Indepth Equine Podiatry Symposium Notes
Written and presented Summer 2010 by R.F. (Ric) Redden, DVM
Frequently, the chronic laminitis horse is confused with the acute case, and is often treated the same way. This misunderstanding and misconception continues to stifle progress in the field of podiatry. Many definitions of acute and chronic have been proposed, however when we have working knowledge of the sequence of events that can be clearly identified by a physical exam, radiographs and venograms we can formulate a treatment regimen tailored not only for this stage of the syndrome but for each foot involved. Personally I consider cases to be in the chronic stage after the acute phase has passed through the largest window of response, which normally occurs 4-6 weeks from onset. An exception is the high scale case that goes off the radar screen within the first few days of the syndrome. The feet are physiologically dead within hours of onset and slough in a matter of days. The window of response for these cases is extremely short relative to the average acute case.
Chronic cases suffer from the cumulative damage that is caused by compromised blood flow to the vital areas of the hoof. Chronic sole compression thins the sole and erodes the apex. Toe growth all but stops due to dorsal coronary plexus compromise, and the ever increasing PA prevents heel loading, which causes excessive heel growth. The cumulative effects are the result of a cascading series of events that is relative to the damage at onset or efficiency of the emergency treatment and the mechanical protocol that follows. The chronic case is no longer considered a red alert, but certainly demands prompt attention as many cases remain very painful even months to years from onset. Regardless of the stage presented, it behooves us to follow a disciplined, methodical discovery protocol that helps define the degree of vascular, soft tissue and bone damage; determine soft tissue parameters and establish client goals as we formulate a treatment protocol.
Case 1: Show horse with pre-symptomatic chronic laminitis
This case may have a history of intermittent soreness, though not necessarily lameness, scoring less than Obel grade 1 of 5. The foot may have increased heat and often pulse, usually in one foot, and often stands with the affected foot positioned forward of the other. However, the horse warms out of soreness and continues to compete.
This could describe many different problems and is often thought to be quite insignificant when there are no other findings. The lateral low beam, soft tissue radiograph will help confirm that very low grade laminitis is present. There will be no signs of rotation or sinking, but a close look at the HL zone reveals it is 2-5mm wider than it is on the opposite foot. When both front feet are involved, the HL zones can be compared to the hind feet, which will normally be the same as the front feet unless pathology is involved. To further confirm that the wider L side is evidence of low grade laminitis, perform a venogram and compare the findings to that of other healthy feet. The vascular pattern will be quite different.
Treatment: Depending on the degree of vascular alteration and the length of time that has passed since the first indications that there was a problem, I treat cases such as this with a medium score rocker rail that provides a 12-15 degree PA and recommend very light exercise and a follow up venogram in 30-45 days. At that time the vascular pattern should be improved, revealing demonstrable solar papillae; a tighter, denser dorsal supply; good medial/lateral coronary and quarter supply and a continuous flow over the extensor process. Sole depth should have increased by several millimeters and horn growth should be accelerated, evidenced by a new growth pattern that should be equal at the medial and lateral quarters unless prior growth history produced otherwise.
These cases can respond well to this method of treatment, though several resets using moderate mechanics to aid vascular and soft tissue repair may be required for the best long term results. The training schedule should be kept light until the new horn has grown to the level of the apex, which takes approximately 4-6 months. Closely monitor the soft tissue parameters as the new hoof grows out. The L side measurement should return to normal and the new horn will show a distinctly tighter growth pattern that can continue provided the mechanics that release DDF tension are maintained.
Same case, 30 days later. Note HL zone, 20/18mm. This is evidence of the mechanical action of the Ultimates.
Case 2: Low scale chronic laminitis
This case presents weeks to months from onset with lameness grade 2/5 or less and the following soft tissue parameters: distal HL zone widening of 3-5mm, PA 5-10 degree (depending on prior history when a club foot is present) sole depth 15+mm and no lucent zone along the endodermal/ectodermal junction. Why is the timing of onset important here? Though the same radiographic signs can be visible in the first few days to weeks of onset, the mechanical plan for the acute case will be totally different from the chronic case, as two to three months from onset the acute stage has passed. Capsular rotation and other parameters have basically become static.
Treatment:: The good news is the majority of capsular rotation can be reversed with efficient mechanical enhancement that will adequately reduce DDF tension using shoes or Redden Ultimates (as seen in the case below) that greatly reduce DDF tension or various levels of surgical correction, e.g. inferior check desmotomy, DDF tenotomy proximal to the attachment of the check or DDF tenotomy distal to the attachment, depending on the severity of vascular alteration and digital displacement. When there are only a few millimeters of distal L thickening and the case is months since onset, a rocker shoe that produces a 12-15 degree PA is usually adequate to enhance healing. However the case that presents with similar signs that is only a few weeks from onset is treated with high PA enhancement and exercise is restricted. The timeline is very important. Turnout is ok provided the condition is very chronic (months to years) and the horse is not overly active. New horn growth and radiographic evidence of a tighter L zone confirms the efficiency of the shoeing device.
