Performing an Amputation
Updated: Apr 22, 2020
Indepth Equine Podiatry Symposium Notes Written and presented January 2009 by R.F. (Ric) Redden, DVM
Amputation can be an option for horses that have suffered irreversible, catastrophic loss of blood supply to the foot, pastern, fetlock, cannon bone, hock or knee due to injury or disease. Typical cases may include acute and chronic debilitating deformities in young horses, explosive fractures involving the pastern, distal cannon, combination suspensory apparatus failure, extensive irreversible damage due to joint sepsis and extreme lacerations that destroy major arterial supply to the digits. Fractures of this nature can occur at high speed, be the result of paddock injuries and occur while in a stall or being worked on a lunge line.
When determining whether or not amputation is a viable option many things must be taken into consideration. The personality of the animal is very important to consider. Aggressive, high strung, unruly or unbroken animals pose serious risk of injury for those attending to frequent surgeries and aftercare. Financial commitment can also be a determining factor, as a great deal of expense can be involved, especially if complications arise. The location of the injury (below or above the knee or hock) can also affect whether or not amputation should be attempted. Adequate surgical and aftercare facilities must be available and should include a 12 foot high beam system compatible with using an electric one ton hoist and sling, as after care is performed in a sling for the first 4-5 months until the horse learns to stand quietly without the sling for support. Aftercare personnel with good horsemanship skills will be necessary as well as a qualified farrier who enjoys mechanical challenges. The farrier should be open minded with the energy and optimism to make it happen, and willing to work closely with a veterinarian who also thrives on challenges.
Ideal Candidates:
Athletes who suffer an acute, catastrophic injury are good candidates for amputation as they are otherwise very fit and healthy and the opposite foot is most likely very healthy at the time of injury. Hind limb injuries at or below the fetlock would be the very best candidates; the second choice would be a mid to upper cannon amputation site on a hind limb, which would require a full limb prosthesis.
Ponies and miniature horses (200-300 pounds) have a very good prognosis simply due to their light body weight. I have had several cases, and all have been receptive to the prosthesis. Prosthesis and stump management have been uneventful.
Hind limb cases have a better prognosis than front limb cases due to less weight distribution on the hind end. Lower leg injuries have a better prognosis and lower maintenance requirements than mid-cannon amputations. Pastern or hind limb fetlocks require a short limb prosthesis (below the hock or knee). Mid-cannon, carpal or hock amputations and some front limb fetlock amputations require a prosthesis with an above the knee or hock extension. This can be hinged for select cases in front but a stiff, full limb works best for behind.
Breeds that naturally have exceptionally good quality feet (thick and tough walls, 20+mm of sole with natural cup, 3-5 degree PA and strong digital cushion) can be reasonably good candidates even when contra limb laminitis affects the good foot. However, the laminitis must be manageable regardless of the degree of vascular damage and should always be the prime focus, as the good foot can deteriorate very quickly when laminitis is present. Standardbreds top the list of tough footed horses, followed closely by Tennessee Walking Horses. I often say you can't hurt these breeds with a running chain saw, as they are very durable with no limit to their pain threshold.
Poor Candidates:
Front limb injuries or disease that involves both limbs are not good candidates for amputation. Note that I classify these cases as poor candidates, not impossible. There is enough clinical evidence to suggest that bilateral amputation is possible and could be a viable option for select cases.
Young horses with chronically painful injuries or disease that bow the opposite limb at the knee or hock are poor candidates as the opposite limb deformity remains a threat. As a rule it will continue to worsen with age and weight gain, which precludes all efforts to offer them a quality life even when the amputation and acceptance of the prosthesis are uneventful.
Contra limb laminitis certainly diminishes the prognosis considerably when injury or disease has precipitated this frequently occurring problem. Laminitis in the opposing foot can be a major problem following surgical repair of catastrophic injury. Fortunately this common complication can be prevented in a large majority of high risk cases and can be treated successfully in most cases provided irreversible vascular damage has not occurred. Detection and timely realignment followed by a mid-cannon DDF tenotomy guided by evidence from comparative venograms can have very gratifying results even when it looks like all is lost to this devastating disease. This is where an ounce of prevention is worth a pound of cure.
Cases that are initially treated surgically but deteriorate due to sepsis or major blood loss to the healthy tissue are poor candidates for amputation. Due to new, ongoing surgical developments many catastrophic injuries are now considered potential surgery candidates. Their ability to heal is based on adequate vascular supply, efficiency of fixation, temperament of the animal and uneventful aftercare. However, cases that are borderline for surgery due to the extent of the injury become far better candidates for an amputation than surgery, provided the decision is made at the time of injury and not weeks after it is obvious that the surgical approach failed to meet the criteria for returning the limb to a healthy, useful state. Contra limb laminitis is imminent in cases that heal slowly and have ongoing complications. Performing the amputation at the time of injury instead of attempting a very high risk surgery can offer much better long term results and bypass the risk of contra limb laminitis. Amputee pin cast cases are much sounder immediately following surgery than those with implants and cast.
The problem with slow healing or complicated surgical cases is that they will show no signs of contra limb laminitis until the good foot becomes more painful than the surgical leg. By this time laminitis has been present for several weeks and tremendous vascular damage has occurred. However, if the initially injured limb is 80-90% healed when laminitis is detected good results can be obtained by realigning the palmar surface with the natural load zone (derotation) followed by a DDF tenotomy. When performed in a timely fashion, most hind limb contra limb laminitis cases have a reasonably good prognosis.