An artificial ankle joint, also known as an ankle joint prosthesis, is a surgical treatment for osteoarthritis of the upper ankle joint. However, the success of an artificial ankle joint is closely linked to the surgeon's experience. Here you will find further information as well as selected specialists and centers for ankle joint prostheses.
The ankle joint is located between the leg and the foot. It contains the bones and soft tissues that are responsible for bending and stretching the foot. The ankle joint is the most heavily loaded joint in the human body. With every step, it has to bear up to seven times the weight of the individual's body.
If the ankle joint is replaced by an artificial joint, this is referred to as an artificial ankle joint or an ankle joint prosthesis.
Illustration of the different bones in the ankle joint © bilderzwerg | AdobeStock
Osteoarthritis, i.e. joint wear and tear, can also occur in the upper ankle joint (OSG). Osteoarthritis of the upper ankle joint occurs at an advanced age, particularly in people who play sports that put strain on the lower extremities. These sports include
The most common fractures in the lower limb occur in the upper ankle joint. In later years, up to one in two cases of ankle fractures can lead to osteoarthritis. This is independent of how precisely the fracture could actually be surgically repaired after the injury.
These sobering early and late courses are caused by the extremely sensitive biomechanics of the upper ankle joint. If, for example, a small bony step of only 1 to 2 mm remains after a fracture operation, this already leads to a reduction in the contact surface of the corresponding bones between the lower leg and foot of 30 to 60 percent.
The resulting overloading of the remaining joint surface permanently increases the risk of osteoarthritis developing. Even small detachments of the joint cartilage can trigger long-term changes in wear and tear after convalescence.
The most common sports injury is also localized to the upper ankle joint. It is estimated that external ligament tears occur up to 1000 times a day in Germany.
People under the age of 35 and, in this age group, young people between the ages of 15 and 20 are most commonly affected. In around 15 percent of them, wear-related late damage to the ankle joint must be expected in the further course of the disease.
Before deciding on an ankle joint prosthesis, a thorough physical examination including an X-ray of the diseased joint is carried out. Magnetic resonance imaging(MRI) may be a necessary additional examination in certain cases.
Not every patient is equally suitable for an ankle joint prosthesis. Bone quality plays a particularly important role: the bone substance of the ankle bone in particular must still be of sufficiently good quality. There must also be no extreme osteoporosis in the joint area.
Infections in the affected joint area must be ruled out. If there has been an infection, it must have occurred at least one year ago and have been treated.
Further limitations are
Contraindications for an ankle joint prosthesis are therefore
In principle, conservative treatment measures are initially carried out for ankle arthrosis. In some cases, these can alleviate the symptoms for years.
Once these options have been exhausted, there are two surgical treatment options:
The response of the ankle joint to the unfavorable influences described is always the same:
They are an expression of progressive cartilage wear in the joint. Finally, osteoarthritis develops as the affected joint becomes progressively stiffer.
Until a few years ago, the only remedy for this stage of wear and tear was to stiffen the damaged joint. This type of surgical immobilization then leads to freedom from pain or at least to a reduction in pain in the affected joint area.
However, in around one in five patients the stiffening operation fails, i.e. the bony structure of the joint is not restored. As a result, the stress pain remains. In this case, those affected must undergo another fusion operation.
If the fusion operation is successful, the upper ankle joint is "immobilized" and can no longer perform any movements. The pain disappears, but the lost mobility must be absorbed by the neighboring joints of the upper ankle.
This extra work is not without consequences. Typical and dreaded late complications of fusion are so-called secondary arthroses. These are wear and tear changes caused by overuse, particularly in the immediately adjacent lower ankle joint.
Up to 28 percent of the existing joint surfaces can be affected later on.
The patient's lifestyle also influences the surgical outcome. Factors for poor or absent bony remodeling despite a technically successful operation include
For some years now, ankle joint prostheses have been a good alternative to ankle fusion surgery.
Artificial ankle joints have been used since around 1970. The optimistic expectations from the early days could not be confirmed in long-term observation. The prostheses loosened after a few years and had to be removed. The design and anchoring method of the first-generation prostheses were not yet fully developed.
However, there is now long-term experience with modern total ankle prostheses. These consist of three components:
Stability in the artificial joint is adjusted via the height of the polyethylene sliding core.
