Peripheral nerve injuries (PNIs) are an often-overlooked but significant consequence of complex orthopaedic trauma. They add another layer of complexity to rehabilitation, influencing recovery trajectories, delaying functional outcomes, and often causing distress to our clients. Understanding how to assess and manage these injuries is essential for optimising long-term recovery.
Prevalence and Mechanisms of Injury
Peripheral nerve injuries are common in the context of high-energy trauma and complex orthopaedic cases. They may result from direct trauma (e.g. laceration, traction), secondary to fracture displacement, compartment syndrome, or surgical intervention. Procedure related injuries during surgery such as ORIF or joint replacement are also a contributing factor.
Common sites of injury include:
- Upper limb: radial, ulnar, and median nerves (especially in humeral or supracondylar fractures)
- Lower limb: common peroneal nerve (frequently in tibial or fibular fractures)
- Plexus-level injuries: often seen with clavicular fractures or shoulder dislocations
Pathophysiology: Understanding Nerve Injury
Peripheral nerves consist of axons supported by Schwann cells and connective tissue layers (endoneurium, perineurium, epineurium). These structures are crucial in both the function and repair of nerves.
Seddon’s and Sunderland’s classification systems describe the spectrum of injury severity:
Neurapraxia: focal demyelination with intact axons; good prognosis
- Neurapraxia: focal demyelination with intact axons; good prognosis
- Axonotmesis: axonal disruption with preserved connective tissue; regeneration possible
- Neurotmesis: complete disruption of axons and connective tissue; poor prognosis without surgery
In crush and transection injuries, Wallerian degeneration initiates the clearance of damaged axons. Schwann cells dedifferentiate and proliferate, helping to create an environment that supports nerve regrowth by expressing neurotrophins like NGF, BDNF, and GDNF (Gordon & English, 2016).
Nerve Regeneration and Prognosis
Axonal regeneration is slow and occurs at an average rate of 1–3 mm/day, although this can vary based on injury type, client age, comorbidities, and the anatomical location. Early regeneration occurs via collateral sprouting, but more severe injuries require axonal regrowth from the proximal stump.
If surgery to repair the nerve is delayed, the cells that support nerve regrowth (Schwann cells) start to break down, and the signals that help the nerve grow become weaker (Gordon et al., 2016. This makes it harder for the nerve to heal. Keeping the area where the nerve needs to regrow healthy is very important, because if it stays without a nerve for too long, recovery is less likely.
Key indicators of regeneration include:
- Advancing Tinel’s sign.
- Return of voluntary movement or EMG activity.
- Re-emergence of sensation.
Surgical Management of Peripheral Nerve Injuries
Surgical repair options include:
- Neurolysis: freeing the nerve from scar tissue.
- Nerve grafting: bridging a nerve gap.
- Nerve transfers: redirecting functional nerves to restore priority functions.
- Tendon transfers: substituting lost muscle function when nerve recovery is incomplete.
As Physiotherapists we need to understand post-surgical precautions and timelines. Immobilisation protocols, scar desensitisation, and protection of repair sites are key priorities in early phases.
Physiotherapy in the Rehabilitation Pathway
Acute Phase
- Protect nerve repair sites.
- Preserve joint ROM.
- Manage pain and swelling.
- Educate clients and carers about prognosis and pacing.
Intermediate Phase
- Facilitate active movement as reinnervation occurs.
- Desensitisation techniques for sensory nerves.
- Functional splinting and orthotic support.
- Begin motor retraining and progressive loading.
Long-Term Rehabilitation
- Task-specific training.
- Strengthening reinnervated muscles.
- Address compensatory movement patterns.
- Support return to meaningful activity!
Adjuncts to Physiotherapy
Electrical Stimulation (ES)
Electrical stimulation is an evidence-supported adjunct that promotes peripheral nerve regeneration and improves functional recovery. Traditional muscle stimulation parameters may be inadequate to address denervated muscle, but research suggests that new protocols can be of benefit:
- Brief low-frequency ES (typically 20 Hz for one hour) has been shown to significantly accelerate axonal outgrowth and improve functional reinnervation in both animal and human models (Al-Majed et al., 2000; Gordon & English, 2016).
- ES activates the expression of growth-associated genes such as BDNF, GAP-43, tubulin, and actin, enhancing the intrinsic growth capacity of neurons (Al-Majed et al., 2004; English et al., 2007).
