fig 1

Negative Plane P3 Syndrome

Negative Plane Distal Phalanx (Pedal Bone) in Hind Feet

Negative Plane Distal Phalanx Syndrome

There are many types of subtle equine lameness. It is uncommon to recognise the symptoms as being linked to the feet. Typically foot problems affect more than one area of the upper body. It is quite common with observant equine owners, trainers, farriers and vets, to see and recognize stiffness in the rear quarters. Frequently horses that are reluctant to move freely are resistant to work and require longer warm up times than one would consider normal.

How do we determine if the horse has a negative plane distal phalanx?A negative plane distal phalanx is not always easily observed unless x rays are taken first. However, other injuries or symptoms may become apparent prior to further investigation. All these injuries and conditions are directly related to the condition of a negative plane distal phalanx.
  • Hock pain
  • Stifle pain
  • High suspensory strains
  • Filled legs which go down following work
  • Tight hamstrings or injuries
  • Strains of the suspensory apparatus - predominately proximal (high) suspensory desmitis (strains)
  • In front feet, check ligament injuries and mild fore limb lameness
  • Kissing spines
  • Constant back pain and the need for continuous therapeutic treatments, i.e. chiropractic physiotherapy and acupuncture. In particular sacroiliac injuries or general pain around the area
  • The above ailments are some of the most common found in horses with a Negative Plane Distal Phalanx.
  • The external indicators are that the horse does not land slightly heel first, thus engaging the back parts of the foot on the ground first.
  • The frog is diseased of dysfunctional.
  • The dorsal wall has a domed appearance to it.
  • Although this condition is found in the front limbs of horses, I have found a greater incidence in the hind limbs.
  • A line drawn along the line of the coronary band on the hind foot should bisect the front limb just behind the knee. On horses with NPDP syndrome, this line will often bisect the front limb at the elbow or above.
  • When examining the foot closely from the side (lateral view), there is commonly a crown or arch to the dorsal hoof wall this often corresponds with heels that are very unstable and appear to crumble easily under the weight and movement. Along with what seems to be poor heels, the frog is very large and has descended through the shoe to meet the ground. (Fig 1) With hoof tester examination, a positive response is common in the sole behind the widest part of the foot, through the heels and occasionally over the frog. Regardless of the pain response from the hoof testers (painful or pain free), the discomfort that exists when manipulating the limb, the dorsal wall arch and the prolapsed (enlarged) frog are the main indicators that lead to suspicion of a Negative Plane Distal Phalanx. This, means that the bottom surface of the distal phalanx that is normally elevated slightly more in the rear than in the front (2° - 5°) or in some cases parallel, is actually closer to the ground in the rear of the bone than in the front.(Fig 2 Normalangle – Fig 3 NPDP syndrome)

    fig 1

    Fig1

    fig 2

    Fig2

    fig 3

    Fig 3 it is seldom the failure of one single structure that causes the distal phalanx to obtain a negative plane. It is my belief that most or all of the above structures have a contribution to make or are altered in some way in this process. Are there other factors that cause a negative plane distal phalanx? Domestication has played the greatest role in the demise of the functional distal limb. We have taken equines from their natural environment where Mother Nature could dictate the plan she has worked out for optimal maintenance of the equine digit in each particular environment. It follows then that, domestic equines feet cannot be maintained in that optional environment. Hoof distortions will occur despite our efforts to manage them. Good foot health is married to foot function, with most of our domestic equines unable to find access to large enough areas to maintain optimal foot health so it is no surprise feet become dysfunctional and diseased. We have not been selective in our breeding policies and paid little attention to the long term consequences of creating a poor gene pool. We have consistently bred from horses that had gone lame and were no further use for work. Can you imagine the disaster if a motor manufacturer took the worst parts from all its models and combined them into one new model?It is my belief the way we have approached foot trimming and shoe placement is the largest contributing factor in NPDP Syndrome. We have to question the reason we have shod horses in the past. Has farriery become like tyre changing? Have we just shod horses to enable us to travel over greater distances?

