Current treatment options for dogs with appendicular osteosarcoma - Veterinary Medicine
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Current treatment options for dogs with appendicular osteosarcoma
Your therapeutic choices for dogs with osteosarcoma in their limbs continue to expand. Deciding which option is best comes down to the site and extent of the tumor and the owner's preference.


VETERINARY MEDICINE


Ideal candidates for this procedure are dogs with good cortical integrity and without pathologic fractures. Dogs undergoing pasteurized autograft limb salvage have survival times and complication rates comparable to dogs undergoing cortical bone allograft and bone transport osteogenesis limb salvages.18 When this technique was used in conjunction with adjuvant chemotherapy, mean and median survival times in a small cohort of patients were 531 and 324 days, respectively, with overall survival rates of 100%, 50%, and 44% at six, 12, and 18 months, respectively.18 While this technique eliminates the need for establishing and maintaining a bone bank and has the advantage of proper fit to the recipient site, pasteurization increases the duration of surgery, and screw placement in the pasteurized bone segment can be limited by tumor erosion.18

Bone transport osteogenesis

Distraction osteogenesis involves applying gradual traction to certain tissues, which creates stresses that can stimulate and maintain the regeneration of active growth.33 Persistent traction causes tissues to become metabolically activated, resulting in an increase in the proliferative and biosynthetic functions. These processes depend on an adequate blood supply to the tissues being elongated and the stimulating effect of functional weightbearing.33 This biologic phenomenon has been used to control healing and shape bone and soft tissue formation to treat traumatic and pathologic musculoskeletal abnormalities.33

Bone transport osteogenesis is a specific application of distraction osteogenesis. It is used to replace large segmental bone defects and has been used clinically in both animals and people.20,21,29,34-38 This technique involves slowly moving an intercalary segment of healthy normal bone into an adjacent defect. Typically, the intercalary segment of the bone is transported by wires that pass through the bone segment and anchor to a circular external skeletal fixation device. The wires are moved in a linear direction along the fixator frame. As the transport segment is moved, new regenerate bone forms in the trailing distraction pathway. Optimal bone formation is obtained by using a distraction rate of about 1 mm/day.29,36 The regenerate bone acts as a highly vascularized autogenous graft that remodels into lamellar bone. In addition to being successfully used in dogs and people for repairing osseous defects related to trauma and infection,37,38 this technique has been successfully used to resolve subtotal defects of the distal radius and tibia of dogs after tumor resection (Figures 2A & 2B).20,21

Many of the complications associated with cortical bone allografts can be avoided when bone transport osteogenesis is used to replace the resultant bone defect. With autogenous bone produced by bone transport osteogenesis, concerns regarding failure or loosening of internal implant components, graft rejection, transmission of infectious disease, and harbored bacterial infections are either decreased or eliminated.20 Previous research has shown that fewer complications (such as fracture and infection) were associated with the use of bone transport osteogenesis (33%) than with traditional segmental defect replacement (60%).38 The well-vascularized regenerate bone is highly resistant to infection.39

Local recurrence of the tumor is still a concern; however, proper case selection, administration of adjuvant chemotherapy, and adherence to sound surgical oncologic technique help to minimize this potential risk.11,16,20,23,40 While necrosis of the regenerate bone has been reported, this complication may have been related to preoperative radiation administration.20 A recent study has shown that administering cisplatin during the distraction and docking process (the process by which the newly formed and preexisting bone fuse) does not adversely affect regenerate bone formation.41

The principal disadvantage of using bone transport osteogenesis for limb-sparing is the relatively long period that the fixation device must be maintained. This is particularly true when dealing with longer segmental defects. Previously reported applications of bone transport osteogenesis for limb salvage in dogs with osteosarcoma used a rate of 1 mm/day and a rhythm of 0.25 mm/6 hours.20 A large defect may require a substantial amount of time for adequate distraction and consolidation; 100 to 147 days of distraction were reported in cases without local recurrence.20 During this time, weekly visits to the local veterinarian and exercise restrictions such as leash walking are required. A technique known as double bone transport has been recently reported as a treatment for tibial osteosarcoma in dogs.21 This technique involves the simultaneous distraction of two transport segments, allowing a defect to be filled more quickly than with a single transport segment.


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Source: VETERINARY MEDICINE,
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