What About The Hinds? - Shoeing the Powerhouse
Updated: Sep 25, 2019
Farriery care can often be guilty of being fore limb focused, most of the research on horses’ feet has been fore limb dominant, there are set parameters for the ideal fore hoof conformation but not hinds and the majority of diagrammatical writing uses the fore hoof for illustration purposes. The rationale for this is usually put down to the fact that the fore limbs carry 60% of the horses weight, other factors may be that lameness is more easily recognised in the fore limbs with studies showing that the observer agreement on lameness even from experienced vets vastly reduces when assessing hind limbs. I have certainly been guilty in the past of sayings such as “lets sort out the fronts, the hinds will sort themselves.” And seeing hind feet like these (Fig1) while the owner insists it only needs fronts on!
Fig 1. bare foot hind showing imbalances and possible indications of higher pathologies.
Meanwhile the equine performance world is experiencing more and more hind limb and spinal pathologies, Sacro-Illiac disorders, kissing spines and proximal suspensory desmopathy/desmitis being prevalent, so should we be paying much more attention to how we are shoeing (or not) the hinds!? We must remember that the hinds have a different job to do and therefore work differently, for instance the hind limbs are “picked up” my muscular effort compared to the fronts which breakover, the hinds need toe to drive off as they are the power house, responsible for providing propulsion and even being responsible in some cases for compensating for fore limb disorders (see my article on high-low hoof conformation) and are therefore vitally important in longevity of working careers and maybe have even more effect on the musculoskeletal system than the fronts when considering their direct bony attachment to the axial skeleton compared to the muscular attachment of the fore limbs.
Dr Stephen O’Grady presented on applying farriery principles to hind feet (https://www.facebook.com/farriers/videos/1467883573375546/) where he spoke about the prevalence of low heel “bull nosed” hinds, but what was interesting to the author was the radiographs used to represent good hind hoof conformation (Fig 2).
Fig2. Expressing O’Grady (2019), an ideal front radiograph showing a straight phalangeal alignment and the “common” conformation in hind radiographs showing a distally plantarly displaced middle phalanx. Note that the angle of the distal phalanx is not dissimilar. Radiographs courtesy of Progressive Equine.
O’Grady found that in the majority of hind radiographs the middle phalanx presented as mildly displaced distally and plantarly, although this is not a peer-reviewed study it perhaps points at the ideal hind conformation being different from the fore, many farriers not armed with this information may be forgiven for thinking these hinds presented as having a broken back phalangeal alignment as it would be described as that would it of been a fore foot, however you can see that the angle of the distal phalanx is not dissimilar to the fore (Fig.2). ). Having said that common must not be confused with ideal and farriers should be careful to change practice on this evidence. O’Grady did highlight however that a negative plantar angle (NPA) was abnormal and needed to be addressed. Dyson (2007) and Mannsman et al (2010) amongst other studies have linked the “prevalent” low heel hind with higher pathologies and then expressed the remedial effect farriery can have, Mannsman et al (2010) linked it with gluteal pain and highlighted the stance adopted by the horses with the conformation which can be seen in both of the case studies further on in this article. Mannsman described these hooves as “long toed” however often long toes are actually a case of low heels as trigonometry dictates that reduction of the angle of the hypotenuse increases the base length, conversely this same formula can be used to work out the extra length needed to compensate for the elevation when graduating in any form in addressing a NPA, HL / cosine AE = LH the horizontal length you want on the flat divided by the cosine of the angle of elevation gives you the new length of the hypotenuse you need, ill use this in an example in one of the case studies.
O’Grady also discussed the differences in the solar proportions attributed to the different role it plays (Fig.3)
Fig.3 The shape of the hind is designed to provide traction and enable efficient propulsion primarily. The widest point of the foot is located more palmerly in the hind.
