·         Fractures produced as a result of repetitive stress on bone 

·         Most common locations

o       Lower extremity (calcaneus, tibia, fibula)

o       Thoracic vertebra

o       Sacrum

o       Ilium

o       Pubic bone

·         General risk factors

o       New / different / rigorous repetitive activity

o       Female sex

o       Increased age

o       Caucasian race

o       Low bone mineral density

o       Low calcium intake

·         Specific risk factors and bones involved

o       Clay shoveler’s fracture

§         Spinous process of lower cervical / upper thoracic spine

o       Clavicle

§         Postoperative (radical neck dissection)

o       Coracoid process of scapula

§         Trap shooting

o       Ribs

§         Carrying heavy pack, golf, coughing

o       Distal shaft of humerus

§         Throwing ball

o       Coronoid process of ulna

§         Pitching ball, throwing javelin, pitchfork work, propelling wheelchairs

o       Hook of hamate

§         Swinging golf club / tennis racquet / baseball bat

o       Spondylolysis

§         Ballet, lifting heavy objects, scrubbing floors

o       Femoral neck

§         Ballet, long-distance running

o       Femoral shaft

§         Ballet, marching, long-distance running, gymnastics

o       Obturator ring of pelvis

§         Sooping, bowling, gymnastics

o       Patella

§         Hurdling

o       Tibial shaft

§         Ballet, jogging

o       Fibula

§         Long-distance running, jumping, parachuting

o       Calcaneus

§         Jumping, parachuting, prolonged standing, recent immobilization

o       Navicular

§         Stomping on ground, marching, prolonged standing, ballet

o       Metatarsal (commonly 2nd MT)

§         Marching, stomping on ground, prolonged standing, ballet, postoperative bunionectomy

o       Sesamoids of metatarsal

§         Prolonged standing

·         X-ray

o       15% sensitive in early fractures, increasing to 50% on follow-up

o       Sclerotic band (due to trabecular compression and callus formation) usually perpendicular to cortex

o       Intracortical radiolucent striations (early)

o       Solid thick lamellar periosteal new bone formation

o       Endosteal thickening (later)

o       Follow-up radiography after 2-3 weeks of conservative therapy may reveal fracture not seen earlier

 

 

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.

Click here for a larger version of the same photo

 

 

 

·         Nuclear medicine

o       “Gold standard" = almost 100% sensitive

o       Abnormal uptake within 6-72 hours of injury (prior to radiographic abnormality)

o       "Stress reaction" is a focus of subtly increased uptake

o       Focal fusiform area of intense cortical uptake

o       Abnormal uptake persists for months

·         MRI

o       Very sensitive modality

o       Fat saturation technique most sensitive to detect increase in water content of medullary edema / hemorrhage

o       Diminished marrow signal intensity on T1WI

o       Increased marrow signal intensity on T2WI

·         CT is the least sensitive modality

·         Differential diagnosis

o       Osteoid osteoma (eccentric, nidus, solid periosteal reaction, night pain)

o       Chronic sclerosing osteomyelitis─ Brodie’s abscess ─ (dense, sclerotic, involving entire circumference, little change on serial radiographs)

o       Osteomalacia (bowed long bones, looser zones, gross fractures, demineralization)