Recognizing Various Grades of the Club Foot Syndrome
Written and presented April 2012 by R.F. (Ric) Redden, DVM
To better understand the club foot syndrome, we must be familiar with the mechanical formula and how it greatly influences the various degrees of hoof capsule distortion and bone remodeling associated with this syndrome. There appears to be a direct relationship between the degree of tension increase or contributive force of the DDF muscle and these two very distinct alterations from the normal healthy foot. This paper will describe that relationship and the soft tissue and coffin bone alterations that are found in the four basic categories of club feet.1 These characteristics are unique for each grade, however several variables can influence the stereotype mechanical model.
The Healthy Foot
First let's briefly describe a healthy foot on a light boned breed such as a thoroughbred, quarter horse, Arabian and other similar breeds. A healthy foot will have a relatively constant growth pattern heel vs. toe, especially when left barefoot. This uniform toe to heel growth rate is clearly revealed by the relatively even spaces between the growth rings, which routinely occur approximately every 30 days. Shoeing styles, trim and reset timeframes can alter this natural pattern to some degree, but it remains well within a range that can quickly adjust back to its original pattern. The hoof wall has a relatively straight, linear appearance and the toe angle has a very large range depending on bone angle (BA) and palmar angle (PA), which can also vary considerably. The approximate angle found along the growth rings when the toe and heel grow at a different rate will closely mimic the PA on the foot that has not been trimmed for 30-45 days.
Figure 1A Left: This horse has very healthy, sound feet despite a grade 1 right front club. Figure 1B Right: The right front growth rings indicate a tendency for a negative PA in the right hind due to the club in front.
Figure 1C Left: Radiographs of same horse taken prior to 5 week reset. The left front has 25mm of sole, a 0 PA and a very healthy horn wall.
Figure 1D Right: The right front has approximately 22mm of sole, a positive PA and very healthy horn wall. Note difference in bone angles. Both feet are sound and healthy even though strikingly different.
Sole depth maintains around 15mm plus with a few millimeters of natural cup. This is the goal on trim day. Strong feet and healthy digital cushion go hand in hand - you won't find one without the other. Domestic horses with strong, intact heel tubules will have a positive PA that will fall into a range of 2 to 5°. Contrary to what we have thought in the past, hind feet of light breeds do not have a larger PA or hoof angle than front feet. Observing many foals as they mature, the large majority have a 0° PA behind, which may explain why their heels can quickly crush and a negative PA develops once put into training.
With this very basic description of a healthy foot we can start comparing one foot to another, from horse to horse as well as feet on the same horse. Observing the external characteristics and soft tissue parameters before and after trimming or shoeing helps us better understand the interconnectedness of each component as well as how we can enhance the natural healing mode with shoeing mechanics.
Club syndrome influence on the opposite foot
The foot opposite a club also appears to be greatly influenced by the club syndrome. The hoof capsule silhouette has several distinguishing characteristics that apparently occur due to a significant laxity of DDF muscle tension, which reduces suspension function. In these feet the pastern sits back well away from the face of the dorsal half of the wall but can remain parallel to the face of the body when digital alignment is present. Imagine pushing the pastern forward just above the heel on the club foot. The tension on the DDFT displaces the pastern on the club and the lack of tension on the opposite foot lets it sag, creating the distinct difference. The growth ring pattern on this low foot is often wider at the toe than the heel, indicating the toe is outgrowing the heel. This ratio steadily increases from one shoeing to the next, as blood flow is exceptionally good to the toe but impaired in the heel due to excessive heel load that results from lack of adequate suspension.
Figure 2A: Photo of a hind foot with a negative PA and crushed heel. Note the growth ring pattern, very low heel angle, bull nose and coronary band angle.
Figure 2B: Right of the same foot. Note the negative PA and digital alignment imbalance. Heel tubules on the low profile foot have a very low angle as compared to feet with even growth ring patterns. The ground surface contact point may be folded forward to the widest point of the foot. The bars are very thin and also folded inward with the heel tubules. The frog is very prominent and extends well past the ground surface of the heels and most often hangs out the bottom well below the load surface of the heels in shod feet. The digital cushion, which can be estimated by placing your forefinger on the frog and thumb in the cleft of the heel, is also compressed. Comparing its thickness to that of the club, it is very obvious that the cushion is all but maxed out.
