The Bars (10-25-06) with 2018 edits Pete Ramey
"Please don't twist this article into the thought that excess bar pressure can't do harm. The bars, sole frog and walls each have weight bearing responsibilities and excess pressure to each of them can certainly cause problems. The change in my understanding, thought process and trimming is that the bars “like” to share more of the load than I previously thought. How much? It varies from case to case; mostly by terrain, health and use of the individual hoof." Pete
Like most natural hoof care practitioners who learned at the same time I did, I came from a traditional shoeing background, then studied the early barefoot works of Jackson and Strasser and took their early insights to the horse, searching for more answers. For years I routinely trimmed the bars and the sole ridge that extends from them (along the frog) to the level and flow of the rest of the natural, callused sole plane without giving it much thought. I saw a great deal of success, but in hindsight only a shadow of what I see now. I was stuck in the thought that pressure to the bar region needed to be reduced and kept to a minimum, even as I constantly said, “Nature would not and did not put anything on the bottom of the horse that was not intended to bear weight” and “Nothing is passive on the bottom of the foot in varied terrain; everything that casts a shadow bears weight.”
I believe the bar pressure phobia came first from horseshoers, who see constant demonstrations that bar pressure on a shoe causes local bruising and abscesses. This gave many farriers the idea that the bars weren’t supposed to bear any weight. But as with the sole corium, the bar corium is damaged by constant pressure, as with having a shoe “clamped on” tightly. The bar corium, like the sole corium thrives under pressure and release only. There is a huge difference between the two.
Then the early barefoot trimmers started carving out the sole and bars from the back of the foot in an attempt to increase the flexibility of the foot. The now over-exposed coriums bruised and abscessed, I believe simply because of a lack of armor. They mistakenly blamed excess bar pressure, and carved them away even more. But I have found that if bars are maintained at about a 3/4" thickness and the horse is managed barefoot and booted, the bars are actually a strong place to bear the brunt of impact force – nature put them there for a reason.
In addition to that, there are countless teachings out there that try to convince folks that you can relieve corium pressure to an area on the bottom of the horse by thinning or concaving away its armor – just carve 1/16” of “relief” and POOF, no more pressure to the region, right? Perhaps if horses only stood perfectly still on hard, flat surfaces this might be partially true. But the second a horse steps into motion; the second it steps onto terrain the foot can sink into, the pressure to the corium is increased by carving away its armor. Never forget it.
Shod horses come out of shoes much more comfortably if you leave 1/4” of bar wall standing above the sole plane. This also immediately and very dramatically increases the soundness and traction of most barefoot horses. The bars will almost always start to maintain their own height at the level of the sole or perhaps 1/8” to 1/4” longer than the sole if you leave them alone. The less you trim the bars, the shorter they become! The flip-side is that the more routinely you trim the bars, the quicker they pop back and “need” to be trimmed again. Leaving a longer bar (and sole ridge around the frog) accelerates the process of achieving a deeply concaved sole by providing support to the internal structures and reducing sole wear. I already learned this lesson about the other parts of the foot years ago. The less I trimmed the sole, the deeper the solar concavity became. The less I shortened the foot, the shorter the foot became. The less I trimmed frogs, the sounder the horses were, and the frogs didn’t get taller, just more callused. Every time I have learned to back off, my horses became more comfortable and the rehabilitation of pathologies accomplished more quickly. I was a just a bit slower in seeing the same truth about the bars. Now I’ve come to view them as a critically important weight-bearing structure and see that as with every other part of the foot, over-trimming them makes them grow too long, too fast.
A basic guideline I'm starting to embrace is this: If more than 1/4-inch of any part of the foot “needs” to be removed at a four week maintenance trim, that spot was probably over-trimmed at the last visit. Not by any expert's standard, but by the horse's standard in its given terrain and given the current health of the internal structures (the horse will work overtime to replace needed material if it is removed). This is a strong statement, I know, but I'm learning to trust it more every day. How do you apply this? Not by just leaving all of the excess, but by always leaving anything that pops back an 1/8-inch longer than you did at the last trim. You'll be amazed as you watch the excess growth immediately slow down – the hooves will move towards self-maintenance.
This does not mean you should allow a flared bar to lay on top of the sole. If a bar is flared out of any reasonable support role, I do tend to trim it to or just slightly longer than the level of the sole to try to encourage/allow straighter growth for the future. But people who take this a step further – cutting sole and bar together, looking for straight bar tubules near the corium are making a big mistake. The real secret to straight, strong bars is heel-first impact, and that type of trimming puts horses on their tiptoes, perpetuating the problem.
