Presentation
Left hip pain for two weeks after starting a new exercise regimen.
Patient Data
Frontal view of the pelvis is normal.
Three-phase bone scan + SPECT
Two-phase bone scan with planar and SPECT of the hips and pelvis
Planar (blood pool) shows faintly increased radiotracer accumulation in the region of the left femoral neck and lesser trochanter.
Planar (delayed) shows intense radiotracer uptake in the base of the left femoral neck, compressive side, in the region of the lesser trochanter. This finding is characteristic of a femoral neck stress fracture in the appropriate clinical setting.
Coronal and axial SPECT images increase the conspicuity of the stress fracture due to the increased contrast resolution and can also improve anatomic localization. These reasons are likely why the addition of SPECT in this scenario has been shown to increase the sensitivity and accuracy of bone scintigraphy.
Coronal T1 and T2 fat sat images of the pelvis demonstrate abnormal marrow edema (T1 dark, T2 bright) in the base of the left femoral neck, compressive side. There is an underlying transverse fracture line (T1 and T2 dark) originating from the compressive side cortex and extending approximately one-third of the way across the femoral neck.
Case Discussion
Radiotracer uptake on a bone scan in the femoral neck due to a stress fracture can have two patterns:
Focal uptake along the inferior aspect of the femoral neck towards the lesser trochanter is associated with a compression-type stress fracture (as in this case). This type is seen most commonly in young adults and is low-risk, allowing for conservative treatment.
Focal uptake along the upper portion of the femoral neck towards the greater trochanter is indicative of a tensile-type stress fracture, more often seen in older individuals. A tensile femoral neck stress fracture is prone to progress to a displaced femoral neck fracture with a risk of avascular necrosis and hence may require operative stabilization.
SPECT imaging added to planar imaging has been shown to improve sensitivity and accuracy for the diagnosis of femoral neck stress fractures.
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