The document discusses AO principles of fracture treatment and different implant modalities. It covers the AO classification system, the four AO principles of fracture fixation focusing on restoration of anatomy and stability, methods of fracture reduction, types of fracture fixation including absolute and relative stability, importance of preserving blood supply, and postoperative care including early mobilization. Key implant modalities discussed include screws for cortical and cancellous bone as well as lag screw fixation.

1. AO Principles Of FractureAO Principles Of Fracture
Treatment And DifferentTreatment And Different
Implant ModalitiesImplant Modalities
Dr. Anshu sharmaDr. Anshu sharma

2. AO System Of ClassificationAO System Of Classification
 AO Classification is based on theAO Classification is based on the
Type of involved bone (no. 1 to 9),Type of involved bone (no. 1 to 9),
Part of involved bone (no. 1 to 3),Part of involved bone (no. 1 to 3),
Fracture is extraarticular, partiallyFracture is extraarticular, partially
articular or intraarticular ( A,B or C),articular or intraarticular ( A,B or C),
Pattern of fracture (1 to 3).Pattern of fracture (1 to 3).

4. AO PrinciplesAO Principles
 The four AO principles of fracture fixation are:-The four AO principles of fracture fixation are:-
1. Fracture reduction to restore anatomical1. Fracture reduction to restore anatomical
relationships.relationships.
2. Fracture fixation providing absolute or relative2. Fracture fixation providing absolute or relative
stability as the “personality” of fracture, patient andstability as the “personality” of fracture, patient and
injury requires.injury requires.
3. Preservation of blood supply to soft tissues and3. Preservation of blood supply to soft tissues and
bone.bone.
4. Early and safe mobilization of the injured part and4. Early and safe mobilization of the injured part and
the patient as a whole.the patient as a whole.

5. Fracture ReductionFracture Reduction
 Aim of reductionAim of reduction
Some fractures are reduced to restoreSome fractures are reduced to restore
1. The bony anatomy and morphology, when perfect1. The bony anatomy and morphology, when perfect
anatomical reductionanatomical reduction is required.is required.
2. The relationship between the proximal and distal main2. The relationship between the proximal and distal main
fragments. Length, alignment and rotation are restored.fragments. Length, alignment and rotation are restored.
This isThis is functional reductionfunctional reduction..
 Reduction methodsReduction methods
The decision, which reduction method should be used,The decision, which reduction method should be used,
depends on the location of the fracture:depends on the location of the fracture:
1. Meta- and diaphyseal fractures usually need1. Meta- and diaphyseal fractures usually need
functional reduction.functional reduction.
2. Joint fractures need anatomical reduction.2. Joint fractures need anatomical reduction.

6. Reduction of diaphyseal fracturesReduction of diaphyseal fractures
•• The functional anatomy is restored (length, alignment,The functional anatomy is restored (length, alignment,
and rotational axis).and rotational axis).
•• The load-bearing axis of the extremity is restoredThe load-bearing axis of the extremity is restored
(especially important in the lower limb).(especially important in the lower limb).
•• An exception is the forearm which functions as a singleAn exception is the forearm which functions as a single
articular unit.articular unit.
Reduction of articular fracturesReduction of articular fractures
•• The joint surface is restored anatomically.Gaps and stepsThe joint surface is restored anatomically.Gaps and steps
in the articular surface must be avoided.in the articular surface must be avoided.
 ““Steps” means that there is a difference between theSteps” means that there is a difference between the
levels of two main articular fragments.levels of two main articular fragments.
 ““Gaps” means that there is some space between twoGaps” means that there is some space between two
adjacent main articular fragments.adjacent main articular fragments.
 The axial alignment is restored.The axial alignment is restored.

7. Fracture FixationFracture Fixation
 Goal of fracture fixationGoal of fracture fixation
1. To maintain the reduction1. To maintain the reduction
2. To create adequate stability which:2. To create adequate stability which:
-Allows early and optimal function of the injured limb,-Allows early and optimal function of the injured limb,
-Minimizes pain.-Minimizes pain.
 The main goal of internal fixation is to achieve promptThe main goal of internal fixation is to achieve prompt
and, if possible, full function of the injured limb. Althoughand, if possible, full function of the injured limb. Although
reliable fracture healing is only one element in functionalreliable fracture healing is only one element in functional
recovery, its mechanics, biomechanics, and biology arerecovery, its mechanics, biomechanics, and biology are
essential for a good outcome.essential for a good outcome.

