Introduction

The ankle joint is prone to injuries. It is considered one of the most commonly affected joints in the human body (1). This joint mainly consists of three bones of the body, which are the tibia, fibula, and talus. It is known that the lower ends of the tibia and fibula together form a mortise that connects with the trochlea of the talus. Maintaining stability and alignment in this connection depends on structures, including the ligaments (medial and lateral), joint capsule, and tibiofibular syndesmosis (2). The primary task done by syndesmosis is to serve as a joint that connects the tibia and fibula enabling a range of motion between them. There are four ligaments in the leg: the tibiofibular ligament, the inferior tibiofibular ligament, the transverse tibiofibular ligament, and the interosseous tibiofibular ligament (3, 4). Additionally, a membrane (IOM) is a thick sheet-like structure extending from the proximal to distal ends of the tibiofibular joint, separating different compartments within the leg (5). Usually, syndesmosis preserves both integrity and alignment of the ankle mortise during weight-bearing activities and motion. It effectively withstands axial, rotational, and translational forces that impact upon this joint. During foot movement towards shin alignment, dorsiflexion causes broader engagement between anterior parts of the talus with mortise leading to slight lateral displacement along, with the posteriorly directed proximal force exerted on the fibula (6). During the movement of the foot (plantar flexion), the back part of the talus bone connects with a specific joint called the mortise. This connection causes the fibula bone to be pulled towards the middle, front, and bottom (7, 8). One important structure responsible for preventing rotation and forward movement of the fibula is known as the Anterior Inferior Tibiofibular Ligament (AITFL). The PITFL is the primary restraint to internal rotation and posterior translation of the fibula (9, 10). The TTFL reinforces the PITFL and prevents excessive widening of syndesmosis. The IOTFL is a thickening of the IOM at its distal end and prevents proximal migration of the fibula. The IOM also contributes to load transfer from the fibula to the tibia. Syndesmosis injuries are relatively common and account for 1-18% of all ankle injuries. They are often associated with ankle or lower leg fractures, especially Weber type C fractures. However, they can also occur in isolation or with other soft tissue injuries. Injuries to syndesmosis are commonly caused by rotation of the foot or excessive movement of the ankle in a downward direction. Through this instability may appear and this weakens the joint area. Syndesmosis injuries can have an impact on patients causing discomfort and limitations. They can affect the function and mechanics of the ankle joint resulting in pain, swelling, instability, restricted a certain range of movement, decreases strength and endurance, and changes in walking patterns. If not properly treated or left untreated altogether, syndesmosis injuries can result in long-term complications such as arthritis, improper healing of bones (malunion), failure of bones to heal (nonunion) infection, or issues with implanted hardware. Generally speaking, outcomes for syndesmosis injuries are favorable; however, some patients may not fully. Experience satisfaction with their recovery. Several factors can influence these outcomes, including severity and duration of injury; presence or absence of associated fractures or soft tissue damage; accuracy and stability achieved during realignment and fixation; occurrence of complications or re-injury; and adherence to care instructions and rehabilitation programs. This paper aims to provide a review based on existing literature concerning anatomy, biomechanics, and treatment options for syndesmosis injuries.

Methodology

On October 1, 2023, we conducted a literature review on the topic of Anatomy, biomechanics and treatment of tibiofibular syndesmosis injuries. Due to this review, we had to search the Medline and PubMed databases, using medical subject headings and various related terms in each database. We used keywords such as tibiofibular syndesmosis, ankle joint, ankle sprain, ankle fracture, ankle stability, etc. We also searched Google Scholar manually. We did try to check the reference also of the retrieved papers for additional sources. To ensure the quality of our review, we applied inclusion criteria, such as excluding papers published before 2008 up to 2023 and preferring English language publications. We did not apply any restrictions based on age or publication type.

Discussion

There are several types of ankle joint injury that may occur to an individual but among them syndesmosis injuries are most common. They are more likely to happen in males, rather than females individual with a ratio of 2:1 to 3:1, between males and females (11). Patients who commonly suffer from syndesmosis injuries are usually 30 years old. These types of injuries often occur during sports activities that involve changes, in direction pivoting or jumping. There are several other sports such as soccer, rugby, football etc. are related to these injuries. However, it is important to note that syndesmosis injuries can also happen due to falls, car accidents or workplace hazards.

