BONE GRAFTS IN SPINAL FUSION

Bone Grafts Provide Support

A bone graft refers to a supporting structure. Rather than crush the bone into fine pieces, larger pieces of bone fill gaps or voids between two bones. For example, if the surgeon removes a vertebra or disc, he or she may place a chunk of bone graft into the empty space. To clarify, the hard or rigid bone will hold the bones apart while the body grows to the ends of the graft. Over time, the entire piece of bone that was grafted will become “remodeled” and replaced by the body with new bone. Also, the time it takes to fuse depends on the size of the piece of bone that was used. Despite taking a long time to completely heal — a slow process works and may take several years.

Understanding Bone Graft Substitutes and Their Comparison to Real Bone Grafts

Bone graft substitutes are specially designed materials that aim to replicate the benefits of traditional bone grafts, such as human bone autografts and allografts, but with fewer potential side effects. These substitutes are instrumental in procedures like spinal fusion and are used in millions of surgeries globally each year.

Types of Bone Grafts

Demineralized Bone Matrix (DBM)

• Composition and Function: DBM is derived from donor bone with its mineral content removed, leaving behind growth-stimulating proteins such as collagen and growth factors.
• Forms and Uses: Available as powder, granules, putty, gel, or chips, DBM is known for its versatility. It’s often combined with other grafts due to its inability to solely support bone fusion.
• Advantages: Processed to minimize disease transmission risks, making it a safer option in terms of infection control.

Ceramic-Based Substitutes and Synthetic Bone Graft Extenders

• Composition and Function: These include materials such as calcium sulfate, calcium phosphate, and other ceramics. Their makeup is similar to that of natural bone.
• Benefits: Free from disease transmission risks, non-toxic, easy to sterilize, and technicians can mold the material into various shapes and sizes.
• Limitations: Lack inherent strength and cannot independently stimulate bone growth. They usually act as scaffolds for new bone growth.

Bone Morphogenetic Proteins (BMPs)

• Natural Production: BMPs are naturally occurring proteins in the body that encourage bone healing by converting stem cells into bone cells.
• Medical Use: Genetically engineered BMPs are now available, reducing adverse reactions compared to other graft substitutes.
• Considerations: While promising, BMPs require the surgeon’s expertise due to potential risks, and surgeons must use them in conjunction with structural agents like other grafts or substitutes.

Comparison to Real Bone Grafts

• Human Bone Autografts and Allografts: The most common bone grafts involve transplanting a patient’s own bone (autograft) or using donor bone (allograft). These methods are effective but come with risks like infection or disease transmission.
• Bone Graft Substitutes:
• Safety: Generally safer in terms of disease transmission.
• Versatility: Available in multiple forms and adaptable to various surgical requirements.
• Effectiveness: Often needs other grafts due to limitations in strength and self-stimulation capability.

Final Thoughts

Bone graft substitutes offer a promising alternative to traditional grafts with specific advantages and limitations. While they reduce some risks associated with real bone transplants, they often require combination approaches to achieve the desired therapeutic outcomes in bone healing and fusion. Selecting the right type of graft or substitute depends on the specific medical situation, and expert spine surgeons, like those at the Scoliosis and Spine Institute should determine the type.

Understanding Ceramic-Based Substitutes and Synthetic Bone Graft Extenders

Ceramic-based substitutes and synthetic bone graft extenders are innovative materials used in orthopedic surgery to promote bone regeneration. Mimicking the properties of natural bone, these substitutes are crafted from materials like ceramics, calcium sulfate, and calcium phosphate. Their primary role is to act as scaffolds where new bone cells can grow, eventually dissolving as the natural bone takes over.

Benefits

• Safety: One of the standout benefits is the zero risk of disease transmission, a significant concern with other types of bone grafts.
• Biocompatibility: These materials are nontoxic and can sterilizing them to ensure they are safe for implantation is easy.
• Versatility: Technicians can mod thm into various shapes and sizes to fit different surgical needs.
• Support for Growth: They provide a reliable framework, aiding in new bone formation.

