implication, the pathology of *‘pin firing’ suggests that it must have similar, if not more detrimental, effects.
The biochemical findings showed that *line ‘firing’ produces major short term changes in skin collagen synthesis and destruction but this rapidly returns to normal.
In one case only, ‘firing’ caused an increase in protein synthesis (but not collagen synthesis) in the underlying tendon, but this had returned to normal in three to four weeks.
In all cases, tendon collagen synthesis was unaltered or decreased slightly in ‘fired’ animals.
In some animals, organisation of fibrinous inflammatory exudates caused peritendinous adhesions after firing.
Pathological studies showed that tendon healing is a very prolonged process and continues after 15 months. ‘Firing’ did not alter this process except in the case of ‘pin firing’ where injury to the actual tendon prolonged the healing and resulted in further damage.
Scar collagen in *‘pin fired’ tendons did not align along lines of stress and remained as ‘cores’ of permanent weakness. ‘Fired’ skin, after an initial period of acute inflammation and oedema, produced local areas which were weaker than normal skin.
On the basis of these observations we have to conclude that ‘line firing’ is not an effective treatment for acute or chronic injury and that ‘pin firing’ and tendon splitting are detrimental. The work of L.H.
Larsen Leonard Larsen was Professor of Veterinary Surgery at the University of Sydney from (date period) who studied the consequences of firing for a PhD Thesis titled “The Reaction of Mesodermal Tissues to Irritation” and dated 1960.
Professor Larsen observed that cautery of the musculoskeletal system had been discontinued in human medicine47.
He found many field observations on firing of horses in the published literature, but little critical evidence as to the nature of changes in the tendon after cauterisation, or on the impact on tendon strength.
Larsen quotes Irving R.C48, who cites an experiment performed by Hunting.
Twelve horses with bilateral forelimb sprains were studied.
In each case the less affected limb was cauterised.
The horses returned to work in 4 months but all broke down on the cauterised limb.
Larsen used micro-radiography and stereoscopic micrography to examine limbs after various treatments including thermo-cautery.
Up to 40 thermo-cautery canals 3/8 inch (~10mm) apart were created over the flexor aspect of the limb under procaine local anaesthesia.
The depth of insertion was “visually assessed”, but the intention was to penetrate skin and subcutis and synovial sheath only, not the tendon.
A “dressing” of 50% tincture of iodine, 25% phenol and 25% glycerine was applied daily, and the limb bandaged.
He believed that the phenol provided local analgesia.
Larsen found no behavioural evidence of post-operative pain or irritation.
Pulse rates and body temperatures were slightly elevated for various periods after thermo-cautery.
Marked local inflammation with heat, and swelling was noted within one hour and reached a maximum at three days.
Pain on could be elicited by palpation.
It was significant on firm pressure to three days and had diminished by 6-10 days.
Wound discharges diminished after 4 days.
Some horses had marked sloughing and eschar formation.
The skin still felt hot for up to 18 days when experimental horses were slaughtered.
Histopathology showed a coagulated zone a few cells thick, and a zone of cell damage approximately half the thickness of the skin, around each cautery point.
There was active hyperaemia, and by three days blood vessels were engorged with erythrocytes, distended and tended to rupture.
Most swelling in the limb occurred in the subcutis and synovium and was caused by hyperaemia, congestion and oedema, and later by deposition of connective tissue.
The tendons were unaffected.
Cauterisation was found not to increase the vascularity of tendons (indeed, vascularity was reduced for the first few days), but it did stimulate marked blood vessel proliferation in the subcutis and synovium in the area of cauterisation.
The anterior aspect of the limb was unaffected.
Larsen pointed out that the normal inflammatory process associated with repair following tendon injury is characterised by intense hyperaemia and increase in blood vessel concentration in the affected n and surrounding synovial membranes.
In normal repair “fibroplasias and blood vessel formation are in excess of that necessary for repair,” [therefore] “considerable doubt is cast on the value of cauterisation in tendon healing.” Tissue reacts to repeated strain by hyperaemia, oedema and reduction in tensile strength.
As a consequence, the prolonged hyperaemia induced by cauterisation further predisposes to tendon sprain.
