- key to stability of ankle mortise is posterior syndesmotic ligament complex, ligament or posterior tibial tubercle or malleolus;
- presence of a posterior lesion always indicates degree of instability, whether or not the medial structures are disrupted;
- no matter what mechanism, instability must be assumed when injury to both sides of joint is accompanied by posterior syndesmotic ligament injury;
- spiral frx at or above joint indicates low energy rotation injuries, whereas short oblique or comminuted fractures at or above syndesmosis are usually caused by high energy abduction injuries and are more likely to be unstable;
- Stable Injury
- if ankle is stable, very little displacement will occur at lateral complex with stress abduction and eversion;
- if little or no displacement is present in the fibula, and there is no evidence of a posterior or medial injury, nonoperative treatment is indicated;
- note that this stable type of injury may occur with a fibular fracture at any level, be it at or above the syndesmosis;
- most common type II injury, SER variety w/o medial disruption, may be associated w/ fibular fracture at or above mortise;
- therefore, proximal position of the fibular fracture is not presumptive evidence of mortise instability;
- Unstable Injury: (see radiographic evaluation of ankle fractures)
- any clinical or radiologic injury to the medial joint complex;
- x-ray signs of instability include:
- abnormal valgus talar tilt;
- increased mortise width 2nd to w/ shortening or & displacement of fibula;
- subluxation of talus;
- frx of posterior or medial malleolus or their ligamentous equivalents;
- Indications for Treatment:
- if in presence of medial tenderness, > 5 mm of space is seen either initially or on a stress radiograph, presumptive dx of substantial injury of the deltoid ligament can be made;
- treat as bimalleolar frxs, w/ ORIF of lateral malleolus;
- routine exploration of medial side of the ankle is not necessary unless there is evidence that portion of the deltoid ligament has entered the joint and is blocking reduction of the talus
Experimentally produced ankle fractures in autopsy specimens.
The key role of the lateral malleolus in displaced fractures of the ankle.
Examination of the pathologic anatomy of ankle fractures.
Ankle fractures. A clinical and roentgenographic stereophotogrammetric study.
Stress Examination of Supination External Rotation-Type Fibular Fractures.
Ankle Stress Test for Predicting the Need for Surgical Fixation of Isolated Fibular Fractures.
The use of the gravity or manual-stress radiographs in the assessment of supination-external rotation fractures of the ankle.
Comparison of manual and gravity stress radiographs for the evaluation of supination-external rotation fibular fractures.