Drawbacks

• Limited Strength: Their primary limitation is their inherent weakness compared to natural bone or some other graft materials.
• Cannot Independently Stimulate Growth: While they offer structural support, they cannot stimulate bone growth on their own and need the body’s natural bone-forming processes to complete the regeneration.

In summary, while ceramic-based and synthetic bone graft extenders bring significant safety and versatility advantages, their lower strength and inability to independently encourage bone growth present some limitations. Understanding these benefits and drawbacks is essential for determining their suitability for different orthopedic applications.

Bone Graft Types

Medical companies provide several different kinds of bone graphs.  The following identify them.

Autografts:

Surgeons consider Autografts as the gold standard for bone grafting in spinal fusion surgery. These grafts use bone from the patient’s own body, typically from the iliac crest (hip bone). Therefore, autografts provide live bone cells, growth factors, and proteins necessary for bone regeneration. Furthermore, this type of graft maintains a high success rate and promotes efficient fusion. However, the main drawback is the need for an additional surgical site, which can cause discomfort and potential complications.

Allografts:

Allografts involve using bone tissue obtained from a cadaveric donor. Meanwhile, this type of bone graft eliminates the need for an additional surgical site, reducing patient discomfort. Allografts undergo extensive processing and sterilization to minimize the risk of disease transmission and rejection. Lastly, they provide a structural framework for bone regeneration and help promote fusion. However, they lack the live cells and growth factors found in autografts, which may slightly impact the fusion process. Occasionally, surgeons use allografts to supplement autografts or in situations where doctors do not use an autograft.

Understanding Graft Composites in Spinal Fusion Surgery

What Are Graft Composites?

Graft composites are specialty materials used in spinal fusion surgery to promote effective bone healing and fusion. These composites combine different substances to mimic the natural components and properties of bone, ensuring optimal conditions for new bone growth.

Types of Graft Composites

Graft composites often include:

• Collagen and Ceramic: This mixture replicates the natural structure of bone, providing a scaffold that supports new bone formation.
• Demineralized Bone Matrix (DBM) and Bone Marrow Cells: DBM contains growth factors that stimulate bone growth, while bone marrow cells offer a natural source of stem cells that can develop into new bone cells.
• Bone Morphogenetic Proteins (BMP) and Ceramics: BMPs are growth factors known for their ability to induce bone formation, and ceramics act as a supportive matrix.

Usage in Spinal Fusion Surgery

In spinal fusion surgery, these graft composites are strategically placed at the fusion site. Here’s how they function:

• Structural Support: The composite materials provide a robust framework that maintains spinal stability during the bone fusion process.
• Biological Activation: Components like BMP and DBM actively promote the body’s natural bone-healing mechanisms.
• Stem Cell Contribution: Bone marrow cells in the composite can transform into bone cells, directly contributing to new bone growth.

Advantages of Using Graft Composites

• Enhanced Fusion Rates: By combining materials that directly support bone growth, these composites improve the likelihood of successful spinal fusion.
• Reduced Recovery Time: The natural-like properties of graft composites facilitate quicker integration and healing.
• Versatility: Various combinations enable customization based on the patient’s specific needs and surgical goals.

Conclusion

Graft composites play a crucial role in spinal fusion surgeries by combining structural and biological elements to support natural bone healing. Understanding their composition and function helps in appreciating their significance in achieving successful spinal fusion outcomes.

Synthetic Bone Grafts:

Synthetic bone grafts mimic the properties of natural bone. Generally, these grafts contain materials such as ceramics, calcium phosphate, or calcium sulfate. Nevertheless, synthetic grafts provide a framework for new bone growth and gradually resorb over time as the patient’s own bone takes its place. Overall, they eliminate the need for harvesting bone from the patient or relying on cadaveric donations. Lastly, synthetic grafts have the advantage of consistent quality, reduced risk of disease transmission, and availability. However, they may take longer for fusion to take place as compared to autografts or allografts, and doctors continue to study their long-term effectiveness.

