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Thermocautery (firing) of horses and racing greyhounds

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Ratification Date: 20 Jul 2023

Policy

Thermocautery (firing) must never be used as a treatment in any animal as there is no scientific evidence for its efficacy and it causes unnecessary pain.  All regulatory authorities across Australia must ban this practice.

Definition  

Thermocautery, also called ‘firing’ or ‘therapeutic cautery’1, is the use of cautery to burn tissue on the leg of an animal as a remedial or preventative treatment for lameness from injury to any one or more musculoskeletal tissues (tendon, ligament, enthesis, joint capsule, periosteum, fascia, bone, cartilage, muscle). Firing can be performed in several ways using, for example, heated metal instruments1, an electrosurgical generator and electrode1 , a surgical laser2 or liquid nitrogen3,4.

The defining characteristic common to all methods of firing is deliberate damage to tissue, often normal healthy tissue1, as a treatment per se for lameness. Irrespective of alternative terminology, any procedure on the leg of an animal in which thermal damage is caused to tissue as a treatment per se for lameness is a form of firing.

Background

Thermocautery has a long and controversial history as a treatment for lameness in horses5 and has also been used to treat racing greyhounds6. Thermocautery causes the death of cells in treated tissue7,8,9,10 and damage to the structurally important collagen fibres11,12,13, eliciting a tissue repair response resulting in scar tissue formation4,14, similar to healing of other wounds15,16,17. Thermocautery is painful4,7,14,18 and is normally performed under anaesthesia1. The procedure can cause post-surgical pain4 or discomfort11, with ongoing sore skin and soft tissue swelling19.

Rationale

The intended purpose of firing is to damage tissue in the belief that this will provoke or enable healing in an injured tissue, either by directly firing the injured tissue (for example, by pin firing or point firing an injured tendon or joint) or indirectly by firing normal tissue adjacent to the injured tissue (for example, by bar firing or line firing the skin over an injured tendon or joint)1,14. Treatments for lameness that raise tissue temperature to 600C or above to denature collagen fibrils and shrink the tissue also kill cells in the treated tissue13 and therefore have the same tissue impact as firing, provoking the same wound healing response with removal of the damaged tissue debris and replacement with scar tissue8,13.

In the past, two theories about possible biological mechanisms of action have been proposed to justify the use of firing.

  • The first theory, known as ‘counter-irritation’4, postulates that the tissue damage from firing provokes an acute inflammatory response that increases blood flow and thereby promotes healing in adjacent tissue, with the chronic inflammation that was thought to underlie the refractory injury believed to be resolved in healing of the acute inflammation elicited by the tissue damage from firing1,14.
  • The second theory proposes that the scar tissue formed in healing the tissue damage caused by firing provides “tightening up” of the injured tissue and additional physical support, like an internal “scar tissue bandage”5,14.

These theories are not mutually exclusive. There is no scientific evidence supporting either theory.

The first theory, ‘counter-irritation’, is inconsistent with contemporary scientific knowledge of the relationship between the inflammatory process and tissue repair in response to traumatic injury of these tissues15,20. Rather than being the cause of failure of the tissue to heal, as proposed in the ‘counter-irritation’ theory, chronic inflammation indicates that repair of the injured tissue is incomplete and ongoing. Healing in dense connective tissues such as tendon is very slow20. Persistent inflammation may also indicate that injury to the healing tissue is ongoing because the original cause of injury is ongoing.

Research has failed to demonstrate the postulated increase in blood flow in response to firing21, 22, even though an increase in blood flow is reported during the acute phase of normal healing immediately after tendon injury - without firing23.

With better understanding of the nature of traumatic injury in these tissues, including the cumulative microdamage in overstrained tendons, ligaments and bones of racing animals15, it is clear that traumatic microdamage to the structurally important collagen fibres of these tissues accumulates if the rate of ongoing tissue damage exceeds the animal’s innate capacity for tissue repair. With this degenerative microdamage accumulating, the risk of tissue failure under peak force loading during training or competitive racing is increased15. Asymmetric adaptive remodelling of the bones of young greyhounds training and racing in one direction on circular tracks24 is a further factor predisposing to common injuries during competitive racing25. Adaptive remodelling also occurs in tendons and ligaments26,27,28.

Healing in injured tendons and ligaments invariably involves removal of the debris from damaged parts of the tissue and replacement of the damaged tissue with scar tissue15,20, but this scar tissue never achieves the full tensile strength and elastic properties of the tissue it replaces29,30. Tendons and ligaments therefore often fail at sites of scarring from previous injury31.

