understanding the importance of nerve protection

When surgeons embrace nerve protection as a part of their algorithm in the OR, they give their patients a better chance of functional recovery and improved quality of life.

why nerves need protection after an injury

Because nerve damage can start from the inside out, an injury isn’t always obvious.

When a traumatic injury occurs, nerves near the site of impact may remain intact and appear outwardly normal. But damage often happens within the nerve or to the tissue surrounding it. Stretching and compressive forces of an injury can cause nerves to experience endoneurial and perineurial damage. In addition, a nerve that appears normal after trauma may become injured over time due to compression from the buildup of scar tissue in the environment surrounding the nerve.

In a thermally injured tissue bed, Axoguard HA+ Nerve Protector acts as a physical barrier and protects the nerve from fibrotic tissue

These injuries are sometimes referred to as non-transected nerve injuries (NTNIs). While the nerve may not have been transected, they can lead to the same pain and loss of function if left untreated. One study demonstrated that 69% of hand trauma patients whose nerves were noted to be normal or non-injured at the time of surgery presented signs of impaired nerve function at follow-up.1

Muscle injury: no wrap

Muscle Injury No Wrap

Muscle injury: with wrap

Muscle Injury with wrap

injured nerves in continuity still need intervention
Despite complete nerve continuity preservation, stretching and compression injuries can result in total loss of both motor and sensory nerve functions. This presents a surgical dilemma due to a lack of obvious repair needed—despite an injury being present.1

77% of patients with hand/wrist trauma and subsequent nerve symptoms are not experiencing full nerve recovery1

 

considering acute versus chronic inflammation

When a nerve is injured, it goes through a healing process in which acute inflammation plays a critical role in helping to repair the damaged tissue and restore homeostasis.

However, when there is ongoing irritation, such as a nerve rubbing against a plate or tethering due to scar tissue formation, that inflammation can become chronic and lead to additional scarring and pain. These irritations can occur because of damage to the tissue surrounding the nerve, or other factors unique to the patient’s injuries and anatomy.

Types of inflammation in nerve repair

Acute

A part of the normal physiology

Can become chronic with stress or inflammatory triggers in the microenvironment

Chronic

Prolonged inflammation

Can be caused by complex injury or successive acute injuries

May lead to soft-tissue tethering

 

why nerve protection matters

Nerve protection preserves and protects nerves that may not have been cut or have obvious damage by helping to mitigate soft tissue attachment and the impact of negative changes of the surrounding tissue environment. Introducing a barrier between the non-transected nerve and its surrounding soft tissue creates a safer space for proper nerve regeneration.

In one study, with the absence of direct nerve treatment only 23% of patients experienced full recovery based on qualitative sensory assessments.1

what’s at risk when nerves aren’t protected1,2

  • Scarring
  • Soft tissue attachment
  • Compression
  • Tethering
  • Edema
  • Reactive swelling
  • Further injury
  • Limited mobility
  • Decreased sensation
  • Incomplete recovery

how nerve protection helps

  • Provides a protective barrier to separate the nerve from the surrounding tissues,2,3 minimizing the potential for soft tissue attachments to allow the nerve to glide2
  • Reduces the likelihood of traumatized nerve becoming inflamed by serving as a barrier to inflammatory cells
  • Reduces the potential for nerve tethering and neurostenalgia
  • Reduces the likelihood of collagen deposition (internal scarring) in the nerve
 

taking control of the healing process

When there is trauma to structures adjacent to nerves, this not only hints at the force and mechanism of the injury’s origin but is highly indicative of the likelihood that nerves were involved. When surrounding structures such as ligaments and tendons are torn or transected, it is likely that the adjacent nerve is as well.1

This common correlation highlights the importance of considering the pattern of injury when evaluating for possible nerve involvement.

provide a barrier to inflammatory cells to avoid soft tissue attachment

Adding a barrier between the non-transected nerve and the surrounding soft tissue gives the nerve a better chance at recovery by minimizing the possibility of soft tissue attaching to it.

Minimizing soft-tissue attachment is essential because a nerve requires a healthy surrounding tissue bed to allow free nerve gliding.4

the right biomaterial..not all barriers are created equal


build a targeted barrier between nerves and soft-tissue attachment

Scar tissue formation in the vicinity of a peripheral nerve can lead to damage, such as compression, ischemia, and impaired glide and tether, which can result in neurostenalgia. Neurostenalgia is a neuropathic pain that results from continuing irritation of an anatomically intact nerve by a noxious agent.4

healthy normal nerve fibers

healthy normal nerve fibers

axons: red | myelin: green

smaller fibers: nerve injury

smaller fibers: nerve injury

axons: red | myelin: green

nerve protection promotes healthy axon growth

With proper nerve protection, healthy, normal axons can grow more easily. As shown in the left image above, the red staining represents the axons present in a healthy, normal nerve. Conversely, on the right, the nerve that wasn’t protected shows little to no visible staining because those axons have been damaged and aren’t there.5

When nerves are properly protected, less collagen buildups occur. Collagen presence is often indicative of scarring.6

Healthy

healthy epineurium and fascicles

cells: red | collagen: blue

Excess intraneural collagen

excess intraneural collagen

cells: red | collagen: blue

minimize collagen deposition

cells: red | collagen: blue

 

connecting mechanism of injury to nerve involvement

Understanding where and why non-transected nerve injuries present themselves, especially in acute hand and wrist trauma, can help in early intervention. And early intervention can help maximize functional recovery.

