Limb-Sparing Surgery and Stifle Arthrodesis Using Patient-Specific 3D-Printed Guides and Endoprosthesis for Distal Femoral Chondrosarcoma in a Dog: A Case Report.

Limb-sparing techniques for appendicular primary bone tumors are still associated with a high rate of complications. Three-dimensional (3D)-printed patient-specific instruments could reduce these complications. The aim of this study is to describe a limb-sparing surgery using 3D-printed patient-specific guides (PSGs) and an endoprosthesis (PSE) to treat femoral chondrosarcoma in a dog. An eight-year-old female Golden Retriever presented with persistent lameness of the right hind limb, reluctance to move and difficulty in maintaining a standing position. Palpation of the right femur revealed an approximately 4 cm painful lesion. Cytological analysis of the needle aspiration supported the clinical and radiological suggestion of a cartilaginous bone neoplasm. Computed tomography (CT) scans suggested the presence of an aggressive lesion on the right distal femur. CT scans of the femur and tibia were then reconstructed using a bone tissue algorithm and processed with computer-aided design (CAD) software, which allowed for performing virtual surgical planning (VSP) and the fabrication of both the PSG and the PSE. Anti-inflammatory drugs and monoclonal antibodies were used for pain management while waiting for surgery. Adjuvant chemotherapy was also administered. An ostectomy of the distal third of the femur to completely remove the tumor was performed with the designed PSG, while the bone defect was filled with the designed PSE. Histopathological examination of the osteotomized bone segment confirmed a grade 2 central chondrosarcoma. There was no excessive tumor growth during the 28 days between the CT scans and surgery. Both PSG and PSE fitted perfectly to the bone surfaces. PSG eliminated the need for intraoperative imaging and ensured a faster and more accurate osteotomy. PSE optimized load sharing and eliminated the complications of the commercial endoprosthesis, such as incongruity and the need for manual intraoperative adjustment. Overall, the use of VSP, 3D-printed PSG and PSE significantly reduced surgical time, risk of infection and intra- and postoperative complications.