Internal fixation: pins, wires and interlocking nails

Question 1

When is internal fixation warranted?

Answer 1

when external coaptation can’t be use or has distinct disadvantages

Question 2

What bones should internal fixation always be used?

Answer 2

humerus and femur

Question 3

What kind of fractures should usually be fixed by internal fixation?

Answer 3

1. oblique

2. comminuted

Question 4

What do intramedullar pins control?

Answer 4

bending. but need help for controlling others

Question 5

What do interlocking nails, external skeletal fixators and bone plates control?

Answer 5

all the forces that act on the fracture if the correct hardware/configuration is used

Question 6

What is internal fixation?

Answer 6

fracture repair by means of hardware that attaches directly to the bone

Question 7

What are fractures for which internal fixation is much better than external coaptation?

Answer 7

1. open fractures
2. fractures of femur, humerus, pelvis
3. articular fractures–perfect reduction–early joint movement
4. oblique or comminuted fractures–control commpresion
5. fractures in which primary force acting is tension–olecranon, calcaneus, greater trochanter

Question 8

What forces to intramedullar pins control?

Answer 8

bending

Question 9

What is an intramedullary pin

Answer 9

a rod that stabilizes broken bone by passing longitudinally within medullary canal, v/ close to neutral axis

Question 10

what is a K-wire

Answer 10

A small pin

Question 11

What are 4 advantages of intramedullary pins

Answer 11

1. availability
2. axial alignment
3. bending control
4. minimal to moderate blood supply disruption

Question 12

What are 4 advantages of intramedullary pins

Answer 12

1. availability
2. axial alignment
3. bending control
4. minimal to moderate blood supply disruption

Question 13

What are 4 disadvantages of intramedullary pins?

Answer 13

1. pins control only bending
2. can’t always anatomically repair comminuted fractures
3. potential for injury to surrounding structures–sciatic nerve
4. not good for skull, pelvis. RADIUS

Question 14

What are two ways to place an IM pin

Answer 14

1. normograde placement-

2. retrograde placement

Question 15

What is normograde placement?

Answer 15

reduction of fracture then pin run down middle–for tibia, often ulna, humerus

Question 16

What is retrograde placement?

Answer 16

pin inserted in the proximal fragment, then pull out proximal end. –easier to get in canal. NOT tibia. usually in femor

Question 17

What is retrograde placement?

Answer 17

pin inserted in the proximal fragment, then pull out proximal end. –easier to get in canal. NOT tibia. usually in femor

Question 18

What should the diameter of an IM pin be?

Answer 18

60% the diameter of the medullary canal at skinniest point of the bone–still allows blood supply UNLESS combined with bone plate or external fixation (50% then)

Question 19

How should the IM pin be positioned?

Answer 19

run the length of the bone and spear the cortex at the bottom but do not penetrate it

Question 20

What is cross-pinning?

Answer 20

NOT Im pins. The pins are placed so they cross the fracture line and two cortices

Question 21

What are forces neutralized by cross pins?

Answer 21

1. torsion
2. compression
3. moderate bending

Question 22

When is cross pinning appropriate?

Answer 22

for repairing physeal or very distal/proximal metaphyseal fractures

Question 23

What are wiring techniques used for?

Answer 23

1. prevent propagation of fissues
2. reconstruct fragments
3. hold fracture in reduction until definitive repair
4. help control torsion and compressive along with IM pin

Question 24

What is a full cerclage?

Answer 24

the passing wire around the circumference of bone to stabilize a fracture

Question 25

What is the only appropriate use of full cerclage?

Answer 25

for use in long oblique fractures. the cylinder of bone must be reconstructed! and must be TIGHT

Question 26

Why must full cerclage wires be tight?

Answer 26

because if they wiggle they distrupt blood supply to the fracture --thus MUST be perpendicular to bone and not on tapering areas unless anchored

Question 27

What is interfragmentary wiring?

Answer 27

placing wires through two bone fragments to connect them

Question 28

Where can interfragmentary wiring be used?

Answer 28

transverse, short and long oblique fractures. can also use with cross pins/skewer pins

Question 29

Where can interfragmentary wiring be used?

Answer 29

transverse, short and long oblique fractures. can also use with cross pins/skewer pins

Question 30

What is tension band wiring?

Answer 30

It is wiring to counteract tensile force. it transforms bad tensile forces into good compressive forces. Parallel pins are placed perpendicular to the fracture line. A figure of 8 wire is passed through a distal hole and around the pins and tightened

Question 31

What is an interlocking nail?

Answer 31

a rode placed in the medullary canal and fixed in place with scews or bolts that pass from the outside of the bone, through holes in rod and back through cortex usually left in place

Question 32

What forces do interlocking nails control?

Answer 32

1. bending! 2. compression (scews) 3. torsion (screws)

Question 33

What are the advantages of interlocking nail?

Answer 33

1. can fix comminuted fractures without requiring anatomic reconstruction 2. less disruptive than plate placement so only moderately disrupts blood supply 3. cheaper than bone plate

Question 34

What are the limitations of interlocking nail?

Answer 34

1. need a bone protrusion to introduce into the bone: femur, humerus, tibia NOT RADIUS 2. require a box of special equipment 3. big learning curve

Question 35

What is an IM ESF tie-in

Answer 35

leave IM pin protruding. pass transfixation pin and external fixating bar (tie-in) IM, external skeletal fixator

Question 36

What is a plate-pin combination?

Answer 36

have a pin AND a bone plate gives superior bending control--can also drop IM pin diameter to 50% and only need 1 screw per fragment going all the way across

Question 37

What is a plate-pin combination?

Answer 37

have a pin AND a bone plate gives superior bending control--can also drop IM pin diameter to 50% and only need 1 screw per fragment going all the way across. For the skinny diaphyseal parts just need to go into one cortex