As load is steadily passed to the growth centers the vascular supply is greatly compromised and heel growth shuts down. This can be demonstrated with comparative venograms. As a rule, the higher the scale the greater the imbalance of toe to heel growth on the low profile foot. This DDFT tension laxity closely resembles the relationship of the pastern to the hoof capsule that occurs following a DDFT tenotomy, a procedure that allows the pastern bones to sag, shifting load to the posterior aspect of the coffin joint/navicular area and associated components of the heel.
Figure 3: Left: Estimating depth of heel and digital cushion. Right: Frayed heel tubules are one of the first signs of heel crush.
How does this happen? The physics of the syndrome are very simple and quite clear if we focus on the function of the DDFT. The club foot results from increased DDFT tension and suspension function. The opposite foot apparently has the same degree of hypo-function; lack of suspension allows excessive internal heel loading that quickly surpasses the limitations of cushion load and recall. As the cushion fails the tubules fail, and the capsule quickly alters the natural growth patterns. One component does not fail alone but affects adjoining support structures.
The hind foot on the same side of the horse as the club foot also has distinct characteristics that clearly distinguish it from the opposite hind foot. Even the hind foot that follows a grade 1 club will have a lower profile hoof angle, lower heel and less than healthy digital cushion depth, much like that of the low heel in front. Why this occurs is unknown at this time, but it is the author's hypothesis that both are closely related and the result of the club syndrome.
Radiographic Evaluation
A low beam, soft tissue lateral radiograph taken 4-6 weeks post trim or shoeing is very helpful to evaluate the severity of a club foot and determine optimum management options. Radiographs made shortly after trimming or shoeing often fail to clearly describe the significance of the syndrome as the PA, sole depth, digital breakover and HL zone are usually altered with the trimming process.
Figure 4: Standing the horse on two blocks with the head held straight and low beam penetration can help assure a more accurate radiographic image.
Figure 5: Lateral low beam soft tissue view vs. high beam. Note the lower beam projection reveals one branch of the shoe, which is vital for measuring sole depth and PA.
This protocol allows for accurate evaluation of sole depth and other valuable soft tissue parameters. It is also helpful to see the dermal/epidermal (DE) zone on all lateral soft tissue detail film. This zone describes the horn (H) and laminae (L) and as a rule evenly divides the HL zone. If the H zone appears quite narrow closer to the toe, this indicates that the toe was backed up (rasped off) by the farrier.
Figure 6: Measuring soft tissue parameters on a foot with a positive PA and negative PA.
Radiopaque paste along the face of the foot describes the wall proper, which is not visible on any radiographs without an opaque marker. Contrary to popular belief, digital images do not reveal the outermost layer of the horn wall as this small area is always overexposed. Radiopaque paste also describes growth rings that can provide valuable information. Using a nail, needle or wire only touches the high points and therefore does not reveal the growth rings or the true wall margin.
It is important to note that a common practice is to trim and shape a club foot to make it appear more normal. This practice can drastically alter several key soft tissue parameters, including the horn-lamellar (HL) zone, sole depth and PA, which can cause confusion when evaluating a foot and lead to misinterpretation. The best time to observe the foot's natural characteristics is 4-6 weeks post trim or shoeing.
When interpreting film made shortly after shoeing we must focus on the joint space (lateral view), which in most cases will be very tight along the dorsal aspect and wider along the distal articular zone. This is an indication of increased DDFT tension. Even though PA may be 2 to5° and appear quite healthy, an 8-10° PA will allow for a more even joint space. This is also an indication that increased tension is present due to lowering of the heel, which is a very common practice. The face of the bone of a club foot develops a distinct bulge. The bone shape can also allude to the club foot syndrome even when the foot is freshly shod. In young horses, the distal HL zone is narrower than the proximal measurement.
Foals
In newborn foals, the coffin bone is quite small and has a very distinct shape and the bone and foot grow rapidly in a relatively natural growth plane. Apparently the overall shape of the bone is greatly influenced by the forces exerted by the DDFT, laminae and ground load, all of which directly influence the nutrient supply to the bone and associated components.
Radiographs of foals only a few days old suggest that bone angles certainly do not always match, nor does the overall stereotype shape of the bones match. Feet with higher bone angles are prone to grade 2 or higher clubs, however those with relatively matching bone angles can progress to various grades of club that are noticeable within weeks or months of birth. This syndrome has been previously referred to as an acquired syndrome, however the author is very satisfied that there is enough clinical evidence to support the theory that the club syndrome is congenital with very strong genetic influence.
Figure 7: 3 week old foal with a 60° bone angle (BA).
Note bone angle shape and digital alignment. As the foal grows and attains body weight the forces at play are certainly magnified. When all forces remain within their natural range, a healthy, sound foot as described earlier evolves.
