Here are some numbers to keep in mind when dealing with osteosarcoma of long bones:
- Early peak in age: two years
- Late peak in age: eight years
- Breeds: most often large and giant
- Area most affected: the metaphysis of long bones
- Front leg: often “away from the elbow”
- Hind leg: “close to the knee” may be debatable
- Front vs. back: front limbs are affected twice as often as hind legs
- Without chemotherapy, 90 percent will metastasize within one year
- Average survival with amputation alone: four months
- Average survival with radiation therapy alone: four months
- Average survival with amputation and chemo: 10 months, though some say one year
What on earth is limb sparing?
Limb sparing, or “limb spare,” is a highly specialized limb salvage procedure that consists of en bloc excision of the tumor. Depending on the specific location, the missing bone may or may not need to be replaced with some sort of graft.
The most common and practical location for limb sparing is the distal radius. The missing bone can be replaced with a variety of grafts: the distal ulna; the distal radius segment itself after radiation or pasteurization; an allograft from a bone bank; or a metal cylinder.
Because the stability of the carpus is compromised after removal of the distal radius, the joint requires an arthrodesis. Therefore, a long bone plate spans most of the radius, the carpus and one metacarpal bone.
The most difficult part of limb sparing is not the technique, or the cost or postoperative care. It is the selection of the correct candidate: There should be minimal adjacent soft tissue invasion.
Chemotherapy is always used after limb sparing, systemically and sometimes locally.
Survival does not seem to be greatly improved by limb sparing, compared to amputation. This option is therefore chosen when the client will not accept the concept of amputation, or when the amputee would predictably not function well.
For example, dogs with severe orthopedic or neurological conditions may not be good candidates for amputation. Careful assessment is critical to ensure that limb sparing is a better option.