A Pilot Study of Dorsopalmar Geometric Proportions of the Equine Fore Foot

M. N. Caldwell. FWCF* & J. D. Reilly, BSc (Hons), BVSc, PhD, MRCVS.The School of Veterinary Nursing and Farriery Science, Myerscough College, Myerscough Hall, Bilsborrow, Preston, Lancashire, PR3 0RY*Tel: 01995 642000 ext; 2057 Mob: 07792374551 emails; markncaldwell@btinternet.com or mcaldwell@myerscouch.ac.uk

Word count does not include all figures and references.4258

Key words: Farriery, conformation, hoof trimming, foot balance, hoof capsule pathology, hoof capsule morphology, geometric, proportions.

Summary

Introduction: Russell (1897) argued that symmetry around the central axis was the perfect form for “levelling & balancing” the foot. Russell hypothesised that “the height of wall from coronary band to ground bearing border should be the same at any 2 opposite points”. To this day this remains the basis for standard farriery texts. More recently Duckett (1990) Ovnicek (2003) have advocated proportionality to anatomical reference points along the solar margin to verify optimum balance to the trimmed hoof.The aims of this study is to record a range of hoof metrics once a standardised trimming technique had been used and to test the dorsopalmar hoof proportions ascribed by Duckett (1990) and Ovnicek (1995).Methods: A series of post trim measurements from easily recognisable anatomical points of 26 cadaver feet were recorded from digital photographs using OnTrack™ Equine digital measurement software. The results were transferred to Microsoft Excel within windows 2007 and data analysis of basic descriptive statistics with a confidence (>P) of 0.05 and Pearson’s correlations from the raw measurement data were generated. Results: There were strong relationships between the proportional dimensions quoted by Duckett (1990). LATTL was 1.05 times DHW-COR ± 0.06 S.D. p>0.01. LATTL was 1.07 times COP ± 0.10 S.D. p>0.01 and DHW-COR was 0.98 times COP ± 0.06 S.D. p>0.01. The distance COP - COR was calculated as a percentage of BBT. The heel width (BBHM x 2) + BBHL was calculated as a percentage of BBT. There was a strong inverse relationship p>0.62 between a reduction in heel width and an increase in the COP - COR distance. Discussion: Moleman et al; (2006) has established that horses are able to compensate for changes in form the equivalent of 8 weeks growth (4.8mm). It may be that this variation constitutes a “band of tolerance” within which the foot can still function in relative equilibrium our data indicates variations in proportion of that order. Savoldi (2006) has suggested that hoof capsule morphology can be linked to foot pathology. Conclusion: If the hoof can operate effectively within the range of asymmetry indicated in our study and Savoldi has a credible argument we might be able to predict certain pathologies based on hoof capsule form. Further work is clearly needed to test this hypothesis.

INTRODUCTION

Poor “foot balance” has been cited as a major causative factor in equine foot and

lower limb pathology. (Eliashar et al 2004). Hoof wall distortions are also considered

undesirable in domestic horses, possibly reflecting underlying disease or suggesting

impending lameness and requiring correction (Balch et al; 1997).

Questions about what hoof capsule metrics constitute ideal have teased farriers and

hoof care professionals for generations. To add confusion, standard texts differ in the

interpretation of even the most basic of hoof metrics. For example, dorsal hoof wall

angle (DHWA) Hickman (1987) advocated a 45° DHWA, Stashak in Adams

Lameness (2002) stated the range of normal as between 45° and 50° whilst Butler

(1995; 2005) quoted between 50° and 55°. Few have ascribed multi dimensional

metrics, often referred to as medial-lateral balance, as an essential component of

either static or dynamic foot balance. Russell (1897) argued that symmetry around

the central axis was the perfect form for “levelling & balancing” the foot. Russell

further argued that “the height of wall from coronary band to ground bearing border

should be the same at any 2 opposite points” (Fig. 1) to this day this remains the

basis for standard farriery texts.

More recently opinion has edged towards advocating a higher DHWA and greater

heel toe height ratio questioning the viability of the frog pressure model (Lungwitz

1891). Conflicting data indicates that the common hoof angle is between of 53º to

60º (Ovnicek 1995.), mean average of 54° (Clayton 1998).

