Neurectomy refers to the surgical cutting and removal of a nerve to prevent pain sensation. [1] In horses, neurectomy is considered a salvage procedure, meaning it is a last resort only performed if no other treatments were effective. [2]

Veterinarians may recommend neurectomy in horses with long-term lameness issues, such as navicular disease or arthritis. [1] The two most common neurectomy procedures are performed on plantar/palmar digital and lateral plantar nerves.

Lameness resolves completely in the majority of neurectomized horses, with many horses remaining sound for several months after the procedure. However, neurectomized horses require close monitoring as they have a high risk for severe, life-threatening injuries.

It is important to note that neurectomy is a somewhat controversial procedure, particularly if the horse is expected to return to competition. The regulating bodies of some equestrian sports do not allow neurectomized horses to compete.

Horse owners must work closely with their veterinarian to determine if neurectomy is appropriate for their horse. Caretakers considering neurectomy are advised the procedure is usually only intended as a form of palliative care in otherwise unresolved cases of lameness.

Why are Neurectomies Performed on Horses?

Veterinary surgeons may recommend neurectomies in horses with chronic lameness issues, to allow them to return to some level of work or stay comfortable during retirement. [1]

Conditions that may benefit from neurectomy include: [2]

Neurectomy is an irreversible procedure with a high risk for complications, so most veterinarians only recommend the procedure if all other treatment options were unsuccessful. [2]

Before recommending a neurectomy procedure, the veterinarian numbs the nerve using local anesthetic. [1] This allows the veterinarian and owner to see the approximate effect that the neurectomy surgery will have on the horse’s lameness. [1]

The owner and veterinarian can use this information to determine whether a neurectomy procedure is appropriate for the horse. [1]

Types of Neurectomy

Neurectomies target the major nerves that provide pain sensation to the lower limbs. [2] The type of neurectomy performed depends on the cause and location of lameness. [2]

Some of the main types of neurectomies target the following nerves:

  • Palmar digital nerve
  • Plantar digital nerve
  • Lateral plantar nerve

Palmar/Plantar Digital Nerve

Neurectomy of the palmar digital nerve (front limbs) or plantar digital nerve (hind limbs) is the most common surgical treatment for navicular syndrome. [1] These nerves run along the back of the fetlock and into the hoof, and provide sensation to the sole, navicular area, and the coffin joint. [1]

Conditions treated using a palmar/plantar digital (PD) neurectomy include: [2]

  • Navicular syndrome
  • Navicular bone fractures
  • Coffin bone fractures
  • Collateral ligament injuries of the coffin joint

Procedure

The following contains detailed descriptions of surgical procedures on the nervous system, which may be sensitive for some horse owners. Reader discretion is advised.

There are several methods described for performing a PD neurectomy, and the method used depends on the surgeon’s preference and equipment availability. [1]

The main surgical techniques are: [3][4]

  • Simple transection: surgically cutting the nerve and removing a segment
  • Perineural capping: placing a cap over the end of a surgically cut nerve
  • Laser coagulation: causing damage to the nerve by overheating
  • Laser transection: cutting the nerve using a laser
  • Cryoneurectomy: using cold temperatures to damage the nerve

Studies show that simple transection is most effective, with reduced pain sensation for a longer period, and carries the lowest risk of neuroma formation. [3] Neuromas are extremely painful growths that can develop at the end of a severed nerve and are a common complication of neurectomy procedures. [1]

There are two main methods for performing simple transection, and the methodology chosen does not affect surgical outcomes. [5] These methods are the guillotine and pull-through techniques. [4]

The guillotine technique involves creating two long incisions on the back of the pastern to visualize the PD nerves. [6] The surgeon separates the nerve from the surrounding tissues and places it over a tongue depressor. [6] While pulling on the nerve, a scalpel blade cuts the portion of the nerve over the tongue depressor in a guillotine-like fashion. [6]

The pull-through technique is an adaptation of the guillotine technique that allows for smaller incisions. [7] The surgeon makes two small incisions at the top and bottom of the PD nerve along the back of the pastern to access the nerve. [7] The nerve is cut at the bottom of the pastern first, then the loose end of the nerve is pulled up through the top incision and removed. [7]

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Post-operative Care

Proper post-operative care is crucial to reduce the risk of neuroma formation. [1] Neuromas are an extremely painful growth that can develop at the end of a severed nerve. [1]

Horses typically require 30-60 days of stall rest or limited activity after surgery. [1] Stall rest appears to reduce the risk of neuroma formation, but current findings around this are anecdotal. [2]

Horses often require bandaging of the affected limbs for up to 30 days after surgery. [1]

Prognosis

Between 65-70% of horses show no symptoms of lameness after neurectomy. [2] These results typically last for 12 to 18 months, depending on the individual horse. [2]

Many horses can return to their previous athletic performance level during this time, but it is important to note the procedure is not expected to last long-term. [1][8] Further, some of the governing bodies in equestrian sport require disclosure of neurectomy results and do not allow neurectomied horses to compete.

