The aim of this study was to evaluate the correlation between the preoperative radiological measures of the carpal tunnel and the ease of access of the instruments into the carpal tunnel during an endoscopic carpal tunnel release (ECTR) and to estimate changes in the radiological measures after ECTR.

Carpal tunnel views were possible in 45 patients, 78 wrists taken before the ECTR and the distances between scaphoid and pisiform (S-P) and between trapezium and hamate (T-H) were measured. The correlation between the measured distances and the ease of access of instrument was analyzed. In addition, the radiographic carpal tunnel views were taken three months after surgery and the distance changes after ECTR were measured.

In “easy” rated access, the average S-P and T-H distances were 34.5 mm and 24.8 mm in females and 37.0 mm and 26.1 mm in males, respectively. In the "difficult" rated access, the average distances were 29.5 mm and 20.0 mm in females and 32.4 mm and 22.7 mm in males, respectively. Therefore, as the distances became shorter, the insertion of the endoscopic instrument became more difficult (p<0.001). However, after ECTR, the average distances were significantly increased in all cases by 2.5 mm (7.6%) and 2.4 mm (9.6%) in females and 2.8 mm (7.9%) and 2.8 mm (11.2%) in males, respectively (p<0.001).

The ease of access of an endoscopic device into the carpal tunnel on ECTR had a significant correlation with the radiological measures of the S-P and T-H distances on the preoperative carpal tunnel view. In view of such radiological measures, it is believed that the carpal tunnel is widened after ECTR.