- 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 fracture would disrupt interosseous ligament, can explain the anatomic basis for infrequent diastasis in these ankle fractures;
- 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:
- contra-indications for syndesmotic fixation (w/ syndesmotic injury):
- w/ < 3 cm of sydesmotic disruption above plafond, there is little or no alteration was seen of ankle loading characteristics;
- anatomic reduction of fibula, esp if frx is w/in 4 cm of joint, tends to reduces talus in Mortise & restores syndesmotic stability;
- if
medial malleolus is frxed &
deltoid ligament is intact, ORIF of fibula & tibia should make syndesmosis fixation unnecessary;
- 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 hardware removal;
- suture fixation:
- involves the creation of two small drill holes through the 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: a biomechanical study..
-
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
Mechanical considerations for the syndesmosis screw. A cadaver study.
Operative treatment of syndesmotic disruptions without use of a syndesmotic screw: a prospective clinical study.
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.
Distal tibial fracture post syndesmotic screw removal: an adverse complication
The management of acute distal tibio-fibular syndesmotic injuries: Results of a nationwide survey.
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