Stress Fractures

Presented by M.A. Kaeser, DC

Summer 2009

General considerations

• Term is applied to a bone injury incurred as the result of repetitive stress of lower magnitude than required for an acute traumatic fracture

• Occurs in normal or abnormal bone• Radiographs are

insensitive in the early course

• Bone scans are modality of choice

• MRI will depict neoplasm versus stress fracture

Definitions

• Fatigue fracture– Occurs secondary to an abnormal

amount of stress or torque applied to a normal bone

– Examples: military recruits, runners, dancers, people who inadequately train

• Insufficiency Fracture– Occurs with normal stress placed on abnormal bone– Examples: Paget’s, osteoporosis, osteomalacia or

rickets, osteopetrosis, fibrous dysplasia, OI

Causes

• Major cause is abnormal degree of repetitive trauma• Related to increased physical trauma• May be related to muscular imbalance or altered

biomechanics (rigid supination of foot, varus deformities of foot, LLI)

• May follow certain surgical procedures (bunionectomies, hip replacement, knee surgery, fusion of the lumbosacral junction)

• Deformity from OA, esp. at knee • Menstrual irregularities may predispose women to stress

fractures

Common sites

• Metatarsals are M/C, esp. middle and distal portions of the shaft of the second and third metatarsals– Frequent in military recruits (march fracture,

Deutschlander’s disease)• Due to fatigue of the peroneus longus muscle leading

to instability of the foot

– Stress fractures of the 2nd and 3rd metatarsals may complicate Morton’s syndrome (congenitally shortened first metatarsal)

Common sites continued

• Proximal tibia– High incidence in joggers, marchers and ballet

dancers

• Calcaneus– Found in military recruits and long-distance runners

• Proximal or distal metaphyses of the fibula– Runners and ballet dancers

• Ribs– Rowers (12%)

Common sites continued

• Pars interarticularis of the lower L/S– M/C site for stress fracture

of the entire skeleton– May be found w/ or w/o

spondylolisthesis

• Sacrum– M/C in elderly women with osteoporosis– Associated with neural compromise (paraesthesias

and sphincter dysfunction)

Clinical Features

• More common in women than men

• Pain, related to activity and relieved by rest

• Soft tissue swelling with localized tenderness over the area of stress

• Bones of lower extremity are most frequently involved

• More than one site can be present

Radiologic Features

• Initial radiographic examination may fail to reveal the fracture line

• Minimum radiographic latent period is 10-21 days• CT may be helpful in demonstrating the fracture

line• Bone scan is modality of choice

– Focal uptake at the site of fracture on delayed images is characteristic but not specific

– Scan may be active for up to 12 months after healing

Radiologic Features continued

• Combination bone scan with tomography (SPECT) is useful for active stress in pars

• CT is useful when diagnosis is in doubt

• MRI – Low signal on T1– High signal on T2 if local

hemorrhage is present

(if not the signal is low on T2)

Roentgen Signs

• Periosteal response– Most frequently seen and reliable signs are

periosteal and endosteal cortical thickening– Solid pattern of periosteal response– Cortical thickening is localized to the area of

stress fracture

• Fracture line– Exuberant periosteal new bone will obscure the radiolucent

fracture line– Fracture may be too thin to see– Oblique fractures are most common, transverse and longitudinal

may occur– CT will depict fracture when plain film doesn’t

Transverse opaque bands

• Enface– Periosteal callus forms a linear, transverse,

radiopaque band– Margins are hazy and pooly defined (this

differentiates it from growth lines)

Differential Diagnosis

• Osteomyelitis– Creates a significant periosteal

response– Lytic bone destruction adjacent to

periosteal callus confirms osteomyelitis

• Osteosarcoma– Both produce a periosteal response

(stress fracture = solid, o-sarc = spiculated)

– Bone destruction will be seen with o-sarc

– CT depicts a linear radiolucent fracture line which diagnoses a stress fracture

Differential Diagnosis continued

• Osteoid Osteoma– Oval radiolucent nidus of

osteoid oseoma vs radiolucent fracture line

• Growth Arrest Lines– Discrete radiopaque lines through the metaphysis (growth

arrest lines)– Radiopaque line is broad, hazy,

ill-defined margin to its edge in stress fractures

– GALs are usually found in other bones as bilateral, symmetrical, well-defined radiopaque bands

Calcaneus parachutingClavicle persistent ticFirst rib backpacker7th-9th ribs coughing, golfing,

rowingScapula (coracoid) trap shootingUlna pitchfork work,

wheelchairPhalanx tuft guitar playing5th metatarsal running on banked track fieldsHook of hamate equipment holding (tennis, golf,

baseball)