|Title : Case 671|
Age / Sex : 17 / M
Chief complaint: Right lower leg pain and swelling, 5 months ago.
Stress fracture (Medial tibial stress syndrome, shin splints)
Localized periosteal reaction is appreciated along the anterior surface of the mid tibial shaft.
Bone scan : There is focal increased uptake in the right tibia cortical area, anterolateral aspect
Stress fractures refer to fractures occurring in bone due to a mismatch of bone strength and chronic mechanical stress placed upon the bone. Fractures can either be:
Radiographs have limited sensitivity for an acute stress fracture, although repeat delayed radiographs may show changes of healing. MRI is the most sensitive modality for diagnosis of stress fracture and is an important tool to distinguish high and low-risk fractures to help clinicians for management plans.
Stress fractures normally present with worsening pain with a history of minimal or no trauma. 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 are far more common in the lower limb (~95%) than the upper limb.
High-risk sites of stress fractures are locations at greatest risk of a progression to complete fracture, displacement or non-union. These sites are under tensile stresses and have poor vascularity. These include:
Low-risk sites of stress fracture are at low risk of complications and are under compressive stresses. They include:
Plain radiographs have poor sensitivity (15-35%) in early-stage injuries, which increases in late-stage injuries (30-70%). MRI is the modality of choice with a sensitivity reported to reach close to 100%.
Plain radiographs have poor sensitivity in detecting stress fractures, as positive findings may take months to appear. During the first few weeks after the onset of symptoms, x-rays of the affected area may look normal.
Positive findings can include:
Bone scans can show evidence of stress fracture within a few days upon the onset of symptoms. As a modality, it is considered less sensitive than MRI .
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. However, as with all bone scintigraphy, this is non-specific; the increased uptake can also be due to osteomyelitis, bone tumors or avascular necrosis.
The findings are similar to plain radiography, including sclerosis, new bone formation, periosteal reaction, and fracture lines in long bones.
CT may be useful in differentiating stress fractures from bone tumor or osteomyelitis if the plain radiographs are negative and bone scans are positive.
MRI is the most sensitive modality for detecting stress fracture, and may also be useful for differentiating ligamentous/cartilaginous injury from bone injury.
Typical MRI appearance of stress fracture includes:
The use of MRI grading system for bone stress injuries is helpful for predicting recovery time (important especially for athletes).
3. Radiopaedia, https://radiopaedia.org/articles/stress-fractures
|Total applicants||36||Correct answers||29|
|장민영||국민건강보험공단 일산병원, 전문의|
|윤유성||순천향대 부천병원, 전문의|
|김형민||연세의대 강남세브란스병원, 전문의|
|Total applicants||36||Semi-Correct answers||7|