MR3127BSc (Hons) Dissertation Farriery Science

A pilot study of Lateral Hock Angles in a random selection of 44 diagnosed cases of Bone Spavin

compared to 18 cases with clear pathology.

Angus Wiseman FdSc AWCFStudent number: 20107101005907

Word Count:

Acknowledgements

Many thanks to Mark Caldwell and staff at Myerscough college for their tuition

and support over the duration of this course, special thanks to Mrs Lorraine

Allan for her excellent guidance at the eleventh hour.

Thanks to my father for writing direction and editing skills and my wife and two

boys for their patience and understanding of being neglected and ignored in

my quest to further my education.

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Abstract

Introduction. Hock conformation is frequently associated with hind limb

lameness in horses, with sickle-hocked conformation commonly referred to as

being a causative factor in the development of bone spavin.

Study design. A quantitative, experimental pilot study.

Hypothesis. Horses with bone spavin have a smaller hock angle than those

with no diagnosis.

Aim. To test the hypothesis by comparing the measured lateral hock angle of

horses diagnosed with bone spavin with those showing no abnormal

pathology of the hock joint.

Objective. To develop a method of measuring lateral hock angle to

characterise lateral hock angle in diagnosed and non-diagnosed cases of

bone spavin.

Materials and Methods. Lateral hock radiographs of horses that had been

positively diagnosed with bone spavin by a veterinary hospital were analysed

using Ontrack Equine® analysis software to measure lateral hock angle,

these measurements were compared to measurements taken following the

same protocols from lateral hock radiographs taken by the same veterinary

hospital of horses that showed no abnormal joint pathology.

Results. The radiographs of horses diagnosed with bone spavin recorded a

mean lateral hock angle of 4.48° less than those showing no abnormal joint

pathology

Conclusion. Horses with a smaller hock angle may be predisposed to the

development of bone spavin although other factors need to be considered.

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Significance. With a better understanding of hock conformation used in

conjunction with other clinical signs farriers may be ideally placed to instigate

earlier veterinary investigation into the diagnosis of bone spavin.

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Contents

Title Page 1

Acknowledgements Page 2

Abstract Page 3

Table of Contents Page 5

Chapter 1- Rationale and Introduction 1.1 Rationale Page 7

1.2 Equine tarsus, hock Page 8

1.3 Bone spavin Page 10

Chapter 2- Literature Review 2.1 Introduction Page 14

2.2 Equine conformation Page 14

2.3 Hock angle Page 17

2.4 Bone spavin Page 19

2.5 Radiography of the hock joint Page 21

2.6 Taking Measurements from radiographs Page 22

Chapter 3- Methodology 3.1 Introduction Page 23

3.2 Hypothesis Page 23

3.3 Problem definition or aims Page 23

3.4 Aim Page 24

3.5 Objectives of the research Page 24

3.6 Objective Page 25

3.7 Research design Page 25

3.8 Materials and methods Page 26

3.9 Reliability and validity Page 28

3.10 Standardisation Page 29

3.11 Sample size and inclusion criteria Page 30

3.12 Data collection Page 30

3.13 Data analysis Page 31

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3.14 Interpretation of results Page 31

3.15 Validation of results Page 32

3.16 Ethical considerations Page 32

Chapter 4-Results 4.?

4.?

4.?

Chapter 5-Discussion

Chapter 6-Conclusion and recommendations 6.1 Conclusion

6.2 Recommendations for further study

References

Appendices

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Chapter 1 – Rationale and Introduction1.1. Rationale

Several authors including (Rooney 1968, Hickman 1977, Horace Hayes 1978,

Butler 1985a, Eskell et. al 1998, Gough and Monroe 1998, Marks 2000,

Jackman 2006,) cite cases of horses with sickle hocks, that is an acute or

small hock angle, which can make them predisposed to bone spavin.

However, in a small observational comparison study carried out by the

researcher, of horses that had been positively diagnosed with spavin, these

opinions were contradicted with 100% of the observed cases studied having a

post-legged conformation, i.e. a more upright or larger hock angle. (See

Appendix 1.)

This prompted the researcher to undertake this pilot study to investigate if

there is a predictable lateral hock angle range into which horses with bone

spavin fall. The results of this study, when used in conjunction with other

indicators, may hopefully enable farriers, horse owners and other equine

health care professionals to recognise earlier signs of the condition, prompting

pre-emptive investigation and the possible implementation of treatment and

management regimes to enable the horse to remain sound longer and

improve its welfare.

1.2. Equine Tarsus, Hock.

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The hock or tarsus of the hind leg corresponds in position to the knee of the

front leg of the horse, and is similar in structure and positional function to the

ankle joint of man (Butler 1985). Fig. 1.1.

The equine hock is arranged in three main layers; the upper or proximal layer,

the middle layer and the lower or distal layer (Clayton 2003).

It comprises of ten bones and four joints, the most proximal joint is the

tibiotarsal joint, a high motion ginglymus joint involving the tibia, talus and

calcaneus. The talus and calcaneus rotate dorso-plantarly around the distal

articular surface of the tibia. Deep grooves form the articular surface of the

talus, and are known as the trochlea, covering almost twice the surface area

of that of the corresponding articular surface of the tibia. The grooves are

directed at an angle of twelve to fifteen degrees dorsolateral to the limb’s

sagittal plane.

The three lower joints are low motion arthrodial joints and in a proximal to

distal direction are the proximal intertarsal joint, involving the distal aspects of

the talus and calcaneus and the proximal aspect of the central tarsal bone;

the distal intertarsal joint, which involves the central tarsal bone proximally

and the third and fused first and second tarsal bones distally; and thirdly the

tarsometatarsal joint, which lies between the distal row of tarsal bones and the

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Fig. 1.1.

proximal aspect of the metatarsal bones. The fourth tarsal bone spans the

distal intertarsal joint laterally and articulates with the proximal intertarsal and

tarsometatarsal joints. (Butler 1985, Riegel and Hakola 1996, Stashak 2002,

Clayton 2003, Jackman 2006, Raynor 2006). Fig.1.2.

Fig. 1.2.

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A: Trochlea.

B: Talus.

C: Calcaneus.

D: Calcaneal Tuber.

E: Sustentaculum tali.

1: Central tarsal bone.

2: 1st and 2nd Tarsal bones (fused).

3: 3rd tarsal bone.

4: 4th tarsal bone.

5: 2nd metatarsal bone.

6: 3rd metatarsal bone.

7: 4th metatarsal bone.

(Image reproduced from, Raynor, 2006).

The equine hock is complex and is the hind limb joint most commonly affected

by lameness (Blaik et. al 2000, Baird 2002, Gnagey et. al 2006, Jackman

2006, Vanderperren et. al, 2009,).

1.3. Bone Spavin DefinitionBone spavin is considered to be the most common cause of tarsal lameness

in horses (Gough, and Monroe 1998, Eskell et al 1999, Björnsdóttir et al.