Foals with low grade clubs can escalate to a higher grade, whether due to genetic influence or to increased tension placed on the DDFT by excessive heel lowering. The genetic component seems to have potent influence on the mechanical model of the foot just as it does for other unique characteristics of the individual. When low grade clubs are trimmed or shod in a fashion that increases DDFT tension, they often escalate to a higher grade on the scale due to neuromuscular reflex that is apparently triggered by pain response in the toe area. Simply put, trying to solve the problem of excessive heel growth using the excessive forces that created the problem is often futile and precipitates the common ill effects of the club foot that have been recognized for years. Toe bruising, fragmented terminal laminae, thin soles, lack of toe horn growth and frequently subsequent toe abscesses commonly occur when treatment is designed to eliminate the unique capsular characteristics of the club. Soundness issues frequently plague athletic horses even with lower grade clubs.
Figure 8: Foal with a grade 4 club, fragmenting toe, thin sole and no toe growth. This frequently leads to abscesses and ongoing soundness issues.
Toe abscesses are very common in foals with grade 2 or higher club feet, but can be prevented by monitoring sole and wall junction integrity. Note a seemingly harmless abscess that often breaks at the coronary band can be a precursor to white line disease in the mature foot.
The Mechanics of the Club Foot
Removing the heel from a low grade club with a PA that is 5° greater than the opposite foot may appear to immediately correct the club syndrome. However, the heel grows back in 10-15 days. Why does it regenerate so quickly? This brings us to a very decisive point of understanding mechanics. If the heel were growing and pushing the horse upward, simply removing the heel would be a reliable solution. And if this were the case, the freshly trimmed heel would set firmly on the ground once the excess heel was removed. However, even with lower grade clubs this practice can create a remarkable air gap along the ground surface of the foot from heel to toe. Even when it looks to be loaded, one can often slide a business card under the heel almost through to the toe. This foot is now being loaded over a very small part of the toe as the heel is suspended and unable to share digital load.
Though an inferior check desmotomy is accepted worldwide as a recommended treatment for mid-grade club feet, the theory that the DDFT is the source of the forces that cause the syndrome seems to get lost. Literature continues to teach that regular, proper farrier care is needed to prevent the heel from growing. Unfortunately this concept violates the mechanical principles of the club foot and can set off a cascading series of events that have the potential to haunt the horse throughout its career.
The trigger mechanism of the club syndrome is not known, but it is obvious that whatever it is has a large scale of intensity. Clinical evidence from venograms support the theory that increased suspension forces of the DDFT directly contribute to increased tension and shear on the very elastic laminae and compressive forces of the palmar rim on the sole corium, an easily compressed source of nutrient supply. This domino effect remarkably reduces sole proliferation and sole and toe horn growth. Increased DDFT forces rotate the coffin bone around the articular surface of PII, increasing the PA and internal load on the apex and sole corium as well as additional stress on the distal lamellar attachment and the dorsal face of PIII. As force increases, load on the digital cushion, heel and frog (which are all located below the suspension structures) decreases, resulting in tight, narrow heels; small recessed frog; excessive heel height, etc. These are all typical distinguishing characteristics seen with various grade clubs.
Figure 9: Balance = harmony between suspension and support structures.
Growth rings become remarkably wider at the heel than the toe, clearly demonstrating the imbalance of forces between the DDFT and its opposing antagonist component, the laminae. The laminae directly oppose the force of the DDFT. The wall then receives load from the laminae, which is passed to the toe at ground contact. Therefore the length of digital breakover demands great respect when attempting to relieve DDFT tension. To better understand the potent effects of the DDFT tension, we need only to greatly reduce the forces at play and observe the medical benefits seen as accelerated sole growth, return of healthy papillae (as seen on the venogram), reduced heel growth and increased toe growth. This treatment concept is referred to as reversal therapy. However, positive results require a few weeks as the foot begins to overcome the ill effects of imbalanced DDFT tension. Unfortunately, much of the horse world continues to want immediate results and simply cannot visualize the DDFT as being the seat of hoof and bone distortion.
Grading Club Feet
Redden defined 4 basic categories of club feet based on increasing severity of hoof capsule distortion from grade 1 at the lowest to grade 4 at the highest.1 Radiographic evidence can also be correlated to the various categories. As a rule, the higher the grading scale, the greater the degree of capsule distortion and soft tissue parameter alterations.
