MSK Imaging of Fractures Flashcards
2 best modalities for
- Bone injury
- Soft tissue injury
- X ray, CT
2. MRI, US
Cortical bone osteon formation
Osteoclasts carve Haversian canal through damaged or disorganized bone
Osteoblast follow and deposit concentric layers of osteoid that mineralize into new bone
Osteoblasts trapped in the matrix differentiate into osteocytes
Callus
New bone formed around a fracture site
Initially cartilaginous, hardens as mineralization takes place (endochondral ossification)
Repair process in stable vs unstable fractures
Stable: primary bone healing (no callus)
Unstable: secondary bone healing (callus forms to bridge the fracture gap) - most common
3 phases of secondary bone healing
Inflammation (5-14 days)
Repair (weeks to months)
Remodelling (months to years)
Inflammation stage
Hematoma formation Inflammatory cells migrate to site Necrotic tissue resorbed Angiogenesis Cell differentiation (chondrocytes to osteoblasts)
Repair stage
Synthesis of reparative matrix
Soft callus formation
Hard callus formation (mineralized)
Woven bone (strong but disorganized bone structure)
Remodelling stage
Replacement of woven bone with lamellar bone by osteon formation
Process influenced by Wolff’s Law
4 types of healing disruption
Delayed union
Non-union (6-9 mon)
Mal-union
Re-fracturing
What views to get?
2 views (orthogonal) 2 joints (above and below)
Salter-Harris classification
S: straight across A: above growth plate L: lower or below T: two or through growth plate ER: erasure of the growth plate or crush
8 fracture patterns
Transverse Oblique Spiral Comminuated (multiple pieces) Avulsion Impacted Fissure Greenstick
FOOSH injury
Falling on an out-stretched hand
Skeletal survey
Performed in the evaluation of children with suspected NAI <2 years old
21 views of the skeleton
Repeat in 2 weeks if suspicion is high
High specificity fractures for NAI
Classic metaphyseal lesions (most specific)
Rib fractures (posterior more suspicious)
Scapular fractures
Spinous process fractures
Sternal fractures
