Medial clear space volume on cone beam CT scan offers objective measurement of congruency in supination external rotation ankle fractures in a cadaver model

Background: We performed a volume analysis of gravity stress (GS) and simulated weight bearing (WB) CBCT scans of a cadaveric supination external rotation (SER) ankle fracture model. Methods: An AO supination external rotation 44B3.1 ankle fracture was simulated in 6 human cadavers, each serving as its own control. MCS volume (mm³) was measured on GS and WB CBCT scans. Paired t-tests were used to compare the MCS volume for control versus experimental conditions for GS and WB conditions, and means ± standard deviation are presented. Results: MCS on GS CBCT was greater for the experimental (1,540.15±374.8) versus control (984.5±226.5) groups (P=0.004), and MCS on WB CBCT was also greater for the experimental (1,225.57±274.1) versus control (1,059.40±266.6) groups (P=0.05). MCS on GS CBCT was greater for the experimental group compared to both WB CBCT controls (P=0.005) and WB CBCT experimental group (P=0.04). Additionally, MCS on WB CBCT was greater for the experimental group compared to GS CBCT controls (P=0.002), however there was no statistically significant difference in MCS on GS CBCT for controls versus WB CBCT for controls (P=0.08). Conclusions: MCS volume increased on WB CBCT scans using a cadaveric SER ankle fracture model.