June 24, 2009

Ankle Mortise Radiographic View

Figure 1: "Inadequate mortise view of the right ankle" in a patient with lateral malleolar fracture and torn deltoid ligament. Note that the radiograph was taken without adequate internal rotation of the ankle joint. The entire tibiotalar joint space is not clearly shown, particularly the lateral clear space. On this image, the medial clear space (arrowheads) appears normal.

Figure 2: "Adequate" mortise view of the same patient shows disruption of the deltoid ligament, which is shown as widening of the medial clear space (arrowheads).

Ankle Mortise View
  • Anteroposterior view with ankle internally rotated 15 to 20 degrees
  • Considered adequate if - tibiotalar joint well demonstrated entirely and medial/lateral clear spaces are open
  • Used to assess - tibiotalar articular surface, integrity of ankle mortise, and medial/lateral clear spaces
Normal
  • Entire tibiotalar joint space is uniform in width
  • Normal overlap between distal tibia and fibula about 1 mm, or a little wider than tibiotalar joint space
Our case emphasizes the importance of determining the adequacy of radiographic techniques before interpreting radiographs as normal. In our case, findings are consistent with a supination-external rotation (SER) type of ankle fracture.

Reference:
Schwartz DT, Reisdorff EJ. Emergency Radiology. McGraw-Hill Professional, 1999.

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