Bone Morphogenetic Proteins (BMPs):

Bone morphogenetic proteins (BMPs) are a group of naturally occurring proteins that play a critical role in bone formation and healing. Surgeons can use these as an alternative or in combination with traditional bone grafts. The production of BMPs get produced through genetic engineering and are available in synthetic forms. For this purpose, they seem highly potent in promoting bone growth and fusion. However, Surgeons reserve BMPs for specific cases because of potential complications, such as inflammation and excessive bone growth.

New Technology for a Bone Graft

Medical research continues to design bone graft substitutes, chemicals, and devices that stimulate the bones to fuse. Furthermore, electrical current stimulates bone to grow, so surgeons use electrical stimulation devices to speed up a fusion. In addition, some artificial bone graft materials have been developed. For instance, sea coral, harvested from the oceans, sometimes provides a successful structural bone replacement. Other developments include:

• Demineralized bone matrix (DBM): Developed from cadaver bones in a bone bank. Calcium gets removed from the bone turning the material into a putty, sheet, or gel. Surgeons can then add the material to a graft site to improve the fusion. Demineralized bone matrix (DBM) is allograft bone that has had its mineral content (calcium) removed. What’s left in the bone are protein-based growth-stimulating substances, such as collagen, proteins, and growth factors. DBM comes in a variety of forms—powder, granules, putty, gel, chip—and its processed nature makes it low risk from a disease transmission perspective. However, DBM isn’t strong enough to promote bone fusion by itself, so it’s typically combined with other grafts.
• Autologous Growth Factor (AGF): A solution used to stimulate bone growth. Developed in a laboratory from blood platelets (the clotting part of the blood). The mixture is usually used in combination with some form of structural support, such as autograft or fusion cages.
• Bone Morphogenic Protein (BMP): A chemical added to bone graft to enhance bone growth when added to a fusion site.

Researching Bone Graph Research

In addition to these established methods, researchers are exploring several emerging technologies that could revolutionize bone graft substitutes in the future. According to a review in the World Journal of Orthopedics, notable areas of promise include:

• Bone marrow-derived mesenchymal stem cells: These have shown significant potential in bone healing properties.
• Gene therapy: This advanced technique is being researched for its efficacy in promoting bone growth and healing.
• Tissue engineering: A promising field that could lead to new, more effective bone graft substitutes.

At this stage, these emerging technologies have primarily demonstrated their potential in animal studies. However, they offer a glimpse into what might be possible for spinal fusion bone grafting in the near future. Combining these forward-looking innovations with the existing, proven methods provides a comprehensive view of the current and future landscape in bone graft technology.

What Are the Differences Between Real Bone, Bone Graft Substitutes, and Stem Cell Modifiers?

When considering options for bone grafts, it’s crucial to understand the distinctions between real bone, bone graft substitutes, and stem cell modifiers like bone morphogenetic proteins (BMPs). Each has unique characteristics and applications, especially in spinal fusion surgeries.

Real Bone

A real bone refers to either autograft or allograft:

• Autograft: This is bone harvested from your own body, commonly from the hip or another bone site.
• Allograft: This is donated bone sourced from a cadaver.

Real bone, especially autograft, is highly effective due to its natural compatibility and lack of immune response. However, it involves an additional surgical procedure for harvesting, which can extend recovery time and increase infection risks.

Bone Graft Substitutes

Bone graft substitutes are synthetic or natural materials designed to replicate the bone’s structure and function without some of the downsides. These can include:

• Ceramics: Materials like calcium phosphates that support bone growth.
• Polymer-based substances: These act as a scaffold for new bone formation.
• Composites: A mix of ceramics and polymers for enhanced properties.

