Analysis of Medial Clear Space Widening in Weber B Ankle Fractures

Rotational ankle injuries are a commonly encountered injury. Classification of these injuries is most commonly by the Danis-Weber (or Weber) classification and the Lauge-Hansen classification.

Within this classification system exists the isolated Weber B or Lauge-Hansen Supination External Rotation 2/4 (SER 2/4) injury which radiographically involves an isolated spiral fracture of the lateral malleolus at the level of the tibiofibular syndesmosis.

The difference between SER2 (isolated) Weber B injuries and SER4 injuries is disruption of the medial ankle mortise structures, either the medial malleolus (4a) or deltoid ligaments (4b) which then can permit increased talar subluxation with potential to result in tibitotalar joint incongruity.

Standard practice is to proceed with operative fixation of rotationally unstable Weber B or SER4b injuries.

To determine the competence of medial ligamentous structures in isolated fractures of the fibula at the level of the syndesmosis when there is minimal widening of the mortise on non weight bearing films there are three plain x-ray views currently widely used and considered standard of care:

• manual external rotation stress;
• gravity assisted stress;
• and weight-bearing stress radiographs.

Increased widening on one of these views is used to decide whether to treat the fracture with or without surgery.

Globally there is wide variability as to which stress-view radiograph or combination of these are used. To our knowledge, no study to date has compared all three stress-view radiographs concurrently to determine if the three different methods predict equal amounts of tibiotalar joint instability.

The need to understand how these three views compare is crucial, as tibiotalar instability is primary indication for surgical stabilization.

The null hypothesis therefore is the investigators will find no difference in the tibiotalar joint instability between the three stress views.

Inclusion criteria

• Patients with a Weber B ankle fracture who are skeletally mature (no open physes) and older than 18 years of age.

Exclusion criteria

• Medial and/or posterior Malleolar fracture
• Any other lower extremity trauma that limits weight bearing
• Concomitant arthridities/rheumatologic disease (patients with osteoarthritis may be included)
• Prior fracture
• Prior surgery of foot, talus or ankle
• Open fracture
• Initial NWB xrays with a medial clear space (MCS) > 7 mm or medial clear space> superior clear space (SCS) by 2mm, signifying an unstable fracture prior to stress
• Protected populations