- 1 Definition / Description
- 2 Clinically Relevant Anatomy
- 3 Epidemiology / Etiology
- 4 Characteristics / Clinical Presentation
- 5 Differential Diagnosis
- 6 Diagnostic Procedures
- 7 Outcome Measures
- 8 Examination
- 9 Medical Management
- 10 Physical Therapy Management
- 11 Key Evidence
- 12 Resources
- 13 Clinical Bottom Line
- 14 References
Definition / Description
The lower leg is composed of two bone pieces, the tibia and the fibula. Those two bones form a fibrous joint, a so called syndesmosis. The tibia and fibula are attached to each other by a connective tissue, composed of collagen- and elastic fibres. The tissue is strengthened by several ligaments. However, if you sprain your ankle, it is possible that the tissue between the two bones breaks. This can lead to a tibiofibular diastasis or syndesmosis, which is a separation of the tibia and the fibula. The dissolution is caused by the rupture of the tibiofibular ligaments of the ankle. The talus that fits into the tibiofibular fork, detaches and becomes unstable. As a result, the talus tilts and other ligaments can be ruptured. Ankle instability or arthritis can be the result of diastasis  .
Clinically Relevant Anatomy
The Art. tibiofibularis distalis is a typical syndesmosis. It connects the distal fibula, tibia and talus. At this level, the tibia and the fibula are attached to each other by syndesmotic ligaments. It includes an anterior and posterior inferior tibiofibular ligament, the tibiofibular interosseous ligament and the transverse tibiofibular ligament and the membrane interrosseus.  . Those ligaments and the membrana interossea act to statically stabilize the joint . The syndesmosis is placed between the incisura fibularis tibiae and the medial extremity of the malleolus lateralis .The purpose of these ligaments is to hold the tibia and the fibula together when the joint is loaded .
Those ligaments have different functions in the tibiofibular joint. The anterior tibiofibular ligament prevents extreme uncontrolled movement of the fibula and also external rotation of the talus. The superficial part of the posterior tibiofibular ligament is in conjunction with the anterior tibiofibular ligament and holds the fibula tight in the incisura fibularis tibiae. The deep part of the posterior ligament is also known as the ‘transverse tibiofibular ligament’ and is a part of the articulating surface of the talus, it prevents a posterior translation of the talus. The interosseus tibiofibular ligament acts like a spring and allows a small separation of the lateral and medial malleolus during dorsiflexion of the ankle joint .
Epidemiology / Etiology
The incidence rate of ankle sprains is very high. Older people but also many young people and athletes can suffer from tibiofibular syndesmosis. In many countries ankle instability is the most common ankle injury in the world of sport. Ankle instability can be the result of tibiofibular syndesmosis . If this injury is left untreated, chronic pain, muscular weakness and degenerative arthritis may arise . Of course there are factors that can stimulate tibiofibular diastasis. When practicing a sport, the chance of hurting your ankle is higher. When your ankle is under a lot of stress, overloading may occur. Other factors such as intrinsic- and extrinsic factors may also play a role. Intrinsic factors include age, gender, height, weight, and body mass index. The playing surface, the shoe type or the level of competition can be categorized under the extrinsic factors. The history of previous ankle sprains is also an important aspect to be taken into consideration. Finally, the neuromuscular control and postural control are essential. When muscles are insufficiently developed, stability and postural control are decreased.
When practicing a sport, it is important to do pay attention to control. Imposing the correct load capacity to our body is very important. Too much pressure on our body, more specifically the ankle is not good and can cause dangerous problems .
Characteristics / Clinical Presentation
Tibiofibular diastasis is often associated with extensive ligamentous tears . Consequently, this decreased stability leads to ankle instability of the joint. Tibiofibular diastasis can also be associated with external rotation or abduction injuries of the ankle or eversion of the talus and hyperdorsiflexion that can cause a deranged axial movement.
This condition may occur without an associated fracture, but may also occur with a fracture where there is rupture of the internal malleolus or rupture of the internal lateral ligament. There is also a fracture of the posterior part of the tibia extending into the joint. There are large forces acting on the talus that can also lead to a tibiofibular diastasis.
It will not rotate in a similar proportion to the force but it will result in a translocation of the fibula in the lateral direction.
This causes a tear of the least strong syndesmotic ligament namely the anterior tibiofibular ligament, when this ligament is completely torn there is a lateral translation with an external rotation of the fibula that increases the contact pressure   .
