The ankle is one of the joints that is most exposed to the risk of distortion and all the structures that make it up, including the tibio-peroneal syndesmosis. This is the membrane that solidates the tibia and the fibula, the two bones of the leg that go from the knee to the ankle: “The lesion of symmetry – recalls Dr. Lorenzo Di Mento, traumatologist at Humanitas – is often associated with a fracture, both in the malleolar and proximal fibula”.
A durable and elastic tissue
Syndesmosis is a particular type of joint that connects the tibia and fibula and helps maintain ankle stability. It is formed by an interosseous membrane rich in elastic fibers that ensure joint mobility. The syndesmosis plays its role also thanks to the support of a network of ligaments.
One of the most frequent ankle traumas is distortion that can most frequently result in lesion of ankle ligaments and in a smaller percentage lesion of tibio-peroneal syndesmosis.
In the vast majority of cases, distortion occurs in reverse, with the foot rotating outwards: “The distortion from which the damage to the synapse can be caused by the syndesmosis can also occur during daily activities, but more often during sport. The most at risk are those who devote themselves to disciplines such as volleyball, football, rugby or basketball, for example, both recreational and competitive”, recalls Dr. Di Mento.
The diagnosis
As a result of an ankle distortion, the doctor may also recommend some tests in the clinic to diagnose the lesion of synapse. With the external rotation stress test, the presence of pain in the ankle is evaluated by rotating the foot outwards. With the compression test, on the other hand, with the patient in a sitting position and knee flexed at 90 degrees, the leg is gently squeezed halfway through the calf: if the patient feels pain at joint level, a distortion is suspected involving the upper part of the ankle, with lesion of the tibio-peroneal syndesmosis.
Sometimes the lesion of symmetry can be misunderstood, especially when it is not associated with malleolar fracture. This may happen because the higher part of the fibula may be fractured, in which case the diagnosis could escape a clinical and instrumental examination that evaluates the ankle only”, adds the specialist.
In the operating room
The information about the lesion and the opportunity to perform surgery will be provided by first level examinations (standard ankle and leg radiographies), possibly supplemented by second-level examinations (Ankle MRI or CT without contrast medium): A significant lesion of the symmetry must always undergo surgery: the interosseous membrane keeps the malleolar clamp tightly closed so that the talus remains well centered during the ankle flexure-extension movement. Where this is not the case, the patient will complain about painful symptoms of load and movement, with a loss of his functional capacity.
The surgical operation aims to stabilize the interosseous membrane: “Depending on the type of lesion, one or two transyndesmosic screws that close the malleolar clamp can be positioned, resolving what the trauma caused. Screws are generally removed six to eight weeks after surgery, as they can limit ankle dorsiflextion.
Functional recovery resulting from a correctly diagnosed and operated synapse lesion is complete. The timing depends essentially on whether there are associated fractures, which require a healing time of about three months,” concludes Dr. Di Mento.
