Arthrodesis or Joint Fusion
Arthrodesis is the artificial induction of joint ossification between two bones via surgery. This is done to relieve intractable pain in a joint which cannot be managed by pain medication, splints, or other normally-indicated treatments. The typical causes of such pain are fractures which disrupt the joint, and arthritis. It is most commonly performed on joints in the spine, hand, ankle, and foot. Historically, knee and hip arthrodeses were also performed as pain relieving procedures, however with the great successes achieved in hip and kneearthroplasty, arthrodesis of these large joints has fallen out of favour as a primary procedure, and now are only used as procedures of last-resort in some failed arthroplasties.
A bone graft can be created between the two bones using a bone from elsewhere in the person’s body (autograft) or using donor bone (allograft) from a bone bank.
Bone autograft is generally preferred by surgeons because, as well as eliminating the risks associated with allografts, bone autograft contains native bone-forming cells (osteoblasts), so the graft actually forms new bone itself (osteoinductive), as well as acting as a matrix or scaffold to new bone growing from the bones being bridged (osteoconductive). The main drawback of bone autograft is the limited supply available for harvest.
Bone allograft has the advantage of being available in far larger quantities than autograft; however, the treatment process the bone goes through following harvest, which usually involves deep-freezing and may also involve demineralization, irradiation and/or freeze-drying, kills living bone or bone marrow cells. This significantly reduces the immunogenicity (risk of graft rejection) such that no anti-rejection drugs are needed and, combined with appropriate donor screening practices, these processing and preservation practices can significantly reduce the risk of disease transmission. In spite of all of this processing, cancellous allograft bone retains its osteoconductive properties. Furthermore, certain processing practices have been shown to also retain the acid-stable osteoinductive proteins in cortical bone grafts, so that many bone allografts can be considered both osteoconductive and osteoinductive.
A variety of synthetic bone substitutes are commercially available. These are usually hydroxyapatite or tricalcium phosphate based granules formed into a coralline or trabecular structure to mimic the structure of cancellous bone. They act solely as an osteoconductive matrix. Some manufacturers have recently begun supplying these products with soluble bone-forming factors such as bone morphogenetic protein to attempt to create a synthetic product with osteoinductive properties.
Metal implants can be attached to the two bones to hold them together in a position which favors bone growth.
A combination of the above methods is also commonly employed to facilitate bony fusion.
At the completion of surgery and healing, which takes place over a period of several weeks to over a year, the two adjoining bones are fused and no motion takes place between them. This can have the effect of actually strengthening the bones, as in anterior cervical fusion.
Surgeons fuse joints in many different ways. In the past, most of the procedures used a bone graft from your pelvis. Surgeons now try to take a small amount of bone from the end of the radius bone instead. A bone graft involves taking bone tissue from one area and transplanting it into another area. This encourages the ends of the bone to grow together. If your surgeon grafts bone from your pelvis, you will have two incisions, one on the back of your wrist, and another on the side of your hip. Your surgeon may also try to fuse the bones without a graft. Surgery can last up to 90 minutes.
Who Is a Candidate for Arthrodesis?
Arthritis patients who have joints so severely damaged that usual pain management techniques fail are candidates for arthrodesis. Depending on which joint is affected, the patient may have the option of joint replacement surgery or arthrodesis. The goals for recovery may be factored into the decision.
The primary benefit of arthrodesis is pain relief in the affected joint. By surgically eliminating the joint, pain relief is an attainable goal, barring any complications of surgery.
Consider your goals when deciding if arthrodesis is the best option for you.
Recovering from Arthrodesis
After surgery, a cast will be placed over the joint that underwent arthrodesis. Until there is x-ray evidence of fusion, use of the operated joint will be limited. The process is a long one. For example, ankle arthrodesis patients are not allowed to bear weight for between 8 to 12 weeks. Patients should keep their leg elevated to decrease swelling and promote healing, until there is evidence of fusion. While the patient needs to be non-weightbearing, crutches or wheelchairs may be very useful.
Arthrodesis is not without potential complications. Pain at the site of bone fusion, nerve injury, infection, or broken hardware (e.g., pins, screws) are known risks associated with arthrodesis. The most troublesome potential complication is a failed fusion, meaning the joint physically does not fuse. Arthrodesis, though, is normally a very successful procedure and serious complications are rare.