2000, Stashak 2002, Jackman 2006, Byam-Cook and Singer 2009, Lamas et.

al 2011) and has been recognised as such since c.1440 (Oxford English

Dictionary 2012).

Bone spavin disease is an osteoarthritis and periostitis involving one or more

of the three lower hock joints. The distal intertarsal and tarsometatarsal joints

are the most commonly affected, with the proximal intertarsal joint being least

likely to develop the condition (King and Mansmann, 1997 Bjornsdottir et al

2000, Stashak 2002, Dick Vet 2012). It has been variously defined as a lay

term used to denote degenerative joint disease of the tarsus (Baird 2002).

However, Stashak (2002) believed that distal tarsal osteoarthritis more

accurately described the condition and Byam-Cook et al (2009) referred to the

condition as osteoarthritis of the small tarsal joints. According to Blaik et al

(2000), lameness localised to the tarsus has been reported to account for up

to 80% of chronic low grade lameness in the horse, a proportion supported by

evidence from Murray’s (2005) findings that tarsal degenerative joint disease

is a common cause of lameness in horses and the most common cause of

tarsal lameness.

AetiologyPoor conformation traits such as sickle hocks and cow hocks are commonly

believed to be one of the main causative factors in the development of bone

spavin (Butler 1985, Riegel and Hakola 1996, King and Mansmann 1997,

Gnagey et al 2006, Dick Vet 2012). Poor shoeing and trimming have also

been noted as contributing to the development of bone spavin in any horse

regardless of their conformation (King and Mansmann 1997, Dick Vet 2012).

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Stashak (2002) claimed bone spavin is most frequently observed in mature

horses that are ridden hard at a gallop and canter; horses that jump and

Western horses used for reining, roping and cutting. Similarly, studies by

Eskell et al (1999), Björnsdóttir et al. (2000), Axelsson et al (2001) and

Björnsdóttir et al. (2004) suggest Icelandic horses may have a pre-disposition

for the disease, because of their poor conformation or joint architecture.

PathogenesisThere are two major factors leading to the development of degenerative joint

disease in the lower hock joints. The first is cartilage compression. The lower

tarsal bones have cartilage on their upper and lower surfaces, and they are

stacked on top of one another like building blocks (King and Mansmann,

1997). Excessive compression plays a key role by causing degeneration of

the structure of the cartilage and a consequent reduction of its shock

absorption properties. Over time the cartilage surfaces become flattened and

eroded, and the joint spaces narrow. Eventually the joint space may fill with

new bone (King and Mansmann, 1997).

The other major factor is uneven loading. When the lower hock joints are

unevenly loaded, there is excessive compression of the cartilage and

underlying bone on one side. On the other side there is strain on the joint

capsules and supporting ligaments. Repeated overloading of a joint surface

can cause remodelling and new bone production, exostoses or bone “spurs”

at the edges of the bone. Likewise, excessive and repeated strain on the

joint’s soft tissues can cause exostoses around the joint. These bony

changes, narrowing of the joint space, and bone spurs around the joint, are

the hallmark of bone spavin (King and Mansmann, 1997).

Clinical SignsThe researcher believes from personal experience in the field, that the initial

signs of bone spavin are detected by the farrier when trimming or shoeing,

with the horse exhibiting a stiffness and reluctance to lift and flex the leg back

into the required position.

Sporadic and vague hind limb lameness (Dick Vet 2012) accompanied by

stiffness and shortening of the cranial phase of the stride (Gough and Monroe

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1998) particularly when walking down hill, is also a feature. This is commonly

followed by increased wear to the lateral branch of the shoe (Stashak 2002,

Riegel and Hakola 1996) often with a squaring of the toe, because of the

dragging of the foot brought about from reduced flexion of the hock (Butler

1985).

Diagnosis aidsThe diagnostic process should commence with enquiries as to the horse’s

history. Factors, such as age, work load and reduction of performance, should

be considered, followed by an observation of static conformation, noting flaws

such as sickle hocks and base narrow stance, as these issues may increase

stresses through the distal hock joints (Jackman 2006). Physical palpation of

the medial distal aspect of the hock should identify abnormal enlargements as

well as other abnormalities (Gough and Monroe 1998).

The horse should then be observed dynamically at walk and trot in straight

lines and also when turning, to evaluate gait changes or abnormalities. Intra-

articular analgesia should be used to block out pain to assist identification of

the affected area (Gough and Monroe 1998, Jackman 2006). Although the

flexion test or spavin test is routinely used to assist in the diagnosis of hock

lameness (Butler 1985, King and Mansmann 1997), Gough and Monroe

(1998) believed that a mild response should be treated with scepticism.

Armentrout et al (2011) concluded that a flexion test result should not be

considered in isolation from other clinical data.

To achieve a complete radiographic examination of the hock a minimum of

four radiographic views are used; dorso-plantar, lateromedial, dorsolateral-

plantaromedial oblique and dorsomedial-plantarolateral (Eksell et al 1999,

Butler et al 2000, Baird 2002, Siems 2005, Jackman 2006, Byam-Cook and

Slinger 2009). Infrared thermographs can be utilised to reveal increased

thermal gradients on the medial aspect of the hock (Riegel and Hakola 1996).

Nuclear scintigraphy (Gough and Monroe 1998, Jackman 2006,) and

magnetic resonance imaging (Blaik et al 2000) have improved imaging detail,

allowing the identification of more subtle lesions. Both are increasingly used

diagnostic tools.

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TreatmentThere are a multitude of veterinary treatments for bone spavin, the choice of

which is dependent on a variety of factors such as the degree of lameness,

other coincidental pathologies, radiographic signs, horse’s work regime, time

constraints, response to other treatment, and cost (Gough and Monroe 1998).

Conservative or non-surgical treatment can be implemented in the form of

non-steroidal anti-inflammatory medication (NSAIDS) such as phenylbutazone

or flunixin meglumine which can be used in the short term (Jackman 2006),

along with a controlled exercise regime (Gough and Monroe 1998).

Commonly used intra-articular medications administered to the affected area

include corticosteroids that will reduce inflammation and hasten cartilage

degeneration (Riegel and Hakola 1996, Gough and Monroe 1998). Hyaluronic

acid and products such as Adequan® can reduce pain in mild cases but are

less effective in moderate to severe cases (King and Mansmann 1997).

Most surgical procedures are aimed at accelerating the process of joint fusion,

(ankylosis), and involve destroying some of the cartilage of the lower hock

joints with a surgical drill bit (King and Mansmann 1997). This process is most

effective when there is minimal radiographic evidence (Gough and Monroe

1998). Cutting of the cunean tendon can be a way of reducing pressure over

the medial aspect of the distal tarsus and cunean bursa (Jackman 2006).