The cement-free anchoring of the two components to thetalus andtibia is a decisive improvement. 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 operation. It should therefore be performed by experienced surgeons who are familiar with this problem.
The results are not yet quite comparable with those of hip endoprosthetics. However, modern implants achieve similarly good durability.
If an ankle joint prosthesis loosens in the course of time, only individual components are usually affected. Complete loosening is rare and primarily occurs after infections. To date, there are no generally applicable surgical strategies for cases of loosening. Here, too, the surgeon's experience determines the further course of action.
In principle, in the case of aseptic loosening, the artificial joint can be replaced completely or in its individual components. Combinations of different models from different manufacturers are possible depending on the extent of the loosening and the condition of the bone.
Revision arthroplasty models such as those used in hip and knee arthroplasty would certainly be desirable, but will probably continue to be limited to custom-made products in the near future due to the anatomical conditions. Replacement operations of loosened OSG components are still limited to individual cases.
Classic arthrodesis is the treatment of choice after definitive failure of the ankle joint prosthesis.
In Europe, the five-year survival rate after implantation of an ankle prosthesis is 89 percent and the ten-year survival rate is 76 percent.
The indications for ankle arthroplasty are still the subject of fundamental debate. However, the figures show that these procedures have been steadily increasing in Germany for several years: approx. 1500 implantations / year in 2009; in comparison: Great Britain approx. 800 / year.
Early revision rates after arthroplasty are 7 percent on average. They are only slightly better than after fusion procedures (9 percent). The main cause of revisions after arthroplasty implantation is premature loosening (28 percent). An important reason for this is the surgeon's experience ("learning curve").
Typical errors relating to an artificial ankle joint are incorrect positioning, but also
This knowledge, together with increasing experience in implantation techniques, means that revisions are becoming less and less necessary.
Today, fusions are still performed ten times more frequently than ankle prosthesis implantations. Nevertheless, it does not offer better and more convincing results, neither in the early revision rates nor in later complications.
Immediately after the operation, the operated leg is fitted with a removable Vacoped® splint.
If the procedure is uncomplicated, the patient can stand up with assistance on the first day after the operation. On the second day after the operation, the Vacoped® splint is used to put full axial weight on the leg once. This serves to post-compress the prosthesis components in the bone bed.
Walking exercises with the splint begin on the second day after the operation. The patient can put partial weight on the operated leg with 20 kg for a total of six weeks after the operation. In addition, so-called "intermediate mobilization" of the operated ankle joint with lifting and lowering of the foot is carried out from this day onwards.
This is supplemented by passive exercise of the joint with a motorized splint. Manual lymph drainage and elevation promote the reduction of swelling in the joint.
Once the wound has healed, the stitches are usually removed on the 12th day after the operation.
Further physiotherapeutic treatment can then be
be carried out. The splint can be removed six weeks after the operation. The patient should now quickly put full weight on the leg again.
The rehabilitation phase lasts a total of approx. 12 weeks.
The first X-ray check is carried out immediately after the operation. Further X-ray checks are carried out
are carried out.
As with other operations, complications can occur during the implantation of an ankle prosthesis.
A fracture of the inner or outer ankle either during the operation or immediately after the operation must then be stabilized surgically.
Wound healing disorders and other soft tissue problems sometimes also require longer treatment. Occasionally, additional plastic surgery procedures are also necessary.
In some cases, follow-up operations must also be performed. The reason for this can be, for example, in addition to bone fractures
be.
In rare cases, it is necessary to replace parts of the prosthesis or to perform a fusion operation. With newer prosthesis models, relatively little bone substance is lost. Therefore, if necessary, a stiffening operation can be performed without difficulty.
After successful implantation of a prosthesis, it is a realistic therapeutic goal for patients to regain pain-free joint function in the upper ankle joint.
Endoprosthetic treatment is a good therapeutic alternative to fusion surgery. However, despite the technical innovations, the results of the procedure are closely linked to the surgeon's experience.
The advantage of the prosthesis over ankle fusion is also the shorter rehabilitation period. Prolonged immobilization in a cast, for example, as with many arthrodeses, is not necessary with the prosthesis.
After successful surgery, the gait is pain-free and mobility is close to that of a healthy joint. Normal specialist shoes can be worn without problems, stiletto heels cannot.
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