Fracture Healing

Question 1

what is the method of primary healing for bone

Answer 1

Bone remodels itself to form a ‘cutting cone’ - a structure formed of osteoclasts, osteoblasts and a central blood supply

These cones are extremely delicate - which is part of the reason why fractures need to be immobilised

The cones tend to cut across a fracture site to suture the site together

Question 2

What is the method of secondary healing for bone

Answer 2

More common of the two

‘callus healing’

Requires a degree of stability, but some controlled motion between fracture surfaces gives relative stability

Question 3

what is the timeline of secondary healing

Answer 3

0-1 weeks
Haematoma/inflammation
Bleeding
Resorption

1-4 weeks 
Soft callus 
Fiberous tissue 
Cartilage  
Woven bone 
Endosteal and periosteal callus 

4-16 weeks
Hard callus
Calcified soft callus resorbed + replaced with woven bone
Fracture is considered ‘healed’ at this point

1-2 years  
remodeling 
Woven bone replaced by lamellar bone  
Process is the same as primary healing  
Medullar canal reforms

Question 4

What are factors that affect fracture healing

Answer 4

soft tissue trauma 
neurovascular injury 
bone loss
immobilisation
infection
tumours
bone type
bone site
interposition of soft tissues 
smoking
diabetes
nutrition
drugs
hormones 
associated head injury

Question 5

what is the definition of non-union

Answer 5

lack of healing within the expected time

Question 6

what are the different definitions of non-union with different bones (radius, scaphoid, tibia/femoral)

Answer 6

Distal radius = 6 weeks

Scaphoid = 8 weeks

Tibia/femoral = 16 weeks

Question 7

what is the definiton of radiological union on an XRAY of a fracture

Answer 7

visible trabecular bridging is observed on at least 3 out of 4 cortices on an X-ray

Question 8

what are the complications of fracture healing

Answer 8

malunion

Nonunion

Avascular necrosis

Osteopenia

Question 9

what are some common fracture mimics and artifacts seen on XR

Answer 9

Growth plates
Especially in the humerus/femur
Discontinuity in the proximal portion usually seen
Age must be taken into account

Apophysis
Normal secondary ossification center
Located in non weight bearing areas of bone
Usually the side of a tendon/ligament attachment

Ossicles 
Similar to apophysis 
Secondary ossification centers 
Remain separate from adjacent bone  
Ovoid shape 
Typically occur in set locations  
e.g. navicular bone accessory ossicle  

Vascular lines
Luscencies, usually longtitudinal that appear like fractures

Harris lines
Dense transverse lines (usually distally)
Indicates areas of growth plate stopping due to physiological insult