Grade 1
Figure 10: Photo and x-ray of grade 1 club foot. Note the linear alignment between pastern and hoof. This is a very healthy, sound foot.
A grade 1 club is often considered to be a healthy, robust foot by most horsemen and professionals. However when we take a closer look at distinct internal as well as external characteristics there is often conclusive evidence that increased suspension force is directly responsible for the subtle but distinct alterations that clearly distinguish it from the opposite foot.
In the foal, the most defining characteristics of the grade 1 club with similar bone angle to the opposite foot are is a hoof angle 5°greater than the opposite foot and greater PA relative to the discrepancy in bone angle. The face of the pastern is pushed dorsally in a straight plane with the face of the hoof and the heel bulb will have a fuller appearance, though this is difficult to detect at a very young age as the foot is smaller than the pastern.
At 6-12 months of age the grade 1 club is quite easy to identify as the features explained above are simply magnified. The PA will be greater, the frog not as well formed as the opposite frog and the heel and foot width will be slightly narrow. Growth rings will be quite uniform or slightly wider at the heel, especially the lateral heel.
A foot that remains a grade 1 club throughout the life of the horse can be easily maintained as long as it is trimmed and/or shod in a fashion that does not drastically reduce PA and thereby increase tension on the DDFT, making it look like the lower profile opposite foot that has a 0° PA and less DDF suspension. The grade 1 club will have a 3 to 5° PA and can maintain 15-20mm of sole on shoeing day. Dropping the PA with every trim to match the opposite foot invariably increases tension on all structures and will slowly remodel the face of PIII, the L zone, sole depth and articular surface.
Grade 2
Figure 11: Photo and x-ray of grade 2 club foot. Note wider growth rings at the heel than the toe and the pastern/toe relationship, The 10° PA is evidence of excessive toe loading, In the radiograph, note debris that has invaded the toe.
A grade 2 club foot is the most common grade and most often missed, as it can appear to be a healthy foot compared to the opposite grade 2 low heel (slam dunk) foot. Grade 1 and grade 2 clubs have a very similar pastern and dorsal hoof capsule alignment. The pastern is displaced dorsally, creating a linear plane along the pastern and face of the hoof capsule. This characteristic can be detected when foals are quite young. The pastern of the opposite foot sits back away from the linear plane along the dorsal face, creating a slight dip just proximal to the coronary band. The heel shape on the club will have fullness between the bulbs with less of a pocket in the space between the heel bulbs. The lateral view profile of the club heel will be more vertical than the opposite heel.
Foals with grade 2 club feet may have a bone angle that is 5-10°greater than the opposite foot. This appears to be unique to the club syndrome as the larger than average bone angle (50 to 51°) has not been documented in the low foot. The apex is always convex in the newborn, but starts to remodel quickly if subjected to excessive internal bending forces. As a yearling the apex will have developed a distinct lip, referred to as a load induced lesion, caused by the unrelenting pressure of the DDF as it presses the apex into the sole corium. Sole depth will be diminished compared to an untrimmed foot that has natural growth. The cup of the foot may be absent radiographically unless the sole has been trimmed by the farrier to remove sole pressure.
The face of the coffin bone will begin to develop a slight bulge along the mid face. Distal to this point the bone will have a dish appearance that increases the distance between the opaque DE zone and the face of the bone. This resorption of bone can be confused with rotation of the coffin bone. Note the parallel arrangement of the bone and wall above the bulge. This differentiates the alterations from capsular rotation, which is caused by loss of horn integrity (white line disease, laminitis or both) and occurs along the entire dorsal face. The resorption or remodeling found in the club foot apparently falls under Wolff's law, which states that bone remodels along lines of stress. This lip of remodeling is also accompanied by a higher PA than we find in the healthy foot described above.
Figure 12: At first glance this foot might appear to have rotation, but note the parallel arrangement between horn wall and proximal face of coffin bone. Distal to the bulge bone remodeling gives the appearance of rotation.
As this foot matures and the forces at play are continually reinforced by traditional heel lowering, the bone continues to remodel along the lines of stress. The lip is resorbed and the palmer surface of the bone is no longer a straight plane. The anterior third of the bone is no longer in line with the wings. This can be considered a load induced lesion and is a typical characteristic of grade 2 club feet.
Before trimming, most all grade 2 club feet will have a 5 to 8° PA and can be as high as 10 to 12°. Even if the heel is removed and the PA is subsequently lowered, it will drift back up over 4-6 weeks. This tells us a lot about the foot. If a foot naturally has an 8 to 10° PA but is maintained at 2 to 3° we know without a doubt that the tension on the DDFT is greatly increased on a regular basis. Every time the heel is taken off load is transferred to the toe.
