Equine Keratomas

By Matthew Jones FdSc AWCF

BSc Honours Degree in Farriery

Anton Lungwitz’s Image from 1884

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1.0 Introduction

Keratomas have been observed in horses’ feet for many years and yet they still remain an enigmatic lesion with little understanding as to their aetiology and pathogenesis.

It is generally accepted that keratomas are a rare cause of lameness and this has led to a general apathy in their study and a lack of concerted documentation of their incidence. Observing feet every day in my career as a farrier, I occasionally see areas of opaque, erroneous horn, coupled with an inward deviation of the white line, in sound horses. For example, Holly pictured in Figure 1 below, has displayed an area of erroneous horn in the toe of her off hind for the last three years without any sign of lameness.

Figure 1. Holly. Lesion in a sound foot. Figure 2. Dillon. Confirmed keratoma.

Conversely, Dillon’s foot in figure 2 displayed a similar lesion, again in a sound foot. However a radiograph was ordered by a concerned owner and the pedal bone was found to possess an area of osteolysis, in relation to the lesion. The lesion was extirpated successfully before any instances of lameness and with the minimum of trauma to the hoof ( Wiseman. May 2011 pers comm).

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1.1 Reasons for Performing the Study

By its nature, the veterinary profession only encounters a keratoma when it causes lameness. These instances of lameness maybe after the sinister growth has developed in size large enough to place pressure on the sensitive structures within the hoof or when the keratoma has provided a path for repeated abscessation in the hoof, in quick succession.

Keratomas have also been known to cause a distorted hoof capsule, a crack in the wall and osteolysis of the pedal bone with subsequent weakening of the pedal bone.

It has been said that keratomas are an insidious cause of lameness, (Redding 2007). They are usually only diagnosed after much loss of work due to intermittent bouts of lameness or repeated occurrences of abscesses in the hoof over many months. Surgery to remove them is invasive and a full recovery from surgery can take up to a year for the hoof wall to grow back. Also the keratoma can return if surgery is not successful in extirpating the mass completely.Other postoperative complications such as hoof wall instability and excessive granulation tissue formation have been reported, Honnas (1997). The worst case that I personally have encountered is that of the horse that foundered on the opposite foot due to excessive weight bearing, post-surgery, resulting in it’s euthanasia.

Is it possible therefore that a farrier could aid the veterinary profession in the diagnosis of these lesions before they become large enough for their symptoms to arise and lessen their impact on the hoof?If an erroneous area of horn becomes apparent in the hoof during routine trimming, can it be flagged up as a keratoma before the onset of lameness? If farriers were able to recognise the presence of a keratoma in the foot before the onset of lameness, precious time in work may not be lost, the lesions would not develop to a size large enough to cause lameness and therefore the surgery to remove them would be less invasive.

Therefore it seemed prudent to investigate whether these lesions, that farriers notice in feet, could provide another path in the study of keratomas and therefore an aid in their diagnosis before much loss of work ensues.

In an attempt to gather more information the author decided to conduct an in depth literature review and pursue an information gathering exercise.

The aims of this study were therefore to-

a. Conduct a literature review to cover the definition, aetiology and pathogenesis of keratomas.

b. To gather information from the working farriery world about erroneous areas of horn resembling keratomas.

c. To attempt to gather some new cases of keratoma incidence and type and report their histological findings.

d. To draw some conclusions about keratomas, highlight areas of controversy and give indications for future directions of study.

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2.0 An Overview of the Current Thinking on Keratomas

2.1 Definition

Keratomas have been defined in the literature as: A space occupying, erroneous mass of keratin and squamous epithelial cells (Hamir et al.1992); An aberrant focal proliferation of cornified tissue produced by abnormal corium (Honnas et al 2003); A tumour of keratin producing cells (Greet 2002); A new piece of horn tissue, Van Nassau (2007).

2.2 Area of Occurrence

Keratomas have been detailed throughout the literature occurring in any area of the hoof. They are most commonly cited as being found behind the hoof wall, between the stratum medium and the underlying distal phalanx (Greet2002). However they have also been noted within the sole (Boys Smith 2011), the frog (McDiarmid (2007) and even in one case of note at the coronary band,( Hamir et al. 1992).

2.3 Diagnosis

Keratomas can be difficult to diagnose because of their rarity and an inconsistent repetition of symptoms between cases. For example they can, but will not always reveal their presence with-

1. A deformation in the hoof wall.2. An inward deviation of the white line3. A crack in the hoof wall.4. Recurring abscessation. 5. Classically, if the lesion occurs behind the dorsal hoof wall, they may cause an area of

osteolysis of the pedal bone in relation to their size.

2.4 Histopathology

Today, confirmation that the mass is a keratoma must always be carried out histopathologically, Boys Smith et al (2006). This requires a good partial or full biopsy technique. However it was not until Lloyd et al.(1988) that the histology of keratomas was considered in the literature. Up until this time keratomas were considered to be tumours of the keratin producing cells of the epidermal laminae at the coronary band, (Stashak 1987).

Lloyd et.al.(1988) stated that if the definition of a ‘tumour’ is taken to be a neoplasm, then it is not strictly a suitable term for a keratoma which actually is hyperplastic in nature. Since 1988 the term tumour is slowly going out of fashion in relation to keratomas in the literature.

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A neoplasia is an increase in cells with a loss of control by the body. A hyperplasia on the other hand is an increase in cells but with no loss of control by the body (pers.comm. Debra Fews April 2011)

2.5 Imaging of the Lesion

Keratomas themselves, being only made up of abundant keratin and squamous epithelial cells, (Honnas 1997), will not appear on radiographs. However if they develop behind the hoof wall their effects on the pedal bone may. Pressure necrosis of the dorsal surface of the pedal bone occurs following expansion of the mass in the confined space of the hoof capsule (Pickersgill 2000). The mass of the keratoma therefore may cause osteolysis, or a focal reabsorption of the bone, in relation to it’s size. If this is the case, radiography of the foot will display a smoothly outlined, semi-circular radiolucent defect within the solar margin of the pedal bone, (Boys Smith 2011).Unfortunately it is possible for the pedal bone to display no osteolysis on the radiograph when a keratoma is present (Honnas 1997). Stashak (2002) cites the study by Lloyd et al. (1988) when it was reported that out of the seven cases of keratoma studied, only three displayed an area of osteolysis in the pedal bone.Therefore the horse may be lame, the hoof may have a distorted white-line and hoof wall but it is not certain that a radiograph of the hoof will display an area of lysis in the pedal bone. Radiographs are therefore an unreliable path to diagnosis and to accurate positioning of the lesion.Magnetic Resonance Imaging is more sensitive in defining space occupying lesions which have not caused a defect in the pedal bone.

