Amputation remains the standard of care to address most primary tumors of the appendicular skeleton, particularly sarcomas.
As a general rule, dogs adapt well to amputation, regardless of size. However, dogs suffering from concurrent orthopedic or
neurologic diseases, or those with owners opposed to amputation, may be poor candidates for this procedure. In those cases,
limb sparing may be an option. As the name implies, limb sparing is a surgical procedure in which a portion of diseased bone
is removed or treated while limb function is preserved.
Proper staging must be performed to ensure the procedure is in the best interest of the patient. Surgical planning to ensure
appropriate margins for both soft and bony tissues is essential. Advanced imaging such as CT and MRI may facilitate this,
as well as help determine whether the patient is even a candidate for limb sparing.
The techniques for limb sparing, prognosis for functional outcome and complications seen are dependent on the anatomic location
of the tumor. The site most amenable to limb spare is the distal ulna. It can be removed and does not need to be replaced.
Ideally, the interosseous ligament is preserved. If the styloid process must be excised with the tumor, reconstruction of
the lateral collateral ligament or pancarpal arthrodesis will maintain stability of the antebrachiocarpal joint. The prognosis
for limb function is usually excellent.
The anatomic site receiving the most attention for limb sparing is the distal radius. It is one of the most common sites for
osteosarcoma in dogs. Most commonly, the diseased distal radius is replaced with a cortical allograft (Photo 1). Unfortunately,
the complication rate is high, with infection seen in up to 70 percent of limbs and local recurrence and implant problems
in as many as 60 percent of the limbs.
Photo 1: Dog undergoing limb sparing surgery using the allograft technique. The allograft is being held by the surgeon. The
plate has been applied to the allograft, and it will be placed into the bony defect present from having removed the distal
aspect of the radius harboring the tumor. The plate will then be applied to the proximal aspect of the remaining radius and
the carpus and metacarpal bone.
This technique does require maintenance of a bone bank or purchase of a commercially available cortical allograft. A metallic
endoprosthesis with specialized bone plate now is available as an alternative to cortical allograft. A study comparing the
endoprosthesis and cortical allograft found no difference in complication rates.
The distal radius can be replaced with viable autograft using distraction osteogenesis or transfer of an ulnar segment. Distraction
osteogenesis utilizes the principles and techniques developed by Ilizarov.