Accordingly, Larsen considers that “cauterisation is of doubtful value in promoting tendon repair”, but may lead to restrictive adhesions between the tendons and their synovial sheaths.
He left open the possibility that cauterisation might have value in converting chronic to acute inflammation and could lead to satisfactory resolution of lesions involving bursae and joints where movement was unimportant.
Bursae and joints were not the subject of his thesis.
Policies and Legislation on Firing Australia Examination of the Animal Welfare, Animal Protection and Prevention of Cruelty to Animals Acts and associated Regulations from all Australian States and Territories has only revealed one jurisdiction in which firing is mentioned.
The following is a quote from the NSW Prevention of Cruelty to Animals Act (1979) “PREVENTION OF CRUELTY TO ANIMALS ACT 1979 – SECT 21A 21A Firing prohibited A person who applies a thermal stimulus (such as hot wires) to the leg of an animal with the intention of causing tissue damage and the development of scar tissue around tendons and ligaments of the leg is guilty of an offence.
Maximum penalty: 250 penalty units in the case of a corporation and 50 penalty units or imprisonment for 6 months, or both, in the case of an individual.” In the ACT, the Code of Practice for the Welfare of Horses, gazetted under the Animal Welfare Act 1992 (8 Dec 1993) states (p9) “4.4.3 Surgical and Medical Procedures Practices such as firing, knicking (cutting the skin or ligaments of the tail to ensure the tail is held high) and limb neurectomy for the purpose of performance enhancement are not acceptable.” It is not clear whether the Code refers to all firing as being not acceptable, or whether only firing for performance enhancement is not acceptable, and that firing for other reasons may be.
In the ACT, Codes of Practice do not have legislative stature, but may be used as a defence against prosecution under the Act.
No other State or Territory in Australia mentions firing or thermocautery in its Animal Welfare or Prevention of Cruelty to Animals Act, or equivalent legislation, nor in a Code of Practice.
Victoria has indicated it is moving to institute a ban through its Prevention of Cruelty to Animals Act (Lee-Anne Wahren pers.comm.).
The position of Australia’s Harness Racing Association is as follows: “Pin firing or similar treatment on a pacer or trotter prohibits that horse from participating in a race (Australian Rules of Harness Racing).
The National Rules cannot permit a procedure which is prohibited by another Act in a State.” Overseas New Zealand The Animal Welfare Act (1999) states: Surgical Procedure Offences 21 (2) A person commits an offence who — (a) Crops, or causes to be cropped, the ears of a dog; or (b) Performs, or causes to be performed, blistering or firing or nicking on a horse. Royal College of Veterinary Surgeons (UK) Given the extensive debate in the UK veterinary literature, and the fact that significant research into the effectiveness of the procedure was performed there, it is not surprising that the registering body for veterinary surgeons in the UK would rule on this matter.
In 1983 the Equine Sub-Committee discussed firing, in the light of Silver’s work.
They considered whether the procedure was an effective form of therapy for tendon strains and whether the pain involved was justified by the results.
They agreed that the procedure was painful, but decided that the procedure, while not ideal, was the best treatment available for tendon sprain. 49 The British Government declined to abolish the firing of horses in 1986.
In 1991, J.B.
Johnson proposed that “the Council [of the RCVS] should now declare firing to be an unethical procedure and prima facie evidence of conduct disgraceful in a professional respect”.
This motion was unanimously agreed, and the effective date was set at 1st September 199150.
This ruling provoked, as might have been expected, significant debate, including raising concerns that firing would continue by European vets (in the UK or in Europe), or by lay people, with significant detriment to horse welfare.51,52.
Further, the ability of the Royal College to pursue a case against a veterinarian who, after due consideration, performed the procedure with diligence, effective anaesthesia and analgesia and postoperative care, and a successful result perhaps saving a horse from euthanasia, was challenged.53.
In 1992 it was reported that the Royal College had agreed not to pursue a notified occurrence of firing, casting doubt on their ruling.54 The Royal College now lists “firing of horses” in its “16.
Category C “Unacceptable Procedures” Annexe – c.) Practices which Council deplores as being ineffective and/or lacking justification as methods of treatment and which should be discontinued.” 55 (see box 3)
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