2.6 Differential Diagnosis

The reason that the diagnosis of a keratoma is only confirmed after the histopathology of the mass is considered is because there are other causes of keratoma like symptoms.

Medial and lateral hoof imbalances can cause cracks and deformations in the hoof wall. Infiltrations of white-line disease will cause separation of the wall and cavities behind the hoof wall. Abscesses, puncture wounds and abnormal laminar horn production due to laminitis must be considered (Chan and Munroe 1997). Canker is also characterised by a proliferation of squamous epithelial cells but it does not undergo extensive keratinisation (Hamir et al. 1992).Squamous cell carcinomas, malignant melanomas, haemangiomas and endochondromas also cause radiographical evidence of osteolysis of the pedal bone. However because these afflictions infiltrate the bone itself, they are associated with new bone formation and also the osteolysis they cause, is more irregular in outline than the smoothly outlined semi-circular defect caused by a keratoma (Pickersgill 2000).

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Septic and non-septic pedal osteitis can result in areas of lysis around the solar margin of the pedal bone and proximally in the hoof, near the distal interphalangeal joint, subchondral bone cysts can occur (Pickersgill 2000).

2.7 Treatment

A lesion that occurs behind the hoof wall can be extirpated by resecting the wall over the site of the osteolysis, revealing the keratoma ( Lungwitz 1884, Greet 2002). Care must be taken to stabilise the hoof capsule after the lesion has been removed with a suitable shoe and perhaps bridging across the defect with a plate. Packing the defect reduces the risk of excessive granulation tissue formation (Boys Smith et.al, 2006).

2.8 How Keratomas Cause Lameness

A keratoma can cause lameness in two ways-

1. Keratomas can be a space occupying mass (Redding 2007) within the hoof. This can cause lameness due to pressure placed on the sensitive laminae in a similar way that a farrier’s nail, driven too close to the sensitive dermis, (a nail bind) will be felt. The lameness is often intermittent in nature.

2. If the presence of the keratoma is manifested by a deviation of the white line then this can upset the integrity of the solar mural junction and allow for infection to enter the sensitive structures at the white line, causing an abscess, (Greet 2002).

This failure in the integrity of the hoof caused by the keratoma allows for the ingress of organisms which will cause infection (Greet 2002). Often a feature in the diagnosis of keratomas is that they are only considered after repeated instances of abscessation have occurred in the foot. This may take a period of months until a further underlying cause will be investigated. Ironically, an intermittent lameness for a period of months caused by the space occupying mass of the keratoma may be followed by a time of severe lameness, due to a keratoma-caused abscess. The ensuing cavity formed by the pus relieves the pressure the space occupying keratoma places in the hoof, for a short while. Therefore full soundness occurs while the cavity formed by the pus relieves the pressure the keratoma inflicts, only for it to return, once the cavity has grown out.

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2.9 Types of Keratoma

The commonest form that the keratoma takes is that of a cylinder but they can also take a spherical form and some authors think they also form a fan shape, ( Wortley (1906); Van Nassau (2007)).Greet (2002) states that there are two basic types of keratoma, that of the cylindrical and that of the spherical.

Cylindrical keratomas are to be found behind the hoof wall and may occupy a space down the length of the hoof wall to the bottom of the foot. It is here where they can distort the white line and show their presence within the foot. They can also distort the wall and cause cracks in the wall as they take up space in the hoof capsule.

The second type of keratoma takes a spherical form and can occur anywhere in the hoof wall (Boys Smith 2011). Greet (2002) notes that the two types can sometimes be seen together in the same foot and even together in the same defect.

2.10 The Relation Between Keratomas and Abscesses

Keratomas are well associated with abscesses in the hoof. It has been noted that abscesses can give rise to keratomas (Dollar and Wheatly 1898; Boys Smith (2011) and also an established keratoma can be the instigator of an abscess. (Greet 2002). Any horse can develop an abscess in the foot at some point in its life. This is most commonly due to our temperate climate and the resulting muddy conditions that, into which, we are forced to turn-out our horses into.Sodden and therefore soft feet are vulnerable to the ingress of infection, which will develop into either solar or wall abscesses. An abscess in the sole will result in a cavity being formed by the pus in the sole. If the pus is allowed to build up without being drained it will take the path of least resistance throughout the foot (Stashak 2002). This is invariably out through the bulbs of the heels.

Infection, which forces its way into a sodden white line, can result in ‘gravel’,(Stashak 2002). ‘Gravel’ is the term given to the build-up of pus behind the dorsal hoof wall. Again, if this abscess is left to develop, it will take the path of least resistance throughout the foot, which in this case, is up behind the hoof wall and out at the coronary band.These coronary band ‘blow-outs’ of pus will cause temporary disruption to the germinative layer of cells at the coronary band, upsetting the germination of the hoof wall at this instant. Subsequently, the familiar horizontal crack appears at the coronary band and will grow distally with the hoof wall. I have seen tracks of white line disease associated with a crack in the hoof wall, result in an abscess high up in the wall, with a subsequent ‘blow-out’ of pus at the coronary band. The ensuing horizontal crack in the hoof wall then travels distally with the wall, until it meets the original track of white line disease. The hoof wall above the horizontal track contains no

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ingress of the track of the white-line disease and so this ‘blow-out’ acts as a natural crack stopping mechanism of the hoof.Sadly keratomas that cause repeated coronary band ‘blow-outs’ due to repeated abscesses obviously do not grow out with the hoof wall otherwise they would not cause more than one abscess. They must remain in situ as the hoof wall grows over them.

In my own experience I see fewer abscesses during the summer months than the winter, in horses in my care. Anecdotally therefore a foot that is kept sodden for months at a time can have a propensity to abscess. According to Cullimore (2010) there is anecdotal evidence that keratomas are far less common in arid countries like Australia than here in the UK. Physically keratomas may be just as common in horses in Australia but there is less of an opportunity there for repeated abscesses, due to ‘gravel’, to ‘flag-up’ the keratoma in the first place.

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3.0 The Literature Review.

One Hundred and Seventeen Years of Keratoma

Writings.

3.1 Introduction

A study of the literature published on keratomas in the last one hundred and seventeen years discovers investigative dogma, unsubstantiated conjecture and little development of knowledge in the field. Knowledge gained prior to the discovery of radiographs and an appreciation of the histopathology of keratomas has not been developed.

The writings fall into two camps. Those who try to base their facts on science, for example Lungwitz (1887), Honnas (1988), Stashak (2002) and those who have a more anecdotal approach, such as Holmes (1949), Stashak (1987), Hickman and Humphrey (1988), Butler (2004), Devereux (2006) and Colles and Ware (2010).