Recently studies based on descriptive anecdotal reports of small samples of free-

ranging horses in North America (Emery 1977; Jackson 1992; Ovnicek et al; 1995;

Ovnicek. 2003) of the feet of feral populations have been cited as the ideal model

for static and dynamic foot balance of the domesticated horse. The ‘self-trimming’

process is also said to maintain the both the heel toe height ratio and the DHW in a

parallel orientation with both the phalangeal axis and the heel. Citing a morphological

and radiographic study of 150 front feet (Craig et al; 2001) Ovnicek et al; (2003)

suggested that the palmar angle of the distal phalanx should be elevated between 3º

to 8º in a dorsal palmer orientation. Kummer et al (2006) supported Craig et al;

(2001) in this contention.

Duckett (1990) explored the relationship of the distal interphalangeal joint (DIP) to

the proportions of the hoof utilising a series of external land marks as reference

points from which hoof proportions could be assessed. Duckett also theorised that

the location of these external reference points of the hoof give an indication

regarding the location of specific internal anatomical and biomechanical land marks

around which the foot should be trimmed and or shod (Fig. 2). Duckett called these

reference points. The so called “Duckett’s Dot”, when viewed from the solar border,

is located 10mm palmar to the true apex of the trimmed frog is purported to be

adjacent to the theoretical centre of pressure (COP) (Clayton 2004). “Duckett’s

Bridge” is located palmar of “Duckett’s Dot” and is said to be representative of the

centre of rotation (COR) of the DIP. On the solar border of the hoof COR is said to

be represented at the widest part of the hoof. Other authors (Ovnicek et al; 2003)

have ascribed COR a fixed measurement of 1 ¼” palmar of the true apex of frog.

The application of fixed measurements fails to account for individual biomechanical

variation. Duckett (1990) then utilised his external reference points to quantify

proportionality of any given hoof segment along the bearing border against the linear

DHW measurement. Ovnicek (2003) merely quotet the frog as being 2/3rd of the

bearing border length. Neither author addressed the question of what mediolateral

proportions might be considered normal. Like Duckett (1990), Ovnicek (2003)

proportioned for anatomical reference points along the bearing border to verify

optimum balance to the trimmed hoof. Ovnicek proposed that the basal length

between the heel buttresses to the COP and from COP to the point of optimum

break over forms a 60:40 ratio. The frog is said to be 2/3 rd the overall length of the

bearing border and that the distance from the frog apex to the point of optimum

break over is 11/4”.

Duckett (1990) and Ovnicek et al; (1995) cited two other externally visible reference

points the Pillars. Both authors claim that these structures run the entire height of the

dorsal hoof wall biaxial of the distal extremity of the extensor process of the distal

phalanx. They suggested that the pillars are two of four points of weight bearing, the

remaining two being the heel buttresses. Hood et al; (1997) dismiss Ovnicek et al;

(1995) suggesting that these points are in fact primary weight bearing structures. In a

study of hoof deformation on different surfaces Hood, et al (1997) suggested that all

the epidermal structures are weight sharing and that the wear pattern seen on feral

horses is a reflection of wear and these four points are not in fact high points of

contact. The so called four point type of wear pattern was only visible on horses

pastured on uneven ground. Horses pastured on firm ground wore the dorsodistal

border of hoof wall to below the level of the sole, whilst those pastured on sand

exhibiting a more defined solar arch both similar to those witnessed by Jackson

(1992).

It has been said that the hoof wall is an elastomeric structure (Lungwitz. 1891;

Thomason 2002) which, if placed under constant stress will lose its elastic qualities

and thus its ability to absorb shock and more importantly retain its shape or

proportions. Increased stress loading of hoof wall structures is said to lead to

changes in both form and function of the foot (Reilly 2006). Turner (1992), Turner

and Stork (1998) and Stashak (2002) have attempted to define a number of hoof

abnormalities objectively and advocate a series of measurements to assess foot

balance and to quantify morphological changes to the hoof capsule as measured

against the standard text model of normal hoof conformation.

Savoldi (2006) linked hoof morphology to the orientation and function of the internal

structures. Savoldi utilised the uniformity of sole thickness to the horizontal plane of

the bearing border to analyse solar arch morphology. He believed that this indicates

P3 orientation which may lead to localised areas of pathology around the distal

margin of the distal phalanx and associated structures of the distal sesamoid.