8.  Absolute stabilityAbsolute stability
•• There is no movement at fracture site.There is no movement at fracture site.
•• It is achieved by interfragmentary compression,It is achieved by interfragmentary compression,
eg. lag screws, compression plate.eg. lag screws, compression plate.
•• There is no callus formation.Direct bone healingThere is no callus formation.Direct bone healing
is achieved.is achieved.

9.  Relative stabilityRelative stability
•• Movement at fracture siteMovement at fracture site
•• There is no interfragmentaryThere is no interfragmentary
compression at fracturecompression at fracture
site.It is achieved by splintingsite.It is achieved by splinting
or bridging, eg. elastic nailsor bridging, eg. elastic nails
•• There is callus formation.There is callus formation.
Indirect bone healing isIndirect bone healing is
achieved.achieved.

10. Absolute
(Rigid)
Relative
(Flexible)
Spectrum of Stability
Cast
IM Nail
Compression
Plating/ Lag
screw
Ex Fix
Bridge Plating

11. Practically speaking….Practically speaking….
 Most fixation probably involvesMost fixation probably involves
components of both types of healing.components of both types of healing.
 Even in situations of excellent rigid internalEven in situations of excellent rigid internal
fixation one often sees a small degree offixation one often sees a small degree of
callus formation.callus formation.

12. Relative
(Rigid)
Absolute
(Flexible)
No
callus
Fixation Stability
Callus
Reality

13. Preservation Of Blood SupplyPreservation Of Blood Supply
Care for the soft tissuesCare for the soft tissues
•• Evaluation of limb swelling.Evaluation of limb swelling.
•• Consideration for staged procedure is important:Consideration for staged procedure is important:
- Primary stabilization → external fixation.- Primary stabilization → external fixation.
- Secondary stabilization → definitive fixation.- Secondary stabilization → definitive fixation.
•• Careful reduction procedureCareful reduction procedure
-Too intense efforts for perfect reduction are-Too intense efforts for perfect reduction are
risky and Increases infection rate.risky and Increases infection rate.
•• Minimal invasive surgery.Minimal invasive surgery.
•• Good Nursing care of patient with fractures and CareGood Nursing care of patient with fractures and Care
during transfer and positioning.during transfer and positioning.

14. Postoperative carePostoperative care
•• Immediately after surgery,the treated extremity isImmediately after surgery,the treated extremity is
positioned above the level of the heart to minimizepositioned above the level of the heart to minimize
swelling.swelling.
 Adequate pain control.Adequate pain control.
 Thrombosis prophylaxis.Thrombosis prophylaxis.
 Early recognition and treatment of complications.Early recognition and treatment of complications.

15.  Early joint motion: CPM (continuous passive motion) machines areEarly joint motion: CPM (continuous passive motion) machines are
used to provide a continuous but passive (without force of theused to provide a continuous but passive (without force of the
patient) motion for limbs where after surgery (knee or elbow)patient) motion for limbs where after surgery (knee or elbow)
stiffness of the limb might be expected.stiffness of the limb might be expected.
 Partial weight bearing and gradually full weight bearing.Partial weight bearing and gradually full weight bearing.
 During follow-up treatment, not only look at the xrays but also at theDuring follow-up treatment, not only look at the xrays but also at the
injured limb. Pain, swelling, and tenderness are signs of eitherinjured limb. Pain, swelling, and tenderness are signs of either
instability or infection.instability or infection.

16. Indications for Internal FixationIndications for Internal Fixation
 Displaced intra-articular fracture,Displaced intra-articular fracture,
 Axial, angular, or rotational instability thatAxial, angular, or rotational instability that
cannot be controlled by closed methods,cannot be controlled by closed methods,
 Open fracture,Open fracture,
 Polytrauma patients,Polytrauma patients,
 Associated neurovascular injury.Associated neurovascular injury.

17. Benefits of Internal FixationBenefits of Internal Fixation
 Earlier functional recovery,Earlier functional recovery,
 More predictable fracture alignment,More predictable fracture alignment,
 Potentially faster time to healing.Potentially faster time to healing.

18. Screws
• Cortical screws:
-Greater number of threads
-Threads spaced closer together
(smaller pitch)
-Outer thread diameter to core diameter
ratio is less
-Better hold in cortical bone.
• Cancellous screws:
-Larger thread to core diameter ratio
-Threads are spaced farther apart
(greater pitch)
-Lag effect with partially-threaded
screws
-Theoretically allows better fixation in
cancellous bone Figure from: Rockwood and Green’s, 5th
ed.