Veterinary publications such as Hamir et al. (1992), Stashak (2002) and Floyd and Mansmann (2007) take a scientific approach.

However conspicuous in their more anecdotal approach are the recognised current farriery text books of Hickman and Humphrey (1994), Butler (2004), Van Nassau (2007) and Colles and Ware (2010).

Straddling the two camps with his scientific but pragmatic approach is Greet (2002).

Encyclopaedic equine health publications such as, Knottenbelt and Pasco (1997) Diseases and Disorders of the Horse and Horace Hays (2002) Veterinary Notes for Horse Owners, now in it’s 18th Edition are admittedly, entry level in their scope. However despite the apparent rarity of keratomas, each publication has reviewed their existence.It is imperative that these publications should accurately introduce the horse-owner to a subject. This is their duty. Yet for example Knottenbelt and Pascoe (1997) list keratomas under a heading of ‘Neoplastic Disorders’ and Horace Hays (2002), lists them under ‘Cancer and Equine Lumps and Swellings’. These publications do not have to be as detailed as their scientific counterparts but, never the less, should not contain anomalies.

Vetstream Ltd, is a contemporary online information resource for vets. Despite claiming to be peer reviewed by 400 vets this contemporary web-site still lists keratomas as being neoplastic in nature.

The first mention of an analysis of the histology of keratomas is by Lloyd et al, (1988). Up until this time it can be presumed keratomas were only confirmed visually. Lungwitz (1884) states that keratomas can only be diagnosed with certainty when they extend downwards to

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the lower border of the wall. Hickman and Humphrey (1994) give a keratoma’s clinical feature as hard glistening horn. These days, according to Boys Smith (2006) the mass can only be confirmed as a keratoma once an analysis of the histopathology of the mass has been carried out.

3.2 The Earliest Writings

In our contemporary times of radiography, histopathology, magnetic resonance imaging and venography it is fascinating to note that one hundred and seventeen years ago Anton Lungwitz (1884) described keratomas in a manner that is as relevant today as it was then. He described a keratoma as a keraphyllocele or horn leaf tumour projecting from the inner surface of the wall.

Lungwitz (1884) states “Its occurrence is rare. Its favourite seat is at the toe. It rarely causes lameness. It can only be diagnosed with certainty when it extends downwards to the lower border of the wall”.

Lungwitz (1884) then noted the classic inward deviation of the white line which reveals a keratoma to this day, by saying: ‘frequently the horn at this place crumbles away, from which there sometimes escapes a small quantity of dark greyish pus’.

Lungwitz (1884) went on to detail that keratoma removal should only be performed by a veterinarian, using the same technique of resection as that which is performed today- “should lameness persist, it will be necessary to remove a strip of the wall from the plantar border to the coronet. The fleshy leaves which have secreted the tumour must be extirpated and the surface of the os pedis well scraped or the growth will return”.

Greet (2002) agrees with Lungwitz (1884) that even though keratomas are found throughout the hoof, their favourite seat is often at the toe. Change the terminology Lungwitz (1884) uses from fleshy leaves to laminae and his words could have been published today.

3.3 The Term Keratoma

These space occupying masses of keratin are still known as keratomas today by all modern authors such as Butler (2004), Devereux (2006) and Colles and Ware (2010). However, writing in 1992, Hamir et al. stated “Keratoma- which implies a neoplastic growth is technically not an appropriate name for this lesion because the process does not appear to be a true neoplasm but is a hyperplasia or an abnormal regeneration of the superficial keratin.”

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Significantly however, Hamir et al. (1992) went on to say - “However the name (keratoma) is well entrenched in the clinical literature and will probably remain in use for some time.”

Hamir et al. (1992) have been proved correct. The name keratoma is still entrenched now nineteen years later. However, the definition of these lesions is changing in the literature.

3.4 The Definitions in the Literature of Keratomas

Up until Lloyd et al. (1988) the most common definition of keratomas was that of a horn tumour. For example, Lungwitz (1884), Dollar and Wheatly (1898), Holmes (1949),Hickman and Humphrey (1994).

Hamir et al.(1992) noted that the word tumour is not a suitable one for a hyperplasm. Some literature published post Hamir et al. (1992) has continued to use the word tumour in relation to these lesions, for example- Horace Hayes (2002), Butler (2004) and Colles and Ware (2010). These publications are of the more introductory, entry level writings on the subject, yet, as stated before, should they still not be accurate?

It is fascinating to compare the 4th and 5th editions of Stashak’s, ‘Adams Lameness in Horses’. Those published in 1987 and 2002 respectively. These two editions straddle the watershed writings of Lloyd et al (1988) Chaffin et al. (1989) and Honnas (1991). Therefore the updated 5th edition of ‘Adam’s Lameness in Horses’ contains no references to the word tumour in relation to keratomas and devotes three full pages to the study of keratomas, as opposed to merely one column, in the earlier 4th edition.

Conspicuous by the absence of employing the word ‘tumour’, when describing keratomas, are the more scientific based references post 1988 such as those by Stashak (2002); Ross and Dyson (2003,2011) and Redding (2007).

Keratomas are not tumours according to these authors. It could be argued that the continued use of an incorrect term is holding back the study of these lesions. Certainly the horse owner who mistakenly thought her horse had a cancer in the foot need not have worried that it was the end of her charge. For reasons of professional communication the correct terminology must be used. These masses of cornified tissue, (Honnas 1991), these aberrant, hyperplastic masses of keratin, Boys Smith (2011) will never metastasise into other structures of the hoof.

In employing the word ‘benign’ to these ‘tumours’ some references such as Devereux (2006), Ross and Dyson (2011) try to placate the linguistically stringent. However, is it not time, seeing that Lloyd et al. (1988) were writing 23 years ago that their writings were universally accepted?

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Greet (2002) with his pragmatic view notes that keratomas have been known as tumours but are strictly hyperplastic growths.

Van Nassau (2007) merely defines keratomas as a new piece of horn tissue. His book ‘Hoof Problems’ is, again an anecdotal, aimed at farriers, publication but at least does avoid the erroneous term ‘tumour’.

3.5 Where Keratomas Occur

Reviewing the literature published on keratomas reveals that if all the writings are to be taken as a whole, keratomas occur in any area of the hoof.

The earliest references by Lungwitz (1884) and Dollar and Wheatly (1898) do not name but obviously detail the cylindrical type of keratomas that are found behind the hoof wall. Lungwitz (1884) and Dollar and Wheatly (1898) state that keratomas are to be found most commonly at the toe and rarely at the quarter.

