Case Twelve - Stress Fracture
Findings: Nuclear Medicine Bone Scan: A single focus of increased radiopharmaceutical activity is identified on all three phases within the distal right fourth metatarsal.
Diagnosis: Stress fracture.
Discussion: A stress fracture is the result of repetitive, prolonged muscular action on a bone that has not accommodated itself to that action. In most instances, persons who have stress fractures are engaged in vigorous activity to which they have not yet become conditioned. Under normal circumstances, the muscle tone takes up at a faster rate than bones which result in a mechanical imbalance.
Stress fractures are divided into two categories, fatigue fractures and insufficiency fractures. A fatigue fracture is caused by the application of abnormal stress or torque on a bone that has normal elastic resistance. On the other hand, an insufficiency fracture occurs when normal muscular activity stresses a bone that is deficient in mineral or elastic resistance. The term pathologic fracture should be reserved for fractures that occur in bone already weakened by neoplasm or infection.
The stress placed on bone causes resorption and microfractures. If the patient rests and the stress decreases then repair may continue with resultant relief of pain. However, if the repair process can no longer keep up with the resorptive process, then cortical disruption and a radiographically visible fracture may ensue. Findings develop earlier on bone scan and MRI than on plain film roentgenograms. A hot spot on all three phases of a bone scan is a bone that has received repetitive trauma is indicative of a stress fracture.
Type sites for athletic stress fractures include:
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