New techniques make amputation more viable for some patients

New techniques make amputation more viable for some patients

Oct 01, 2002

Intraoperative view of stump preparation. If adequate tissue to fully enclose stump is not available, as is common in distal limb fracture, then a granulation bed growth is encouraged at the distal end of the stump. A second procedure will be performed in 10 days to transfer grafted frog tissue to this granulation bed.
We have all been there. A client calls to say that she has just found her horse standing in the field unwilling to move.

"His leg is just dangling, there may be a kick mark and I...I think it may be broken."

There have been many improvements in anesthesia and in surgical techniques for fracture repair, you tell yourself as you drive onto the farm road. You see the small crowd standing around the horse as you approach and, from the abnormal angle to the leg and that almost nervous way that he tries to place and replace a leg that no longer does what he wants it to do, you know that the leg is indeed broken.

If the fracture can be repaired surgically then the horse has a chance. If the damage is too severe, then you have to break the bad news to the owner.

Open, infected fractures, bad spirals or comminuted breaks with a multitude of small pieces usually mean the end of a horse's life.

"What about amputation?" someone occasionally asks.

If you are like most veterinarians, the question of equine amputation is usually answered emphatically with "been there, tried that, didn't work." In fact the history of attempts at equine amputation and prosthetic repair does not offer much hope, and this technique has been largely discarded.

If the fracture is so severe or of a type that does not allow standard plate and screw repair or casting with transfixation pins, then the horse is usually euthanized.

Not so fast Fortunately, a group of veterinary surgeons has been thinking and operating "outside the box" and has come up with new techniques and approaches that may make amputation in the horse a very reasonable alternative to the management of a catastrophic fracture.

Stump being prepared for temporary casting. Transfixation pins are shown illustrating the 30-degree diversion angle placement crucial to weight-bearing and successful post-op recovery.
Even though these veterinarians do not practice together, they have been sharing information and discoveries and have collectively justified a new look at an old procedure.

Actual amputation of the distal limb in the horse is not technically difficult and could be reasonably performed by any qualified surgeon. The poor success rate for this procedure in the horse has been due almost entirely to post operative complications.

Fracture upon recovery from anesthesia, wound dehiscence, osteomyelitis of the stump, pressure sores from the prosthesis, contralateral limb failure from laminitis, tendon rupture of fracture and poor patient acceptance are the major problems that have earned amputation in the horse its dismal reputation.

Dr. Ted Vlahos of the Sheridan Animal Medical Center in Sheridan, Wyo., says, "Amputation has been only minimally accepted, and only as a salvage procedure."

Healed stump prior to fitting for prosthetic.
"Taking the leg off a horse is not something that most owners can even contemplate," adds Dr. Barrie Grant of the San Luis Rey Equine Clinic in California.

Yet these two surgeons, along with Dr. Ric Redden of the International Equine Podiatry Center in Versailles, Ky., have modified and improved the amputation and prosthetic procedure to a point where they feel it should be considered as a reasonable treatment option for some injuries and one that allows the horse a good quality of life as opposed to merely "salvage."

All three surgeons have been performing amputations and modifying the technique as they progressed. While they may currently use slightly different steps, the general principles and procedures are similar.

How it's done Prior to surgery, a temporary prosthesis is constructed using inch-flat aluminum stock. A cup is fabricated from this material and two aluminum straps are welded to the medial and lateral aspect.

The horse is then taken to surgery where two transfixation pins are placed at 30-degree divergent angles through the bones proximal to the site of amputation.

Four-and-a-half month foal with temporary prosthetic.
The site of amputation is dependent on the location of the injury. The most common areas of amputation are the proximal and distal interphalangeal joints, and the metatarsophalangeal joint. Amputations of the hind feet seem more common, perhaps because of the increased number of injuries in this area and because these cases do well and as such are attempted more frequently. The hind limbs bear less weight than the forelimbs and tend to do better following amputation.

Grant has had considerable experience with amputations just distal to the carpas or tarsus and amputations higher up the leg than this are rarely attempted.

The load bending forces on the limbs seem to be much greater if the amputation is above the knee or hock and "though we will eventually get there," says Redden, "we don't have that capability yet."

The placement of these transfixation pins seems like a small detail, but this was the first step in improving the success of the amputation procedure.

Prior to placing them at 30-degree angles, the pins were placed in a parallel arrangement. This design was associated with a significant rate of fracture on recovery from anesthesia. The divergent angle placement did not stress the bone as much and almost totally solved that post-op complication.

Frog tissue grafts Another innovation that significantly improved long-term results was the incorporation of frog tissue grafts into the stump closure. Traditionally there is little muscle or other tissue to use when constructing a stump following distal limb amputation in the horse.

Grant has had success using flexor tendon incorporation in stump formation in "high leg" amputations, but this is not possible when amputating lower down the limb. Because of the lack of muscle and other tissue for use in stump construction, many horses had poor stump healing and were prone to rubbing and trauma to the stump by the prosthetic device.