Stress Fracture

• Fractures produced as a result of repetitive stress on bone 
• Most common locations
• Lower extremity (calcaneus, tibia, fibula)
• Thoracic vertebra
• Sacrum
• Ilium
• Pubic bone
• General risk factors
• New / different / rigorous repetitive activity
• Female sex
• Increased age
• Caucasian race
• Low bone mineral density
• Low calcium intake
• Specific risk factors and bones involved
• Clay shoveler’s fracture
• Spinous process of lower cervical / upper thoracic spine
• Clavicle
• Postoperative (radical neck dissection)
• Coracoid process of scapula
• Trap shooting
• Ribs
• Carrying heavy pack, golf, coughing
• Distal shaft of humerus
• Throwing ball
• Coronoid process of ulna
• Pitching ball, throwing javelin, pitchfork work, propelling wheelchairs
• Hook of hamate
• Swinging golf club / tennis racquet / baseball bat
• Spondylolysis
• Ballet, lifting heavy objects, scrubbing floors
• Femoral neck
• Ballet, long-distance running
• Femoral shaft
• Ballet, marching, long-distance running, gymnastics
• Obturator ring of pelvis
• Stooping, bowling, gymnastics
• Patella
• Hurdling
• Tibial shaft
• Ballet, jogging
• Fibula
• Long-distance running, jumping, parachuting
• Calcaneus
• Jumping, parachuting, prolonged standing, recent immobilization
• Navicular
• Stomping on ground, marching, prolonged standing, ballet
• Metatarsal (commonly 2nd MT)
• Marching, stomping on ground, prolonged standing, ballet, postoperative bunionectomy
• Sesamoids of metatarsal
• Prolonged standing
• Imaging Findings
• 15% sensitive in early fractures, increasing to 50% on follow-up
• Sclerotic band (due to trabecular compression and callus formation) usually perpendicular to cortex
• Intracortical radiolucent striations (early)
• Solid thick lamellar periosteal new bone formation
• Endosteal thickening (later)
• Follow-up radiography after 2-3 weeks of conservative therapy may reveal fracture not seen earlier
• Nuclear medicine
• “Gold standard" = almost 100% sensitive
• Abnormal uptake within 6-72 hours of injury (prior to radiographic abnormality)
• "Stress reaction" is a focus of subtly increased uptake
• Focal fusiform area of intense cortical uptake
• Abnormal uptake persists for months
• MRI
• Very sensitive modality
• Fat saturation technique most sensitive to detect increase in water content of medullary edema / hemorrhage
• Diminished marrow signal intensity on T1WI
• Increased marrow signal intensity on T2WI
• Differential diagnosis
• Osteoid osteoma (eccentric, nidus, solid periosteal reaction, night pain)
• Chronic sclerosing osteomyelitis─ Brodie’s abscess ─ (dense, sclerotic, involving entire circumference, little change on serial radiographs)
• Osteomalacia (bowed long bones, looser zones, gross fractures, demineralization) 

 
Stress Fracture. Two views of the tibia and fibula in a younger woman show a transverse lucency in the cortex surrounded by cortical thickening. There is no periosteal reaction. The patient was a dancer. The tibia is a relatively common site for stress fractures.