Indications
Acute / damage control
- compound injures
- periarticular injuries
- high energy injuries / let soft tissues settle
- multi-trauma (avoid second hit)
Chronic / definitive management
- mal /non union
- infection
- deformity
- LLD
Problems
Pin site infections
Malunion
Non union
Construction
Pins
Diameter
- < 1/3 diameter of bone
- 3, 4, 5 mm
Materials
- stainless steels
- titanium
- HA coated
Bars
Increased diameter
- increased strength and rigidity
Clamps
Modular, multidirectional
- pin to bar
- bar to bar
Frame types
- uniplanar
- biplanar
- circular
- hybrid (combination of planar + circular)
- joint spanning (non or articulated)
Increasing strength / stiffness
Increase pin diameter
Increase number of pins
Increase pin spread on same side of fracture
- near / far / near / far
Decrease distance of bar to bone
Increase number of bars
Note: Increasing stiffness can lead to non union
- to increase union rates
- reduce stiffness
- i.e. reduce above factors
MRI issues
Non compatible
- local heating
- production of current
- costly disruption of MRI machine
- interference with pictures
Healing
1. Rigid inter-fragmentary fixation
- intramembranous ossification
If a frame is too rigid
- osteopenic nonunion
- need to reduce rigidity
- may need bone graft
2. Micro-motion / strain
- collagen formation and endochondral ossification
If a frame is too loose
- excessive callous
- hypertrophic non union
Types
Ankle External Fixation
Humerus external fixation
AO surgery foundation humerus external fixation