Stress radiography is known as an important diagnostic tool for confirming mechanical instability in patients with chronic ankle instability. However, there are no reports on how muscle guarding caused by the stress applied on the ankle during stress radiography affects test outcomes. Thus, this study aimed to analyze the effects of muscle guarding caused by stress radiography on outcomes by performing stress radiography before and after anesthesia. This is a prospective study involving 32 patients who were diagnosed with chronic ankle instability through patient history, physical examination, and magnetic resonance imaging studies. Varus and anterior drawer stress radiographs were taken before and after anesthesia in the operating room, and the findings were compared. On the post-anesthesia stress radiographs of the affected ankle, talar tilt and talar anterior translation were significantly increased by 2.55° ± 2.64° and 1.54 ± 2.03 mm, respectively (mean ± standard deviation; p < .05). These parameters were also significantly increased by 2.08° ± 2.62° and 1.27 ± 1.37 mm, p < .05, on the post-anesthesia radiographs of the unaffected ankle. Before anesthesia, 26 of 32 patients had positive stress radiographs, but 31 patients had positive results after anesthesia. Talar tilt and talar anterior translation significantly increased after anesthesia. Therefore, in CAI patients, efforts to reduce muscle guarding should be made before stress radiographs are taken. Moreover, when interpreting results, it should be noted that muscle guarding might have reduced the measurements of stress radiographs, leading to diagnostic false negatives.
Keywords: anesthesia; chronic ankle instability; muscle guarding; pain; stress radiographs.
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