Plantar Flexion Influences Radiographic Measurements of the Ankle Mortise

Abstract

Plantar flexion of the ankle produces changes in radiographic measurements of the medial clear space. The potential for false-positive findings of deltoid disruption increases with increasing ankle plantar flexion.

Does Foot Position and Location of Measurement Influence Ankle Medial Clear Space?

“…5,9 The position of the ankle to measure MCS has also been studied. Saldua et al 10 found an average increase of 0.38 mm in MCS with ankle plantar flexion from 0° to 45°, using mortise radiographs. In our study, we found an average increase of 0.66 mm from neutral to FPF at MCSp and of 0.90 mm at MCSo, using AP radiographs, which may explain why the values encountered were so different.…”

Varus External Rotation Stress Test for Radiographic Detection of Deep Deltoid Ligament Disruption With and Without Syndesmotic Disruption

“…The ankle was maintained at neutral to slight dorsiflexion to diminish the possibility of a false-positive DDL instability due to plantarflexion. 19,22 The footplate was used as a visual guide to maintain a neutral to slightly dorsiflexed position. Three conditions were used: intact ligaments, DDL transected, and DDL + syndesmosis transected ( Figure 3).…”

Relationship of Self-Reported Ability to Weight-Bear Immediately After Injury as Predictor of Stability for Ankle Fractures

“…Patient positioning can be difficult as can ascertaining an appropriately rotated mortise radiograph, and patients may inadvertently plantarflex due to discomfort, which has been demonstrated to overestimate medial clear space widening. 23…”