Biomechanics

When the foot become rotated externa way, severe injury like syndesmosis may occurs to the person. The rotation mostly occurs externally or excessive upward or downward movement of the ankle. These actions can weaken one or more parts of the syndesmosis leading to instability or misalignment of the ankle joint. External foot rotation is typically the cause of syndesmosis injury (12). This happens when the foot is firmly planted on the ground, and the body rotates around it or when external force forcibly rotates the foot outward. This type of mechanism can damage parts of the syndesmosis, starting with AITFL, then IOM, IOTFL, and finally PITFL and TTFL. The extent and severity of injury depend on how much external rotation occurs. Mild external rotation might only cause damage to AITFL, resulting in an incomplete syndesmosis injury. A moderate rotation of the ankle outward can lead to injuries in the AITFL and the IOM, causing a syndesmosis injury with displacement. On the other hand, a severe rotation of the ankle outward can harm all components of the syndesmosis resulting in a syndesmosis injury with significant displacement and widening of the mortise. Syndesmosis injuries can also occur due to excessive downward movement of the foot (13, 14). When raising foot towards the shin is referred to as dorsiflexion while pushing it down away, from the shin is known as flexion. These movements exert forces on the syndesmosis ligaments, which can lead to complete tears. Dorsiflexion can also cause compression forces on the syndesmosis, potentially resulting in fractures involving tibia or fibular spurs. Likewise, plantarflexion can exert distraction forces on syndesmosis, potentially leading to avulsion or fractures involving fibular tubercles.

Classification

There are many categories of syndesmosis injury available, but they are all categorized by different factor which may include the way they occur, their severity, stability, the extent of displacement, or any associated fractures. However, there isn't an agreed-upon or validated classification system for syndesmosis injuries. Some of the employed classification systems include.

Lauge-Hansen classification: This classification system provides a way by which the category of the ankle fracture can be determined. It consists of four categories: supination adduction (SA), supination rotation (SER), pronation abduction (PA) and pronation external rotation (PER) (15). Each category has four stages that indicate the involvement of parts: the medial malleolus, lateral malleolus, posterior malleolus, and syndesmosis. Syndesmosis injuries typically occur in stage 4 of SER and PER fractures as in stages 2 and 4 of PA fractures.

Weber classification: This classification system for ankle fractures utilizes analysis to categorize them based on the multiple position of the fracture which has connection to the syndesmosis. here are three categories; category A, category B and category C. Injuries related to syndesmosis are commonly associated with category C fractures whereas category B fractures can also result in injuries (16).

AO/OTA classification: This classification system provides a way to categorize fractures based on their location, shape, and the extent of displacement (17). There are three categories; Group A, which includes fractures outside of the joint Group B, for fractures within the joint and Group C, for fractures fully located within the joint. Each group is then divided into three subcategories that classify the patterns: Subcategory 1, for fractures Subcategory 2 for wedge shaped fractures and Subcategory 3, for fractures. In each subgroup there are three indicators that show the extent of displacement: Indicator A, for displacement Indicator B for displacement and Indicator C, for displacement. Syndesmosis injury primarily occurs in Group C fractures in C3 fractures. However, it can also occur in some Group B fractures, like B2 and B3.

Clinical manifestation

Disruption or weakening of syndesmosis can result in instability or misalignment of the ankle joint. Instability refers to the joint losing its motion and function because the ligaments are unable to maintain its stability and alignment. Misalignment on the other hand, refers to the position or orientation of the joint caused by bone displacement or angulation relative to each other (18) (19). The degree and direction of instability and misalignment can vary depending on the severity and mechanism of injury. The common forms of instability and misalignment include Diastasis which occurs when there is a separation or gap between the tibia and fibula at their joint, causing displacement of the fibula away from the tibia. Diastasis can be measured by determining the distance between the border of the fibula and the lateral border of the tibia at dome level on anteroposterior radiographs. In adults, a normal value is than 6 mm, while in children it is, then 4 mm (20). Rotation refers to the repositioning of the fibula in relation to the tibia caused by either internal rotation around its long axis. To measure rotation, we look at the angle between the fibula's axis and a line that is perpendicular to the plafond on lateral radiographs. Typically, a normal value falls between 5 to 10 degrees. Translation, on the other hand, relates to alternation of the actual position of the fibula which would correspond to the tibia due to anterior or posterior displacement along its long axis. To measure translation, we determine the distance between the border of the fibula and that of the tibia at the level of the dome on lateral radiographs. A normal value should be 2 mm. Angulation refers to the alteration in the positioning of the fibula in relation to the tibia caused by either downward displacement along its short axis. To measure angulation, one can determine There are mainly presence of angles between the axis of the fibula and a line parallel to the plafond on lateral radiographs. Typically, a normal range for angulation falls within 0-5 degrees. The syndesmosis's instability and misalignment can negatively impact how the ankle functions and moves. It can result in pain, swelling, reduced stability, and limited mobility of the ankle joint. The misalignment can cause unevenness and imbalance in the ankle mortise leading to pressure and stress on the surfaces where the tibia, fibula, and talus meet. This can lead to damage to cartilage lesions in bone and cartilage, arthritis, or improper healing after injury.

