Syndesmosis surgical intervention

Understanding the syndesmosis and its functions

The syndesmosis is a joint that connects the 2 bones of the leg (the tibia and the fibula) at the level of the ankle. This complex structure is composed of several ligaments, including the anterior tibiofibular ligament, the posterior tibiofibular ligament, the interosseous ligament, and the transverse ligament. These ligaments play an essential role in maintaining stability and mobility between the bones, thus enabling the fine functioning of the ankle.

Above the ligamentous structures is the interosseous membrane, which is a fibrous structure stretched between the fibula and the tibia. This membrane helps keep the two bones in place and supports the body’s weight, distributing forces evenly during movement.

Role of the syndesmosis in ankle mobility

The syndesmosis is essential for the mobility and stability of the ankle. It allows for movements of external rotation, translation, and ascent of the fibula relative to the tibia. These movements are very important on uneven terrain, on slopes, and during ascent.

The ankle helps absorb shocks and distribute loads during dynamic movements, thereby protecting the bony and joint structures of the ankle. This capacity for absorption and load distribution is especially important for athletes or during intensive physical activities.

It should be kept in mind that during normal walking, the pressure passing through the ankle is about 5 to 6 times the body weight per step. These forces are significantly increased during fast walking, running, or jumping.

The syndesmosis therefore plays an important role in the stability and mobility of the ankle, with adaptive movements that vary according to physical activity and terrain.

Indications for surgical treatment of the syndesmosis

Surgical intervention of the syndesmosis can be considered when one or more ligament bundles are injured. Symptoms can range from mild pain, to ankle instability, to valgus deformity of the ankle. These lesions may be caused by severe ankle twists, falls, or direct impacts that compromise the integrity of the syndesmosis, this essential joint that stabilizes and maintains the proper distance between the tibia and fibula. Here are some clinical situations that may require surgical intervention:

• Ruptures of the syndesmotic ligaments: These ruptures occur when the ligaments holding the syndesmosis are stretched or torn.
• Associated fractures: Ankle fractures involving the syndesmosis require surgical stabilization for optimal functional recovery.
• Chronic ankle instability: When repeated or poorly treated injuries lead to chronic ankle instability with syndesmotic lesions, a ligament repair of the ankle and syndesmosis stabilization procedure is performed.

Symptoms and Diagnosis of Syndesmotic Lesions

Symptoms of a syndesmosis injury generally include sharp pain, swelling, and ankle tenderness that may radiate up to the knee due to increased stress on the interosseous membrane. In the case of an isolated syndesmosis injury, diagnosis is made through clinical examination. It is more difficult to diagnose a syndesmotic injury when there are associated ankle ligament injuries, so it is necessary to systematically test the syndesmosis in cases of chronic painful ankle. In the context of a fracture, radiographic images may show signs of syndesmotic involvement. In cases of operated ankle fracture, arthroscopy systematically performed with osteosynthesis will allow to confirm the lesions and then the quality of syndesmosis stabilization.

Here are the various available methods for diagnosing a syndesmosis injury:

• Interview: The traumatic mechanism causing the pain often allows suspicion of a syndesmosis lesion.
• Physical examination: In the case of syndesmosis pain, the patient presents a characteristic gait with an antalgic limp, weight bearing in external rotation and slight plantar flexion of the ankle to limit pain. Several clinical maneuvers can detect syndesmosis injuries; these generally consist of inducing pain by stressing the syndesmotic ligaments.
• Weight-bearing ankle X-rays: Contrary to popular belief, this is probably the most effective examination for assessing syndesmotic injuries and their evolution. The analysis is bilateral and comparative, searching for the presence of a diastasis between the tibia and talus, and also allows evaluation of the centering of the fibula at the level of the tibial tubercles.
• Magnetic resonance imaging (MRI): This allows detailed visualization of ligament structures and identification of injured ligament bundles. However, MRI is not perfect for analyzing ligament injuries. Some ligaments look abnormal on MRI but are mechanically competent; conversely, ligaments may appear healthy even though they lack sufficient mechanical quality to ensure their stabilizing role.
• Computed tomography (CT) scan: The scanner, when performed in a comparative manner, more precisely analyzes the centering of the fibula within the tibial notch defined by the two tibial tubercles.
• Ultrasound: This examination allows dynamic analysis of the syndesmosis and can also assess ligament injuries, mainly lesions of the anteroinferior bundle of the syndesmosis.

Surgical techniques for the syndesmosis

Surgical techniques for syndesmosis stabilization relied on stabilization with screws or a screwed plate, with screws passing successively through the fibula and the tibia to clamp and contain the fibula in the intertubercular tibial notch. This technique is still used in traumatology for the management of ankle fractures, and also in the management of syndesmosis osteoarthritis requiring stable fixation with the interposition of a graft to limit excessive clamping of the malleolar clamp. For acute injuries, the principle of screw fixation enables immediate stability of the syndesmosis, allowing for ligament healing. The syndesmosis will then tend to regain its slight mobility, which may lead to a material fracture.

For this reason, syndesmosis stabilization with screws requires removal of osteosynthesis material three to four months after stabilization. The main disadvantage of this technique is the necessity of achieving perfect reduction of the syndesmosis to avoid any centering, clamping, or tension problems of the syndesmosis. Currently, the most reliable way to accurately reduce the fibula into the tibial notch is still debated. The other drawback is the need to remove the material 3 to 4 months after surgery, which corresponds to the postoperative period when patients start to regain use of their ankle.

Development: dynamic stability

There is another, more recent syndesmosis stabilization technique, which consists of stabilizing the syndesmosis dynamically with a double button system. The principle is to create a tunnel between the fibula and tibia to place a button system with one button applied to the tibia and the other to the fibula. These buttons are connected by a very strong tightening thread that allows for stabilization of the syndesmosis by fibrosis of the syndesmotic ligaments.

The theoretical advantage of this technique is that there is no hardware removal. However, in most cases, the buttons will need to be removed as they can cause discomfort with burning sensations near the buttons, even burns that may extend to the lateral and medial sides of the leg. Ultimately, the main argument for using a dynamic fixation system with a double button for the syndesmosis is adjustability. The tightening of the button system is performed with the ankle held at 90°, which corresponds to tensioning of the syndesmotic ligaments. Even in cases of excessive initial tightening, the thread will find its position in the bone as weight-bearing and ankle mobility return. The risk of fibula malposition in the notch is therefore limited.

Recovery and post-operative care

Immediately after the operation

After a syndesmosis operation, or ankle surgery in general, the aftercare requires:

• Monitoring: You will be closely monitored for any possible complications, such as bleeding or infection.
• Pain management: Painkillers will be administered to control the pain, which is essential for starting rehabilitation in good conditions.
• Immobilization: Your ankle may be immobilized in a non-weight-bearing cast initially, or in an ankle brace with weight-bearing allowed.

It is important to follow your medical team's advice carefully and to report any unusual pain or worrying symptoms.

Rehabilitation and long-term follow-up

The rehabilitation phase is essential to regain optimal function of your ankle. Here are the typical steps you may encounter:

• Physiotherapy: Usually starts a few weeks after the operation, depending on your surgeon's recommendations. It aims to restore mobility, strength, and function of the ankle.
• Progressive exercises: Under the supervision of your physiotherapist, you will start with light exercises, gradually increasing in intensity and complexity.
• Regular follow-up: Regular appointments with your surgeon are essential to monitor your progress and adjust the treatment if necessary.