What is "the right" bar length? As discussed at length in the previous article One Foot for All Seasons? it varies dramatically with terrain. The bars need enough relief (solar concavity or slope from the heels) that they can descend as the hoof expands, but more importantly, they need to be in place to "bottom out" to provide vertical support at peak impact loads – transferring energy into the flexible lateral cartilages. On hard, flat terrain, a 1/4-inch taper from the heel buttress to the end of the bar might be perfect. On rocky terrain, much more taper or concavity may be necessary. On soft arena footing the same goals and support ratio may require a bar to be longer than the hoof walls. Severely foundered horses; particularly "sinkers" often love to have all or most of their weight carried by the bars, as do Thoroughbred types with wholesale lamellar separation..... I wish it were easier, but honestly listening to the hoof will take you to the right place.
Now enter the latest research from Dr. Bowker. He and his team at MSU have discovered that much of the intertubular sole material is actually being produced from the bar laminae and migrates outward, flowing around the sole tubeules, toward the outer periphery. This is something we should have noticed in the field. Have you ever seen a hole in the sole that was made by someone trying to dig for an abscess or drain a puncture wound? Did it fill back in with new sole material? No, it eventually migrated forward and out the front, didn’t it?! The results of the studies are not complete; the research is currently ongoing, but it appears that relatively little of the total mass of the sole is actually being produced from the outer inch of the sole's corium – just enough to help move the greater mass of sole coming from the bar laminae along in its journey to the outer periphery.
This works much like the keratin cells produced from the laminae aid in moving the larger mass of hoof wall growth down from the coronet, except in the case of the sole, the tubeules run straight from the solar papillae to ground on a 45-ish degree angle, generally paralleling the dorsal aspect of P3. Meanwhile, intertubular sole horn is flowing from the bar laminae (and the solar corium adjacent to the frog) toward the outer periphery. These new cells flow around the sole tubules like a slow-moving river flowing through a cypress forest. Dr. Bowker and I studied this both by backtracking spots of pigment in the sole to their origin of growth on cadaver feet and later in live horses, by embedding BBs in the sole and photographing spots of pigment in the sole flowing past the BBs over time.
This brings up some very important things to understand when trying to help hooves recover from various pathologies. Since the same structures (bar laminae) are responsible for producing both bar material and much of the mass of the sole of the horse. If the horse is constantly working to replace bar material you are trimming away, it can probably reduce the ability to build sole that would eventually be positioned under the toe! This is why it is important to try to achieve self-maintaining bars by leaving them a bit too long and thus slowing down their rate of growth. I believe it 'frees up' the bar laminae to send a larger amount of sole out to the distal border of P3.
[Admittedly, this has been difficult to study. If you do something to a foot and it responds well, you really don't know exactly how the foot would have responded if you had done something different. I can say for sure that it seems far rarer for a foot to refuse to build sole at the toe when little or no trimming is done to the bars and sole ridge adjacent to the frog.]
Secondly, when you see a thin-soled horse with heavy ridges of sole along the frogs and/or wrapping around the apex of the frog, realize this material is not necessarily building upward into even taller lumps. Much of the material is traveling outward, on its way to the callus ridge under the distal border of P3 where it is needed most. This is why thin soled horses tend to build these ridges and horses with thick, concaved soles tend not to. The thinned soled horse is working overtime to try to spread sole material toward the white line and these ridges of sole should not be trimmed all the way down, but should be allowed to do their job of vertical support and sole building. Can they inhibit hoof expansion? Not as much as the decreased movement caused by pain from thin soles!
Since the collateral grooves tend to be 7/16” (9mm) away from the corium, if you concave the sole all the way to the bottom of the collateral groove around the apex of the frog, you will have cut the sole too thin (right side of drawing). In order for the entire sole to be of adequate (5/8”-15mm) thickness (much needed for safety and soundness), there needs to be a 1/4-3/8” vertical drop-off into the collateral grooves adjacent to the frog (left side of drawing). Note that the collateral groove heights-off-the-ground are the same on both sides, but the left side has a much thicker sole.