The utilisation of farriery treatment is critical in the management of bone

spavin (Dick vet 2012). Shoes with a raised heel and rolled toe can facilitate

the horse’s action (Hickman 1985) by preventing hyperextension of the distal

intertarsal and/or tarsometatarsal joints (Back 2001). Peham et al (2006)

found that by raising the heels of the hind limb resulted in an increase in

maximum hock flexion during the stance phase of the stride, and claimed

evidence for the use of raised heel shoes for horses with pain at maximum

hock extension, e.g. bone spavin. Shoes that offer additional stability and heel

support, such as egg bar shoes, can also be beneficial (King and Mansmann

1997, Dick Vet 2012), although Gough and Monroe (1998) prefer the use of a

shoe with a lateral extension to help increase lateral support.

.

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Chapter 2 - Literature Review 2.1. IntroductionThe research methods utilised for this study included the Internet, both farriery

and veterinary textbooks, and veterinary journals such as Equine Veterinary

Journal and Equine Veterinary Education. Many of these were sourced

through the university library, or via the internet through search engines such

as Google Scholar, Wiley on-line and IVIS. Keywords searched included hock,

tarsus, hock angle, spavin, equine conformation and radiographic protocols.

2.2. Equine ConformationSince domestication of the horse around 5000 years ago (Dunlop and

Williams 1996) equine conformation has been an important indicator of

performance and soundness (Holmström 2001), although interpretation of this

is still largely based on subjective criteria and empirical evidence (Van

Weeren and Crevier-Denoix 2006). Despite the lack of scientific research and

its subjective nature, Holmström (2001) felt the work done is of no less

interest, with early work on the relationship between conformation and

performance described by Bourgelat (1750) and Magne (1866) corresponding

well with results from more recent research. Van Weeren and Crevier-Denoix

(2006) cited the ground-breaking work analysing equine conformation and

gaits with the use of photography by Etienne Marey (1882) and Eadweard

Muybridge (1899). They also referred to several later studies (Bantoiu 1922,

Stratul 1922, Nicolescu 1923, Radescu 1923) acknowledging that, although

morphometric differences were found, statistical analysis was not carried out,

which casts doubts on the validity and reliability of the studies. However Van

Weeren and Crevier-Denoix (2006) suggest that scientific thinking has

advanced and technical possibilities have increased, which should allow a

deeper insight into the largely empirical practice of conformation judgement,

leading to a greater understanding of performance and soundness.

Many later studies have objectively measured conformation in horses,

including (Magnusson 1985, Holmström et al 1990, Holmström and Philipsson

1993, Back et al 1996, Eksell et al 1998, Dolvik and Klemetsdal 1999,

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Anderson and McIlwraith 2004). However, due to methodological differences,

the information is not always comparable across studies, with Gnagey et al

(2006), in particular, questioning the reliability of the studies. In an effort to establish a recognised standard for conformation assessment,

Magnusson (1985) developed an objective method for measuring the equine

conformation. The study was carried out on standardbred trotters and

gathered absolute figures of certain body measurements, such as length,

width, circumference and joint angles. This was done by using white slips of

paper measuring 4cm², the centres of which were marked with a cross or an

hourglass shaped black field. These were fixed to the horse with a water-

soluble glue stick, to twenty-five predetermined anatomical landmarks located

through palpation. The points were situated as near to the end of bones as

possible in order to record bone length, yet as close as possible to the moving

centers of the actual joints, for recording angle measurements. The horses

were positioned in what was described as a box but was actually a calibrated

frame that helped bring the horse into a standard posture for analysis,

reducing the variation in stance. A thorough process of testing measurement

accuracy was followed; five repeated measurements were made on an

immovable skeleton to check for errors in measurements, whilst

measurements were taken on three live horses five times daily over a period

of three days. Photographs were also taken, and these images were projected

at one-third actual size onto a wooden screen to allow measurement-

recording equipment to be pressed against the image. Three different

statistical methods were used; simple means and standard error, standard

deviations, and coefficients of variance. These enabled the testing of reliability

of the results generated from the differing measuring techniques. The fact the

markers were placed at the centers of joint rotation suggests that the bone

length measurements recorded were not the actual lengths of the individual

bones but segmented lengths relative to areas of joint rotation, a problem that

could call into question the validity of the bone length measurements results.

The quantitative method of Magnusson (1985) was utilised in the work of

Holmström et al (1990) to study the conformation of 356 Swedish warmblood

horses: thirty three of which were elite dressage horses, twenty eight were

elite showjumpers, 100 were riding school horses and 195 were unselected

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four-year olds. Holmström et al (1990) acknowledged that there were

differences from Magnusson (1985), in that the horses were stood against a

wall or a fence to be placed in a standard position. This therefore brought in to

question the accuracy of Holmström et al (1990) results compared to those of

Magnusson’s (1985) because of the greater chance of stance variation of the

horse. Holmström et al (1990) used the lengths of the radius and metacarpus

as reference lengths when comparing photographs with live horses.

Mawdsley et al (1996) felt that, because there was much disagreement

among animal breeders concerning which conformation traits were suitable

for particular tasks, assessment techniques needed to be standardised.

Despite the fact there is no reference given, Mawdsley et al (1996) claimed

this was achieved in cattle with a linear assessment trait evaluation

programme introduced by the American Holstein Cattle Association in the late

seventies. Even though Mawdsley et al (1996) described it as a well

developed system in cattle, there was no established system for horses,

therefore their aim was to develop an objective linear assessment trait

evaluation system to allow quantitative description of the static conformation

of the horse. A total of twenty-seven traits were assembled diagrammatically,

covering the full anatomy of the horse, of which measurements were taken.

The system was tested initially for repeatability of measurements on four

horses. Twenty-one of the selected traits were satisfactory and six proved

unsatisfactory in terms of reproducibility. A population of 101, two and three

year old thoroughbreds and nineteen thoroughbred stallions were similarly

assessed. More than 65% of the traits exhibited large (CV>10%) phenotypic

variation within the sampled population. It was proposed that such a system of

static conformation assessment would provide useful quantitative selection

criteria in the description and breeding of horses. The outcome of the study

was not to attempt to define good or bad characteristics but to describe where

the individual being assessed lies between the biological extremes for a

particular conformation trait (Mawdsley et al 1996). However to the

researcher’s knowledge such a system has not been implemented

scientifically in horses, but the researcher has utilised this method in a

previous subjective analysis of hind limb conformation.

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2.3. Hock Angle.There is much written about hock angle and its effect on performance and

soundness, however the vast majority being anecdotal and subjective (Butler

1985, Hickman 1985, King and Mansmann 1997). Several authors

(Magnusson 1985, Holmström et al 1990, Gnagey et al 2006) have measured

hock angle, these studies have been carried out by observing the position of

external markers placed on the horse at various points for reference.