There are several contrasting opinions on the effect that stress loading of the hoof by

faulty conformation might have on foot form and function. The conformation of the

hoof and the foot can change when a horse’s environment is changed including the

extent of movement, ground surfaces, trimming and shoeing procedures (Bowker.

2003; Hampson. 2010).

Bowker (2003) stated those feet with one side steeper than the opposite side, the

primary epidermal lamella (PEL) are not evenly distributed between the toe and the

heels but seem to be distributed in accordance with stresses being placed on the

foot. When attributing morphological changes within the hoof to stress created by the

environment, Bowker (2003) noted that there is a greater density of PEL along the

portion of the hoof wall that contains a flare when compared with the non-flared side

of the foot. In contrast Hampson (2010) noted PEL appear evenly spaced in the feet

of feral horses from the Australian desert. In contrasting experimental conditions

both authors note rapid adaptation of the hoof to the environmental conditions.

Dejardin et al; (1999) noted that viscoelastic deformation of the hoof wall produced

potentially harmful strain and that this strain distribution appears to result from the

differential expansion of the hoof wall under load. In their experiments increasing

load resulted in higher strains and asymmetric loading resulted in an ipsilateral

increase in strain magnitudes without altering strain locations. Dejardin et al (1999)

showed epicentres of high shear stress at locations two-thirds of the way down the

wall which corresponds to clinical observation of flares in distorted feet. Bowkers

(2003) observations of the PEL density being a response to biomechanical variation

would therefore seem to be logical.

Moleman et al; (2006) demonstrated that standing horses are able to compensate for

changes in dorsopalmar hoof conformation over an 8-week shoeing interval. Their

findings that the morphological changes within the hoof shape following 8 weeks of

normal unrestricted growth leads to increased DIPJ extension and an increased

loading of the deep digital flexor tendon. This would seem to support Bowkers (2003)

assertion that the internal structures adapt in form in accordance with increased

strain.

Eliashar et al; (2004) investigated the relationship between the degree of heel

collapse and foot conformation and the degree of compressive force exerted by the

deep digital flexor tendon on the distal sessamoid. Their findings that heel collapse

was not significantly correlated to any of the force parameters yet changes in force

parameters were directly correlated to the changes in the ratio of heel to toe heights

and the palmar angle would seem to support our hypothesis that hoof capsule

proportions are more significant to skeletal orientation and the subsequent

distribution of load than mere parallelism of the phalangeal axis with the toe and heel

(Mather. et al; 2009).

The suggestion is that structures of the foot are able to cope with a degree of

morphological change before having to adapt to biomechanical variation (Thomason.

2002; Bowker. 2003; Moleman. 2004; Eliashar. 2006; Mather. et al; 2009) and that

normal foot conformation could be considered as a range of common variable hoof

metrics.

AIM OF THE STUDY

The aim of this study is to record a range of geometric hoof proportions using a standardised trimming technique and to;

A. Test the hoof proportions ascribed by Duckett (1990) and Ovnicek (1993) post trimming following after a standardised trimming technique has been used.

B. Test the hypothesis that normal foot conformation constitutes a range of common hoof proportions as opposed to a rigid fixed model.

MATERIALS & METHODS

26 fore limbs from a mixed population of riding horses ranging in height from 15hh

through 16.3hh weighing between 375kg and 580kg were selected on the basis of

displaying minimal visual limb and hoof pathology or gross angular limb deviation

(Mawdsley et al; 1996). The limbs were disarticulated at the intercarpal joint to

maintain the proximal attachment of the suspensory ligament.

The common digital extensor tendon (CDET), lateral digital extensor (LDET), deep

digital flexor tendon (DDFT) and the superficial digital flexor tendon (SDFT) were cut

3-4” proximally to the distal extremity of the radial carpal joint to allow for the

attachment to a cadaver limb press for use in subsequent experiment.

