Anterior Iliac Crest Tricortical Bone Graft
What is a bone graft?
A bone graft is when bone is placed at the desired site to speed up the fusion process. The Iliac Crest is one of the most common sites to harvest bone grafts from. This is because it is an easily accessible donor site that offers a relatively large and safe supply of bone. When harvesting bone graft, the aim is to obtain enough bone for the fusion operation, while limiting the effects of its removal.
Different types of bone graft
Bone grafts can be harvested from elsewhere in the patient’s body, which is called an autologous transplant or autograft. They can also be harvested from another person, which is known as an allograft. Synthetic, or natural bone substitutes can be used too.
Autografts typically have higher fusion rates, and given that they are harvested from the patient’s own body, they eliminate disease transmission or immune rejection risks. However, they do require an additional procedure to harvest the bone graft, which carries its own set of potential complications. Autografts can also increase post-operative pain and the graft bone is limited in terms of size, shape, quality and amount. This is particularly true in children, who often need internal stabilisation hardware and bracing to offer initial support.
Bone graft alternatives
Bone morphogenetic proteins (BMP) stimulate bone growth naturally in the human body. These proteins naturally exist in the body and they can be produced, concentrated and placed in the fusion site in surgery to attract bone-forming cells, and to stimulate cells to form bone. More importantly, they can create a fusion without the need for any use of the patient’s own bone.
Although BMPs are more expensive in comparison to bone graft, the advantages are numerous:
- They decrease fusion time by a third. This means faster hospital discharge and a faster return to day-to-day activities.
- They increase the successful fusion rate to up to 90%.
- They bypass the pain, blood loss and risk of infection and nerve damage that may occur during the bone graft harvesting procedure.
- Bone growth in unwanted sites.
- Transient desorption of adjacent bone.
- Seroma formation or local oedema.
- Local inflammatory reaction.
- Potential development of an immune reaction, particularly if used in subsequent surgeries.
- Effects on developing embryo in pregnancy are unknown.
The bone graft harvesting procedure
The patient lies on his/her back, and the skin over the harvest site is cleaned. The surgeon then makes an incision over the anterior iliac crest and cuts a window into the thick cortical bone. The inner cancellous bone is removed for grafting and the wound is stitched closed.
Potential complications of bone graft harvesting
Removing bone may result in a slight defect in the smooth line of the skin below the surgical scar. While not very noticeable it can be felt in thinner patients.
In some cases, the removal of bone graft can stress the adjacent bone and weaken the region. Although uncommon, it can lead to a fracture through the pelvis at a later stage. This is more likely in people with pre-existing osteoporosis.
Bone graft removal will cause pain at the donor site, which usually settles within months but can continue for years. Pain can also be caused by injury during access to the site or as a result of injury or tension on nearby nerves.
Potential complications of bone graft placement
While the use of bone from another person holds many advantages, such as: avoiding donor site pain and complications, decreasing surgery duration and cost, plus access to an unlimited amount of bone; the downside is that the fusion rate may be less successful, slower, and the bone may be weaker than the patient’s own. There is also a risk of infection transfer if untreated bone is used. (Allograft bone in the South African setting is processed and treated, which virtually eliminates the risk of infection.)
During a bone graft, bone fragments are placed in the space between two bones. If the bones are kept still for long enough, the fragments fuse with one another – and the adjacent bones – to form a solid and pain-free single bone. However, if excess movement occurs before fusion has occurred, the graft can become displaced. This can result in pain, injury to adjacent tissues, misalignment of the bones or non-fusion, which is known as non-union or pseudoarthrosis.
Regardless of whether bone graft is obtained from a site in the patient’s body, another person’s body or synthetic materials, a risk of infection exists. This risk is minimised as much as possible, but should infection occur, the area may need to be cleaned.
Every effort is made to ensure that bone grafts are placed in optimum positions. However, there are rare instances where these implants are not optimally placed and a further procedure may be required to correct this. Misplacement may be the result of anatomical variations, equipment limitations or system failures.