44.ESF Flashcards
unique advantages to ESF
- adjustment of frame (alignment mods, enhance healing)2. open wound mgmt3. MI approach4. early return to function5. economical
linear ESF type Ia
unilateraluniplanar
linear ESF type Ib
unilateralbiplanar (90 degrees offset)
linear ESF type II
bilateral (180 degrees apart)uniplanar
linear ESF III
bilateralbiplanar2 bars are 180 degrees and 3rd is placed at 90 degrees
T/Fdouble clamp type I a linear ESF are mechanically inferior (less stiff) than single clamps
TRUEdouble clamps are weaker than single clamps
types of transfixation PINs
–smooth or threaded–positive vs negative profile threaded pins–central or end threaded–cancellous vs cortical–half or full pinsthreaded pins demonstrate superior pull out strength
why are negative profile bind subject to high bending moments
negative profile pins have threads cut out of them making their interface a smaller diameter –> stress riser effect–>high bending moment–> implant failure
three limitations with KE (kirschner ehmer) clamps
- must be applied to connecting bar before placement of transfixation pin (and then can’t be removed without removing the whole bar)2. acute structural deformity noted following single use tightening (material weakness)3. do not accommodate thread diameter or positive profile pins (must apply all pins first, then bar with preplaced clamps)
SK system stands for
securos external skeletal fixation clamp system
advantages to acrylic based ESF
ADVANTAGES1. can contour connecting bar component to any shape of fracture (ie. mandible) or out of plane pins2. light weight but strong mechanical option3. connecting bar/pin junction (clamp component) produces a stiffer, stronger frame–can increase strength by adding 5 notches to end of pin (knurled shaft pin)4. economical
bending stiffness of tensioned K wires used in ring fixators (circular ESF systems)
bending stiffness of a tensioned wire is SIGNIFICANTLY GREATER than the bending stiffness of a loose wiretensioned 0.062 (1.6 mm) wire has bending stiffness = 5/32 (4mm) pin
two types of K wires used for ring fixators
- OLIVE– smooth but with stoppers2. SMOOTH*** generally two wires are used 90 degrees from each other secured to the ring via bolts
ideal circular ESF or ring fixators should use how many rings in what technique
4 rings–threaded rods stabilize themtensioned wires with bolts F-N FRACTURE N-F
T/FType I b frames have a greater resistance to shear than type II frames
True
placing a second bar on a type Ia frame will increase construct stiffness by how much?
placing a second connecting bat on a type I a frame will increase the frames resistance to axial stiffness by a factor of 2.5BUT adding this second bar to Ia is = stiffness obtained with a II b frame
ideal number of pins per fragment to increase ESF frame stiffness and decrease pin-bone interface stress
increase the # of pins up to 6-8 per construct or 3-4 per fragment (placing more than 4/fragment does NOT increase stiffness)MINIMUM is usually 2 above and below fracture/gap
when using smooth pins, what angle should they be placed to max pin bone interface purchase and increase frame stiffness
70 degrees angle to long axis of bone
optimal diameter of transfixation pins for ESF and placement guidelines from fracture site
SIZE: 20-30% of the diameter of the bonePLACEMENT: no closer than 3 times the pin diameter OR half the diameter of the bone from the fracture or joint edge
T/Fwires tensioned to partial rings, posts or connecting rods should NOT be tensioned more than 30 kg
true
15 principles for proper ESF mgmt
- asepsis2. proper location for insertion of transfixation pin for desired frame construct (tension side of bone, avoid neurovascular structures)3. select the most suitable frame4. consider auxiliary fixation (tie in, cerclage, screws)5. maintain stabilization/reduction during application of frame6. insertion of pins/wires (skin stab first, btwn muscle)7. proper insertion techniques (insert at low speeds 150 rpm; min wobble)8.engage cis and trans cortices9. Smooth pins 70 degrees, positive profile 90 degrees10. SAME PLANE for linear ESF (insert most prix and most distal first for alignment)11. insert implants evenly12. 3-4 pins/fragment ( 2 per frag is MINIMAL)13. optimal size connecting bars, rings14. connecting bar should be at least 1 cm away from skin, clamps IN to decrease working length15.cancellous bone grafts if needed
what is the ideal time to destabilize an ESF to not get an increase in callus but improve bending strength
6 weekstoo early–increase callus, decrease strengthtoo later–no effect on callus or bending strength
what does CORA stand for
center of rotation of angulationdefines an angular limb deformity in relation to the axes of the bone
other than acute fracture management, what are other indications for ESF
- limb salvage surgeries2. transarticular ESF for immobilization/arthrodesis3. ALD (acute correction or DO)4. nonunion fracture/osteomyelitis fracture revision6. spinal luxations
