Methods of Fracture Fixation

1
Methods of Fracture Fixation
2
What are the forces acting on a fracture after
reduction and fixation?

• Shear
• Torsional/ Rotational
• Bending

3
Which of these forces is most significant for a)
transverse fractures b) oblique fractures c)
comminuted fractures.

• Transverse
• Rotational and bending
• Oblique
• Shear
• Comminuted
• Shear, compressive and torsional

4
When is external coaplation indicated for tx of
limb fractures in dogs and cats?

• When rapid healing is expected
• Immature dogs and cats
• Simple, non-displaced, closed fractures
• When joints above and below fracture can be
  immobilized
• Fractures below elbow or stifle

5
What is an external fixator?

• device for holding fracture in place a steel bar
  that is affixed parallel to a fractured long bone
• Fixator pins are insterted through both cortices
  and secured external to limb with 1, 2 or 3
  connecting bars.

6
What forces does an external fixator counteract?

• All forces

7
What are the limitations on placement of Type II
and Type III external fixators?

• Type 2 fixators can not be placed on the humerus
  or the femur because they cannot be placed
  confortably
• Type 3 ??

8
Why is this method often used for open fractures
and for comminuted fractures?

• Open
• The device is relatively easy to apply and may
  even be adjusted during the fracture site
• Ready access is gained for open wound management
• Comminuted
• ??

9
Why is it not considered a good method for
articular fractures?

• Does not offer stabilization of the joints above
  and below the fracture?????

10
What type of bone healing would you expect with
an external fixator?

• Direct bone healing

11
How can an external fixator be combined with
other methods of fracture fixation?

• Can be combined with cerclage wire, hemicerclage
  wire, IM pin ????????????

12
What are the advantages and disadvantages of
intramedullary pins?

• Can only be used on a stable fracture in small
  dogs and cats and is not adequate for repair of
  femoral fractures in medium and large dogs
• Excellent against bending forces

13
What forces are and are not counteracted by
intramedullary pins?

• Only does bending forces

14
What are indications and contraindications for
intramedullary pins?

• Indications
• Stable fracture
• Small dogs and cats
• Contraindications
• Femoral fractures in large to medium dogs
• Not used in the radius

15
What other methods of fracture fixation may be
used with an IM pin?

• External fixators
• Cerclage and hemicerclage wires

16
Why are such combinations often used with
intramedullary pins?

• Because the IM pins only work against the bending
  forces and thus the addition of other methods of
  stabilization allows for better overall stability
  of the fractured limb

17
What is cerclage wire?

• Stainless steel wire
• 18, 20 and 22 gauge
• Spool or loop

18
What are the guidelines for use of full cerclage
wires?

• Used in areas in which cylinder of bone can be
  reconstructed anatomically
• Auxillary support never used as primary means
  of fracture fixation

19
What is a tension band?

• One or two small pins are inserted through
  fracture fragments into the shaft of bone
• A figure 8 of orthopedic wire is passed through a
  hole drilled into the shaft of bone and twisted
  around the pins

20
In what type of fracture is it used?

• Fractures of the tension physes

21
What is the other use for a tension band?

• May be used to close osteotomy done as part of
  approach to a joint

22
Why does a tension band work only in these
situations?

• Because only in these situations can it convert
  distraction force of a tendon or ligament to
  compressive force.

23
Define dynamic compression plate, compression
plate, neutralization plate, and buttress plate.
What is a veterinary cuttable plate and what are
its advantages?

• Dynamic compression plate self compressing
  screw holes
• Compression plate a type of bone plate in which
  the screws are arranged so that they compress the
  defect and actively promote closure (concept not
  an actual plate).
• Neutralization plate A metal plate used for the
  internal fixation of a long bone fracture to
  neutralize the forces producing displacement
• Buttress plate - A metal plate used to support
  the internal fixation of a fracture.

