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External fixator

Principles

1. Focus - area of bone supported (ie fracture)
2. Segment - area of bone into which external fixator is inserted in order to control the focus

Components

1. Pin (fix frame to bone)
   • Screw-threaded half pins: applied to side of bone, low risk of neurovascular damage, but increased risk of loosening
   • Transfixing pins: passes through all of bone to other side, better control of fracture site; disadvantage of neurovascular injury and risk of loosening - used only in simple constructs or temporary stabilisation of severely traumatized limbs
   • Tension wired: passes through all of bone, tightened to support bone, less traumatic to blood supply, but more expensive and complicated to apply
2. Frame
   • Unaxial: half pi; frame adjacent to one side of pin only
   • Circular: ilizarov frame
   • Hybrid: supports one segment using rings and other segments using uni-axial constructs
   • Pinless: metal clamps that tighten onto bone and therefore avoid interfering with medullary canal for lateral internal fixation

Indications:

• Polytrauma
• Peri articular fractures
• Intra articular fractures
• Open fractures
• Pelvic fractures (to reduce life threatening haemorrhage)
• Bone transport

Complications

• Pin-track infection
• Chronic pain
• Pin loosening and breakage
• Neurovascular damage
• Joint stiffness

Intramedullary nails

1. Material
   • stainless steel, titanium, titanium alloys
2. Locking
   • Screws inserted proximally and distally
   • Provide longitudinal and rotational stability
   • May be static or dynamic
   • Dynamisation: process of removing one or more screws in order to allow collapse - increases the loading of the fracture site and hastens union
3. Controversies of reaming
   • Enlarges medullary canal - allows stronger, wider nail
   • Weakness due to loss of endosteal bone
   • Disturbance of medullary blood supply may cause cortical necrosis
   • Time consuming
   • May cause embolisation