Coffin bone rotation and Sinking in a donkey.

Sadly, I share the story of my very own donkey named "Lollipop". She is approximately 12 years old and every summer gets a bit foot sore when the green grass is lush. Through benign neglect and some luck, she has recovered every year with just a few days of phenylbutazone treatment! This year has been different. She has been lame in left front foot for over 2 months. Initially, she was lame in both front feet and I kept her feet supported with impression material and bandages. After 30 days of foot bandages, I switched to Soft Ride boots with removable orthotics designed for acutely foundered horses. The donkey remained lame in the left front foot hence I broke down and radiographed both front feet. On the day that the radiographs were taken, I noted that the entire coronary band was soft and painful in the left front foot!!
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Figure 1

Figure 2

.Figure 1 is a radiographs of the left front foot and Figure 2 is of the right front foot. There is evidence of chronic laminitis in both front feet with coffin bone rotation and pedal bone lysis. However, the most concerning observation was the radiographic evidence of coffin bone "sinking", predominantly in the left front foot. This occurs when the lamina becomes detached all the way around the foot and can result in the entire hoof sloughing off the foot!! In Figure 3 and 4, the red line corresponds to the coronary band and the blue arrow is the distance from the coronary band to the coffin joint. In Figure 3 (left front foot), the blue arrow is longer than the blue arrow in Figure 4. This would suggest that the entire bony column has "sunk" into the hoof capsule. This would also explain why the coronary band was soft and painful. In essence, Lollipop is trying to lose her hoof!  If this was to happen she would likely require humane euthanasia!!

Figure 3

 

Figure 4

Due to the severity of her condition, she is now locked up in a stall and I have placed her left front foot in a cast. The cast will hopefully stabilize the foot/hoof and allow time for healing of the lamina. She is comfortable on 1/2 gram of phenylbutazone 2x per day and other than being annoyed about the stall confinement, she appears stable. Stay tuned and keep her in your thoughts and prayers!!

Foundered Horse with Inadequate Shoeing!

A 10 year-old Arabian cross gelding presented for shifting foot lameness and pounding digital pulses. There was no history of laminitis/founder. The horse was not willing to walk on concrete and was a grade 3/5 lame in both front feet on soft ground. Physical exam noted a prominent fat pad over the tail head and the development of a cresty neck! A radiographic exam was performed on both front feet to determine the severity of the gelding's condition.

Figure 1

Figures 1-3 correspond to the lateral projection of the right front limb. There is a clear explanation for the shifting leg lameness and pounding digital pulses. In Figure 2, the yellow dotted lines correspond to the dorsal hoof wall and the dorsal border of the coffin bone. In a normal horse, these two lines are parallel. However, in the case of laminitis/founder with coffin bone rotation the yellow lines are NOT parallel. The small blue triangles labelled A and B correspond to the angles of the yellow lines with the horizon (red line). In this horse, angle A does NOT equal angle B. These findings confirm the diagnosis of laminitis with coffin bone rotation. The difference between angle A and B corresponds to the degrees of coffin bone rotation and in this case that number was 10-12 degrees. The left front limb was similar.

Figure 2

In addition, the gelding's cranial to caudal balance is extremely poor. The yellow line in Figure 3 corresponds to the "center of rotation" and in a normal horse should divide the foot evenly in half. As such, there should be equal amount of ground contact (red lines) in front of the yellow line (cranial) and behind the yellow line (caudal). In this horse, the amount of ground contact behind the yellow line is nearly zero compared to that in front of the yellow line. This is due in part to the extremely long "toe" and the shoe placement. The extremely long toe and cranial shoe placement adds significant leverage on the toe which will aggravate the laminitis and increase the horse's level of pain!. Initial management of this case involved removing the shoes and significantly reducing the length of the toe. In addition, a blood sample was tested for insulin resistance and the horse was confirmed to be suffering from insulin resistance secondary to metabolic syndrome. The gelding was treated with the appropriate diet, stall confinement, pain medication, and medical management for insulin resistance. Stay tuned for follow-up.....

Figure 3

Sub-solar Abscess in a Horse!!

Figure 1

The radiograph in Figure 1 is of a horse's hind foot. This gelding has been suffering from chronic laminitis/founder for over 1 year. When I first examined this horse, there was nearly zero sole depth between the coffin bone and the bottom of the foot. In addition, the coffin bone was reduced in size due to gradual degradation (pedal osteitis) of the coffin bone. The pedal osteitis developed due to the chronic pedal bone rotation that is evident in Figure 2 (non-parallel red lines). It was decided that a deep digital flexor tenotomy combined with appropriate shoeing may help stabilize the foot and promote sole growth. Over 4-6 months after the surgery, the gelding's sole depth increased significantly, indicating normal hoof growth and he was more comfortable on this limb.

Figure 2

Recently, the gelding's lameness worsened and he was non-weight bearing when examined. A lateral radiograph was performed (Figure 1-3). A large, radiolucent area (red circle) was noted in the toe region of the foot with a track that appeared to be traveling toward the coronary band (Figure 3). These findings are consistent with a large, sub-solar abscess! 

