Syndesmosis (Membrana interossea) is the term used to describe the connective tissue membrane that connects the fibula and shinbone and is thus necessary for stabilizing the ankle joint. In the lower part, close to the ankle, the syndesmosis guarantees this stability in cooperation with the outer and inner ligaments. If the ankle joint is twisted or compressed, the syndesmosis (syndesmosis tear) or a part of it can be torn. Especially an excessive external rotation of the ankle bone (talus) bears the danger of a syndesmosis injury. This can also occur if no bony structures are affected, so that the exclusion of a fracture in the area of the ankle joint is not sufficient to rule out a syndesmosis tear.
Origin
The syndesmosis tear is a classic sports injury and occurs more frequently in sports where accidents involving severe twisting of the ankle joint are likely. These include skiing to the same extent as movement-intensive ball sports.
Diagnosis
A syndesmosis tear sometimes causes severe pain when the ankle joint is strained, which often makes it impossible to fully load the affected leg. In most cases, the joint also swells considerably, causing painful pressure and painful external rotation. Since the radiological exclusion of a bone injury does not rule out an injury to the ligamentous apparatus, the diagnosis is primarily clinical.
The local pressure pain and the behaviour in the stress test during external rotation of the ankle or during compression of the tibia and fibula (syndesmosis compression test) can give an indication of the extent of the injury. Conventional x-rays and magnetic resonance imaging (MRI) are often helpful and can support the diagnosis. Magnetic resonance imaging can also be useful in planning any necessary surgery. If a syndesmosis rupture is suspected, other injuries such as a torn outer ligament, an ankle fracture and fractures of the tibia or fibula may also be considered and must be excluded.
Therapy
In the acute phase, the affected extremity must be elevated and cooled. It is also advisable to take anti-inflammatory drugs (ibuproipfen, paracetamol, aspirin) for pain therapy. The primary goal of long-term therapy is to restore the stability of the ankle joint and thus the ability to cope with stress and sport.
In this context, a distinction must be made between the tearing or incomplete tearing of the syndesmosis and the complete tearing. In the case of an incomplete tear, conservative treatment with immobilization in an orthosis is possible. In case of a complete rupture of the syndesmosis, associated with severe pain and instability of the upper ankle joint, the conservative regime can be prolonged.
The affected extremity is immobilized with a lower leg walking cast or a removable brace for about six to ten weeks. The exercise can be performed in the absence of pressure pain and with painless possible external rotation of the calcaneus and should be accompanied by a physiotherapist as soon as full weight bearing capacity exists. If the heel bone is grossly malaligned, surgical therapy may be necessary.
Depending on the procedure, the joint is stabilized with an ankle-spanning set screw and the ligamentous apparatus is reconstructed with absorbable sutures, if necessary, or a minimally invasive procedure is performed using permanent implants remaining in the body. In the first case, metal removal under short-term anesthesia will be necessary at a later point in time, even before full weight bearing begins. Postoperatively, supported by forearm walking aids, a partial loading of the injured joint is possible.
