What are the timing and guidelines for peripheral nerve injury (laceration wound) repair, including options for delayed repair if the nerve was not sutured at the time of injury?

Peripheral Nerve Laceration Repair: Timing and Management

Immediate Primary Repair is Optimal for Clean Sharp Lacerations

For clean, sharp peripheral nerve lacerations without tissue defect, immediate primary repair using epineurial sutures provides the best functional outcomes and should be performed at the time of injury. 1

Timing Guidelines Based on Injury Characteristics

Clean Sharp Transections

• Perform immediate primary repair for clean-cut nerve injuries without defect using trunk-to-trunk coaptation with epineurial sutures 1
• In median and ulnar nerves where motor and sensory fascicles are separated, perform fascicular dissection with coaptation of fascicle groups 1
• This approach offers optimal results even in severe lesions when performed in centers with appropriate facilities 1

Contaminated or Blunt Injuries

• Perform delayed primary repair at 2-4 weeks if nerve stumps appear bruised or the wound is contaminated 2
• Tack the nerve stumps to adjacent tissue planes to prevent retraction, but avoid approximation under tension which damages stumps and creates larger defects 1
• This allows time for wound healing and demarcation of viable tissue 1

Nerve Injuries with Tissue Defect

• Avoid primary nerve grafting in acute trauma due to risk of graft loss if complications occur 1
• Plan early secondary repair during the third week or later when local conditions permit 1
• Perform plastic surgical procedures first to eliminate constricting scars and provide optimal soft tissue environment 1

Management When Primary Repair Was Missed

Closed Injuries or Injuries in Continuity

• Observe clinically and electrically for 2-5 months depending on the nerve involved and mechanism of injury 2
• If no reversal of neurologic deficit occurs by 3-4 months, proceed with surgical exploration 3, 4
• Use intraoperative nerve action potential (NAP) testing to guide decision-making during exploration 2

Time-Critical Window for Motor Recovery

• The quality of motor recovery decreases steadily after 6 months delay from injury 1
• Late secondary repairs or reoperations should be performed within this 6-month window 1
• Nerve regeneration occurs at approximately 1 inch per month, limiting recovery potential to injuries where the distance from injury to innervated muscle is less than 18 inches 3
• Recovery remains possible for up to 18 months following injury, though outcomes worsen with longer delays 1, 3

Surgical Decision-Making at Delayed Repair

• After exploration and stump preparation, decide between direct suturing versus nerve grafting 1
• If nerve stumps cannot be coapted easily after very limited mobilization and slight flexion, use a nerve graft 1
• Avoid excessive mobilization that compromises blood supply 1

Special Considerations for Delayed Presentation

Very Late Presentations (>6 months)

• Nerve repair is still indicated if sensibility restoration is the main functional objective, as sensory recovery can occur even after prolonged delays 1
• Combine nerve repair with tendon transfer or capsulorrhaphy in long-standing cases to optimize functional outcomes 1
• In elderly patients or after particularly long intervals, consider only palliative surgery 1

Nerve Gaps

• For gaps <2 cm, neurological recovery with grafting is moderate 5
• For gaps 2-4 cm, recovery is generally poor 5
• For gaps >4 cm, recovery is limited to non-existent 5

Critical Pitfalls to Avoid

• Never approximate nerve stumps under tension in acute setting—this damages tissue and creates larger defects requiring grafting 1
• Do not delay exploration beyond 4 months in closed injuries without spontaneous recovery 4
• Avoid primary nerve grafting in contaminated wounds or when complications are likely 1
• Do not wait beyond 6 months for motor nerve repairs as motor recovery quality deteriorates significantly 1

Combined Injuries

When nerve and tendon injuries coexist (e.g., carpal tunnel), perform nerve repair as a later procedure to avoid adhesions between repaired tendons and nerves 1