Bone Fracture

KEY FACTS

• Fracture (fx): Traumatic discontinuity of bone usually involving both cortical and trabecular bone
• Stress fx: Fx occurring in normal bone due to excessive repetitive submaximal loading
• Insufficiency fx: Fx occurring in diffusely weakened bone subjected to normal loading
• Pathologic fx: Fx occurring in focally weakened bone subjected to normal loading

• Standard radiographs will not show

85% rib fxs, 50% nasal bone fxs, 15% scaphoid fxs

25% pediatric elbow fxs, 100% chondral fxs
• Fx

Focal cortical disruption with soft tissue edema, hematoma, or callus ± reverberation artifact at fx line

→ fx edge resorption with hypoechoic osteoid deposition across fx line

→ progressive callus mineralization
• Stress fx

Thickened hyperechoic periosteum at symptomatic site

Visible on US before radiographs

Hyperemic thickened periosteal rim on color Doppler imaging
• Pathologic fx

Often wider fx line ± cortical irregularity extending beyond fx margins

± visible tumor protruding from fx gap

US-guided biopsy helpful
• Chondral fx

Focal disruption of hypoechoic cartilage

± juxtachondral soft tissue edema or hematoma
• Insufficiency fx

US insensitive to detection in early stage

Focal cortical hyperostosis or exuberant callus in later stages

• Fracture (fx): Traumatic discontinuity of bone usually involving both cortical and trabecular bone
• Trabecular microfracture: Fx limited to trabecular component of bone without clear fx line

Diffuse bone marrow edema on MR imaging but no discrete fx line
• Stress fx: Fx occurring in normal bone due to excessive repetitive submaximal loading
• Stress reaction of bone: Trabecular microfracture occurring in normal bone due to repetitive excessive submaximal loading
• Insufficiency fx: Fx occurring in diffusely weakened bone subjected to normal loading

Usually due to osteoporosis; other causes include renal osteodystrophy and chronic bisphosphonate therapy
• Pathologic fx: Fx occurring in focally weakened bone subjected to normal loading

Usually due to metastatic infiltration or primary bone tumor; infection is another cause

• Best diagnostic clue

Focal disruption of bone cortex with juxtacortical soft tissue edema/hemorrhage ± callus formation
• Location

Most common in ribs, distal radius, scaphoid, metacarpals, phalanges, metacarpals, nasal bones, skull, and vertebral bodies

• Gold standard for fx detection

Detects both cortical and trabecular component of fx as well as stress reaction with high sensitivity, specificity, and negative predictive value

• Fx

Focal cortical disruption with adjacent soft tissue edema, hematoma, or callus

– ± reverberation artifact (“chimney phenomenon”) or shadowing artifact at fx site

– Effusion, hemarthrosis, or lipohemarthrosis if intracapsular surface extension is present

Later, fx edge resorption occurs with hypoechoic osteoid deposition across Fx line

→ progressive callus mineralization

→ complete callus mineralization → smooth bump on cortical contour
• Stress fx

Thickened rim of hyperechoic periosteum at symptomatic site

– Visible on US before radiographs

Hyperemia of thickened periosteum on color Doppler imaging

→ progressive increasing echogenicity of periosteal thickening due to increasing bone deposition
• Pathologic fx

Often wider fx line ± cortical irregularity extending beyond fx margins

± visible tumor protruding from fx gap
• Insufficiency fx

Periosteal thickening and hyperemia with adjacent soft tissue edema

± focal cortical irregularity or disruption

Overall sensitivity of US for early insufficiency fx is low

– Propagates from trabecular bone and is therefore not visible on US at early stage
• Chondral fx

Focal disruption of hypoechoic cartilage

± juxtachondral soft tissue edema or hematoma

– Heals by fibrocartilaginous repair

– No callus formation

Apr 9, 2020 | Posted by admin in MUSCULOSKELETAL IMAGING | Comments Off