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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

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Stress fractures

Stress Fractures

Presented by M.A. Kaeser, DC

Summer 2009


General considerations
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
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
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
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
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 continued1
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
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
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
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
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
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
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
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 parachuting

Clavicle persistent tic

First rib backpacker

7th-9th ribs coughing, golfing,

rowing

Scapula (coracoid) trap shooting

Ulna pitchfork work,

wheelchair

Phalanx tuft guitar playing

5th metatarsal running on banked track fields

Hook of hamate equipment holding (tennis, golf, baseball)


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