Wortley, (1906) states that keratomas are to be found at the toe or at the coronet. The only other mention of a keratoma at the coronet is by Hamir et al. (1992) who stated-

“The mass was relatively large at 65mm by 35mm, well demarcated and prominently laminated. Histopathologic examination of the mass revealed a thin collagenous capsule containing dense compacted layers of keratin that were periodically separated by areas of disorderly deposits of keratin and collagen”. The mass was confirmed as a keratoma histopathologically.

This example of a keratoma at the coronary band given by Hamir et al. (1992) is fascinating because it is by far the largest keratoma detailed in the literature. Presumably this must have been because it occurred at the coronary band and did not extend into the hoof. Therefore it occurred in an area of the hoof that would not restrict it’s development and would also tolerate a larger mass of the lesion before the onset of lameness.

Greet (2002) states that the lesion occurs typically in the toe region and less commonly elsewhere. He does also display a lesion at the heel however.

Van Nassau (2007) states these lesions can form at any place in the hoof capsule and he details the removal of a ‘side wall’ keratoma.

McDiarmid (2007) details the existence of a spherical keratoma in the frog and Colles and Ware (2010) also display a spherical keratoma in the frog. Personal communication with Personal communication with C.Colles Jan2011 reveals that he has encountered three keratomas in the frog during his practice as a vet.

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3.6 Shapes and Types of Keratoma

There is a lack of consistency of agreement in the literature on the shapes that keratomas can form.

Lungwitz (1884) and Dollar and Wheatly (1898) both describe, but do not name, what we would know today as a ‘cylindrical’ keratoma. Reports that do not mention the differing shapes that these masses of keratin come in, only acknowledge the cylindrical type of keratoma ( Hickman and Humphrey1994; Hamir Et al. 1992; Butler 2004; Stashak 2002).

When the keratoma is described as causing a smooth, semi-circular osteolytic track in the pedal bone we can presume that the author is describing a cylindrical keratoma. Spherical keratomas do occur behind the hoof wall but they will form a circular osteolytic area (Christman 2008) mirroring their shape.

Few references in the literature actually mention the differing shapes of keratoma. Fascinatingly however, as far back as 1906, J. Wortley was the first to list the shapes of keratomas as ‘elongated’, ‘ovid’ and ‘cone’. In modern terms we can read ‘elongated’ as ‘cylindrical’, ‘ovid’ as ‘spherical’ and ‘cone’ as ‘fan’ shaped.

Eighty two years after Wortley (1906), Lloyd et al.(1988) were the next to describe any shape other than that of a cylindrical keratoma. Lloyd et al. (1988) state that keratomas come in oval or conical shapes but it is not clear whether Lloyd et al. (1988) are describing a cylindrical keratoma oval in cross section, or a spherical keratoma which is oval in form.

Hamir et al.(1992) report them as being either conical or cylindrical.

Greet (2002) states there are two basic types of keratoma, the cylindrical and the spherical forms. He gives the most comprehensive account of a spherical keratoma anywhere in the literature. Fascinatingly Greet (2002) states and displays how cylindrical and spherical keratomas can be present together at the same site, behind the hoof wall. Greet (2002) also displays photographs of the removal of a 3cm diameter spherical keratoma.

Christman (2008) details the removal of three spherical keratomas from the same site, behind the hoof wall. The figures overleaf are taken from Christman (2008) Multiple keratomas in an equine foot, The Canadian Veterinary Journal. The horse detailed by Christman (2008) was a 19-year old arab gelding which had suffered trauma to the coronary band 15 years previously to going lame.

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Figure 3. The masses have been extirpated. Figure 4. Three spherical keratomas removed. Taken from Christman (2008) Multiple Keratomas in a Horses Foot.

Van Nassau (2007) reports a fan-shaped keratoma which sounds to be consistent with the ‘cone’ of Wortly (1906) and the conical form related by Hamir et al. (1992).

Boys Smith (2011), is the only reference to state that the shape of the keratoma is influenced by where it occurs in the foot. Boys Smith (2011) states that those behind the hoof wall are cylindrical in shape and those arising from the sole and the frog are spherical. This contradicts both Greet (2002) who displays cylindrical and spherical keratomas occurring together and Christman (2008) who details the removal of 3 spherical keratomas from behind the hoof wall.

McDiarmid (2007) details the removal of a spherical keratoma from the frog.

There is no mention in the literature of a cylindrical form of keratoma occurring anywhere else other than behind the hoof wall.

Sadly in the literature there is no attempt to reason why keratomas form different shapes. Certainly those keratomas that have been detailed in the frog are always spherical in shape, Mc Diarmid, A. (2007).

Thus there is still a lack of complete information about the shapes of keratomas; 3 shapes appear to exist: cylindrical; ovid/spherical and fan or cone.

There is supposition that the shape keratomas form within the hoof is influenced by position although this is not well reported.

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3.7 The Origin of the Germination of the Keratoma

There is no agreement in the literature on the anatomical origin of the development of keratomas. The majority of references give the area of the foot in which keratoma germinate as being at the coronary band; Lungwitz (1884), Greet (2002), Van Nassau (2007), Boys Smith (2011).

It is generally accepted that keratomas are not always found extending from the coronary band to the most distal surface of the hoof wall,(Greet 2002). The study by Boys Smith et al. (2006) of twenty six horses undergoing complete or partial hoof wall resection details fourteen (54%) that underwent complete resection and 12 (46%) that underwent partial resection. Those that underwent partial resection did so “because the lesion did not extend to the coronary band”.

‘A sterile metal probe was inserted into the solar drainage tract to determine the direction and proximal extent of the abnormal tissue’. (Boys Smith et al.2006).

In fact, in practice, the removal of the lesion by resection of the hoof wall does not involve direct surgery to the coronary band as this would severely damage the germinative layer of cells (Greet 2002, pers.comm., J.Tipp April 2011). In the study performed by Boys Smith et al. (2006) all surgery was performed distal of the coronary band.

A failure to remove the lesion in its entirety will result in it regenerating, (Lungwitz 1884; Greet 2002). The fact that resection never interferes with the coronary corium surely means that regeneration is independent to the row of germinative cells at the coronary corium.

Hickman and Humphrey (1994) like Dollar and Wheatly (1898) looks at the lesion from the other direction. Hickman and Humphrey (1994) states that the tumour extends varying distances up the wall from the bearing surface towards the coronet.

Boys Smith (2011) states that keratomas can originate from any point on the inner surface of the hoof wall, the sole or the frog. Keratomas behind the hoof wall are given the most description and there are no references that

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3.8 A etiology- Trauma

The argument for direct trauma being the trigger for development of these lesions is present in all the literature and yet, it is also accepted that keratomas have developed in feet where there is no history of trauma, Honnas (1997).

