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August 30, 2010

Ankle Replacements Keep Boomers Moving
By Barbra Williams Cosentino, RN, LCSW
For The Record
Vol. 22 No. 16 P. 24

As techniques and devices have evolved, total ankle replacement has become a viable option for baby boomers who suffer debility from ankle arthritis or injury.

Ankle replacement is emerging as a viable solution that enables baby boomers to continue their active lifestyles. Many people are familiar with hip and knee replacements that for decades have proven effective in relieving chronic pain, restoring function, and allowing older adults to return to their normal activities. Fewer are familiar with the total ankle replacements now being performed with increasing frequency as baby boomers age and procedures and devices are perfected.

“When the first generation of total ankle replacements, or arthroplasties, were done in the 1970s, the success rate was not very impressive,” says Joseph Whalen, MD, PhD, an orthopedic surgeon specializing in foot and ankle surgery and assistant professor of orthopedics at the Mayo Clinic in Jacksonville, Fla. “Partially, the implant designs were at fault. Also, there was not enough known then about the biomechanics of the ankle. This lack of knowledge frequently led to device failure, which sometimes necessitated removal of the implant or to other, sometimes serious, complications. In the late ‘90s, newer implants were developed which have a much higher success rate. Today, techniques are being honed and new implants developed which continue to greatly improve the viability of these procedures.”

Promising Devices
A 2008 article in Podiatry Today reviews several implant devices that have been used extensively with good results. The Salto Talaris Total Ankle is recommended for patients with limited arthritis in the tibia and talar surfaces of the ankle and with no angular deformity. For patients with more extensive arthritis of the ankle joint and those with no avascular necrosis or osteoporosis, the Agility Total Ankle implant seems most effective. This is the most extensively studied device and has been used the longest of any available implant in the United States. The Inbone Total Ankle locks into the bone better than the other two systems and is ideal for patients in whom there is no medial or lateral gutter arthritis and whose ankle is well aligned, according to the article.

In May 2009, the FDA approved the Scandinavian Total Ankle Replacement (STAR) system. At the time of approval, the design had been implanted in more than 15,200 patients worldwide, and more than 35 peer-reviewed clinical outcome papers had been published on the device’s efficacy. A study published in the July 2009 issue of Foot and Ankle International indicated that after 24 months, ankles treated with the STAR system rather than with ankle-fusion surgery had better function and equivalent pain relief, making ankle-replacement surgery a viable option for those with end-stage arthritis.

According to a study published in the October 2009 issue of Foot and Ankle International, total ankle arthroplasty (TAA) can significantly improve quality of life, allowing patients to comfortably and safely return to light recreational activity and non–weight-bearing sports. The study reflects the outcomes experienced by 140 patients who had surgery between 1997 and 2005. All had the same type of device implanted, with the procedures performed in France by Michael P. Bonnin, MD. Nearly five years after surgery, more than 75% of the patients surveyed considered their ankles normal or nearly normal. Almost one half reported no discomfort in their daily activity but did experience some pain while participating in athletic and recreational activity. Thirty-one percent indicated they had no limitations in any situation.

In another study reported in a 2008 issue of Foot and Ankle Surgery, researchers reported that at five years postsurgery, more than 90% of patients still had their total ankle replacement devices, which were still functioning. At 10 years postsurgery, this number was approximately 80%. The article concluded that for many patients total ankle-replacement surgery has definite advantages over ankle fusion and if adherence to selection criteria is maintained, a long-lasting satisfactory outcome can frequently be achieved.

Why Ankle Replacement?
Several factors influence the decision to undergo ankle-replacement surgery. The most common is arthritis, defined broadly as inflammation or pain within a joint. According to the American Academy of Orthopedic Surgeons, arthritis is the leading cause of disability in the United States, occurring at any age and with varying degrees of severity. The three types of arthritis are as follows:

• Osteoarthritis, also known as degenerative arthritis, is due to the wear and tear of normal life, causing the gliding surface over the end of bones (cartilage) to wear away, creating inflammation and pain. Degenerative arthritis progresses slowly and usually affects people as they reach midlife or older. Besides age, risk factors include obesity and a family history of the disease.

• Rheumatoid arthritis is a systemwide disorder that unpredictably affects joints in many parts of the body. Due to this inflammatory disease process, the body’s own immune system attacks and eventually destroys the cartilage, leading to results similar to osteoarthritis.

• Posttraumatic arthritis develops following an injury to the foot or ankle in which the cartilage that holds the joint together sustains damage. If the injury is severe enough, cartilage separates from the bone, eventually causing additional pain and inflammation. At some point, scar tissue forms, leading to further pain and instability in the ankle joint. Problems can occur years or even decades after the initial injury.

According to Brian G. Donley, MD, director of the Foot and Ankle Center at the Cleveland Clinic, “The ankle is basically made up of the end of the tibia bone and the top of the talus bone. These two bones come together to create up-and-down motion that allows an individual to do a variety of actions such as walking, running, and playing sports. When the ends of these bones wear out, that is the basis for ankle arthritis, a condition that is painful and potentially crippling and greatly impacts quality of life.

“The pain is caused by the smooth surfaces of each bone becoming irregular and rough, and with every step they are grinding on each other with little cushioning,” he continues. “A total ankle replacement works by replacing the end of each bone with a new metal surface and a piece of high-density plastic in between. This replicates the normal ankle joint and allows a person to return to activity without the grinding, uncomfortable pain that the degenerative process had caused.”

