Carpal canal pressure of the distracted wrist

Purpose This study was conducted to study the effect of distraction across the wrist joint on carpal canal pressure. Methods Ten cadaver specimens were mounted vertically in neutral forearm rotation by 2 half pins that transfixed the radius and ulna. The wrist joint was distracted by suspending weights from the middle finger. A balloon-tipped catheter, percutaneously introduced into the carpal canal and connected to a transducer, was used to measure carpal canal pressure. The carpal canal pressure was measured at 0 to 4.54 kg of distraction in 0.45-kg increments and at 6.81 kg and 9.08 kg of distraction. Three wrist positions were tested: neutral, 30° of flexion, and 30° of extension. Results Highly linear direct relationships between wrist distraction force and carpal canal pressure over baseline were observed in all positions of the wrist. Statistically significant increases in carpal canal pressure over baseline were observed at a wrist distraction force of 2.27 kg or more with the wrist in neutral position, at 1.82 kg or more with the wrist in 30° of extension, and at 4.09 kg or more with the wrist in 30° of flexion. At each level of wrist distraction force of 3.63 kg or less the carpal canal pressure of the extended wrist was significantly higher than that of the wrist in neutral position. At each level of wrist distraction force 4.54 kg or less the carpal canal pressure of the extended wrist was significantly higher than that of the flexed wrist. No statistically significant differences were observed at any level of wrist distraction force between carpal canal pressures in the neutral and flexed positions of the wrist. Conclusions Distraction across the wrist joint causes a statistically significant highly linear increase in carpal canal pressure. The position of the distracted wrist also has a considerable effect on carpal canal pressure, with the extended position associated with the largest increases in carpal canal pressure and the flexed position with the smallest increases in carpal canal pressure.