Consistency and Reliability of Ankle Stress Radiography in Patients With Chronic Lateral Ankle Instability

BACKGROUND: Ankle stress radiographs are important tools for evaluating chronic lateral ankle instability. The consistency of a patient’s ankle condition as it affects the reliability of ankle stress radiographs has never been evaluated. PURPOSE: To investigate the consistency and reliability of ankle stress radiographs in patients with chronic lateral ankle instability without an ankle injury during the study period. STUDY DESIGN: Cohort study (diagnosis); Level of evidence, 3. METHODS: Included were patients with chronic lateral ankle instability who underwent 2 repeated ankle stress radiographs between January 2014 and July 2019; those with an ankle injury during the study period were excluded. The tibiotalar tilt angle on varus stress radiographs and anterior translation of the talus on anterior drawer stress radiographs were measured at initial presentation and final follow-up examination. Interobserver reliability and consistency of ankle stress radiographs were analyzed using the intraclass correlation coefficient (ICC). RESULTS: A total of 45 patients (mean ± standard deviation age, 36.4 ± 13.4 years; 18 men and 27 women; follow-up duration, 9.1 ± 3.2 months) were included. The mean ± standard deviation tibiotalar tilt angle and anterior talar translation at initial presentation were 10.8° ± 5.2° and 6.9 ± 2.7 mm, respectively. The interobserver reliabilities of the tibiotalar tilt angle and anterior talar translation were excellent (ICC = 0.926 [95% CI, 0.874-0.959] and 0.911 [95% CI, 0.766-0.961], respectively). The consistency between the initial and final radiographs was good for tibiotalar tilt angle (ICC = 0.763 [95% CI, 0.607-0.862]) and poor for anterior talar translation (ICC = 0.456 [95% CI, 0.187-0.660]). CONCLUSION: Although the interobserver reliability of the radiographic measurements was excellent, the consistency of the ankle stress radiographs was not as acceptable. Surgeons need to be cautious when deciding whether to operate on a patient with chronic lateral ankle instability based on a single ankle stress radiograph.