Cranioplasty using castor oil–based polyurethane in a dog with Grade II multilobular osteochondrosarcoma

Abstract Multilobular osteochondrosarcoma is an uncommon tumour that affects the flat bones of the skull. Surgical removal of these lesions often results in large osseous defects that require reconstruction using conventional materials or metallic implants. Castor oil–based polyurethane appears to be biocompatible and nonimmunogenic; however, its osteointegrative properties remain uncertain. A 4‐year‐old Boxer dog was diagnosed with a Grade II multilobular osteochondrosarcoma located in the calvarium, along with a solitary pulmonary nodule. The tumour was removed by craniectomy, and the resulting osseous defect was repaired using castor oil–based polyurethane. Local tumour recurrence and enlargement of the pulmonary nodule were observed 5 months after surgery, despite chemotherapy. The survival time was 7 months. Computed tomography was useful for preoperative tumour characterisation, postoperative assessment of the polymer, and detection of pulmonary metastasis. This report demonstrates that cranioplasty using castor oil–based polyurethane cement may be an alternative option for the reconstruction of skull defects in small animals.