Internal Fracture Fixation: IM Pin and Cerclage Wire Flashcards
advantages of IM pins
- affordable inventory
- simple application
popular choice
4 forces
- bending
- axial compression + shear
- torsion
- tension
what are the limitations of IM pin and wire fixations?
- limited fracture scenarios
- requires rapid healing
- provides limited stability
- prone to complications
- technical errors, case selection errors
what % of canal fill do we aim for with IM pins?
60-70% medullary canal filled
as long as not past this %, general health of bone is good
what fixations can resist compression?
- ESF
- IM Pin + ESF
- ILN: interlocking nail
- bone plate and screws
what forces can IM pins resist vs not resist?
CAN resist bending!
CANT resist compression/shear, rotation, tension
what fixations can resist rotation?
- IM pin + cerclage wire
- IM pin + ESF
- ILN
- bone plate + screws
what are common additions to IM pins?
- cerclage wire: bone must be perfectly reconstructed ie it doesn’t look broken anymore
- external fixator: “tied in” ie pin out on one end of bone
- plate + screws
what are IM pins made of?
316L stainless steel
what common terminology can you hear regarding IM pins
- steinmann pins: larger
- kirschner wires: “K wires” - small steinmann pins
what does cerclage mean
to encircle or wrap in a bundle
what effect is cerclage wire applying?
interfragmentary compression
what fracture configurations can be good candidates for cerclage wiring? (remember: needs to be able to be perfectly reconstructed)
- long oblique
- single large oblique butterfly
- long spiral
basically just think of LONG OBLIQUE
T/F: if applied the whole way around the bone, cerclage wire can be the sole method of fixation
FALSE: cerclage wire is NEVER used as the sole method of fixation!
how does cerclage wire affect the vascular supply?
- tight, small diameter wires do NOT impede blood supply
- loose wire devascularizes and disrupts callus formation: enough micromotion to interfere with vascularization. also a loose wire just isn’t doing that job
what defines something as a long oblique fracture?
when the fracture line length is AT LEAST 2x the diameter of the bone!!
what happens if you try to use cerclage wire on a comminuted fracture?
collapse and wire loosening
what are the rules for cerclage wiring?
- perfect reconstruction needed
- need AT LEAST 2 WIRES !!
- spaced 1/2 bone diameter apart from the edge of the fracture. if they’re right next to each other; won’t be effective
what is the “weakest link” of circlage wiring?
the way it is secured- by twisting. there are multiple ways to secure the wire but the most common is to just twist it
want a nice even twist, and leave 3 twists and then cut
how do you ensure that the wire has a proper twist?
- firm traction during application
- watch the wire closely to make sure it’s even
what are the rules for IM pin + cerclage wire application?
- PERFECT anatomic reconstruction
- only LONG OBLIQUE/spiral configuration
- properly spaced wires
- > 2 cerclage wires
- no loose wires!!
- do NOT entrap soft tissues
- IM pin 60-70% canal diameter
what bone is not commonly repaired using IM pins? why?
radius- sandwiched top and bottom with joints, so not good access
contrasting to the femur: which has one side of the bone not in the joint
what are variants of cerclage wiring?
- cerclage + K wire: used when the bone is conical shaped: the wire might just slide right off so trap it with a K wire
- hemicerclage: holes drilled through the bone and the wire goes thru the bone. mechanically inferior
- intra-fragmentary: maxillary fractures
what is hemicerclage?
cerclage variant where holes are drilled thru the bone and wire goes thru the holes
mechanically inferior, can damage bone or affect IM pin placement
what are tension band wires used for?
- opposes pull of muscle or ligament on fragment
- K wires control shear/rotation
- figure 8 converts tension to compression
what is ILN?
interlocking nail: IM pin combined with bolts that lock into the IM pin
what forces can an ILN combat?
bending, rotation, axial compression forces
