Last month's column covered limb sparing in dogs for the treatment of appendicular tumors, namely sarcomas. This month, I will briefly review the use of limb sparing for other, less common, more challenging, anatomic sites.
Last month's column covered limb sparing in dogs for the treatment of appendicular tumors, namely sarcomas, and the techniques recommended for use in the distal antebrachium. This month I will briefly review the use of limb sparing for other, less common, more challenging, anatomic sites as well as a possible limb sparing alternative.
Photo A: lateral radiograph showing an osteosarcoma in the distal radius.
The scapula, like the distal ulna, can be removed and not replaced. As a general rule, the amount removed and the size of the dog are inversely related to the degree of limb function and speed of recovery that one might expect. A complete scapulectomy can be performed if necessary. The prognosis for functional outcome remains good to excellent for most dogs. Physical rehabilitation can make a tremendous difference in the final functional outcome.
Limb sparing using allografts and extracorporeal irradiation have been described for use in the proximal humerus. However, the functional results and complication rates have been unacceptable. There is currently no surgical technique recommended for this location.
Photo B: lateral radiograph following limb sparing using microvascular transfer of the distal ulnar graft.
Tumors of the proximal femur may be addressed with femoral head and neck ostectomy or total hip arthroplasty. For more extensive disease, the affected femur is excised, preserving the tendons for muscular reconstruction. The excised bone is replaced with allograft. Total hip arthroplasty is then done, using a specially designed femoral implant with a longer femoral stem that will extend beyond the osteotomy site, providing mechanical stability, to complete the procedure.
Two techniques are described for use in the distal tibia: distraction osteogenesis and microvascular transfer of a distal ulnar graft (Photos A and B). Distraction osteogenesis as previously described in the radius also works well for the tibia. Using two bone segments, allowing for more rapid transport and restoration of the bony column, also is reported.
Stereotactic radiosurgery and intensity-modulated radiation therapy (IMRT) are "non-surgical" modalities that have the ability to deliver high doses of radiation to the tumor while sparing normal tissues. These techniques have the potential to be very useful in cases in which maintenance of limb function is necessary for an acceptable quality of life. Unfortunately, they are not readily available to veterinarians at this time.
In conclusion, many techniques are available for limb sparing, each with advantages and disadvantages. Limb sparing requires significant planning, skill, case selection and follow-up on the part of the veterinary team. Just as important is solid owner commitment. Client education and cooperation are imperative for a good outcome.
Dr. Bernard Séguin is an ACVS board-certified surgeon who is an assistant professor at the College of Veterinary Medicine, Oregon State University. His research interests include osteosarcoma and limb sparing.