Donley says, “The youngest age for TAA depends on many variables but generally should not be under 50. If the patients are properly selected, they will have a very good chance of getting great pain relief, and most older patients respond very well to the surgery in terms of rehabilitation and recovery.
“Because TAA is a newer technology and does not have the long track record of success that we’ve seen with hip and knee replacements, it is best not to place them in younger patients who would exert much more demand on them for longer periods of time. This could lead to loosening and wearing out of the plastic and thus the need for revision surgery,” he adds.

The recovery period following ankle replacement is rather long. Patients progress from splinting and no weight-bearing activities to casting for two weeks followed by stitch removal and encasement in a boot using crutches, still avoiding weight-bearing activities. By six weeks postsurgery, patients can begin to walk using the boot. Three months after surgery, they can start walking without the boot and begin increasing their activity. It takes roughly six months until full clinical benefit from the procedure is experienced, according to Donley.

As the media slowly disseminate information on total ankle replacements and as the sophistication of devices leads to greater success rates, the population aged 55 and older embrace this new procedure, a trend physicians expect to continue. Many older adults have been active participants in sports or exercise programs for years and are eager to take advantage of a surgical option that will lessen their pain and enable them to resume their activities.

A patient will not be considered a candidate for a total ankle replacement until other less-invasive options for ankle arthritis management have failed. The most conservative treatment involves the limitation of activity and the substitution of low-impact activities such as swimming for high-impact ones such as running. Physicians or other practitioners may recommend supportive shoes or prefabricated orthotics that are inserted into the shoe. Rocker soles have been shown to reduce stress on the ankle and can be added to many different types of footwear.

21st-Century Options
Before ankle-replacement surgery was perfected, ankle fusion (arthrodesis) was the most commonly used procedure. It involves fusing the ankle bones using screws that are permanently affixed to the bone. Ankle fusion is effective for relieving pain, but a patient’s range of motion is severely limited. This results in changes in gait, with the foot and knee joints absorbing the extra stress. This procedure is still performed but is gradually being supplanted by total ankle replacements for those patients for whom the surgery is appropriate.

According to John-Paul Veri, MD, an orthopedic surgeon and assistant professor of orthopedics and rehabilitation in the Oregon Health & Science University School of Medicine in Portland, during total ankle-replacement surgery, an incision is made in the front of the ankle to expose the joint. The surgeon removes part of the damaged bones that make up the socket of the joint and reshapes the bones that remain in place. These include the lower end of the shin bone (tibia), the lower end of the smaller lower-leg bone (fibula), and the top of the foot bone (talus). The prosthetic joint is then inserted and the parts attached. Screws may be placed through the two leg bones to give added stability; a bone graft also increases the new ankle’s stability.

Because the new devices require that less bone be removed, the bone to which the device is affixed is now able to be stronger than was possible with previous implants. However, some of the parts may wear out over time and revision surgery may become necessary.

Veri says, “When joint replacements wear out, there is a need for special prostheses and components to make up for lost bone. We already have excellent protocols for hip and knee revisions should they become necessary. However, because ankle arthroplasties are still relatively new, there is a great need and interest in developing better surgical techniques, materials, and devices to use when revision surgery is needed. The art and science of ankle replacement is still evolving.”

Possible Complications
“Proper patient selection is one of the critical ways to decrease the risk of complications or device failure,” Whalen says. The surgeon should have a sense in advance of the procedure as to how much deformity will be able to be corrected. Ideal candidates include individuals over the age of 55 who are relatively healthy and who are not morbidly obese. The patient should have a relatively sedentary lifestyle and should participate in sports that involve low-impact activity. However, as development continues on new devices and more surgeons become proficient in the techniques facilitating greater success, the definition of appropriate candidates is being expanded.

Because the major complication of total ankle replacement is delayed or impaired wound healing, patients who have systemic medical conditions such as coronary artery disease, peripheral vascular disease, diabetes, and other disorders in which circulation may already be compromised are considered to be at higher risk for device failure or postoperative complications. The procedure may not be appropriate for some patients with diabetes or patients who suffer from avascular necrosis, in which the bone is too soft for the implant to be effective. Patients with allergies to metal are not appropriate candidates.

Along with poor wound healing, another possible complication is technical failure, occurring with improper placement of the device with ensuing misalignment. Other potential complications include loosening of the artificial joint over time, damage to the nerves or blood vessels, infection, and increased ankle weakness or instability.

Procedure Specifics
In the 40 years since the first TAA was performed, many changes and improvements have been made to the devices used in the procedure. The newer-generation implants are two-component designs (fixed-bearing devices) and three-component devices (mobile-bearing devices) that do not typically require cement. Both types use the ligaments to maintain stability.

Unlike ankle fusion in which the two bones of the ankle are fused to prevent them from grinding against each other, ankle replacement involves replacing the ends of the bones, providing smoother surfaces and allowing the patient normal mobility of the ankle joint.

As with every procedure, results are sometimes less than optimal. “Failure means different things to different surgeons,” Donley says. “Basically, [in ankle-replacement surgery] it means loosening of the prosthesis that would require revision surgery, or it could mean that the patient does not get a reasonable improvement in their pain and/or mobility. We do not yet know the failure rate, which depends on the prosthesis used and many other factors. In general, it is too early to determine failure rates because the latest designs have not been used in the U.S. for us to have long-term follow-up results. Short-term follow-up, which is now approximately two years, appears very promising.”

— Barbra Williams Cosentino, RN, LCSW, is a medical writer and psychotherapist in private practice in Forest Hills, N.Y.