Stashak (1987) states that- (In the healthy hoof) – growth of the hoof wall is primarily from the stratum germinativum of the coronary epidermis towards the ground. Whereas most of the laminar epidermis normally keratinises minimally, primary laminae keratinize as the mass moves distad. Trauma or inflammation of the area will stimulate greater keratinization. Stashak (1987) is describing the healthy hoof and not the laying down of rogue keratin cells in the form of a keratoma.

Personal communication with Boys Smith Jan 2011 informs that it is a very well-known medical and veterinary fact that cells can start to proliferate as a result of physical or chemical irritation.

Will an upset cause more keratin to be produced other than in the hoof wall itself? A hyperplasia by definition is an increase in the number of cells but with no loss of control by the body (pers. comm. Fews 2011).

Throughout the literature, trauma to the hoof is the most commonly cited cause of keratomas. Lungwitz (1887) gives compression, bruising, a toe crack or a direct impact such as a tread or caulkin wound. Wortley, J. (1906) states “they are caused by injury, irritation, blow or tread. Also by the poor practice of the hammering down of the toe-clip of the shoe by a farrier to lay the clip at the angle of the hoof wall”.

Charles Holmes (1949), details Keraphyllocele as a horn tumour ‘undoubtedly brought about by anything that is liable to set up an inflammatory condition of the horn secreting structures’. Ie. sandcracks, treads and again a hammering of the toe-clip home. Holmes (1949) goes on to say:

“I have seen some heavy cart horses very stubborn in picking up the hind feet; so much so, the doorman has deliberately hit the wall of the foot a good blow with the nailing-on hammer with the idea of making the horse snatch up the foot: it is done without thinking what might be the after-effects. I am pleased to say, however it is the practice of only a few men, and I hope it will soon cease altogether; it is a practice to be deprecated very strongly”.

Thankfully, in our modern times, with attentive owners of mainly pleasure horses, Holmes’s prayers have been answered. Negligent farriers no longer strike the hoof wall in this manner and yet keraphyllocele, as he called them, still exist.

There is no proof that these examples of poor farriery practice are directly responsible for keratomas. Every farrier admits that his strength is far outweighed by that of the horse. If the horse weighing approximatly1300lbs can gallop at 25mph, during which time one foot

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supports its whole weight, how can the strength of a man influence the creation of keratomas in the hoof.

It could be presumed that this ‘trauma’ to the hoof caused by the clips of the shoes would result in examples of lesions at the distal border of the hoof, in the area of the clips. Yet there is no mention in the literature as to a propensity for keratomas to occur at the sites chosen by farriers, to place the clips of their shoes.

In Wortley and Holmes’s day the majority of horses were working on farms , and drawing carts or carriages. These would have been shod with a toe clip on the hind feet because they were not doing fast work.

The only horses which are still shod behind in this way today are race horses. I do not hammer clips home but I do see instances where race horses that have a heavy foot fall in the hind feet press the toe clip into their own feet. The toe of the foot can even be distorted inwards by the pressure of the clip on the hoof capsule as the horse pushes his own shoes back, under his feet, Figure 3 below.

Figure 5 Inward deviation of the white line at the toe due to pressure from the clip of the shoe.

Figure 5 above displays no haemorrhaging in the area of the clip to signify trauma and there is no documentation of thoroughbreds, of any age being in the majority today to suffer keratomas.

Would a horse that is suffering a clip that is pressed too hard into the wall of a foot not be lame? He would tell you if trauma, sufficient to inflame the hoof and be more than he could normally cope with, is occurring.

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The fact remains that modern horses suffer many traumas to their feet and yet keratomas are still a rare lesion. The modern disciplines of show-jumping, eventing and polo will provide as many instances of treads, stamps and bangs as the beasts of burden of our forefathers and yet keratomas still remain rare.

Vale (1997) and Butler (2004) cite hoof grooving as a cause of keratomas but sadly do not detail as to why this practice had previously taken place. Hoof grooving is an anecdotal therapy which attempts to; increase flexibility and subsequent blood flow in the treatment of navicular disease, Hickman and Humphrey (1994); tries to increase flexibility to alleviate a contracted foot, Hickman and Humphrey (1994); increase the flexibility of the hoof capsule in an area for the treatment of side bone, Butler (2004); address the initial onset of laminitis (Rooney 2011).

In 1977, two years after the Farrier’s Registration Act, Lieutenant-Colonel John Hickman M.A., F.R.C.V.S., Reader in Animal Surgery at the University of Cambridge , fulfilled the need at the time for a contemporary text book, with his- Farriery- A Complete Illustrated Guide. Seventeen years later, the second edition was published, renamed ‘Hickman’s Farriery. A Complete Illustrated Guide’. For this updated version John Hickman partnered up with Martin Humphrey, B.V.M.S., M.R.C.V.S., Dip. W.C.F.

‘Hickman’s Farriery’ (1994) is, to the present day, the textbook of choice for the British Apprenticeship in Farriery.

Writing in the preface to the book, Hickman and Humphrey (1994) acknowledge that all the best known authors on farriery have been consulted and the information collated. Their bibliography lists 63 references, spanning the years from 1564 ( Fiaschi, Caesar. Traite de le maniere de bien emboucher, manier, et ferrer les chevaux. Dedie au Roi Henri 2nd , c.Perrier, Paris) to 1987 (Stump,J.E. Anatomy of the Normal Equine foot, Including Microscopic Features of the Laminar Region, J.A.V.M.A. Vol. 151, No 12 , P.1588). Of course it would be disingenuous to presume every reference contained a piece on keratomas but despite such an admirable bibliography, Hickman, who was also the first editor of the Equine Veterinary Journal, does little to address the mystery of keratomas.

According to Hickman and Humphrey (1994) keratomas are horn tumours which develop on the inner aspect of the wall and sometimes in the sole -

“The tumour is composed of hard glistening horn, generally cylindrical in shape, ranging from 6mm to 40mm in diameter and extending varying distances up the wall from the bearing surface to the coronet. It is first detected at the bearing surface where it appears as a mass of hard horn, between the wall and the sole, which deflects the white zone inwards. As the tumour increases in size lameness may gradually develop”.

The words “extending varying distances up the hoof wall from the bearing surface to the coronet” seem to imply that Hickman and Humphrey (1994) consider keratomas to originate at the distal border of the foot.

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Hickman and Humphrey (1994) contradict Lungwitz (1884) who states that the keratoma “extends downwards to the lower border of the wall”. This contradiction is despite Lungwitz (1884) being referenced by Hickman and Humphrey (1994).