So we have established that the parameters for ideal fore and hind limb hoof conformations may not be the same, therefore comparing the hinds to the fronts to establish what is correct is probably not advisable especially considering their different roles in locomotion, however when it comes to dorso-palmer balance a NPA does predispose to higher pathologies as it would in the front and shoeing to address this conformation will have a remedial effect. An established external reference marker for assessing hind hoof conformation is the coronet trajectory which should fall around the knee of the fore limb, hinds with NPA will often have a trajectory much higher than this, again an example will be shown in one of the following case studies.
Fig.4 Typical hoof conformation and stance of NPA, low crushed heels and a stood under stance. This horse had SI pathology and kissing spine, as well as proximal suspensory desmitis, expressing the link mentioned by the above studies but which caused which?
Fig.5 radiography clearly showed a NPA
Fig.6 Duo ellipse hind (Advocated and principles of which taught to the author by Mark Caldwell and available from the shoeing lab.) fitted to provide elevation while channelling the point of force trajectory away from the compromised structures.
Fig.7 The external geometrics looked improved.
Fig.8 HL / cosine AE = LH
Fig.9 The change in stance from the shoeing application.
This case exhibited the stance highlighted in Mannsman et al (2010), the horse preferred to stand far under himself to relieve the higher pathologies, but in doing so he was crushing his heels, the author sought veterinary intervention to establish related pathologies and the horse was treated for SI and kissing spine at the same time as the shoeing was changed, as its important to appreciate that there is still a chicken and egg situation when it comes to whether the higher pathologies cause the conformation or vice versa, (read my article on disordered physiology and hoof morphology). Fig.9 clearly shows the change in stance achieved by addressing the geometric proportions of the hoof, the author hopes to see continued improvement as we have in Fig.11-13, the second shoeing, in the coronet trajectory over time (shown with the yellow line).
Fig.10 Shows the radiographic improvement of the pedal angle from -9 degrees to neutral after the first shoeing, the second shoeing will look to further improve this.
Fig.11-13 The horse showed improvement in geometric proportions from the first shoeing and was shod in hand made steel duo ellipse hinds as he is beginning work in his rehabilitation programme and to also more accurately place the length and elevation. Fig.13 when compared with Fig.7 shows how the external reference markers including the HPA, coronet trajectory and posture all present closer to the ideal and in turn the horse shows improved comfort in its work as it progresses through its rehabilitation.
Fig.14 Before and after change in posture after addressing the geometric proportions of the hind foot.
You can see from Fig.14 again that what you do to the hind feet has a direct effect on the musculoskeletal system above it, the whole outline of the back end has changed and more closely conforms to the ideals (see my article on creating optimal basal support).
Fig.15 The change in the distal limb from the correction of geometric proportions.
When looking at the distal digit of the hind limb established conformational outlines dictate a right angle triangle is formed through the central axis of the bone and the tarsal should be vertical following the line dropped from the point of buttock. Before the hind shoe was too small allowing prolapse of the caudal hoof over the back and the angle was too acute. The shoe fitted on the right had the basal length worked out by using the trigonometry equation mentioned earlier.
HL / cosine AE = LH, so lets say the length of the base I wanted which could be any where from the widest part of the frog to in line with the bulbs (depending on how much length you want to give it) is for arguments sake 10cm and the angle of elevation is going to be 5 degrees then 10 / cosine 5 = ~10.04 so this tells me that in order for my base to be where I want it after my elevation I need to add an extra .04cm to my starting length. You can see that the extra length and the elevation created geometric proportions far closer to the established ideal.
Fig.16 showing the solar view of Fig.15 you can see the extra length and elevation. The amount of base behind the widest part of the foot although is proving to be less in the hind foot the proportions can still be improved to provide a more optimal bearing surface and therefore posture. This horse was fitted with duo ellipse graduated hinds which channels the point of force trajectory into the central rails, relieving the compromised heels in an effort to create an environment to encourage heel growth to create positive hoof morphology.
Fig.17 The radiograph clearly shows a NPA which correlated with all of the external markers.
Fig18-20 Although this horse could have benefited with more length to compensate for the elevation these images express how the external markers were improved in a horse suspected to have NPA, radiographs are of course preferred and the gold standard in assessing phalangeal alignment however the external markers can give a very good indication, looking for that right angle triangle with a coronet trajectory that aims around the fore knee.