    Remember! The foot trimming protocol we have attached such importance to was developed for military use. Here the military dictated the size of horse, type, colour and foot size. The work regimes were strictly adhered to and ever part of the horse’s life was managed for the best results within the confines of that very specific environment. Unfortunately military horses had short working lives and most were retired early in their life.

    How does the life cycle of the military horse convert to our domestic equines? I suggest, not well. We have based our systems of farriery upon these military criteria. We all desire, a one to three ratio, between the heel and the toe. It is desired to achieve a 50° angle on a front foot and a 55° angle on a hind foot. If you mark the widest part of the foot and shoe half to the shoe should be ahead of the centre line and half should be behind that line. Is this formula relevant in to-days domestic environment? Although I have utilised this military criteria for farriery for many years, I now believe with the up to date research on foot trimming and shoe fitting protocol pointing us away from those farriery principles we have placed our trust in.

    Is it time for a change of protocol?

    Dr Bowker DVM, from Michigan State University and others, consider that the health of the digital cushion is dictated by the environment the foal is born into. If the foal is born into a soft domestic environment without access to large areas of dry hard ground to roam around, then the digital cushion will not reach its optimal potential for functional health to sustain the horse throughout its life. However, if the horse is privileged to a more natural environment, with large areas of dry hard ground to roam in from birth, then the digital cushion will develop to its optimum for functional soundness throughout the horse’s life. Correct development will see a large amount of cartilaginous tissue in the digital cushion, whereas incorrect development will only provide little or no cartilaginous tissue within the digital cushion. One could logically suspect that the situation is created by trying to leave heels tall to achieve pastern alignment to raise the angle. This approach is clearly responsible for an unhealthy under-run heel condition that causes severely curved bars and curved heels that crumble under the weight of the animal. In addition, low level pain, bruising and abscessing are often the result of this practice and it validates unwillingness for the horse to engage the rear of the foot on the ground first. The enlarged frog is a natural response by the foot to supply support to the back of foot when the normal structures are not available to service those duties. Typically in this situation, the frog is very healthy and is level with the ground through the shoe at the end of the shoeing period.X’ ray protocol;Although you may only suspect either the front or hind feet are involved, insist that all four feet are investigated. Remove the shoes from the horse prior to taking the ‘x’ rays. Clean away any debris from the soles and frogs.There are some very specific requirements for taking good reliable lateral foot ‘x’ rays.
  • The horse needs to be stood with either both front or hind limbs on blocks of identical height.
  • The blocks must have a ground marker set into the block.
  • The limbs must be vertical.
  • There must be a thumb tack placed into the true tip of the frog. (This is the point where the tip of the frog inserts down through the sole)
  • There should be a dorsal wall marker. (This marker should be placed at the point where the lowest hairs are coming out of the coronary band)
  • Measurements;Now the ‘x’ rays have been taken and processed, measurements can be made to establish breakover directly under the distal border of the distal phalanx. Using the ‘x’ rays measure from the point of the thumb tack forwards to the distal border of the distal phalanx. Note;in a normal healthy foot, breakover should occur 0.6cm (1/4”) in a front foot and 0.3cm (1/8”) in the hind feet, ahead of the distal border of the distal phalanx. The treatment of this condition requires breakover to be directly beneath or slightly behind the distal border of the distal phalanx.Once the measurements have been taken, transfer them to the foot. Place the end of the ruler at the tip of the thumb tack and measure forwards and mark breakover directly over the distal border of the distal phalanx. Continue this mark onto the hoof wall. The reason for this is, once the foot is filled with impression material any marks on the sole of the foot will be obscured.We now know exactly where the position of the shoes needs to be we can fit them to the foot.Choice of shoeing systems; Many feet in moist areas with this condition will only widen when the increased support of the enlarged frog is being compressed within the back of the foot. Only temporary results are seen and in time the condition can return. In these marginal barefoot attempts, the use of shoes and a hard Multi-Purpose plate are the first in a series of treatment procedures. It is not uncommon for a horse to be uncomfortable standing once the shoe is removed and the heels are trimmed to the level of the live sole. Properly preparing the bars and heels to the Natural Balance standards is necessary for reconstruction of the back of the foot. The discomfort is occasionally experienced temporarily I assure you, but is required to improve the situation. The mistake commonly made by most farriers, myself included, is to not allow the frog to be loaded, hence, exacerbating the condition. It works best if the horse can be left barefoot and housed in a confined area on a flat, firm surface for a period of 24 to 48 hours until the frog is repositioned comfortably within the foot. The original discomfort will disappear within hours.An aluminium NBS, steel NBS, or EDSS shoes, along with the Multi-Purpose plate works well for the initial application after the 24 to 48 hour adjustment period. An Elite Hind steel shoe is best suited for hind feet applications, along with a Multi-purpose plate. I find that Sole Pack works best as a filler beneath the pad, the reason being is that the frog has to continue to deviate and conform to its new position within the back of the foot. If Impression Material is used on the first shoeing, the frog would be limited in its ability to deform properly and comfortably. The shoe and pad can be secured with as many nails as necessary, including nails used behind the widest part of the foot. A heel first landing is generally seen with the first shoeing, if not immediately, then generally within a few days. If the horse fails to land heel first within a few days, elevation with rails or wedge pads may be necessary to achieve these goals.With a heel first landing and regular work, much of the back pain and rear leg stiffness is reduced, and in many cases eliminated. Over the next 2 or 3 shoeings at 6 to 8 week intervals, Impression Material can be used as the next level of treatment in combination with, Natural Balance pads (Figs 4 and 5) either flat -wedge or The Equine Digit Support System. Both these systems I use in conjunction with sole ssupport impression material. If the distal phalanx has a very negative angle, the horse is lame or lands toe first, I will almost always use the EDSS system. My reason for this is the adjustability of the system. I have found it more useful to me under these circumstances as it allows me to achieve my goals on the first attempt.