The second theory used to justify firing, the ‘scar tissue bandage’, is also flawed18, because the scar tissue that replaces the tissue damaged by firing will always have lower biomechanical strength than the tissue is replaces30.

These dense connective tissues do adapt over time in response to the force loading stresses placed upon the tissue20, with tissue remodelling during normal tissue turnover, and hence the stiffness and strength of these tissues and their resistance to failure under load can be increased with a rigorous training regime. Although this increase in tensile strength with remodelling also occurs slowly in scar tissue under normal training stresses, the scar tissue starts from a lower base of biomechanical strength and will continue as a point of weakness in the surrounding normal tissue30.

With knowledge of the overuse micropathology29 predisposing to fatigue injuries in racing animals, and the slow healing of this overstretched, strained tissue in tendons and ligaments, in which the immature scar tissue that is initially formed is remodelled over months or years to improve biomechanical function but never regains its normal elasticity, it can be readily inferred that firing of animals with refractory injuries to facilitate their early return to racing is not a rational therapy18. Alternative treatments including prolonged rest (spelling) and modification of the race training regime32 to reduce the rate of tissue microdamage during rigorous exercise are rational treatments.

It is therefore not surprising that designed experiments have failed to produce evidence of any direct clinical benefit from firing11. The only apparent benefit is the long period of enforced post-surgical rest from training and racing, with at least a year of rest recommended after firing4.

Firing provides no healing benefit additional to this long period of rest from training and racing11.

After a decade of scientific investigation of firing, Silver and Rossdale11 concluded that ‘line firing’ is not an effective treatment for acute or chronic injury and ‘pin firing’ is actually detrimental. Hayward and Adams33 concluded that “biological explanations for firing as a therapy are archaic and unsatisfactory in 2001, particularly when the evidence is against its effectiveness and provides no empirical justification”. Two decades later, there is additional scientific evidence supporting their view and nothing to the contrary.

Accordingly, thermocautery (firing) is now widely regarded as an obsolete treatment34 and “one of the most misused therapeutic agents in veterinary therapy”1.

One possible explanation for anecdotal reports of benefits from firing as a treatment for lameness is the desensitisation of injured tissue as a result of thermal destruction of local peripheral nerves during thermocautery8. Direct electrical damage to nerves may also occur, well beyond the area of thermal damage in electrosurgical cautery35. Desensitization of injured tissue can reduce lameness by reducing the sensation of pain from the injured tissue, without any beneficial impact on tissue healing. Treatment of lameness by desensitisation of injured tissue can thus facilitate aggravation of the injury if exercise is continued, increasing the risk of catastrophic tissue failure.[*]

The idea that tissue repair in response to deliberate additional tissue damage could improve the capacity of an injured tissue to withstand the peak force loading during competitive racing which the tissue, in its undamaged native state, was previously unable to withstand, is fundamentally ill-conceived18.

Relevant rules and regulations

Without scientific evidence of any benefit from firing sufficient to justify the adverse impact of this surgical procedure on treated animals, firing is inconsistent with contemporary animal welfare standards and community values. Some racing industry participants nonetheless still believe that firing can make an injured animal with refractory lameness sound again to run one or a few more races before retirement. Firing therefore continues in some places as a treatment for lameness, despite the lack of supporting scientific evidence.

Many Australian racing authorities now have policies opposed to firing and some have declared in their Rules of Racing that fired animals are ineligible to race. Racing authorities oveseas have also prohibited firing.

Under the Australian Rules of Racing, adopted in all Australian States and Territories, any thoroughbred horse that has been fired is ineligible to race. Under the Australian Harness Racing Rules, it is an offence to “perform or authorise the performance of the procedure of pin-firing or bar-firing (thermacautery) a horse”.

Equestrian Australia subscribes to the FEI Code of Conduct for the Welfare of the Horse which states that “Any surgical procedures that threaten a competing Horse’s welfare or the safety of other Horses and/or Athletes must not be allowed” but does not specifically mention firing.

Under the Local Rules of Racing for Greyhounds in NSW, any dog that has been fired is ineligible to race. However, firing is not mentioned in the Greyhounds Australasia Rules that are adopted in all states, nor in the local rules of states other than NSW. Accordingly, any Greyhound that has been fired remains eligible to race in all states other than NSW.

