External Fixation Flashcards
External skeletal fixator
Method of skeletal immobilization in which bony fragments/whole bones interconnect by external stabilizing frames attached to bone with percutaneously inserted pins
Advantages of ESF
Stability - counteracts all five forces
Easy removal of implants (without surgery)
Can decrease ESF stability as heal —> promote remodeling
Can be fixed without large incision or closed
Components of ESF
Transfixation pins
External connect bars
Linkage devices (clamps)
Application of smooth transfixation pins
Young animals with simple, stable fractures
Exotics with v small bones
Inexpensive
May prematurely loosen
Negative profile transfixation pins
Threaded pins where shaft diameter of threaded portion smaller than smooth portion (creates a weak point —> can break)
Not often used
Positive profile transfixation pin
Threaded pin - threaded portions large diameter than smooth portion
+ no eat interface
- can break cortical bone if improperly inserted
- more expensive
Full vs half pin
Full - goes through both cortices, connected to bar on both sides
Half - only connected to one bar
Materials for external connecting bars
Carbon fiber (lighter)
Stainless steel (often too heavy)
Aluminum/graphite - not in vet med
Acrylic or PMMA connecting bars
Classification systems for ESF
skin surfaces penetrated (unilateral/bilateral)
# planes (uniplanar, biplanar)
Tie-in configuration (intramedullary pin + ESF)
Type 1A Configuration
Unilateral, uniplanar
Options: single clamp config (one bar), 2-connecting bars (tethered), double clamp (easier to place, weak, not common)
Type IB Configuration
Unilateral, biplanar
2 IA configurations at 90 deg to each other
+ strong against cranial-caudal bending
Type II Configuration
Bilateral, uniplanar
Type III configuration
Bilateral, biplanar
Stiffest configuration
Tie-in configuration
Intramedullary pin tied to ESF
Common in humerus/femur
Surgical placement of ESF
Strict surgical asepsis
Standard draping
Hanging leg preparation - reduction/alignment
Pin insertion
Incision for each pin
Power drill at low speed (150 rpms)
Avoid hand chucks (wobble/loosening)
Pin <20% bone diameter
Pre-drill bone with bit (esp for positive profile)
Technique for applying ESF
Place proximal + distal pin first
Reduce fracture + place connecting bars on with clamps
Dive remaining pins through clamps such that they align
Intraop fluoroscopy, or minor adjustments post rads
To preserve soft tissue…
Don’t place pins in incision/opens ounces
Don’t place pins through nerves
Don’t place pins through muscle/tendons
ESF complications
Pin loosening
Pin tract infections
Pin breakage
Iatrogenic fracture through pin tract
Fracture nonunion
Advantage of ESF
Implants removed without surgery (sedation only)
Minimally invasive placement
Biologic healing
Good alignment/rigid fixation
Good for wound management/open fractures
Allow for staged disassembly
Disadvantage of ESF
Greater degree of owner compliance / post-op care
More post-op visits
Pain associated with pins
Circular (ring) fixators
Bone lengthening (distraction osteogenesis)
Distal fractures with very small segment of bone
Angular limb deformities
Distraction osteogenesis
Bone becomes metabolically active under gentle traction
3-5 d lag phase
Distraction 1 mm/d (over 2-4x/d)
Neutral position 4-6 wks after distraction complete to allow bone healing
