Principles of open reduction and internal fixation

Question 1

Goal of ORIF

Answer 1

1-restore functional anatomic relationships
2-acheive stable fixation
3-preserve blood supply to the bone and soft tissue
4-allow early and safe mobilization

Question 2

fracture repair is a balancing act between…

Answer 2

enough and too much stability and how fast a bone heals and how soon a chosen implant will fail

Question 3

fracture repair biology

Answer 3

trauma sustained results indisruption of endosteal and periosteal blood supply. maintaining an adequate blood supply is essential for healing

Question 4

four classic stages of bone healing

Answer 4

inflammation, soft callus, hard callus, and remodeling

Question 5

Biologic Fixation

Answer 5

attempts fixation with minimal violation of the fracture envelope and maximum preservation of soft tissue and blood supply to the fracture site. (open but do not touch)

Question 6

Anatomic fixation

Answer 6

perfectly reconstruct the bone through reduction, rigid fixation and compression across a fracture promoting primary bone healing.
Requires excessive dissection and disruption of the soft tissue and blood supply to the fracture site

Question 7

compression forces

Answer 7

force directed along long axis of the bone. If not neutralized, results in axial shortening of the bone

Question 8

bending force

Answer 8

force focused at a specific point on the bone (ie the fracture site) If not neutralized, results in sharp angulation of the bone at the fracture site

Question 9

torsion force

Answer 9

a twisting force along long axis of the bone. If not neutralized results in rotation of the fracture fragments

Question 10

shear force

Answer 10

force directed parallel to the plane of the fracture (ie compression along and oblique fracture). If not neutralized, results in fracture fragments sliding against each other

Question 11

tension forces

Answer 11

forces applied to bone via forceful muscular shortening (ie avulsion fractures). If not neutralized results in distraction of the bone prominence and contracture of the muscle involved.

Question 12

Kirschner wires

Answer 12

small gauge, smooth or theaded, trocar or chisel tipped pins that are used primarily as provisional implants)
most commonly used in conjunction with other implants but may be the sole means of fixation for small fragments or epiphyseal/metaphyseal fractures
capable of counteracting BENDING and ROTATIONAL forces (if used in multiples)

Question 13

Steinmann pins

Answer 13

larger gauge smooth or threaded, trocar or chisel tipped pins.
typically use smooth steinmann pins for IM pinning while threaded pins are used for external fixators
Counteract against BENDING

Question 14

IM pins

Answer 14

if sole implant for couteracting bending the pin should fill greater than 70% of the diameter of the medullary cavity at its narrowest point
If pin is an adjunct impland for bending then it should fill 30-40% medullary cavity
NEVER use as sole means of fixation because weak when it comes to rotation and compression

Question 15

bones that IM pin can be used in

Answer 15

any bone with safe access point to medullary cavity including humerus, ulna, femur, tibia.
NEVER PIN A RADIUS
NEVER PIN THRU ARTICULAR SURFACE

Question 16

orthopedic wire

Answer 16

stainless steel, monofilament of varying size and can be used as an adjunct device.

Question 17

methods of orthopedic wire placement

Answer 17

cerclage, hemi-cerclage, tension band, interfragmentary wire.
most common uses are cerclage and tension band

Question 18

Cerclage wire

Answer 18

used to encircle bone to hold fragments together

very little resistance to bending

Question 19

rules of cerclage wire

Answer 19

1-fracture should be simple (2-3 pieces), long oblique
2-fracture must be anatomically reduced
3-minimum of 2 wires
4-space wires 1 cm apart and at least 0.5cm from fracture end
5- avoid soft tissue entrapment
6-must be tight
7- place perpendicular to the long axis of the bone
8-wire should be 18g or 20g in diameter
9-using twist cerclage: leave 3 twists to secure the wire and apply twist under tension
NEVER USE AS SOLE MEANS OF FIXATION

Question 20

Interlocking nails

Answer 20

use the bending strength of an IM pin and add the ability to neutralize in compression and torsion
can be used on humerus, femur and tibia (require enough bone stock proximally and distally to accomodate the bolts)
Mid-diaphyseal fractures work best

Question 21

screws

Answer 21

rarely used without bone plate

can be used alone or in conjunction with other implants

Question 22

four parts of screw

Answer 22

Head=top of screw
Shaft=core and diameter determines the size of drill bit used to place screw
Thread=inclined plane wrapped around shaft responsible for engaging bone
Tip=rounded(require tapping) or fluted(self tapping)

Question 23

Interfragmentary screws

Answer 23

used in isolation are placed as lag screws to compress two fragments together or as positional screws to hold two fragments in a neutral relationship

Question 24

screw as primary means against shear

Answer 24

screw diameter should be larger (40-50%) compared to the bone fragment

Question 25

screws used in conjunction with a plate

Answer 25

should have a diameter 25-30% the diameter of the diaphysis

Question 26

Plates

Answer 26

placed as neutralization plates, compression plates, or bridging(buttress) plates

Question 27

neutralization plating is used

Answer 27

when needed to neutralize axial forces across a fracture in order to protect interfragmentary fixation i.e the fracture is reduced using lag screws and a neutralization plate is used to span bone, protecting lag screws

Question 28

compression plate

Answer 28

used when anatomic reduction and interfragmentary compression are acheiveable and the desired goal of absolute stability to allow primary bone healing

Question 29

bridging/buttress plate

Answer 29

used for comminuted, unstable fractures for which anatomic restoration and absolute stability are not possible plate is used to attach two main bone fragments ,provide length, axial alignment and rotation.

Question 30

where should bone plates be placed

Answer 30

when possible plates should be placed on the tension surface of the bone this allows us to take advantage of the tension band effect which converts tension forces to compressive forces at the fracture site

Question 31

plating on compression surface

Answer 31

only when necessary | resistance to bending is significantly compromised

Question 32

Dynamic compression plate(DCP)/limited contact dynamic compression plate

Answer 32

used in neutral, compression or bridging designed with an oval hole to allow for neutral or eccentric placement of the screw

Question 33

eccentric screw head placement

Answer 33

results in plate shifting in relation to the bone

Question 34

limited contact dynamic compression plates

Answer 34

differ from dynamic compression plates by their scalloped design which theoretically allows for preservation of periosteal vascularity and improved cortical profusion.

Question 35

Locking compression plate

Answer 35

accepts conventional and locking screws allows screws and plate to become one construct (internal fixator) less reliant on perfect contouring

Question 36

String of pearl plate

Answer 36

locking system designed to be used with cortical screws screw threads engage the plate nodes SOPs can be contoursed with six degrees of freedom

Question 37

veterinary cuttable plates

Answer 37

thin, lightweight plates | close inter-hole distance useful with shorter fragments, can stack plates and customize length

Question 38

Principles of bone plating

Answer 38

1-minimum of 6 cortices per segment (conventional/plate alone) 2-minimum of for cortices per segment (locking plate/plate+ rod) 3-screws at least 5mm from fracture (1.5x diameter of screw) 4-avoid penetrating fracture site 5-avoid penetrating or crossing open physis 6-avoid penetrating articular surfaces 7-plate should be perfectly contoured (if not locking) to avoid displacement of fragments