Detection of fibular rotational changes in cone beam CT: experimental study in a specimen model

Background In syndesmotic injuries, incorrect reduction leads to early arthrosis of the ankle joint. Being able to analyze the reduction result is therefore crucial for obtaining an anatomical reduction. Several studies that assess fibular rotation in the incisura have already been published. The aim of the study was to validate measurement methods that use cone beam computed tomography imaging to detect rotational malpositions of the fibula in a standardized specimen model. Methods An artificial Maisonneuve injury was created on 16 pairs of fresh-frozen lower legs. Using a stable instrument, rotational malpositions of 5, 10, and 15 degrees internal and external rotation were generated. For each malposition of the fibula, a cone beam computed tomography scan was performed. Subsequently, the malpositions were measured and statistically evaluated with t-tests using two measuring methods: angle (gamma) at 10 mm proximal to the tibial joint line and the angle (delta) at 6 mm distal to the talar joint line. Results Rotational malpositions of >= 10 degrees could be reliably displayed in the 3D images using the measuring method with angle delta. For angle gamma significant results could only be displayed for an external rotation malposition of 15 degrees. Conclusions Clinically relevant rotational malpositions of the fibula in comparison with an uninjured contralateral side can be reliably detected using intraoperative 3D imaging with a C-arm cone beam computed tomography. This may allow surgeons to achieve better reduction of fibular malpositions in the incisura tibiofibularis.