Chronic Foot Abscess in a Horse

A fifteen year old gelding presented to PHD veterinary services for the complaint of recurrent foot abscesses. Over the past 2 months, the gelding has suffered from 2 abscesses in the same foot. Physical exam revealed a draining abscess from the outside (lateral) margin of the sole and the horse was lame at the walk. A radiographic study of the foot was performed. In Figure 1, the lateral view of the foot is represented. There is no evidence of laminitis and there appears to be adequate sole depth (>1cm). However, careful examination of the palmar (bottom) portion of the coffin bone revealed an area of radiolucency in the bone (yellow circle and yellow arrows).

Figure 1

In Figure 2, the same radiolucency can be seen in the outside (lateral) portion of the coffin bone (yellow arrows and circle) AND is associated with the radiolucency (blue arrows)  immediately below it which is the current abscess that is draining from the bottom of the foot.

Figure 2

In Figure 3, the downwardly projected radiograph clearly identifies the defect within the coffin bone (yellow arrow and yellow circle).  In addition, the full extent of the abscess is noted by the blue arrows which nearly encompass the entire lateral aspect of the sole. The "black hole" noted inside the yellow circle corresponds to a region of the coffin bone which as been invaded by infection or possibly a tumor. The most likely scenario is a chronic abscess which has resulted in osteomyelitis (bone infection) of the coffin bone. Further diagnosis and treatment will involve a veterinary surgeon and exploration of the coffin bone defect. 

Figure 3

 Typically, foot abscesses do NOT result in a bone infection. However, if the initial abscess is not treated aggressively with disinfecting foot soaking and proper bandaging, it is possible to have such a complication. I typically recommend 7 days of epsom salt solution soaking along with bandaging the foot with a variety of "packing" material. In the case of large sub-solar abscesses, I strongly recommend the use of a hospital plate or specialized boot.

Keratoma in a horse!!

A 10 year-old gelding presented to PHD veterinary services for a history of recurrent abscesses in the left front foot. Over a period of 6 months, the gelding developed 3 distinct abscesses which ruptured at the coronary band. At presentation the gelding was mildly lame and there was no active drainage from the most recent abscess rupture. A radiographic exam was performed to determine if there was a radiographic explanation for the development of multiple foot abscesses in the same foot.

Figure 1

The most notable finding in the radiographic exam was evidence of coffin bone rotation (Figure 1 and 2). In Figure 2, the red dotted lines should be parallel. The red line on the left corresponds to the dorsal hoof wall and the red line on the right corresponds to the dorsal aspect of the coffin bone. The reason they are not parallel is because the red line on the right has rotated in a down ward direction approximately 10-12 degrees. Evidence of coffin bone rotation suggests a history of laminitis or founder and this might explain the recurring foot abscesses. In addition, the yellow lines in Figure 1 highlight the hoof wall defect which developed secondary to the recurrent foot abscesses. There are thin areas that appear radiolucent (black lines) which extend from the dorsal hoof wall defect (yellow lines) down towards the bottom of the foot. These radiolucent lines may correspond to remnants of draining tracts from the recent abscesses.

Figure 2

Figure 3

In Figure 3, the radiographic beam is aimed downward through the hoof and coffin bone. The image on the left is the left foot and the image on the right is the right foot. The yellow dotted circles correspond to the tip of the coffin bone that appears to be more radiolucent (less bone) in the left foot compared to the right foot. This would suggest some sort of pathological process affecting the tip of the coffin bone in the left foot. The possibilities for these radiographic changes include laminitis, chronic abscess with bone infection (osteomyelitis), and keratoma. An MRI study of the foot was strongly recommended to determine the cause and provide key information for likely surgical exploration.

Figure 4

The gelding was referred to the University of Florida for MRI of the front feet. A large area of concern was highlighted in the MRI that was either a chronic abscess or a keratoma. Subsequently, a partial hoof wall resection was performed by Dr. Andrew Smith and his surgical team at University of Florida's college of veterinary medicine (Figure 4). Once the hoof wall was removed, a large keratoma (yellow dotted lines) was identified and removed. A keratoma consists of  a benign tumor of keratin or horn-producing cells. The keratoma will grow between the coffin bone and the hoof wall causing distortion of the hoof wall, recurrent foot abscesses, and laminitis. Surgical resection is the only option but should be preceded by an MRI to identify the keratoma and its dimensions. Prognosis is good for a full recovery assuming the entire keratoma is removed at the time of surgery.

Special thanks to the Dr. Andrew Smith and the University of Florida's radiology department!

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