The precision of ultrasound imaging and its relevance for carpal tunnel syndrome.

The carpal tunnel syndrome (CTS) is the most common peripheral entrapment neuropathy in human. The diagnosis is based on symptoms and on physical examination and is supported by nerve conduction tests. The aim of this study was to evaluate the precision and the valence of ultrasound (US) for CTS. An anatomic study was performed on 40 wrists of 20 unfixed human cadavers. The carpal tunnel and its important structures and contents were imaged and measured by ultrasound (7.5-MHz high resolution probe). The dorsopalmar diameter (DPD), the radioulnar diameter (RUD), the perimeter (P) and the cross-sectional area (A) were determined for the carpal canal and for the median nerve. These US images and measurements were directly compared with anatomic cross-sections gained from the same wrists at the same level. Our results showed that ultrasound is a very precise method to display the anatomy of the carpal tunnel and of the median nerve and thus the conditions of the median nerve. Significant differences could not be detected for each of these parameters either for the carpal tunnel or the median nerve. (Ultrasound: cross-sectional area of carpal tunnel: 162.4 +/- 29.3 mm2 and of the median nerve: 9.2 +/- 2.4 mm2; anatomy: cross-sectional area of carpal tunnel: 168.4 +/- 31.2 mm2 and of median nerve: 9.4 +/- 2.2 mm2).