The aim of this study was to describe the diagnosis and treatment of grade IV lateral patellar luxation (LPL) in two adult large breed dogs with complex femoral deformities using patient-specific three-dimensionally (3D) printed osteotomy guides and implants. Computed tomography (CT) scans were obtained for virtual surgical planning (VSP) using computer-aided design (CAD) software, which allowed for 3D reconstruction and manipulation of the femoral deformities, providing a preoperative view of the correction. Of the two patients, one was affected bilaterally and the other unilaterally, but both dogs were from the same litter. Therefore, the healthy femur of the unilaterally affected patient was used as the physiological reference for the virtual surgical correction. Three distal femoral trapezoid osteotomies (DF-TO) followed by reduction and internal fixation with plates were performed using patient-specific 3D-printed osteotomy guides and implants. This type of osteotomy permitted correction of procurvatum in all the femurs to increase knee extension, raise the dog’s lumbar spine and correct the kyphosis. Preoperative, expected and postoperative femoral angles were compared to evaluate the efficacy of virtual surgical planning and the outcome of surgical correction. Radiographic follow-up, passive range of motion and functional recovery were recorded. There were no major complications requiring revision surgery. Significant clinical improvement was observed in both patients. This study suggests that the treatment used represents a viable surgical alternative to restore limb alignment in patients with complex femoral deformities.

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.

Canine appendicular osteosarcoma (OSA) is typically managed by limb amputation. However, this approach may be suboptimal in dogs with concurrent osteoarthrosis (OA). Limb-sparing surgery using three-dimensional (3D)-printed patient-specific implants (PSIs) may be an alternative, although evidence on implant durability and revision strategies remains limited, in particular for proximal humeral reconstructions. This report describes a 9-year-old, overweight dog referred for a 4-week history of persistent left forelimb lameness. Computed tomography (CT) confirmed a lesion affecting the proximal humerus and severe bilateral hip OA. Fine-needle aspiration cytology supported a presumptive diagnosis of OSA. Limb-sparing surgery with 3D-printed PSIs was chosen instead of amputation due to overweight status and OA. Patient-specific guides (PSGs) and endoprosthesis (PSE) were designed based on preoperative CT. Histopathology of the resected tumour confirmed OSA with complete surgical margins. Postoperative functional recovery was favorable, with progressive return to weight-bearing and mild residual lameness up to 8 months. At 9 months, implant failure occurred due to fracture at the distal humeral fixation region. Revision surgery was performed using a novel 3D-printed modular PSE integrating the retained proximal component, allowing restoration of limb function for an additional 6 months. The dog was euthanized at 15 months due to pulmonary metastases. Post-mortem macroscopic and histological visual semi-quantitative assessment of peri-implant tissue suggested advanced osseointegration, with no local recurrence or infection. This report suggests that PSI-based limb-sparing reconstruction may be feasible in proximal humeral OSA and highlights mechanical fatigue as a key limitation. The modular revision approach suggests the potential of additive manufacturing for salvage strategies after implant failure.