Session IX - Tibia

Non-Invasive Measurement of Compartment Syndrome

Michael J. Sullivan, MD; Kyle F. Dickson, MD; Bruce Steinberg, MD; Leann Myers, PhD; Tulane University, New Orleans, LA; Jacksonville Orthopaedic Institute, Jacksonville, FL

Compartment syndrome occurs when tissue pressure within a limited space rises to the point where tissue perfusion is compromised. The clinician diagnoses compartment syndrome with a combination of clinical exam and pressure measurements. Current pressure monitoring utilizes devices and techniques that invasively measure intracompartmental pressure. This study compares the effectiveness of a commercially available invasive intracompartmental pressure-measuring device with an investigational noninvasive hardness-measuring device in clinical subjects undergoing examination for possible compartment syndrome.

Two hundred seventeen (217) compartments were measured in seventy-five (75) patients. Limbs tested included leg, forearm, thigh, and arm. The pressure of compartments in the affected limbs was measured with an invasive pressure-measuring device. The hardness of compartments in the affected limb and the contralateral limb was measured with the investigational device. Pressure was expressed in millimeters of mercury (mmHg). Hardness was expressed as a ratio of affected to unaffected side. Pressure values and hardness ratios were compared to each other as continuous variables and to the clinical diagnosis of compartment syndrome as discrete variables. Within a limb diagnosed with compartment syndrome, only the compartment with the highest pressure reading was compared to compartments in limbs without compartment syndrome.

The diagnosis of compartment syndrome by pressure measurements was compared to the clinical diagnosis of compartment syndrome. A correct diagnosis was made in 64 of 74 (86.5%) compartments. The specificity was 0.96 and the sensitivity was 0.66. The diagnosis of compartment syndrome by hardness measurements was compared to the clinical diagnosis of compartment syndrome. A correct diagnosis was made in 58 of 75 (77.3%) compartments. The specificity was 0.82 and the sensitivity was 0.68. Logistic regression equations were used to yield a z score; a test with a higher z score is a better predictor of outcome. The z score for pressure was 2.66 (p = 0.0079) and the z score for hardness was 3.03 (p = 0.0024). The direct correlation between pressure values and hardness ratios was 0.47. This represents a moderate correlation. The mean hardness ratios with 95% confidence intervals for those with and without the diagnosis of compartment syndrome were 2.56 (95% C.I. = 2.01 - 3.12) and 1.50 (95% C.I. = 1.32 - 1.69), respectively.

This study compares the invasive measurement of pressure and the noninvasive measurement of hardness as objective tests used in the diagnosis of compartment syndrome. Clinically the hardness measuring devices have the advantage of being noninvasive. Statistically hardness and pressure tests are similar. This study supports the use of noninvasive measurement of hardness as an objective test to be used in making the diagnosis of compartment syndrome.