Weight bearing cone beam CT scan versus gravity stress radiography for analysis of supination external rotation injuries of the ankle

Abstract

For AO 44-B2 ankle fractures of uncertain stability, the current diagnostic standard is to obtain a gravity stress radiograph, but some have advocated for the use of weight-bearing radiographs. The primary aim was to compare measures of medial clear space (MCS) on weight-bearing cone beam computed tomography (CBCT) scans versus gravity stress radiographs for determining the state of stability of ankle fractures classified as AO SER 44-B2 or Weber B. The secondary aim was to evaluate the details offered by CBCT scans with respect to other findings that may be relevant to patient care. Nine patients were enrolled in this cross-sectional study between April 2016 and February 2017 if they had an AO SER 44-B2 fracture of uncertain stability, had a gravity stress radiograph, and were able to undergo CT scan within seven days.The width of the MCS was measured at the level of the talar dome on all radiographs and at the mid coronal slice on CT. Wilcoxon signed-ranks tests were used to compare MCS between initial radiographs, gravity stress radiographs and weight-bearing CBCT scans. MCS on weight-bearing CBCT scan (1.41±0.41 mm) was significantly less than standard radiographs (3.28±1.63 mm, P=0.004) and gravity stress radiographs (5.82±1.93 mm, P=0.02). There was no statistically significant difference in MCS measured on standard radiographs versus gravity stress radiographs (P=0.11). Detailed review of the multiplanar CT images revealed less than perfect anatomical reduction of the fractures, with residual fibular shortening, posterior displacement, and fracture fragments in the incisura as typical findings. Similar to weight-bearing radiographs, weight-bearing CBCT scan can predict stability of AO 44-B2 ankle fractures by showing restoration of the MCS, and might be used to indicate patients for non-operative treatment. None of the fractures imaged in this study were perfectly reduced however, and further clinical research is necessary to determine if any of the detailed weight-bearing CBCT findings are related to patient outcomes.

Weight-Bearing Cone-Beam CT Scan Assessment of Stability of Supination External Rotation Ankle Fractures in a Cadaver Model

“…We have found that, like plain radiography, weight-bearing CT scans can indicate stability in many SER fractures of uncertain status and could be used to select patients for nonoperative treatment based on medial clear space measurement. 18 On the other hand, we also noticed by examining all 3 planes of CT images that there was rarely perfect reduction, with residual fibular shortening, fibular rotation, fracture comminution, and asymmetry of the distal tibiofibular joint present. We are not certain of the clinical implications of these findings, and although others have shown good clinical outcome when only medial clear space is used for decision making, the studies have been of relatively short follow-up.…”

“…20,26 Previous studies, however, have demonstrated that gravity stress radiographic measurements may overestimate the number of patients in need of operative fixation. 11,13,14,18,27,31 These authors report that weight-bearing radiographs are more predictive of stability, and patients with an anatomic mortise relationship can be successfully managed with immediate protected weight bearing and functional rehabilitation, without having to undergo an operative procedure.…”

Comparison of cartilage and bone morphological models of the ankle joint derived from different medical imaging technologies

“…In addition, the recent cone-beam CT (CBCT) technology, originally for the field of dentomaxillofacial radiology (15,(22)(23)(24), has proved to be also suitable to musculoskeletal radiology for upper and lower limb joints, and features reduced radiation dose, high surface and model accuracy (25,26), but mainly weight-bearing condition for the patient during scanning. These devices finally allow to study bone and joint architecture of the extremities under physiological load (14,(27)(28)(29)(30). Because of the limited field of view (FOV), the CBCT is thus suitable for joints of small dimension (27).…”

The Value of Additional Gravity Stress Radiographs for Decision Making in the Treatment of Isolated Type B Distal Fibular Fractures

“…In 2017, Marzo et al 16 were the first to investigate the weightbearing CT scan, in comparison with the GS radiograph. Mean MCS on weightbearing CT scan (1.41 mm) was significantly less than that on standard radiographs (3.28 mm) and GS radiographs (5.82 mm).…”