principles of internal fixation

PRINCIPLES OF INTERNAL FIXATION

» DR MANU MATHEW» MODERATOR DR GAURAV SHARMA

• Historical Background• Preoperative Planning• Fracture Reduction• Techniques and Devices for Internal Fixation

Historical Background

• First reports on modern techniquesof internal fixation are only about 100 years old.

• Elie and Albin Lambotte “osteosynthesis” offractures with plates and screws, wire loops and

external fixators

Robert Danis (1880to 1962) introduced the term of “soudure autogéne

Maurice Müller was impressed by DANIS &founded the Arbeitsgemeinschaftfür Osteosynthesefragen (AO)

Gerhard Küntscher(1900 to 1972) in Germany had developed the technique of IMnailing,

• GOAL OF OPERATIVE FRACTURE FIXATION

• full restoration of function

• faster return to his preinjury status• • minimizethe risk and incidence of

complications.

• Predictable alignment of fracture fragments

The purpose of implants

to provide a temporary support

to maintain alignment during the fracture healing

to allow for a functional rehabilitation

Biology and Biomechanics onFracture Healing

fractured bone needs - a certain degree of immobilization -optimally preserved blood supply

-biologic or hormonal stimuli in order to unite.

Soft Tissue Injury and Fracture Healing

“every fracture is a soft tissue injury, where the bone happens to bebroken,”

The more extensive the zone of injury and the tissue destruction, the higher is the risk for a delay of the healing process or for other complications

mechanical stability,

Absolute stability

rigid fixation that doesnot allow any micro motion

elastic fixation

provided by internal or external splintingof the bone

High Rate of Healing

Spectrum of Healing

Absolute Stability =10 Bone Healing

Relative Stability =20 Bone Healing

Biology of Bone HealingTHE SIMPLE VERSION...

Fibrous Matrix > Cartilage > Calcified Cartilage > Woven Bone > Lamellar Bone

Haversian Remodeling

Minimal Callus

Callus

Absolute

(Rigid)– eg Lag screw/ plate– Compression plate

Relative– (Flexible) – eg– IM nailing

– - Bridge plating

0

No callus

Fixation Stability

Callus

Reality

Functions of Fixation

• Interfragmentary Compression– Lag Screw

• Plate Functions– Neutralization– Buttress– Bridge– Tension Band– Compression– Locking

• Intramedullary Nails– Internal splint

• Bridge plate fixation– Internal splint

• External fixation– External splint

• Cast– External splint

*Not internal fixation

Indications for Internal Fixation

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

cannot be controlled by closed methods• Open fracture• Polytrauma• Associated neurovascular injury

The components of a preoperative plan• Timing of surgery• Surgical approach• Reduction maneuvers• Fixation construct• Intraoperative imaging• Wound closure/coverage• Postoperative care• Rehabilitation

Prophylactic Antibiotics

• In general a second generation cephalosporinwith a broad spectrum is recommended, applied as single dose

• 30 minutes before the start of surgery or for a period of a maximum

• 24 to 48 hours postoperatively

Fracture Reduction

• The goal of reduction is to restore the anatomical relationship

Direct Reduction

• Direct reduction – fragments are manipulated

directly by the application of different instruments or hands, via open exposure of the fracture

•

joysticks

Collinear reduction clamp

Reduction Forceps provide an excellent purchase onthe fragments without stripping or squeezing the periosteumEG WEBERS FORCEPS

ADVANTAGES

precise restorationof anatomy;

DISADVANTAGES

1 more interference with bone and soft tissue biology.

2 higher risk of infection and

3 possibly a delay in bony union

Open Reduction

• Open reduction implies that the fracture site is exposed, allowing to watch and inspect the adequacy of reduction with our eyes.

Indications for open reduction

1 Displaced articular # with impaction of the joint surface

2 #which require exact axial alignment (e.g., forearm #, simple metaphyseal #)

3 failed closed reduction due to soft tissue interposition

4 Delayed surgery where granulation tissue or early callus has to be removed

5 high risk for neurovascular structures6 no or limited access to perioperative imaging tocheck reduction

Indirect reduction

• Indirect reduction means that the reduction and alignment of the # by applying reduction forces indirectly

• via the soft tissue envelope—to the main fragments by manual Or skeletal traction, a distractor, or some other means.

• classical example of indirect reduction is the “closed” insertion

• of an intramedullary nail on a fracture table

The distractor

Indirect reduction

ADVANTAGES virtually NO exposure of the fracture site ;

LESS damage to the vascularity of the tissue

DISADVANAGES1demandingtechnique and that 2the correct overall alignment of the fracture is more difficult to assess, especially in rotation

Closed Reduction

• Closed reduction relies entirely on indirect fragment alignment by ligamentotaxis or the pull of the soft tissue envelope

• Traction is the most common means to reduce a fracture

– D/A applied across a joint and that there are limited possibilities to move the limb.

Eg The fracture table

The distractor

offers many possibilities and more freedom of movement•D/Aquite demanding to manipulate and requires considerable practice

advantages of closed reduction

• minimal damage to soft tissues• safer• more rapid fracture repair • lesser infection.

