CASE 7
Bone scan (Delayed)
HISTORY: A 19-year-old female runner presents with bilateral leg pain since one week ago with negative x-ray.
Bone scan requested to rule out stress fracture.
FINDINGS:
Three phase bone scan. Blood flow to both legs (not shown): normal. Blood pool images show mild hyperemia in posterior aspect of left tibia. Delayed images show linear increase uptake in posterior cortex of left tibia. There is also focal area of mild uptake in mid shaft of right tibia. These findings are compatible with shin splint in left tibia and suspicious stress fracture in right one.
DIAGNOSIS:
Stress fracture and shin splint.
PEARLS AND DISCUSSION:
Stress fracture must be differentiated from shin splint. Stress fracture is caused by repeated abnormal stress on normal bones such as with ballet dancers, gymnastics, soldiers and runners. While shin splint is caused by abnormal stress of soleus muscle on at tibial origin. Patients with shin splint can continue with exercise if they feel comfortable.
However, patients with stress fracture must avoid exercise for at least 6 weeks, as they are at risk of sustaining complete fracture. Both entities should be differentiated from the insufficiency fracture which is caused by normal stress on abnormal bone as with osteoporosis and osteomalcia.
The potential of bone scan is in detection of fractures before they become evident on radiograph.
On three phase bone scans, stress fracture appears as focal increased uptake with increased flow on initial images while shin splint appears as linear area of increased uptake in posterior aspect of tibial cortex and usually with normal flow on initial images.
FURTHER READING:
J Nucl Med 2001; Drubach LA, et al. Assessment of the clinical significance of asymptomatic lower extremity uptake in young athletes. 42: 209-212
AJR 2010; Porrino, Jr. JA, et al. Diagnosis of proximal femoral insufficiency fractures in patients receiving bisphosphoate therapy. 194: 1061-1064