Figure 3

The shoe was removed and a large "hole" was noted at the apex of the frog that extended into a cavity with the circumference of a golf ball! The abscess appeared to be draining however it involved a significant amount of space between the bottom of the sole and the coffin bone. After removing the shoe, the foot was soaked in a warm epsom salt solution and then was "packed" with a strong disinfectant. The gelding's lameness improved within 24 hrs however he remains lame at the walk. His return to soundness will take some time and most likely require a specialized shoe known as a hospital plate. Recurrent foot abscess formation is a common problem among chronically foundered horses and highlights the importance of regular trimming/shoeing plus radiographic examination!

Figure 4

White Line Disease and Laminitis in a Horse!

Figure 1

 The radiograph in Figure 1 is that of a middle-aged gelding that presented for intermittent foot pain. One year prior, the gelding had developed a high fever of unknown origin (presumed viral). During the weeks that followed the high fever, the gelding was slow to walk in small circle and on concrete surfaces. Over several months, the gelding's lameness improved however he was consistently tender immediately after being trimmed by the farrier.  There are 2 disease processes identifiable in Figure 1. The first is chronic laminitis or founder.

Figure 2

 In Figure 2, the yellow lines correspond to the dorsal hoof wall and the dorsal aspect of the coffin bone. Normally, these lines are parallel to each other such that a horizontal line drawn across them would yield equal angles (angle A and angle B). However, when the coffin bone has "rotated" from its axis then the angles will differ as they do in Figure 2. Hence, the radiographic finding is consistent with laminitis (founder) and subsequent coffin bone rotation. This condition appears to be chronic, evidenced by the "flaring" of the tip of the coffin bone seen in the blue circle in Figure 3. This flaring often corresponds to small fractures of the tip of the coffin bone secondary to increase concussive forces over the toe region of the foot. The red arrow highlights the extremely thin sole which measured less than 5 mm!  Ideally, the sole depth at the tip of the coffin bone should measure between 10-15 mm in thickness.

Figure 3

 The second disease process noted in these radiographs is White Line Disease. This is evidence by the gas lucency traveling up the dorsal hoof wall (yellow arrows in Figure 4). The lateral radiograph is only 2 dimensional hence it is impossible to predict if this gas lucency is right down the middle of the hoof or if it wraps around the medial and lateral aspect of the hoof. Regardless, the gas lucency corresponds to separation of the hoof wall from the underlying tissue. White line disease may be the primary problem or secondary. In this case, it is likely secondary to the chronic founder/laminits however in primary cases, it can cause coffin bone rotation and result in laminitis. This condition results from the accumulation of dead/decaying material that slowly works its way from the sole surface up the hoof wall. The offending organism is believed to be in part anaerobic bacteria that thrive in a low-oxygen environment and produce gas that can be seen on a radiograph. Excessive gas accumulation may result in hoof wall separation from the coffin bone and coffin bone rotation.  Treatment involves aggressive removal (hoof wall resection) of ALL dead and decaying hoof wall to expose the offending organisms. Hoof wall resection along is very effective in treating this condition but it is typically paired with soaking the foot after resection in a variety of solutions to kill off the offending organisms.

Figure 4

Often, the early signs of white line disease can be detected at the time of hoof trimming and appear as a shallow crack at the toe region. The opposite foot of this horse had the very beginnings of white line disease evidenced by a small amount of gas lucency noted at the very tip of the hoof (Figure 5). When identified at this early stage, the condition is easily managed with regular balanced 4-pt trimmings by the farrier. Successful  management of white line disease is best accomplished through a farrier-veterinarian team effort. The farrier is the most important part of the team since they will be doing 99% of the work. The veterinarian will provide the radiographic studies to verify that adequate exposure of the diseased foot is accomplished.

Figure 5

Coffin Bone De-Rotation!!

Approximately 6 weeks ago, a middle aged mare presented for chronic founder and non-weight bearing lameness. At presentation, there was significant rotation of the coffin bone in the lame foot (greater than 15 degrees) and reduction in the sole depth at the toe region (Figure 1-3). Due to the severe degree of coffin bone rotation and lameness it was determined that transection of the deep digital flexor tendon was the best option for the mare. The procedure was performed at the barn with sedation and a regional block.

Figure 1

Figure 2

Figure 3

In addition to transection of the deep digital flexor tendon, corrective shoeing was achieved by an expert farrier who specializes in foundered horses  (Sir Adam Whitehead). Corrective shoeing is as important if not MORE important than the surgical procedure and without it the procedure could not be a success! The mare's lameness has slowly improved over the past 4 weeks and follow up radiographs revealed complete DE-ROTATION of the coffin bone (Figure 4).  The palmar angle (blue line) is now approximately zero degrees with respect to the horizon and there has been a moderate increase in the sole depth at the toe region (yellow arrow).

