NPA - what is it and how to fix it
This blog post was written by Minna Sarkkinen, an experienced barefoot trimmer who also manages the Flex Boot helpdesk email, helping people all around the world achieve greater hoof health with their horses and ponies.
NPA is a fairly hot topic at the moment, and it's great that people are becoming more aware of this condition and want to fix it in their horses. There's a widely spread belief that the best (or only) way to fix NPA is by using wedge pads in shoes, and we have been asked about the use of wedge pads in Flex Boots. In this blog post we will talk about our personal experiences treating horses with NPA during our professional barefoot trimmer careers. But first, let's talk about what NPA is and what causes it.
What is NPA?
NPA - negative palmar or plantar angle of the pedal bone (depending on if it's the front or back feet), is a hoof morphology where the rear part of P3 is sitting lower than the front part of the bone. The angle of P3 can, and does vary in healthy hooves due to individual conformation, and as such it's impossible to put an exact number on the degrees of positive angle required. It is generally accepted that a slight positive angle of P3, which achieves straight alignment of the bones in the horse's lower leg, is desirable. It could be 5 degrees, or it could be 8 - it depends on each horse.
Above are examples of various hoof angles. None of the horses have been shod. On the left is a low hoof of a high-low footed TB. Middle is a yearling. On the right is a draught X. All these hooves are healthy and sound. Note how the hoof walls are relatively smooth.
What causes negative plantar or palmar angles?
Main cause of NPA is poor development or damage to the digital cushion (let's remember the digital cushion consists of soft tissue), exacerbated by a diet too rich in sugars which prevents strong horn growth. Since the health of the digital cushion dictates the direction of growth of heel horn, it's simple to see that if the digital cushion is not plump and firm, the heels cannot "stand up" in the correct orientation.
This photo shows the classic NPA appearance; low heels, and a bull-nosed dorsal hoof wall. It's a Thoroughbred recently out of shoes. Note the event lines on the hoof wall indicating ongoing inflammation.
This horse has lumbar arthritis and sacroiliac injury. Other photos of this horse are included later in the post, so read on.
So what causes weak digital cushions?
There are a few common things that cause weak digital cushions.
Lack of movement as a youngster is one big factor. The digital cushion is a fatty tissue at birth, designed to strengthen and turn into firm fibro-cartilage in response to the stresses of motion placed on it. When it comes to digital cushion health, the saying "use it or lose it" was never truer.
Shoeing is by far the leading cause of weak digital cushions. A hoof isn't designed to run with peripheral loading, and the soft tissue simply falls through the branches of the shoe, or atrophies away (morphology commonly known as contracted heels). Hardly any shod horse has an appropriate diet, so this contributes a great deal, since the horse is in a constant state of low grade laminitis. Shoeing early in life makes it even worse, since the tissues don't have the opportunity to develop, and adult horses are galloping around with the soft tissue composition of little foals!
A high level eventing horse with a prolapsed frog and very little sole depth. Middle photo is around 2 weeks post shoe removal, and last photo another 6-8 weeks after that. Horse is trimmed weekly by owner and every 4 weeks by professional. Previously he would trip a lot but that stopped immediately after removing shoes and using Flex Boots.
Foundered (laminitic) horses, shod or not, often present with negative plantar (hind feet) angles. If the cause of the founder is removed and a frequent trim is applied, the problem goes away. I find that horses whose inflammation isn't truly resolved, will remain with poor angles, and recovered horses who have a relapse, quickly lose their good angles. Inflammation prevents strong tissue growth - I cannot emphasize this enough!
Diet is key to fixing NPA in foundered, laminitic horses.
Poor angles on a laminitic warm blood, front hooves. Sole view is taken approximately 3 weeks after shoe removal. Very thin "dropped" sole due to distal descent (sinking) and a toe that has stretched forward. No one knew the horse had a problem!
Same horse several months later. This horse's diet wasn't managed and the improvement really kicked in when the grass seasonally dried off, as a matter of "luck". Not the ideal way to approach the problem, but the improvement is still very good.
Below is the hind hoof of the same warmblood horse.
The pictures below belong to a chronic founder pony. The plantar angles have improved with trimming and diet management, over a number of months.
Another cause of NPA is upper body problems. These horses present with problems in their lumbar spine, sacroiliac joint and stifles, to name a few. Since the hoof is like a block of Play-Doh and will conform to pressures placed on it, it makes sense that upper body problems which alter the way the hoof is loaded, are a big issue. It's also known that the horse often stands "camped under" which further stresses the higher structures. Therefore, body work in conjunction with the other changes (diet and trim) is really important. There is a direct link here to the training of the horse too: all the above mentioned parts of the horse, and more, suffer with incorrect training. So it's important to make sure that this is covered, as well as saddle fit issues.