Magnusson (1985) was tried to develop an objective method for measuring

conformation, although the sample size was small. Five repeat measurements

were made on a single horse, with the hock angle recorded as 143.6°, and

when the same measurement was repeated five times on a projected slide

image the recorded hock angle was 144.4°. Using Magnusson’s (1985)

measurement method, Holmström et al (1990) managed to record a hock

angle range from 356 separate horses, as 145° to 169°. This was then broken

down between categories; 195 four year old horses ranged between 145°-

161°, 100 riding school horses ranged between 148°-169°, 33 elite dressage

horses ranged between 150°-165° and 28 elite showjumpers ranged between

156°-165°. Therefore comparing hock angles of elite dressage and jumping

horses with “normal” horses, Holmström (1990) concluded that the dressage

horse in general had larger hock angles or, more correctly, there were no

sickle hocked dressage horses. Gnagey et al (2006) carried out an

assessment of sixteen horses of various breeds and ages standing squarely

with the hind hooves directly below the hip joint, the results of which indicated

that hock angle range was slightly less than Holmström’s (1990), with the

smallest recorded angle being 152 to the largest at 168. This could be

explained by the differences in sample size, breed type or methological

differences in marker placement or, indeed, the forced stance of the horse.

Gnagey et al (2006) categorised hock angles as small <155.5, intermediate

155.5°- 165.5°, and large >165.5. The researchers make no reference to

sickle hocks or post legged in analysis of the results.

Even though Mawdsley et al (1996) categorised hock conformation, no angle

measurements are given. Instead the conformation trait was scored on a

scale from 1-7. Therefore when assessing lateral hock conformation, a score

of 1 denotes a large hock angle (i.e. post legged), and 7, a small hock angle

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(sickle hocked), with 4 being in the middle and assumed ideal (Mawdsley et al

1996).

Many authors (Magnusson 1985, Holmström et al 1990, Black 1992, Eksell et

al 1998, Marks 2000, Axelsson 2001, McIlwraith et al 2003, Anderson et al

2004) believe certain hock conformational traits are considered undesirable in

relation to specific types of athletic performance or long-term soundness. A

small angle of the hock joint (sickle hocks), or a large angle (post legged), has

been implicated in the aetiology of tarsal disease (Hickman 1985, Stashak

1987, Eksell et al 1998, Dolvik and Klemetsdal 1999; Marks 2000).

Radiographic signs of bone spavin and hind limb lameness are often

associated with a small hock angle (Hickman 1985, Black 1992; Axelsson et

al. 2001). Stashak (1987) also includes plantar ligament desmitis with this.

Horses with a large tarsal angle are considered as being predisposed to

proximal suspensory desmitis (Dyson 2000) and upward fixation of the patella

(Stashak 1987). Conformation of the hock may also affect the horse’s

performance in sports that require hind limb power generation, such as racing

(Marks 2000), dressage (Holmström et al 1995), showjumping (Holmström

2000) and working western stock horse events (Black 1992).

Magnusson (1985) found that small hock angles (sickle hocks), were related

to more synovial distensions in the stifle and hock joints as well as to a

greater incidence of curbs. This has also been reported by several other

authors (Smythe, 1963, Pritchard, 1965, Davidson, 1970, Beeman, 1973,

Adams, 1974). Rooney (1968) and Hickman (1985) had the opinion that sickle

hocked horses were predisposed to bone spavin. Icelandic Toelter horses

show a significant correlation between small hock angles and bone spavin

(Eskell et al 1998). All these findings confirm Schmidt’s (1928) opinion that a

horse with a small hock angle will be able to stop underneath itself but will not

be able to carry weight on the hind limbs due to decreased resistance and

strength in the hock (cited in Holmström, 2001).

2.4. Bone Spavin

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Bone Spavin is one of the most common forms of hind limb lameness, so

much so that Gough and Monroe (1998) anecdotally claimed that the

condition accounted for over one-third of the hind limb lameness cases seen

at the Royal (Dick) School of Veterinary Studies. This claim, however, is

supported by Eksell et al (1998) confirming that radiographic changes were

evident in 33% of horses studied. Ehrlich et al (1999) also found that 33% of

hind limb scintigraphs of racing standardbred horses had radiographic

changes associated with the small tarsal bones, and a similar figure of 30.3%

was found by Björnsdóttir et al (2000). Baxter (2011) made reference to a

study carried out by Winter et al (1996) claiming only 7.2% of 3566 horses

failed to demonstrate radiographic evidence of bone spavin. The study carried

out by Eksell et al (1998) set out to estimate the prevalence of radiographic

signs of bone spavin in the Icelandic horse in Sweden. It involved 379 horses

comprising 238 geldings, 125 mares and 16 stallions, with the age of the

sample group ranging from 0 to 19 years. Owners were interviewed to obtain

individuals history including, age, gender, origin, working intensity, number of

gaits, and age when saddle broken. The hock conformation was assessed by

eye from the side and classified as straight, normal or sickle. A single

standard dorsolateral-plantaromedial oblique view radiograph of each hock

was taken and then recorded after consensus from the examiners. To validate

the radiographic method, 193 hocks of 98 different Icelandic horses were

radiographed in four projections; lateromedial, dorsoplantar, dorsolateral-

plantaromedial oblique and plantarolateral-dorsomedial oblique. These are

considered by Lavin (1994), Eksell et al (1999), Butler et al (2000), Siems et

al (2005), Vanderperren et al (2009) to be the minimum required to accurately

evaluate the hock joint. The findings of Eksell et al (1998) were that the single

dorsolateral-plantaromedial projection revealed a sensitivity of 93% and a

specificity of 84% in detecting bone spavin, compared to reading all four

projections of the same limb together. Horses with sickle hocks were reported

as having a bone spavin prevalence of 42%, which was significantly higher

than those with straight hocks (20%) and normal hock conformation (19%)

(Eksell 1998).

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Björnsdóttir et al (2000) conducted a study to estimate the prevalence of bone

spavin in a 614 Icelandic riding horses in Iceland aged 6-12 years; this group

consisted of 24 stallions, 403 geldings and 187 mares. Three radiographic

projections were used; latero-5°-proximalmediodistal, dorso-35°-lateral-

plantaromedial oblique and plantaro-45°-lateral-dorsomedial oblique

projections of each tarsus, with the beam centred on the distal intertarsal joint.

These projections differ slightly from those recommended by Lavin (1994),

Eksell et al (1999), Butler et al (2000), Siems et al (2005), Vanderperren et al

(2009). However, Björnsdóttir et al (2000) felt that, based on the results of

Eksell et al (1999), three radiographic projections were sufficient, that the risk

of underestimating the number and extent of radiographic findings was minor,

and that fewer exposures saved time and money and improved radiation

safety. Signs of bone spavin in the distal tarsal joints were found in 30.3% of

the horses, the prevalence of which was strongly correlated with age,

increasing from 18.4% in horses aged 6 years to 54.2% in those aged 12

years. No account of individual conformation traits was given (Björnsdóttir et

al 2000).

Risk factors which were considered as causative of bone spavin were

evaluated by Axelsson et al (2001) in a study that analysed 420 Icelandic

horses aged between 6-12 years, and involved interviews with

owners/trainers, analysis of blood samples, conformation assessment, motion

evaluation and radiograph interpretation. The results showed that the

radiographic signs of bone spavin in the hock increased with age, in line with

Eksell et al’s (1998) study, and horses with a smaller hock angle showed

significantly higher evidence of these signs (Axelsson et al 2001).

