neurectomia, lameness, pain, hoof deformation, hoof physiology

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1 Nerve cut and the consequences - case example Dr.med.vet. Hiltrud Strasser, Tuebingen, Germany Key words: neurectomia, lameness, pain, hoof deformation, hoof physiology Summary In this lecture a case of chronic lameness will be discussed. It started with a genetic hoof deformation and finally ended with a necrotic hoof and blood poisoning. The basic cause of the problem was not identified, therefore not removed. Instead the foot nerves were cut and the chronic lack of blood supply as well as the dying off of most of the tissue inside the hoof was not noticed. After the returning of the blood supply to the hoof, it was not possible to keep the poisoning under control. This case An 18 year old horse was brought to the Hufklinik because of chronic lameness. (Fig.1) The horse had been in the care of the present owner for 15 years and was used as the family riding horse. The heavy warm blood mare had been shod from 3 years to 15 years of age. The right front was a club foot, which was never especially treated to change the deformation. 5 years ago the shoes were removed because of lameness and different types of orthopaedic shoeing and veterinarian treatment was used. The lameness couldn t be cured and the decision was taken to do nerve cut surgery. After the surgery the horse could be ridden by the family for 5 more years. Then the lameness returned which was diagnosed as laminitis. Different conventional treatments were applied, without success. This is when the horse came to the Hufklinik. We couldn t save the life of the horse because of the poisoning of the whole metabolism. Fig 1: Horse when arrived, right front hoof very lame Method Because there was a clubbed front right foot, the coffin bone had been standing on its tip for many years. The overloading of the suspension in the front part of the hoof had the consequence of enlarging the lamellae. This leads to more movement of the coffin bone inside the hoof capsule, with the result of unphysiological pressure to the tip of the bone, leading to bone destruction. The enlarged or stretched lamellae allows for the coffin bone to sink down further within the hoof capsule. At this stage often laminitis and lameness caused by pain also occurs. The circumflex artery was compressed in the front part of the foot therefore this part of the solar corium was no longer supplied with blood. Also the compression of the circumflex artery has the effect of backing up the blood in the arteries inside the coffin bone in this region. Therefore: without blood circulation the bone dies. This circulus vitiosus was broken for a while by the nerve cut surgery and the horse no longer has feeling - no more pain. The result is that the horse doesn t protect the hoof anymore. This leads to the 7

2 quiet circulus vitiosus. Nobody notices that the destruction of the coffin bone continues and that the dead tissue cannot be removed by the blood stream because of the lack of circulation due to the incorrect hoof shape and the incorrect lever forces, which continue to compress the blood vessels more and more. The little parts of poisonous dead tissue structures can be managed by the organisms, as it is a very small amount because of the restricted blood circulation in the deformed hoof capsule. The poisonous dead tissue structures within the hoof that find their way into the blood system are kept at a minimum due to the restricted blood circulation in the deformed hoof capsule and therefore are easily managed and expelled by the organisms. There are no outside signs to show anybody the damage that is happening inside the horse. Exception: x-ray shoes the arthrotic changeings. Because the clubfoot was not remedied by proper treatment in the beginning, the steep position of the coffin bone was always there, the overload in the lamellae suspension always present, the circumflex artery always pinched off, dead solar corium in the front area, parts of the frog corium and insertion area of the deep flexor tendon dead from no longer being supplied by blood. When the continuing damage (dying of tissue) spread to the bar/bulb area which does not take its blood supply from the circumflex artery, the horse started getting lame again. At this stage the horse was brought to the Hufklinik. In the deformed hoof, it is not possible to know what damage has been done inside due to incorrect lever forces (Fig 2-5). 2 clefts in the hoof capsule 3 holes in the bulb area 4 very long bars and heels full sole 5 additional bone around the joint short-long pastern Fig. 2-5 : right front hoof when arrived in Hufklinik The first thing we tried was to bring the hoof into a more natural form by removing the wrong lever forces and improving the blood supply (Fig. 6-7). 8

3 Fig. 6 and 7 : side and front view Fig. 8 sole view after first correction With this we had to open up huge areas of stinking masses which had been sitting there for years, because heel growth had never been removed. The normal lever forces of the wall caused the blood supply to come back and it started bleeding into the dead tissue areas (Fig. 8). The horse seems to be much better after opening the abscessing areas. It moved more and did eat very well, was interested in the environment. But the blood took the dead tissue parts into the body. Having these destructed molecules in such huge amounts overloaded the metabolic organs. This led to a very quick poisoning of the organism, even though we supported the liver and kidneys with remedies and optimum food. The hoof started to regenerate after the return of the blood supply but the blood poisoning was faster. We couldn t win this competition! The horse became weaker every day and we had to euthanize it when it stopped eating. After the horses euthanasia the hoof was removed and dissected. The regeneration processes and the rotting processes are visible in the cross section (fig. 9). Rotten areas Regenerating areas Abb.9: dissected hoof 9

4 Discussion There are different methods for cutting the nerve.. Present common practice is to remove a piece of the nerve and stitch the perineurium, as shown in Adams lameness in horses (Fig.10). Scinne cut perineurium Abb. 10: aus Adams`Lahmheit der Pferde: Technik des Nervenschnittes Because of the club foot, the coffin bone was standing for many years in an abnormal position tipped forwards with it's base not parallel to the ground. Resulting non physiological pressure to the tip of the coffin bone (Wolff`s law!) led to destruction of the bone tissue (Fig. 11). Fig. 11: destroyed tip of the coffin bone Because of the club foot, the coffin bone was standing for many years in an abnormal position tipped forwards with it's base not parallel to the ground. Resulting non physiological pressure to the tip of the coffin bone (Wolff`s law!) led to destruction of the bone tissue. A horse with a club foot, without a nerve cut, would be very lame and would avoid hard impact to the foot. This horse with a nerve cut was pain free and not lame, but because of this the deterioration in the foot progressed unnoticed. From the non physiological pressure of the coffin bone on the horn sole and also the pressure from the elongated bar onto the living corium, the corium of the sole died in large areas unnoticed! Sometimes, following trimming, there was some revascularisation which caused abscesses. The development of abscesses would normally be very painful, but following a nerve cut they are never painful. The puss destroyed the dead corium of the sole and some of the dead bone structure, as well as parts of the hoof horn. It requires years for damage such as this to develop. In a foot having only short term abscess problems from pinching effects for example one shoeing period the solar corium can regenerate quiet fast. Not so after many years of abnormality with an huge amount of dead tissue. 10

5 Abb.12: (Thorsten Kaiser, NZ) : The damage inside the Hoof is similar to the above explained case, but this horse s hoof shape was not changed for better blood circulation before it was killed. In this hoof we can not detect any regeneration processes. Half of the coffin bone is rotten, the hoof corium died and is destroyed by puss. The mineral structure of the tip of the coffin bone is less destroyed than in our case. Conclusion We need to understand why nerve cut surgery is such a dangerous treatment! 11