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.

Fractured Patella in a Horse

A teenage gelding presented for sudden non-weight bearing lameness in the right hind limb. There was a history of a "kick" from another horse but the exact location of the kick was not witnessed. On presentation, there was a basketball-size swelling centered on the stifle and the horse was very painful. He was not willing to walk on the limb. The initial radiographs were not conclusive due to the severe swelling and a follow-up exam was performed 10 days later. On presentation, the gelding was walking on the limb but was very resistant to have the limb flexed at the stifle/hock. There was minimal swelling compared to previous exam.
Figure 1 is a lateral radiograph of the patella. The yellow lines corresponds to bone fragments that are noted along the edges of the patella.

Figure 1

In order to better assess the patella, a special "sky line" projection is required and was especially difficult in this horse because he was resistant to having the stifle flexed! However, it proved to be the most important radiographic view. In  Figure 2, the patella is imaged and a distinct line can be noted traveling through the body of the patella. In Figure 3, the "line" is highlighted in red and is consistent with a complete or near-complete fracture of the patella. In Figure 4, a normal patella is imaged for comparison to the fractured patella.

Figure 2

Figure 3

The degree of fracture appears complete or near-complete which significantly worsens the prognosis. There are cases of patella fracture in horses that are described in the literature that have healed after several months of stall rest. However, there is minimal discussion regarding the future of these horses with regards to as equine athletes. The prognosis for this horse to return to work is poor and his outcome is yet to be determined.

Thin Soles in a Horse!!

The radiographs below in Figures 1-3 belong to a middle-aged QH gelding that presented for severe lameness. The gelding was recently trimmed by the farrier and had a history of mild to moderate foot pain.
On presentation, the gelding was very sore when asked to walk on a firm surface and was not willing to walk in a tight circle! There were NO pounding digital pulses however firm pressure, via my finger tips, over the sole region resulted in a strong pain reaction by the gelding. Radiographs were taken and severely thin soles were diagnosed in both front feet (Figure 1 and 2). The actual thickness of the sole was difficult to measure due to the thinness but was approximated at 2-3mm (Figure 3). Less than 5mm of thickness essentially corresponds to 1 swipe with the hoof knife!!

Figure 1

Figure 2

Figure 3

In Figure 4, there is a radiograph of a normal horse's foot. The sole depth at the toe region is approximately 15-20mm. In my experience, when the sole thickness is less than 10mm, there is increased likelihood of foot pain from concussion with the ground. Thin soled horses are at high risk for sole bruising and sub-solar abscess development. Unfortunately, some horses are "naturally" thin soled due to poor genetics and MUST be managed with shoes. The corrective shoeing is simple and may include a rim pad, leather pad , or soft pour-in pad. I strongly recommend radiographic evaluation PRIOR to any foot trimming to determine the sole thickness of horses that have a history of chronic foot pain!

Figure 4

Fibrosarcoma in a horse!

A 14 year old gelding presented for a complaint of recent lameness and swelling of the right knee or carpus. There was no history of trauma but a plumb size swelling was palpated along the outside of the knee. The gelding resented direct pressure over the knee and any manipulation of the knee. When radiographed, there were no significant abnormalities noted with regards to the bones or articular surfaces that make up the carpus. However, a moderate soft tissue swelling was noted along the dorsal (front) and lateral (outside) aspect of the carpus (Blue circles in Figures 3-4). 

Figure 1

Figure 2

Figure 3

Figure 4

An ultrasound exam was performed on the soft tissue swelling and a hypoechoic (dark) soft tissue structure was identified (Figure 5). This structure appeared well demarcated and was consistent with a mass or tumor which was below the surface of the skin yet outside the joint capsule of the carpus.

Figure 5

When the ultrasound image is flipped into the same projection as the radiograph, the soft tissue mass aligns perfectly with the soft tissue swelling noted on the digital radiograph (Figure 6). The red line corresponds to the middle carpal joint and helps demonstrate how close the tumor is to the joint yet does NOT communicate with the joint.

Figure 6

A core biopsy was taken of the soft tissue mass through a small skin incision directly over the area in question and submitted for analysis.  The histopathology report indicated that the core biopsy was consistent with a fibrosarcoma. This type of tumor is not common in horses and although it does not commonly spread to other regions of the horse, it can be locally destructive and aggressive. As such, it was determined that the immediate course of action was intra-lesional injections of a potent chemotherapy drug. Due to the close proximity with the joint capsule, surgery was considered too risky at this point. The gelding has been treated 1x with a chemotherapy medication and a follow-up exam is expected within 2-3 weeks. To be continued...