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2003 - 16th Annual Bluegrass Laminitis Symposium Notes

How To Perform An Amputation With Frog And Cushion Graft

Written and presented January 2003 by R.F. (Ric) Redden, DVM

Horses with catastrophic injury or disease of the lower limb are most often euthanized as there is irreversible vascular, soft tissue and bone damage. Amputating the limb well above the dysfunctional area and fitting the horse with a prosthesis is a viable option. Successfully fitting a horse with a prosthesis is similar in some respects to that in the human field but stark differences make it quite a challenge. The ideal condition is the recently injured animal with hind limb involvement. Catastrophic injuries that involve the mid to lower half of the metatarsus or lower appear to respond more favorably than front limb problems, possibly due to weight distribution and the constant twisting load placed on the front end that is not imposed on the rear limbs.

Selecting the right candidate:
I was stimulated by the heroic efforts of Dr. Barrie Grant many years ago to attempt the seemingly impossible feat of providing a horse with an artificial limb. Dr. Grant’s work opened many doors of opportunity for me early in my career. I attempted many cases that had a primary injury and subsequent contra limb laminitis as my first candidates, a real learning curve. In most cases I had to flip a coin to decide which limb was more devitalized and which should be removed, and in spite of hopeless odds we almost succeeded on several cases. One mare that we successfully treated for nine months and was quite happy was euthanized due to severe colon torsion. A stallion, who bred mares with a homemade prosthesis for five seasons, was a total cripple but didn’t know it nor did he care, lost his battle due to colic. Many along the way were euthanized simply due to the failure to have an acceptable quality of life. These early cases made it possible for me to successfully save two quality bred mares heavy in foal with catastrophic, articular fractures involving the proximal metacarpus and lower carpal joints. Both were successfully amputated, fitted with a temporary prosthesis and delivered healthy foals. One mare was euthanized at the owner’s request, the other euthanized due to spiral fracture of the radius due to excessive pin wear.

Hind limb amputation holds a bit more promise. Individuals presented with only unilateral involvement, without impending signs of contra limb laminitis, have all been successful attempts. Five cases remain productive and happy, with the longest case now approaching eleven years and the most recent case eight months. One stallion has successfully covered his mares for six years, one mare has for three years produced embryos which have been successfully harvested, and one filly I have lost track of after three years. The most recent, a Quarter Horse mare, has a healthy stump but apparently has phantom pain due to years of pain from osteomyelitis associated with complicated, chronic, unilateral laminitis.

The procedure is quite simple, requires very few surgical tools and can be performed in most any location. Using a sling for induction and recovery certainly reduces the risk of injury during recovery. The sling must be used for the second cast and several prosthesis changes until the horse has learned to stand unaided by the sling. Therefore a sling set up is imperative; I prefer a twelve foot ceiling and a Liftex sling.

Procedure:
The level of amputation is a great consideration. When the foot and coffin joint are involved, I try to leave PI and the germinal centers of the coronary groove, digital cushion and frog. Provided these structures remain vitalized they can be brought up over the end of PI, and sutured to the existing tendon and skin. Most auto graphs have been successful providing the stump with a tough pad that seems to serve the horse well.

Amputations higher up, mid cannon, I do not attempt to get primary healing of the stump but prefer a healthy, granulating bed over the bone that soon becomes a nice receptive area for a germinal frog graft. At two to three weeks post amputation the stump is healthy and ideal for a graft. A foot on the opposite end of the animal is fitted with a hospital plate shoe, the frog trimmed very thin and surgically prepped. Once under general anesthesia, the cast and temporary prosthesis is removed, the hospital plate removed from the shod foot, and a small strip of germinal tissue is removed along the body of the frog. This strip is then cut into small pieces (1-2 cm. in size) and implanted throughout the granulating stump. Pad the stump with ½ inch felt, cut to fit snugly and apply a cast using the pins to support the limb and protect the stump. All cases treated in this fashion have grown a zone of cornified horn, some have wall tubules with frog tissue others just frog tissue. The results have been very stimulating and demand further research.

The actual amputation technique is quite simple and straight forward; just remove the diseased tissue, dissect away the frog and digital cushion, leaving it attached to the vascular supply. Then fold the germinal tissue forward over the end of PI. A transcortical cast provides pain free post op care for three to seven weeks. Once micro fractures form around the pins they must be removed and the stump loaded. The temporary prosthesis can be made in a typical shop using a variety of materials. I prefer ¼ inch aluminum plate to form the stump for the lower amputation. The higher amputations must have adequate leg extension that can be made with aluminum pipe, PVC for lighter horses or even wood. The goal is to simply replace leg length and secure it to the limb so it doesn’t twist or fall off. I hope to soon provide a monograph that shows many various ways to build and fit a temporary or even permanent prosthesis.

If you have a candidate please call me and I will do all I can to help you assess the case and walk you through each step of the procedure.