All limbs were visually conformation scored (Mawdsley et al; 1996) from a dorsal

palmar view by two experienced farriery assessors. The coronary hairline was

shaved with standard horse clippers and all limbs were branded in alphabetical order

a-z at a point 20mm proximal of the coronary border through the central axis and

medial / laterally at the level of the middle of the phalanx, with a branded dot below

the letter on the medial aspect for photographic identification of left or right.

Trimming Protocol

Each foot was trimmed to a standardised trimming protocol for research purposes

(Caldwell et al, 2010) by two qualified registered farriers and checked for accuracy

by two experienced farriery assessors (Fig. 2).

Photographic Evidence

A series of digital photographs using a Fuji Finepix and Kodak c875 zoom cameras

were taken pre trim and post trim. To ensure consistency of photographic standards

the camera placed on a tripod 12” perpendicular to a custom built 12 x 12 x 12”

photographic box containing a fixed 12” calibrating marker perpendicular to the

camera (Fig. 3). Individual photographs were calibrated and a series of 10 pre

determined digitised measurements, accurate to 1 pixel, relating to specific

anatomical reference points were recorded from both pre trim and post trim using the

manual Ontrack™¹ digital measuring software program (Tables 1 & 2). All

measurements were recorded by two separate co-workers, qualified farriers, and five

foot images from each projection randomly checked by the lead researcher for

consistency.

All of the measurements were recorded in a Microsoft Excel (Windows 2007) spread

sheet (annex 1). Unlike the other measurements taken, the COR of DIPJ and COP

were not physical external structures but external reference points estimated by

Duckett (1990) relating to internal physiological structures. The COR was mapped

onto the solar surface of the foot by projecting two parallel lines from the centre of

each heel buttress at the widest part of the frog forward through to the toe at the

solar white line interface. Two diagonal lines were projected from the heel buttress to

the opposing toe. A horizontal line drawn through the intersection of the diagonal

lines was corresponded to the widest part of the ground bearing hoof and is said to

be representative of the COR (Caldwell. 2001). Unlike the COR the COP is not a

fixed anatomical point and will move or change during the landing, loading and break

over phases of the stride pattern due to the changing position of the horses centre of

mass (Clayton.2004). According to Clayton (2004) COP is located dorsopalmar in a

sagittal plane directly below the attachment of the superficial extensor tendon and

the insertion of the deep digital flexor tendon. COP was marked up according to

Duckett (1990), 10 mm palmar to the apex of the trimmed frog as a repeatable

constant external reference.

Using mediolateral X and dorsopalmar Y coordinates to plot outline images for the

shape of the bearing border of all the post trimmed feet, for a separate study, using a

smoothed line scatter graph within the Excel™ chart wizard tool. Five experienced

qualified farriers visually placed the images into four groups of common foot shape

based on individual clinical experience.

DATA ANALYSIS

Descriptive statistics for range, median, standard deviation, standard error,

frequency distribution with a confidence (>P) of 0.05 and Pearson’s correlations

(table 1) from the raw measurement data were generated (annex 2) for pre and post

trimming using Microsoft Excel™ spread sheet (Windows Vista Office 2007). The

data was transferred to Mini tab 15® for comparative analysis of common foot

conformation parameters of heel toe height ration, heel toe parallelism and the key

proportional reference points of Duckett (1990) including dorsal hoof wall length

(LATTL), bearing border COP to heel termination (BBCOP) and bearing border COR

to the dorsodistal extremity of the DHW (DDT-COR). Variable Analysis, Anderson-

Darling normality test were performed with a probability of 95% for the whole sample

by action and each of the four groups by foot shape.

Proportional and standard hoof metric data analysis was performed in the Microsoft

Excel™ spread sheet (Windows Vista Office 2007®). Heel toe ratio was calculated

by dividing heel height (HH) by LATTL. Duckett’s (1990) proportions were calculated

in the dorsopalmar sagittal plane by dividing both BBCOP and DDT-COR by LATTL.

Mediolateral symmetry was assessed by comparison of “X” axis bearing border

coordinates of the dorsodistal reference points zeroed through the longitudinal axis

of the frog. Bearing border coronary band parallelism and medial and lateral wall

height and angle were assessed in the frontal section dorsopalmar plane. Medial

lateral and proximodistal foot conformation results are the subject of a separate

study and are not presented here.

