Tibiofibular Diastasis

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Clinically Relevant Anatomy

Tibiofibular syndesmoses include a anterior and posterior inferior tibiofibular ligaments and the transverse ligament and membrane interrosseus. It connects the distal fibula, tibia and talus.

Mechanism of Injury / Pathological Process

Diastasis is a dislocation or separation of two normally attached bones. Here this located between the fibula and tibia and 4 different types can occur.

Clinical Presentation

Tibiofibular diastasis is often associated with extensive ligamentous tears and often with external rotation or abduction injuries to the ankle. This condition may occur without associated fracture, but may also occur with 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.

Diagnostic Procedures

In different cases tibiofibular congenital diastasis can occur.
Various deformities of the foot can be seen, an unduly prominent and distally placed medial malleolus, tibia VARA and accentuated tibial intorsion, shortening. The exact pathogenesis of congenital inferior tibiofibular diastasis is unknown.
 (Level of Evidence 3)

Outcome Measures

The measurement of tibiofibular diastasis is not easy, research shows than the CT scans may be more effective in evaluating the syndesmosis just radiagraph.

Management / Interventions

Examination will reveal swelling and discrete tenderness over the anterior tibiofibular ligament. There may be associated tenderness over the deltoid ligament. In this disorder, the squeeze test can be used.

Physical therapy management
Dysfunction: A variety of mechanisms have been reported for syndesmotic injuries; the most common is thought to be forced external rotation with ankle dorsiflexion and pronation.  
Diastasis requires surgical stabilization by transfibular screw fixation, 1 cm above the syndesmosis. The screw will primarily provide a reduction in dorsiflexion.
After inserting the screw, it is important that it is followed with 6 weeks immobilization, after 3 weeks you can use a walking cast, and later with a brace or taping.  It is important to optimize the mobility as soon as possible. Due to the immobilization period the muscles are atrophy and strengthening exercises are important.
The final treatment will provide the best possible reduction which dorsiflexion an important part of the treatment. They will also provide a good reconstruction of the articular surfaces. It is also very important that all exercises are under the pain threshold.

Differential Diagnosis

Tibiofibular diastasis without fracture can be classified into 4 types;
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.
o Type2:
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)

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