19. Lag Screw FixationLag Screw Fixation
 Screw compresses bothScrew compresses both
sides of fx togethersides of fx together
 Best form of compressionBest form of compression
 Poor shear, bending, andPoor shear, bending, and
rotational force resistancerotational force resistance
 Partially-threaded screwPartially-threaded screw
(lag by design)(lag by design)
 Fully-threaded screw (lagFully-threaded screw (lag
by technique)by technique)

20. 1
2
Figure from: Schatzker J, Tile M: The Rationale of
Operative Fracture Care. Springer-Verlag, 1987.
Lag Screws
• “Lag by technique”
• Using fully-threaded
screw
• Step One: Gliding hole =
drill outer thread diameter of
screw & perpendicular to fx.
• Step Two: Pilot hole= Guide
sleeve in gliding hole & drill
far cortex = to the core
diameter of the screw.

21. Lag ScrewsLag Screws
 Step Three: counter sinkStep Three: counter sink
near cortex so screw headnear cortex so screw head
will sit flushwill sit flush
 Step Four: screw insertedStep Four: screw inserted
and glides through the nearand glides through the near
cortex & engages the farcortex & engages the far
cortex which compressescortex which compresses
the fx when the screw headthe fx when the screw head
engages the near cortexengages the near cortex
Figure from: Schatzker J, Tile M: The
Rationale of Operative Fracture Care.
Springer-Verlag, 1987.

22. Lag ScrewsLag Screws
 Functional LagFunctional Lag
Screw - note theScrew - note the
near cortex hasnear cortex has
been drilled to thebeen drilled to the
outer diameter =outer diameter =
compressioncompression
 Position Screw -Position Screw -
note the near cortexnote the near cortex
has not been drilledhas not been drilled
to the outerto the outer
diameter = lack ofdiameter = lack of
compression & fxcompression & fx
gap maintainedgap maintained

23. Figure from: OTA Resident Course - Olsen
Lag Screws
• Malposition of screw, or neglecting to
countersink can lead to a loss of reduction
• Ideally lag screw should pass perpendicular to fx

24. Neutralization PlatesNeutralization Plates
 Neutralizes/protectNeutralizes/protect
s lag screws froms lag screws from
shear, bending,shear, bending,
and torsional forcesand torsional forces
across fxacross fx
 ““Protection Plate"Protection Plate"
Figure from: Schatzker J, Tile M: The Rationale of
Operative Fracture Care. Springer-Verlag, 1987.

25. Buttress / Antiglide PlatesButtress / Antiglide Plates
 ““Hold” the bone up.Hold” the bone up.
 Resist shear forcesResist shear forces
during axial loading.during axial loading.
 Used in metaphysealUsed in metaphyseal
areas to support intra-areas to support intra-
articular fragments.articular fragments.
 Plate must matchPlate must match
contour of bone to trulycontour of bone to truly
provide buttress effect.provide buttress effect.

26. Bridge PlatesBridge Plates
 ““Bridge”/bypassBridge”/bypass
comminution.comminution.
 Proximal & distalProximal & distal
fixation.fixation.
 Goal: Maintain length,Goal: Maintain length,
rotation, & axialrotation, & axial
alignmentalignment
 Avoids soft tissueAvoids soft tissue
disruption at fx todisruption at fx to
maintain fx bloodmaintain fx blood
supply.supply.

27. Tension Band PlatesTension Band Plates
 Plate counteracts naturalPlate counteracts natural
bending moment seen withbending moment seen with
physiologic loading ofphysiologic loading of
bonebone
 Applied to tension side toApplied to tension side to
prevent “gapping”.prevent “gapping”.
 Plate converts bending forcePlate converts bending force
to compression.to compression.
 Examples: Proximal FemurExamples: Proximal Femur
& Olecranon.& Olecranon.

28. Compression PlatingCompression Plating
 Reduce & CompressReduce & Compress
transverse or obliquetransverse or oblique
fx’s.fx’s.
 Unable to use lagUnable to use lag
screwscrew
 Exert compressionExert compression
across fractureacross fracture
 Pre-bending platePre-bending plate
 External compressionExternal compression
devices (tensioner)devices (tensioner)
 Dynamic compressionDynamic compression
w/ oval holes &w/ oval holes &
eccentric screweccentric screw
placement in plateplacement in plate

29. Examples- 3.5 mm PlatesExamples- 3.5 mm Plates
 LC-DynamicLC-Dynamic
Compression PlateCompression Plate::
 stronger and stifferstronger and stiffer
 more difficult to contour.more difficult to contour.
 usually used in theusually used in the
treatment radius and ulnatreatment radius and ulna
fracturesfractures
 Semitubular plates:Semitubular plates:
 very pliablevery pliable
 limited strengthlimited strength
 most often used in themost often used in the
treatment of fibulatreatment of fibula
fractures.fractures.
Figure from: Rockwood and Green’s, 5th
ed.
Figure from: Rockwood and Green’s, 5th
ed.

