A simplified, validated method for measuring fibular reduction on CT scan

C.P. Prior, D. Weller, E.V. Wood

Introduction: Fibular malreduction is an important cause of pain after ankle fracture fixation. Plain radiographs have been shown to be unreliable at measuring mal reduction when compared to CT scans. Davidovitch developed a validated method of measuring malrotation, diastasis and AP translation. His method relies on finding the axis of the fibula. Elgafy demonstrated that the fibula morphology varies greatly, and in many cases it can be difficult finding the fibular axis.

Methods: We developed a new method of measuring the ankle syndesmosis on CT scans. We used CT scans in 16 normal subjects after a power calculation. Two assessors independently measured the ankle syndesmosis using the Davidovitch method, and our new protocol.

Results: We demonstrated that after statistical analysis (Pearson Product Moment Correlation) our method showed improved inter-observer reliability (0.99 and 0.95 vs 0.77 and 0.58 respectively) for diastasis and AP translation, and improved intra-observer reliability (0.99 and 0.99 vs 0.96 and 0.91 respectively). We found that fibular rotation was difficult to measure accurately.

Conclusion: We believe that out method is a simple, accurate and reproducible system for measuring the ankle syndesmosis. We believe that this method could be used to assess fibular reduction after obtaining CT images of the uninjured side for comparison.