In a static stance phase, the ankle joint is stable, so that the body weight and the pressure are distributed over the entire foot and ankle. In this way, the body weight can be carried. During the movement of the foot, there are different working forces that operate on the ankle. The ankle joint can naturally only make a minimal movement between the talus and the ankle fork. When an excessive force creates too much pressure on the ankle, a tibiofibular diastasis is likely to occur. The tibiofibular diastasis is caused by different mechanisms. These mechanisms ensure a disruption of the tibiofibular syndesmosis. The syndesmosis ligaments ensure that there is no lateral translation. This means that if there is a disruption of these ligaments, there may be a great instability. The anterior inferior tibiofibular ligament is the weakest ligament of the ankle joint and can easily tear. When it is completely torn, there is a lateral translation of two millimetres of the fibula, a shortening of two millimetres, and an external rotation of five degrees which also causes an increase in contact pressure. The external rotation is the main mechanism of the damage. Here, the talus rotates in the same proportion to the applied force. When a force of 87N is applied, a two millimetre lateral translation occurs.  
Complaints of Patients with chronic disruption of the distal tibiofibular syndesmosis have generally after their initially injuries of the ankle persistent pain while the joint is bearing weight. Pain is provoked when the tibiofibular is stretched this is a combination of dorsiflexion and external rotation. When those patients are walking on uneven ground, they complain from instability of the syndesmosis, as a giving way. 
Tests are able to find out if the result of the diagnosis is a tibiofibular diastasis. To know whether the injury is serious or not, first it has to be determined how long the patient suffers from pain. Acute pain lasts 3 weeks, subacute pain takes 3 weeks to 3 months and when the pain is dominating for more than 3 months, it is called a chronic pain.
Subsequently a physical examination, including the palpation of the malleoli and ligamentous area, is important. So you can exclude some injuries. Afterwards, you can start with the execution of some tests, like the squeeze test, the external rotation test and the dorsiflexion test. When these tests are positive, there is a chance that a syndesmotic injury is present. The fibular translation test, the Cotton test, and the crossover leg test, can also be used. But in order to find out if these tests are good, they must have a high confidence interval.
To be absolutely sure about whether a syndesmotic injury is present or not, the golden standard rule may be applied. A radiography can clearly demonstrate what is going on .
Edwards and DeLee classified traumatic syndesmotic diastasis in a latent or a frank form. A frank diastasis can be divided into 4 degrees:
o Type1 :
Type I injuries demonstrate straight lateral fibular subluxation without plastic deformation of the fibula and are best treated by open reduction, removing any intervening soft tissue, and stabilization with a tibiofibular screw.
Type II injuries are injuries with straight lateral subluxation of the fibula due to plastic deformation of the distal fibula. Fibular osteotomy can be used for reduction, before the internal fixation.
o Type 3:
Type III injuries consist of posterior rotation subluxation of the fibula. The talus superiorly will be disrupted, resulting in divergence of the tibia and fibula.
o Type 4:
The talus is dislocated superiorly causing a wedge effect between the tibia and fibula resulting in an increase of the intermalleolar distance. Type III and IV injuries can usually be treated by closed manipulation and plaster immobilization. (Level of Evidence 3)  
Further, there is ‘The West Point Ankle Grading System’, that classifies pure ligamentous syndesmosis injuries into three grades. Grade I suggests that there is no instability. Grade II means that there is some evidence of instability and grade III declare instability in the ankle.
But for the moment, there is still a doubt about the classification systems. Further research is required .
Swelling in the ankle, inability to bear weight, pain in the anterolateral aspect of the ankle, pain during the push-off phase of gait and giving way are a few symptoms of a tibiofibular diastasis.  But this disease has no specific symptoms. It is difficult to differentiate this disease from other lateral ankle injuries. If the patient has a lot of high ankle pain, proximal till the anterolateral aspect of the leg, then this is probably a serious condition. The only way to know which disease it is, is through the tests and investigations that should be carried out. 
One of the several options to recognize a tibiofibular diastasis is by taking a radiography from the ankle. With this radiography, a fracture, a diastasis or an avulsion can be detected. When a syndesmosis injury is being diagnosed, a space greater than 6 millimetres above the plafond and a space between the malleolus medialis and the talus can be seen. In case of a tibiofibular diastasis, a CT scan can provide more options than a radiography.
