AO Principles of Fracture treatment & Different Implants

AO Principles Of Fracture AO Principles Of Fracture Treatment And Different Treatment And Different

Implant ModalitiesImplant Modalities

Dr. Anshu sharmaDr. Anshu sharma

AO System Of ClassificationAO System Of Classification

AO Classification is based on the AO 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).

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.

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 perfect 1. The bony anatomy and morphology, when perfect

anatomical reduction anatomical reduction is required.is required. 2. The relationship between the proximal and distal main 2. The relationship between the proximal and distal main

fragments. Length, alignment and rotation are restored. fragments. Length, alignment and rotation are restored. This is This 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 need 1. Meta- and diaphyseal fractures usually need

functional reduction.functional reduction. 2. Joint fractures need anatomical reduction.2. Joint fractures need anatomical reduction.

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 restored The 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 single An exception is the forearm which functions as a single

articular unit.articular unit.

Reduction of art icular fracturesReduction of art icular fractures • • The joint surface is restored anatomically.Gaps and steps The 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 the Steps” 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 two Gaps” 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.

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.

Absolute stabil i tyAbsolute stabil i ty• • 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 healing There is no callus formation.Direct bone healing

is achieved.is achieved.

Relative stabil i tyRelative stabil i ty • • Movement at fracture siteMovement at fracture site • • There is no interfragmentary There is no interfragmentary

compression at fracture compression at fracture site.It is achieved by splinting site.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 is Indirect bone healing is achieved.achieved.

Absolute

(Rigid)

Relative

(Flexible)

Spectrum of Stability

Cast

IM Nail

Compression Plating/ Lag

screw

Ex Fix

Bridge Plating

Practically speaking….Practically speaking….

Most fixation probably involves Most fixation probably involves components of both types of healing.components of both types of healing.

Even in situations of excellent rigid internal Even in situations of excellent rigid internal fixation one often sees a small degree of fixation one often sees a small degree of callus formation.callus formation.

Relative (Rigid)

Absolute

(Flexible)

No callus

Fixation Stability

Callus

Reality

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 Care Good Nursing care of patient with fractures and Care

during transfer and positioning.during transfer and positioning.

Postoperative carePostoperative care• • Immediately after surgery,the treated extremity is Immediately after surgery,the treated extremity is

positioned above the level of the heart to minimize positioned 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.

Early joint motion: CPM (continuous passive motion) machines are Early joint motion: CPM (continuous passive motion) machines are used to provide a continuous but passive (without force of the used 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 the During follow-up treatment, not only look at the xrays but also at the

injured limb. Pain, swelling, and tenderness are signs of either injured limb. Pain, swelling, and tenderness are signs of either instability or infection.instability or infection.

Indications for Internal FixationIndications for Internal Fixation

Displaced intra-articular fracture,Displaced intra-articular fracture, Axial, angular, or rotational instability that Axial, 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.

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.

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.

Lag Screw FixationLag Screw Fixation

Screw compresses both Screw compresses both sides of fx togethersides of fx together Best form of compressionBest form of compression Poor shear, bending, and Poor shear, bending, and

rotational force resistancerotational force resistance Partially-threaded screw Partially-threaded screw

(lag by design)(lag by design) Fully-threaded screw (lag Fully-threaded screw (lag

by technique)by technique)

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.

Lag ScrewsLag Screws Step Three: counter sink Step Three: counter sink

near cortex so screw head near cortex so screw head will sit flushwill sit flush

Step Four: screw inserted Step Four: screw inserted and glides through the near and glides through the near cortex & engages the far cortex & engages the far cortex which compresses cortex which compresses the fx when the screw head the fx when the screw head engages the near cortexengages the near cortex


Lag ScrewsLag Screws

Functional Lag Functional Lag Screw - note the Screw - note the near cortex has near cortex has been drilled to the been drilled to the outer diameter = outer diameter = compressioncompression

Position Screw - Position Screw - note the near cortex note the near cortex has not been drilled has not been drilled to the outer to the outer diameter = lack of diameter = lack of compression & fx compression & fx gap maintainedgap maintained

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

Neutralization PlatesNeutralization Plates

Neutralizes/protectNeutralizes/protects lag screws from s lag screws from shear, bending, shear, bending, and torsional forces and torsional forces across fxacross fx

““Protection Plate"Protection Plate"


Buttress / Antiglide PlatesButtress / Antiglide Plates

““Hold” the bone up.Hold” the bone up. Resist shear forces Resist shear forces

during axial loading. during axial loading. Used in metaphyseal Used in metaphyseal

areas to support intra-areas to support intra-articular fragments.articular fragments.

Plate must match Plate must match contour of bone to truly contour of bone to truly provide buttress effect.provide buttress effect.