Figure 4

In my experience, horses coffin bone rotation that exceeds 15 degrees benefit greatly from this procedure. Typically, these horses require 4-6 months from time of surgery before they are barefoot and sound in the pasture. This mare's initial recovery was slowed due to a sub-solar abscess that involved her entire sole and communicated with the coronary band. 

Laminitis in a horse!!

 The following radiographs are from a gelding that has been lame for nearly 1 year. The gelding has been treated for laminitis/founder and despite efforts by the farrier and veterinarian, the gelding's conditions has worsened. He is non-weight bearing on one forelimb at the time of my exam. The right front foot is imaged in Figure 1 and the left front foot in Figure 2. In Figures 3 and 4 the palmar angle (angle "A") is measured in both front feet. The palmar angle corresponds to the angle that the bottom or palmar surface of the coffin bone makes with the horizon. In both front feet, the palmar angle measures approximate +23-25 degrees. Normally, the palmar angle may range between zero to +5 degrees. Abnormal palmar angles may be negative or greater than +7-8 degrees. However, even though the right and left front feet share the same palmar angle, it is for two very different reasons!

Figure 1 (Right front)

Figure 2 (Left front)

Figure 3 (Right front)

Figure 4 (Right front)

The most likely causes for an increased palmar angle include coffin bone rotation and coffin joint contracture. The difference between these two conditions is key to making the correct diagnosis. In the case of laminitis, the coffin bone rotates under the influence of the deep digital flexor tendon and due to a lack of attachment between the coffin bone and the lamina (i.e. laminitis). In Figure 5, the degree of coffin bone "rotation" is estimated based on the difference between angles "A" and "B". Normally, the hoof wall (red line over "A")  is parallel with the coffin bone (red line over "B"). When these two lines are parallel, the angles equal each other and there is zero degrees of coffin bone rotation. Therefore, the problem with the left front limb in Figure 5 is laminitis and secondary coffin bone rotation.

Figure 5 (Left front)

The right front foot has zero degrees of coffin bone rotation however the palmar angle is the same as in the left front foot. This due to coffin joint contracture and is the definition of a "Club foot". In Figure 6, the lines corresponding to the hoof wall and coffin bone are parallel and as such angle  "A" equals angle "B". Figure 7 diagrams the concept of coffin joint contracture that results in an angle of contracture (angle "A"). Typically, a club foot or coffin joint contracture does not result in non-weight bearing lameness but rather a life long commitment to proper shoeing and trimming. In this case, first glance of the radiographs might be deceiving because both front feet have an abnormal palmar angle, but it is the left front foot with the coffin bone rotation and life threatening laminitis! The deep digital flexor tendon was transected in the left front limb and follow-up radiographs will follow!
To be continued......

Figure 6 (Right front)

Figure 7 (Right front)

Venogram!

As discussed in last week's "pic of the week", laminitis or founder is a serious condition in horses that requires aggressive and frequent intervention by a veterinarian-farrier team. The radiographs below are those of a quarter horse gelding with moderate founder and approximately 10 degrees of coffin bone rotation. Although the gelding appears stable, he continues to be lame in the affected foot. Routine radiographic evaluation confirms that there has been no further rotation of the coffin bone but does not explain why the horse remains lame. 

The radiographs below are of the same horse AFTER injecting a radiopaque dye into one of the veins that removes blood from the equine foot. A tourniquet is applied at the level of the fetlock before the injection and this allows for the dye to pool within the venous vasculature. Radiographs are taken immediately after the injection and the current blood supply to the foot can be assessed. 

Careful evaluation of the above image suggests that the horse has adequate blood supply to the entire foot. This is evident by the extensive venous supply (white squiggly lines) that originate near the coronary band and essentially surround the entire foot. However, when the foot was imaged in a dorsal-palmar view (below), there appears to be a decline in blood supply to the inside of the foot versus the outside. The yellow arrows are pointing to the areas in question. Note the subjective decline in blood supply along the right side (inside) compared to the left side (outside)

Although these observations are not 100% definitive, they do suggest a reduction in blood supply to the medial aspect of the hoof. This information is important when considering the horses's prognosis and shoeing recommendations. Venograms can be easily performed in a stall-side setting but do require digital radiography and knowledge regarding the technique. The information gathered from these studies is considered an important piece of the puzzle regarding management of laminitis in the horse.

Founder!

The images below are of those of a horse with chronic "founder" or laminitis. There has been significant deterioration of the coffin bone and severe distortion of the hoof wall capsule. Clearly, there has not been adequate care of this horse's feet by a farrier/veterinarian team. Chronic founder requires careful attention and care by a veterinarian AND a farrier. The changes in coffin bone alignment must be monitored via radiographs and corrective shoeing by the farrier is critical to reduce pain and further deterioration of the foot. 

The images below are of a different horse with chronic founder that resulted in the coffin bone rotating out the bottom of the foot. Unfortunately, this is the end of the road for this horse and his condition resulted in humane euthanasia. This end result can often be avoided however sometimes despite the most attentive veterinarian/farrier team, mother nature has the last say in the matter. 

This post will be the first of several discussing chronic laminitis/founder, so stay tuned!!!