CT scans are more accurate than radiographs because they can show small avulsion fractures and they can clearly show the link between the fibula and tibia as well. If there is any suspicion of tibiofibular diastasis, the contralateral limb should be examined. That way, the examinator can compare both limbs and look for the differences. There may be a difference in displacement greater than or equal to two millimetres. Another option to detect a syndesmosis injury, is with MRI. MRI can show the structures of the syndesmosis.
MRI has 93% specificity and 100% sensitivity for Anterior Inferior Tibiofibular Ligament (AITFL) injuries and 100% specificity and sensitivity for Posterior Inferior Tibiofibular Ligament (PITFL) tears. The sensitivity and specificity may vary depending on the severity of injuries. Patients with AITFL injuries can easily undergo an ultrasound scanning because it is cheap and quick.
With ultrasound scans, a clear space can be detected that increases with sensitivity and specificity during stress ultrasonography.
But, ultrasonography cannot detect the secondary injuries on the bone and cartilage. X-rays are useful to detect or exclude the fractures. But X-rays have a disadvantage and that is that the soft tissue (eg. Ligaments) cannot be directly seen on X-rays. Arthroscopy is indispensable for diagnosis of syndesmosis injuries because then they can know how they have to handle the secondary injuries to the bone and the cartilage. Arthroscopy is also really important for the management of both syndesmotic and osteochondral injuries. 
During the anamnesis, the clinician should ask about the patient’s history of the injury. Once the history is sufficiently asked out, the clinician can decide whether or not a basic function examination has to be performed. The injury is present, there are several tests to investigate the disease .
The tests can only be used when there is no pain or swelling associated to the fracture  :
1. External rotation test
2. Squeeze test
3. Dorsiflexion compression test
4. Heel thump test
1. External rotation test is a test to identify a tibiofibular syndesmosis. The clinician has to maintain the ankle in dorsiflexion with an external rotation during a stabilized leg on the affected limb. The test can be implemented while the patient is sitting or lying down. The test is positive when there is pain provoked in the syndesmosis region and has a specificity of 84,5 and a sensitivity of 0,20 .
2. Squeeze test is another test to identify a tibiofibular syndesmosis. It is also a pain provocation test. The patient is in a supine position while the clinician grasps the leg of the patient, midway of the calf muscle on the affected limb, and perform compression with both hands. The test is positive when the patient experiences pain in the syndesmosis region .
3. Dorsiflexion compression test is an active provoked test while the patient charges his ankle on both malleoli. If the test is positive the patient will experience pain on the distal side of the fibula .
4. Heel thump test is also a provoked test while the clinician stabilizes the tibia with one hand. The other hand is used to exercise force on the calcaneus, which is in the same axis of the tibia. 
Management of the ankle injury can be divided into physical and medical therapy, the intervention is based on the severity of the syndesmotic injury, which is divided in three grades.
Grade I injuries are not treated surgically. Symptomatic treatment includes a period of rest, ice, and immobilization for comfort and assistance with rehabilitation.
For mild injuries in athletes, casting is generally not required and may impede course of therapy because of risk of disuse atrophy and stiffness.
Patients often use crutches only 1 to two weeks for comfort in a controlled ankle motion walker boot. Immobilization allows early mobilization but protects against external rotation. The patient is then switched to a functional brace usually between weeks 2 and 4.
The best treatment plan for grade II injuries is less clear. Nonoperative treatment for this injury includes initial splinting and protection from rotation as well as strict non-weight bearing status. Once swelling has retreated and the syndesmosis remains reduced on exam, the patient is transitioned to a short leg cast for 6 to 8 weeks. The patient is then transitioned to progressive weight bearing in a walking cast, and then eventually to a soft ankle brace. If conservative approach is undertaken, again, serial evaluations are needed to ensure maintenance of reduction.
Some more aggressive treatments are suggested for athletes, including arthroscopic debridement and percutaneous screw fixation; however, this approach has not yet been substantiated by biomechanical or clinical data. Early anatomic reduction and fixation ensures that the ligaments are in an optimal position for healing. Early fixation avoids the potential of a subtle missed diagnosis or for a delayed slip while attempting cast immobilization.
