Peripheral Nerve Injury: Part 1. The scale of the problem, & injury classification.

Mr Will Eardley
MSc PgCertMedEd DipSEM(UK&I) MD FRCSEd (Tr&Orth)
Consultant Orthopaedic Trauma and Limb Reconstruction Surgeon
Research Associate, University of York CTU | Honorary Associate, University of Teesside
South Tees Hospitals NHS Trust

Orthopaedic surgery is the most common cause of iatrogenic peripheral nerve injury requiring treatment. Every orthopaedic surgeon fears this complication. Thereafter the path towards the eventual outcome is an emotive one for both the patient and the team responsible.

Blame, presumption of poor practice and anxiety permeate the condition. When discovered post-surgically, lack of clarity often exists between causation in the operating theatre, the Emergency Department, or a poorly-documented but perhaps evolving primary injury.

Bonney (1997) felt that the term iatrogenic did not go far enough in characterizing who or what had done harm. Writing in ‘Iatropathic lesions of peripheral nerves’(1997) Bonney felt ‘ The time may have come for that term to be replaced: ‘iatrogenic’ means ‘doctor producing’ rather than ‘produced by a doctor’, just as ‘osteogenic’ means ‘bone-producing’ and ‘carcinogenic’ means ‘cancer-producing’.

The term preferred and illustrative of issues around placing responsibility firmly with the surgeon is ‘iatropathic’ – to signify damage done by a doctor.

To place nerve injury of this nature in perspective, characterizing where iatropathic injury sits amongst global nerve trauma is essential. Injury as a result of clinical action accounts for around 17% of all nerve trauma. Of this population, the vast majority (94%) occur in some way due to a procedure in a surgical environment. Keeping with proportions, an indicator of the scale of impact can be seen from the fact that iatropathic nerve injury comprises 16% of all medicolegal cases.

Around the time of the procedure, injury is not limited to the surgeon’s blade or retractor. In addition to direct surgical insult, pressure from positioning, or tourniquet may cause harm. Equally, direct injury to the nerve either through nerve block procedure or injection of noxious substance contributes to the injury burden.

Focusing on the surgical procedure, Carter et al. (2020) have introduced a specific classification relating to iatropathic nerve injury.

Type I injuries are those occurring in an operation where the nerve ‘is not the target of the treatment’. Peripheral nerve injuries in orthopaedic practice are predominantly of this type. An example of a Type I surgical nerve injury therefore would be a closed humeral fracture with no pre operative radial nerve injury signs that undergoes surgery and a nerve laceration occurs.

A Type II injury is one where the ‘nerve was the target of the procedure but no repair or harvest intended’. Surgeons dealing with upper limb injuries may see these types of injury. An example would be trauma to the median nerve during carpal tunnel decompression or cubital tunnel decompression at the elbow.

The Type III injury is encountered when the ‘nerve was targeted for the repair of another nerve’ an example being nerve transfer or grafting with complications. This is uncommon.

Having considered the background and quantified the scale and description, the next post will look at outcomes related to common orthopaedic scenarios leading to these nerve injuries. These will be reviewed fracture by fracture.