Lecture 14 2/13/25

Question 1

What are the forces that act on bone?

Answer 1

-bending
-compression/tension
-torsion

Question 2

How do IM pins neutralize the various forces on bone?

Answer 2

*+++ neutralization of bending
*no neutralization of rotation
*no neutralization of axial compression
*no neutralization of tension

Question 3

How do interlocking nails neutralize the various forces on bone?

Answer 3

*+++ neutralization of bending
*++ neutralization of rotation
*++ neutralization of axial compression
*++ neutralization of tension

Question 4

How do bone plates neutralize the various forces on bone?

Answer 4

*++ neutralization of bending
*+++ neutralization of rotation
*+++ neutralization of axial compression
*+++ neutralization of tension

Question 5

How do ex-fixes neutralize the various forces on bone?

Answer 5

+(++) neutralization of bending, rotation, axial compression, and tension based on configuration and additional components added

Question 6

What are the types of cerclage done?

Answer 6

-full cerclage
-hemi-cerclage
-inter-fragment cerclage
-tension band (most common)

Question 7

What must be done for a cerclage wire to be placed?

Answer 7

must have 360 degree reconstruction of the cylinder of bone at the level the wire is to be placed

Question 8

What are the characteristics of the twist knot method for applying a cerclage wire?

Answer 8

-weakest method
-ends of the wire wrap around each other
-pull up while twisting to tighten the wire

Question 9

What are the characteristics of the loop knot method for applying a cerclage wire?

Answer 9

-uses a special wire type with a loop at one end
-requires a loop wire tightener to apply the wire
-can be applied as a single loop or a double loop
-double loop is the strongest method and only used in large animal

Question 10

Which fractures can a cerclage wire be applied to?

Answer 10

long oblique fractures in which the shaft has been rebuilt with careful technique

Question 11

What are the basic elements of an external fixator?

Answer 11

-fixation pins that attach the device to the bone
-fixation clamps that secure the fixation pins to the rods
-connecting rods that interconnect the fixation pins and span the structure

Question 12

What are the characteristics of an acrylic column ex-fix?

Answer 12

-replaces the clamps and rods
-forms the frame of the ESF device

Question 13

How many fixation pins should be placed for an ex-fix?

Answer 13

three pins in each major fragment

Question 14

What is the far-near-near-far principle of fixation pin insertion?

Answer 14

-reduces the frame working length
-ensures there are not large spans of bone without pins that could increase movement
-want one pin near the fracture site, one pin far from the fracture site, and one pin in between at a minimum

Question 15

How are the fixation pin insertion sites selected?

Answer 15

-selected to minimize the thickness of soft tissue being penetrated
-selected according to “safe corridors” based on tissue thickness, blood supply, etc.

Question 16

What are the characteristics of a type 1a ex-fix?

Answer 16

-unilateral fixator
-half pins
-single plane

Question 17

Identify the ex-fix.

Answer 17

type 1a

Question 18

What are the characteristics of a type 1b ex-fix?

Answer 18

-unilateral fixator
-half pins
-two different planes
-30 to 60 degree angles
-most common in vet med
-can be reinforced with diagonal linkages

Question 19

Identify the ex-fix.

Answer 19

type 1b

Question 20

Identify the ex-fix.

Answer 20

type 1b with diagonal linkage reinforcement

Question 21

What are the characteristics of a type 2 ex-fix?

Answer 21

-bilateral fixator
-full pins
-single plane

Question 22

Identify the ex-fix.

Answer 22

type 2

Question 23

What are the characteristics of a modified type 2 ex-fix?

Answer 23

-combines full pins with half pins
-reduces interference with soft tissue

Question 24

Identify the ex-fix.

Answer 24

modified type 2

Question 25

What are the characteristics of a type 3 ex-fix?

Answer 25

-bilateral fixator -half and full pins -two planes -very rigid -combines a type 2 frontal plane with a type 1 sagittal plane

Question 26

Identify the ex-fix.

Answer 26

type 3

Question 27

What are the characteristics of ex-fix frame stiffness?

Answer 27

increases with number of planes and number of sides

Question 28

What are the characteristics of circular fixators?

Answer 28

-used for fractures and limb deformities -most complex orthopedic implant

Question 29

What are the ring types for circular fixators?

Answer 29

-full ring -half ring -extended ring

Question 30

What are the characteristics of ring placement in a circular fixator?

Answer 30

-use very small pins under a lot of tension -can put pins all over to increase the stability

Question 31

What are the mechanical advantages of interlocking nails?

Answer 31

-intra-medullary location -locking bolts -stability based on locking efficacy

Question 32

What are the benefits of intra-medullary location for the interlocking nails?

Answer 32

-large moment of inertia -near bone neutral axis -counteract bending

Question 33

What forces are counteracted by locking bolts?

Answer 33

-compression -torsion

Question 34

Which fracture types can benefit from interlocking nails?

Answer 34

diaphyseal fractures of the femur, tibia, and humerus

Question 35

What are the biological advantages of interlocking nails?

Answer 35

-nail insertion through remote incisions -preservation of fracture hematoma -preservation of periosteal blood supply -very stable against all forces