Quantitative MRI analysis of anatomic dimensions of the carpal tunnel in women

114 wrists from two groups of asymptomatic women of 25-45 years of age (group I, no = 30) and over 45 years (group II, no = 27) were examined: a) to quantify the anatomic features of the carpal tunnel, and b) to search for age-related changes in the anatomy of the tunnel. Bilateral MRI axial wrist images were obtained by means of turbo spin echo (TSE) and fast field echo (FFE) sequences. We measured the length, the cross-sectional areas, the volume of the carpal tunnels-from inlet to outlet- and the volume of the wrists, bilaterally. A carpal tunnel volume/wrist volume (CTV/WV) ratio was obtained in both groups. We also searched for the location of the narrowest point of the canal. The mean (SD) length of the tunnel, from inlet to outlet, was 36.3 mm (SD = 3.4), in both groups. The tunnel had a cone shape, with the inlet constantly larger than the outlet in all subjects. The mean (SD) cross-sectional area of the tunnel inlet was found to be larger in group II, compared to group I (p = 0.029). The calculated mean (SD) volume of the tunnel also appeared significantly larger in the older group (p = 0.023). The narrowest point of the canal was identified at its distal third, at 8 mm from the outlet, in both groups. We conclude that: a) quantitative MRI is a valuable method for assessing the anatomic characteristics of the carpal tunnel, and b) the anatomy of the tunnel is affected by age.