Novel Radiographic Measurement Method for an Anterior Drawer Stress View of Plain Radiographs in Patients with Chronic Lateral Ankle Instability: Fibular Tip to Talar Neck Measurements

Purpose: Stress radiographs have long been used to evaluate chronic lateral ankle instability.Several measurement methods exist, but their diagnostic value remains controversial.This paper introduces a new measurement method for stress radiographs, the fibular tip to talar neck (FTN) method, and compares it with established methods to assess its diagnostic accuracy and reliability.Materials and Methods: Forty-one patients who underwent a modified Broström procedure for chronic lateral ankle instability were included.Lateral standing and anterior drawer radiographs were analyzed using two conventional methods (methods I and II) and the novel FTN method.The contralateral unaffected side served as an internal control.The diagnostic accuracy was evaluated using receiver operating characteristic curve analysis.The intra-observer and inter-observer reliability were assessed using intraclass correlation coefficients (ICCs).Results: Using the FTN method, the mean gap on the affected side (14.39±4.79mm) was significantly greater than on the contralateral side (10.24±4.19mm, p<0.001).The side-to-side difference (SSD) was significantly higher in the FTN method (4.14±2.94mm) compared to methods I (0.89±1.94 mm) and II (0.91±1.78 mm, p<0.001).The FTN method showed a balanced diagnostic performance with an area under the curve of 0.743 and an optimal cut-off of 13.5 mm.The intra-observer and inter-observer reliability were good for all methods.The intra-observer and inter-observer ICCs for the FTN method were 0.858 and 0.783, respectively. Conclusion:The FTN method provides a reliable and reproducible measure of chronic lateral ankle instability.The method facilitates a more intuitive diagnosis compared to conventional techniques by providing a larger numerical differentiation (SSD) and a statistically balanced threshold.