Nerve Grafting

Nerve Gaps and Grafting After Nerve Injury

When a nerve is completely severed, the elastic tissue within the nerve causes the two cut ends to retract from each other, creating a nerve gap. If the cut is clean and surgery is performed without undue delay, a primary repair can often be achieved by carefully mobilising the cut ends to restore continuity.

However, when there is substance loss due to trauma or the need to remove damaged tissue (debridement), a nerve defect is encountered. In these cases, attempting to reconnect the nerve directly can cause too much tension at the repair site, which has been shown in both clinical and experimental studies to lead to poor outcomes. Therefore, a conduit or a graft is needed to bridge the gap.

Options for Nerve Grafts/Conduits

There are two main categories for nerve grafting or conduits: autologous (from the patient) or off-the-shelf products.

Nerve Graft vs. Conduit

The nerve autograft remains the gold standard for nerve grafting, as it provides the best results. However, it comes with the risk of donor site morbidity—damage or loss of function at the site from which the nerve is harvested. Processed nerve allografts and off-the-shelf conduits offer alternatives that avoid this issue, though allografts are derived from cadaveric donors, which may not be acceptable to all patients.

Factors Influencing the Choice of Graft or Conduit

The choice of whether to use an autologous graft, processed allograft, or an off-the-shelf conduit depends on several factors:

• Length of the nerve defect/gap: Longer gaps may require specific types of grafts or conduits.
• Type of nerve injured: Sensory, motor, or mixed nerves may need different approaches.
• Size/diameter of the nerve injured: Larger nerves may require more robust conduits.
• Patient preferences: Some patients may prefer to avoid products derived from cadaveric or animal sources.
• Cost considerations: The price of off-the-shelf options or allografts may influence decision-making.

Prerequisites for Successful Nerve Grafting

To achieve the best outcomes with nerve grafting, the following conditions must be met:

• Skeletal stability
• Healthy tissue bed
• Healthy nerve ends
• Tension-free neurorrhaphy (nerve repair)
• Adequate soft tissue coverage
• Appropriate timing for the procedure

Key Message

A nerve defect can arise due to:

• Traumatic loss of nerve tissue
• Debridement of damaged nerve ends
• Delayed repair, leading to retraction of the nerve ends

Attempting a tight repair with excessive tension leads to poor results, so it is essential to ensure a tension-free repair by using appropriate grafts or conduits.