Case 3: Low to mid-scale chronic case
This chronic case presents with the following soft tissue parameters: narrow lucent zone along the endodermal/ectodermal junction, several millimeters of distal displacement (e.g. HL zone 18/25mm), no evidence of vascular damage to the apex and reasonably healthy sole depth of 15-18mm.
Treatment: These cases can also reach full recovery using 12-15 degree PA enhancement shoeing, though some cases may need slightly more mechanics, such as an 18-20 degree self-adjusting PA. Recovery time varies with growth rate, age and breed, but normally the entire capsule will be re-grown in 8-12 months. I like to keep competitive horses out of training for a minimum of a year and a half, preferably two, as this allows the horn to grow out at least twice from the coronary band to ground surface and assures optimum reconditioning and attachment of the endodermal/ectodermal junction. Once full recovery has occurred there are often no gross or radiographic signs of previous laminitis.
Case 4: Mid to high scale chronic damage
In this chronic case the following soft tissue parameters are present: proximal L zone increase of 5-8mm with distal increase of 10-12mm, adequate but not dense and healthy sole depth, a large PA (15-20 degree) unless the heel had recently been taken down, obviously damaged apex and areas of lucency that can be seen radiographically. The growth pattern indicates accelerated heel growth and very slow toe growth. With all chronic cases the club or steeper foot will normally have more damage than the low heel foot. Therefore, this foot can give you more problems, respond slower and often fail to attain the level of healing of the lower profile foot.
Treatment: A venogram may be a deciding factor between shoeing with optimum mechanics or cutting the DDF. Most of these cases will have a well organized lamellar scar that can be seen grossly as well as radiographically. The venogram may reveal a distinct vascular pattern that has been pulled from its ectodermal attachment. There may be some degree of circumflex vessel remaining distal to the apex or it may be prolapsed over the apex.
First consider the goals of the client. When pasture soundness is the goal I would consider derotation shoeing with a tenotomy rail or shoe that offers comparable advantages. Create a zero PA with the foot side of the shoe branches while maintaining a minimum 20mm distance between the palmar rim and shoe. The 3-5 degree wedge in the shoe helps prevent excessive luxation when the DDF is cut and offers better articular alignment. This helps prevent excessive load on the vessels entering the terminal arch. The heel extension component of the shoe prevents toe lift that occurs with a fair number of cases and allows the horse to be bedded in deeper bedding. If the heel extensions are left off, most cases will hyper extend the coffin joint in deep bedding.
Bandages should be worn for 90 days post op. I often let my chronic cases wear the tenotomy shoe for 8-12 weeks provided the length does not pull the foot forward, creating a tip up situation. At this time sole depth should be 15-30mm (depending on the starting point) and the DDF will be securely adhered to the SDF, which allows the foot to be trimmed to a minimum sole depth of 20mm and a 2-3 degree PA when possible, and left barefoot. Toughen the foot with a propane torch and Keratex hardner or apply a bandage or a boot for a few days until the foot gets into a tougher mode. These cases do well barefoot provided there is adequate mass.
This case may also respond well to an 18-20 degree PA shoe, however there are pros and cons for either option.
Shoeing
Shoeing requires a farrier with good working knowledge of radiographic information. Sole depth, PA and digital breakover are all very important parameters to be considered when applying a rocker shoe.
The shoes are technique sensitive, therefore knowledge of the degree of mechanics that are required and how to apply the shoes are vital.
Shoeing intervals can vary from 30-60 days but must be consistent.
Radiographic control is necessary for each shoeing. Failure to monitor the efficiency of the mechanics, response, etc. can be very detrimental to a successful outcome.
Therapeutic shoeing with radiographic control is not cheap and requires a substantial investment that should be considered before starting the protocol. There is no cheap shortcut way to push these cases to full or even an acceptable recovery.
Shoeing can offer favorable results, however the results may be a bit slower to attain than with a tenotomy.
Shoeing is recommended over surgery for mares heavy in foal, or mares with young foals that need to go out.
Surgery
Initial investment is greater, but can be more economical long term.
Requires proper shoeing prior to mid-cannon DDF tenotomy.
Surgery can be performed standing with sedation and local block.
Follow up care requires good horsemanship skills, such as bandage changing.
Adequate sole depth can often be obtained in 6-8 weeks.
Case 5: Penetrated chronic case 6-8 weeks to months from onset
In these cases, one or both feet may be penetrated through the sole and the horse will be grade 3/5 lame on a good day. The hoof capsule will be distorted and steadily become more distorted with longevity. Radiographs may reveal evidence of chronic abscesses, especially in the steeper foot, and minimal to moderate bone damage. The HL zone may indicate sinking and rotation that occurred months prior to penetration, and PA may be 10-20 degree, which is higher than normal for the feet presented.