Complications

PD neurectomy has several potential complications that can arise long after the surgical procedure. [1] Complications include neuroma formation, traumatic injuries to the lower limb, and regrowth of the PD nerve. [1][2]

Neuroma Formation

Neuromas are painful growths that develop at the end of a damaged nerve. [1] Neuromas occur in between 5-13% of horses after PD neurectomy. [4] In some cases, neuromas develop months after the surgery. [2][8]

Neuromas may respond to local injections of anti-inflammatory medications, such as corticosteroids. [2] In some cases, a second neurectomy procedure is necessary to remove the neuroma. [2]

Traumatic Injuries to the Lower Limb

Due to the loss of sensation, horses with PD neurectomies are prone to injury in their lower limbs. [2] These injuries often require euthanasia due to their severity. [2][9]

Reported injuries include: [2][9][10]

  • Rupture of the deep digital flexor tendon
  • Luxation (separation) of the coffin joint
  • Fractures of the navicular bone
  • Sloughing of the hoof capsule

Horses with PD neurectomies also require careful monitoring for hoof injuries. [2] Without feeling in their hooves, horses do not show lameness when injuries such as hoof abscesses or punctures of the sole by an object occur. [2]

Left unnoticed, these injuries can cause widespread infections within the hoof capsule, including infections of the coffin bone. [2][7]

In one study following neurectomized horses, 3 out of the 41 horses (7%) required euthanasia due to a traumatic injury within 1 year of surgery. [7]

One horse developed an undetected foot abscess that led to bone infection, one developed a navicular bone fracture, and the other ruptured their deep digital flexor tendon. [7]

Nerve Regrowth

Some horses develop lameness after a PD neurectomy due to regrowth of the nerve, returning pain sensation to the affected area. [2] If lameness still resolves with a local anesthetic block, a second neurectomy procedure may be beneficial. [2]

In these cases, the second neurectomy procedure is typically less effective, due to the reforming nerve producing numerous branches that may be difficult for the surgeon to identify. [2]

Deep Branch of the Lateral Plantar Nerve

The lateral plantar nerve is a branch of the tibial nerve which provides sensation to the lower hind limb. [11] Horses with proximal suspensory desmitis (PSD) may develop irritation of the deep branch of the lateral plantar nerve, which runs close to the suspensory ligament. [12]

Most horses with proximal suspensory desmitis in the hind limbs do not make a full recovery and continue to have mild to moderate lameness. [11]

Some veterinarians believe that continued irritation of the deep branch of the lateral plantar nerve (DBPLN) may contribute to lameness even after the suspensory ligament heals. [11][12] Neurectomy of the DBPLN may help resolve lameness in these cases.

Procedure

The procedure for DBPLN neurectomy is a combination of neurectomy and fasciotomy, cutting of connective tissue. [12]

For the fasciotomy portion of the surgery, the surgeon cuts through two layers of fascia, supportive connective tissue surrounding the muscles. [13] This procedure allows the surgeon access to the DBPLN. [13]

In addition to allowing the surgeon to access the nerve, fasciotomy has the additional benefit of relieving tension in the area. [13] This can reduce pressure on the suspensory ligament, DBPLN, and bones that may cause irritation and lameness. [12]

Once the surgeon accesses the DBPLN, the nerve is separated from the surrounding tissues and cut using a guillotine technique. [13]

Post-operative Care

Horses typically require 2-3 weeks of stall rest and bandaging, followed by a slow return to exercise over a 2–6-week period. [12] Horses that have chronic injuries to their suspensory ligament often have atrophy of the gluteal muscles and require more rehabilitation before returning to trot or canter. [12]

Some veterinarians recommend a follow-up ultrasound before returning to canter work. [12] This ultrasound ensures that the suspensory ligament is healing appropriately and that the horse is sound enough to continue exercise. [12]

Prognosis

The prognosis of DBPLN neurectomy is good, with studies showing that around 80-90% of horses can return to their previous level of performance after surgery. [11]

Horses that have a straight hock conformation or hyperextension of the fetlock due to their suspensory injury have a poorer prognosis. [12][14] One study found that none of the horses with this conformation became sound after DBPLN neurectomy. [14]

Some veterinarians avoid performing neurectomy in these horses, as studies show these conformational traits increase the risk of suspensory ligament rupture after neurectomy. [12]

Complications

Complications from DBPLN neurectomy in horses are rare. [12] The most common complications are: [12][14]

  • Swelling at the surgical site
  • White hair regrowth at the surgical site

Although these complications can be permanent, they are cosmetic and do not affect the horse’s soundness or future athletic capacity. [14]

More severe complications reported in the literature include: [12][15][16]

  • Rupture of the suspensory ligament
  • Chronic or recurring injuries to the suspensory ligament
  • Neuroma formation

Like PD neurectomies, neuromas from DBPLN neurectomies typically require a second surgery to remove the growth and resolve pain. [15]

Horses that rupture their suspensory ligament are usually euthanized due to a grave prognosis. [12] Most reported cases of suspensory ligament rupture occur within 4 months of surgery. [12] Some horses with chronic injuries can remain sound for non-athletic careers, such as breeding. [16]

Neurectomized Horses in Competition

The ethics of performing neurectomy in horses has come into question due to the high risk of complications. [2] In particular, many experts question the use of neurectomized horses in competitions.