Sole depth revealed by radiographs may appear to be adequate, however if this foot was shod 6 weeks previously and only 10 to 12mm of sole is present, the foot is not happy. If the foot has 10 to 12mm of sole and had only ben shod a few days, interpretation would be totally different. When a cup is present, consider whether it is natural or manmade. If the foot was shod a few days prior to the x-ray, we can assume it is manmade and have no clue what it was before shoeing. Here lies the value of noting the last trim or shoe date.
Figure 13: This foot has very thin sole and fragmented walls despite being reset several weeks ago, indicating the mechanics are not complimenting circulation to the growth centers.
The average grade 2 club often presents to the author 4-6 weeks post shoeing with a history of off and on lameness grade 1-2 out of 5, especially on hard or firm surface. Growth is very limited with the exception of the heels. Several sets of nail holes may be present very close together. The walls have become more fragmented and it is obvious the farrier is running out of horn for a good nail as the growth supply isn't replacing the old nail holes.
Grade 3
Figure 14: Photo and x-ray of grade 3 club foot shod with a positive pressure frog plate and rocker rail to self-maintain the exceptionally high PA, all the while
drastically reducing DDFT tension.
The foal with a grade 3 club foot is normally born with DDFT contraction syndrome, with one foot contracted more than the other. Some may even have contraction through the fetlock and/or carpus. Several treatment options can successfully manage the congenital contraction stage in a large majority of cases, however in some cases the heel remains suspended regardless of the treatment and favorable results on the carpus and fetlock. These feet will likely develop into grade 3 or possibly a grade 4 club feet as they mature.
The overall hoof and heel shape will be much narrower on grade 3 club feet compared to the opposite foot. The frog often sits deep within the foot. Internally the PA can be as much as 8 to 10° degrees with the hoof and 20 to 30° with the ground before trimming. Bone angle can be considerably greater on grade 3 clubs; it is not unusual to find a 60° BA on these feet. To determine whether the club syndrome creates the higher BA or the other way around, coffin bone development in a large population of cases needs to be documented.
The apex will develop a lip within weeks from birth, especially if efforts are made to reduce heel growth, as this automatically increases apex bending forces. The hoof capsule starts to dish due to the same forces and the more often heel is removed, the greater the dish. Farriers routinely remove the dish once it forms, but it soon returns as the foot is now weaker and more vulnerable to internal forces. This is where we must stop and ask why the dish and excessive heel growth is always there even when both are taken off every few weeks.
Grade 4
Figure 15: Photo and x-ray of a grade 4 club foot. Note heel length is almost equal to toe length. There is extensive bone remodeling, which is characteristic of most grade 4 club feet.
Capsular characteristics of grade 3 and 4 club feet are not present at birth, however the author strongly believes the syndrome is congenital in nature and the higher grades are a reflection of ever increasing DDF muscle contraction syndrome. These grades develop with maturity and consistent, unrelenting tension of the DDFT. A weanling with a grade 4 club will have very notable DDFT contraction with little evidence of toe growth and excessive heel growth. The dorsal hoof wall will form an angle of 80 to 90° with the ground surface of the heel.
The bone remodels quickly and shows signs of extensive bone resorption and remodeling, often appearing as a rounded off, very misshapen surface, indicating a large area of apex has been resorbed. The face of the bone takes on a very distinct bulge much like the grade 3. The distal half of the dorsal face will be well resorbed, creating a much wider L zone than even the grade 3 club foot. PA can range from 10 to 20° within the capsule and is often 30 to 40° in the mature foot.
This is the grade that everyone identifies as a club foot as the alterations are so distinct and far removed from that of the opposite foot. Many of these feet have already had several abscesses along the toe, breaking at the coronary band. Most mature animals will have a full thickness toe crack that develops along the scar, created by migrating abscesses that break at the coronary band.
Treatment:
The club foot syndrome essentially cannot be cured. Therefore the goal is to manage the syndrome. This can best be achieved by greatly decreasing DDFT tension. Because the severity of contraction varies greatly, the level of mechanics needed to offset the imbalance between suspension and heel load is relative to needs of the individual foot. Best results are obtained with young foals, especially with lower grades. However it can also be quite helpful in managing mature horses. My management goals are to significantly reduce the forces of the DDFT in an effort to reduce the severity of capsule distortion. I like to see grade 2 cases appear to be grade 1 and grade 3 and 4 cases as grade 2.
