# Ins and Outs of the Ankle Syndesmosis from a 2D to 3D CT Perspective
## 3 Results
### Conventional 2D Measurements
#### 3.3.1 2D Measurements Quantifying Tibiofibular Translation Mediolateral Translation (Diastasis)  
* Anterior, middle, posterior, maximum, and minimum tibiofibular width First described by [PERSON] et al. [25], the anterior tibiofibular width (ATFW) and posterior tibiofibular width (PTTFW) are the most commonly used measurements of the distal tibiofibular joint in the literature [5; 6; 13; 18; 20; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32]. They serve as indicators of diastasis between the tibia and fibula [29]. [PERSON] et al. introduced the middle tibiofibular width (MTFW) as an additional measurement for diastasis [28]. More recently, [PERSON] et al. and [PERSON] et al. introduced the maximum tibiofibular width (MxTFW) and minimum tibiofibular width (MnTFW), respectively [22; 32]. These measurements are generally performed at the level of 1 cm proximal to the tibial plafond on axial images, as depicted in Figure 2A,B and  
Figure 4: Fibular translation measurements on an axial CT image of an uninjured syndesmosis. (**A**) Anteriorposterior translation ratio by [PERSON] [28] of anterior distance (a) and posterior distance (b) (blue lines), calculated based from a perpendicular line, drawn from the middle of a line connecting the most anterior and posterior points of the incisura (white solid lines). (**B**) Medial (c) and anterior (d) Phisitkul measurement (blue lines), calculated from a line connecting the most anterior and posterior points of the incisura, and a perpendicular line perpendicular to the previous line at the level of the anterior tubercle (white dashed lines). Figure 3: Fibular rotation measurements on an axial CT image of an uninjured syndesmosis and ankle. (**A**) Fibular rotation angle (\(\alpha\)) by [PERSON], The angle between the fibular axis and the tangential line to the anterior and posterior tibial tubercles (white lines) [36]. (**B**) Tang ratio of anterior (a) and posterior measurement (b), represented as the ratio of distances from the tibial centroid (white dashed lines) to the most anterior fibular point and the most posterior fibular point, respectively (blue solid lines). (**C**) Bimleolar angle (\(\beta\)), calculated between the tangential line to the medial cortex of the lateral malleolus and the tangential line to the lateral cortex of the medial malleolus (solid white lines). described in Table 1 This level is consistently selected due to the prominent tibial tubercles and well-defined fibular incisura at this extent [6, 13, 22, 24, 25, 27, 28]. Most studies exhibit a wide standard deviation (SD), resulting in a broad normative range [28]. Furthermore, the reference values do not account for age and gender. [PERSON] et al. reported that the posterior width is significantly smaller in women (\(p<0.001\)), and both ATFW and PTFW significantly decrease with age (\(p<0.001\)) [6]. On the other hand, some studies showed no significant difference in AFTW and PFTW by age and gender [29, 31]. However, there is no significant difference compared to the contralateral ankle, enabling bilateral comparison in the evaluation of syndesmotic injury [6, 31]. No significant differences were observed in the ATFW, PTFW, and MTFW under both normal and weight-bearing conditions. [29, 20]. Additionally, the interobserver reliability is excellent for the MnTFW and MxTFW and good for the ATFW, PTFW, and MTFW, indicating the reliability of these parameters. A recent study compared the ATFW and MTFW of the injured ankle with the contralateral uninjured ankle in 68 patients under non-weight-bearing conditions [18]. The mean distances were 0.3 greater in injured ankles compared to uninjured for both measurements. Ideal cut-off values for instability assessing the difference between the injured and uninjured ankle were set at 0.7 and 1.7 for ATFW and MTFW, respectively. These values demonstrate low sensitivity (25%) but high specificity (97%) for ATFW. For MTFW, the value is primarily useful for ruling out syndesmotic injuries, with low sensitivity (0%) but high specificity (100%) [18].