This article is more than 5 years old. Information may no longer be current.
Time Dependent Relaxation of Soft-Tissue Elements About the Wrist Following Wrist External Fixator Placement
Click Here to Manage Email Alerts
ABSTRACT
This study examined the change in soft-tissue tension over time following placement of a wrist external fixator, applied in tension.
Twelve fresh-frozen, matched cadaveric forearms were obtained, amputated above the elbow. A 3/16-inch pin was placed in the base of the second metacarpal and a second placed in the radial diaphysis. The forearms were placed in a Model 1101 Instron mechanical testing device (Instron Corp, Canton, Mass) with a 100-lb load cell. Twenty pounds of force was applied in tension using a cruise head of 2 inch/minute and a sampling rate of 5 pts/sec. The change in specimen tension was monitored over 24 hours by measuring the amount of force (tension) necessary to maintain the two inserted pins at a predetermined, fixed difference. This procedure was performed for six unaltered specimens labeled “controls” then repeated for the remaining six specimens labeled the “fracture group.” This group received a dorsally based, 5-mm wedge osteotomy at the metaphysis, simulating a comminuted, extra-articular distal radius fracture. All data were analyzed using Student’s t-test.
The average loss in tension by the control group and study group (fracture group) during the 24-hour period was 55% and 59%, respectively. This was not statistically significant. In 6 of 12 specimens, 50% of ultimate tension loss occurred within 180 minutes of application. The 50% of ultimate tension loss occurred at a faster rate in the fracture group than in the control group, but was not statistically significant.
Relaxation of wrist soft tissues occurs soon after being placed in tension by an external fixation device. Additionally, a tendency exists in the cadaver model for wrist soft-tissue relaxation to occur more rapidly once the dorsal radius cortex and periosteum have been disrupted. The results of this study question the reliability of ligamentotaxis as the sole means of maintaining reduction of shortened distal radius fractures.