Treatment: These cases all require derotation/DDF tenotomy if you are seeking optimum recovery with minimal damage to PIII and growth centers. Many professionals believe that they can attain pretty good results without cutting as many cases as I do. But how we determine whether or not a case is successful varies greatly. I personally consider cases to be successful when there is no further evidence of the disease, sole depth and PA are easily maintained, growth patterns are compatible with that of a healthy foot and the horse is pasture sound and can be ridden lightly or even go back into full training and slow sports 2-3 years from onset.
Thirty years ago I was satisfied that if a horse remained alive, regardless of how crippled, they were a success and I attempted to reverse the irreversible for months on end. That has all changed with experience and unprecedented numbers of cases. The advent of venogram information and astute observations of small details clearly paved the way to my present and most beneficial treatment protocol. I cannot stress enough that time is of the essence.
Case 6: Very chronic high scale case:
This case may present with extensive hoof capsule distortion and be grade 4/5 lame or reluctant to stand. The HL zone can be off the scale (25/40mm), sole depth may be only a few millimeters, and PA can be 30-40 degree. The horse has a history of chronic abscesses and extensive bone deterioration within the level of the nutrient foramen.
Treatment: This stage of laminitis has short term solutions at best. Most cases are very lame, have evidence of prior or existing body sores and are down more than they are up. They certainly meet the criteria for euthanasia, but with select cases when the owner wants to do everything possible to make the horse comfortable and can financially support all efforts, derotation followed by DDF tenotomy often offers immediate relief for a few months. However, due to extensive bone disease most cases will have recurring DDF contraction, scar contracture and SDF contraction, which can be observed as heel growth rapidly exceeds toe growth, the PA continues to increase and the horse knuckles forward at the fetlock. The fetlock goes forward first due to pain response, but when it remains forward the knuckling becomes more permanent. This stage often follows many of the mid to high scale cases that slowly deteriorate over the years and is normally always associated with the previous, ongoing degenerative bone disease.
Case 7: Advanced stage chronic laminitis
This stage of laminitis will have moderate to extensive bone disease, a large PA, thin sole, large HL zone especially at the distal measurement, upright pastern and knuckling at the fetlock. These cases may have had previous DDF tenotomies several months prior to presentation. The club foot will invariably become upright and knuckled forward some time before the lower heel foot undergoes similar changes.
Treatment: Twenty years ago I thought it best to re-cut the DDF and also the SDF on these cases. However, the end results were often very disappointing. When both tendons are surgically severed, the suspensory is the only support to the fetlock and the sesamoids are very fragile due to months to years of non-use. The upright pastern does not allow suspensory loading, therefore the sesamoids lose strength and often fracture once the DDF and SDF are severed. Even when using a sling to control load and a cast to prevent hyperextension, bilateral sesamoid fractures are common. They can heal with several months of casting, but unfortunately even when successfully healed the ongoing contraction/contracture phase continues and 6-12 months later many of these cases will once again go upright and knuckle over.
A second option is to use a shoe that satisfies the requirements of the DDF and SDF, which can offer favorable long term results. This shoe is made from flat plate aluminum and has a zero PA with the shoe surface and an identical shod PA as the start model. We are not dropping PA, simply shifting load from the apex to the heel. This shoe also has a toe extension that satisfies the action of the SDF. Extending the toe helps push the fetlock into a better flexed position. This can only occur if DDF tension is adequately reduced. Applying a bandage with a cast that extends from the heel bulb to the carpus is also helpful. Once the cast has been on for 4-6 weeks, a half cast along the posterior side of the limb is used for another 4-6 weeks. At this time there should be adequate sole growth and 5-10 degree extension through the fetlock joint. I have maintained several cases for many, many years using this type of shoe and cast combination.
Deciding whether to use mechanical shoeing or the surgical option can be difficult for those with limited experience with the many phases of laminitis. As a rule of thumb, the case that is presented with minimal pain in spite of extreme displacement and hoof disfigurement is a shoeing candidate until proven otherwise. On the other hand, the case with unrelenting pain in one foot or all four is normally a surgical candidate even when the parameters are not necessarily off the scale and hoof distortion and bone damage is minimal.
When shoeing the chronic case, strive to use mechanics that greatly reduce breakover (rocker) and also allow the horse to stand with the same PA once shod even though a zero PA has been created between the wings and posterior quarter of the hoof at the heel. The shoe should not reduce the PA with the ground surface, as this defeats the purpose of mechanical shoeing. We are simply shifting load. Taking 10 degree PA away from a foot in an attempt to make it look non-laminitic can be devastating, as the forces at play are greatly increased. Shoeing the chronic case for surgery is a totally different mechanical setup. We want to create a zero PA with the wing and shoe branch at the heel and provide a 3-5 degree wedge to create a slightly positive shod PA. This greatly helps reduce luxation of the coffin joint and helps release load on the terminal arch vessels.
Regardless of whether shoeing or surgery is the best option for your horse, the big message is this: the majority of chronic cases are chronic simply because they have passed the most effective window of response. Most cases do not have to reach this point. Timely, thorough evaluation and efficient emergency treatment at onset coupled with an effective monitoring protocol that can evaluate the horse's progress (or lack thereof) can reverse the forces at play before irreversible damage occurs.
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