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The Effect of Equine Hoof Growth

Monday, December 10, 2018  ‹ Back To Latest News List


Hoof Balance Theories

Welcome to the latest blog by our Brighton based Technician and Farrier Yogi Sharp on the effects of hoof growth and the Farrier's role.  This paper formed part of his studies.

Contents

  1. Introduction                                                             3
  2. Farriery interventions                                            3-4
  3. Van Heel et al 2004                                                 5-6
  4. Moleman et al 2006                                                 6-7
  5. Van Heel et al 2005                                                7-8
  6. Wilson et al 1998                                                    8-9
  7. Other studies                                                         9-10
  8. Conclusion                                                            10-11
  9. Word count                                                              11
  10. References                                                            12-13

Introduction

This paper will look at the effects of hoof growth in a stationary and moving equine and how a farrier’s intervention influences these changes. Probably the biggest effect of hoof growth over time is how it effects the balance and geometry of the hoof. We also need to assess the parameters of farriery interventions and look at whether these interventions will always have the same results.

 

Farriery interventions

Balance, as discussed in The American farrier’s journal (Turner 2017), is essential for the hoof and structures above it to work in harmony, imbalance predisposes the horse to injury. This article showed how “balance” can be assessed by different methods and can be somewhat subjective, therefore farriery interventions can be different according to each farrier. More study needs to be done to determine which farriery protocols are most beneficial.

A recent study (Caldwell et al 2015) adds weight to this statement and talks about how each hoof should be trimmed on an individual basis as the currently held universal protocols for trimming stemming from the studies of Duckett in the 1990’s didn’t hold true.

The question in the title is how farriery interventions will influence the parameters of the effects of hoof growth. As in Caldwell et al (2015) another study (Kummer et al 2007) showed that the farriery intervention’s influence over these effects, will not be universal. Kummer (2007) discussed how different farriers will influence the balance of the hoof very differently from each other depending on their methods. This shows that there must be more conclusive research done into trimming methods to create an industry standard that allows for repeatable and optimum farriery interventions.

For the sake of this assignment we will look at farriery interventions that looked to return the hoof pastern axis (HPA) to a straight one, and the proportions of the foot to be square to the long axis as this is the protocol used in the following papers stated in the contents. Hoof proportions determined by the culmination of M.N.Caldwells Geometric proportions (2010), which encompasses M.Savoldi’s Uniform sole thickness, D.Ducketts Dot, bridge and pillars (1990) and the NVQ level 3 trimming protocol are stated as the golden ratio and the optimum capsular proportions by Balchin (2017) and is perhaps what should have been used to standardise the trimming protocols for the research.

fig 3

Figure 3: Trajectory of CoP during stance phase of stride (after Van Heel et al 2004) and percentage timings (after Wilson 2001). Image courtesy of R.J.Mather

 Van Heel et al 2004

Van Heel et al (2004) discovered that horses had a preferred way of landing laterally both in front and behind and that the landing duration was shorter in the front limbs. The study showed that horses had a fixed unrollment pattern, the CoP followed a trace as in fig 3. The study showed a trimmed hoof did not change its preference but had less lateral deviation and a shorter landing duration. This showed a centralised loading of the hoof and therefore the internal structures post trim; even loading of the hoof allows the internal structures to be utilised correctly giving less rise to damage.

They discussed how post trim there wasn’t a substantial change in how the hoof landed but it did affect other aspects of the stride, most markedly how long a hoof took to land was reduced leading to the hoof having complete bearing support sooner, subsequently the CoP moved centrally quicker which in theory positively effects the load distribution on the internal structures. Conversely this study shows that hoof growth has a negative effect, the hoof takes longer to reach full bearing meaning the caudal aspect maintains loading for longer and at full bearing the load would be more medio-laterally imbalanced again negatively effecting the surrounding internal structures, Van Heel et al (2004) adds that full bearing support is beneficial in absorbing concussion. Because of the duration of landing in front feet and hind feet the effect of trimming which shortened the duration of landing 2.2 msec had a larger proportional effect on the front feet, this can be in part explained by the difference in the hoof/ground impact angle.

Van Heel et al (2004) also makes mention of the trim slowing the horses speed, possibly due to changes in muscle memory.

 

Moleman et al 2006

Moleman et al (2006) echoes the findings of Van Heel et al (2004) showing that in a shoeing interval of 8 weeks the hoof wall angle decreased significantly, this caused the CoP to move toward the joint away from the toe. This in turn increased the moment force significantly around the distal interphalangeal joint (DIPJ) however the moment around the proximal inter phalangeal (PIPJ) joint did not change significantly, this showed a compensation for the change in hoof conformation happened mainly in the DIPJ, the extension of this joint created an increased load on the deep digital flexor tendon (DDFT) and the navicular area, predisposing these soft tissue structures to injury. This showed that although the horse can compensate to an extent for hoof growth this compensation is detrimental even with minimal hoof growth and farriery intervention is important in protecting the internal structures of the hoof.