There are several ways to reduce DDFT tension.
Extend heel length. Push the heel back to solid tubules at the longest length possible (the widest point of the frog) in the same plane as the PA, not from the toe as is required for all flat shoeing. Note the landmarks at the frog/skin junction. Visualize a line passing through this point to the apex of the frog. This is the plane of the PA.
Reduce breakover. Backing the toe up has been mentioned and can be helpful, but only on a very small scale as the toe can only be backed up a few millimeters before we are inside the wall, as evidenced by the light yellow color of the distal end. However, using a shoe to greatly enhance breakover lets us leave the toe and bring breakover back 2-3 inches or whatever is needed to place it directly under the center of articulation. First, significantly increase heel tubule support length by creating a 0° PA between the wings of the coffin bone and the shoe surface at the heel. Then rocker the shoe, starting at the heel and working the radius forward. This will increase heel load and maintain original static PA with the ground. The mechanics of this shoe lie in the airspace from breakover to the toe. There is little or no tension on the DDFT as there is no opposing ground force from heel to the center of pivot of the shoe.
Shorten the distance between the origin and insertion of the muscle tendon unit. A variety of wedges, shoes and trim styles can effectively raise the heel to accomplish this. However the increased PA is not self-adjusting, and even if it meets the goals of decreasing DDFT tension, heel crushing is inevitable. Many variables can influence the effectiveness of this method.
A grade 2 club with a 50° bone angle and 8° PA has a 58° hoof angle, which is 8 to 10° greater than the opposite foot, which has a 50° BA and 0° PA. Raising the heel of this foot by 5° increases the hoof angle to 63°, which reduces the tension on the DDFT to some degree. However the positive effects are limited due to the pre-existing high internal PA. Blood supply to the apex remains compromised as load has not shifted to the heel zone. Therefore to optimally shift load away from the apex and to the heel we need to incorporate all three mechanical methods: creating a 0° PA with maximum heel length; greatly reducing breakover by placing the belly of the shoe under the center of articulation and raising PA with the ground to shorten the length between origin and insertion of the DDFT. This establishes the mechanics for a self-adjusting PA. The horse can shorten the musculotendinous unit at will and with ease. Thus these mechanical properties complement each other. When all principles are followed the horse cannot rock back, which is very important.
Pushing the heels back to the widest point of the frog and bringing the breakover back (not the wall) the same amount is often sufficient to maintain a low grade club. Both techniques reduce DDFT tension, and used together they can be highly effective to manage grade 1 club feet in foals, weanlings and adults. Many foals with grade 1 club feet can be managed very successfully as they mature with an easy four point trim.
Figure 16: Low grade club foot with a four point trim. Note breakover is pushed back almost to the apex of the frog. Heels are pushed back to the widest point of the frog but in a totally different plane. The sole along the trim plane should be perfectly flat - no crown.
Higher grades, such as grade 2, require more mechanics (higher PA) to offset the adverse effects of increased DDFT tension because there is more tension involved. Start by backing the heels up to the widest point of the frog (solid tubules) in a plane with the palmar wing using external landmarks. Be conservative and leave as much foot as possible while achieving the desired mechanics.
Figure 17: Before and after radiographs of the same foot. Note area of breakover and the fact that 20mm of sole remains after the trim.
As you rocker the toe of the foot with the rasp, make sure it is in a flat plane across the sole forward of the location of the apex of PIII and perpendicular to the frog. There is very little sole at this point. Rasp breakover forward of the apex to prevent loss of sole depth under the apex. The author prefers a shoe that has mechanics on the ground surface, e.g. Nanric Rocker Race, Nanric Full Rocker or Nanric Rail shoeA, which are rockered to offer even more mechanics for most all cases.
When rockering the shoe, start at the heel, making certain the breakover point of the shoe is closer to the heel than the toe. This will allow you to set the heels to the trimmed heel tubules. There is no reason to bring the shoe back farther than the trimmed tubules at the base of the frog. When the shoe is placed on the foot, the peak of the belly will be at the widest point of foot. Higher grade clubs may require the point of pivot to be slightly forward of the widest point of the foot. Be careful not to just bend the shoe; it should be a gentle, smooth radius from toe to heel, foot side as well as ground side, with no flat places on either surface. Radiographically this will be directly beneath the articular surface of PII. The PA is self-adjusting when the belly of the shoe is right and there is no resistance of the toe against the DDF muscle. Shoes can be glued on foals with Equilox, however caution should be taken to cover any and all small separations in the terminal laminae with wax or composite product to prevent sealing up bacteria that can create potential abscesses.
