Mandibular Reconstruction With a Patient-Specific Implant Following Surgical Excision of an Acanthomatous Ameloblastoma in a Dog

Abstract

Canine acanthomatous ameloblastoma (CAA) is an invasive benign epithelial odontogenic tumour most commonly affecting the mandible of large breed dogs. To the author's knowledge, this report describes the first computer-aided design patient-specific implant (PSI) that has been placed for a critical sized bone defect in mandibular reconstruction of a dog in the UK. The aim was to restore mandibular stability using a regenerative approach combining a titanium locking plate and compression-resistant matrix infused with recombinant human bone morphogenetic protein-2 (rhBMP-2) to bridge the 85 mm mandibular defect created by a segmental mandibulectomy. A 7-year-old neutered crossbreed dog with a focal 60 × 45 × 30 mm³ mildly ulcerated mass on the left mandible was presented. Histopathology confirmed a CAA. A left segmental mandibulectomy was followed by a delayed (secondary) reconstructive surgery. The porous titanium scaffold was manufactured from the first computed tomography (CT) scan and was designed with a channel to be filled with a compression-resistant osteoconductive resorbable sponge material infused with an osteoinductive solution containing rhBMP-2. Follow-up CT scans were performed on the day of the second surgery, and 4 and 12 months after the second surgery. Filling the porous titanium scaffold with an osteoconductive strip mixed with rhBMP-2 promoted bone remodeling and stimulated partial osseous integration of the implant; however there was no evidence of complete osteosynthesis bridging the bone defect as initially expected. Twelve months after reconstruction, dorsal longitudinal implant exposure necessitated PSI explantation. This study reflects a recent surgical therapeutic approach that can be utilised to reconstruct mandibles. PSIs can help reduce the known postoperative complications inherent to large gap mandibulectomies. Therefore, their use has the potential to improve patient welfare by restoring mandibular and temporomandibular joint (TMJ) stability, preventing mandibular drift, improving prehension, and reducing the risk of secondary TMJ degenerative disease and pain. It is likely that some implant design refinement is required to achieve better success rates for these challenging cases.