24
What forces do bone plates counteract?

• All forces

25
Why should a plate span the diaphysis in most
situations?

• Because of the stress riser effect and the
  fractured bone here

26
What complication is associated with leaving a
screw hole in a plate empty?

• Empty holes means there is a weak spot and a
  large dog can break the plate.

27
Why must 6 cortices be engaged on each side of
the fracture?

• There is a high rate of failure associated with
  fewer than 6 cortices, thus put in 6.

28
Explain tension band plating.

• Tension band plate is placed on tension side of
  weight bearing bone
• Converts distraction (tension) forces to dynamic
  compression forces with weight bearing.

29
What are the tension sides of the femur, tibia,
humerus and radius?

• Femur craniolateral
• Tibia craniolateral
• Humerus varies with location of fracture
• Radius cranial

30
Where are bone plates placed on each of these
bones?

• Femur lateral
• Tibia medial
• Humerus cranial, medial, lateral or caudal
• Radius cranial

31
What type of plate would you apply to a
transverse fracture of the femur?

• Compressive

32
What type of bone healing would you expect?

• Direct- contact

33
What type of plate would you apply to a
comminuted fracture of the femur?

• Neutralization plate with lag screws or a buttress

34
What type of bone healing would you expect?

• Indirect for both depending if you use lag screws
  (direct)

35
Describe the two types of bone screws

• Cortical
• Fully threaded, fine pitch
• Used in cortical or cancellous bone
• Cancellous
• Fully or partially threaded, coarse pitch
• Used in cancellous bone

36
Describe lag screw fixation and positions screw
fixation.

• Gliding hole, equal to diameter of screw threads,
  is drilled in near cortex
• Thread hole, equal to diameter of screw core, is
  drilled in far cortex and tapped
• As screw engages far cortex, compression occurs
  across fracture line
• Hole should be drilled so that it bisects angle
  between perpendicular to axis of bone and
  perpendicular to fracture line

37
If you use 2 lag screws to fix a butterfly
fragment to the main fracture fragments, and you
then apply a bone plate, what type of plating
have you done?

• Neutralization plate?

38
What is an advantage of an interlocking nail over
a bone plate in resisting bending?

• Neutral axis of the bone, plate is on one cortex.

39
How, in general terms, is an interlocking nail
placed in the bone?

• Select nail of appropriate length, attach
  extension device to end of nail, use insertion
  tool to place nail into bone. Use drill guide
  jig for hole placement and place distal screws
  first

40
When would a nail be contraindicated?

• When there is no intact cortex proximal or distal
  to the fracture

41
Nails, like IM pins, should not be retrograde in
in the tibia. Why?

• No way to get there without going through the
  joint and metal in a joint is a bad thing!

42
What is the fracture assessment score?

• Scoring system used to reflect high to low risk
  of failure of repair

43
Give examples of mechanical factors, biologic
factors and clinical factors that are used to
develop a fracture assessment score for a
patient.

• Mechanical
• of injured limbs, patient size activity,
  degree of load sharing
• Biological
• Age health, open vs. closed, open vs closed
  reduction surgeons skill, low vs. high energy,
  specific bone injured fx location
• Clinical
• Patient compliance, owner compliance, patient
  comfort and pain tolerance

44
Describe the requirements for implants for
fractures with scores of 0-3, 4-7 and 8-10.

• 0-3 lenghtneing plate, plate-fixator
  combination, plate-rod combination, fixator-pin
  combination with tie in, type II, type III
  fixator
• 4-7 bone plate, type I/type II fixator,
  fixator-pin combiation with/without tie-in, pin
  plus cerclage
• 8-10 type I fixator (smooth pins), pin plus
  cerclage, external coaptation

45
Give an example of a suitable method of fixation
for each of these groups.

• 0-3 implant must bridge fracture and be strong
  enough to prevent bending or breaking as well as
  excess motion at fracture
• 4-7 intermediate load sharing and healing time
• 8-10 immediate load sharing, so do not need very
  strong or stiff implant implant does not need to
  function for prolonged time