If your pet has suffered severe limb trauma your veterinarian may recommend amputation after performing an orthopedic and neurological evaluation. Other organs such as the lung, heart, or bladder may also be injured, necessitating that your cat be stabilized prior to surgery to allow any life-threatening problems to be treated.
In cases of tumors, biopsy is usually performed initially to define the tumor type. This allows your veterinarian to plan the best treatment regime and to give you an idea of the prognosis.
Some limb tumors are so large that amputation is the only effective treatment option. Alternatively, x-rays of the limb may show severe bone destruction that has resulted in a fracture. In such cases there may be no option to amputation, but a biopsy may provide information regarding the prognosis.
Cats undergoing an amputation for a tumor should have blood work and a urinalysis performed to ensure that they are otherwise healthy. A series of chest x-rays may be performed to determine if there is evidence that the tumor has already spread to the lungs.
Biopsies can be taken by removing a small wedge or core of tissue or by using biopsy needles when a sample of abnormal bone is required. A pathologist will examine the tissue and the results should be available in a few days. When the biopsy contains bone, the sample will need to be de-calcified before it can be looked at with a microscope. This may take a few days to two weeks, depending on the nature of the sample.
Local lymph nodes on or around the affected limb will be evaluated for enlargement. In some cases, a needle may be inserted into the nodes to aspirate cells. Such aspirates can then be examined microscopically for evidence of tumor spread.
Amputation will be preceded by the administration of pain-killers or analgesics, usually morphine derivative drugs. By administering them prior to surgery they serve to block pain receptors in the brain before the pain begins. They may be given in the form of an injection or administered via a patch that is placed on a shaved area of skin approximately 18 hours prior to the surgery. For hind leg amputations an epidural analgesic can be performed to reduce postoperative pain. Nerves will be cut during the procedure and these will be blocked with a local anesthetic to further reduce discomfort. Pain-killers will be continued after surgery to ensure a smooth, comfortable recovery. Oral analgesics or anti-inflammatory drugs may be sent home with your pet for a week or so after the procedure.
For forelimb amputations, the limb can be removed at the level of the humerus but removal of the scapula with the limb is more cosmetic.
With hind leg amputations, the level of the amputation will depend upon where the lesion is located. The most common location for amputations to be performed is at the upper third of the thigh bone (the femur). At this site, muscle that has been cut can be brought over the end of the bone to provide a smooth stump. If a tumor exists above or around the knee this level of amputation may be too close to the lesion, necessitating that the amputation be performed at the hip joint. If a tumor exists even higher up the leg, then not only the limb but a portion of the pelvis may need to be removed in order to help ensure complete removal of the tumor.
After forelimb amputations a soft padded bandage is usually placed over the surgical site. The bandage provides protection for the wound and thus makes the animal more comfortable. It also reduces swelling and fluid accumulation at the surgical site. For hind limb amputations bandages are seldom applied.
If the tumor involves the scapula, resection of the scapular bone may be performed. Up to 80 percent of the scapula can be removed without compromising limb function.
Occasionally, alternatives to amputation may be possible for treating certain tumors affecting the limbs. In the forelimb, osteosarcoma of the distal radius, which is the bone just above the wrist joint, may be treated by excision of the bone and replacement with a bone graft, which is fixed in place with a long metal plate and screws. This procedure is referred to as a limb-sparing surgery because it can result in a functional limb. However, this procedure does not affect the overall survival time for this type of cancer.
As in humans, cats can be fitted with a prosthesis following an amputation. For this procedure the amputation is performed lower down on the front leg (below the elbow) to leave an adequate stump for application of a carefully and specifically fitted prosthesis. Many cats function normally with a prosthesis; tolerating the artificial limb extremely well.