Below is the horse from the earlier hoof image in this blog, showing what body issues on this horse contributed to the poor hoof health.
The yellow arrow points to muscle atrophy by saddle induced nerve damage.
The green arrow points to lumbar spine arthritis.
The purple arrow points to sacroiliac injury and dysfunction.
Lets have a look at his hoof again. Not the best quality photos, but you can see that the frog has prolapsed and there is very little sole depth at the back of the foot. This is a pretty unhealthy picture all round.
It's also important to remember that as the hoof wall grows, the wall at the toe will grow more forwards, and higher at the same time. A high wall at the toe can tip the balance of the hoof backwards.
Above photos show an easy trimming fix; a desert hoof which has built excessive sole due to lack of natural exfoliation, before and after trim photos.
So what can you do if your horse has NPA?
The "normal", common advise you will hear from many vets and farriers is that the horse needs shoes and wedge pads. So it's understandable that people might think that without wedge pads, the horse doesn't stand a chance. And if the owner is reluctant to shoe their horse, using wedge pads in hoof boots is the next logical step.
When we talk about fixing the NPA, what we're really fixing is the internal structures of the hoof, and/or the current trim. We can't magically rotate the bones to their correct position (unless there is excess sole depth at the front of the hoof which can be trimmed away - but this is not a DIY job!). We need to understand what internal structures affect the position of the bones and take action that affects those structures - mainly the digital cushion.
Using wedge pads in hoof boots
We have seen some applications of wedge pads in Flex Boots and none seem to have gone very well. Mainly, because the wedge alters the boot fit because Flex Boots were designed to work with Flex pads, not wedge pads.
Then, since the boots no longer fit properly, they are harder to keep on. I must stress that if a "device" is placed under the horse's hoof, then the horse must live with that device 24/7. It is completely pointless to put a wedge in for riding and then remove it for the rest of the time.
We would prefer the horse not be ridden in the rehab phase than to add a wedge only for when the horse is ridden.
Rubbing can also occur since the straps no longer fit correctly. Correctly fitted Flex Boots never rub!
And it's important to clarify that even if wedge pads were successfully used in boots, if the cause of the problem isn't addressed, the issue with NPA will never go away.
So how can NPA be fixed?
We have had really good success rehabbing hoof problems including navicular (both bone damaged cases, and the preceding soft tissue injuries) with a weekly trim, a diet overhaul and the correct type and amount of padding in the boots, depending on the individual horse. Add in lots of quality movement, and the stage is set for recovery. A lot of horses with "navicular" also have NPA. They almost always also have laminitis that hasn't been recognized.
1. Use hoof boots
We boot and pad to achieve heel first landing which strengthens the back of the foot and in turn improves the angles.
2. Fix the diet
We fix the diet so the laminae can grow in tight and the soles can gain depth, which will improve the angles.
3. Trim frequently
We trim frequently to make sure the hoof capsule is always in a correct form.
4. Allow movement
Movement activates blood flow in the hoof and that aids recovery.
The trick is that everything has to work together, at the same time: the trim, the diet, the training, the movement, and the hoof protection.
Then we rinse and repeat and wait.
That's a long way to say that basically we don't do any "special rehab" at all. How strange does that sound! We treat the horse like we treat any horse, and the problems get better. It seems weird that something so simple and cheap is the answer, but for the majority of the time, it is. Just about every issue that plaques domestic horses can either be eliminated, or greatly improved, by following these simple principles.
But does it always work?
Extremely damaged digital cushions do not always recover completely, we have to be realistic. Depending on the severity of upper body problems in conjunction with the digital cushion damage, some horses heal entirely, and others sufficiently to lead a happy, active life. Some body issues may need ongoing maintenance treatment.
This horse will not have perfect feet. He is older, and also has very contracted heels. But with a better diet and barefoot trimming, he is happy to be ridden in Flex Boots. This change was made in 2 trims, 2 weeks apart. The hoof in the before image will not fit into a Flex boot, but the second image will.
Even the most severe cases can be improved
My recent most spectacular (in terms of the damage) case is a horse with bilateral severe navicular bone damage. Since the owner learned to trim weekly, and used Flex Boots, the horse has been 100% sound for over a year and is training at around elementary level dressage. Prior to this, the horse had been in various shoes and other boots, and barefoot on a “normal” trim cycle with a different technique (leaving the heels very high to lift the angles). He was at best 80% sound “sometimes” and entirely crippled at other times. The owner has also embraced the classical style dressage training to help create correct movement patterns.