In addition, bone graft substitutes are popular due to their availability and reduced need for donor material. However, they may not integrate as seamlessly as real bone, though they eliminate the need for additional surgery to harvest donor bone.

Stem Cell Modifiers (BMPs)

Stem cell modifiers, specifically bone morphogenetic proteins (BMPs), play a pivotal role in bone healing and regeneration:

• Natural Function: BMPs are naturally occurring proteins in your body that stimulate stem cells to turn into bone cells.
• Synthetic BMPs: Advances in biotechnology have allowed for the genetic engineering of BMPs, making them more widely available for clinical use.

BMPs have the potential to reduce adverse reactions found with other graft types and encourage quicker bone healing. However, their use needs careful consideration. Surgeons must have specific experience with BMPs due to potential risks and “off-label” use, meaning they might be used for purposes not officially approved.

Summary

• Real Bone: Autografts (from your body) and allografts (from donors) are commonly used for their natural effectiveness but come with drawbacks like additional surgery and possible immune responses.
• Bone Graft Substitutes: Synthetic options mimic bone but may not integrate as well. They avoid the need for harvesting donor bone.
• Stem Cell Modifiers: BMPs enhance natural bone healing and can mitigate complications. However, they require careful and experienced application due to potential risks.

Understanding these differences can help in making informed decisions about the best bone grafting option for your needs.

How Does a Spine Surgeon Stimulate Bone Fusion During Spinal Fusion Surgery?

During spinal fusion surgery, a spine surgeon stimulates bone fusion by using a specialized technique involving bone grafts. These bone grafts are essentially small pieces of bone that are placed in the affected area to encourage new bone growth.

Key Steps in Bone Fusion:

• Bone Graft Application: The surgeon places the bone graft material at the site where fusion needs to occur.
• Biological Process: The graft materials act as a scaffold. They stimulate the body’s natural healing process, encouraging living bone cells to grow and bridge the gap between the vertebrae.
• Stability: To provide additional support and ensure successful fusion, hardware such as screws, rods, or plates may be used to hold the spine in place while the new bone develops.

This method effectively “tricks” the body into generating new bone tissue, leading to the fusion of the targeted spinal segments. Through this carefully orchestrated biological process, the spine gradually becomes more stable, reducing pain and improving function.

Conclusion:

Bone grafts play a vital role in facilitating successful spinal fusion procedures. Based on the patient’s condition, surgeons have autografts, allografts, synthetic bone grafts, and BMPs as graft options. Each type has its advantages and considerations. The choice depends on various factors, including the patient’s condition, the extent of fusion required, and the surgeon’s preference and expertise. Patients should consult with an experienced orthopedic surgeon to determine the most suitable bone graft option for each individual case, ensuring optimal fusion and successful long-term outcomes.

The Reasons Why Patients Choose the Southwest Scoliosis and Spine Institute.

• Spine expertise: The team of specialists at Southwest Scoliosis and Spine Institute is comprised of spine experts.  They specialize in the diagnosis and treatment of spinal conditions, ensuring the best possible care for their patients.
• Cutting-edge technology: Our practice uses the latest technology and techniques to diagnose and treat a wide range of conditions.  In addition, we use minimally invasive procedures that reduce pain and promote faster recovery.
• Comprehensive care: Our practice offers a full range of services, from diagnostic imaging and physical therapy to surgery.  We ensure that patients receive complete, seamless care for their spinal conditions.
• Dedicated facilities: Southwest Scoliosis and Spine Institute provides patients with a safe and comfortable environment.

Finally, our board-certified physicians and fellowship-trained orthopedic surgeons use the full range of treatments to treat their spine patients. Southwest Scoliosis and Spine Institute with offices in Dallas, Plano, and Frisco, Texas offers cutting-edge technology, comprehensive care, and dedicated facilities to ensure the best possible care for their patients. Get in touch with us today to schedule an appointment.

____________________

Medtronic: Bone Graft Types