Fluoroscopic Corner Congruency and Tibiotalar Symmetry Confirm Syndesmotic Reduction.

OBJECTIVE

The objective of this study is to assess the accuracy of two intraoperative radiographic markers, corner congruency (CC), and tibiotalar symmetry (TTS), in determining anatomic reduction of the syndesmosis.

METHODS

Eight cadaveric specimens were used. Each specimen underwent baseline imaging with C-arm fluoroscopy to confirm native presence of the CC and TTS radiographic markers and with axial CT to assess the native syndesmosis reduction. Unstable syndesmotic injuries were simulated through complete sectioning of the syndesmosis; malreductions were then performed, confirmed on CT, and CC and TTS markers were recorded. Open syndesmotic reductions were then performed and confirmed with CT, and the presence or absence of anatomically aligned CC and TTS radiographic markers were again recorded. All measurements were done independently by three reviewers.

RESULTS

CT measurements demonstrated intercorrelation coefficient values of >0.8, indicating excellent interobserver reliability. Anatomically aligned CC and TTS radiographic markers were present in all specimens at baseline. Fluoroscopic images obtained after malreductions demonstrated the presence of an anatomically aligned CC radiographic marker in 3/8 specimens, presence of TTS marker in 2/8 specimens, and anatomic malalignment of both markers in 3/8 specimens. None of the malreduced specimens demonstrated the concomitant presence of intact CC and TTS radiographic markers. After open reduction of the syndesmosis, all specimens demonstrated restoration of both the CC and TTS radiographic markers. Independently, CC as a marker of syndesmotic reduction was found to have a sensitivity of 62.5% and a specificity of 100%, whereas TTS as an independent marker of syndesmotic reduction was found to have a sensitivity of 75% and a specificity of 100%. In combination, the presence of both CC and TTS radiographic markers were found to have 100% sensitivity and specificity.

CONCLUSION

In combination, intact CC and TTS radiographic markers are reliable predictors of anatomic reduction of the syndesmosis.