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More Bone for Grafting with Fewer Problems

Posted on: 03/17/2011
There are new and wondrous developments in the area of bone grafts. In this article, new techniques for bone grafting in the foot and ankle are discussed and demonstrated through description, photos, and drawings. Bone grafts are often used in ankle and foot surgery to fill in areas of bone or to fuse joints that have lost their stability because of injury or trauma (e.g., fractures, ligamentous tears).

Bone graft materials can come from the patient (that's called an autograft) or donated from someone else. Donated bone called an allograft comes from a bone bank. New methods of preparing bone grafts have changed the way patients respond to bone grafting with better results and fewer complications. At the same time, the use of bone marrow from inside the bone and growth factors and interleukins now speed up bone healing.

The biggest problem has always been the donor site for autografts. Most often, bone was taken from the iliac crest. The iliac crest is the top of the pelvic bone -- it's located where you place your hands on your hips.

Bone harvested from this area is plentiful but can cause excessive bleeding and postoperative pain. For some procedures, like ankle and foot reconstruction, the patient could go home the same day if it wasn't for problems with the bone graft donor site.

Because of major complications with graft site pain, deep infections, ugly scars, and sensory loss, surgeons started looking elsewhere for another source of autograft with fewer problems. With the advances in graft techniques, it's now possible to take bone from places other than the iliac crest.

The most popular sites have become the front of the tibia (lower leg bone) just below the knee, the lower part of the tibia (just above the outer ankle), the calcaneus (heel bone), and the greater trochanter (area of bone at the top of the femur or thigh bone).

If the graft donor site is close to the area where the donor bone is needed, it's considered a local source of autogenous graft material. If the bone is harvested from an area away from the main surgical site (usually in order to get more bone), it's referred to as a regional bone graft.

Whenever harvesting bone from these alternate sites, the surgeon must be careful to make the incision where the most bone can be removed without cutting into nearby nerves, blood vessels, or soft tissues. Incision sites for each of the alternate donor sites are provided.

Techniques and tools to use for removing bone graft are also provided in this article. The position to place the patient for bone harvesting is also discussed. Positioning can be tricky if the patient has a difficult bone fracture and movement might displace or shift the broken pieces.

Another important consideration in selecting bone graft material is the type of bone used. There are two main types of bone: cancellous and cortical. Cancellous bone is the spongy, less dense bone between the outer layer (perisoteum) and inner layer (bone marrow).

Cancellous bone has a better blood supply and that's helpful in getting new bone cells to survive. There's also more of it compared with cortical bone. And it is easier to form and shape cancellous bone around difficult or tight spots during bone grafting procedures. This last benefit is important when working in the ankle because of the many oddly shaped bones and joints.

Cortical bone is the stronger, denser, supportive bone that forms the outer shell of most bones. It provides good mechanical support. But with less of a natural blood supply, it is much slower to build blood vessels for the new bone.

Both types of bone (cancellous and cortical) are selected based on where the bone will be used and its specific purpose (e.g., fracture repair versus fusion). Once the best bone site for the problem has been selected and bone harvested, it must be transplanted to the location where it is needed.

The surgeon uses a tool called a high-speed burr to shape a trough in the bone where the graft can be placed. The bone graft forms a scaffold where other bone will fill in and around. It must be able to stimulate more bone cells to grow.

Until the bone fills in, the area won't be strong enough to support the patient. That's where instrumentation or fixation comes in. Metal plates, screws, and/or wires are used to hold everything together until healing takes place.

The authors admit there can be complications using these alternate donor sites. Problems can occur with poor wound healing, infection at the donor site, bone fracture of the donor bone, and failure of the bone graft to fuse the surgical site. The iliac crest is still an excellent source of donor bone (both cancellous and cortical). Fusion rates are the best when using iliac crest bone graft.

In conclusion, if there are concerns about bone graft donor site problems, allografts from the bone bank are still an option as is taking autografts from alternate sites. This article reviews all possibilities, pros and cons of each, as well as risks and benefits.

Timothy C. Fitzgibbons, MD, et al. Bone Grafting in Surgery About the Foot and Ankle: Indications and Techniques. In Journal of the American Academy of Orthopaedic Surgeons. February 2011. Vol. 19. No. 2. Pp. 112-120.

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