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Syndesmotic Injuries of the Ankle


- See: syndesmotic sprain

- Anatomy:
    - syndesmosis is made up of anterior-inferior tibiofibular ligament, interosseous ligament, and
            posterior-inferior fibular ligaments, inferior transverse tibiofibular ligament, and interosseous ligament;
            - these stabilize the mortise by opposing the fibula in the fibular notch (incisura fibularis tibiae);
    - section of the anterior tibiofibular ligament results in diastasis of 2.3 mm;
    - section of anterior tibiofibular ligament and interosseous ligament will result in diastasis of 4.5 mm;
    - when all 3 ligaments are sectioned, diastasis measures 7.3 mm; 
    - syndesmotic injuries are unusual in displaced Weber B fractures;
    - in the anatomic study by Snedden MH and Shea JP, the authors noted that the interosseous ligament, may have a variable
            attachment on fibula, differing between specimens in its distance above the synovial reflection or joint line; 
            - low fibula frx would disrupt interosseous ligament, can explain anatomic basis for infrequent diastasis in these ankle frxs;
    - ref: Diastasis With Low Distal Fibula Fractures: An Anatomic Rationale

- Injury Patterns:
    - isolated syndesmotic injury:
    - syndesmotic injury & fibular frx;
            - w/ syndesmosis & fibula disruption, talus can shift laterally 2 to 3 mm, even w/ deep deltoid ligament intact;

    - syndesmotic injury + medial injury:
            - > 3 mm displacement indicates that either the deep deltoid ligament or medial malleolus must be disrupted;
            - if medial malleolus is frxed & deltoid ligament is intact, rigid fixation of fibula & tibia should make
                      syndesmosis fixation unnecessary; 
    - posterior malleolus fracture
            - fixation of posterior malleolar fractures will make syndesmotic reduction and fixation easier;

- Objective Diagnosis of Syndesmotic Injury and Indications for Syndesmotic Fixation:

- Surgical Treatment Options:
       - reduction of syndesmosis (theory and surgical technique)                  
       - fixation techniques:
               - screw insertion technique for snydesmotic fixation         
               - k wire fixation:
                       - two 1.5 mm K wires can be inserted obliquely across the distal tibio-fibular syndesmosis;
                       - is a less rigid form of fixation, which allows more physiologic ankle function, and does not require early HW removal;
               - deltoid ligament repair:
                       - ref: Deltoid Ligament Repair Versus Syndesmotic Fixation in Bimalleolar Equivalent Ankle Fractures.
               - suture fixation (w/ suture button):
          - involves creation of two small drill holes through fibula and tibia (separated 7-10 mm) above the ankle syndesmosis
                                 (between 2-5 cm), through which is passed a single No 5 Ethibond suture to form a loop;
                       - the suture is tied over the fibula, securing the fibula to the tibia;
                       - advantages: there is no need for hardware removal and nor is there risk of hardware failure;
                       - in the study by Miller RS, et al (1999), the suture technique showed similar strength characteristics to tricortical screw
                                 fixation techniques;
                       - references:
                               - Comparison of tricortical screw fixation versus a modified suture construct for fixation of ankle syndesmosis injury:
                               - Repair of the tibiofibular syndesmosis with a flexible implant.  
                               - Comparison of a Novel FiberWire-Button Construct versus Metallic Screw Fixation in a Syndesmotic Injury Model
                               - Randomized Trial Comparing Suture Button with Single Syndesmotic Screw for Syndesmosis Injury

Long-term Results After Ankle Syndesmosis Injuries.
Examination and Repair of the AITFL in Transmalleolar Fractures.
Outcome after fixation of ankle fractures with an injury to the syndesmosis: the effect of the syndesmosis screw.
Mechanical considerations for the syndesmosis screw. A cadaver study.
Distal tibial fracture post syndesmotic screw removal: an adverse complication
The management of acute distal tibio-fibular syndesmotic injuries: Results of a nationwide survey.
Operative treatment of syndesmotic disruptions without use of a syndesmotic screw: a prospective clinical study.