Session V - Knee / Tibia

Fri., 10/11/13 Knee/Tibia, PAPER #69, 3:56 pm OTA 2013

Interobserver Reliability in the Measurement of Lower Leg Compartment Pressures

Thomas M. Large, MD1; Julie Agel, MA2; Daniel J. Holtzman, MD2;
Stephen K. Benirschke, MD2; James C. Krieg, MD2;
1Mission Hospital, Asheville, North Carolina, USA;
2Harborview Medical Center, University of Washington, Seattle, Washington, USA

Purpose: Accurate measurement of compartment pressures may be crucial to the correct diagnosis of a compartment syndrome. Commercially available monitors have not been validated as reliable in clinical practice. We hypothesized that there would be significant interobserver variability in measuring compartment pressures in a simulated compartment syndrome cadaveric lower leg model.

Methods: Four above-knee cadaveric specimens were used to create a compartment syndrome model with consistent lower leg compartment pressures at a mean of 47 mm Hg. This pressure was monitored with indwelling slit catheters and the authors’ serial measurements (standard deviation [SD], 2.8 mm Hg). 38 emergency department, general surgery, and orthopaedic surgery residents, fellows, and attending physicians examined the limb for firmness and a diagnostic impression assuming a diastolic blood pressure of 70 mm Hg. They assembled the compartment pressure monitor with a side-port needle and measured the pressure in the four compartments of the leg. They were observed for correct assembly of the monitor, reading the instructions, proper zeroing and flushing of the monitor for each measurement, and anatomically correct measurements. The measurements were recorded and compared to the standard pressure measurements.

Results: 47% of participants were clinically concerned for compartment syndrome based on the firmness of the leg. 61% of participants did not read the instructions. Of the 152 separate compartment measurements, 48 (31.6%) were made with proper technique, 45 (29.6%) were made with catastrophic errors in technique, and 59 (38.8%) with lesser variations in technique. Participants’ level of training, experience using a compartment pressure monitor, and reading the monitor’s instructions did not have a significant effect on the likelihood of making a catastrophic error nor did they have a significant effect on accuracy to within 5 mm Hg of the standard compartment pressure. Using proper technique significantly improved the accuracy of the measurements (P <0.005): 60% of proper technique measurements were within 5 mm Hg of the standard pressure while 42% of those with lesser variations in technique and 22% of those with a catastrophic error were within this range. Proper technique measurements were a mean of 5.9 mm Hg (SD 7.1) from the standard pressure while those with variant technique were a mean of 10.8 mm Hg (SD 12.8) and those with catastrophic errors in technique were a mean of 20.1 mm Hg (SD 14.0) from the standard pressures, respectively. This difference between the catastrophic error group and the other two groups was significant (P <0.001). 41% of measurements were below 40 mm Hg, which corresponded to a delta P of 30 mm Hg in this model. These would have resulted in the missed diagnosis of compartment syndrome.

Conclusion: There was significant variability in technique and results obtained with a compartment pressure monitor. Catastrophic errors and variations in technique were common. Proper technique improved accuracy, but even with proper technique 40% of the measurements were at least 5 mm Hg from the correct pressure. We recommend review and education of proper technique for all clinicians measuring and diagnosing compartment syndrome. The numeric value obtained when measuring compartment pressure must be seen as an approximation.

Alphabetical Disclosure Listing

• The FDA has not cleared this drug and/or medical device for the use described in this presentation   (i.e., the drug or medical device is being discussed for an “off label” use).  ◆FDA information not available at time of printing. Δ OTA Grant.