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2.5. Radiography of the hock joint A minimum of four views are generally used when evaluating the hock joint

radiographically; lateromedial, dorsoplanter, dorsolateral-plantaromedial

oblique and plantarolateral-dorsomedial oblique (Lavin 1994, Eksell et al

1999, Butler et al 2000, Siems et al 2005, Vanderperren et al 2009).

When radiographing the hock, Lavin (1994) stated the horse should be

standing in a normal weight bearing position. Butler (2000) agreed but

referred to the weight being evenly borne on both hind limbs. Siems et al

(2005) specified that the weight should be evenly distributed on all four legs.

Additionally, Eksell (1999), Butler (2000) and Siems (2005) specified that the

metatarsal be positioned vertically or perpendicular to the ground. Butler

(2000) also recommended sedation to facilitate examination of a difficult

horse.

For lateromedial radiographs, which is what this study is concerned with

Douglas et al (1987), Lavin (1994), Seims (2005), Weaver and Barakzai

(2010) all agreed that the cassette be placed on or against the medial aspect

of the hock. However Butler (2000) refuted this by recommending that the

hind legs be spread apart sufficiently to allow the cassette to be positioned

without touching either limb.

A true lateromedial projection is achieved by directing the beam parallel to a

line joining the medial and lateral malleoli of the tibia (Douglas et al 1987), or

to a line tangential to the heel of the foot (Butler 2000), whereas Seims (2005)

advised that the beam should be positioned parallel to the floor and centred

on the proximal intertarsal joint. Because the proximal intertarsal, distal tarsal

and tarsometatarsal joints slope proximodistally from laterally to medially

(Butler 2000), an alternative lateromedial view involves the beam being

angled 10° proximodistally (Eksell et al 1999) and centred on the proximal

intertarsal joint space (Douglas et al 1987) or distal intertarsal joint (Butler

2000).

21

2.6. Taking Measurements from RadiographsA way of reducing some of the parameters of error as discussed in sections

2.2 and 2.3, is to measure angles on radiographs (Caron 1988). This study

looked at angular limb deformities in foals, referring to a geometric evaluation

involving drawing lines on a clear acetate sheet placed over a radiograph. The

lines bisect the long bones above and below the involved joint, and where the

two lines intersect is the “pivot point” of the deformity. Caron (1998) claimed

that this corresponded to the most important site of abnormal development.

The severity of the angular deviation can be quantified by measuring the

angle at the same point of intersection. The author advised that subsequent

studies must have the same limb position and projection, as inconsistency in

either will substantially change the calculated angle. The primary focus of the

paper was to review the then present understanding and treatment methods

of angular limb deformities in foals. It does not make any reference to sample

size or inclusion criteria, and does not generate any data on the subject.

However, it contained only eight references, which brings into question the

validity of this study.

This method of measuring angles directly from radiographs was seen by the

researcher, as a particularly useful option for this study as it removed some of

the variations and reduced elements of error generated by the use external

reference markers discussed by Magnusson (1985), Holmström et al (1990),

Holmström and Philipsson (1993), Back et al 1996, Eksell et al. (1998), Dolvik

and Klemetsdal (1999), Anderson and McIlwraith (2004) and Weller (2006).

22

Chapter 3 – Methodology3.1. IntroductionResearch methodology is defined in simple terms as being a system of

models, procedures and techniques, which are used to find the results of a

particular research problem (Panneerselvam 2004).

In this respect a research process would be commenced with a definition of

the particular problem, followed by an outline of the objectives of the research

and details of the research design. An explanation of the process of data

collection and data analysis would follow and would lead to the interpretation

of the results and the validation of those results (Panneerselvam 2004).

3.2. HypothesisThe hypothesis is generally considered to be the principal instrument in

research and its main function is to suggest new experiments and

observations. Essentially, it states what we are looking for and it is a

proposition that can be tested in order to determine its validity. It must be

clear and precise in its definition, state the relationship between variables,

should be specific, limited in scope and, insofar as is possible, be stated in

simple terms so that it can be understood by all concerned. It should be

consistent with most known facts, amenable to testing within a reasonable

time and must actually explain what it claims to explain (Kothari 2006).

The hypothesis to be tested in this study is that: “Horses with bone spavin

have a smaller hock angle than those with no diagnosis”.

3.3. Problem definition or aimsA research problem must be identified and defined without any ambiguity

(Panneerselvam 2004). A research question must be concise and

unambiguous, achievable in terms of time, and ethical, whereas a hypothesis

is formed as a statement, tentatively predicting the research findings that the

results support or disprove (Gray 2009). To qualify as research, the process

must have certain characteristics: it must, as far as possible, be controlled,

rigorous, systematic, valid and verifiable, empirical and critical (Kumar 2011a).

Research is sometimes labelled as either pure or applied. The former is that

which is performed for the single goal of gaining knowledge – gaining

23

knowledge for knowledge’s sake. Any practical useful outcomes are simply a

bonus. The alternative is applied research, which is performed to solve a

specific practical problem. Here the practically useful outcome is the goal and

any outcomes of theoretical significance are the bonus (Goddard and Melville

2007).

3.4. AimThe aim of this pilot study is: “To test the hypothesis by comparing the

measured lateral hock angle of horses diagnosed with bone spavin with those

showing no abnormal pathology of the hock joint”. This aim could therefore

be described as one involving pure research.

3.5. Objectives of the researchPanneerselvam (2004) suggested that research techniques could be

categorised into two paradigms or conceptual frameworks, quantitative and

qualitative. Newman and Benz (1998) took the view that the quantitative and

qualitative research strategies and their underlying presuppositions have been

the subject of much debate since the early 1980s as though one or the other

should eventually emerge as more important. They rejected the dichotomy

assumed by that debate and took the view that the two philosophies are

neither mutually exclusive, nor interchangeable. They presented them as

interactive places on a methodological continuum based on the philosophy of

science. A researcher would test a theory and, as results fed back to the

original hypothesis, both inductive and deductive processes would be

operational at different points in time: quantitative and qualitative methods

would be invoked at different points in time: and feedback loops would

facilitate maximising the strengths of both methodologies (Newman and Benz

1998). The quantitative objectives aim to optimise certain measure of

performances of the system of study, whilst the qualitative objectives aim to

test the significance of hypotheses of a study of importance (Panneerselvam

2004). In basic form this could be defined as the former using numbers as the

unit of analysis and is usually associated with researcher detachment,

24

whereas the latter uses words or visual images, quality and description, and is

associated with researcher involvement, although such a simplistic approach

has been subject of much debate (Denscombe 2010). Qualitative and

quantitative research strategies have their philosophical roots in the

naturalistic and positivistic philosophies respectively. Almost all qualitative

researchers, regardless of their theoretical differences, reflect some form of

individual phenomenological perspective. Most quantitative research

approaches, regardless of their theoretical differences, appear to confirm that

there is a common reality on which people can agree. The debate between

the two centres upon the differences in assumptions about what reality is and

whether or not it can be measured. The debate further rests on differences of

opinion about how we can best understand what we “know”, whether through

objective or subjective methods (Newman and Benz 1998). The strength of

quantitative research lies in its ability to produce large-scale data, which can

be tested for reliability and validity, and consequently can be generalised to a

number of settings, but it can only measure what is observable (Gabriel 2007)

citing (Parahoo 1997). The strength of qualitative research, on the other hand,

lies in its intimacy with the truth and its ability to explore depth of meaning.