Within 30 days, radiographs should reveal double or often triple sole growth, especially in young foals. Horn growth will likewise have approximately the same growth rate response and PA should hold, meaning it remains at or close to zero with the heel branch of the shoe just as it was when the foot was shod. When PA holds it means the mechanics are adequate to balance the force of the tendon with other support components. When this occurs the vascular supply is mechanically uninhibited, enhancing nutrient supply to the solar papillae and primary horn papillae. As a result growth rings at the coronary band will be equal from heel to toe.
Figure 18: Radiographs of a foal with a grade 3 club. Note the increased sole growth after only 5 weeks shod with a Nanric Rocker Race shoe.
Most young cases will require 2-3 resets using this concept before they can be weaned out of the shoe and into a 4 point trim that also should maintain optimum sole depth. Remember if the sole is not growing 5-10mm per month the vascular supply is mechanically inhibited. If sole depth diminishes and/or PA increases, go back to the higher mechanics of the rocker shoe.
Using the reversal therapy concept to balance heel/toe growth produces exceptionally thick soles and good, strong walls. Relieving internal DDFT tension also preserves the integrity of the apex and palmar rim, which is essential for athletic potential. However the foot will always be narrower than the opposite foot and possess the subtle signs a club foot even if it is managed as a lower grade. We do not cure it, we manage it.
Surgery
When shoeing mechanics have failed to suppress excessive heel growth and promote sole growth, it is time to consider surgical options. Surgically lengthening the musculotendinous unit can be accomplished several ways.
Inferior check desmotomy: This method has been advocated as an efficient means treating club feet for many years. The author's approach to when, how and why to use this method can help overcome several problems that can potentially interfere with a positive outcome. Factors to consider when considering surgery include:
Age. Foals 4-8 months of age appear to be most responsive to surgery and as a rule experience less scar formation than yearlings and more mature horses.
Severity of contraction. Surgically cutting the check allows approximately 15° of PA decrease. For higher grades, this may not be sufficient.
Bone angle. Bone angle, which can be measured from low beam lateral radiographs, should be taken into consideration. The bone angle in a club foot can be several degrees higher than the opposite foot and adds to the overall hoof angle. If the bone angle is 8 to 10° larger than the opposite foot and the PA is only 5°, the best improvement in hoof angle we can achieve by cutting the check is 5°. The bone angle will keep the hoof angle a good 10 to 15° greater than the opposite foot and minimal cosmetic or medical benefits have been achieved.
Most grade 2 and low to mid-grade 3 club feet will show a favorable response to an inferior check desmotomy provided all other variables, including foot stereotype, chronicity, degree of internal surgical gap and follow up care are taken into consideration.
Shoeing: Preparing the foot for optimum surgical gapping is of utmost importance. Dr. Redden prefers to create a 0° PA and maintain a minimum of 15 to 20mm of foot mass between the palmar rim and shoe. Farriers need to work from radiographs to appreciate the small but essential details as the foot is trimmed and shoe secured to the foot. Shoeing prior to surgery prevents unwarranted bruising of the surgical area. When shod after surgery, the farrier's knees can cause unwarranted pressure, bruising and bandage slip.
Often there is not enough heel, not enough sole or both to reduce PA to 0°. In order to do so, draw a line on a lateral radiograph parallel to the palmar rim (along the straight part of the wings) and another 15 to 20mm below the palmar rim. This is the trim line. The goal is to preserve as much foot as possible yet establish a 0° PA, which produces optimum surgical gap. The larger the gap between the ends of the cut tendon, the more favorable and lasting the results.
Figure 19: Shoe applied pre-surgery creates 0° PA. Heel raise is made with ACSB to facilitate standing surgery when elected and also to reduce unwarranted soft tissue damage by allowing gradual PA reduction.
Performing the surgery: Literature has previously described the procedure as the open method in the proximal cannon or with a bistoury using ultrasound control, both performed under general anesthesia.2 However the surgical site invariably results in remarkable scar tissue whether performed from the lateral or medial side.
The author prefers to cut the tail of the check mid-cannon as it is an easy procedure that can be performed on the standing horse using sedation and local anesthesia. A post-surgical compression bandage adequately protects the mid-cannon site, as opposed to a proximal incision surgery site that is barely covered by the bandage, which often slips or is pushed down by the foal, exposing the incision and creating unwarranted swelling and scar. Cutting the tail of the check appears to produce less serum leakage, apparently due to the denser, fibrous nature of the ligament at its insertion. The check ligament insertion with the DDFT varies greatly from horse to horse and can be isolated mid-cannon in most all horses.