Management

This study delves into the management of syndesmosis injuries, a critical consideration for healthcare providers. Successful management relies on conducting an assessment of the patient's health status considering their preferences and expectations. This must be coupled with a judicious review of existing evidence and clinical guidelines. Broadly, the management options for syndesmosis injuries encompass no-operative and operative approaches.

Non-operative Treatment

Non-surgical treatment is mainly used for stable or slightly displaced syndesmosis injuries that don't affect the function or mechanics of the ankle joint. This approach involves two parts; immobilization and limiting weight bearing, followed by rehabilitation (21, 22). Immobilization helps protect the injured structures and promote healing. There are methods, like casting using a boot or wearing a brace, to restrict motion in the ankle joint. At the time, limiting weight bearing with crutches, walkers, or canes aims to reduce strain on the affected limb. The duration and level of immobilization and weight-bearing restriction depend on factors like how severe and long-lastingthe injury's well as patient-reported pain, swelling, and stability. Typically, immobilization lasts around 4 6 weeks while maintaining restrictions on weight bearing for 6-12 weeks. After that, progressive rehabilitation focuses on restoring ankle function and mechanics by prospering the limb's range of movement, strength, endurance, balance, and coordination. Rehabilitation includes exercises, manual therapy techniques, and various therapeutic devices tailored to each individual's needs under the supervision of therapists or orthopedists. It usually begins after removing immobilization and gradually reduces weight-bearing restrictions. This phase may last from 3-6 months until the patient fully recovers or reaches their desired level of satisfaction. Non-surgical treatment can lead to results, although patient experiences may vary. The success depends on factors such as diagnosis, consistent care, patient cooperation with prescribed protocols, and the possibility of complications, like stiffness, muscle wasting, limited mobility, infection, blood clotting issues or reflex sympathetic dystrophy. Therefore, it is crucial to select and monitor patients during surgical management of syndesmosis injuries.

Operative Treatment

Surgical treatment is only recommended for syndesmosis injuries that are unstable or cause disruption to ankle joint function and biomechanics. In some cases, the main focus is fixing the syndesmosis using screws, suture buttons, or other devices, followed by rehabilitation. The objective of fixation is to restore the alignment and stability of the tibiofibular joint. The choice of fixation device depends on factors like surgeon preference, the type and severity of the injury presence of fractures or soft tissue injuries well, as evidence-based guidelines. Common fixation options include screws that create a connection between the fibula and tibia, suture buttons that provide fixation, and various other devices like plates, staples, rods, nails, or anchors with different designs and mechanisms. The surgical procedure for fixation involves anesthesia administration, patient positioning for surgery incision making, reduction of the joint to its position, and placement of the chosen device in position within the wound area, followed by closure. This approach requires expertise in surgery from surgeons. After surgery, immobilization is necessary based on factors to management but also taking into consideration the choice and stability of the chosen fixation device. Typically, immobilization lasts for 4 to 6 weeks, while weight-bearing restrictions may persist for 6 to 12 weeks. Progressive rehabilitation, similar to its counterpart, aims to restore ankle function and biomechanics through a personalized program overseen by physical therapists or orthopedists. This phase occurs after the removal of immobilization and the gradual reduction of weight-bearing restrictions, typically lasting between 3 and 6 months. The ultimate goal is to achieve recovery or patient satisfaction. Surgical intervention has shown outcomes in treating syndesmosis injuries. Fixation devices have their own benefits and drawbacks. While screws provide stability, they can lead to stress concentration and hardware irritation. It may require removal. On the other hand, suture buttons offer fixation, with fewer hardware complications and the potential to avoid removal. However, there might be some difficulties in obtaining them and inserting them properly.

Conclusion

The treatment of syndesmosis injuries requires an assessment of patient factors and following evidence-based guidelines. Both non-surgical and surgical methods have their advantages and also would be chosen based on the conditions of the injury and the patient's requirements. Regardless of the chosen method, it is vital to monitor and provide rehabilitation to ensure the possible outcomes for patients with syndesmosis injuries.

Disclosure

Conflict of interest

There is no conflict of interest.

Funding

No funding

Ethical consideration

Non applicable

Data availability

Data that support the findings of this study are embedded within the manuscript.

Author contribution

All authors contributed to conceptualizing, data drafting, collection and final writing of the manuscript.