The effect of wearing a flexible wrist splint on carpal tunnel pressure during repetitive hand activity.

We investigated how repetitive hand activity normally affects carpal tunnel pressure and whether a flexible wrist splint can influence this effect. Nineteen healthy subjects were evaluated under four test conditions: at rest with and without a wrist splint (baseline) and while performing a repetitive task with and without a wrist splint. The task involved loading and unloading 1 lb. cans from a box at a rate of 20 cans per minute for period of 5 minutes. Carpal tunnel pressure and wrist angles were continuously monitored by means of a fluid-filled catheter inserted into the carpal canal and a two-channel electrogoniometer mounted on the dorsum of the hand and forearm. Without the splint, carpal tunnel pressure rose from a median baseline level of 8 +/- 6 mmHg to 18 +/- 13 mmHg during activity. With the splint, carpal tunnel pressure rose from a baseline of 13 +/- 5 mmHg to 21 +/- 12 mmHg during activity. Median carpal tunnel pressure during activity with the splint was no different from that without the splint. Our data indicate that the median nerve is subjected to increased pressure within the carpal tunnel during repetitive hand activity. Wearing a flexible wrist splint during activity limits the range of wrist motion but has no significant effect on carpal tunnel pressure.