30. Dynamic Compression PlatingDynamic Compression Plating
 Compression appliedCompression applied
via oval holes andvia oval holes and
eccentric drillingeccentric drilling
 Plate forces bone toPlate forces bone to
move as screwmove as screw
tightened =tightened =
compressioncompression

31. Dynamic Compression Plates
• Note the screw holes in the
plate have a slope built into
one side.
• The drill hole can be purposely
placed eccentrically so that when
the head of the screw engages the
plate, the screw and the bone
beneath are driven or compressed
towards the fracture site one
millimeter.
This maneuver can be
performed twice before
compression is maximized.
Figure from: Schatzker J, Tile M: The Rationale of
Operative Fracture Care. Springer-Verlag, 1987.

32. Locking PlatesLocking Plates
 Screw head has threadsScrew head has threads
that lock into threadedthat lock into threaded
hole in the platehole in the plate
 Creates a “fixed angle” atCreates a “fixed angle” at
each holeeach hole
 Theoretically eliminatesTheoretically eliminates
individual screw failureindividual screw failure
 Plate-bone contact notPlate-bone contact not
criticalcritical Courtesy AO Archives

33. Locking PlatesLocking Plates
 Must have reduction and compressionMust have reduction and compression
done prior to using locking screwsdone prior to using locking screws
 CANNOT PUT CORTICAL SCREW OR LAGCANNOT PUT CORTICAL SCREW OR LAG
SCREW AFTER LOCKING SCREWSCREW AFTER LOCKING SCREW

34. Locking PlatesLocking Plates
 Increased axialIncreased axial
stabilitystability
 It is much lessIt is much less
likely that anlikely that an
individual screwindividual screw
will failwill fail
 But, plates canBut, plates can
still breakstill break

35. Locking PlatesLocking Plates
 Indications:Indications:
 Osteopenic boneOsteopenic bone
 MetaphysealMetaphyseal
fractures with shortfractures with short
articular blockarticular block
 Bridge platingBridge plating

36. Intramedullary NailsIntramedullary Nails
 Relative stabilityRelative stability
 Intramedullary splintIntramedullary splint
 Less likely to break withLess likely to break with
repetitive loading thanrepetitive loading than
plateplate
 More likely to be loadMore likely to be load
sharing (i.e. allow axialsharing (i.e. allow axial
loading of fracture withloading of fracture with
weight bearing).weight bearing).
 Secondary bone healingSecondary bone healing
 Diaphyseal and someDiaphyseal and some
metaphyseal fracturesmetaphyseal fractures

37. Intramedullary FixationIntramedullary Fixation
 Rotational and axialRotational and axial
stability provided bystability provided by
interlocking bolts.interlocking bolts.
 Reduction can beReduction can be
technically difficult intechnically difficult in
segmental andsegmental and
comminutedcomminuted
fractures.fractures.
 Maintaining reductionMaintaining reduction
of fractures in closeof fractures in close
proximity toproximity to
metaphyseal flaremetaphyseal flare
may be difficult.may be difficult.

38. • Open segmental
tibia fracture treated
with a reamed,
locked IM Nail.

39. • Intertrochanteric/
Subtrochanteric fracture
treated with closed IM
Nail
• The goal:
• Restore length,
alignment, and
rotation
• NOT anatomic
reduction
• Without extensive
exposure this fracture
formed abundant callus
by 6 weeks
Valgus is restored...

40. •Classic example of
inadequate fixation &
stability
•Narrow, weak plate that is
too short
•Insufficient cortices engaged
with screws through plate
•Gaps left at the fx site
Unavoidable result =
Nonunion Figure from: Schatzker J, Tile M: The Rationale of
Operative Fracture Care. Springer-Verlag, 1987.
Failure to Apply Concepts

41. SummarySummary
 Respect soft tissues.Respect soft tissues.
 Choose appropriate fixation method.Choose appropriate fixation method.
 Achieve length, alignment, andAchieve length, alignment, and
rotational control to permit motion asrotational control to permit motion as
soon as possible.soon as possible.
 Understand the requirements andUnderstand the requirements and
limitations of each method of internallimitations of each method of internal
fixation.fixation.