauma.
  • Direct sharp injury during surgery (complete or partial transection).
  • Surgeons must appreciate anatomic variations along the course of peripheral nerves to minimise the risk of iatrogenic nerve injury during dissection.
  • Implants add an additional risk factor:
    • plates may crush / entrap / irritate nerves.
    • drill bits/screws/ k-wires may penetrate / avulse nerves.
    • increased risk with percutaneous or “minimally invasive” techniques.
  • Indirect injury/traction during retraction or during insertion or removal of implants.
  • Thermal injury secondary to exothermic reaction of cautery devices or cement.
  • Accidental resection if mistaken for another structure e.g. tendon/vessel.
  • Peri-operative injury from external compression and non-surgical treatments:
    • casts/splints / dressings.
    • injections.
    • patient positioning during surgery

 

Pathophysiology

Nerve macrostructure

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Nerve injury occurs on a spectrum of severity (Seddon 1942, modified by Sunderland 1951) and is directly proportional to recovery potential.

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Additionally, axonal injury with discontinuity causes a neurotrophic cascade which results in sprouting proximal nerve axons which can form a neuroma.

 

Most common causes of specific nerve injuries

  • Superficial peroneal nerve: lateral approach to fibula, anterolateral ankle arthroscopy portal
  • Sural nerve: posterolateral approach to ankle, Achilles repair, lat approach to calcaneus, posterior arthroscopy portals
  • Saphenous nerve: medial ankle approach /ORIF, anteromedial ankle arthroscopy portal
  • Tibial nerve: total ankle replacement
  • Medial dorsal cutaneous nerve: hallux valgus surgery

 

Presentation

History may include numbness/paraesthesia in peripheral nerve distribution. Severe, unremitting neuropathic pain is suggestive of entrapment/strangulation. Hyperalgesia and allodynia suggest transection or neuroma formation.

Examination should include:

  • muscle bulk/atrophy and MRC grading
  • joint range of motion
  • sensory nerve distribution including 2-point discrimination and Tinel's test
  • symptoms suggestive of autonomic dysfunction (hair loss, anhidrosis)

 

Investigations

  • X-rays: orthogonal imaging to assess for aberrant metalwork/implants or fracture gapping
  • Ultrasound: visualises topography/continuity of nerve as well as pathological changes in muscle from denervation
  • MRI: visualises topography/continuity of nerve but may be affected by metal artefact
  • EMG: useful 3-4 weeks post injury for showing denervation changes; serial studies can show regeneration

 

Management

Non-operative

  • Gabapentin / pregabalin and tricyclics: level 1 evidence in treating neuropathic pain
  • Desensitisation therapy: limited evidence but favourable risk benefit profiles
  • Peripheral nerve stimulation: limited evidence, not recommended in guidance

Operative

  • Primary repair should be attempted if transection noted intraoperatively
    • Major nerve: microscopic end to end repair without excessive tension, ideally by surgeon familiar with peripheral nerve injuries
    • Small, sensory branches: ends left or buried to reduce neuroma formation
  • Delayed presentation or segmental loss usually managed with grafting/transfer
    • Autologous: sural nerve most commonly used, also saphenous and medial antebrachial cutaneous
    • Decellularised allografts have been described but little evidence, mostly upper limb
  • Neuroma excision
  • Management plan based on age, co-morbidities, time from injury, neurological deficit

 

Outcomes

Dependent on location and type of lesion, patient factors and time to intervention.

Minimal good quality data, particularly for F&A but largest series suggests only 24% achieved a “very good” outcome (i.e. patient experiencing considerably less pain and/or improvement in motor or sensory nerve function).

 

Conclusions

Iatrogenic nerve injuries are more common than we think. Good examination and documentation are essential. Nerve injuries suspected in the acute postoperative period should be evaluated for any reversible causes and addressed. The Seddon-Sunderland classification is useful in identifying prognosis and management. Early identification and management are crucial to maximise outcomes.

 

References

  • Pulos N et al. Management of Iatrogenic Nerve Injuries. J Am AcadOrthop Surg 2019;27:438-48
  • Ramachandran M. Basic Orthopaedic Sciences, 2nd edition 2017
  • Hendrickson NR et al. Treatment of Postsurgical Neuroma in Foot & Ankle Surgery. F&A Orthop 2018; 1-8
  • Bai L et al. Natural History of Sensory Nerve Recovery after Cutaneous Nerve Injury following Foot and Ankle Surgery. Neural Regen Res 2015 10(1):99-103