External Fixation

ajkim1's version from 2015-06-17 12:36


Question Answer
What does AO stand for?Arbeitgemeinshaft fur Osteosynthesis fragen
Founding principles of AOAccurate anatomic reduction, avoid ST damage and preserve blood supply, rigid internal fixation, early active ROM (not early WB)
Primary bone healingNo bone callus, haversian remodeling, cone cutting, stress shielding
Lag principle"Lagging requires correctly drilled holes, compress fracture fragments, screw cortex to cortex (screw bites the bone causing lag)
Order of placing a screwOverdrill, underdrill, countersink, measure, tap, screw
Screw used with syndesmosisPosition screw
Screw that holds things in place but does not compressPosition screw
Distance between 2 threadsPitch
Smaller pitchCortical
Larger pitchCancellous
1.5 screw's core1.0
1.5 screw's underdrill1.1
2.0 screw's core1.4
2.0 screw's underdrill1.5
2.7 screw's core1.9
2.7 screw's underdrill2.0
3.5 screw's core2.4
3.5 screw's underdrill2.5
4.0 screw's core1.9
4.0 screw's underdrill2.5 or 2.7
Weakest part of a screwRunout
What makes a screw self-tapping?Tip
Parts of a screwLand, shank, thread
Is it completely necessary to overdrill with a partially threaded screw?No
Why must you countersink?Prevent ST irritation, prevent stress risers, so screw doesn't spin (flush with cortex)
What is the handle made of?Pressed linen
Neutralization plate?Using a screw and a plate neutralizes shear forces
What 2 steps are skipped in plates?Overdrill and countersink
Prevents gap at far cortexPrebending
Put screw in off center and it will slide into the centerLoad screw
Plate working distanceScrew nearest to the fracture for more strength
Locking plateFixed angle plate, internal-external fixator, 0.1-0.2 mm off the bone, doesn't ride up on the bone or fracture
Indications for locking platesOsteopenic bones, comminuted fractures, inability to attain anatomanicity, allows for early WB
Combines locking and non-locking plateHybrid plate
Mechanism of hybrid platePut non-locking screw first, then locking
Indication for hybrid plateCalcaneal fractures
Is a K-wire internal or external?Internal
Indications for external fixationPolytrauma, open fracture, deformity, corrections, limb lengthening, protect soft tissue, compromised ST, osteomyelitis
Basis for the use of external fixator in unstable distal long bone fractureLigamentotaxis
Mechanism of ligamentotaxisBy applying longitudinal distraction force, the soft tissues surrounding the fracture help mold the bony fragments and facilitate reduction
OsteotaxisSame as ligamentotaxis, but with bone
Rate of distraction1mm per day
According to MCG, the best rate of distraction for the lesser MTs5/8 (0.5-0.7) mm a day
Time between surgery and beginning of distraction processLatency period
Latency period for adults10 days
Latency period for children5 days
How long do you have a fixator on after you've reached appropriate length?1 mo for every c of distraction, or until there's radiographic evidence of consolidation
Fracture blisterCan use an external fixator as a temporizing measure
How to increase external fixator stability and strengthDecrease frame distance, increase pin diameter, increase number of pins, increase number of connecting rods, multiplanar fixation, controlling near and far segments, cooling during drilling
Slowly disassembling an external fixatorDynamization
Purpose of dynamizationPrep bone for full WB, loosen things up to avoid fracture
External fixator shields bone from external forces, takes stress from the boneStress shielding
Classification of PTIChecketts-Otterburns
Checketts 1Slight redness, little discharge
Checketts 1 txImproved pin site care
Checketts 2Redness of skin, discharge, pain, tenderness in the ST
Checketts 2 txImproved pin site care, oral antibiotics
Checketts 3Grade 2 but doesn't improve with antibiotics
Checkett's 3 txAffected pin/s resited and external fixation can be continued
Checkett's 4Severe ST infection involving pins, sometimes with loosening of pin
Checkett's 4 txExternal fixation must be abandoned
Checkett's 5Grade 4 but also involvement of the bone, also visible on radiographs
Checkett's 5 txExternal fixation must be abandoned
Checkett's 6Infection occurs after fixator removal, pin tract heals initially but will break down and discharge in intervals, radiograph shows new bone formation and sometimes sequestra
Checkett's 6 txCurettage of the pin tract
How much longer must fixator be kept on DM patients?2x longer
Safe zoneNo MSK or NV
Hazardous zoneMSK, no NV
UnsafeBoth MSK and NV
Indication for K wiresHammertoes or bunions
K wire sizes.028, .035, .045, .054, .062
S pin indicationBigger bones
S pin sizes5/64, 12/64 in
Do pins and wires provide compression?No
Ways to attach tendon to boneAnchor, biotendodesis screw, trephine plug, button and anchor, staple, tunnel, mason-allen stitch, AO screw and washer
Antibiotic most commonly prescribed for an external fixation PTI?Keflex and Cipro
Remove self-tapping screws byScrew forward once, then unscrew it out
3 reasons to countersink a screwST irritation, prevent stress riser, prevent spinning screw
How much stress before non union2% strain
Dahl 0WNL
Dahl 0 txWeekly pin care
Dahl 1Marginal inflammation, no drainage
Dahl 1 txDaily pin care with mild soap or 1/2 H202 + saline
Dahl 2Inflammed, serous
Dahl 2 txAggressive pin care, PO antibiotics
Dahl 3Inflammed, purulent
Dahl 3 txTreat like grade 2
Dahl 4Erythema, inflammation, puruen discharge, osteolysis at both cortices
Dahl 4 txRemove pin immediately, debride pin site with peroxide
Dahl 5Inflammation, purulence, osteolysis, sequestra, brodie's abscess, deep-seated infection
Dahl 5 txAbandon and culture specific antibiotics