Bridge PlatesBridge Plates

““Bridge”/bypass Bridge”/bypass comminution.comminution.

Proximal & distal Proximal & distal fixation.fixation.

Goal: Maintain length, Goal: Maintain length, rotation, & axial rotation, & axial alignmentalignment

Avoids soft tissue Avoids soft tissue disruption at fx to disruption at fx to maintain fx blood maintain fx blood supply.supply.

Tension Band PlatesTension Band Plates Plate counteracts natural Plate counteracts natural

bending moment seen with bending moment seen with physiologic loading of physiologic loading of bonebone Applied to tension side to Applied to tension side to

prevent “gapping”.prevent “gapping”. Plate converts bending forcePlate converts bending force

to compression.to compression. Examples: Proximal Femur Examples: Proximal Femur

& Olecranon.& Olecranon.

Compression PlatingCompression Plating

Reduce & Compress Reduce & Compress transverse or oblique transverse or oblique fx’s.fx’s. Unable to use lag Unable to use lag

screwscrew Exert compression Exert compression

across fracture across fracture Pre-bending platePre-bending plate External compression External compression

devices (tensioner)devices (tensioner) Dynamic compression Dynamic compression

w/ oval holes & w/ oval holes & eccentric screw eccentric screw placement in plateplacement in plate

Examples- 3.5 mm PlatesExamples- 3.5 mm Plates

LC-Dynamic LC-Dynamic Compression PlateCompression Plate:: stronger and stifferstronger and stiffer more difficult to contour.more difficult to contour. usually used in the usually used in the

treatment radius and ulna treatment radius and ulna fracturesfractures

Semitubular plates:Semitubular plates: very pliable very pliable limited strengthlimited strength most often used in the most often used in the

treatment of fibula treatment of fibula fractures.fractures.

Figure from: Rockwood and Green’s, 5th ed.

Figure from: Rockwood and Green’s, 5th ed.

Dynamic Compression PlatingDynamic Compression Plating

Compression applied Compression applied via oval holes and via oval holes and eccentric drillingeccentric drilling Plate forces bone to Plate forces bone to

move as screw move as screw tightened = tightened = compressioncompression

Dynamic Compression Plates

• Note the screw holes in theplate have a slope built intoone 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.


Locking PlatesLocking Plates

Screw head has threads Screw head has threads that lock into threaded that lock into threaded hole in the platehole in the plate

Creates a “fixed angle” at Creates a “fixed angle” at each holeeach hole

Theoretically eliminates Theoretically eliminates individual screw failureindividual screw failure

Plate-bone contact not Plate-bone contact not criticalcritical

Courtesy AO Archives


Must have reduction and compression Must have reduction and compression done prior to using locking screwsdone prior to using locking screws CANNOT PUT CORTICAL SCREW OR LAG CANNOT PUT CORTICAL SCREW OR LAG

SCREW AFTER LOCKING SCREWSCREW AFTER LOCKING SCREW


Increased axial Increased axial stabilitystability

It is much less It is much less likely that an likely that an individual screw individual screw will failwill fail But, plates can But, plates can

still breakstill break


Indications:Indications: Osteopenic boneOsteopenic bone Metaphyseal Metaphyseal

fractures with short fractures with short articular blockarticular block

Bridge plating Bridge plating

Intramedullary NailsIntramedullary Nails Relative stabilityRelative stability Intramedullary splintIntramedullary splint Less likely to break with Less likely to break with

repetitive loading than repetitive loading than plateplate

More likely to be load More likely to be load sharing (i.e. allow axial sharing (i.e. allow axial loading of fracture with loading of fracture with weight bearing).weight bearing).

Secondary bone healingSecondary bone healing Diaphyseal and some Diaphyseal and some

metaphyseal fracturesmetaphyseal fractures

Intramedullary FixationIntramedullary Fixation Rotational and axial Rotational and axial

stability provided by stability provided by interlocking bolts.interlocking bolts.

Reduction can be Reduction can be technically difficult in technically difficult in segmental and segmental and comminuted comminuted fractures.fractures.

Maintaining reduction Maintaining reduction of fractures in close of fractures in close proximity to proximity to metaphyseal flare metaphyseal flare may be difficult.may be difficult.

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

• 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...

•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

SummarySummary Respect soft tissues.Respect soft tissues. Choose appropriate fixation method.Choose appropriate fixation method. Achieve length, alignment, and Achieve length, alignment, and

rotational control to permit motion as rotational control to permit motion as soon as possible.soon as possible.

Understand the requirements and Understand the requirements and limitations of each method of internal limitations of each method of internal fixation.fixation.

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AO Principles of Fracture treatment & Different Implants