AO fixation

Question 1

thread diameter : 2.0

Answer 1

core 1.3

Question 2

thread diameter 2.7

Answer 2

core 1.9 ( use 2.0 drill bit)

Question 3

thread diameter 3.5

Answer 3

core: 2.4

Question 4

thread diameter 4.0

Answer 4

core: 1.9

Question 5

What is the distinguishing charachteristic between cortical vs cancellous screws?

Answer 5

Pitch

Question 6

who invented scarf?

Answer 6

Dr Myer

Question 7

Fixation sequence?

Answer 7

underdrill
overdrill
countersink
Measure
Tap
Screw

Question 8

No underdrill

Answer 8

No lag

Question 9

For underdrill the hole is of a diameter ——-than the core ( minor) diameter.

Answer 9

slightly larger

Question 10

another name for Overdrill

Answer 10

Glide hole

Question 11

overdrill drill only to

Answer 11

osteotomy or even less

Question 12

These kinds of screws don’t need over drill?

Answer 12

Partially threaded

Question 13

why countersink?

Answer 13

1. Prevent screw head irritation to ST
2. Prevent stress riser
3. prevent head ( land) from spinning on the cortex

Question 14

When measuring using barrel gauge add — to your final measurement ?

Answer 14

2 mm

Question 15

why do you tap?

Answer 15

create Threads for the screw

Question 16

What size tap do you use for a 2.7 mm screw

Answer 16

same size 2.7 mm

Question 17

what do you do when the head of the screw contacts the bone but you are not getting compression yet?

Answer 17

do 2 finger thightness - use thumb and finger to tighten it down

Question 18

what is PCDO?post calc displacement osteotomy

Answer 18

usually done for flat foot- ( make an ostetomy in the calc) put screw in post aspect of calc and go upward

Question 19

what are you worried about with cannulated screws?

Answer 19

thermal necrosis

Question 20

why do screws fail

Answer 20

1. poor technique
2. Micromotion at the site
3. Axial pullout
4. Bending forces
5. Torque

Question 21

conventional plates are for

Answer 21

Bicortical fixation

Question 22

What physical force holds the plate to the bone

Answer 22

Friction

Question 23

What steps are omitted from application process in conventional plating?

Answer 23

Overdrill and countersink

Question 24

What type of screws are used in conventional plating?

Answer 24

cortical screws

Question 25

Prebending allows

Answer 25

1. Concentric loading of the bone –> distribute forces more equally along the insertion of the plate
2. prevents Gapping of the far cortex

Question 26

Load screw allow for

Answer 26

movement usually about 1mm on either side of the fracture

Question 27

which screws can be utilized as a load screw?

Answer 27

The closest screw on either side of the fracture

Question 28

what is the goal of biologic osteosynthesis

Answer 28

preservation of blood supply, periosteum, and endosteum via minimally invasive plating techniques
Also bone healing occures with bone callus formation.

Question 29

what is stress shielding?

Answer 29

The rigid plate carrying much of the load ( force transmission)

Question 30

What type of loading do you need to improve bone healing?

Answer 30

Axial loading

Question 31

what desighn changes have been made to plates to prevent cancellization of the cortex?

Answer 31

Locking plate

Question 32

Fixed angle osteosynthesis?

Answer 32

The locking plate is not tightly placed against the bone buy instead is locked into the plate a few mms above the bone surface

Question 33

Indication fr the use of lokcing plate?

Answer 33

osteopenic bone
communited fracture
inability to attain anatomicity during fracture reduction

Question 34

Apperence of callus is bad or good

Answer 34

GOOD - A sign of prompt and positive reaction

sign of secondary bone healing