Value of postoperative computed tomography for the diagnosis of lateral hinge fracture in medial opening-wedge supramalleolar osteotomy

Abstract

Introduction It remains unclear whether computed tomography (CT) is superior to plain radiography in detecting lateral hinge fractures after medial opening-wedge supramalleolar osteotomy (SMO) of the ankle joint. This study aimed to evaluate the disparity between postoperative plain radiography and CT in detecting lateral hinge fractures after medial opening-wedge SMO and to identify the predictive factors of lateral hinge fractures. Materials and methods This retrospective study included 39 patients who underwent medial opening-wedge SMO. The immediate postoperative plain radiography and CT scan images were retrieved, and the presence of lateral hinge fractures was independently determined. Depending on the fracture gap, the lateral hinge fractures were subclassified as stable (gap < 2 mm) or unstable (gap >= 2 mm) fractures. To investigate the predictive factors, the cases were divided based on diagnostic tools such as plain radiography and CT. Results The incidence of lateral hinge fractures was 48.7% (19/39) on plain radiographs and 61.5% (24/39) on CT scans. Five cases of lateral hinge fractures additionally detected on CT scans were stable fractures, and all had been classified as no fracture on plain radiographs. The unstable fractures that had been subclassified based on plain radiographs did not change on CT scans. None of the variables were associated with the presence of lateral hinge fractures on plain radiographs and CT scans. Conclusions Postoperative CT after medial opening-wedge SMO has no additional diagnostic value if the lateral hinge fracture has already been diagnosed on plain radiography. Therefore, postoperative CT is only recommended when lateral hinge fractures are not visible on plain radiographs.