However, maybe Hickman and Humphrey (1994), who had the Farriery Apprentice in mind when they were writing their book, were merely warning the unscientific student of the sinister growth that is indicated by ‘a hard area of glistening horn, causing an inward deviation of the white line’. Yet again however, this light assessment of keratomas, in the most influential farriery text book in the United Kingdom today, is based on an unproven, anecdotal theory.

Van Nassau (2007) cites the banging of the stable door for attention, as a cause of keratomas. Of course it is as impossible to prove as disprove that trauma is the cause. Horses cannot be observed at all times. Many a horse owner has walked their field in search of a cause of their horse’s injury, to no avail. Until traumas are observed and subsequent development of keratomas noted, surely we cannot be certain that direct trauma is responsible for these lesions.

Horses that are likely to suffer a high incidence of trauma such as those show jumping, eventing and hunting do not appear to supply the majority of keratoma incidences. Data from the 26 horses studied by Boys Smith et al.(2006) and the 22 horses studied by Linnenkohl (2011) show no preference of age, breed, sex or discipline.

There is a preference however of incidence of keratoma in front feet over hinds. In the Linnenkohl (2011) data, twenty out of twenty two cases or 91% concern the front feet and front feet supplied seventeen out of twenty two cases or 65% of the keratomas in the Boys Smith et al. (2006) data.

Maybe front feet suffer more incidents of trauma, they are certainly more likely to bang the stable door. Or maybe simply because 60% of the horse’s weight is taken by the front feet, front feet, if they contain a keratoma, are more likely to go lame than affected hinds.

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3.9 – Aetiology- Abscesses

Along with trauma, incidences of abscessation have been cited as something that ‘is liable to set up an inflammatory condition of the horn secreting structures’, Holmes (1949), and therefore the development of a keratoma.

Boys Smith (2011) also writes that ‘The keratoma could be secondary, with proximal extension of an abscess towards the coronary band causing disruption of the germinal epithelium and predisposing to keratoma formation.

Dollar and Wheatly (1898) also regard keratomas to be secondary to abscesses but also had another theory on their development –

‘After the pus has escaped through a passage established by pressure or through an artificial opening, the space left is only partially filled up, and, in consequence of the inflammation, small prominences form on the free margins of the sensitive laminae, which are the chief agents in the production of keratomata’.

This theory of the space occupying lesion developing to fill the cavity left in the foot after an abscess is a fascinating one but sadly it finds no later favour with any other authors on keratomas. The term ‘free margins’ appears to be no longer in use.

Dollar and Wheatly (1898), however do state that Keratomata may be caused by chronic inflammation unaccompanied by suppuration.

Abscesses are well associated with keratomas. Abscessses have certainly flagged up the existence of the space occupying mass of the keratoma in many cases. This is because it is thought the existence of the keratoma at the white line on the solar surface of the foot can allow for the disruption in continuity of the solar-mural junction, Greet (2002). In other words the keratoma at the white line gives a path for infection in the hoof.

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3.1 Farriery Treatments

The one subject in the study of keratomas where all authors agree is the shoeing protocol.

Prior to the invasive modern-day surgical technique of resection, Lungwitz (1884); Dollar and Wheatly (1898); Holmes (1949); Hickman and Humphrey (1994) all favour shoeing with an ordinary open-heeled shoe, which is ‘seated out’ in the area of the keratoma. This is recommended so that no ‘pressure’ is placed on that part of the hoof where the lesion exists. No nails must be driven near the keratoma, Hickman and Humphrey (1994).

This ‘pressure relieving’ technique is admirably put into practice by Bradbury (1987) in his Fellowship thesis for the Worshipful Company of Farriers entitled ‘A Description of some Actual Cases Requiring Special Consideration’.

The example cited by Bradbury (1987) is of an eighteen year old thoroughbred with a keratoma confirmed in the traditional visual manner and not histopathologically, directly in the toe area of the off hind foot. This horse was shod with an open heeled shoe which had a set down toe, directly in the area of the keratoma. This shoeing was complemented with hoof grooving. With advice from the veterinary surgeon, the toe was grooved directly at the toe and just at the start of the toe quarters (figure 4 below). Using the combination of these two techniques it was thought that ‘pressure’ from the space occupying lesion was relieved and soundness ensued. This horse was kept sound for a year with this treatment (pers. comm., D. Bradbury Jan 2011) despite a shoeing interval of ten weeks! D. Bradbury (2011) also reports that the rate of hoof wall growth was faster in the affected hind compared with it’s opposite.

Figures 4 and 5 overleaf are taken from Bradbury (1987). Figure 4 displays the hoof grooving that was carried out on the hoof capsule and Figure 5 shows how the hoof grooving allowed the hoof capsule at the toe, over the site of the lesion, to bow out, thereby it was thought, relieving the pressure caused by the unconfirmed keratoma in the hoof capsule.

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Figure 6. Hoof grooving Figure 7. Toe ‘bows’ out.

Figures 4 and 5 taken from Bradbury (1987).

Butler (2004) referred to Bradbury (1987) stating that this grooving allowed- “The tumor to grow out with the wall.” However Bradbury’s (2011) personal communication informed me that the horse was sold before this was confirmed. Cases ‘sold and lost to science’ unfortunately do occur and are familiar to the student of keratomas.

Despite hoof resection being detailed in Lungwitz (1884), it was still not in vogue in the early nineteen eighties. Personal communication with D. Bradbury (Jan 2011), tells of the reticence by both the veterinary surgeon and the owner to perform such invasive surgery at the time.

These days it is common veterinary practice to resect the lesion as soon as it is discovered using a similar technique as that detailed by Lungwitz (1884).

A heart bar shoe for example can be fitted once the defect is dry and there are signs of keratinisation of the area. The heart bar shoe stabilises the hoof capsule and enables the frog to contribute to weight bearing. Further hoof wall stability can be achieved by applying a metal bridging plate across the defect held on with acrylic glue, Boys Smith (2006).

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3.11 Recovery Post Surgery

It remains that if the complete removal of the keratoma is not successful during surgery, they will grow back, Lungwitz (1884), Dollar and Wheatly (1898), Greet (2002),Boys Smith et al.(2006).

Vale, M.M. (1977) has a pessimistic view as to the return of the lesion stating-

“Recovery is guarded if pressure necrosis of the underlying sensitive laminae occurs”.

However the majority of references state that the prognosis for a full recovery is good.

3.12 Histopathology

Hamir et al. (1992) allude to the paucity of reported cases of equine keratoma that have been studied histopathologically. Redding (2007) maligns the same fact.

