What is the general indication for external fixation?
Soft tissue concerns - primary or damage control
What are the advantages of external fixation
- soft tissue sparing
- early WB
What are the disadvantages of external fixation
- psychology
- weight
- infection
- cost
What is the rate of infection in external fixation
20-100%
What happens if bone is lengthened too slow
Bone develops a callus, preventing distraction
What happens if bone is lengthened too fast
There are traction injuries to neurovascular structures and bone which reduced the likelihood of bone consolidation
What are the factors of tension-stress effect
- stability of fixator
- distraction rate and frequency (for high frequency instruments, you have to irrigate in order to increase the thermal necrosis threshold)
- osteotomy type and position
How long after the osteotomy do you have to wait before you start to distract?
5-7 days
What is the ideal rate for lengthening a bone
1 mm a day in four 0.25mm intervals (ie a quarter turn)
What is a consequence of excess motion or distraction too quickly
Pseudoarthrosis
What is a tensioning device
Stiffens wires and increase stability at bone interface
How much tension is needed in cancellous bone
90kg
How much tension is needed in tibia and metatarsals
100-110kg
What are the steps in inserting a Schanz pin
- drill into bone
- insert Shanz pin
- attach pin to ring with fixation bolt
- rings
What are the steps in inserting a wire
- no need to predrill
- insert wire
- secure wire to ring with fixation bolt
- tension the unsecured side
- secure free side to ring with fixation bolt to capture tension
- tensioning device
What are the four general principles of external fixation
- soft tissue sparing
- gradual correction
- safe zones
- construct stability
What are the factors affecting construct stability
- number of pins and trans osseous wires
- pin and wire diameter
- pin spread
- multiplanar orientation
- distance of connecting bar from mechanical axis of bone
- proximity to segment in need of immobilizing
- tensioned wires
- limit use off connecting components
- reducing thermal necrosis
What are the different types of external fixation?
- unilateral frames - pins
- multiplanar from - pins
- circular frame - wires
- hybrid frames - wires and pins
- Taylor spatial frame - wires and pins struts,
