RESUMEN
Aims: To identify the potential pitfalls and indicate procedures to prevent them, during the evaluation of biomaterials for orthopaedic and craniofacial research in the New Zealand White (NZW) rabbit animal model of femoral bone defects. Place and Duration of Study: Laboratory for Research of the Musculoskeletal System, School of Medicine, University of Athens, between June 2014 and July 2015. Materials and Methods: Pre-emptive analgesia (carprofen 2.2 mg/kg sc), chemoprophylaxis (enrofloxacin 10 mg/kg sc) and anaesthesia (ketamine/xylazine 30/5 mg/kg im) were administered to NZW rabbits (body weight 3.3±0.2 kg, mean ± SD) for the aseptic surgical creation of drilled bone defects of 6 mm diameter (“critical size defect”) in the external femoral condyle of the left limb. All rabbits recovered without post-surgical complications from the first postoperative day. Results and Discussion: Although the research group consisted of Veterinarians and Orthopaedic Surgeons with experience in this model, they were challenged with potential pitfalls which were overcome step by step. Among them is the precise localization of the defect to be drilled. Intra-operative palpation of the external femoral condyle assists in determining the site, and post-operative X-ray evaluation confirms it. Additionally the correct width and depth of the bone defect are important to adhere to, which was achieved by using a 5.5 mm diameter bone drill and observing its depth marks. Another challenge is to have the specific amount of biomaterial implanted confined to the defect. Its potential distribution in the femoral shaft, diffusion in the metaphysial trabecular bone or excessive covering of the bone surface, are also pitfalls to be avoided. Conclusions: The increased use of this animal model in the evaluation of biomaterials in orthopaedic and craniofacial research requires knowledge, skills, surgical accuracy and attention to a sequence of steps, in order to achieve homogenous results and high repeatability of the implantation technique. With the fulfillment of these conditions, the extraction of valid scientific results and reduction of the number of animals used are possible.
RESUMEN
Objective: Growth factors have been applied in maxillary sinus augmentation with clinically successful results. The purpose of this article is to evaluate the effectiveness of growth factors in combination with various synthetic scaffolds. Methods and Materials: A systematic review of studies examining the effects of synthetic materials in combination with growth factors were performed. Results: Twelve (1 human and 11 animal) studies were eligible for inclusion. Due to the great heterogeneity of the studies regarding design, materials and outcomes, a meta-analysis was not performed. The majority of the studies show a reduction in healing time and enhancement of bone formation within the subantral environment. Bone Morphogenetic Protein-2 and GDF-5 were the two most common osteoinductive factors studied, showing a significant effect on new bone formation. Moreover, initial outcomes of trials with stem cells genetic transformation, that results in increased production of growth factors, are positive and justify further research. Conclusion: The incorporation of growth factors into the synthetic scaffold may be beneficial regarding the healing process.