- Electrical stimulation helps both nerve and support cells release proteins that encourage healing by upregulating neurotrophic factors in both Schwann cells and neurons, driven by calcium influx and CREB-mediated gene transcription (Gordon & English, 2016). This happens because it triggers signals inside the cells that turn on growth-related genes
- The use of ES may be especially important in delayed nerve repair, where chronic axotomy and denervation would otherwise reduce regenerative potential (Gordon et al., 2020).
Specific Parameters for Denervated Muscle:
- Pulse Duration: Long pulses of 20 – 100 ms are typically required due to the high activation threshold of denervated muscle fibres (Gordon, 2020).
- Frequency: Low-frequency stimulation around 0.5–1 Hz for denervated muscle has been used to prevent atrophy, but frequencies up to 20 Hz are explored for promoting regeneration in some models (Willand et al., 2016).
- Amplitude: Must be high enough to produce visible contraction in denervated muscle; this can vary by individual but typically ranges from 20–100 mA.
- Waveform: Triangular monophasic or biphasic pulses are frequently used in clinical settings for denervated muscle due to their gradual current ramp-up, which can improve comfort and reduce the risk of sudden muscle contractions. This contrasts with rectangular pulses that have a sharp onset. While both waveforms are effective, triangular currents are often preferred during the early stages of reinnervation or chronic denervation when tolerability is critical and to reduce overflow.
- Duty Cycle: Often includes long rest periods (e.g. 1:4 or 1:5 ratio) to reduce fatigue in reinnervating muscle.
Key considerations:
- Stimulation should begin early, ideally within days post-injury, to support muscle viability and Schwann cell support.
- Long-term daily stimulation may be needed but remains a logistical and compliance challenge.
- Overuse should be avoided to prevent fatigue or tissue irritation.
- Combination with exercise has shown additive effects in some studies (Asensio-Pinilla et al., 2009).
- A systematic review (ElAbd et al., 2022) confirmed that low-frequency ES (1–20 Hz) applied during or soon after surgical repair enhances sensory and motor recovery, with improvements in tactile discrimination, pressure detection, and EMG measures of muscle reinnervation. Parameters used included 1–20 Hz, pulse widths from 0.1–0.8 ms, and amplitudes up to 30 V depending on tolerance.
Surface Electromyography (sEMG)
sEMG provides both diagnostic and therapeutic benefit:
- Identifies early voluntary muscle activity before visible movement, critical in monitoring reinnervation progress (Gordon, 2020).
- Enables biofeedback-based motor re-education by visually or audibly reinforcing weak motor signals, improving patient engagement and neuromuscular control (Dursun & Dursun, 2004).
- Helps determine the focus of strengthening and compensatory strategies by localising recovering muscles.
- Particularly effective when combined with functional tasks to promote cortical reorganisation and task-specific learning.
Summary and Key Takeaways
- Peripheral nerve injuries significantly affect rehabilitation progress after complex trauma.
- Physiotherapists play a crucial role in identifying, monitoring, and managing these injuries.
- Surgical repair success depends on timely intervention and coordinated post-op rehab.
- Adjuncts like ES and sEMG can support recovery when used appropriately.
- Understanding neurobiology helps physiotherapists tailor interventions more effectively.
Further Reading and Resources
- Menorca RMG et al. (2015). Peripheral Nerve Trauma: Mechanisms of Injury and Recovery
- Gordon T & English AW (2016). Strategies to Promote Peripheral Nerve Regeneration: Electrical Stimulation and Exercise. Eur J Neurosci, 43(3):336–350.
- Gordon T (2020). Electrical Stimulation After Peripheral Nerve Injuries in Animal Models and Humans. Neurosci Lett, 740:135435.
- ElAbd R et al. (2022). Role of Electrical Stimulation in Peripheral Nerve Regeneration: A Systematic Review. Plast Reconstr Surg Glob Open, 10:e4115.
- Dursun N & Dursun E (2004). Electromyographic biofeedback in rehabilitation. Turk J Phys Med Rehab, 50:62–67.
- Willand MP et al. (2016). Electrical stimulation for promoting peripheral nerve regeneration. Muscle Nerve, 53(5): 780–787.
- NICE & BOA trauma rehabilitation guidelines