25 terms

1-2 Fracture mechanics

STUDY
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What are the 5 forces?
Tension - pulling
Compression
Shear - eccentric loading
bending
Torsion
What is the strength of bones dependent on?
material and structural properties
force orientation
Rate of load
What force most commonly causes comminuted?
High energy - like a gun shot
What is the difference between greenstick and fissure fractures?
incomplete fractures
Green stick - goes through both cortex
Fissure - only one cortex is fractured
What force causes a transverse fracture?
bending forces
What force causes oblique fractures?
bending and torsion load
What force causes spiral fractures?
torsional load
What are segmented and comminuted fracture?
Segmented - 3 pieces with the fracture lines don't communicate
Comminuted - fracture lines communicate
What are the 3 types of open fractures?
type 1 - clean soft tissue <1cm
Type 2 - soft tissue laceration >1cm, no flaps
Type 3 - soft tissue flaps and lack of coverage
What are the Salter-Harris types?
1 - Physis (separation)
2 - Metaphysis/physis
3 - Epiphysis/physis
4 - Metaphysis/physis/epiphysis
5 - Physis (compression)
Why is type 1 salter-harris in humans not going to cause growth problems?
it only affects hypertrophic zone, not the germinal cells in the epiphysis
What is the difference between direct and indirect extrinsic causes of fractures?
Direct - hit by car or bullet
Indirect - falling out of a car or bag - radiating forces
What are the 3 intrinsic causes of fractures?
Physiologic disruption - the tension from quadriceps
Pathologic - Ca imbalance cause weak bones
Stress fractures - repeated stress without rest
How do you classify displacement of a fracture?
location of the distal segment relative to the proximal segment
How do you describe a fracture?
open or closed
Configuration - type of fracture
Location - on bone
Right or left
Bone
Displacement
What is secondary bone healing?
healing of bone with a gap
What are the 4 phases of secondary bone healing?
Inflammatory phase
Reparative phase
Remodeling phase
Strength dependent on callus formation
Why is the diaphysis fracture have worse healing than other fracture sites?
the central blood supply is damaged due to fracture and so the fracture site gets blood from periosteum and soft tissues
What happens during secondary bone healing?
fibroblast lay down collagen that turns to cartilage then turns to woven bone then under stress turns to laminar bone
What are the requirements for primary bone healing?
rigid fixation
gaps <1mm
What occurs in primary bone healing?
Osteoclast cross the fracture line and osteoblast replace it with bone
Which type of bone healing is stronger faster and which is better return to function?
secondary - stronger faster due to callus
Primary - return to function
How do you drill holding screws?
the near cortex is size of threads and far cortex is size of core
How long does it take to heal a fracture in a 2month old and 7 year old?
2 month - 3-4 week
7 year old - 8-12 weeks
How do the following fractures stabilize with the forces
Oblique
Transverse
Comminuted
Spiral
Oblique - little stable
- shear with compression and unstable with bending or torsion
Transverse - stable with compression
- unstable with bending or torsion
Comminuted - little stable unless compressed (stable with torsion and some compression and bending
Spiral - if reduced stable to compression and torsion