> ## Content Index > Fetch the complete content index at: https://www.theplasticsfella.com/llms.txt > Use this file to discover other available public pages before exploring further. # Bone Grafts - URL: https://www.theplasticsfella.com/bone-grafts/ - Published: 2022-06-08T10:22:11.000Z - Updated: 2025-05-05T11:11:44.000Z - Description: Bone grafts are biological scaffolds and support structures. They can be autografts (patient's own bone), allografts (from a donor) or alloplastic. This article details their indications, properties and types of grafts. - Author: PlasticsFella - Tags: Core Principles 👇 **In this Article** [5 Key Points](https://www.theplasticsfella.com/bone-grafts/#bone-grafts) [Indications for Bone Grafts](https://www.theplasticsfella.com/bone-grafts/#indications-for-bone-grafts) [Bone Graft Properties](https://www.theplasticsfella.com/bone-grafts/#bone-graft-properties) [Classification of Bone Grafts](https://www.theplasticsfella.com/bone-grafts/#classification-of-bone-grafts) [Autologous Bone Autografts](https://www.theplasticsfella.com/bone-grafts/#autologous-bone-autografts) [Alloplastic Bone Substitutes](https://www.theplasticsfella.com/bone-grafts/#alloplastic-bone-substitutes) [Bone Graft Healing & Incorporation](https://www.theplasticsfella.com/bone-grafts/#bone-graft-healing-and-incorporation) [Bone Graft Survival](https://www.theplasticsfella.com/bone-grafts/#bone-graft-survival) [Flashcards](https://www.theplasticsfella.com/bone-grafts/#flashcards) --- ## Bone Grafts 💛 **5 Key Points** 1\. Bone grafts are **autologous** (humans) or **alloplastic** (engineered) 2\. **Autologous** grafts are autografts (patient) or allografts (cadaver) 3\. They are incorporated through osteoinduction, -conduction, -genesis 4\. Cortical grafts support, and cancellous allow bone regrowth. 5\. Graft survival depends on type of graft, fixation and patient factors. --- ## Indications for bone grafts Bone grafts provide support, encourage bone regeneration and assist fracture healing. There is a diverse array of bone grafting indications. Generally speaking, bone grafts and their substitutes are used for: - Structural support by filling bone gaps secondary to trauma or resection - Improve healing of fractures with delayed or non-unions. - Assist in arthrodeses and spinal fusions --- ## Bone Graft Properties Bone grafts have one or more of the following properties: **osteoconductive**, **osteoinductive**, and **osteogenic**. The biological property of bone focuses on 3 areas - osteoconduction, osteoinduction and osteogenesis. This can be visualised in the image below ![Bone grafts have different amounts of osteoconduction, osteinduction and osteogenesis. There are the biologiical properties of bone and bone grafts](https://storage.ghost.io/c/a0/9f/a09fd7b4-d396-4b28-aed3-b87e20483292/content/images/2022/06/Bone-Graft-Characteristics.png) Bone Graft Characteristics **Osteoconductive** - Osteoconductive material is a structural framework for bone growth. - For example, demineralized bone matrices (DBMs) - More apparent in cancellous bone grafts. **Osteoinductive** - Osteoinductive material stimulates osteogenesis and induces stem cells - For example, bone morphogenetic protein (BMP) arises from the TGF-B family. **Osteogenic** - Osteogenic material provides bone-producing cells (mesenchymal stem cells, osteoblasts, and osteocytes) to produce more bone. - For example, an autologous bone graft is the only bone graft that contains live mesenchymal precursor cells 💡 **Fun Fact:** cancellous bone has a greater ability than cortical bone to form new bone due to its larger surface area --- ## Classification of Bone Grafts There are several different ways to classify the different types of bone grafts. This image below provides a comprehensive review. ![Bone grafts can be autologous, alloplastic, cortical and cancellous](https://storage.ghost.io/c/a0/9f/a09fd7b4-d396-4b28-aed3-b87e20483292/content/images/2022/06/Classification-of-Bone-Grafts.png) Classification of Bone Grafts 💡 **Tip:** Autografts can be further subclassified into vascularised and non-vascularised. --- ## Autologous Bone Autografts ### Autologous bone autografts are cortical, cancellous or corticocancellous bone from the patient that can be vascularised and non-vascularised. They retain all biological properties of bone. ### Indications Bone Autografts are **indicated** in bone defects <6cm and: - Well-vascularized bed - Adequate soft tissue cover - Absence of infection ### Biological Properties Bone Autografts are considered the "gold standard" because of their **biological properties**: - Osteogenic **and** osteoinductive **and** osteoconductive properties. - Less immunogenic than other options. ### Types of Autografts Autografts can be cortical, cancellous or a combination. Each option has its own limitations and advantages. Generally speaking, cortical is used when large defects require structural support. **Cortical Bone Grafts** - Less biologically active than cancellous - More structural support than cancellous. - Slower incorporation due to remodelling of Haversian canals (up to 2 months) - Heals primarily by osteoconduction. **Cancellous Bone Grafts** - An