Application of Novel Biomaterials to Enhance Bone Regeneration in a Canine Non-Union Olecranon Fracture

Abstract

Simple Summary A "non-union" fracture is a broken bone that does not heal over a long period of time, regardless of whether surgery was performed or not. This type of fracture is very difficult to treat because the bone is both unstable and loses its ability to repair itself. In this report, we describe the treatment of a small dog that had lived with an untreated elbow fracture for two years. The dog could not use the forelimb and had severe stiffness and weakness. Surgeons used three-dimensional computer modeling to plan the operation and chose the most suitable plate to hold the bone together. In addition to fixing the bone with surgery, a new material made of very small, thin, leaf-stacked structures of polycaprolactone was placed into the fracture. These particles were combined with recombinant human bone morphogenetic protein-2 that stimulate bone growth and with stem cells, which are special cells that can develop into new bone. Over the following months, the dog regained the ability to walk normally and the bone healed, as shown on follow-up X-rays. This case shows that combining precise surgery with innovative biological materials can restore limb function in difficult cases, offering promise for animal health care.Abstract A six-year-old, neutered male Pomeranian weighing 4.25 kg was presented with a two-year history of non-weight-bearing lameness of the left thoracic limb following an untreated traumatic olecranon fracture. Orthopedic examination revealed markedly reduced elbow joint range of motion and muscle atrophy. Radiographs demonstrated a distinct fracture line with proximolateral displacement of the olecranon fragment. Preoperative computed tomography (CT) and three-dimensional (3D) reconstruction were used to establish the surgical plan and to pre-contour a locking plate. Surgical treatment was performed in sequential steps, including removal of scar tissue, reopening of the bone marrow channel, and internal fixation. Considering the compromised biological environment of a chronic non-union, a bioactive graft composed of porous leaf-stacked structure (LSS) polycaprolactone particles incorporating recombinant human bone morphogenetic protein-2 (rhBMP-2) and mesenchymal stem cells (MSCs) was applied in combination with plate-screw fixation. The patient showed progressive improvement after surgery, achieving full weight-bearing and restoration of elbow joint motion comparable to the contralateral side. Follow-up radiographs and CT confirmed fracture union, and the radiolucency of the LSS scaffold enabled precise monitoring of bone healing. This case highlights the potential utility of combining patient-specific surgical planning with sustained delivery of rhBMP-2 and MSCs using LSS particles for the management of chronic non-union fractures in small animals.