44.ESF

Question 1

unique advantages to ESF

Answer 1

1. adjustment of frame (alignment mods, enhance healing)2. open wound mgmt3. MI approach4. early return to function5. economical

Question 2

linear ESF type Ia

Answer 2

unilateraluniplanar

Question 3

linear ESF type Ib

Answer 3

unilateralbiplanar (90 degrees offset)

Question 4

linear ESF type II

Answer 4

bilateral (180 degrees apart)uniplanar

Question 5

linear ESF III

Answer 5

bilateralbiplanar2 bars are 180 degrees and 3rd is placed at 90 degrees

Question 6

T/Fdouble clamp type I a linear ESF are mechanically inferior (less stiff) than single clamps

Answer 6

TRUEdouble clamps are weaker than single clamps

Question 7

types of transfixation PINs

Answer 7

–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

Question 8

why are negative profile bind subject to high bending moments

Answer 8

negative profile pins have threads cut out of them making their interface a smaller diameter –> stress riser effect–>high bending moment–> implant failure

Question 9

three limitations with KE (kirschner ehmer) clamps

Answer 9

1. 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)

Question 10

SK system stands for

Answer 10

securos external skeletal fixation clamp system

Question 11

advantages to acrylic based ESF

Answer 11

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

Question 12

bending stiffness of tensioned K wires used in ring fixators (circular ESF systems)

Answer 12

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

Question 13

two types of K wires used for ring fixators

Answer 13

1. OLIVE– smooth but with stoppers2. SMOOTH*** generally two wires are used 90 degrees from each other secured to the ring via bolts

Question 14

ideal circular ESF or ring fixators should use how many rings in what technique

Answer 14

4 rings–threaded rods stabilize themtensioned wires with bolts F-N FRACTURE N-F

Question 15

T/FType I b frames have a greater resistance to shear than type II frames

Answer 15

True

Question 16

placing a second bar on a type Ia frame will increase construct stiffness by how much?

Answer 16

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

Question 17

ideal number of pins per fragment to increase ESF frame stiffness and decrease pin-bone interface stress

Answer 17

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

Question 18

when using smooth pins, what angle should they be placed to max pin bone interface purchase and increase frame stiffness

Answer 18

70 degrees angle to long axis of bone

Question 19

optimal diameter of transfixation pins for ESF and placement guidelines from fracture site

Answer 19

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

Question 20

T/Fwires tensioned to partial rings, posts or connecting rods should NOT be tensioned more than 30 kg

Answer 20

true

Question 21

15 principles for proper ESF mgmt

Answer 21

1. 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

Question 22

what is the ideal time to destabilize an ESF to not get an increase in callus but improve bending strength

Answer 22

6 weekstoo early–increase callus, decrease strengthtoo later–no effect on callus or bending strength

Question 23

what does CORA stand for

Answer 23

center of rotation of angulationdefines an angular limb deformity in relation to the axes of the bone

Question 24

other than acute fracture management, what are other indications for ESF

Answer 24

1. limb salvage surgeries2. transarticular ESF for immobilization/arthrodesis3. ALD (acute correction or DO)4. nonunion fracture/osteomyelitis fracture revision6. spinal luxations