Fig. 3

P-US probe positioning and medial clear space distance measurements

3 A) The P-US probe was placed perpendicular to the anteromedial aspect of the medial gutter at the defined landmark for assessing the anterior-perpendicular-MCS and anterior-oblique-MCS. The anterior-perpendicular-MCS distance was measured in mm as represented by the perpendicular distance, drawn starting from the medial border of the talus’s hyperechoic bone contour to the lateral border of the medial malleolus’s hyperechoic bone contour (3 B, 3 C). The anterior-oblique-MCS distance was measured in mm as represented by the oblique distance drawn starting from the lateral border of the medial malleolus’s hyperechoic bone contours to the anteromedial edge of the talus’s hyperechoic bone contours (3 D, 3 E)

3 F) The P-US probe was placed perpendicular to the inferomedial aspect of the medial gutter at the defined landmark for assessing the inferior-MCS. The inferior-MCS distances were measured in mm as represented by the perpendicular distances, drawn starting from the medial border of the talus’s hyperechoic bone contours at the level of the medial malleolar tip to the lateral border of the medial malleolus’s hyperechoic bone contours Fig.  3G, 3H)

Thick lines represent MCS distances

(Abbreviations: MCS, medial clear space; M, medial malleolus; T, Talus; P-US, portable ultrasound)