Moleman et al (2006) showed that there was no significant difference in the change of the CoP in a high angle foot (HHA) to a low angle foot (LHA), but the increase in moment was 2.4% larger in the LHA around the DIPJ, this indicated that horses with high low conformations should be shod according to the needs of the LHA. The ground reaction force (GRF) did not significantly change over the shoeing period, this indicates that the horse did not change its centre of gravity, however the distance between the GRF and the centre of rotation did change, indicating that the change in the lever arms was directly due to the change in the angles of the joints, even with a shorter shoeing interval the changes in hoof angle have a detrimental effect on the underlying structures.

Van Heel et al (2005)

Van Heel et al (2005) correlated with Moleman et al (2006) discussing how the movement of the CoP backwards in correlation to the growth of the hoof wall would put more load and strain on the navicular area. This study showed that hoof growth changed the conformation by increasing the dorsal wall length leading to a decrease in hoof angle.

This study again talked about the horses’ ability to adapt to hoof growth and therefore the CoP didn’t change position as much as predicted but the compensations weren’t enough to negate the negative predispositions, showing the necessity for farriery intervention. The study also showed that the front feet followed the same unrollment pattern, but the hinds shifted this pattern laterally. The CoP being different in the front and hind feet raised questions regarding the widely used ideas on hind foot and front foot balance.

Van Heel et al (2005) discussed how although there was a shift caudally of the CoP it wasn’t as large as previously calculated, possible explanations being; the rolling of the toe bringing the breakover point backwards and a possible change in DDFT tension or a change in limb placement. This again shows certain compensations to hoof growth by the horse, this was even more marked in the hind foot, where there was a larger lateral displacement of the point of rotation and a shortening of the toe lever arm. This goes some way to explaining why navicular and other loading related diseases are more common in the front feet.

 

Wilson et al (1998)

As well as the hoof wall length increasing and the hoof pastern angle decreasing, often the hoof will not grow parallel to the ground surface leading to medio-lateral imbalances. It is also in the authors experience that although most shod and unshod horses will show an increase in dorsal hoof wall length in between shoeing/trimming intervals, some horses, either by wear or perhaps growth irregularity (more study is needed) will grow heel length but not toe length, this can often be seen in laminitic horses. these growth patterns will also influence the static and dynamic hoof.

These effects are discussed in a study by Wilson et al (1998). The study showed that the point of force (PoF) moved in the direction of the high point of imbalance. Although in the study they artificially imbalanced the hoof with wedges it can show the effect of these imbalances on the hoof.

The study can be taken to show that if a horse grows more hoof wall laterally the PoF will move toward the lateral side and vice versa. The study also showed that the horse could adapt to a lateral imbalance more so than a medial imbalance by changing its stance. Wilson et al (1998) observed that with a heel wedge there was no change in the PoF dorsally and the heels stayed in contact with the ground for longer than they would of otherwise resulting in a slower forward movement of the point of force, resulting in the heels bearing more load for longer, This observation is significant in the farriery intervention of low week heels as a heel wedge is common practice in treatment of weak heels, however this study raises questions as to whether the wedge would actually perpetuate the issue.

 

Other Studies

The changes in loading will continue beyond the hoof into the digit and limb. uneven loading of the structures all the way up the limb will predispose the horse to injury Kilmartin (2014) discussed the effects of hoof imbalance on the structures higher up. In Medio-lateral imbalances he discussed how the hoof will distort and higher up, the muscles work harder. The effects can be quite complexed and extensive, even causing problems in the thoracic spine. This article showed that the effects of hoof growth go way beyond the biomechanics of the digit and effect the entire horse. Dorso-Palmer imbalances are discussed by a more recent study by Hagen et al (2015) that assessed the effects of modified shoes on phalangeal alignment, the angles were artificially created but the same president stands that if the hoof showed the same changes in angles you would have the same outcomes. The study discussed how when the angles of the bones are altered this has a loading or relieving effect of the internal structures. For instance, when the heel angle was raised there was a smaller angle in the DIPJ causing less loading on the DDFT. Conversely you could take that increasing the toe angle would increase the angle of the DIPJ and load on the DDFT. Many horses in the authors experience grow much more toe than heel and often in fact vice versa, hoof growth in these instances will change the biomechanics of the internal structures as stated above. Although in occasions where the heels grow more there would seem to be an immediate positive effect of decreasing load on the DDFT this will increase load on the suspensory apparatus, again showing the need to regain balance.