However, by definition, it cannot be subject to statistical analysis; and could

be susceptible to researcher bias (Gabriel 2007) citing (Parahoo 1997).

3.6. ObjectiveThe objective of this pilot study is: “To develop a method of measuring lateral

hock angle to characterise lateral hock angle in diagnosed and non diagnosed

cases of bone spavin”.

3.7. Research designA research design is the overarching plan for the collection, measurement and

analysis of data. Ideally, a research design would describe the purpose of the

study and the type of questions being addressed, the techniques to be used

for collecting data, the selection of samples and the system employed to

analyse the data (Gray 2009). Essentially, it would constitute the blueprint for

the collection, measurement and analysis of data (Kothari 2006). Research

questions help to define an investigation, establish parameters for the

25

research and provide direction, pointing to the theories that are pertinent, the

literature that is relevant and the kinds of research methodologies required

(O’Leary 2004).

3.8. Materials and MethodsAll lateral hock radiographs required for this study were provided by an equine

veterinary hospital in the North West of England. The advantage of analysing

radiographs supplied from a single source greatly reduced possible elements

of error as all the radiographs were taken following a strict protocol, thus

reducing variables in the imaging process and the stance of the horse. Two

sets of radiographs of the lateromedial view of the hock from a random

sample of horses were marked up and the angle formed at the hock joint was

measured using On-Track Equine® analysis soft ware. One set of

radiographs was of a random sample of horses that had been clinically

assessed and positively diagnosed by the veterinary hospital as having bone

spavin. The second set of radiographs was of a random sample of horses that

had been clinically assessed by the participating veterinary hospital but no

positive indications of bone spavin had been recognised. The radiographs of

diagnosed cases were numbered consecutively in odd numbers, with the non-

diagnosed cases being numbered consecutively in even numbers to enable

easy identification. A method of marking radiographs as accurately as

possible was developed using On-Track Equine® software. This involved

calibrating each radiograph from a fixed reference point, which was the

diameter of the left/right marker and was calibrated as 15mm. Measurements

were taken across the width of the tibia at two separate points. A line was

then placed down the full length of the tibia using the mid centre of the width

measurements as the points of reference.

This same procedure was used to mark the third metatarsal. Where the lines

that centrally bisect each bone cross was the point at which the angle

measurement was taken (point of intersection). (Fig. 3.1.)

26

Fig. 3.1.Distances, A and A are equal,

B and B are equal,

C and C are equal,

And D and D are equal.

27

AA

BB

C C

D D

Point of intersection. Angle measured in Degrees

Calibration was set from the diameter of the L/R marker at 15mm

Centre of rotation of the Tibiotarsal Joint.

3.9. Reliability and ValidityBecause of the vulnerability of the actual measurement process to error,

quantitative researchers should carefully determine whether the measurement

procedures, which they plan to use, sufficiently avoid systematic and random

sources of error before they start the study. This involves assessing whether

their measurement procedures have acceptable levels of reliability and

validity.

Reliability, essentially, is concerned with the amount of random error in the

measurement. The more reliable the measurement, the less random error

there will be in it. Reliability is a matter of whether a particular technique,

applied repeatedly to the same object, would yield the same result each time

(Rubin and Babbie 2010).

There are two main types of reliability, inter-observer or inter-rater reliability

and re-test reliability. The former is basically the degree of agreement or

consistency between or among observers or raters, whilst the latter is a

method for assessing a measure’s consistency or reliability over time – the

same measure applied to the same individual on two separate occasions

(Rubin and Babbie 2010). As there was only a single researcher involved in

the marking up and measurement recording in this pilot study, inter-observer

error was eliminated. With regard to re-test reliability one radiograph was

marked up six separate times and the individual measurements recorded, the

lowest and highest value were taken and the difference computed as a

percentage of reliability.

Validity refers to the extent to which an empirical measure adequately reflects

the real meaning of the concept under consideration and can be defined in

two basic forms: firstly, internal consistency reliability, or the degree to which

scores among scale items, or scores among subsets of items, correlate with

each other. Secondly, content validity, which is the degree to which a

measure seems to cover the entire spectrum of meaning within a concept

(Rubin and Babbie 2010).

28

3.10 StandardisationA standardised measure is one that is constructed, administered, scored and

interpreted in a prescribed, precise, and consistent manner in order to reduce

external influences that compromise reliability (Waltz et al 2010). The

essential characteristics are outlined as being a fixed set of items or

operations designed to measure a clearly defined concept, attribute or

behaviour; explicit rules and procedures for administration and scoring;

provision of norms to assist in interpreting scores; and an ongoing

development process that involves a careful testing, analysis and revision in

order to assure high technical quality (Waltz et al 2010).

Collecting data and the subsequent analysis of that data must take into

account the need for standardisation and the problem of variables. A variable

is an image, perception or concept that is capable of measurement and is

therefore capable of taking on different values (Kumar 2011a). A study

involves different response variables. Each response variable may be affected

by several factors. To test the effect of these factors on a response variable, a

suitable experiment has to be designed such that the necessary data for

testing the significance of the effects of the factors on the response variable

are collected, and to ensure the inferences of the tests are highly reliable.

There are two main elements to designing the study. Firstly identification of

the responsible variables of the study and then for each response variable the

following steps must be undertaken; identification of the factors affecting the

response variable; deciding on the type of each factor, which may be fixed or

random; determining the number of levels, or treatments, of each factor;

forming a skeleton of the study; and finally, writing the model of the study and

defining its components (Panneerselvam 2004).

29

3.11. Sample size and inclusion criteriaA sample is a small proportion of a population selected for observation and

analysis. In practical terms there has to be a trade-off between the desirability

of a large sample and the feasibility of a small one. Samples should be

chosen in a systematically random way in order to ensure that chance or the

operation of probability can be utilised (Singh and Bajpai 2008). Ideally a

sample should be large enough to provide an adequate representation of the

population that the researcher wishes to generalise about, and yet small

enough to be selected economically in terms of subject availability, expense in

time and money and the complexity of data analysis. Clearly the larger the

sample the smaller the scale of the sample error but subject availability and

cost factors are legitimate considerations in determining appropriate sample

size (Singh and Bajpai 2008)

The selection of the subjects/cases in the experiment should be such that the

results are reliable and valid. The criteria for inclusion and exclusion must be

clearly specified at the start of the study and this will improve the validity of

the results. Some experiments may be restricted to a subgroup of the study

population for a variety of reasons. Inclusion criteria identify the target group

in a consistent and reliable manner (World Health Organisation 2001).

The sample size for this pilot study was limited by the number of radiographs

provided by the participating veterinary hospital, all radiographs provided were

separated into two groups, positive bone spavin diagnosis and negative/clear.

