Table 3.

Cut-off values of area and volume of the distal syndesmosis and their corresponding sensitivities and specificities for the detection of syndesmotic instability. Cut-off values are calculated based on 2D area and 3D volume measurements performed on weightbearing CT scan of 72 uninjured ankles (24 uninjured ankles in the patients and 48 in the control group).

Measurements	Cut-off Value	Sensitivity (%)	95% CI	Specificity (%)	95% CI	PPV (%)	NPV (%)	Accuracy (%)
Area at 1cm above TP	1.4 cm2	70	[38.5-81.5]	81.6	[76.8-92.1]	82.6	69.2	75.1
Area at 3cm above TP	2.5 cm2	60	[33.2-76.8]	79.6	[69.3-93.2]	78.6	65.4	70
Area at 5cm above TP	3.2 cm2	62.5	[43.1-81.9]	80.3	[68.4-96.2]	78.9	69.9	72.5
Area at 10cm above TP	4.6 cm2	50	[35.9-64.1]	71	[57.9-83.7]	63.2	58.6	60.4
Volume at 1cm above TP	1.5 cm3	62.5	[43.1-81.9]	80	[67.6-92.4]	78.9	64	70.4
Volume at 3cm above TP	5.3 cm3	76.2	[63.3-89.1]	81.3	[77.2-92.8]	72.7	87.2	82
Volume at 5cm above TP	11.6 cm3	95.8	[87.8-100]	83.3	[68.4-98.2]	85.7	95.2	90
Volume at 10cm above TP	29.2 cm3	83.3	[72.8-93.9]	79.2	[67.7-90.1]	80	82.6	81.3

Abbreviations: TP, tibial plafond; PPV, positive predictive value; NPV, negative predictive value; SD, standard deviation; %, percentage; CI, confidence interval.