Typical MRI appearance of stress fracture includes: MRI is the most sensitive modality for detecting stress fracture, and may also be useful for differentiating ligamentous/cartilaginous injury from a bony injury.

The findings are similar to plain radiography, including sclerosis, new bone formation, periosteal reaction, and fracture lines in long bones.ĬT may be useful in differentiating stress fractures from a bone tumor or osteomyelitis if the plain radiographs are negative and bone scans are positive. However, as with all bone scintigraphy, this is non-specific the increased uptake can also be due to osteomyelitis, bone tumors or avascular necrosis. Stress fractures on bone scintigraphy appear as foci of increased radioisotope activity ('hot spot') due to increased bone turnover at the site of new bone formation. As a modality, it is considered less sensitive than MRI 5. Increasing sclerosis or cortical thickening along the fracture siteīone scans can show evidence of stress fracture within a few days upon the onset of symptoms. Grey cortex sign: subtle loss of cortical density in early-stage stress injury During the first few weeks after the onset of symptoms, x-rays of the affected area may look normal. Plain radiographs have poor sensitivity in detecting stress fractures, as positive findings may take months to appear. MRI is the most sensitive modality for diagnosis of a stress fracture and is an important tool to distinguish high and low-risk fractures to help clinicians with management plans and a sensitivity reported to reach close to 100% 5,6. Plain radiographs have poor sensitivity (15-35%) in early-stage injuries, which increases in late-stage injuries (30-70%), due to possible callus formation. Lower limb: calcaneus, posterior medial tibial shaft, fibula, lateral malleolus, 2 nd to 4 th metatarsal shafts Low-risk sites of a stress fracture are at low risk of complications and are under compressive stresses 10,11: Thigh and leg: femoral neck, patella, anterior tibial cortexĪnkle and foot: medial malleolus, talus, navicular, 2 nd to 4 th metatarsal necks, 2nd metatarsal base, 5 th metatarsal, hallux sesamoid Pars interarticularis of the lumbar spine High-risk sites of stress fractures are locations at greatest risk of a progression to complete fracture, displacement or non-union as these sites are under tensile stresses and have poor vascularity 9-11: Stress fractures are far more common in the lower limb (~95%) than in the upper limb 5. Insufficiency fracture: normal stresses on abnormal bone Etiologyįatigue fracture: abnormal stresses on normal bone PathologyĪ stress fracture is the final stage of a stress injury and occurs if the bone fails to withstand a repetitive, cumulative loading force and is no longer capable to mitigate that loading stress with its own healing capabilities and breaks 7. In the lower (weight-bearing) limb, there is often a history of a recent increase of physical activity or significant alteration in the type or duration of normal athletic activity. Stress fractures normally present with worsening pain with a history of minimal or no trauma. The following conditions increase the risk of a stress injury 8: Insufficiency fractures occur more in women and older people 7,8. Epidemiologyįatigue fractures are common in athletes, especially runners and military recruits. Some authors use the term stress fracture synonymously with fatigue fracture, and thus some caution with the term is suggested. A pathological fracture, although a type of insufficiency fracture, is a term in general reserved for fractures occurring at the site of a focal bony abnormality.

Pathological fatigue