One lesson the author has learnt is to start at the basics and work up from there, this next case is an example of where the basics were applied initially, creating as close to ideal solar proportions (discussed in O’Grady (2019)) as possible with the trim, bearing in mind the difference between the fore and hind. Then putting a shoe on to compliment the trim by emphasising those proportions, often with these NPA’s the length of shoe required can look like it “swamps” the foot from the solar surface (Fig.23) but when you put the foot down it looks like its still not enough.
Fig.21 This Hind coronet trajectory flies straight up into the belly of this horse, its shows a posture described by Mannsman et al (2010) and has a broken back HPA with the bulbs of the heel looking like they are almost touching the floor and falling off the back of the shoe.
Fig. 22 The shoe removed and the toe trimmed down as much as possible to try and establish better proportions, note the vast difference between the length from the widest part to the heels and toe.
Fig.23 The shoe placement compliments the trims efforts to create more ideal proportions, note the new lengths difference between the heels and toe. The toe has been brought back and the heels extended as Mannsman et al (2010) showed the improvement in stance and comfort of the horses presenting with this conformation with the bringing back of the “breakover”, although this term is still debated in the hind limb.
Fig. 24 After addressing the basics the geometric proportions and external markers are still far from ideal even talking into consideration the difference between the fore and hind hooves. When placed on the floor the shoe doesn’t look too big although looking long in the solar view, the heel bulbs appear supported, no longer looking like they are going to prolapse over the back of the shoe, however the coronet trajectory is still way off, this would lead the author to perhaps recommend radiographs to establish the orientation of the distal phalanx possibly leading to more involved shoeing as seen in the previous cases.
As well as the lateral view the same principles can be applied to the rear view of the hinds, picturing ideal and looking to create optimal basal support (see my article on creating optimal basal support).
Fig.25 This horse shows a overly base narrow stance and crushed outside heel of the off hind, after the application of a shoe to support the gravitational line of the limb an improved stance was present.
Fig. 26 The definition of a lateral extension is debated, if the shoe still remains within the confines of the hoof as it would be following the coronet band the author likes to call it a coronet support shoe, but for the purpose of this article we will use a lateral extension, in this image the author is checking the width of the extension and amending it, to NOT provide a lateral extension that causes leverage but to adequately support the foot and limb to encourage improved stance and therefore more correctly born load.
Fig.27 The “Lateral Extension” brings more base symmetry to the contracted lateral heel.
Fig.28 The shoe now fills the space where the hoof should be following the coronet, but not further.
Fig.29 Lateral view of the “extension”.
I started writing this article in response to a question posed to myself,
“Could you elaborate on what are the normal values assigned to the hind feet?
Are we just comparing to the fronts?
Are there any studies we can look at to see what is normal for the hind coffin bone?
Will changing the shoeing behind directly effect the top end?”
So to answer them, The normal values for the hind feet are yet to be researched, documented and understood to the extent of the fore feet, however there are understood parameters as outlined in this article and in further detail in O’Grady (2019), with this knowledge the author does not compare the hind feet with the fore feet but uses external reference markers, radiographs where available and the posture of the entire limb to create a shoeing plan to encourage as close to ideal conformation as possible, which does have an effect on the entire musculoskeletel system, so when you are shoeing the hinds, you are shoeing the entire limb, we must always remember that when you put a shoe on it becomes an integral part of the horse so will effect everything above it and be affected by it, look up and look to create the established ideals don’t get stuck into picking up a foot and just looking at the coronet down.
Dyson S. Diagnosis and management of common suspensory lesions in the forelimbs and hindlimbs of sport horses. Clin Tech Equine Pract 2007;6:179–188.
Mannsman RA, James S, Bilkslager AT, et al. Long toes in the hind feet and pain in the gluteal region: an observational study of 77 horses. J Equine Vet Sci 2010;30:720– 726.