Ankle Replacement for Osteoarthritis: Clinical Examination, Information, and Specialists in Ankle Replacement Surgery

The ankle joint is located between the leg and the foot. It consists of the bones and soft tissues responsible for flexing and extending the foot. The ankle joint is the joint in the human body that bears the heaviest load. With every step, it must bear up to seven times the individual’s body weight.

When the ankle joint is replaced with an artificial joint, it is referred to as an artificial ankle joint or an ankle joint prosthesis.

Illustration of the various bones in the ankle joint © bilderzwerg | AdobeStock

Ankle joint degeneration

Osteoarthritis, or joint wear and tear, can also occur in the upper ankle joint (OSG). Osteoarthritis in the upper ankle joint is particularly common in older adults who participate in sports that place stress on the lower extremities. These sports include

• long-distance running,
• skateboarding,
• soccer, handball, and basketball, as well as all other ball sports.

Osteoarthritis Following Ankle Fractures

The most common fractures of the lower extremities occur at the ankle joint. Following ankle fractures, osteoarthritis can develop in up to half of all cases later in life. This occurs regardless of how precisely the fracture was actually realigned surgically after the injury.

These disheartening early and late outcomes stem from the extremely delicate biomechanics of the ankle joint. For example, if a small bony step of just 1 to 2 mm remains after surgery to repair the fracture, this alone leads to a 30 to 60 percent reduction in the contact area between the corresponding bones of the lower leg and foot.

The resulting overload on the remaining joint surface permanently increases the risk of developing osteoarthritis. Even small fragments of articular cartilage can trigger long-term degenerative changes after recovery.

The most common sports injury is also located in the upper ankle joint. Estimates suggest that lateral ankle ligament tears occur up to 1,000 times a day in Germany.

Those most commonly affected are people under 35 years of age, particularly adolescents between the ages of 15 and 20. In about 15 percent of these cases, long-term wear-and-tear-related damage to the ankle joint is to be expected over time.

Before deciding on an ankle prosthesis, a thorough physical examination—including an X-ray of the affected joint—is required. In certain cases, magnetic resonance imaging (MRI) may be a necessary additional test.

Not every patient is equally suitable for an ankle joint replacement. Bone quality plays a particularly important role: the bone substance, especially in the talus, must still be of sufficiently good quality. There must also be no severe osteoporosis in the joint area.

Infections in the affected joint area must be ruled out. If an infection has occurred, it must have occurred at least one year prior and have been fully treated.

Other limitations include

• severe neurological disorders that impair general coordination, as well as
• general severe vascular diseases.

Contraindications for an ankle joint prosthesis are therefore

• severe bone ischemia,
• severe, destructive forms of ankle arthritis,
• infection-related joint destruction,
• neuropathic joint destruction,
• axial deviations of the talus exceeding 20 degrees,
• significant instability of the ankle joint, and
• previous failed attempts at arthrodesis.

In general, conservative treatment measures are the first line of treatment for ankle osteoarthritis. In some cases, these can alleviate symptoms for years.

Once these options have been exhausted, there are two surgical treatment options:

• ankle fusion (ankle arthrodesis), which eliminates pain, and
• the implantation of an artificial joint.

Conventional Surgical Treatment of Ankle Osteoarthritis

The ankle joint’s response to the adverse factors described above is always the same:

• a tendency to swell,
• fluid accumulation,
• increasing pain with weight-bearing,
• nighttime pain at rest.

These symptoms are indicative of progressive cartilage wear in the joint. Eventually, as the affected joint becomes increasingly stiff, the full-blown symptoms of osteoarthritis develop.

Until a few years ago, the only effective treatment at this stage of wear and tear was fusion of the damaged joint. This type of surgical fusion typically results in the elimination of pain or, at the very least, a significant reduction in pain in the affected joint area.

However, in about one in five patients, the fusion surgery fails—that is, the joint does not fuse properly. As a result, pain during weight-bearing persists. In such cases, patients must undergo another fusion surgery.

If the fusion surgery is successful, the ankle joint is “immobilized” and can no longer move. The pain disappears, but the lost range of motion must be compensated for by the joints adjacent to the ankle.

This increased workload is not without consequences. Typical and feared long-term complications of fusion are so-called secondary osteoarthritis. These are wear-and-tear changes caused by overuse, primarily in the immediately adjacent lower ankle joint.

Up to 28 percent of the existing joint surfaces may be affected by this in the long term.

The patient’s lifestyle also influences the surgical outcome. Factors contributing to poor or absent bone union despite a technically successful operation include

• obesity,
• alcohol abuse, and
• tobacco use.

For several years now, ankle replacement has been a good alternative to ankle fusion surgery.

Artificial ankle joints have been used since around 1970. The optimistic expectations from the early days were not confirmed by long-term follow-up studies. The prostheses became loose after a few years and had to be removed. The design and fixation method of the first-generation prostheses were not yet fully developed.

However, there is now long-term experience with modern total ankle replacements. These consist of three components:

• a rounded cap for the talar roll made of a cobalt-chromium alloy
• a plate for the tibial articular surface made of a cobalt-chromium alloy
• a freely movable polyethylene bearing core.

Stability in the artificial joint is adjusted by varying the height of the polyethylene glide core.