Indications for closed reduction

• Most diaphyseal fractures • • Minimally displaced articular fractures.• Geriatric femoral neck fractures,

trochanteric fractures, subcapital humerus fractures, and certain distal radius fractures

Techniques and Instruments for Fracture Reduction

Screws

• The two basic principles of a conventional screw are

• to compress a fracture plane (lag screw) and

• to fix a plate to the bone (plate screw)

• Cortical screws:

–Greater number of threads

–smaller pitch

–Outer thread diameter to core diameter ratio is less

–Better hold in cortical bone

–Usually fully threaded

–Size1-4.5mm diameter

–Self tapping ,cannulated etcFigure from: Rockwood and Green’s, 5th ed.

•Cancellous screws:– Larger thread to core diameter ratio

–pitch is greater

-Lag effect with partially-threaded screws- – Theoretically allows better fixation in cancellous bone

- indicated for meta-epiphyseal ,cancellous bone

Tapping is recommend

LHS•The LHS have a head with a thread•that engages with the reciprocal thread of the plate hole.

•a screw-plate device with angular stability

variable angular stability, which allows angulating lockingscrews within the plate hole to address specific fractureconfigurations

LAG SCREW

Positioning Screw a fully threaded screw that joins two anatomical parts at a defined distancewithout compression. The thread is therefore tappedin both cortices.example is a screw placed between fibulaand tibia in a malleolar fracture

Plates• Conventional non locked screws used to fix a plate to the

bone plate is pressed against the bone

which produces preload and friction between the two surfaces.

• #forearm bones ,• simple metaphyseal fractures of long bones, malunion and nonunions,

D/A local cortical necrosis

HISTORY OF PLATES

• Early modern plates - round holes the conical--firm fit

the dynamic compression• plate (DCP) by Perren

. spherical screw head and an inclined oval screw hole

•Angle blade plates tubular plates,•reconstruction plates, the sliding hip screw and dynamic condylar

•LC-DCP (limited contact-•DCP)

THE FIVE FUNCTIONS OF PLATING

• Neutralization or protection• Compression• Buttressing• Tension band function• Bridging

Neutralization Plates

• Neutralizes/protects lag screws from shear, bending, and torsional forces across fx

• “Protection Plate"

Buttress / Antiglide Plates• “Hold” the bone up• Resist shear forces during axial loading – Used in metaphyseal areas to

support intra-articular fragments• Plate must match contour of bone to

truly provide buttress effect• Buttress Plate– When applied to an intra-articular

fractures • Antiglide Plate– When applied to diaphyseal

fractures

• Order of fixation:• Articular surface compressed with

bone forceps and provisionally fixed with k-wires

1. Bottom 3 cortical screws placed • Provide buttress effect

2. Top 2 partially-threaded cancellous screws placed• Lag articular surface together

3. Third screw placed either in lag or normal fashion since articular surface already compressed

Buttress Concepts

Figure from: Schatzker J, Tile M: The Rationale of Operative Fracture Care. Springer-Verlag, 1987.

Bridge Plates

• “Bridge”/bypass comminution

• Proximal & distal fixation• Goal:– Maintain length, rotation, &

axial alignment

• Avoids soft tissue disruption at # = maintain # blood supply

Tension Band Plates

• Plate counteracts natural bending moment seen wih physiologic loading of bone

– Applied to tension side to prevent “gapping”

– Plate converts bending force to compression

– Examples: Proximal Femur & Olecranon

Plate Pre-Bending Compression• Prebent plate– A small angle is bent into the

plate centered at the #– The plate is applied– As the prebent plate compresses

to the bone, the plate wants to straighten and forces opposite cortex into compression

– Near cortex is compressed via standard methods• External devices as shown• Plate hole design

Screw Driven Compression Device

• Requires a separate drill/screw hole beyond the plate

• Currently, more commonly used with indirect fracture reduction techniques

Dynamic Compression Plates

•

Dynamic Compression Plating

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

move as screw tightened = compression

Lag screw placement through the plate

• Compression + rigidity obtained a with one construct

• Compression plate first

• Then lag screw placed through plate

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

Locking Plates• Screw head has threads that

lock into threaded hole in the plate

• Creates a “fixed angle” at each hole

• Theoretically eliminates individual screw failure

• Plate-bone contact not critical Courtesy AO Archives

Locking Plates• Increased axial stability• It is much less likely

that an individual screw will fail

• But, plates can still breakIndications:– Osteopenic bone– Metaphyseal fractures

with short articular block

– Bridge plating

Intramedullary Nails• Relative stability• Intramedullary splint• Less likely to break with

repetitive loading than plate

• More likely to be load sharing .

• Secondary bone healing• Diaphyseal and some

metaphyseal fractures

Intramedullary Fixation

• Generally utilizes closed/indirect or minimally open reduction techniques

• Greater preservation of soft tissues as compared to ORIF

• IM reaming has been shown to stimulate fracture healing

• Expanded indications i.e. Reamed IM nail is acceptable in many open fractures

Intramedullary Fixation• Rotational and axial

stability provided by interlocking bolts

• Reduction can be technically difficult in segmental and comminuted fractures

• Difficult to Maintain reduction of fractures in close proximity to metaphyseal flare

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

• Note the use of

multiple proximal interlocks where angular control is more difficult to maintain due to the metaphyseal

flare.

• 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...

Percutaneous Plating

• Plating through modified incisions– Indirect reduction

techniques– Limited incision for:

• Passing and positioning the plate

• Individual screw placement

– Soft tissue “friendly”

•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

Failure to Apply Concepts

Summary

• Respect soft tissues• Choose appropriate fixation method• Achieve length, alignment, and rotational

control to permit motion as soon as possible• Understand the requirements and

limitations of each method of internal fixation

Thankyou