Stifle OCD!!

A yearling thoroughbred presented for sudden lameness and swelling around the stifle joint. The filly had been purchased several months prior from a select thoroughbred sale and repository radiographs were performed at the time of purchase. At the time of purchase, the filly was sound, there was no effusion of the stifle joint and there were no obvious radiographic changes noted in either stifle joint. When the filly presented for lameness, the stifle radiographs were repeated. Close inspection of the lateral trochlear ridge suggested irregular contours (yellow arrows inside blue box, Figure 2) of the trochlear ridge along the mid body region (Figure 1 and 2, blue box). Based on the radiographs alone, the filly was treated with intra-articular Hylartin and forced stall rest for 30 days.

Figure 1

Figure 2

Unfortunately, the filly remained lame after 30 days of stall rest and a follow-up exam included an ultrasound evaluation of the stifle joint. The ultrasound exam revealed significant changes along the lateral trochlear ridge which were not fully appreciated on the radiographic exam. In Figure 3, the lateral and medial trochlear ridge are displayed. The bony surfaces of the trochlear ridges appear as a bright white lines and the cartilage as  thin black lines that follow the contour of the bony surface. Any disruption of the bony surface/cartilage will appear as a mix of disrupted white lines and black pockets. In Figure 3, the image on the left is of the lateral trochlear ridge and there is clearly disrupted bone and cartilage along the bony surface.

Figure 3

In Figure 4, the lateral trochlear ridge is imaged in a longitudinal plane to assess the length of the defect. Irregular bone/cartilage appears to extend for several centimeters along the length of the trochlear ridge (yellow lines). The filly was referred for arthroscopic exam and a large bone/cartilage defect was identified on the lateral trochlear ridge consistent with a osteochondritis dissecans or OCD lesion.

Figure 4

Osteochondritis dissecans is defined as a disorder that results in cracks in the articular cartilage and underlying subchondral bone. The "cracks" and cartilage separation result due to lack of blood flow to the region resulting in avascular necrosis of the tissues involved.  This condition is considered in part a hereditary disorder AND nutritional.  Unfortunately OCD lesions are common in young horses that were bred for sport such as racing thoroughbreds, performance quarter horses, and warm blood breeds.  Some cases of OCD can be managed with surgical intervention however the OCD lesion in this filly's stifle was so large that there was no hope for soundness. This case is a good example of the benefit of multiple imaging modalities in diagnosing the source of lameness in the equine stifle.

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.