The upper ankle joint (OSG) consists of three bones:
- Shin bone (tibia)
- fibula (calf bone)
- Ankle bone (talus)
The tibia and fibula form the ankle joint fork for a centered, precisely guided fit of the talus. The upper ankle joint is responsible for lifting and lowering the foot. The talus performs a sliding and slight rotational movement within the ankle joint fork.
The joint surfaces of the tibia, fibula and talus are covered by a thin but highly elastic cartilage.
Anatomy of the ankle joint © bilderzwerg / Fotolia
Osteoarthritis leads to the destruction of joint cartilage. The main cause of ankle arthrosis is a previous injury (trauma). It is comparatively rare for osteoarthritis of the ankle joint to be caused by another underlying disease. Such an underlying disease could be joint inflammation (arthritis), for example.
Older people suffer more frequently from worn joints. However, younger people, especially very active athletes, can also be affected. A twisted ankle with torn ligaments often leads to chronic joint instability. Over the years, this can lead to increased cartilage wear and ultimately to osteoarthritis in the ankle joint.
Twisting an ankle, for example when jogging or stepping on a kerb, can lead to afracture of the medial malleolus or ankle joint.
- of the medial malleolus or
- the lower part of the fibula (outer ankle).
can lead to a fracture. Sometimes even the medial malleolus and lateral malleolus are affected by a fracture. Accompanying injuries such as cartilage damage to the talus often also occur.
Typical symptoms of an ankle fracture are
- a swollen, painful ankle joint with bruising (haematoma) and
- restricted movement.
In Germany alone, around 10,000 ankle fractures are reported to the employers' liability insurance associations every year.
Furthermore, misalignments in the hindfoot area are often responsible for increased pressure on the ankle cartilage. Misalignments can also occur after fractures. The result is then also premature wear of the cartilage and thus ankle arthrosis.
Primary ankle arthrosis is less common. It does not develop due to a previous illness or injury, but rather without any recognizable cause.
A genetically determined inadequate cartilage structure is probably responsible. However, primary ankle osteoarthritis is rather rare compared to osteoarthritis of the hip or knee joint. This is mainly due to a peculiarity in the biochemical composition of ankle cartilage. Compared to other joint cartilage, such as that of the hip joint, the cartilage of the ankle joint has a significantly higher compressive strength.
Extensive cartilage damage in the upper ankle joint is characterized by a painful restriction of movement in the joint. Every step hurts and in advanced stages of ankle arthrosis, pain is also present at rest. The upper ankle joint then swells under load and mobility is increasingly restricted.
Axial deviations and sometimes ligament instability are also frequently observed. The X-ray image then shows the destruction of the joint with a narrowed or abolished joint space and bony attachments to support the joint.
The upper ankle joint is essential for walking © decade3d / Fotolia
In the early stages,arthroscopy can counteract ankle arthrosis. This allows mobility to be improved by removing anterior bone noses on the tibia bone.
In the case of advanced ankle arthrosis, the main surgical and therapeutic measures available are ankle fusion and ankle endoprosthesis.
Stiffening of the ankle joint for ankle arthrosis
Stiffening of the ankle joint (arthrodesis) can significantly reduce pain in most patients. Alongside prosthetic treatment, ankle arthrodesis is the method of choice for treating ankle arthrosis. It is performed in many clinics.
The video shows the surgical procedure for arthroscopic ankle joint fusion:
The technique of ankle arthrodesis (fusion) has been further developed in recent years. The cartilage remnants of the damaged joint surfaces are removed together with the pathologically altered bone layer.
The tibia and talus are firmly fixed internally by inserting screws and/or a stable-angle plate. This allows them to heal together in a similar way to a fracture. Existing axial deviations in the ankle joint are corrected and straightened by cutting off bone wedges of a defined size. This is an important prerequisite for being able to place the foot straight on the ground.
The stiffening of the ankle joint is generally well compensated for. It enables the patient to walk smoothly and unobtrusively without special shoe fittings.
Artificial joint for osteoarthritis of the ankle
Stiffening is still considered the gold standard procedure in most clinics. Under these circumstances, however, an ankle joint prosthesis is the better choice:
- If both ankle joints are affected, or
- if the patient has high demands in terms of maintaining mobility.
The prosthesis avoids overloading the adjacent tarsal joints and protects them from secondary osteoarthritis.
Patients with inflammatory polyarthritis in particular benefit from an ankle prosthesis. They have usually already undergone several operations on the lower extremities. For them, an ankle joint prosthesis means maintaining overall mobility and a positive change in gait.
Endoprosthetic replacement therefore has advantages over arthrodesis, particularly in cases of inflammatory destruction of the upper ankle joint.
Based on the type of construction, ankle joint endoprostheses can be divided into
- uniaxial prostheses,
- semi-coupled two-component prostheses (hinge principle),
- multiaxial two-component prostheses ("ball-and-socket principle") and
- three-component prostheses.
Three-component prostheses with mobile and fixed inlay (polyethylene insert) replace
- either only the central joint section between the tibia and talus, or
- also the inner and outer shoulder area of the talus.
The metal components are specially coated. This allows the bone to grow in and makes it possible to dispense with anchoring with cement. Thanks to the highly developed designs, the systems today generate only minimal abrasion. This significantly reduces the risk of loosening and the reoperation rate.
Which ankle joint prosthesis achieves the best results?
The upper ankle joint not only enables pure hinge joint movement. When walking, various joint movements take place around multiple moving axes:
- glide,
- slight inversion and eversion and
- rotation.
Uniaxial two-component prostheses with a hinge joint principle therefore exhibited high loosening rates. The problem with multiaxial two-component prostheses was the often inadequate joint stabilization.
With the above-mentioned modern three-component prostheses, the physiological axes of movement are imitated much better. In follow-up examinations, the three-component prostheses showed significantly better results than the old two-component prostheses. The complication and loosening rate was significantly lower and the mobility achieved was greater.
The cementless implantation of the three-component prostheses also has advantages if explantation is necessary. Explantation refers to the subsequent removal of a prosthesis, for example because it has become loose(replacement operation). Less bone is lost during explantation. This means that a prosthesis can be replaced or fused safely.
Biomechanical studies show that three-component prostheses have normal inward and outward rotational and tilt stability. Three-component prostheses are currently best able to ensure physiological movement in the upper ankle joint. This is supported by pressure and force measurements under the foot during gait.
The upper ankle joint prosthesis in the form of a three-component prosthesis is a good treatment concept for ankle arthrosis.