RESULTS

Full descriptive sagittal, dorsopalmar along the bearing border hoof conformation

data is attached to annex 2. Table 1 displays the descriptive statistics for range,

standard deviation, normal distribution and Pearson’s correlation’s from raw data of

the sagittal measurements from a lateral aspect.

Post trim heel height ranged between 16.1mm and 27mm mean 21.6mm.± 7.3º S.D.

Vertical toe height ranged between 53.6mm and 70.6mm mean 61.01 ± S.D. 1.7mm

S.D. There was a direct correlation between the toe height and the heel height P>

0.5. Heel height ranged between 28% and 45% of the vertical toe height with a mean

of 35% S.D. ± 5% p>0.45 (table 1).

Post trim lateral toe angle ranged between 47º and 59º mean 52.84º ± 2.8 S.D. of p>

1.13 where as the lateral heel angle ranged between 27.5º and 58º mean 39.5º.± 7.3º

S.D. The mean difference between toe angle and heel angle was 14.3 º S.D. ± 6º.

(Table1). There was a direct relationship between LATTA and LATHA p>0.54. The

data also suggests an inverse relationship between LATTL and LATHA P> -0.48 R²

= 0.2.

Basal length (BBT) ranged between 99mm and 133mm mean 117mm± 9.5mm S.D.

Heel termination to the calculated widest point of the bearing border, COR, ranged

between 37mm and 59mm mean 48mm ± 5mm S. COR exhibited a direct correlation

with BBT p>0.95 (table 2) and was on average 41% of BBT. Heel termination to

COP ranged between 55mm and 83mm mean 68mm± 8mm S.D. and exhibited a

strong correlation with both BBT P>0.89, and was on average 58% of BBT and COR

P>0.83. Heel termination to the apex of the trimmed frog (FRA) ranged between

65mm through 94mm and a Mean of 65mm± 7.5mm S.D. and was a mean 67% of

BBT and exhibited a direct correlation with BBT p>0.9.Heel termination to the white

line solar interface classified as the biomechanical point of break over (BO) (Mather

et al; 2010), ranged between 81mm and 115.5mm mean 99mm.± 9.8mm S.D p>0.97

and was on average 84% ± 2%. S.D. of BBT. BO exhibited strong correlations with

both BBCOP and BBCOR p>0.84 and p>0.92 respectively (Fig. 4).

There were strong relationships (table 3) between the proportional dimensions

quoted by Duckett (1990). LATTL was 1.05 times DHW-COR ± 0.06 S.D. p>0.01.

LATTL was 1.07 times COP ± 0.10 S.D. p>0.01 and DHW-COR was 0.98 times COP

± 0.06 S.D. p>0.01.

The distance COP - COR was calculated as a percentage of BBT. The heel width

(BBHM x 2) + BBHL was calculated as a percentage of BBT. There was a strong

inverse relationship p>0.62 between a reduction in heel width and an increase in the

COP - COR distance.

As previously stated feet were grouped by visual assessment of bearing border

outline plots of x and y coordinates from the longitudinal axis of the frog. Table 4

below shows the variable action normal distribution plots in for Duckett’s proportional

references both pre and post trim including mean averages, standard deviations and

population figures for each group (pre trim data annex 2).

DISCUSSION

Both Turner (1998) and Stashak (2002) have described ideal toe heel conformation

as parallel to the phalangeal axis and within the range of 50º to 55º. Under run heels

are defined (Stashak 2002) as 5º or greater differential from toe angle. All feet in our

study presented with under run heels (Stashak 2002) with the differences between

toe and heel angle of 9° to 24° mean 14.3º±6.º S.D. or up to 31%. Our results are in

line with those of Powell (2006) who found a mean heel toe angle variation of 13º

There was a moderate inverse relationship between toe angle and heel angle p>0.38

and a strong inverse relationship between toe angle and toe length p>0.69 This goes

some way to confirm that increasing toe length reduces toe angle, as it shifts the

COM caudal increasing stress to the palmar aspects of the hoof. The increasing

stress leads to deformation of the dermal horn structure.

Given the widely recognised morphological link between long toes and week under

slung heels (Turner 1988) and the strong inverse relationship p>0.62 between a

reduction in heel width and an increase in the COP - COR distance this may partially

explain the variations in outline border shape and suggests a conformational link

which needs further investigation.