The consensus concerning Grade III injuries is that operative fixation is necessary to maintain anatomic reduction of the mortise and maintain ankle stability and correct alignment of bones while allowing healing. Surgical treatment should include reduction and trans syndesmotic fixation with 1 or 2 metallic screws. The patient should be placed in a non-weight bearing cast for 6 weeks. The preferred timing for the removal of screws is at 8 to 10 weeks.
  (evidence level 5)
An alternative to simple metallic screws is the Assembled bolt-tightrope system which can be used to reduce the syndesmotic diastasis and provide flexible fixation in a minimally invasive fashion. It seems to be an effective alternative technique to treat syndesmotic diastasis.  (evidence level 5)
Physical Therapy Management
Exercise therapy can be initiated when a patient with a grade I injury is switched to functional brace. This includes gradual increases in range of motion and stretching with eventual balance and bicycle program additions. During this initial period patient need repeat examinations and radiographs every 1 to 2 weeks to determine continued stability. The rehabilitation can be described as a 3-phase approach. The acute phase aims at protecting the joint and decrease pain and swelling through immobilization and pain control. The subacute phase includes an increase in exercise intensity to restore strength and basic functional motion. This includes cardiovascular conditioning. The final, optional, stage has its goal of returning the patient back to sport participation with strengthening, neuromuscular training, and sport-specific exercises. Based on examination as well as ability to perform sport specific tasks, the timing of return to sport can be determined.
Physical therapy concerning grade II injuries is similar to grade I injuries: Rehabilitation should focus on range of motion, balance, proprioception, strength, and eventual return to play exercises specific to his/her sport.
Grade III injuries are first treated with surgery, after the surgery the patient should begin progressive weight bearing and range of motion exercises. These exercises can begin with the screws in place.
Rehabilitation can progress to functional activities when the patient demonstrates the ability to perform activities of daily living, ambulate on uneven/soft surfaces, and ascend/descend stairs without difficulty. Patients may return to sports participation when they have the ability to perform aggressive sport-specific tasks like running, jumping, kicking, and cutting/pivoting at competition/practice speed without alarming symptoms during or after participation. The expected time frame to return is around 12 to 14 weeks.   (evidence level 5)
Balance training is also an example of physical therapy. When there is a rupture of the ligaments in the ankle, ankle instability may occur. The consequence of this instability, is that injured patients will demonstrate poor postural control and they will use a more anterior and laterally positioned centre of pressure during a single-limb static-balance task. In the study of Mettler et al. a 4-week balance training program was set up, to determine if the centre of pressure (COP) in patients with chronic instability will change. The results showed that balance training can help. The COP location shifted from anterolateral to posterolateral. The stability of patients with chronic instability will therefore improve a little bit, but it remains to be investigated whether balance training can help on a long-term basis.  (evidence level 1b)
In the study from Lardenoye, Sacha et al., they investigated the comfort and satisfaction by patients with acute ankle sprain. In order to determine this, patients with grade II and III sprains, were divided in two groups. One group was treated with tape and the other with a semi-rigid ankle brace, both for 4 weeks. Patients who received a semi-rigid brace reported more comfort and satisfaction than patient treated with tape. The two groups reported a good functional outcome and the results of pain were similar in both groups.  (evidence level 1b)
- Del Buono, A., Florio, A., Boccanera, M. S., & Maffulli, N. (2013). Syndesmosis injuries of the ankle. Current reviews in musculoskeletal medicine, 6(4), 313-319.
- Magan, A., Golano, P., Maffulli, N., & Khanduja, V. (2014). Evaluation and management of injuries of the tibiofibular syndesmosis. British medical bulletin, 111(1), 101-115.
- Thormeyer, J. R., Leonard, J. P., & Hutchinson, M. (2012). Syndesmotic injuries in athletes, an international perspective on topics in sports medicine and sports injury. ISBN, 978-953.
We extracted all information used for this article from PubMed and Physiopedia.
Clinical Bottom Line
There is a clear lack of consensus concerning almost every aspect of syndesmotic injuries, this includes diagnosis, treatment and transition times. Recently awareness of this injury has increased, however before that there has been very little research made on the subject.
Optimizing outcomes from these complex injuries requires early recognition through awareness of mechanism of injury, a detailed physical exam, and appropriate imaging to assess for subtle changes. Successful treatment depends on early identification and timely intervention; anatomic reduction is required of any treatment modality.
While the injury is a difficult one, appropriate management can return the athlete to preinjury levels of participation, although their return will likely be delayed compared to lateral ankle sprains. 
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