What is bone graft?
There are a variety of places that this bone graft can come from:
Your own body, called Autograft
Bone from another person, which has been cleaned, tested as safe and prepared for use, called Allograft
Bone products from an animal such as a pig or cow, called Xenograft (very rarely used)
Manufactured bone products, commercially produced as synthetic alternatives to human bone, called Bone Graft Substitutes
Why may it not be possible to use my own bone (Autograft) as a graft, and why may my surgeon choose to use a bone graft substitute?
You may not have good quality bone. This may be why you require a bone graft in the first place. For a graft to be effective it needs to provide a solid framework or scaffold for new bone to grow into, and for the biological factors which induce new bone growth to do their job
You may already be undergoing a long and possibly painful surgical procedure. The use of Autograft (graft from your own body) will often require a second surgical procedure and wound. This will cause you additional discomfort and prolong your surgery and recovery
You may need a large amount of bone graft, for example in repair of a failed joint replacement (revision arthroplasty). In this case it would be impossible to harvest enough bone from your own body, and so alternative sources of bone are required
Allograft bone (bone graft from another person)
In many situations where it is not possible to use Autograft, your surgeon may choose to use Allograft bone (from another person). The advantage of using Allograft bone is that it obviously has the correct chemical and structural composition to encourage new bone growth in your body. Allograft bone is normally from dead people who have volunteered prior to death to donate their bone, or from bone harvested during other surgical procedures, for example bone removed during hip or knee replacement surgery. This bone is then taken to a bone bank, where the bone is cleaned, tested for infection, prepared for future use and stored. However, due to the possible risks of infection from the bone donor (allograft is tested for HIV, Hepatitis, CJD and a large number of other possible infective agents), and the need for very good quality bone, supplies of allograft bone are limited.
Where Autograft or Allograft are not possible to use, or you or your surgeon have decided not to use them, there are a number of synthetic bone graft substitutes available as alternatives to human bone graft.
What are bone graft substitutes?
Bone graft substitutes are commercially produced synthetic products that mimic human bone. They are a safe and proven alternative to Autograft (your own bone) and Allograft (bone from another person). They provide a suitable environment for your body to repair or produce its own bone, either replacing the substitute over time with new bone, or combining with the bone graft substitute to form a very strong repair.
Bone graft substitutes can be manufactured to provide distinct advantages to human bone, such as:
100% free from all risk of possible human infective agents
Stronger than human bone, allowing earlier mobilisation and shorter hospitalisation following surgery
Reliable availability, ensuring enough bone is available for your operation
Reliable quality
More predictable response in your body in terms of new bone growth
Bone graft substitutes should provide properties similar to those of human bone:
Strength to enable movement, function and protection of your body
Porosity. Bone is porous, containing a variety of sizes of pores to allow movement of body fluids, bone growth factors and to provide channels for blood vessels and other structures
Biological compatibility. It is important that any substitutes are made of materials that are compatible with your body's own bone, in order to ensure that your body accepts the new material
Catalysts to bone growth. Where possible bone graft substitutes should provide substances that stimulate or encourage new bone formation. This could be through the ability to add other bone growth factors or your own bone marrow or blood to the substitute
How do bone graft substitutes work?
This can be achieved in different ways; hence there are different types of bone graft substitutes for you and your surgeon to choose from:
Products which provide structural support and conduct bone growth initiated by your own body
Products which induce or initiate new bone growth themselves
Products which contain stem cells, the cells from your body which produce new bone
Products which are a combination of the above three options
What types of bone graft substitute products are available?
Calcium Phosphate products
Modern bone substitute products. Different types of these are available:
Hydroxyapatite (HA) products: These can be made from naturally occurring materials, such as the skeletons of very small sea creature, or from coral.
Alternatively, Hydroxyapatite (HA) can be manufactured synthetically to give a predictable and ideal porosity for bone growth, and an enhanced strength for quicker recovery and return home after surgery, and a predictable and steady rate of absorption to work in tandem with your body as the HA is replaced by your own bone. An example of a synthetic HA product is ApaPore from ApaTech. Manufactured products normally offer better handling characteristics for your surgeon, making the operation easier.
Alternatively, Hydroxyapatite (HA) can be manufactured synthetically to give a predictable and ideal porosity for bone growth, and an enhanced strength for quicker recovery and return home after surgery, and a predictable and steady rate of absorption to work in tandem with your body as the HA is replaced by your own bone. An example of a synthetic HA product is ApaPore from ApaTech. Manufactured products normally offer better handling characteristics for your surgeon, making the operation easier.
Learn more about Hydroxyapatite and bone
Tri-Calcium Phosphate: Similar to Hydroxyapatite, however with less structural strength, faster absorption and generally a less predictable porosity and handling characteristics.
Glass ceramic products: Bone graft substitutes that are not absorbed by your body. For use if you cannot grow enough of your own bone, or if your bone is of very poor quality and the site for bone grafting is critical for taking large loads to enable you to move around. Not porous.
Demineralised bone matrix
Human or bovine (from cows) bone product, which is the substance left after bone has all the minerals (which provide structural strength and porosity) removed by acid. Usually combined with another product to provide structural support and porosity.
Collagen products
The protein in bone that provides elasticity. Derived from human or bovine (cows) sources. Normally combined with another product to provide structural strength.
Bone growth factors
Are bone graft substitutes safe?
Bone graft substitutes are implanted into patients by surgeons. Therefore the final factor in the success of your operation is the surgical technique and environment.
What questions should I ask my doctor about bone graft substitutes?
Which bone graft substitute are you planning to use and why?
Is the bone graft substitute synthetic, of human or animal origin?
Does the bone graft substitute you are using enable a quicker rehabilitation period after my operation?
Links
www.oxmed.co.uk
www.medline.com