Stashak (2002) and Butler (2005) quoted ideal toe to heel height ratios as 3: 1. Mean

toe heel ration was 2.9: 1. There was a direct correlation between vertical toe height

& heel height p>0.54. The indication is that vertical heel height is maintained even as

the heels run under. It is believed that heel toe height ratio plays an important role in

the maintenance of phalangeal orientation within the hoof (Craig 2005). Duckett

(1990) suggested that linear toe length also has a geometric relationship with the “Y”

axis of the bearing border and that this is a key factor in hoof phalangeal orientation.

Both Duckett (1990) and Ovnicek (2003) have ascribed proportionality of bearing

border reference points as an indicator of appropriate foot balance. The data from

our study suggests a strong proportional link between the “Y” axis references

p>0.92. Ovnicek (2003) used both heel to COP and FRA to assess dorsal palmar

proportions of foot balance citing 60:40 COP of BBT as the ideal adding that the

length of the trimmed frog to its true apex. Is 66% of BBT. The data from our study

confirms the length of frog from its widest point to the apex is mean 67% S.D. ±

0.029 p> 0.09. of the bearing border length n=73%. Chapman and Platt (1984) first

described the position of the insertion of the DDFT as a critical factor in the treatment

of laminitis and founder 33% of the basal length of the distal phalanx as visible on a

lateral radiograph. They go on to quote a point 3/8” palmar of the trimmed frog apex

as an external reference to it. Eustace (1989) stated that in the treatment of

“founder” heart bar shoes should not be fitted without reference to radiographs for

biomechanical reasons. The data from our sample also suggests Ovnicek (1995)

was correct to note that as a fixed proportion of the basal border length the frog apex

is clearly a significant external indicator of internal anatomical orientation and might

be used in first aid situations such as the treatment of laminitis (Eustace &

Caldwell1989).

Duckett (1990) theorised that toe length could be used as a measurement guide for

bearing border proportions to points of anatomical or biomechanical significance

which he named Duckett’s Bridge (COR) and Duckett’s Dot (COP). He advocated

that toe length is equal to the distance from the distal dorsal tip of the DHW to COR

and that the distance from COP to heel terminations are equal. Our study confirms

the accuracy of Duckett’s theory of proportionality to within a margin of error of ± 6%.

Our data shows a mean ratio of LATTL to DDT-COR was 1.06± 6% S.D. p>0.92 (n =

9). Mean ratio of LATTL to BBH - COP was 0.98±7% S.D. p>0.84 (n = 9).

Significantly in both orange and purple groups, some (80%) of our sample, all the

bearing border external references used to collect data exhibited consistent

proportionality. Only red group (8%) and grey group (12%) exhibited variations of

proportions along the bearing border or in relationship to DHW trimmed length.

Whilst we would accept that the sample size of both red and grey groups is

insufficient to draw firm conclusions, the indication is that the proportions found

within orange and purple groups could be considered as common in a mixed

population of domesticated horses. If the affects of weight distribution through the

foot are mitigated by its conformation as suggested by others (Thomason. 2002;

Bowker. 2003; Eliashar. 2004; van Heel et al. 2005), then the restoration of these

proportions may well prove significant outcomes in any remedial hoof care

interventions. The hoof is a three-dimensional dermal structure whose form can be

influenced by force over time (Moleman et al; 2006).

The data from our limited sample clearly suggests that first Russell (1897) and then

Duckett (1990) were right to ascribe common proportionality to those feet with

aesthetically good conformation. The two differences between the two researchers

(Fig. 1), some 100 years apart, would appear to be the accepted common DHW

angle of the time. Russell (1897) assumed a common front foot DHW angle of

between 45º and 50º whilst Duckett (1990) worked from the assumption of the front

foot DHW angle being between 50º and 55º. Secondly Russell (1897) did not ascribe

to the link between DHW length and bearing border proportions. Our study shows

there is a strong inverse relationship between DHW angle and DHW length p>0.69

which goes some way to confirming that increasing DHW length reduces DHW angle

and increases bearing border length. This may account for the discrepancies within

the between the work of Russell (1897) and Duckett (1990).