    fig 4

    Fig 4

    fig 5

    Fig 5 Summary; There is overwhelming evidence, supported by the scientific community, indicating perimeter shoeing (breakover occurring too far ahead of the distal phalanx) and leaving high heels are the major contributors to the onset of this condition. Further considerations are the prevention of an unhealthy digital cushion. The way we breed foals and the environment the foals spend their first few months in, has a direct influence in the development of a healthy digital cushion. For success in the long term breakover should remain directly beneath the distal border of the distal phalanx and good foot trimming principles (i.e. Natural Balance trimming method) should be employed. References and acknowledgements; New Hope for Soundness Author, Gene Ovnicek - The Equine Distal Limb Author, Jean-Marie Denoix - Limbs of the EquineAuthor, Le Roy Amos - Equine Locomotion Authors, Willem Beckand and Hillary Clayton - The Horses Foot Author, Christopher Pollit - Corrective Farriery Author, Simon Curtis FWCF - Breakover Dr Bowker, Hagen and Dr Barbra Page -Biomechanics of the Equine Hoof Capsule Using Finite Elements Analysis (FEA) Author, Dr Christine Hinterhofer - Sensory Receptors in the Equine Foot Author, R M Bowker VMD, Phd - Functional anatomy of the cartilage of the distal phalanx and digital cushion in the equine foot and hemodynamic flow hypothesis of energy dissipation Author R M Bowker The effect of shoe type, design and material on the forces in the distal limb Author, Alan Wilson MRCVS. - The Breakover of the Foot and its effect on Structures and Forces within the Foot.Authors, Hagen, Page, with Bowker and Ovnicek - Adams Lameness in Horses Author, Ted S Stashak - Hind Limb Alignment Clive Meers Rainger B11 NBCF CLS

     

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