osteoconductive 3D scaffold with minimal structural support - A high number of osteoblasts and growth factors. - Rapid incorporation via creeping substitution (within 2 weeks) - Heals primarily by osteogenesis. ### Donor Sites **Donor** site options for autografts include: - Iliac Crest - commonly used and can give cancellous and cortical bone - Fibula - for a vascular autograft (example - fibula graft with peroneal artery) - Ribs - for vascular autografts. - Distal radius - Bone marrow aspirate 💡 **Tip**: Autografts are considered the "gold standard". They can be cortical, cancellous or a combination. **Bone Allografts** Allografts are bone grafts from a (cadaver) donor that can be fresh, freshly frozen or freeze-dried bone derived from a donor. Bone allografts are osteoconductive **only** due to a lack of viable cells. It is limited by its immunogenicity. 💡 **Tip**: Autografts are considered the "gold standard" of bone grafting. --- ## Alloplastic Bone Substitutes There is an array of "synthetic" and "engineered biological" bone substitutes that provide structural support. Alloplastic bone substitutes have a primary role in support. They are primarily osteoconductive with little osteogenic or osteoconductive properties Here are a few examples: - **Demineralised bone matrix** has an osteoinductive and osteoinductive capacity without structural support. It contains collagen, bone morphogenetic proteins, transforming growth factor-beta, residual calcium but does not contain mesenchymal precursor cells. - **Calcium Hydroxyapatite:** brittle but limited resorption. - **Methylmethacrylate (MMA)**: non-resorbable, high density, "bone cement", structural support with osteoconductive properties only. - **Bone morphogenetic proteins (BMP):** osteoinductive only 💡 **Tip**: Alloplasts vary in their osteoconduction, inductive properties, and resorption rates. --- ## Bone Graft Healing and Incorporation Autologous bone grafting incorporates through 3 main mechanisms: **osteoconduction**, **osteoinduction**, and **osteogenesis.** After haematoma formation and an initial inflammatory period, in which necrotic debris stimulates chemotaxis, bone grafts become incorporated into their new bony surroundings. In a similar way, skin grafting becomes [adherent](https://www.theplasticsfella.com/skin-grafts/#stages-of-skin-graft-healing) to a wound bed. This is visualised in the image below. It is different from the [standard bone healing process](https://www.theplasticsfella.com/bone-healing/). ![a bone graft healings and incorporates into the recipient bed through osteoconduction, osteoinduction and osteogenesis](https://storage.ghost.io/c/a0/9f/a09fd7b4-d396-4b28-aed3-b87e20483292/content/images/2022/06/bone-graft-incorporation-and-healing.png) Bone Graft Incorporation - Osteoconduction, Induction and Genesis ### Osteoconduction - The **bone graft** acts as a scaffold for bone growth via creeping substitution - It provides a matrix for bone growth that enables a blood supply and osteoprogenitor cells to survive. - Occurs in cortical bone, calcium hydroxyapatite, and less so in cancellous bone. ### Osteoinduction - Bone graftgrowth factors stimulate osteogenesis in the **host tissue**. - Osteocytes are formed from the differentiation of the recipient site's mesenchymal cells - Strongly influenced by BMPs. - This process is seen in cancellous bone grafts and demineralised bone matrix ### Osteogenesis - Osteoblasts that survive in the bone graft directly produce new bone. - A faster process in vascularized bone grafts as they do not undergo creeping substitution. - Occurs primarily in vascularized bone grafts and cancellous bone. 💡 **Definition:** Creeping substitution is the osteoclastic resorption of dead bone from the allograft and its replacement by new living bone made by osteoblasts from the host. --- ## Bone Graft Survival Bone grafts are similar to [skin grafts](https://www.theplasticsfella.com/skin-grafts/#skin-graft-failure) in that they are influenced by patient factors, graft factors and the recipient site. ### Patient Factors A medically optimised patient will always have a better outcome for their bone grafts. For example, diabetes control, smoking cessation and adjusting immunosuppression drugs. ### Graft Factors When it comes to the graft, there are so many variables that can have a positive and negative influence on its healing. Here are some key points: 1. **Type of Bone Graft** - **Periosteum** on bone grafts reduces the amount of resorption. - **Cancellous bone grafts are** more readily revascularized than cortical. **2\. Inset of Bone Graft** - **Orthotopic**: if the graft is placed in a normal bone location then there will be less bone resorption. - **Fixation**: bone graft fixation improves survival. - **Quality of recipient:** infection and radiotherapy reduce graft survival. 💡 **Fun Fact:** A bone graft is considered to be incorporated when there is no abrupt histological change between the host bone and the graft --- ## Flashcards ⚡ Evidence-based flashcards are designed for active recall and spaced repetition of the verified information you are currently studying. They are continually updated and are for thePlasticsPro users. ---