In the study “Nerves in Continuity Following Hand Trauma: A Descriptive Report,” both injury cause and type had a direct relation to the occurrence of nerve involvement or damage. For example, tendon and ligament injuries correlate with an increased chance of nerve involvement (81.8% and 83.3%, respectively).1

  • injury type
  • injury mechanism

percentage of patients with abnormal nerve symptoms by injury type1

66.67%
Fracture
81.8%
Tendon
83.3%
Ligament
50%
Dislocation
50%
Muscle
100%
Vascular

Tendon and ligament injuries correlate with an increased chance of nerve involvement (81.8% and 83.3%, respectively).1

percentage of patients with abnormal nerve symptoms by injury mechanism1

40%
Motor vehicle collusion
75%
Saw laceration
100%
Firearm / blast
100%
Machinery / crush / compression
50%
Sharp laceration

Blast injuries (such as from a firearm), crush injuries and compression injuries (such as from machinery) are strongly associated with nerve involvement.1

nerves in continuity following hand trauma: a descriptive report–study design

The study featured a retrospective cohort of 20 patients with hand or wrist trauma that presented at the initial surgery with intact nerves. Of these patients, 75% had signs of impaired nerve function either before surgery or at their first post-surgical follow-up. Only 23% experienced full sensory recovery and 57% had full recovery from pain without direct nerve treatment.1

 

when to incorporate nerve protection

Ensuring patients have the best possible chance for optimal recovery is always the goal. Because of this, protection should be top of mind whenever performing cases where a nerve is involved.

When it comes to nerves, don’t wait to see what transpires after acute surgical healing. Proactive protection sets patients up for long-term functional recovery.

nerve protection is beneficial for:

hardware-based procedures

Study results have clearly demonstrated the presence of marked inflammation and tissue reaction in the soft tissue covering stainless steel and titanium plates. A majority of the tissues around metal implants had discoloration and metal fragments within the tissues and macrophages. This is shown to cause immune-inflammatory reactions.7 When near a plate, nerves can rub against the plate surface and incur mechanical irritation directly.

fractures

In one study, 67% of hand fractures presented alongside signs of associated nerve injuries.1 For humerus fractures, fracture location is an important indicator of the probability of a nerve issue. Middle and middle-distal humerus fractures have been most commonly associated with nerve injury.8

The radial nerve is most likely to be damaged in humerus fractures. Especially those that have a lateral displacement of the distal fracture segment, as the nerve is tethered to the bone and cannot withstand the forces applied to it as a result of the displacement.9

radial nerve palsy likelihood based on fracture type and location8

  • Transverse: 21.2%
  • Spiral: 19.8%
  • Oblique: 8.4%
  • Comminuted fractures: 6.8%

staged and recurrent procedures

Postoperative scarring is the most significant cause of recurrent carpal tunnel syndrome (CTS). In addition, revision surgery is often associated with increased technical difficulty due to significant scarring of the nerve and its surrounding soft tissue.10

Although some reports provide good results with neurolysis alone, many favor providing vascularized tissue or nerve wraps after rerelease to prevent the scarring process. Data suggests nerve protection could provide significant reduction in symptom severity and function severity scores after 1 to 2 years.10

other procedure types

Nerve protection can provide an ideal solution across surgical categories including decompressions, other trauma, head and neck, and iatrogenic injuries.

The following procedures may benefit from using nerve protection, especially Axoguard HA+ Nerve Protector™:

  • Spinal accessory nerve after neck dissection
  • Radial nerve laying on metal plating for humeral shaft and olecranon fractures
  • Ulnar nerve during a revision cubital tunnel release or transposition
  • Median nerve through the carpal tunnel in revisions
  • Traumatic injuries of the sciatic nerve
  • Common peroneal nerve after tibial plateau fractures
  • Tibial nerve through tarsal tunnel in revisions
 

axogen solutions for nerve protection

Protecting damaged nerves during the healing process is important for proper healing and consistent patient outcomes. Learn how our solutions help minimize neuroma formation and protect nerves from soft tissue attachments and mechanical stimulation.

Remodeling extracellular matrix for long-term protection with a short-term gel coating for enhanced nerve gliding and minimization of soft tissue attachments.

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Axoguard® Nerve Protector

Extracellular matrix that remodels to protect injured nerves and reinforce nerve reconstructions.

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references

  1. Pereira DE, et al. Nerves in Continuity Following Hand Trauma: A Descriptive Report. Hand (N Y). 2023;18(1_suppl):126S-132S. doi:10.1177/15589447211064362
  2. Kokkalis ZT, et al. Assessment of processed porcine extracellular matrix as a protective barrier in a rabbit nerve wrap model. J Reconstr Microsurg. Jan 2011;27(1):19-28. doi:10.1055/s-0030-1267379
  3. Thomson SE, et al. Bioengineered nerve conduits and wraps for peripheral nerve repair of the upper limb. Cochrane Database Syst Rev. 2017;2017(3):CD012574. doi:10.1002/14651858.CD012574.pub2
  4. Jordaan PW, et al. Management of the scarred nerve using porcine submucosa extracellular matrix nerve wraps. J Musculoskelet Surg Res. 2019;3:128-133.
  5. Axogen data on file.
  6. Axogen data on file.
  7. Voggenreiter G, et al. Immuno-inflammatory tissue reaction to stainless-steel and titanium plates used for internal fixation of long bones. 2003;24(2):247-254. doi:10.1016/S0142-9612(02)00312-5
  8. Shao YC, et al. Radial nerve palsy associated with fractures of the shaft of the humerus: a systematic review. J Bone Joint Surg Br. 2005;87(12):1647-1652. doi:10.1302/0301-620X.87B12.16132
  9. ‌Bounds EJ, Frane N, Jajou L, Kok SJ. Humeral Shaft Fractures. In: Treasure Island (FL): StatPearls Publishing; March 1, 2023.
  10. Saffari TM, et al. Compression Neuropathies. Hand Clinics. 2023;39(3):389-401. doi:https://doi.org/10.1016/j.hcl.2023.02.009