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The 2004 Annual Meeting (January 14-20, 2004) of OASYS_NEW |
Not yet assigned to a slot - 1:00 AM
Time Dependent Relaxation of Soft Tissue Elements about the Wrist Following
The purpose of this study was to examine the change in soft tissue tension over time following placement of a wrist external fixator, applied in tension.
Methods and Materials
12 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 then placed in a Model 1101 Instron mechanical testing device with a 100 lb. load cell. 20 pounds of force was then applied in tension using a cruise head of 2in/min and a sampling rate of 5 pts/sec. The change in specimen tension was then monitored over 24 hours. This was accomplished by measuring the amount of force (tension) necessary to maintain the two inserted pins at a predetermined, fixed difference. This procedure was done first for 6 unaltered specimens labeled “controls” then repeated for the remaining 6 specimens labeled the “fracture group.” This group received a dorsally based, 5mm wedge osteotomy at the level of the metaphysis, simulating a comminuted, extra-articular distal radius fracture. All data was then analyzed using the student’s T-test.
Results
The average loss in tension by the control group and by the study group (fracture group) during the 24-hour period was 55% and 59% respectively. This was not statistically significant. In 6/12 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.
Conclusions
Relaxation of wrist soft tissues occurs soon after being placed in tension by an external fixation device. Additionally, there is a tendency 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 call in to question the reliability of ligamentotaxis as the sole means of maintaining reduction of shortened distal radius fractures.