SLR - November 2009 - Farlyn R. Charlot
Reference:
Banal, F., Gandjbakhch, F., Foltz, V., Goldcher, A., Etchepare, F., et al. (2009). Sensitivity and Specificity of Ultrasonography in Early Diagnosis of Metatarsal Bone Stress Fractures: A Pilot Study of 37 Patients. Journal of Rheumatology, 36(8), 1715-1719.
Scientific Literature Review
Reviewed by: Farlyn R. Charlot, DPM
Residency Program: Yale New Haven Hospital/VA
Podiatric Relevance:
This prospective pilot study discusses the implementation of ultrasound as an imaging modality to assess metatarsal stress fractures for daily practice, and further proposes an imaging algorithm.
Methods:
Forty-one feet in 37 consecutive patientswith mechanical pain and swelling in the metatarsal area present for less than 3 months with a high clinical suspicion of stress fracture but negative x-rays were evaluated. Both ultrasound (US) and MRI were performed on the same day. US was performed on the dorsum of the foot, longitudinal and axial views. A positive ultrasound for an acute metatarsal fracture was defined as 2 of following: hypoechoic periosteal elevation above cortical bone, cortical disruption, and/or increased vascularity observed on positive power Doppler signal around the periosteal lesion. The same person, blinded from clinical and radiographic data, performed all US. Axial and Coronal T1 weighted and STIR MRI images were obtained and read by 2 trained rheumatologists blinded to clinical and US findings.
Results:
Ultrasound findings were compared to those of MRI scans. US had 11 true positives, 21 true negatives, 2 false negatives and 7 false positive cases of metatarsal stress fracture. The sensitivity of US was 83.3%, specificity was 75.9%, with a positive predictive value of 58.8% and a negative predictive value of 91.7%.
Conclusion:
Ultrasound is more sensitive than radiographs in early detection of stress fractures. US is an inexpensive, quick, noninvasive, and easy technique with good sensitivity and specificity. When evaluating a patient for suspected metatarsal stress fracture, if plain films are negative, an ultrasound is recommended before an MRI. If there is any diagnostic doubt after the MRI, a bone scintigraphy may be obtained.