Limb-Spare
The aim of the limb sparing procedure is to save the leg instead of performing an amputation. The goal is to provide a functional, pain-free leg while not jeopardizing the chances of survival. Medical indications for limb sparing include previous amputation of another limb, severe concurrent osteoarthritis, or neurologic disease. For example, in over 300 limb sparing surgeries performed at Colorado State University, 85% of the patients have experienced good to excellent function. The average survival after limb sparing and chemotherapy is 50% or better at 1 year, which is equal to the survival of dogs receiving amputation and chemotherapy.
It is extremely important to determine if the dog is a candidate for limb sparing procedure. The pretreatment evaluation should include a CBC, urinalysis, biochemical profile (paying particular emphasis to the serum alkaline phosphatase, which can have negative prognostic implications), chest x-ray, and a bone survey or nuclear bone scan. 10-15% of patients will have multiple lesions at the time of diagnosis which carries a worse prog¬nosis. Pathologic fractures are a relative contraindication due to soft tissue contamination via hemorrhage and hematoma. If there is evidence of spread of the cancer, limb sparing surgery is not an option.
Limb sparing surgery is most successful for dogs with primary bone tumors in the distal radius and ulna. Dogs with osteosarcoma of the front leg at the “wrist” (distal radius or ulna) with no evidence of cancer spread to other sites in the body may be candidates for limb sparing. Candidates for limb sparing surgery include dogs with tumors confined to the bone, minimal extension into adjacent soft tissue, and involvement of less than 50% of the bone length. The extent of bone involvement is most accurately determined using CT scans. Other locations are often associated with higher rate of complications and poor postoperative limb function.
To see if your dog is eligible for a limb sparing, several tests will be done, such as blood tests, x-rays, bone scan, ultrasound or computed tomography scans to look for evidence of cancer in other parts of the body. If the tumor is found only in the leg, then limb sparing may be an option. If limb sparing is contemplated, the biopsy technique and position should be carefully planned. Preoperative treatment with cisplatin (chemotherapy) and radiation makes the surgery easier and decreases the chance of recurrence. The optimal dose, route of delivery, and timing of cisplatin relative to the radiation is still unclear. However, this adds significantly to the cost of treatment and is not commonly used.
In limb sparing surgery, the tumor and the affected piece of bone are removed. The space created after the tumor removal is usually filled with an allograft, autograft, or metal implant. An allograft is sterile, frozen bone that has been stored in a bone bank and harvested from dogs that died of other causes. An autograft involves surgically separating the tumor site from the leg and then treating it with a high dose of radiation to “kill” the tumor. Once the allograft, autograft or metal implant is inserted into the defect, a stainless steel plate is applied, and the wrist is fused. The plate is not removed unless it causes problems. Although the wrist can no longer bend, this is not painful and dogs can use the leg almost normally as they compensate by increasing elbow and shoulder motion. In some cases, dogs with tumors of the ulna may not require an allograft or fusion of the wrist.
The surgery itself takes about 2 to 3 hours, but generally anesthesia may last 4 to 5 hours. Dogs stay in the hospital for 2-4 days after surgery. After surgery, a soft padded bandage (usually not a cast or splint) will be applied to the leg, to prevent licking of the wound. The bandages may be changed every few days. Elizabethan collars should be used for dogs who are adamant about licking the bandages. Weight-bearing and range-of-motion exercises can be started immediately after surgery but should be restricted to leashed walks for the first 4 weeks. Exercise is important to prevent contractures of the toes and to decrease swelling in the limb. Most dogs resume normal activities within one to two months after surgery. Medications that are routinely used after surgery include antibiotics and pain medications.
Chemotherapy is usually be started 2 weeks after surgery, with drugs such as cisplatin, carboplatin, or doxorubicin. Four to six treatments, 3 weeks apart, may be recommended depending on the drugs used. This is necessary to try and prevent metastatic cancer. If no chemotherapy is given, there is only a 10% chance that your dog will be alive one year after surgery. However, if chemotherapy is given, the one-year survival probability is 50% and the 2-year survival is 30%.
The most commonly reported complications with limb-sparing surgery are implant failure, local tumor recurrence, and infection. Implant failure occurs in approximately 10% of cases. The use of an orthopedic cement known as methylmethacrylate reduces the incidence of screw loosening, implant failure, and fracture. Local tumor recurrence is caused by incomplete resection or, more commonly, residual neoplastic cells in the soft tissue adjacent to the tumor capsule after marginal resection of the primary bone tumor.
Infection is the most significant postoperative complication encountered with limb-sparing surgery. The cause of infection is unknown, although the extensive resection of soft tissues, poor soft tissue coverage, use of orthopedic implants, and administration of local and systemic chemotherapy are thought to contribute. The use of antibiotic impregnated cement has decreased the risk of infection, which was about 40%. Initially, infections are treated with antibiotics, saline lavages, and wet-to-dry bandages. If the infection is unresponsive or recurs despite treatment, antibiotic-impregnated methylmethacrylate beads can be surgically implanted adjacent to the infected bone. Amputation of the limb may be necessary as a salvage procedure in dogs with uncontrollable infection.
There is generally less than a 20% chance that the tumor will regrow in the leg (local recurrence). Insertion of an absorbable chemotherapy (cisplatin) sponge into the wound at the time of surgery decreases the chances of local recurrence. The chemotherapy sponge is a biodegradable polymer, which slowly breaks down in the body, releasing cisplatin in very high concentrations to the tissues in the surgery site. Only a low dose of cisplatin gets into the blood stream. This high local dose of cisplatin will kill cancer cells remaining in the leg after limb sparing surgery. This material does not usually affect healing, is well tolerated and does not cause noticeable side effects.
Periodic physical examinations as well as chest and leg x-rays will be necessary to follow the dog’s progress. Unless covered by a funded study, the cost of a limb spare surgery ranges from $3,500-$5,000, depending on the amount of the work-up already done by your veterinarian. Follow-up chemotherapy can range from $1,000-$4,000, depending on the drugs chosen. The total cost for one year of treatment and follow-up can be as high as $10,000. It is possible that your dog may be eligible for certain trials investigating various aspects of limb sparing and the treatment of OSA.