Title: Methods of Fracture Fixation
1Methods of Fracture Fixation
2What are the forces acting on a fracture after
reduction and fixation?
- Shear
- Torsional/ Rotational
- Bending
3Which 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
4When 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
5What 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.
6What forces does an external fixator counteract?
7What 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 ??
8Why 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
- ??
9Why is it not considered a good method for
articular fractures?
- Does not offer stabilization of the joints above
and below the fracture?????
10What type of bone healing would you expect with
an external fixator?
11How can an external fixator be combined with
other methods of fracture fixation?
- Can be combined with cerclage wire, hemicerclage
wire, IM pin ????????????
12What 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
13What forces are and are not counteracted by
intramedullary pins?
14What 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
15What other methods of fracture fixation may be
used with an IM pin?
- External fixators
- Cerclage and hemicerclage wires
16Why 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
17What is cerclage wire?
- Stainless steel wire
- 18, 20 and 22 gauge
- Spool or loop
18What 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
19What 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
20In what type of fracture is it used?
- Fractures of the tension physes
21What is the other use for a tension band?
- May be used to close osteotomy done as part of
approach to a joint
22Why 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.
23Define 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.
24What forces do bone plates counteract?
25Why should a plate span the diaphysis in most
situations?
- Because of the stress riser effect and the
fractured bone here
26What 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.
27Why 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.
28Explain 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.
29What are the tension sides of the femur, tibia,
humerus and radius?
- Femur craniolateral
- Tibia craniolateral
- Humerus varies with location of fracture
- Radius cranial
30Where are bone plates placed on each of these
bones?
- Femur lateral
- Tibia medial
- Humerus cranial, medial, lateral or caudal
- Radius cranial
31What type of plate would you apply to a
transverse fracture of the femur?
32What type of bone healing would you expect?
33What type of plate would you apply to a
comminuted fracture of the femur?
- Neutralization plate with lag screws or a buttress
34What type of bone healing would you expect?
- Indirect for both depending if you use lag screws
(direct)
35Describe 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
36Describe 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
37If 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?
38What is an advantage of an interlocking nail over
a bone plate in resisting bending?
- Neutral axis of the bone, plate is on one cortex.
39How, 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
40When would a nail be contraindicated?
- When there is no intact cortex proximal or distal
to the fracture
41Nails, 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!
42What is the fracture assessment score?
- Scoring system used to reflect high to low risk
of failure of repair
43Give 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
44Describe 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
45Give 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