Under the Prevention of Cruelty to Animals Act 1979, NSW has declared firing to be a criminal offence in all species since 1997. Firing is also a prohibited procedure in Victoria under the Prevention of Cruelty to Animals Act 1986, but only in horses. ‘Horse firing’ is an offence in the Northern Territory, under the Animal Protection Act 2018.  In December 2022, Queensland prohibited “firing or blistering on horses or dogs” under the Animal Care and Protection Act 2001. Elsewhere in Australia, firing is not specifically declared in law to be a prohibited procedure.   

Recommendations

  1. Traditional forms of thermocautery (firing) such as ‘pin firing’, ‘line firing’ and ‘freeze firing’ must not be used in any circumstances in any animal, by veterinarians or other persons.
  2. All jurisdictions in Australia should prohibit the use of thermocautery (firing) in their prevention of cruelty to animals or animal welfare legislation, defining thermocautery (firing) as any procedure in which deliberate thermal damage to tissue is caused as a treatment per se for lameness.

Purpose

This policy provides a clear statement of the AVA’s views on firing, and can be used to promote greater consistency and clarity in the rules of racing and in animal welfare legislation across all Australian jurisdictions.

References

  1. Adams OR (1974) Lameness in Horses, 3rd Ed Lea & Febiger Philadelphia pp 441-445.
  2. Davis PE (1983) Examination for racing soundness. In: Proceedings No 64, Refresher course on greyhounds, Post-Graduate Foundation in Veterinary Science, University of Sydney, pp 601-611 cited in Guilliard (2012)
  3. McKibbin LS, Paraschak DM (1985) An investigation on the use of cryosurgery for treatment of bone spavin, splint, and fractured splint bone injuries in standardbred horses. Cryobiology 22(5):468-76
  4. Ellis DR and Dey SP (2011) Counterirritation in Diagnosis and Management of Lameness in the Horse (2nd Ed), Ross W and Dyson SJ (Eds) Ch 88 pp 867-869 WB Saunders
  5. McCullagh KG and Silver IA (1981) The actual cautery: Myth and reality in the art of firing. Equine vet J 13(2):81-84
  6. Guilliard MJ (2012) The nature, incidence and response to treatment of injuries to the distal limbs in the racing Greyhound Diploma Thesis for Fellowship of the Royal College of Veterinary Surgeons available online at https://knowledge.rcvs.org.uk/document-library/fellowships-guilliard-t-736/
  7. Larsen L (1960) The Reaction of Mesodermal Tissues to Irritation PhD Thesis, University of Sydney cited by Hayward M and Adams D (2001)
  8. Arnoczky SP and Aksan A (2000) Thermal modification of connective tissues: basic science considerations and clinical implications J Am Acad Orthop Surg 8(5):305-13
  9. Ruidiaz ME, Cortes-Mateos MJ, Sandoval S, Martin DT, Wang-Rodriguez J, Hasteh F, Wallace A, Vose JG, Kummel AC, Blair SL. (2011) Quantitative comparison of surgical margin histology following excision with traditional electrosurgery and a low-thermal-injury dissection device. J Surg Oncol 104(7):746-54
  10. Akyüz O and Tatar Z (2021) Is it safe to use a thermocautery device for circumcision? Examination of the histopathological changes emerging after thermocautery-assisted circumcisions. Andrologia 53(3):e13968. doi: 10.1111/and.13968
  11. Silver IA and Rossdale PD (Eds.) (1983) A clinical and experimental study of tendon injury, healing and treatment in the horse. Eq. Vet. Journal 1983 Suppl. 1, pp 1-43
  12. Lopez MJ, Hayashi K, Fanton GS, Thabit G and Markel MD (1998) The effect of radiofrequency energy on the ultrastructure of joint capsular collagen Arthroscopy 14(5):495-501
  13. Hayashi K and Markel MD (2001) Thermal Capsulorrhaphy Treatment of Shoulder Instability: Basic Science Clin Orthop Relat Res 390:59-72
  14. Jepson P (2012) Firing and thermocautery in Proceedings of the 51st British Equine Veterinary Association Congress, Birmingham, UK p 86
  15. Birch HL, Sinclair C, Goodship AE and Smith RKW (2014) Tendon and ligament physiology in Equine Sports Medicine and Surgery (2nd Ed) Eds Hinchcliff KW, Kaneps AJ and Geor RJ Ch 9 pp 167-188 WB Saunders