All radiographs provided were included in the study.

3.12. Data CollectionWhilst deciding about the method of data collection to be used, the researcher

should keep in mind two types of data, primary and secondary. Primary data

are those, which are collected afresh and for the first time, and thus happen to

be original in character. The secondary data are those that have already been

collected by someone else, and which have already passed through the

statistical process (Kothari 2006) Primary data is collected either through

experiments or through survey. A researcher conducting an experiment

observes some quantitative measurements, or data, with the help of which he

examines the truth of his hypothesis. In the case of a survey the data can be

30

collected in a number of ways including, observation, personal interviews,

telephonic interviews, mailed questionnaires, or schedules completed by a

trained operator and taken to the respondent (Kumar 2011b).

Data collected comprised the angle measurements that were computed as a

result of the examination of each individual radiograph; this was then entered

onto a spreadsheet using Microsoft excel 2010®. All the data collected was

primary data.

3.13. Data analysisOnce the data has been collected it has to be analysed. Categories have to

be established and applied to the raw data in order to be coded and tabulated

so that statistical inferences can be drawn (Kumar 2011b).

The purpose of analysing something is to gain a better understanding of it.

Through a detailed examination of the thing that is being studied the aim is

either to describe its constituent elements, to explain how it works, or to

interpret what it means (Denscombe 2010).

Denscombe (2010) detailed five main stages for the analysis of data,

beginning with data preparation, an initial exploration of the data, analysis of

the data, presentation and display of the data, and finally validation of the

data. (Rationalise the statistical analysis chosen and why)

3.14. Interpretation of resultsInterpretation refers to the task of drawing inferences from the collected facts

after an analytical and/or experimental study. It is a search for a broader

meaning of the research findings and has two major aspects, the effort to

establish continuity in research through linking the results of a given study

with those of another, and the establishment of some explanatory concepts.

Interpretation also extends beyond the data of the specific study to include the

results of other research, theory and hypothesis (Kothari 2006).

31

3.15. Validation of resultsValidation is essentially the process by which scientific theories become

accepted (Jonker and Pennink 2010).

The analysis of quantitative data should include efforts to ensure that, as far

as possible the data had been recorded accurately and precisely, that they

were appropriate for the purposes of the investigation, and that the

explanation derived from the analysis was correct (Denscombe 2010).

3.16. Ethical considerationsIn the United Kingdom animal experimentation is governed by legislation in

the form of the Animals (Scientific) Procedures Act (1986) and the European

Directive (2010), and all researchers must have regard to the provisions

contained therein. A Working Party of The Nuffield Council (2005) produced a

report on Bioethics which considered a number of moral issues related to the

use of animals in research, including the problem of assessing pain, distress

and suffering.

In general terms, a researcher is dependent upon those who are willing to

collaborate with him/her and guidelines must be drawn up to protect parties in

that collaboration. An experiment may subject a participant to stress or may

have unpleasant consequences, so it is essential that participants are clearly

briefed on the course of the experiment and what is required of them. A

researcher must consider carefully at the outset what are the interests of the

subjects and how those interests may be safeguarded. The main principles,

which must be observed, are firstly, that the subjects’ cooperation must be

sought and they must be treated with respect. Their identities must be

protected and any information collected must not embarrass or harm them.

When negotiating permission, clarity is the keyword and the researcher must

honour the agreement. Finally, the findings must be honestly presented and

discussed (Taylor et al 2006).

The researcher adhered to the Farriers Registration Council’s, “Farrier’s

Guide to Professional Conduct 2011” (Farriers Registration Council 2011) at

all times and followed data protection guidelines (Data Protection Act 1998),

to ensure no horses could be identified from this pilot study. No identifying

information has been shown in the study and all data has been treated with

32

confidentiality and stored in a password-protected computer. Any identifiable

information or data held by the researcher for the purpose of the study will be

deleted from computer hardware or destroyed by shredding in a sustainable

manner. In order for this pilot study to be undertaken an ethical proposal form

was presented to and approved by Myerscough college’s ethics committee.

33

Chapter 4. Results4.1. Validation of Measurement protocolPrior to measuring the radiographs a setsquare was photographed and

measured using the Ontrack Equine® software to test its measurement

accuracy (appendix 3). 100%??

To validate the accuracy of the measurement protocol one radiograph was

repeatedly marked and measured six separate times.

Descriptive analysis was carried out using Minitab 16 Variability test giving a

coefficient variance of 0.18

4.2 Data collectionThe primary data was collected from the radiographs provided by the

participating Veterinary hospital using the designed protocol and entered in to

Microsoft excel 2010® spread sheet (Appendix 4). The summary statistics

and hypotheses test results are displayed in table ?

34

4.3. Data analysisTwo independent data samples were collected for analysis: Hock angles from

a sample of 18 radiographs showing no positive diagnosis of bone spavin and

hock angles from a sample of 44 radiographs showing a positive diagnosis of

bone spavin.

To be validly applicable for comparison both samples of data must be

normally distributed, this was tested using Anderson Darling. Histograms

showing this were generated using Microsoft excel 2010® (Fig. 4.1).

35

Fig. 4.1

The hypothesis was tested between diagnosed and clear cases using a 2

sample t-test for equal variance and showed a mean hock angle for the

diagnosed cases of 151.82° and 156.3° for the clear cases.

This shows a mean hock angle of 4.48° lower for diagnosed cases than clear

cases, although there appears to be a trend for the mean differences of the

measurements; range including the standard deviation makes the difference

insignificant (Figs 4.2 & 4.3).

Tarsus Angle

clearTarsus Angle

Diagnosed

Mean 156.30 151.82Standard Error 1.24 0.67Median 155.90 152.25Mode #N/A 156.10Standard Deviation 5.27 4.41Sample Variance 27.74 19.49Kurtosis -0.53 -0.84Skewness 0.50 -0.07Range 16.90 16.60Minimum 149.00 143.60Maximum 165.90 160.20Count 18 44

  Tarsus Angle clear Tarsus Angle DiagnosedMean 156.3 151.8182Variance 27.73882 19.48989Observations 18 44Pooled Variance 21.82709Hypothesized Mean Difference 0Df 60t Stat 3.428649P(T<=t) one-tail 0.000551t Critical one-tail 1.670649P(T<=t) two-tail 0.001102t Critical two-tail 2.000298 

36

Applying Gnagey et al (2006) categorisation of hock angle to the results

shows that in the diagnosed group 75% fall into the small category, 25% fall

into the normal category and none fall into the large category. Yet in the clear

group 44.5% fall into the small category, 44.5% into the normal category and

11% fall into the large category.

4.4. Statistical analysisDescriptive statistic was entered into Microsoft excel 2010®, normality of

distribution was tested using Anderson Darling. The hypothesis was tested

between diagnosed and clear cases using a 2 sample t-test for equal variance

??????. Correlations were tested using Pearsons with 2° of freedom.

Histograms were generated using Microsoft excel 2010®.

