Identification of tibial stress fractures using therapeutic continuous ultrasound

Study Design: One-group discriminant analysis. Objective: To determine whether 1 MHz of continuous ultrasound can identify tibial stress fractures in subjects. Background: Stress fractures can lead to loss of function or to more seriou s nonunion fractures. Early diagnosis is important to reduce the risk of fu rther injury and to assure a safe return to activity. Therapeutic ultrasoun d has been reported to be an accessible, less expensive alternative in diag nosing stress fractures compared with other diagnostic techniques. Methods and Measures: Twenty-six subjects (12 men, 20.33 +/- 1.37 years; 14 women, 20.78 +/- 3.8 years) with unilateral tibia pain for less than 2 wee ks volunteered to participate in the study. Continuous, 1 MHz ultrasound wa s applied to the uninvolved and involved tibias at 7 increasing intensities for 30 seconds each. Subjects completed a visual analog scale after the ap plication of each intensity to assess the pain response to ultrasound. Resu lts from the visual analog scale were compared to magnetic resonance imagin g (MRI) findings to determine if continuous ultrasound could predict whethe r subjects had a normal MRI, increased bone remodeling, or advanced bone re modeling consistent with a stress fracture. Results: Discriminant analysis on the visual analog scale correctly classif ied subjects into 1 of 3 clinical classification groups in 42.31% of the ca ses. None of the subjects found to have a stress fracture by MRI were corre ctly identified by continuous ultrasound. This resulted in a predicted sens itivity of 0% and a predicted specificity of 100%. Conclusions: A protocol using visual analog scores after the application of 1 MHz continuous ultrasound is not sensitive for identifying subjects with tibial stress fractures.