Ultrasonography as a diagnostic modality of tibial stress fractures

Tibial stress fractures (SFs) are a common orthopedic problem during military basic training. Bone scan is considered the gold standard for diagnosing this condition. Several case reports have described sonographic features of stress fractures. This is a prospective, double-blind study to compare diagnostic ultrasound (US) examination with isotope bone scan in diagnosing SF. Thirty-one soldiers who were referred to the nuclear medicine service for a bone scan to rule out tibial SF participated in this study. The SF lesions of the lower extremities were classified according to the classification criteria introduced by Zwas et al. US examination was performed on the same day. Areas of cortical thickening and other pathologies like bone surface irregularity and bone discontinuity were recorded. Each examination was graded as either normal or suggestive of representing a SF. Thirty of 62 tibiae were diagnosed as having SF according to bone scan, whereas US examination suggested SF in 35 tibiae. US examination was positive in 20 of 30 tibiae with SF (67% sensitivity, 53% specificity). Although US correctly diagnosed SF in 20 tibiae, bone scan remains the chosen imaging modality to detect SF in soldiers. US was not found to be a reliable modality to diagnose SF.