The same reasoning is important when considering the sole ridges that tend to pop up along the sides of the frog. On the right side of the photo, the sole ridge is simply the horse growing adequate sole thickness in that spot – leave it alone, and hope that adequate thickness spreads to the rest of the sole. Look for that 1/4” vertical drop-off into the collateral groove. On the left side of the photo, there is a 1/2”-tall drop-off into the collateral groove – this ridge of sole has formed on top of an adequately thick sole. It might be appropriate to trim this ridge off so that the drop-off is only 1/4” deep, though do consider that it might also be a terrain adaption (See the article http://www.hoofrehab.com/Seasons.html)
The one part of the foot that can and does replace lost material the quickest and most directly is the area of bar and sole alongside the frog. The growth capacity of this region is incredible and it doesn't have far to go. The bars and the sole ridge that often extends from them (parallel to the frog) can seem uncontrollable in its rapid growth, particularly when the laminae are destroyed or compromised in the wake of laminitis and when the soles under P3 are too thin. One reason for this is that the blood supply comes in directly via vessels that are dedicated to the region. This circulation is not reduced during acute laminitis or excess pressure to the outer periphery of the solar corium. In contrast, the outer periphery of the solar corium is nourished by blood vessels that come in through the coronary corium, then feed the dermal laminae, then the circumflex artery, then finally wrap underneath to nourish the solar corium.
Is this capacity for growth an accident? A mistake by nature? Something we should do battle with? I think not. The bars lie directly beneath the lateral cartilages. They are positioned perfectly to transfer impact energy directly to the all-important, flexible foundation of cartilage in the back of the foot. It may not be natural for this region to be in a primary support role, but it can temporarily step up to the task when the sole and lamellar connections are failing.
The sole ridge along the frog (the thickest part of the sole), also nourished by the same pathway as the bars, is positioned perfectly for direct support of the coffin bone in the front half of the foot. The sole's corium is thin in this region, but much thicker in the outer periphery. This allows for expansion of the front half of the foot as P3 compresses the thick cushion of blood in its outer periphery (between the distal border of P3 and the sole). For years, I have felt that the sole is the primary weight-bearing surface of the foot, but the more time I spend with Dr. Bowker, the more strongly I feel the primary natural weight bearing (actually impact bearing) structure for the equine foot is actually the bars. In the healthiest of feet, the frog should start to impact the terrain first, absorbing some energy as it compresses. Then, the heel buttresses, thus the bars should start to hit the ground, transferring more of the impact energy directly into the flexible lateral cartilages. Finally, by the time the sole is starting to transfer impact energy into the coffin bone, much of the impact energy has already been absorbed. More energy is then dissipated as the coffin bone loads and compresses the cushion of blood underneath (Bowker '99). By the time the toe walls are finally engaged, most of the impact energy has already been dissipated. Indeed when a healthy hoof hits the ground heel-first, there is comparably little energy or vibration left to be absorbed by the rest of the limb and body.
It has been at least ten years since I believed the outer walls were the primary weight-bearing structure. It just doesn't make structural sense for nature to so precariously hang the weight-bearing structure on the side of the coffin bone and lateral cartilages. It seems equally insane to think we should waste so much energy dissipating potential built into the horse by doing anything that could cause the slightest sensitivity in the back of the foot. When a horse is sensitive in the back of the foot – voluntarily landing toe first, ALL of the energy dissipating features of the foot are completely erased. In all other hooved animals it is well understood that the 'pads' underneath are to support weight and impact energy – the hoof walls are armor plating to protect the internal structures from blow from the side (kicking a rock) and perhaps as a traction or digging tool. Why is it so different for a horse? Only incorrect traditional thought, in my opinion. That said, why were so many of us taught to relieve pressure on the bars? And why have we ignored nature's attempts to rapidly replace the bars when we trim them down to the sole plane? They are the one structure most capable of direct energy transfer into the lateral cartilages. The lateral cartilages are forming the flexible foundation for the back of the foot so they can absorb most of the initial impact energy so the bones, joints, tendons and ligaments are not over-stressed.
In my personal journey, the more I've been willing to load the bars, the quicker I am able to achieve rock-crushing soundness for my clients. That's the less significant news, though. The same attitude about the bars accelerates founder and navicular rehabilitation. A radical idea? Perhaps, but give it a try – it works and you'll see the results almost immediately. Food for thought, “There’s no such thing as a good habit!” Think before you cut, and if you trim something away that pops back in two weeks, always know that you made a mistake.