International Hoof Care Summit
By Stuart Muir CFP
Cincinnati, Ohio, USA
2nd February - 6th February 2010.
The international Hoof care summit is a series of lectures held by Frank Lessiter of the American Farriers Journal. The information that was given this year was new and the lecturers supported their hypothesis with scientific evidence to ensure its accuracy. The lecturers always had an attentive audience that were keen to advance their knowledge and skill levels that they could later apply to their practice.
The International hoof care summit was well attended, with farriers and veterinarians coming from all over the world. Attendees came from all over the USA as well as Brazil, Germany the UK, Australia and of course New Zealand. Our party consisted of; Kim Hughes, Dr Rebecca Sutorius, Dr Orla Fahey, and myself. The International Hoof Care Summit was held at the Duke Energy Centre. The complex was very nice with many rooms. Smaller lectures were held during the week in smaller rooms, while the main classroom was where the more recognised speakers displayed their approach to their trades.
There were a wide range of lecturers from around the globe that shared their insight
into the part of the industry that they were actively researching, giving advice to their colleagues on or that they had personally found significant to their career.
The speakers that stood out for me were; Dr Noel Mueller, Randy Luikart, Dr Jeff Thomason, Dr Ricc Redden, Pat Reilly, Red Renchin and Jim Ferrie. All of these speakers had information mainly in the field of biomechanics and the effects that this had on the equine limb and how that directly affects how we as farriers and veterinarians approach our job. At times the lecturers contradicted each other however; they supported their individual viewpoints with logical reasoning.
Dr Jeff Thomason was a speaker that particularly took my interest. Dr Thomason is an Anatomy Professor in the Department of Biomedical Sciences at the Ontario Veterinary College and is internationally renowned for his research on equine hoof anatomy and mechanics. Dr Thomason's research is partly unpublished, but the information seemed logical and reasonable. Dr Thomason's research was manly in regard to studying the effects of weight being dissipated throughout the limb during all phases of landing, from the first instance of weight bearing through to break over.
Dr Thomason broke down the landing phase of the limb into 4 basic moments. The term "moments" were used, as the actual time the limb was in each particular phase and was measured in milliseconds. Dr Thomason viewed the equine hoof at this point as nothing more than a "black box" with no particular characteristics.
The first phase was primary impact, the first direct 'slamming' effect of the hoof on the ground. Dr Thomason best described this with the analogy - hammer to nail; a very quick deceleration of the limb. Dr Thomason used an accelerometer and pressure plates that measured the acceleration that the hoof underwent during each phase and graphed these results. He showed, with the use of a PowerPoint presentation, a graph depicting a huge "spike". This "spike" then was very quickly backed up by a series of little shudders almost as you would view aftershocks on a Richter scale. These tremors, to continue the metaphor, represented the hoof sliding to a stop prior to the weight baring phase.
This 'secondary impact' or shudders/tremors were actually the most damaging to the hoof capsule, as this is when the force of the horse is pushing its weight down and forwards into the hoof capsule, putting tremendous strain on the internal structures. This is the phase that the lamellae come under extreme pressure as the horse is trying to stabilise the hoof to allow full loading of the limb. This is also the phase when the suspensory ligament and deep digital flexor tendon start the task of taking the body weight through the fetlock region.
Dr Thomason noted that while the horse moves at the walk holding 1x body weight in the fetlock and 1x body weight in the hoof capsule, this changes when the horse moves into a medium trot. The changes to loading are 1 x bodyweight in the hoof capsule, while the fetlock region loading has doubled. This is simply the affect of the body weight of the horse pushing downwards into the fetlock with more velocity. Dr Thomason did not elaborate on whether or not the same formula continues to work through further changing of gait or speed.
It was also mentioned that the vibrations that the hoof undertook were absorbed by the hoof wall and lamellae, while the actual velocity/weight of the animal was taken through the suspensory/shock absorption mechanism of the limb.
The next phase of the stride was termed "midstance"; the load-bearing phase where the limb is under full load and the animal passes directly over the top the limb. This is when the suspensory ligament and deep digital flexor tendon are under full load. This was depicted on the graph as a gradual incline and decline. Interestingly, Dr Thomason went on to say that the next phase "roll over" was as the animal was moving through the last 25% of the decline phase of this graphic. Ground conditions have variable effects on 'midstance'.
The final phase of the stride was the "roll over". Dr Thomason informed us that "roll
over" should not be confused with "break over"; break over being the point that the farrier installs the last point of purchase on the lever arm of the limb. The lever arm of the limb is best described as the distance from the centre of the distal point of the metacarpal to the most dorsal aspect of the hoof capsule or shoe placement (or where ever "break over" is placed around the centre of rotation).
