Abstract
Introduction
The assessment of the accuracy of reduction of the ankle syndesmosis has traditionally been made using plain radiographic measurements. Recent studies have shown that computerized tomography (CT) scan is more sensitive than radiographs in detecting diastasis. The ethos has now therefore shifted towards CT scan assessment of the syndesmosis. There is however no validated method to scan the syndesmosis and measure it on the CT scans. This exposes the patient to significant radiation risk and also to anxiety from inappropriate interpretation from these scans.
The objectives of this research project are to investigate the current practice of CT scanning the syndesmosis at a University Hospital and to devise a new CT protocol to reduce radiation exposure to patients and to assist surgeons in interpreting the observations.
Methods
Research Ethics Committee approval was obtained. Current practice was evaluated. A new 5 cut CT protocol was devised. Starting at the level of the distal tibial plafond, 5 cuts were made proximally 0.5 cm apart. Accuracy of the syndesmosis reduction was assessed just above the distal tibial plafond. Both the injured and the normal sides were scanned 12 weeks post surgery. The normal side served as a control.
Results
Current practice revealed that patients had on an average 620 cuts CT scan with radiation exposure of 0.2 mSv. 25 patients were prospectively recruited for the new 5 cut CT protocol. The radiation exposure with the new protocol was only 0.002 mSv. Comparison with the normal side revealed that 5 (20%) of syndesmosis had residual diastasis. The only difficulty with the new protocol was getting both the ankle joint lines at the same level for the first CT cut.
Discussion and Conclusion
Our CT scan protocol has insignificant radiation risk, even lower than a single chest radiograph. Comparing the measurements between the fractured and the normal sides provides an accurate assessment of the reduction of the syndesmosis. Significance of the measurements on the CT scan will be correlated with functional scores.