A significant improvement was achieved through the cementless fixation of the two components to the talus and tibia. A special coating (e.g., with titanium/calcium phosphate) enables the bone to fuse firmly with the implants.

The implantation of an artificial ankle joint is a technically demanding and difficult procedure. It should therefore be performed by experienced surgeons familiar with this specific issue.

The results are not yet fully comparable to those in hip replacement surgery. However, modern implants achieve similarly good longevity.

Left: Ankle joint with wear and tear. Right: Ankle joint prosthesis © a7880ss | AdobeStock

If loosening of an ankle prosthesis occurs over time, usually only individual components are affected. Complete loosening is rare and primarily occurs following infections. To date, there are no universally applicable surgical strategies for cases of loosening. Here, too, the surgeon’s experience determines the course of action.

In principle, in cases of aseptic loosening, the artificial joint may be replaced either completely or in its individual components, depending on the circumstances. Combinations of different models from various manufacturers are possible, depending on the extent of the loosening and the condition of the bone.

Revision prosthesis models, such as those used in hip and knee arthroplasty, would certainly be desirable; however, due to anatomical constraints, they will likely remain limited to custom-made prostheses for the foreseeable future. Replacement surgeries for loosened ankle joint components are still limited to individual cases.

Classic arthrodesis is the treatment of choice following definitive failure of the ankle prosthesis.

In Europe, the five-year survival rate following ankle joint replacement is 89 percent, and the ten-year survival rate is 76 percent.

The indications for endoprosthetic replacement are still the subject of ongoing debate. However, the figures show that in Germany, the number of these procedures has been steadily increasing for several years: approximately 1,500 implantations per year in 2009; by comparison, approximately 800 per year in the United Kingdom.

The early revision rates following endoprosthetic replacement average 7 percent. They are only slightly better than those following fusion procedures (9 percent). The main cause of revisions following endoprosthesis implantation is premature loosening (28 percent). A major reason for this is the surgeon’s experience (“learning curve”).

Typical errors associated with ankle replacement include misalignment, as well as

• incorrect sizing,
• misjudgments regarding ligament tension,
• omitted or excessive concomitant procedures, and
• other technical errors during implantation.

This knowledge, combined with increasing experience in implantation techniques, means that revisions are becoming less and less necessary.

Today, ankle arthrodesis is still performed ten times more frequently than ankle joint replacement surgery. Nevertheless, it does not offer better or more convincing results, either in terms of early revision rates or later complications.

Immediately after surgery, the operated leg is fitted with a removable Vacoped® splint.

If the recovery proceeds without complications, the patient can stand up with assistance as early as the first day after the procedure. On the second day, the leg is subjected to full axial weight-bearing once while wearing the Vacoped® splint. This serves to further compress the prosthetic components within the bone bed.

Starting on the second day after surgery, walking exercises begin while wearing the splint. The patient may bear partial weight (up to 20 kg) on the operated leg for a total of six weeks following surgery. In addition, starting on this day, so-called “interim mobilization” of the operated ankle joint is performed by raising and lowering the foot.

This is supplemented by passive exercise of the joint using a motorized splint. Manual lymphatic drainage and elevation help reduce swelling in the joint.

The sutures are typically removed once wound healing is complete, usually on the 12th day after surgery.

Further physical therapy can then

• take place as part of inpatient follow-up care or
• outpatient physical therapy

. Six weeks after surgery, the splint can be removed. The patient should then quickly resume putting full weight on the leg. 

The rehabilitation phase lasts a total of approximately 12 weeks.

Follow-up Examinations After Total Ankle Replacement

The first X-ray follow-up takes place immediately after surgery. Subsequent X-ray follow-ups are

• upon discharge from inpatient care,
• 6 weeks postoperatively,
• 12 weeks postoperatively,
• 6 months post-surgery, and
• annually, each as part of the clinical follow-up examinations

.

As with other surgeries, complications can occur during the implantation of an ankle joint prosthesis.

A fracture of the medial or lateral malleolus—whether occurring during surgery or immediately afterward—must then be stabilized surgically.

Wound-healing disorders and other soft-tissue problems sometimes require prolonged treatment. Occasionally, additional plastic surgery procedures are also necessary.

In some cases, follow-up surgeries must also be performed. The reasons for this can include, for example, in addition to bone fractures,

• loosening of individual prosthesis components,
• persistent pain, or
• excessively limited mobility

.

Rarely is it necessary to replace prosthetic components or perform a fusion procedure. With newer prosthetic models, relatively little bone is lost. Therefore, if necessary, a fusion procedure can still be performed without difficulty.

For patients, regaining pain-free weight-bearing capacity in the ankle joint is a realistic therapeutic goal following successful prosthesis implantation.

Total ankle replacement is a good therapeutic alternative to ankle fusion surgery. However, despite technical innovations, the results of the procedure are closely linked to the surgeon’s experience.

Another advantage of the prosthesis over ankle fusion is the shorter rehabilitation period. Prolonged immobilization—for example, in a cast, as is common with many arthrodeses—is not necessary with the prosthesis.

After a successful surgery, walking is pain-free and mobility is close to that of a healthy joint. Regular specialized shoes can be worn without any problems, but high heels cannot.