Dynamics of intracarpal tunnel pressure in patients with carpal tunnel syndrome.

PURPOSE: To measure pressure within the carpal tunnel (intracarpal tunnel pressures) in patients with carpal tunnel syndrome and determine the effect of quantified active hand use on both the magnitude and location of peak pressures, before and after division of the transverse carpal ligament.

METHODS

We measured intracarpal tunnel pressures intraoperatively in 12 patients with carpal tunnel syndrome at 5 standardized locations based on the distance between each patient's proximal pisiform and hook of hamate (HH) before endoscopic division of the ligament, using a semiconductor gauge pressure sensor inserted from proximal to distal into the tunnel under fluoroscopic control. At each location, pressure was recorded with fingers extended, fingers flexed, and 50% maximum grip using a grip dynamometer. Additional hand use activities, including maximum key and pulp pinch using a pinch dynamometer, 25% maximum grip, and maximum grip, were performed by a subset of these patients. After ligament division, we measured pressures during the same hand activities at a single location, HH. We analyzed the effect of hand activity, measurement location, and ligament division using repeated measures analysis of variance.

RESULTS

Compared with fingers extended (mean pressure, 56 mm Hg), all pinch and grip activities caused significant increases in pressure at HH, with a mean peak pressure of 1151 mm Hg during maximum grip. After endoscopic release, pressures decreased significantly at HH for all hand activities.

CONCLUSIONS

In patients with carpal tunnel syndrome, intracarpal tunnel pressures during active hand use are substantially greater than previously reported. Peak pressures occur at the HH, where the tunnel is most constricted and the median nerve is most compressed in carpal tunnel syndrome.

TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.