Radiographic parameters in gravity stress view of the ankle: Normative data

In rotational ankle injury with isolated fibular fracture, deltoid integrity is important for determining stability of ankle. Medial clear space and superior clear space in gravity stress view are parameters widely used to predict deltoid ligament tear. The purpose of this study is to report radiographic parameters in gravity stress view in normal population.

120 persons were enrolled. Non weight-bearing ankle mortise and gravity stress view were obtained. Radiographic measurements were made by 2 investigators, including medial clear space (MCS), superior clear space (SCS), tibiofibular overlaps, tibiofibular clear space and talocrural angle. Statistical analysis included mean, mean difference, SD, 95%CI, paired T-test were calculated and subgroup analysis by foot length. Intraclass correlation coefficients were used to determine intra/interobserver reliability of measurement.

Mean MCS in gravity stress view was 3.19mm (95%CI 3.1-3.31). This compared to mean MCS of 3.01mm (95%CI 2.9-3.12) in mortise view which was statistically significant (P=0.02). Mean difference was 0.18mm (95%CI 0.07-0.3). SCS in gravity stress view was 3.29mm (95%CI 3.19-3.39) and when compared to MCS in gravity stress view, no statistical significance was found (P=0.158). Mean difference was 0.1mm (95%CI 0.03-0.21). In subgroup analysis by foot length, no significant difference was found in any parameters.

This study provides normative radiographic data for a gravity stress radiograph and supports that if measurable MCS >4mm on gravity stress view, it should be aware of an unstable ankle in supination-external rotation injury.