Superficial Flexor Tendonitis in a Horse

A 12 year old mare presented for sudden onset forelimb lameness and swelling of the tendons in the right front limb. On palpation, the swollen tendons were significantly sensitive to palpation yet it was not possible to determine if it was the superficial flexor tendon (SDF) or the deep digital flexor (DDF) tendon. The mare was a grade 3/5 lame in the right front when trotted in a straight line on firm ground. Ultrasound exam of the soft tissue structures revealed a core-like lesion within the outside corner of the SDF tendon. In Figures 1-3, the core-like lesion appears as a black area (red circle) within the body of the SDF tendon (blue circle).  In Figure 2, the image to the right is a cross-sectional view of the tendon and the lesion is a small black circle within the body of the SDF tendon. In the image to the left in Figure 2, the tendon is in a longitudinal view and the lesion appears as a black streak through the body of the SDF tendon.This view is important because it highlights the over-all length of the lesion which in this case was 4-5cm long. The cross-sectional area measured in Figure 3 determined that the core-like lesion was approximately 20% of the entire cross-sectional area of the SDF tendon.

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The mare was treated with ultrasound guided injection of Platelet rich plasma (PRP), stall rest, daily ice therapy and we will follow-up with 3 doses of extra-corporeal shock wave treatment. We anticipate a full return to work after the appropriate period of rehabilitation.

Superficial Flexor Tendonitis in a Horse

A middle-aged gelding presented to PHD veterinary services for tendonitis of the superficial flexor tendon (SDF). The tendonitis was a result of an tendon-sheath penetrating injury and was associated with a severe tendon sheath infection. The tendon sheath infection was treated aggressively and effectively by an equine surgeon. An ultrasound exam was performed along the plantar aspect of the hind fetlock and a large, core-like lesion was identified (Figure 1, black area within red circle). The lesion consisted of disrupted tendon fiber and edema. Several options were considered to help the "healing process" involving the SDF tendonitis. These included extra corporeal shock wave treatment, platelet rich plasma (PRP) injection, stem cell injection, and/or concentrated bone marrow injection. The decision was made to treat the lesion by injecting a mixture of concentrated bone marrow mixed with PRP product. The bone marrow was collected from the horse's sternum and concentrated on site (Figure2). In addtion, a blood sample was collected from the horse and PRP was harvested on site. The PRP was mixed with the concentrated bone marrow and then injected into the lesion via ultra-sound guided technique.

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Figure 2

In addition to the PRP+bone marrow injection, the horse was fitted with a corrective shoe that provided significant heel extension (Figure 3 and 4). This type of shoe is also known as a "fish tail" show and will reduce the "load" across the fetlock joint by supporting the lower limb. Horses recovering from tendon sheath infections and SDF tendonitis tend to avoid fully loading the back of the foot which may result in lower limb contracture. The fish tail shoe allows the horse to fully load the foot in a more comfortable fashion. The horse was walked daily and otherwise kept in stall confinement. In addition, the leg was treated daily with cold compresses.

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Approximately 30 days after the PRP+bone marrow injection, the horse's limb was re-ultrasounded. There has been significant "filling in" of the lesion (Figure 5). Although the area that was the lesion (red circle) remains identifiable, there has been a significant improvement in tendon fiber alignment and the edema (black) has nearly completely resolved! Although this represents a tremendous amount of improvement in just 30 days, there remains a significant period of rehabilitation before the ultimate out come of this case can be reported.  This case provides an example of a regenerative therapy that combines PRP and progenitor stem cells (bone marrow) for the treatment of tendonitis! The advantages of this approach versus stem cell treatment include reduced cost, on site harvesting and same-day treatment.

Figure 5

Superficial digital Flexor Tendonitis (Bowed tendon) in a Horse!

A  twenty year-old mare presented for sudden, severe swelling of the left front lower limb. The mare was nearly non-weight bearing lame and had been seen galloping around her paddock moments before. Prior to my exam, the mare was stalled for 7 days and treated with ice and systemic non-steroidal mediation (phenylbutazone). On presentation there was a noticeable "profile" to the lower portion of the forelimb (Red line:Figure 1). The mare was moderately positive to pressure over this swelling and was lame at the walk. On palpation, there was no distinction between the superficial digital flexor tendon and the deep digital flexor tendon.

Figure 1

Ultrasound examination of the lower limb, beginning just below the knee (carpus) revealed inflammation of the superficial digital flexor tendon (SDF). The inflammation was moderate just below the knee (Figure 2) however became severe further down the leg (Figure 5). In Figures 2 and 3, moderate to severe edema (dark tissue) is noted with pockets of disrupted fiber pattern. The image in Figure 4 is of the opposite limb for comparison to /the abnormal limb. In Figure 5, the SDF tendon (Red arrows) is severely enlarged and there is no apparent pattern with regards to the fiber pattern. These findings are consistent with a near rupture of the SDF tendon.

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Figure 3

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Although the outward and inward findings are severe, the prognosis for pasture soundness is good. It will take 6-12 months for this type of injury to heal with a fibrotic scar but the mare is likely to return to soundness as a pasture horse. Unfortunately, her prognosis as a riding horse is poor and it is not recommended to return this mare to any type of forced work due to her age and degree of injury. Tendonitis of the superficial flexor tendon can occur in various regions of the lower limb. The closer to the knee/carpus (High bow), the worst the prognosis, even for pasture soundness. This is due to the constant irritation of the tendon when the horse advances the limb. In addition, horses that suffer a "bowed" SDF tendon are at increased risk for another injury to the same tendon and it commonly occurs above or below the original injury. My recommendation for rehabilitative care includes the following:

1: Limited activity: preferred stall rest with hand walking for 2 months followed by small paddock turn-out
2: Daily ice therapy for 2-3 weeks
3: Topical non-steroidal cream: Surpass
4: Consider Extra-corporeal shockwave treatment and PRP injection.