"Roll over" is when the limb has loaded onto the toe region of the hoof with the muscles and tendons levering the horse into dynamic movement. It is also at this point that there is another "spike" on the graph as the tendons start recoiling up the leg resetting themselves for another cycle. Body propulsion takes less pressure on the vector once in locomotion, as the velocity is all ready in place.
1st phase.......... the only phase of concussion (impact landing)
2nd phase........ slide and stopping of the limb (soft tissue damage)
3rd phase ......... maximum peak forces (midstance)
4th phase ......... tendon recoil (roll over)
The second part to body weight distribution is "ground force reaction"; the effects of the ground interacting with the hoof capsule. Dr Thomason showed the effects of "ground force reaction" with simple pictures of the limb. He pointed out the loading force during the "weight loading phase" was over the entire hoof but the majority of pressure is taken slightly forward of the "centre of rotation".
He also took this a step further, showing the pressure relationship as the horse was in the "break over" phase of locomotion. This showed the weight/force shifting forward as the horse started to move over the top of the leg.
For farriers the "roll over/break over" phase is one of the most important phases as it is one of the few phases we try to control. Without balance and structural integrity of the hoof capsule, the torque on the lever arm can quickly damage the tubules within the hoofs structural mechanism.
When trimming the hoof, interrupting the internal stratum or medium stratum is starting to decrease the structural integrity of that hoof capsule, meaning that when the horse loads weight onto the toe region, the forces on the dorsal wall are greater than the weight the wall can carry without it becoming distorted.
Structural integrity of the hoof capsule was a topic that was discussed with by a variety of speakers. Palmar angle of the pedal bone was also discussed with some great footage of the effects of the limb bearing weight through radiographs played in succession showing the internal structures truly working with the horse in locomotion.
Other areas of interest for me were sole depth, and caudal heel pain.
Dr Ricc Redden has a wealth of knowledge with his own ideas on how the equine limb starts to get into negative territory in relation to its health and balance. Dr. Ricc Redden, an innovative veterinarian, farrier and horseman, is on the cutting edge of technology in developing his ideas. Dr Redden believes that the reason for poor hoof growth is that sole depth has been compromised too many times by over trimming, thereby 'shunting' the papillae into a point of not growing or excreting horn. He also said that the circumflex artery would then be in a state of shock from being compressed on the ground surface until circulation was nearly non-existent. He also mentioned that without the mechanics of the hoof operating correctly, the papillae would not return to full health function.
Pat Reilly was another speaker that has researched a different approach of finding mediolateral balance in the hoof capsule. Pat Reilly had been the resident farrier at Rochester Equine Clinic in New Hampshire since 1998 until its closure in 2005.
Pat Reilly started his lecture explaining that his work is controversial but he backed up his hypothesis with clinical facts that he has spent time researching over the past few years. His theory was that when veterinarians and farriers assess mediolateral balance it is usually done in a static position and without much consideration of dynamic balance. So he devised a way to access dynamic balance in the horse to see if the outcome was the same - static to dynamic. The outcomes were quite interesting as he proved that a horse that appeared to land on the lateral aspect of the hoof capsule first at the walk, could actually indeed be perfectly balanced at the trot. He proved this by installing pressure pads under the hoof that were attached to wires that ran up the horses leg to the rider where the information could be stored and gathered later.
Another point that Pat Reilly brought up was that mediolateral discrepancies that we see in the interphalangeal joints were not as easy to realign as we thought. Pat Reilly showed examples of a horse with a mediolateral imbalance through the distal interphalangeal joint. He then applied wedged pads to the lateral side of the hoof to "re adjust" the imbalance. He demonstrated that it took a 9 degree wedge before any significant change was made to the actual joint in question. At this point a view from the palmar aspect showed that the horse was no longer loading the medial side at all; it was in effect 'floating'. With the information gathered from this speaker it is great to know that there is still research to be done on the effects of the horse and farrier relationship and I am keen to see the developments of this in years to come.
After returning to New Zealand from the International Hoof Care Summit, It has been interesting re-evaluating client's horses and looking at each case in a new light. I have made changes to many horses that I otherwise wouldn't have done. With a clearer picture of how the horse works and the knowing value of including bio-mechanical theory into many shoeing jobs it is pleasing to see horses becoming sounder faster, or just clients pleased with how their horse is going. It has made a large improvement being able to run ideas past local veterinarians and having their support knowing that we are aiming for the same result. Working in the equine field many of our remedial jobs have to be explained to the client as to why they need the care they do. It is satisfying when correct knowledge and good shoeing practice works out for all parties.
I would like to thank the New Zealand Equine Research Foundation for allowing me the opportunity to attend the International Hoof Care Summit. Without their help this would not have been possible. Many thanks.