Effectiveness of Therapeutic Ultrasound in Identification of Tibial Stress Fractures

Objective: To determine how accurately continuous wave therapeutic ultrasound with 3 MHz frequency could identify tibial stress fractures as revealed by X-ray and Magnetic resonance imaging.

Materials and Methods: One hundred - fifty patients with suspected unilateral tibial stress fracture volunteered for this study from March 2003 to December 2006. Continuous, 3MHz ultrasound was applied to uninvolved (control) and involved tibias with 2w/cm2 intensity for 30 seconds. Pain responses to ultrasound was noted in terms of visual analogue scale and investigating physiotherapist put up one of the two responses such as no stress fracture (VAS 0 to 5) and stress fracture (VAS 5 to 10). Results of ultrasound test were compared with X-ray and MRI findings to determine if continuous therapeutic ultrasound could predict whether subject had tibial stress fracture or no tibial stress fracture.

Results: Therapeutic ultrasound has better sensitivity, less specificity and accuracy as that of X - ray when compared with magnetic resonance imaging as a gold standard. The predicted sensitivity, specificity and accuracy of therapeutic ultrasound were 43.03%, 32.39% and 38% respectively.

Conclusion: Ultrasound is not accurate enough to serve at present as a substitute for MRI, particularly because of the considerable proportion of false positives.