 

Conclusion

The studies we have looked at show that hoof growth has detrimental effects on the biomechanical workings of the hoof, both statically and dynamically. Although the horse has some compensation devices these are not sufficient to negate the negative predispositions (Moleman et al 2006, Van Heel 2005)

Hoof growth primarily effects the DIPJ and loading on the DDFT (Moleman et al 2006), but when the hoof growth is imbalanced medio-laterally or dorsa-palmer other structures also start to become effected (Wilson et al 1998). Medio-lateral imbalances cause one side of the hoof to bear more load and therefore the digit and limb above it, these are then predisposed to musculoskeletal injury. The imbalances caused by hoof growth can affect the entire equine musculoskeletal system (Kilmartin 2014). These studies clearly show that farriery interventions are important and should aim at returning balance.

However as discussed it cannot be assured that all farriery interventions will have the same effect, due to the individual farriers and equine conformations. Farriery interventions should be unique to the individual horse in terms of actual balancing of the hoof as well as the duration between interventions. For instance, if a horse grows hoof with a medial favoured medio-lateral imbalance they should perhaps be trimmed more often than one showing a lateral favouring as the horse can more easily compensate for the lateral imbalance (Wilson et al 1998). With some horses it should be considered that they can more easily compensate for hoof growth on their hinds than on their fronts.

 Although the studies talk about the farriers using a standardised protocol to trim for the experiments the studies by Caldwell (2015) and kummer (2007) show that at present a standardised protocol perhaps doesn’t currently exist and therefore the effects of farriery interventions depend on the individual farrier. It can be taken that for the most part a farrier’s intervention will rebalance the hoof and therefore go some way to preventing injuries predisposed to by the imbalances caused by hoof growth.

References

Duckett, D (1990) The assessment of Hoof Symmetry and Applied Practical Shoeing by Use of an External Reference Point. International: Farriery and Lameness Seminar. Newmarket England 2(suppl.) 1-11.

 

 Wilson, A, et at (1998) ‘The effect of foot imbalance on point of force application in the horse.’ Equine Veterinary journal, volume.30, No.6, pp. 540-545

 

 van HEEL, M, et al (2004) ‘Dynamic pressure measurements for the detailed study of hoof balance: the effect of trimming” Equine Veterinary Journal, volume 36, No.8, pp. 778-782

 

van HEEL, M, et al (2005) ‘Changes in location of centre of pressure and hoof-unrollment pattern in relation to an 8-week shoeing interval in the horse.’ Equine Veterinary journal, volume 37, No.6, pp. 536-540

 

 Moleman, M, et al (2006) ‘Hoof growth between two shoeing sessions leads to a substantial increase in the moment about the distal, but not the proximal, interphalangeal joint.’ Equine Veterinary journal, volume 38, No. 2, pp. 170-174

 

Kummer, M, et al (2007) ‘Comparison of the trimming procedure of six different farriers by quantitative evaluation of hoof radiographs’ The veterinary journal, volume 179, pp. 401-406

 

Caldwell, M.N., et al (2010) Quantitative Horse Hoof Trimming Protocol for Research Purposes. Forge Magazine, p4-10.

 

 

Mathers, J, 2011 ‘Summary of Biomechanics of the Equine Distal Limb’. (online) available from:

https://myerscough.instructure.com/courses/6874/files/103239?module_item_id=41429 (accessed 07/09/2017)

 

 

 

Kilmartin, R, 2014 ‘Equine Orthopaedic Balance: The Influence of foot balance on the biomechanics of the upper body’. (online), available from:

http://equineoptions.com.au/images/EOB-Rowan-Kilmartin.pdf (accessed 22/09/2017)

 

Hagen, J, et al (2015) ‘Modifying the height of horseshoes: Effects of wedge shoes, studs and Rocker shoes on the phalangeal alignment, pressure distribution and hoof ground contact during motion.’ Journal of equine veterinary science, volume 53, pp. 8-18

 

Caldwell, M, et al (2015) ‘A test of the universal applicability of a commonly used principle of hoof balance’ The veterinary journal, volume 207, pp. 169 -176

 

Turner, T, 2017 ‘The art and frustration of hoof balance’ (online) The American farriers journal, available from: 

https://www.americanfarriers.com/ext/resources/images/Marketing/Files/ArtFrustrationOfHoofBalance_web.pdf (accessed 07/09/2017)

 

Balchin, P, 2017 ‘The Golden Ratio in Relation to Hoof Capsular Geometry in Front Feet’ (online) available from:

http://www.scientifichorseshoeing.com/uploads/2/5/6/1/25618141/golden_ratio__capsular_geometrics_significance.doc (accessed 29/12/2017)