Ultrasonography of Osteosarcoma in Dogs
Sonography Atlas of Dogs

ABSTRACT:

Osteosarcoma (OSA) is the most common bone tumor diagnosed in dogs and represents approximately 85% of canine skeletal tumors. The most commonly employed therapy is amputation of the limb followed by chemotherapy. However, preservation of the afflicted limb has been successful for patients with concomitant neurological or orthopedic conditions, which are contraindications to the complete amputation, or with owners reluctant to the possibility of amputation. For these reasons, the purpose of this study was to describe the technical procedures that allowed limb salvage through the use of pedicle frozen grafts in a dog with femoral OSA. Surgical procedures consisted of a femoral diaphyseal osteotomy with tearing of the soft tissues; thus, creating a bone pedicle that was frozen in liquid nitrogen according to the protocol outlined by ^{TSUCHIYA et al. (2005)}. Limb function remained satisfactory for six months.

Key words: bone tumor; canine; cryotherapy

 

Osteosarcoma (OSA) is the most frequent type of bone tumor (85%) and represents 3% to 4% of all tumors in dogs (^{BURACCO et al., 2002}, ^{JOHNSON & HULSE, 2005}). The diagnosis is based on the medical history, physical examination, radiological findings, bone scintigraphy, and computed tomography results. Confirmation of the diagnosis is achieved with tumor biopsy followed by histopathological examination (^{LIPTAK et al., 2004}).

The purpose of OSA treatment is to allow local control of the disease and to prevent metastasis. Amputation and limb preservation are two possible treatment options for the primary tumor; whereas, chemotherapy is required to minimize the risk of developing metastases. Limb preservation surgery, referred to as "limb-sparing," was developed for special cases in which the patient has other relevant concomitant diseases, such as a neurological or orthopedic disease, or when the owners do not allow amputation (^{BURACCO et al., 2002}; ^{LIPTAK, 2004}).

Limb sparing surgery provides pain-free, functional use for the patient without adversely affecting survival. Among the several techniques that can be employed for limb sparing, substitution of the neoplastic region by allogeneic or autologous grafts is the most commonly used technique (^{EHRHART et al., 2013}).

Reconstruction using the autologous neoplastic bone requires devitalization that can be achieved by autoclaving, pasteurizing, or irradiation of the bone. However, these treatments demand the use of special equipment and involve heating procedures that can weaken the bone and decrease osteoinduction. For these reasons, ^{TSUCHIYA et al. (2005}) have developed a devitalization procedure in humans that involves freezing the bone in liquid nitrogen. There are several advantages associated with this method including its simplicity and low cost as well as maintenance of the osteoinduction and bone osteoconduction properties, perfect adaptation between the bone interfaces, biomechanical strength, lack of disease transmission, lack of immunological graft rejection, no need for a bone donor bank, and no special equipment (^{TSUCHIYA et al., 2010}).

The case report aimed to describe the techniques employed to preserve a limb with OSA through freezing the pedicle in liquid nitrogen and using chemotherapy. An eight-year-old, 33kg, male, Great Dane mix was attended with a history of claudication of the right pelvic limb over the past month. Physical examination showed a slight increase in volume at the distal diaphyseal region of the femur as well as muscle atrophy. OSA was diagnosed through X-ray and a biopsy (osteosblastic osteosarcoma).

The informed consent form was read and signed by the owner, and the patient was directed to limb preservation surgery. The animal was anesthetized and the limb was prepared for aseptic surgery. Antimicrobial prophylactics were administered intravenously (22mg kg^-1 of ampicillin sodium) 30 minutes before the surgery and every 2 hours during the perioperative period.

With the patient in the left lateral recumbency, the femur was approached through the craniolateral portal with an incision in the fascia lata and caudal retraction of the biceps femoris muscle as well as cranial retraction of the vastus lateralis. Exposure of the femur allowed osteotomy at the proximal diaphyseal region (at a distance of 2cm from the tumor border) with the use of a pneumatic oscillating saw. Following osteotomy, and after isolating the tumor region from the soft tissues, the bone marrow was scraped and the patient's limb was rotated towards the stainless steel bowl containing liquid nitrogen to create a pedicle frozen autograft. The tumor was completely immersed in liquid nitrogen at -196°C. The soft tissues were protected with gauze and surgical pads. The devitalization protocol was performed according to procedures outlined by ^{TSUCHIYA et al. (2005}), with the pedicle remaining in liquid nitrogen for 20 minutes, followed by incubation at room temperature for 15 minutes and then in distilled water for 10 minutes. After the devitalization procedure, all surgical instruments and pads were replaced and bone cement was used to refill the devitalized bone marrow cavity; osteosynthesis was then performed with the use of a dynamic compression plate and nine cortical screws (Figure 1). In the end of the surgery, the soft tissues were sutured using routine procedures.

 

Figure 1: Limb sparing of the distal femur in dog. Radiographic compatible with osteosarcoma of the distal femur (A). Following osteotomy and after isolating the tumor region from the soft tissues (B). After, to create a pedicle frozen autograft, the tumor was completely immersed in liquid nitrogen at -196°C (C). Osteosynthesis was then performed with the use of a dynamic compression plate and nine cortical screws (D). Radiographic control of the operated limb (E) After amputation of the limb (F).