Serum creatine kinase levels are associated with extremity compartment syndrome

Limb compartment syndrome (CS) is a difficult diagnosis. Accurate measurement of compartment pressure is user dependent, and there is no consensus on values to define CS. Given the prevalence of extremity CS, difficulty in timely diagnosis, and ramifications of a delay in diagnosis, a precise and reliable means for early diagnosis is needed. The purpose of our study was to determine if a threshold serum creatinine kinase (CK) level is associated with the development of CS.

All patients with isolated tibial/fibula fractures or extremity CS admitted to a three-hospital consortium from July 1, 2001, to June 30, 2011, were identified retrospectively using coded data. Age, basic metabolic panel, lactic acid, CK, and troponin I levels were abstracted. Univariate and multivariate regression analysis was undertaken using maximum and minimum values for each laboratory test to evaluate the association between the test and CS versus tibia/fibula fracture.

Of the 97 patients in the study, 39 had CS. Tests most strongly associated with CS were maximum CK, minimum calcium, minimum blood urea nitrogen (BUN), maximum chloride, maximum lactate, and minimum HCO3. On univariate analysis, only maximum CK had adequate correlation with CS. Optimal cut points were maximum CK of greater than 4,000 U/L. Using the model CK level of greater than 4,000 U/L, chloride level of greater than 104 mg/dL, and BUN level of less than 10 mg/dL, 0 of 6 patients had CS when all three variables were absent. When one, two, or three variables were present, the percentage of patients with CS was 36%, 80%, and 100%, respectively. Using a cut point of two or more of these three variables being positive produced sensitivity, specificity, positive and negative prediction values, and total accuracy of 0.85, 0.87, 0.76, 0.92, and 0.86, respectively.

CK level greater than 4,000 U/L is associated with CS. A model combining maximal CK level greater than 4,000 U/L, maximal chloride level greater than 104 mg/dL, and minimal BUN level less than 10 mg/dL has a 100% association with CS.

Diagnostic study, level III.