External Skeletal fixation (Lewis) Flashcards Preview

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Flashcards in External Skeletal fixation (Lewis) Deck (20):

External skeletal fixation

  • transosseous pins/wires incorporated into an extracorporeal frame
  • can be used as primary or adjunctive stabilization


External fixation: indications

  • Comminuted fractures
  • open fractures
  • infected and nonunion fractures
  • arthrodeses
  • transarticular stabilization
  • limb deformities
  • gunshot wound

*Provides stable not rigid fixation


External fixation:

Advantageous properties

  • Applied either open or closed
  • Stable constructs that counteract axial, bending and rotational forces
  • can be used as adjunctive fixation to internal fixation
  • latitude to make post-op adjustments
  • encourage early weight bearing
  • versatile and economical


Types of external fixators

  • Linear
  • Acrylic
  • Circular
  • Hybrid


External fixation:

Nomenclature: Type I

  • Type I
    • utilizes half-pin splintage
      • pins pass through both cortices of bone, but only one skin surface
    • Uniplanar and unilateral
    • Pins loaded in contilever bending
    • CIs cortex: near
    • trans cortex: far

* can be used above elbow and stifle


External fixation

Nomenclature: Type II

  • Utilizes full-pin splintage
    • pins pass through both cortices and two skin surfaces
  • Is uniplaner but bilateral
  • Pins loaded in four-point bending
    • holding both ends of the broom

*can't use above the elbow, above the stifle


External fixation

Nomenclature: modified type II

  • Utilizes both half and full pin splintage
  • Easier to apply with comparable stability

*can't go above stifle or elbow


External fixation

Nomenclature: Type III

  • Utilizes both half and full-pin splintage
  • Biplanar
    • half and full-pins are oriented in pooposing planes
  • Bilateral
  • Applies mainly to linear and acrylic fixators


External fixation


  • Surgeon must determine which construct is appropriate based on both biological and mechanical factors
  • Type III
    • very rigid constructs
    • reserved for difficult, complex cases


Fixation pins

  • Weakest link in external skeletal fixation construct
  • pin design and application have substantial effect on stability of bone-pin interface
  • don't use smooth pins


Positive profile pins

  • Superior stiffness and axial extraction characteristics
    • can be site dependent
  • Effective centrally positioned threads
  • pre-drill pilot hole
    • approximate the core diameter of fixation pin


Kirschner-Ehmer (KE)



  • Disadvantages
    • Can't place positive profile pins directly through clamps
    • Pre-drilling pilot holes is difficult
    • Difficult to place a series of parallel full-pin splintage pins


IMEX SX External fixation system

  • advantages
    • innovative clamp design allows pre-drilling pilot holes
    • allows variability in fixation pin diameter
    • better mechanics
  • disadvantages
    • connecting system not radiolucent
    • connecting clamps only accept pins of limited diameter
    • connecting rod relatively weak


IMEX SK ex fix


  • Inc stability
  • should allow use of less complex frames
  • eliminate need for double connecting bars on type I constructs


Fixation pins 


  • Place pins through small incisions
    • don't place pins through traumatic or surgical wounds
    • Close surgical wounds prior to placing pins
  • Avoid large muscle masses


Fixation pins should be inserted with

Test question

  • A low speed (150 rpm), high torque drill
  • Place most proximal and distal fixation pins first
  • twist drill bit
  • Add connecting rod close to limb
    • leave some room for swelling
  • pin should be in middle of bone
  • Pin should not exceed 30% of diameter of bone
  • beveled tip of half-pin splintage pins should completely penetrate trans-cortex
  • Place 3 or 4 pins in each fragment segment if possible
  • Interconnect frame elements and tigten fixation clamps
    • likely unnecessary


Fixation pin diameter should not exceed....

test question

30% of diameter of the bone


Stiffness of fixation pins is proportional to....

Test question

it's diameter to the fourth power 


Acrylic connecting columns


  • pins can be variable diameter
  • Pins don't have to be placed in same longitudinal plane
  • Most are radiolucent
  • Minimize distance between connecting column and the cis-cortex of bone
  • light weight
  • limited inventory and expense


Acrylic connecting columns


  • Difficult to maintain reduction if used for primary fixation
  • Polymerization of PMMA is an exothermic reaction
  • Fumes generated during polymerization are noxious, toxic, teratogenic
  • Difficult to make adjustements or remove individual interior fixation pins

*Something about good for a mandible fracture