Conclusion and Clinical Relevance

Symmetry of the hoof around the central axis as the perfect form for “levelling &

balancing” the foot with the height of wall from coronary band to ground bearing

border equal at any 2 opposite points may constitute an aesthetically ideal

proportions. However our data suggests that variations of proportion mean 4% in

both height and angle in the dorsopalmar direction are common. Moleman et al;

(2006) established that horses are able to compensate for changes in from the

equivalent of 8 weeks growth (4.8mm). It may be that this variation constitutes a

“band of tolerance” within which the foot can still function in relative equilibrium our

data indicates variations in proportion of that order. Savoldi (2006) has suggested

that hoof capsule morphology can be linked to foot pathology. If the hoof can

operate effectively within the range of asymmetry indicated in our study and Savoldi

has a credible argument we might be able to predict certain pathologies based on

hoof capsule form. Further work is clearly needed to test this hypothesis.

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Mather. J, Caldwell M. N., and Reilly. J.D. 2009, A preliminary study of a geometric proportioned foot trim on the bearing surface of the equine front foot, By, Forge, April 2009, pp 4-8

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Moleman, M., van Heel, M. C., van Weeren, P. R., & Back, W. (2006), Hoof growth between two shoeing sessions leads to a substantial increase of the moment about the distal, but not the proximal, interphalangeal joint, Equine Vet.J., vol. 38, no. 2, pp. 170-174.

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Illustrations

Fig 1 According to Russell (1897) the foot should be properly prepared for shoeing by levelling and balancing the hoof so as it is equal height at any two corresponding points around the coronary band top right. Bottom right the similarity between Russell’s 1897 and Duckett’s theory of proportions 1990.

Fig. 2 after Caldwell et al (2010) foot mapping protocol (left). With frog trimmed and sole and white line exfoliated in preparation for trim. The bearing border trimmed to a horizontal solar plain (right). The excess wall at the bearing border is removed to a horizontal plane with the live sole; this helps determine the vertical height of the dorsal hoof wall (Duckett. 1990).

Fig. 3 Custom built 12 x 12 x 12” photographic box containing a fixed 12” calibrating marker perpendicular to the camera.

0 5 10 15 20 25 300

20

40

60

80

100

120

140

160

f(x) = 0.769291304347826 x + 107.601775362319R² = 0.328303865353393f(x) = 0.763334782608696 x + 100.579565217391R² = 0.29843011569986f(x) = 0.7827 x + 88.7825R² = 0.317646767134077

f(x) = 0.533556521739131 x + 72.0088768115942R² = 0.254997974233723f(x) = 0.543017391304348 x + 61.318115942029R² = 0.24459375093275

f(x) = 0.448286956521739 x + 42.3072463768116R² = 0.367299066686835

Proportional Relationship of Anatomical Ref Points Y Axis

BB CORLinear (BB COR)BB COPLinear (BB COP)BB FRALinear (BB FRA)

Fig. 4 a smoothed line graph shows P values and regression calculations which demonstrate a strong proportional relationship of bearing border reference points. COR 41% of BBT S.D. ± 2%, BBCOP 58% of BBT S.D. ± 3% BBFRA 67% of BBT S.D. 3% and BBBO at 84% of BBT S.D. 2%..

Fig. 5 the key measurements taken from the lateral include DHW length, height and angle and from along the bearing border length, width at the widest point, heel to centre of rotation, heel to centre of pressure (Duckett’s dot), heel to frog apex, heel to mechanical break over and dorsodistal extremity of the DHW to widest point of the foot.

Note: diagonal lines from the heel termination point intersecting parallel vertical lines extending to the medial and lateral points of break over intersect at the widest point of the foot.