Weaning the PA down: Suddenly dropping a PA to 0° often elicits a painful response as several other adjacent components are forced into a drastically different plane of load and support, particularly the supporting ligament to the navicular bone. Note the close proximity of the navicular bone to the proximal border of the second phalanx before surgery and the significant distance after surgery. Placing a large 20° custom made rubber wedge (ACSB or similar rubber mix) under the foot prior to surgery greatly reduces tension on the DDFT, which offers easy check isolation from the DDFT, prevents unwarranted ill effects of loading a zero PA before the check is cut and offers an easy letdown protocol that prevents unwarranted pain and damage to soft tissues.
Aftercare: Strict stall rest for 30-45 days; hand walking for another 45-60, bandaging changes every 7-10 days for 60-90 days offers best cosmetic results. Reset the shoe in 30-40 days and evaluate PA. It should continue to be 0 to a few degrees positive if the surgical gap was long enough.
DDFT Tenotomy: The majority of grade 4 club feet require complete release of DDFT tension, which can be achieved by surgically severing the DDFT. Choosing the surgical site is an important consideration for several reasons.
Proximal to the check: Cutting the DDFT proximal to the attachment of the check lengthens the musculotendinous unit slightly farther than cutting the check and can be an effective approach for the high grade 3 and low grade 4 club feet. The procedure can be easily performed in the standing horse using sedation and local anesthesia. As a rule this approach produces minimal scar and reduces PA approximately 15 to 20°, therefore shifting the grade 4 club to a more manageable grade 2 that can better serve the athletic potential of the individual.
Mid-cannon: The mid-cannon tenotomy is quite easy to perform standing. Shoeing the foot prior to surgery to create a 0° PA with the shoe produces the best results. The shoe needs slight toe extension to assure the largest tendon gap and heel extension to prevent luxation of the coffin bone and toe lift for the first 30 to 45 days following surgery. Note the shoe is set to the foot using composite such as Equilox parallel to the palmar rim with 20mm of space between the shoe and palmar rim. Leave all the foot mass possible as the heel carries load when the DDFT is severed and needs mass to withstand the increased load. Cutting the deep in lieu of creating a 0° PA can produce disappointing results as the coffin bone remains trapped in the contracted position within the capsule, thereby preventing decompression of the sole corium and apex and the desired load shift to the heel.
Mid pastern: This site is at the distal end of the musculotendinous unit and should be reserved for the very last resort if and when the contraction phase exceeds the ability of the more proximal surgical procedures. Once this area has developed the typical post-surgical scar, cutting above has little or no mechanical advantage.
There are several pitfalls that can reduce the effectiveness of the surgical approach, such as failure to realign the palmar rim with the shoe surface (0° PA), removing far too much heel in an effort to set the shoe on the entire foot and excessive joint luxation due to lack of adequate heel support. A bistoury seldom if ever cuts through the entire tendon and most often does not cut the check fibers. When the bistoury cuts the taut, main body of the tendon it will pop, form a gap and make you believe it is cut through and through. Make an incision, take a look or feel the tissue that remains intact. This approach can cause extensive swelling and unwarranted post op pain.
Young foals 4-8 months of age can have an athletic career barring any and all unforeseen setbacks. Older horses heal slower and require a larger recovery period, and can have quality lives as brood stock and/or perform light work.
Using simple mechanics that can be designed with a variety of shoes we can tweak the mechanics to meet the requirements of the foot. Reading the growth rings, sole response and soft tissue parameters we can successfully manage a large number of feet that fall within the grade 2-3 range. Let's forget once and for all about matching toe angles and focus on maintaining toe growth, sole growth and suppressing heel growth.
Redden RF. How to Treat Club Feet and Closely Related Deep Flexor Contracture. In Proceedings, 16th Annual Bluegrass Laminitis Symposium, 2003 - Louisville, KY.
Waguespack RW, Caldwell F. How to Perform a Modified Standing Deep Digital Flexor Tenotomy at the Level of the Proximal Interphalangeal Joint, in Proceedings, 55th Annual Convention, Am Assoc. of Equine Prac. 230-237.
A. Nanric Rocker Race, Nanric Full Rocker, Nanric Rail shoe are manufactured by Nanric, Inc., Lawrenceburg, KY. B. Advance Cushion SupportTM, manufactured by Nanric, Inc., Lawrenceburg, KY.