The main argument against neurectomized horses in competition is that the neurectomy procedure does not treat the underlying disease. Some individuals view this as a form of performance enhancement, as the surgery allows an otherwise unsound horse to participate in competition.

Additionally, the high risk of catastrophic injury in neurectomized horses may be even higher when the horse is required to perform athletically. Since athletic performance is not a requirement for the horse’s well-being, the additional stress of competition and the increased risk for catastrophic injury can compromise their welfare.

Currently, the Fédération Equestre Internationale (FEI) bans horses who have had a neurectomy procedure from competition. [17] Some horse racing organizations also ban neurectomized horses from competing, while others only require reporting of the surgery.

Summary

Neurectomy is the surgical cutting and removal of a nerve to prevent pain sensation in horses.

  • Neurectomy can be part of a treatment plan for chronic lameness conditions such as navicular syndrome or arthritis
  • Most horses make a full recovery after the procedure, and may return to athletic performance
  • Neurectomized horses have a high risk of lower limb injuries due to lack of pain sensation
  • Horse owners should work with their veterinarian to weigh the pros and cons of the procedure for their horse

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References

  1. Baxter, G. M., Ed. Adams and Stashak’s Lameness in Horses, Seventh edition. Hoboken, NJ: Wiley-Blackwell, 2020.
  2. Ross, M. W. and Dyson, S. J. Diagnosis and Management of Lameness in the Horse. St. Louis, United States: Elsevier, 2010.
  3. Dabareiner, R. M. et al. Comparison of Current Techniques for Palmar Digital Neurectomy in Horses. Proceedings of the Annual Convention of the AAEP. 1997.
  4. Whisenant, K. D. et al. Dorsal-to-Palmar Branch Neuroanastomosis in Horses Undergoing Palmar Digital Neurectomy Does Not Reduce Neuroma Formation or Improve Outcome. Veterinary Surgery. 2024. doi: 10.1111/vsu.14075. View Summary
  5. Oosterlinck, M. et al. Guillotine versus Pull-through Technique for Palmar Digital Neurectomy: A Retrospective Study on 40 Horses. Equine Veterinary Education. 2020. doi: 10.1111/eve.13017.
  6. Matthews, S. et al. Palmar Digital Neurectomy in 24 Horses Using the Guillotine Technique. Australian Veterinary Journal. 2003. doi: 10.1111/j.1751-0813.2003.tb11545.x.View Summary
  7. Maher, O. et al. Pull-Through Technique for Palmar Digital Neurectomy: Forty-One Horses (1998–2004). Veterinary Surgery. 2008. doi: 10.1111/j.1532-950X.2007.00352.x. View Summary
  8. Gutierrez-Nibeyro, S. D. et al. Outcome of Palmar/Plantar Digital Neurectomy in Horses with Foot Pain Evaluated with Magnetic Resonance Imaging: 50 Cases (2005–2011). Equine Veterinary Journal. 2015. doi: 10.1111/evj.12262. View Summary
  9. Easley, J. T. CHRONIC CAUDAL HEEL PAIN: TO “NERVE” OR NOT TO “NERVE”. Proceedings of the North American Veterinary Community Conference. 2015.
  10. Larsen, E. A. et al. Navicular Bone Fracture and Severe Deep Digital Flexor Tendinopathy after Palmar Digital Neurectomy in Two Horses. Open Vet J. 2023. doi: 10.5455/OVJ.2023.v13.i12.24. View Summary
  11. Guasco, P. G. et al. Excision of the Deep Branch of the Lateral Palmar Nerve of Horses to Resolve Lameness Caused by Proximal Suspensory Desmitis. Veterinary Surgery. 2013. doi: 10.1111/j.1532-950X.2012.01073.x. View Summary
  12. Watts, A. E. et al. How to Select and Manage Cases for Hindlimb Fasciotomy and Neurectomy. Proceedings of the Annual Convention of the AAEP. 2017.
  13. Kaneps, A. J. Surgical Options for Treating Tendon and Ligament Injuries. Clinical Techniques in Equine Practice. 2007. doi: 10.1053/j.ctep.2007.08.007.
  14. Dyson, S. and Murray, R. Management of Hindlimb Proximal Suspensory Desmopathy by Neurectomy of the Deep Branch of the Lateral Plantar Nerve and Plantar Fasciotomy: 155 Horses (2003–2008). Equine Veterinary Journal. 2012. doi: 10.1111/j.2042-3306.2011.00445.x. View Summary
  15. Norman, A. et al. Painful Neuroma Formation Following Plantar Fasciotomy and Neurectomy of the Deep Branch of the Lateral Plantar Nerve and Response to Surgical Resection in Four Horses. Equine Veterinary Journal. 2019. doi: 10.1111/evj.20_13152.
  16. Rutherford, D. Suspensory Body Break down Following Deep Plantar Neurectomy and Fasciotomy. Proceeding of the European College of Veterinary Surgeons Annual Scientific Meeting. 2012.
  17. 2024 Veterinary Regulations. Fédération Equestre Internationale, 2024.