  16. Rodrigues M, Kosaric N, Bonham CA and Gurtner GC (2019) Wound Healing: A Cellular Perspective. Physiol Rev 99(1):665-706
  17. Guo HF, Mohd AR, Abd Hamid R, Chang SK, Zainal Z and Khaza'ai H. (2020) A new histological score grade for deep partial-thickness burn wound healing process Int J Burns Trauma 10(5):218-224
  18. Bramlage LR (1991) Therapeutic cautery for tendonitis: the test of time Equine vet. Educ. 3(4):180
  19. Ross MW and Genovese RL (2011) Curb in Diagnosis and Management of Lameness in the Horse (2nd Edition) Eds Ross MW and Dyson SJ Ch 78 pp792-798 WB Saunders
  20. Kirkby Shaw K, Alvarez L, Foster SA, Tomlinson JE, Shaw AJ and Pozzi A (2020) Fundamental principles of rehabilitation and musculoskeletal tissue healing. Vet Surg 49(1):22-32
  21. McCullagh KG, Goodship AE and Silver IA (1979) Tendon injuries and their treatment in the horse. Vet Rec 105 (3):54-57
  22. Gabel AA (1983) Management of Tendon Injuries in Racehorses in Equine Lameness, Proceedings of the Fifth Bain Fallon Memorial Lectures, Australian Equine Veterinary Association, p 142 cited by Hayward and Adams (2001)
  23. Smith R. (2008) Tendon and Ligament Injury in Proceedings of AAEP Annual Convention, San Diego
  24. Johnson KA, Skinner GA and Muir P (2001) Site-specific adaptive remodeling of Greyhound metacarpal cortical bone subjected to asymmetrical cyclic loading. Am J Vet Res 62(5):787-93
  25. Bergh MS, Piras A, Samii VF, Weisbrode SE and Johnson KA (2012) Fractures in regions of adaptive modeling and remodeling of central tarsal bones in racing Greyhounds Am J Vet Res 73(3):375-80
  26. Laros GS, Tipton CM and Cooper RR (1971) Influence of physical activity on ligament insertions in the knees of dogs. J Bone and Joint Surg 53-A:275-286
  27. Woo SL, Ritter MA, Amiel D, Sanders TM, Gomez MA, Kuei SC, Garfin SR and Akeson WH (1980). The biomechanical and biochemical properties of swine tendons--long term effects of exercise on the digital extensors. Connect Tissue Res 7(3):177-83
  28. Bukowiecki CF, Bramlage LR and Gabel AA (1987) In vitro strength of the suspensory apparatus in training and resting horses. Vet Surg 16:126-130
  29. Sharma P and Maffulli N (2006) Biology of tendon injury: healing, modeling and remodeling. J Musculoskelet Neuronal Interact 6(2):181-90
  30. Nichols AEC, Best KT and Loiselle AE (2019) The cellular basis of fibrotic tendon healing: challenges and opportunities. Transl Res. 209:156-168
  31. Crevier-Denoix N, Collobert C, Pourcelot P, Denoix JM, Sanaa M, Geiger D, Bernard N, Ribot X, Bortolussi C and Bousseau B (1997) Mechanical properties of pathological equine superficial digital flexor tendons Equine Vet J Suppl. 23-6
  32. O'Sullivan CB and Lumsden JM (2014) Veterinary aspects of training Thoroughbred racehorses in Equine Sports Medicine and Surgery (2nd Ed) Eds Hinchcliff KW, Kaneps AJ and Geor RJ Ch 48 pp 1013-1036 WB Saunders
  33. Hayward M and Adams D (2001) The Firing of Horses: A Review for the Animal Welfare Advisory Committee of the Australian Veterinary Association available online at https://www.researchgate.net/publication/356283621_THE_FIRING_OF_HORSES_A_Review_for_the_Animal_Welfare_Advisory_Committee_of_the_Australian_Veterinary_Association_c
  34. Rijnberk A (1997) Modes of Treatment Aust Vet J 75(4):260–261
  35. Caglar O, Arslan R, Firinci B, Aydin ME, Karadeniz E, Nalci KA, Salman AB and Aydin MD (2021) Comparing the effects of current circumcision techniques on dorsal root ganglia: an experimental study Ann Pediatr Surg 17(15) https://doi.org/10.1186/s43159-021-00077-9

[*] Under the Australian Rules of Racing, a horse that has had a limb neurectomy or any artificial form of permanent limb desensitisation is ineligible for any race.  Under the Australian Harness Racing Rules, a horse that has had a limb neurectomy is ineligible to race.

Date of ratification by AVA Board 25 July 2013

Updated and re-ratified 20 July 2023