LAUSR

OBJECTIVE To introduce a new method for intraoperative detection of rotational malreduction of the lateral malleolus using conventional fluoroscopy. MATERIAL AND METHODS From January 2014 to December 2017, 56 Weber type C unstable lateral malleolar fractures with syndesmosis injury were identified. The fibular fracture patterns were simple oblique or transverse in 20, comminuted in 25, and Maisonneuve injury with fibular neck fractures in 11 cases. 47 cases were operated with ORIF, and 9 cases of Maisonneuve fractures were operated with CRIF. The mortise view of the contralateral uninjured ankle was used for intraoperative comparison. Two indexes were applied for fluoroscopic detection of distal fibula malrotation, i.e. the contour profile change in lateral malleolar shape, and the intrinsic structure appearance of lateral malleolar fossa cortex. Postoperative talofibular joint congruency was measured on axial CT scan to confirm the reduction quality. RESULTS Using the two radiographic parameters for intraoperative fluoroscopic evaluation, we finally achieved satisfying reduction and fixation of the lateral malleolus in all 56 cases. A more spoon-shaped fibula profile and disappearance of the lateral fossa cortex shadow indicates an internal rotation, while a more pointed blade-shaped fibula profile and disappearance of lateral fossa cortex shadow indicates an external rotation. Postoperative CT scanning identified distal fibular no rotation in 44 cases (78.6%), mild rotation less than 5° in 12 cases (21.4%), with 7 cases internal rotation (mean 3.1°) and 5 cases external rotation (mean 2.8°). CONCLUSION Using conventional intraoperative fluoroscopy on mortise view, new radiographic parameters can provide reliable method to detect rotational malreduction of the lateral malleolus.