The Study on the Graft Materials of Bone Defect Reconstruction Surgery in Dogs

국문 초록 (Abstract)

본 연구에서는 실제 임상 사례에서 개의 치명적인 골 결손부를 재건한 환자의 후향적 연구를 통해 현재 수의 임상에서 일반적으로 사용되는 골 이식재를 평가한 후 합성 골 이식재를 제조하여 실제 임상에서의 적용 가능성을 평가하였습니다.
첫 번째 연구에서는 36마리의 골 결손부가 발생한 환자에서 동종 치밀골, 자가 해면골, 자가 치밀골, Hydroxyapatite를 수송체로 한 뼈 형성 단백질을 적용하여 환자의 상태에 맞는 수술을 실시하였고 방사선학적 평가와 임상적 파행 평가를 통해 유의적인 골 결손부 치유를 확인하였습니다.
두 번째 연구에서는 Poly(lactic-acid)를 FDM (Fused Deposition Modeling) 기술을 적용하여 3D 프린터를 통해 실제 뼈의 모양과 유사한 지지체를 제작하였고, 빈 공간을 Poly(lactide-co-glycolide)와 Hydroxyapatite를 혼합하여 제조한 나노섬유로 채워넣었습니다. 제조한 이식물을 12마리의 비글견의 인위적으로 만든 노뼈 골 결손부에 이식하였고 이식부에는 젤라틴과 뼈 형성단백질을 적용하였습니다. 이후 방사선학적 평가, 미세단층 촬영기를 통한 평가, 조직학적 평가를 통해 실제 뼈 형성이 얼마나 이루어졌는지를 확인하였습니다.
결론적으로, 본 연구에서는 현재 수의 임상에서 널리 쓰이는 골 이식재를 환자에 맞는 수술법과 함께 적용할 경우 좋은 예후를 보일 수 있다는 것을 확인하였습니다. 하지만, 이를 통해 골 이식재의 부피, 크기, 형태, 윤리적 문제 등의 한계를 재확인 하였으며, 새로운 골 이식재 제조 연구의 필요성을 환기시켰습니다. 또한 본 연구에서 시도한 새로운 합성 골 이식재 연구를 통해, 실제 임상 환자에게 적용할 이상적 합성 골 이식재의 연구에 지침이 될 수 있습니다. 실제 임상 환자에 대한 적용은 추가적인 연구를 통한 확인이 필요하며, 한계점을 보완한 개선된 골 이식재 연구를 기대할 수 있습니다.

다국어 초록 (Multilingual Abstract)

Healing of bone defect is bone tissue reconstruction process, which generally undergoes a multi-dimensional procedure with an overlapping timeline (Bhardwaj and Kundu. 2010). Most bone defects can heal spontaneously under adequate physiological environmental conditions due to the regeneration ability of bone.

However, large bone defects, also known as critical-sized bone defects pose a significant treatment challenge to orthopedic surgeons. These can result from a high-energy traumatic event, large bone resection for different pathologies such as tumor, treatment of infected or non-infected non-unions (en-bloc resection) and deformity correction. This may not heal spontaneously and lead to nonunion prognosis due to the size of defects or unstable biomechanical properties, unfavorable wound environment, suboptimal surgical technique, metabolic factors, hormones, nutrition, and applied stress. So helping measures are required for completion of healing process of such defect where various bone grafts and bone substitutes have been tried by several clinicians to healing of those large defects (Vertenten et al. 2010).

A bone graft is defined as an implanted material that promotes bone healing alone or in combination with other materials. The selection of an ideal bone graft relies on several factors such as tissue viability, size, shape, volume, biomechanical characteristics, graft handling, cost, ethical issues, biological characteristics, and associated complications (Minier et al. 2014). Grafts and other materials currently used for the treatment of orthopedic problem have selects advantages, but they are deficient in several aspects. The materials used in bone grafting in veterinary medicine can be divided into several major categories, including autografts, allografts, synthetic and biologically based, tissue-engineered biomaterials and combinations of two or more substitutes.
Inter alia, polymers have been tried in bone tissue engineering owing to their biocompatibility, design flexibility, surface modifiability, light weight, and ductile nature (Murugan and Ramakrishna. 2005, Salgado et al. 2004).

However, to the best of author’s knowledge, methods currently used to reconstruct the critical-sized bone defects in veterinary orthopaedics are neither satisfactory nor well established.

There, the purpose of this study is establishing the critical-sized bone defect reconstruction surgery with relatively available graft materials and confirm the limitations of the graft material and investigate the possibility of gelatin and rhBMP-2 instilled 3D printing PLA scaffold filled with PLGA/HA nanofiber for the repair of critically-sized segmental bone defects in a canine model.

Thus, the objectives of this study are divided into two parts; (1) Critical-sized Bone Defect Reconstruction in 36 Dogs: A Retrospective Analysis of Clinical Outcomes (2) Evaluation of a poly(lactic-acid) scaffold filled with poly(lactide-co-glycolide)/hydroxyapatite nanofibres for reconstruction of a segmental bone defect in a canine model.
First project, critical-sized bone defects were reconstructed in 36 dogs. Surgery was performed with conventional bone graft materials including cortical bone allogrft, cortico-cancellous bone autograft, rhBMP-2 impregnated hydroxyapatite and patient suitable fixation methods. Radiographs and degree of lameness were scored during follow-up period for evaluation of the clinical outcomes.
Second project, poly(lactic-acid) scaffold was fabricated by 3D-printer. Then, filled with poly(lactide-co-glycolide)/hydroxyapatite nanofibres that were fabricated by electrospinning. The experimental bone defects were made in a 20mm-long region of radius. The area of defect in ten beagle dogs were devided into 3 groups; defect not treated, scaffold filled with nanofiber, scaffold filled with nanofiber and instilled with rhBMP-2. Radiographs, histologic examination and micro-computed tomography were utilized to evaluate the bone regeneration after the experiment.

목차 (Table of Contents)

• CHAPTER 1
• General Introduction 1
• References 10
• CHAPTER 2 Critical-sized Bone Defect Reconstruction in 36 Dogs: A Retrospective Analysis of Clinical Outcomes 16
• Introduction 17
• Materials and Methods 21
• Results 35
• Discussion 46
• Conclusion 53
• References 54
• CHAPTER 3 Evaluation of a poly(lactic-acid) scaffold filled with poly(lactide-co-glycolide)/hydroxyapatite nanofibres for reconstruction of a segmental bone defect in a canine model 60
• Introduction 61
• Materials and Methods 63
• Results 74
• Discussion 82
• Conclusion 85
• References 86
• CHAPTER 4 89
• General Conclusion 90
• Abstract in Korean 93