During the early stages of a stress fracture injury there may be difficulty in identifying the fracture. A few weeks later radiology may reveal a small transverse defect in the cortex. If the injury is aggravated by further repeated stress then there may be, in addition, localized periosteal bone formation.
- note that a normal x-ray does not exclude a stress fracture, so if the clinical suspicion remains proceeding to a magnetic resonance imaging (MRI) scan of the area of concern is appropriate
- MRI may show an actual fracture line - however the typical MRI abnormality is periosteal and marrow oedema
- other possible investigations:
- isotope bone scans may also show stress fractures
- however is a non-specific investigation and rarely needed beyond investigating rib fractures
- single photon emission computing tomography (SPECT) scans (followed by a reverse gantry CT scan if positive) can be useful if a pars fracture is strongly suspected despite a normal MRI
- CT adds detail
- however with the exception of the further assessment of the pars interarticularis is not often required
- Ultrasound scanning
- may be diagnostic in cases with a fracture line, and thus a cortical break
- not advocated in isolation
Reference:
- (1) ARC. Sports-Related Musculoskeletal Disorders. Reports on the Rheumatic Diseases 2008;14.