Understanding Ankle Arthritis, Ankle Replacement
Severe arthritis of the ankle joint is the result of progressive wearing down of the articluar cartilage cushion that lines the joint, ultimately resulting in bone-on-bone grinding of the joint surface.
This “end stage” arthritis results in pain, combined with loss of function and mobility - severely limiting normal activity. When this end stage is reached and non-operative options (such as medication, injections, and bracing) have been exhausted, patients are presented with three methods of surgical treatment: ankle fusion (also known as arthrodesis), total ankle replacement (TAR) and, in some cases, distraction arthroplasty.
In our interview with Dr. Deland, we primarily focused on one option in particular – total ankle replacement – and its evolution to an operative procedure that holds much promise today as a valid alternative to ankle fusion for certain patients.
Treatment options for end-stage arthritis of the ankle
Traditionally, when confronted with end-stage arthritis, patients have undergone a fusion, or arthrodesis, procedure, creating raw bone surfaces which are held together with metal plates and/or screws until the bone surfaces unite or fuse. The goal of fusion is to fix the joint in the correct position; pain is relieved at the expense of loss of motion at the ankle joint. The ankle is generally cast for approximately 8-12 weeks (until the fusion is solid).
This procedure continues to be helpful to patients as a means of pain relief. However, there are concerns regarding arthrodesis procedures. Because an ankle fusion results in loss of motion, the joints surrounding the ankle flex and extend to compensate. While this allows most fusion patients to walk without a limp, the primary concern is that these adjacent joints run the risk of becoming arthritic themselves.
Alternatively, total ankle replacement is a relatively new procedure, the modern, accepted design having only come into widespread use in the late 1990s. Forgoing the fusion process, this procedure instead relies on replacement of the arthritic surfaces with a man-made implant that is composed of two or three components that glide against each other using low-friction materials. The primary benefit is pain relief with retained ankle motion.
Although there are no long-term (>10 yr.) studies on TAR, this procedure requires a shorter immobilization period and has been shown to provide a functional range of motion in the ankle, allowing patients to actively engage in daily tasks (and low-impact sports). More importantly, TAR results in a smaller amount of stress upon the surrounding joints, reducing the risk of arthritis in those areas as well.
A third option for some patients with end-stage arthritis is a procedure called distraction arthroplasty, a surgical process aimed at younger patients that involves placing the ankle in a framework of pins set into the bones and then slowly adjusting that framework in order to distract (pull apart) the joint surfaces. In theory, this aids the body in regenerating ankle cartilage.
The patient must have proper alignment of the foot in order for the procedure to be successful. The fixator holding the pins around the ankle is generally in place for ten weeks; improvement is gradual, but after one year ankle pain is typically significantly diminished. Studies show that this procedure has a 60% rate of success.
Determining the Proper Treatment
Regardless of the condition of the ankle, each patient will require a treatment that is individually suited to their needs. Factors in determining the proper treatment include age (generally, candidates for TAR are aged 50 or older), activity level, body weight, quality of bone stock, overall alignment of the foot, stability, and degree of arthritic severity.
In order to determine some of these factors, a doctor will conduct a physical exam and prescribe x-rays.
Generally, candidates for total ankle replacement have good mobility, with good bone stock and foot alignment. If TAR is deemed to be an appropriate treatment, Dr. Deland stresses that choosing a surgeon with significant experience is vital. “No surgeon should do only one or two of these TAR procedures per year – they’ll get into trouble mighty fast,” he explains. “You have to know about foot alignment, and you have to know the implant. Studies show a steep learning curve when performing this procedure.”
A surgeon who is well-versed in the procedure will then be able to determine the best type of implant for the patient.
Implants for Total Ankle Replacement
The difficulties in creating an effective implant for total ankle replacement can be largely attributed to the complex motion at the ankle joint. The center of rotation, or axis, of the ankle joint does not remain constant through the course of motion. The “trick” is to allow for rotational forces while moving through a range of flexion and extension.
Total ankle replacement implants have gone through several generations of design and materials. Dr. Deland anticipates much progress in the near future, but stresses that results from long-term studies are needed to determine the effectiveness of these implants. Deland says that while the procedure requires exacting surgical precision, he is encouraged by the progress total ankle replacement has enjoyed in recent years.
“We now have to see how the next generation performs,” he notes. “There will be some ongoing issues relating to design and materials used, but it’s a promising time.”
When ankle arthritis has progressed to an advanced stage, where non-surgical methods of treatment are no longer effective, several options are available. When determining the best possible treatment for each patient, numerous factors will be considered by an orthopedic surgeon specializing in foot and ankle surgery, including age, activity level, body weight, bone quality, alignment, and severity of arthritis.
Arthrodesis (ankle fusion) has been the traditional “gold standard” treatment option for end-stage ankle arthritis. Yet, in the last two decades, total ankle replacement has become an effective alternative for many patients. It is important to consult a foot and ankle specialist who understands the factors that influence the condition of the ankle, and who is able to recommend the best option for relief of arthritic ankle pain.