LAT LAT TL DP CBT

LAT TA

LAT HA

LAT HH

TA / HA%

DIF CBT / HH%

TL / HH%

MAX 83.07 70.58 58.80 58.10 27.02 0.99 25.00 0.45 0.37MIN 58.89 53.61 46.80 27.50 16.10 0.52 0.70 0.28 0.23

MEAN 73.14 61.08 52.84 38.50 21.64 0.73 14.34 0.35 0.30STDEV 6.33 4.29 2.83 7.32 3.19 0.12 6.27 0.05 0.04CONF 2.53 1.72 1.13 2.93 1.27 0.05 2.51 0.02 0.02NDIST 0.73 0.78 0.80 0.97 0.50 0.92 0.08 0.34 0.40

CORRELL 0.68   0.45 0.54 0.51 0.88LATTL   0.68 -0.69 -0.38 0.45        DPCBT 0.68   -0.18 0.54 0.51        LAT TA -0.69 -0.18   0.54 -0.09        LAT HA -0.38 -0.24 0.54   0.00        LATHH 0.45 0.51 -0.09 0.002          

1.1 Legend to table 11.2 LATL 1.3 Linear toe length1.4 DPCBT 1.5 Vertical toe height 1.6 LATA 1.7 Dorsal hoof wall

angle1.8 LATHA 1.9 Heel angle1.10 LATHH 1.11 Heel height

Table 1 Key lateral plane post trim hoof conformation data for heel toe height ratio and heel toe height ratio and heel toe angle parallelism.

  COR COP FRA BO WL BB TMax 58.54 83.00 93.73 115.49 126.72 133.40Min 36.67 54.51 64.71 81.18 91.38 99.37Mean 47.91 68.11 78.68 98.57 110.12 117.22Stdev 5.23 7.76 7.47 9.82 9.88 9.49Conf 0.72 1.07 1.03 1.35 1.36 1.31Ndist 0.82 0.75 0.73 0.91 0.83 0.82Freq 10 12 12 13 13 13Pears 0.83 0.85 0.97

Legend to table 2

COR Centre of Rotation of DIPJ represented by the widest point of the basal border

COP Centre Of Pressure (9.5mm Palmer Frog Apex)

FRA Heel termination - Frog Apex

BO Intersection of the solar white line interface at the toe perpendicular to heel termination

WL Inner margin of the white at the toe along the central axis of the hoof

BBT Bearing border length heel termination – toe

Table 2 displays the descriptive statistics for range, standard deviation, normal distribution and correlation’s from raw data (annex 2) of the key bearing border reference points.

Legend to table 3LATTL Sagittal length Coronary hair line – dorsodistal extremity DDT-COR Dorsodistal hoof wall – Centre of Rotation (widest point of foot)COP Heel termination - Centre Of Pressure (9.5mm Palmer Frog Apex)FRA Heel termination - Frog ApexBBT Bearing border length heel termination - toe

LATTL COPDDT-COR LATTL/COP

LATTL/DDT-COR

COP/DDT-COR

FRA/BBT

AVERAGE 73.14 68.11 69.31 1.08 1.06 0.98 0.67MIN 58.89 54.51 59.39 0.94 0.92 0.85 0.63MAX 83.07 83 77.11 1.41 1.19 1.11 0.72

MEDIAN 74.85 68.14 68.88 1.07 1.05 0.98 0.67STDEV 6.19 7.60 4.74 0.10 0.06 0.06 0.03

AVEDEV 8.13 8.48 6.67 0.11 0.10 0.09 0.05NORMDIST 0.39 0.50 0.54 0.55 0.54 0.49 0.56

P CONF 0.85 1.05 0.65 0.01 0.01 0.01 0.004FREQ 12 12 12 12 12 12 12

Table 3 displays the descriptive statistics for range, standard deviation, normal distribution and correlation’s of the key bearing border reference points quoted by Duckett (1990) and Ovnicek (1995). Ratios between the centre of pressure and heel termination (COP) and the centre of rotation to the dorsodistal extremity of the DHW (DDT-COR) with the linear length of the DHW are also displayed. The length of the frog from the apex to the widest point palmar of heel termination is displayed as a proportion of the overall bearing border length through the longitudinal axis of the frog (FRA / BBT). COP calculated 10mm palmar the trimmed apex of the frog (Clayton 2004) and COR identified as the intersection of diagonal lines from heel termination to white line solar interface at the toe quarter (Fig. 5).

Table 4 Variable action histograms for the normal distribution LATTL, BBCOP DDT-COR. Basic descriptive data for the mean average dimension of each variable is included by group. Grouped by outline shape orange and purple groups are the most densely populated (80%) and would clinically be considered to have normal foot conformation (Turner 1992).