Ultrasonography in tarsal tunnel syndrome

Objective. The purpose of this study was to clarify the diagnostic value of ultrasonography in tarsal tunnel syndrome. Methods. Seventeen patients (17 feet) with tarsal tunnel syndrome were treated between 1988 and 2003. Preoperative ultrasonography was performed, and the cause of the syndrome was confirmed intraoperatively in all cases. Long and short axes of the tarsal tunnel were scanned to ascertain the presence of any space-occupying lesion. Results. The causes of tarsal tunnel syndrome, as confirmed by surgery, were ganglia (n = 10), talocalcaneal coalition (n = 1), talocalcaneal coalition associated with ganglia (n = 3), and varicose veins (n = 3). Among the cases involving ganglia, hypoechoic or anechoic regions were observed. The mean sizes +/- SD of these regions were 19.4 +/- 8.8 mm in the long axis, 15.2 +/- 6.3 mm in the short axis, and 10.4 +/- 3.8 mm in depth. Of these, 3 ganglia were not clearly palpable before surgery and were small: 10 x 10 x 7, 13 x 11 x 9, and 9 x 8 x 7 mm. Among the cases involving talocalcaneal coalition, ultrasonography indicated a beak-shaped bony process on the short axis images. Although these 3 cases were associated with ganglia, this could not be determined by preoperative palpation. Conclusions. As a diagnostic imaging technique for tarsal tunnel syndrome, ultrasonography is extremely useful for identifying space-occupying lesions. Ultrasonography should be performed routinely in patients with suspected tarsal tunnel syndrome.