Why is it evenly distributed? Parametric and non parametric?

37

The data generated in this study shows that horses that have been positively

diagnosed with bone spavin have a mean hock angle 4.48° less than that of

the clear sample group, suggesting that horses with a smaller hock angle are

more predisposed to bone spavin.

Chapter 5. Discussion The radiographs provided for analysis in this pilot study were taken as part of

the diagnostic process of horses with hind limb lameness; therefore the

primary purpose of the radiographs was to investigate abnormal pathology of

the hock joint. The researcher had no control or influence over the stance

position of the horse or the radiographic procedure thus increasing the

amount of potential variance between radiographs.

Of the literature reviewed in this study there are differences in the way the

horses were positioned prior to analysis, in a box with the metatarsal vertical

and the contralateral limb somewhat more forward, with the weight on the

hind limbs equally distributed (Magnusson 1985), with the horse in a similar

position against a wall or fence (Holmström et al 1990), with the horse

standing square on level ground (Mawdsley et al 1996), in a standardised

pose with the front and hind feet square, the forelimbs vertical and the hind

hooves vertically beneath a hip marker (Gnagey et al 2006). Because of the

variation in the literature regarding the ideal positioning of the horse for

assessment, the adapted pose referred to by each author may not be a true

reflection of the horse’s natural conformation, casting doubt on the accuracy

of the results generated. This will be of particular significance when assessing

hock angle, if the metatarsal has been positioned vertically or the hind hooves

have been positioned directly below a hip marker, the angle formed may not

be true reflection of actual conformation.

Therefore the method developed in this study to measure joint angles from

radiographs could be further improved if a reliable and repeatable method of

positioning the horse in its own relaxed natural true stance could be

formulated. The use of a calibration marker placed on the limb prior to

radiography would also increase the accuracy of the marking and

measurement process of the radiographs.

38

(Add a bit about different conformation traits being desirable for different

disciplines).

Correct stance appears to be difficult to quantify Questions (CAN’T ASK QUESTIONS NEED TO DO IT SOME OTHER WAY) need to be asked what exactly correct stance is and what is the correct way to assess and quantify equine conformation.With an awareness of hind limb stiffness in horses and an increasing

understanding of conformational traits of horses that are affected by bone

spavin farriers are ideally placed to instigate earlier veterinary investigation of

the horse which may lead to earlier treatment of the condition reducing the

speed and severity of osteo-degeneration of the hock allowing the horse a

longer working life

On analysis of the radiographs used for this study it became evident that there

was a variation in the distance between the centre of rotation of the tibiotarsal

joint and point of intersection (fig. ??).

Because the radiographs used in this study have no calibration marker on the

limb the distance measurements are not accurate thus preventing any reliable

data to be generated being used for analysis.

39

According to Caron (1988) when analysing angular limb deformities in foals,

where the two lines intersect corresponds to the location of the most important

site of abnormal development. The point of intersection in this study could be

seen as an area of load or pressure the point of which could perhaps be of

significance to the development of bone spavin and the joint of which it

affects.

Chapter 6- Conclusion and recommendations6.1 ConclusionAlthough there appears to be a trend for the mean differences of the angle

measurements between the two groups the range including the standard of

deviation makes the difference insignificant

40

Centre of rotation of the Tibiotarsal Joint

Point of Intersection

Fig. ??.

6.2 Recommendations for further study Further study to investigate hock conformation and its relationship with bone

spavin could be carried out utilising the measuring technique developed for

this pilot study, using radiographs specifically taken and calibrated for

analysis. Much stricter control of horse positioning and radiographic protocols

by the researcher would enhance accuracy of the data generated allowing

more factors to be investigated, particularly the centre of rotation to point of

intersection and its relationship with hock angle.

By taking both a lateromedial and a dorsoplantar radiograph systematically

and applying the same marking and measuring protocols to each it should be

possible to evaluate both lateral hock angle and how straight the hind limb is

through the hock joint, i.e. cow hocked conformation. Direct comparison of

both projections should enable the researcher to accurately locate the point of

intersection in three dimensions within the joint and investigate any relevance

of its distance from the centre of rotation of the tibiotarsal joint.

This could also be built on by following the procedures discussed above, to

study the effect of the farriery treatment option of fitting raised heeled shoes.

Two radiographs could be generated one with the foot level and a second with

a wedge tapering downwards from heel to toe placed under the foot, to see if

there is any difference in the position of the point of intersection caused by

raising the heels of the foot. This could be tried with different height wedges to

alter the number of degrees the heels are raised. The results of which could

have relevance to farriery treatment as to whether the raising of the heel

moves the area of load or pressure within the joint.

Manufacturers Addresses Adequan:One Luitpold Drive,

P.O.Box9001,

Shirley,

41

NY 11967

MicrosoftExcel2010: Microsoft Corporation,

One Microsoft Way,

Redmond,

WA 98052-6399,

USA

Ontrack Equine:POBox152,

Lake Elmo,

Minnesota,

55042

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51

Appendix 1

52

Large hock angle (Post Legged)

Small hock angle (Sickle Hocks)

Appendix 2

Horse 1 2 3 4 5 6

Age Yrs. 10 10 19 7 13 15

Sex Male Female Male Male Male Male

Breed Irish Thoroughbred

Coloured Pony

Irish Draught

X Thoroughbred

Irish Draught

XThoroughbred

Thoroughbred AppaloosaX

Thoroughbred

Size H.H. 16.1 13.1 16.3 17 15 14

Caudal

Conformation

Normal BaseNarrow

BaseNarrow

CowHocked

CowHocked

CowHocked

Lateral

Conformation

PostLegged

PostLegged

PostLegged

PostLegged

PostLegged

PostLegged

Work

Regime

EventingHuntingHacking

Hacking HuntingHacking

Dressage

EventingHacking

EventingHunting Hacking

EventingDressageHacking

X-Ray

Changes

Yes No Yes Yes Yes Yes

Vet

Treatment

JointInjection

NSAID JointInjection

JointInjection

JointInjection

JointInjection

Farrier Square ToeGraduation

LateralExtension

Rolled ToeGraduated

Normal Lateral Extension

Normal

53

Appendix 3

To test the accuracy of the measurement software a set square was

photographed using a Kodak ?? digital camera and downloaded to an Acer

Aspire 5315 laptop computer, this was marked and measured using the

Ontrack Equine® software.

Over the two fixed 90° measurements taken both recorded exactly 90°.

54

Appendix 4

Recorded Hock angles:

Tarsus Angle Tarsus Angledegrees degrees153.2 156.1153.5 154.3157.3 155.8157.7 155162.8 154.8163.6 144.3165.9 150.1165.5 152.8154 156.5

156.7 156.3149 151.8

149.2 150.7155.4 149.3156.8 143.6156 148.2

155.8 145.5151.2 154149.8 147.8

150.5158.4159.3151.4146.5145.9157.9152.8148.1148.7156.1153

153.2152.3147.7152

147.8144.2158.5152.3152.9149.3152.2156.6160.2145.3 55