Below are two photos of a different horse's hoof with a similar situation. This is a typical "navicular" foot that often gets wedges. The horse was previously shod. These photos are 9 months apart, with a fortnightly trim by the owner and a professional trim every 4 weeks. You can click on the images to see the full photo.
We find this to be the case over and over, and the angles will improve as long as the diet and trim frequency and technique facilitate the healing. Some horses love to live in their boots for a period of time - usually the thin soled ones - others only need the cushioning during riding time.
The hardest cases are usually a Thoroughbred ex-racehorse, who has no depth to the collateral grooves at the back of the foot, meaning the frog has prolapsed completely. The heels at the starting point can be almost in the middle of the hoof but down to the level of the sole, and sometimes completely curled over on themselves. They have to be carefully moved back with small trims. This cannot be done if the sole depth doesn't improve, and hooves like this on a long trim cycle will absolutely not improve. If the normal trim is at 4 weeks, by 7 weeks the heels have curled over again and weeks if not months of progress can be lost just like that. Sometimes this kind of hoof also has excess sole in front of P3 at the front making the issue worse. But even these horses also can get better, and get back to riding comfortably!
A completely crushed digital cushion. By backing the heels and toes weekly and adjusting the diet, the hoof fitted into a custom Flex Boot nicely in a short amount of time, and the horse was able to go back to work and build stronger hooves.
A bit about a correct trim
It's not just a case of trimming frequently enough, but the feet must be trimmed correctly in order for things to get better.
Backing up the toes and heels very frequently (weekly!), along with removing sugars from the diet, will allow a new hoof capsule to grow in, and the usually rearwards ejected heel bulbs can become part of the hoof again. As the distal descent (sinking of P3) improves and sole depth is gained, the heels are able to be moved further back without lowering them more than the horse’s anatomy allows. I get the best results when I attend every 4 weeks, and the owner does weekly maintenance trims in between. Below is an excellent example.
This is a Thoroughbred with heel contraction, distal descent, laminitis and sidebone. Again, no one knew or told the owner that the horse had a problem. Note how the heels look very long, but the hoof wall isn't terribly high. This means P3 has sunk. The heels cannot be trimmed shorter until the sole moves upwards, and to get that to happen, we need to fix the diet and living environment, remove the shoes and trim frequently, so that tighter laminae can grow in, and suspend the bone higher in the hoof capsule. The heel bulbs don't appear to be a part of the hoof capsule but are hanging out the back.
Below is the same hoof from the side, and later after being barefoot for a few years.
Horse has high low front hooves, this is the low foot. We can see how the heels have moved backwards towards the widest part of the frog. They are shorter but more upright. (Note there are still rings appearing on the hoof walls, and red bruising can be seen in the bar laminae - these are signs of low grade laminitis). Thin soles remain due to permanent damage but with boots and pads he is comfortable being ridden.
Even with this approach, recovery takes the time that it takes. Some improvements can be seen almost instantly, but it may take weeks or months for the horse to be ready to be ridden or worked at the level the owner wants. We encourage all horse owners to allow their horse sufficient time to recover, before resuming previous activities.
For horse owners who would like to learn to do the weekly maintenance trims on their horse between professional trims, or even to trim their horse completely on their own, we have created online hoof care courses that teach just this. You can read more about the courses at www.holistichoofcareforhorseowners.com
Fitting hoof boots for horses with NPA
Flex Boots are especially good for providing comfort for horses and ponies with low heels, especially when used with Flex pads. The Flex pads are designed to work with the Flex Boot.
If the dorsal (front) hoof wall is bull-nosed in appearance, boot fit is compromised. This needs to be taken care of - usually these horses have excess sole depth in front of the tip of P3 - but as said before, you should engage an experienced professional trimmer to fix such issues, not attempt to DIY them.
Then, the toes need to go to the front of the boots. The only instances in a permanent sense that I’ve had to modify the boots is for a naturally very upright hoof, where I have heat fitted the front of the shell to stretch the top of it a bit. Otherwise, the weekly trim (or in some cases a trim done every 3 days even) gets me the anatomically correct hoof form in a pretty short amount of time that then works in the boot as well.
Hoof on the left will not fit nicely into a boot. Hoof on the right does.
If I can’t get a great fit straight away, I will resize the boots as soon as I can, and use them as a rehab tool only until then (i.e. horse is not ridden until the hooves are in the right shape).
Do you have questions about how to use Flex Boots to help your horse recover from NPA? Our helpdesk is here to guide you, please email us at email@example.com!