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
Clavicle
First rib
7th-9th ribs
Scapula (coracoid)
Ulna
Phalanx tuft
5th metatarsal
Hook of hamate
parachuting
persistent tic
backpacker
coughing, golfing,
rowing
trap shooting
pitchfork work,
wheelchair
guitar playing
running on banked track fields
equipment holding (tennis, golf,
baseball)