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Bone Sequestrum

It happens to our horses too: Lenny’s “Innocent” wound and the benefits of radiographs and Intravenous Regional Perfusion (IVRP). I don’t want to have to post  regular cases of this nature, but I thought it may give reassurance to fellow horse owners that, despite our best intentions, problems can occur in vets’ horses too!

Figure 1. Appearance of Lenny’s wound 2 weeks after initial injury

Two months ago one of our hunters sustained a small wound to the inside of his left hind leg just below the hock.  We treated it in the usual way over the first three days with regular lavage of the area and topical and systemic antibiotics.  Lenny (also known as The Warrior!) was never lame and we were not unduly concerned.  In fact he stayed in work and continued to live up to his “warrior” status.  Over the following few weeks, however, the wound failed to heal and he became increasingly sensitive to palpation of the region. The wound edges started to gape and there was more localized swelling (figure 1).

Although the actual skin defect looked relatively “innocent” we were concerned about the underlying bone as there is little overlying protection in this area.  We took a precautionary radiograph to highlight this inside area of his limb and found our answer (figure 2).

Figure 2. Radiograph of Lenny’s injured leg with a sequestrated piece of bone within his inside splint bone and a narrow fracture line continuing obliquely

The initial trauma to the leg had damaged the splint bone directly under the skin causing a hairline fracture.  While most small fractures of this nature heal routinely with rest complications can occur, as in Lenny’s case, when the blood supply to the bone is impaired and the chip of bone is unable to heal.  The presence of this devitalized chip of bone, or sequestrum, prevents the skin wound from healing and a persistent discharging defect will remain until the chip is removed.

Fortunately Lenny is an amenable character and he allowed us to scrape out the offending sequestrum under a small amount of sedation and some local anaesthetic.  The  photograph in figure 3 shows the piece of bone that was removed. A bone curette was also used to remove unhealthy granulation tissue and irregular callus formation at the fracture site to stimulate healing.  A radiograph was then taken to ensure the splint bone had been fully debrided (figure 4).

Figure 4. Radiograph of the splint bone after debridement

 

 

 

Figure 3: The sequestrated chip of bone that was removed with a bone curette

 

Lenny was then box rested for 3 weeks.  The splint bone was supported by a half limb pressure bandage which was changed every 4 days to monitor discharge from the wound.  In addition to a short course of systemic antibiotics he also received a localised infiltration of antibiotic via his saphenous vein that courses over the inside of the hock.  This technique, known as intravenous regional perfusion (IVRP) increases the concentration of antiobiotic at the area in the body where it is most needed and was a useful adjunctive treatment in this case. It is simple and quick to perform, involving the application of a tourniquet above and below the wound and injection of antibiotic into the vein via a small catheter.

Figure 5. Appearance of wound 1 week after standing surgery and IVRP

 

Following his treatment Lenny made a good recovery.  The wound started to granulate with healthy tissue (figure 5).  Four weeks after surgery the wound could barely be seen (figure 6).

Figure 6. Appearance of wound 4 weeks after surgery and IVRP