Interestingly for those who propound direct trauma as the cause of keratomas, Hamir et al.(1992) state-

“Inflammatory cellular reaction was not evident in either the mass or the tissue surrounding the mass”

Redding (2007) also states that no evidence of inflammatory infiltrate had been found histopathologically. However inflammatory infiltrates can be present if there is secondary bacterial infection (Boys Smith 2011).

Once the mass has been extirapated it is commonly fixed in 10% formalin followed by routine histopathological processing.

Boys Smith (2011) states; Histologically, classical keratomas are composed of a cystic structure filled with concentric layers of compact keratin. This is produced by a layer of keratinising stratified squamous epithelium (which conceivably originates from epidermal lamellae) that lines the cyst. Ideally, this epithelium should be identified to confirm the diagnosis, but it is often absent in submitted biopsies; in these cases, the presence of concentric layers of compact keratin together with a typical gross appearance of the lesion is compatible with the diagnosis of a keratoma.

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4.0 The Information Gathering Exercise

4.1 Introduction

Other than the literature review, this study was to investigate whether farriers could flag up the presence of keratomas in horse’s feet before they cause lameness. The only reference I found to the fact that keratomas are present in horses feet for prolonged periods of time before they cause lameness was by Knottenbelt and Pascoe (1997). Anecdotal evidence abounds from farriers that see keratoma like lesions in horses feet before the onset of lameness.

In an effort to gather more examples of erroneous horn in white-lines the three most widely read farriery journals in the northern hemisphere were contacted. They were most helpful, placing my appeal for examples in prominent positions in their publications and even, in the case of The European Farrier’s Journal, on the front cover. Overleaf is an example of the terrific publicity given to me by these publications.

In total I received seven replies to my appeals which are suitable for this study. I have chosen the five examples with photographic evidence, as this is how they are encountered by farriers.

An American farrier, Mikel Dawson, practising in Denmark provided the fascinating case of a young horse that has suffered no history of trauma. A radiograph of the foot displays an osteolytic area in the pedal bone in relation to the lesion pictured. The lesion is yet to be extirpated and sent for histopathology.

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Figure 8. Appeal in the European Farriers Journal

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4.2 Cases Gathered

There follows the five most suitable replies to my appeals.

1. Mikel. A year and a half old warm blood with an inward deviation of the white-line with no history of lameness, pictured below,

Figure 9. Figure 10.

Subsequent radiographs display an osteolytic track in the pedal bone.

2. Dillon. A fifteen year old cob with no history of lameness in his right hind.

Figure 11. Figure 12.

Figure 13. Dillon’s radiograph displaying a small area of osteolysis.

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3. Pepper. 23year old riding horse having suffered many abscesses in the last three years in the off hind and with three times the growth rate of the opposite hind.

Figure 14. Pepper’s haemorrhaging in the sole and cavities from abscesses.

Figure15. The same foot as in figure 12 a month later.

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Figure 16. Radiograph of Pepper’s hoof- “suggestive of a space occupying lesion” ( pers. comm., Greet, Jan 2011)

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4. Rosco. An eighteen year old Irish Draught gelding having suffered an intermittent lameness for 6 months. No history of abscessation.

Figure 17. Pre.operation solar view. Figure 18 Rosco’s operation.

Figure 19. Mass removed.

Figure 20 overleaf. Rosco’s subsequent histopathology report.

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5. Holly. 12 year old, coloured cob with no history of lameness.

Figure 21. Inward deviation of the white-line in Holly’s off hind.

Figure 22. Erroneous lesion in the white-line. Figure 23. Biopsie of horn. Pictures taken 28th April 2009.

Figure 24. Holly’s foot 2nd March 2010. Still displaying an inward deviation of the white-line but still no lameness.

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Figure 25. Histopathology report from the biopsies taken from Holly. The features are consistent with a keratoma but are not large enough to confirm a keratoma.

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4.3 Discussion of the Cases Gathered

The original premise of this study was to investigate the possibility that farriers could flag up keratomas before the onset of lameness by sending a biopsy such as in figure 20 for histopathology as in figure . This triggered the literary review and the appeals for more examples of erroneous horn like Holly’s.

In the course of my study I discovered that this was not possible for a farrier to supply enough material and from the correct site in the foot to aid a histopathologist in a diagnosis of a keratoma. Boys Smith (2011) states that ideally the keratinising stratified squamous epithelium should be identified to confirm the diagnosis of a keratoma or failing that, the presence of concentric layers of keratin and the gross appearance of the lesion.

However successes such as Mikel, Dillon and Pepper are to be celebrated. In each of these cases my publicity prompted the farrier to discuss the lesion with the owner, action was taken and the future insidious lameness was avoided.

5.0 Conclusions

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This study has highlighted the lack of detailed anatomical knowledge in relation to the precise site of keratomas and the effects of tissue growth on their development and satisfactory extirpation.

A study of where keratomas originate from is yet to be published. We only get interested in them when they cause lameness, when they are already established.

It is fascinating to hypothesise how the pioneers of keratoma study, before the invention of radiographs, recognised keratomas in the same way as we do today. Many of their observations must have been done post-mortem. Perhaps in a time when the horse was still the most common form of personal transport, our forebears were forced to study lameness more than we do today. Or it may have been that because of the economic ties of keeping a horse, they were more likely to be euthanized instead of being allowed to end their days in a pasture, as is the case today. Obviously the best way to study and expiate a keratoma is post-mortem. There are no modern reports of histopathological analysis in vitro.

My literary review has brought home to me the extent of their knowledge in Victorian times. It is all too easy, with our modern diagnostic tools, to forget the advances from earlier studies. We patronise and ignore their thinking to our peril. How many horses over the years would have enjoyed productive lives if methods detailed over a century ago had been implemented? Accurate knowledge is truth. An apathetic attitude to learning continues to allow knowledge levels in our craft of farriery to slide back from levels attained at the turn of the last century.

A study of the historic literature has shown how important pieces of information can be lost and not passed on to subsequent generations. This is where a ‘literature search’ approach shows merit.

Literature searches are usually only done for scientific approaches such as scientific or journal paper publishing.

Hence the information in books (unless referenced) must be recognised as not necessarily historically comprehensive and can be based on unscrutineered opinion and dogma (Reilly 2011 pers comm).

The fact that keratomas are a rare form of lameness has never been in doubt.

My attempts to discover if keratomas are more prevalent than we think have not been successful. Appeals for examples of opaque, erroneous areas of horn in the white line noticed by farriers reading: The American Farriers Journal, The European Farriers Journal and the UK wide, Forge Magazine has only gathered a handful of examples.

Farriers cannot provide biopsies of erroneous horn large enough and from the correct part of the hoof wall to enable histopathological vets to draw conclusions. However, a visual

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assessment of an area of erroneous horn in the white line can lead to an early resolution of, as J. Wortley writing in 1906 elegantly put it, ‘the mischief’.

In order to quantify how many horses do have space filling masses of keratin, which could eventually cause lameness, a nationwide MRI study of as many horses as possible would have to be conducted.

Sadly, with an individual MRI study retailing at £750 as I write, we will have to wait a few years for the price to come down, before such a prospective study is possible and we can discover what is occurring behind the hoof wall.

With modern electronic methods, a permanent data-base could be established so that farriers can use it to record the lesions they see. Better publicity and a more informed profession may result in a breakthrough in knowledge in this field. The need for detailed and extensive data gathering has been unearthed by this study.

Until this time, we will continue to base our knowledge of keratomas largely on conjecture.

Therefore I hope my study has:

a. Drawn the knowledge base about keratomas together in one place, during the information gathering exercise.

b. Highlighted some of the areas of controversy about keratomas including the lack of precise definition and histopathological understanding.

c. Detailed some of the difficulties associated with their study d. Indicated some of the suspect areas for the future study of keratomas.

Word count – 9300 words.

Post Script

Recent personal communication with Debra Fews BSc BVM&S Cert VA DipRCPath MRCVS informs me that even the term hyperplasia may not be a suitable one for these masses of keratin, as hyperplasia is a term used with live tissue and keratin is not live.

Tragically the example named as Mikel in my results suffered an accident in the field and had to be euthanized recently. The farrier managed to obtain the hoof and it awaits importing into this country and undergoing histopathological analysis.

Hopefully, in the near future we can add to the work of the last one hundred and seventeen years.

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6.0 References

Back,W., van Schie, M.J.J. and Bosch, G. (2007) Keratoma and its Cutting Edges. Equine Vet. Ed. 19, 288-289.

Booth.T. 2010.UK Vet- Vol 15 No 2 UK Vet Publications, Kennet Building, Woolton Hill, Newbury, Berks. RG20 9UT

Boys Smith, S.J., Clegg, P.D., Hughes, I., Singer, E.R. (1994-2004) Complete and Partial Hoof Wall Resection for Keratoma Removal, Equine Vet. Journal, Wiley Online Library.

Boys Smith, S.J. (2011), Keratomas: their aetiopathogenesis, diagnosis, treatment and outcome. Rossdale and Partners, Cotton End Road, Exning, Newmarket, CB8 7NN

Bradbury,D. FWCF (1987) A description of some Actual Cases Requiring special Consideration. FWCF Thesis.Clay Cross. England

Christman, C. (2008) Multiple Keratomas in an Equine Foot. Canadian Veterinary Journal 49(9): 904-906

Dollar, A.W. MRCVS and Wheatley, A. MRCVS (1898) A Handbook of Horseshoeing. David Douglas, 10 Castle Street, Edinburgh.

Greet T. (2002) Keratoma of the hoof capsule. Chapter 10, Corrective Farriery, A Textbook of Remedial Horseshoeing, Edited by Simon Curtis 2002, R&W Publications Ltd, Suites 3&4, Kings Court, Willie Snaith Road, Newmarket, Suffolk CB8 7SG, UK.

Hamir,A.N., Kunz,C., Evans,L.H. (1992) Equine Keratoma. J Vet Diagn Invest 4:99-100

Hickman, J., Humphrey, M., (1994) Hickman’s Farriery. J. A. Allen and Co. Ltd, 1 Lower Grosvenor Place, London. SW1W 0EL

Holmes, C,M. FWCF(1949) The Principles and Practice of Horseshoeing. The Farrier’s Journal Publishing Co., 48 Spencer Place, Leeds

Honnas,C.M. (1997) Keratomas of the Equine Digit. Equine Vet. Ed. 9 203-207

Horace Hays, M. (2002) Veterinary Notes for Horse Owners 18th Edition. Ebury Press, Random House, 20 Vauxhall Bridge Road, London. SW1V 25A

Linnenkohl, W. (2011) Bell Equine, Bucher’s lane, Mereworth, Maidstone, Kent. ME18 5GS

Lungwitz, A. (1884) A Text Book of Horseshoeing. University of Pennsylvania, J.B. Lippincott Company, Philidelphia.

Mc Diarmid, A. (2007) Keratoma from the frog corium of a horse. Equine Vet Ed. 19 (6) 285-287

O’Grady.S, Horne,P.A., (2001) Lameness Caused by a Solar Keratoma. Northern Virgina Equine http://www.equipodiatry.com. J Equine Vet. Ed. American Edition.

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Pickersgill, C.H. (2000), Recurrent white line abscessation associated with a keratoma in a riding pony. Equine Vet. Ed. 12 (6) 286-291.

Redding (2007) in Floyd A.E., Mansmann R.A. (2007) Equine Podiatry, Saunders, 11830 Westline Industrial Drive, St. Louis, Missouri 63146

Tipp, J. (2011) Personal communication. Fyrnwy Equine Practice, Whitmore Lane, Baschurch, Shropshire.SY4 2EY

Vale, M.M. (1977) The Illustrated Encyclopedia for Horsemen. Equine Research Inc. PO Box 535547. Grand Prarie, Texas. USA. 75053

Van Nassau R. (2007) Hoof Problems, pages 99-106. Kenilworth Press, Quiller Publishing Ltd, Wykey House, Wykey, Shrewsbury, SY4 1JA

Wortley.J,(1906). The Horse, Its’ Treatment in Health and Disease. The Gresham Publishing Co., 34 Southampton Street, Strand. London.

7.0 Glossary

Taken from Saunders Comprehensive Veterinary Dictionary. (2007) Blood D.C., Studdert, V.P and Gay C.C. Saunders Elsevier Ltd, (http://www.elsevier.com)

Aberrant- deviating from the norm

Benign- not malignant, not recurrent; favourable for recovery, mild and not malignant, kind hearted, gracious. Non cancerous

Benign Tumour- does not spread to other parts of the body

Hyperplasia- abnormal increase in volume of a tissue or organ caused by the formation and growth of new normal cells

Keratoma/keratosis- Any horny growth on the skin, such as a wart or callosity; a firm elevated circumscribed area of excessive keratin production.

Malignant Tumour- a tumour which destroys the tissue in which it arises and does spread to other parts of the body

Neo- word element. (Gr.) new,recent.

Neoplasm- 1.a TUMOR. 2. Any new and abnormal growth, specifically one in which cell multiplication is uncontrolled and progressive. Neoplasms may be benign or malignant

Squamous- composed of scales

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Tumor- Neoplasm; a new growth of tissue in which cell multiplication is uncontrolled and progressive. A cancer. A swelling caused by a proliferation of cells.

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