IMPLANTS IN
ORTHOPAEDICS
DR ABHISHEK SHETTY
HISTORY
The basic foundation
 Lord Lister– aseptic surgery in 1860
 Morton & Simpson– ether & chloroform
for anesthesia
 Roentgen (1896)-- xrays
EVOLUTION
Pre Lister era
 Gold, Silver, iron, platinum and
many others were used as implants
 Pins wires, hooks books also used
 Bell (1804) and Lavert (1829)– silver
and platinum implants
Post Lister era/ antiseptic era
 Lister himself was the first to wire a
patella with silver wire.
 Hansman– early exponent of plate
and screws, used plated sheet steel
 Sir Arbuthnot Lane placed plate and
screw on firm footing by using high
carbon steel/ stout steel




Von Bayer– pins for intraarticular
small fragment fixation.
Hey Grooves(1893)– advocated rigid
fixation of fractures
Sherman (1912) used vanadium
During the same time stainless steel
was discovered with discovery of
chromium!! Stainless steel era was
thus launched!

1959- Ferguson and Lang published
their work “ metals and engineering
in bone and joint surgery” type 316
steel was recognised.. 316L is now
replacing 316
Advances in implant of fracture
fixation




Smith Peterson 1937—triflanged nail
Mc laughlin and throton introduced
extra plate to S-P nail.
60 yrs ago kuntscher–
intramedullary nailing
A.O/ ASIF group– 1950 in Europe by
18 surgeons.
IMPLANTS

DEFINITION
As a substance made of living/non
living material with a specified form
which can be inserted into the body
through skin/ mucus membrane to
sub serve a specific function and to
remain there for a significant
duration.
Common qualities
1. Function without breaking,
distorting or deteriorating.
2. Not produce deleterious effect on
host
3. Easier to insert and remove.
Functions
1. Replace a diseased damaged or
worn out part
2. Immobilize fractures or osteotomies
3. Aid in correction of deformities
IDEAL IMPLANT
1.
2.
3.
4.
5.
Should be inert & non toxic to the
body
Corrosion proof
Easily fabricated
Great strength & high resistance to
fatigue
Should be inexpensive.

PHYSICAL PROPERTIES
1. Corrosion resistance
2. Fatigue resistance
3. Shape & dimensional compatibility
4. Interchange ability
5. Sterilization
6. Freedom from toxic effects
7. Freedom from surface defects
8. Marking and packing
Testing of implants
CATEGORIES
 Physical
 Chemical
 Structural
 Biological

1.
2.
3.
4.
5.
Physical
appearance
Weight
Magnetism
Hardness
Microstructure

1.
2.
3.
CHEMICAL
Molybdenum detection test
Molybdenum percentage estimation
Corrosion test

1.
2.
STRUCTURAL CHARACTERISTICS
Design specifications
Mechanical stability

1.
2.
3.
4.
5.
6.
Implant design
Possible forces acting on implant &
whether implant is strong enough to
neutralize these forces.
Function for considerable time
Surgical convenience
Anatomical factors
Stress protection effect
Cost

1.
2.
3.
Methods of checking profiles
Naked eye examination & magnification
photography.
Profile magnification be done by using a
profile projector or a slide projector
Industrial x-rays
-slot foe screw driver
-canal of canulated screw
-structural defects
METALS IN ORTHOPAEDICS




METALLIC GROUPS
Stainless steel or iron based alloys
Cobalt based alloys
Titanium based alloys
Stainless steel
first modern alloy system
corrosion resistant
contains carbon, molybdenum,
chromium and nickel




Carbon increases strength but
decreases corrosion resistance
Chromium increases passivity by
forming stable chromium oxide
Molybdenum counters the action of
chloride ions &organic acids in body
fluids & thus increases passivity
Nickel keeps structure of steel stable



Commonly used types
AISI 316L—implant steel
AISI 440B—instrument steel

1.
2.
3.
4.
5.
Advantages & disadvantages of
stainless steel
Offers good mechanical strength
Possesses excellent ductility
Shows work hardening effects
Time-tested metal
It may show local corrosing &
pitting corrosion
DRILLBIT STEEL

Extremely hard

Can be sharpened well

Not ductile & can easily break

Not corrosion resistant
COBALT-BASED ALLOY

Vitallium or F75--- commonly used
cobalt-chromium alloy– contains 27
to 30 % chromium, 5 to 7 %
molybdenum, cobalt making up
remaining

1.
2.
3.
4.
5.
Advantages & disadvantages
Are inert
Posses high modules of elasticity &
high strength than steel
Difficult to machine
Quite expensive
Has low ductility & bind securely to
bone
TITANIUM


PURE TITANIUM is soft hence not
commonly used
However AO grp popularising pure
titanium of good strength & ductility-LCDCP

1.
2.
3.
4.
Advantages & disadvantages
Less prone to fatigue
Outstanding corrosion resistance
Optimal amount of torque
Technologies are not well
established
FUTURE



TRIP( transformation-induced
plasticity) steels
Refractory metals—tungsten,
tantalum and molybdenum
Nickel-titanium alloys memory
metals (nitinol)
BIOCOMPATIBILTY OF IMPLANT

CORROSION– damage of material
due to action of its environment
1-change in colour
2-formation of surface film
3-disintegration of material

1.
2.
Effects of corrosion
Tissue inflammation & necrosis
Weakening of implant

1.
2.
Corrosion process
Chemical
Electrochemical
CORROSION CLINICAL
RELEVANCE




UNIFORM ATTACK
GALVANIC OR BIMETALLIC
PITTING CORROSION
FRETTING





To make use of corrosion resistant
material for implant manufacturing
To use same material for parts of a
multipart implant
To remove broken drill bit if any, esp
if it is in contact with plate
To keep damage to implant minimum
Avoid instability of fixation
HOST RESPONSE




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
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Fibrine & platelets
Leukocytes
Macrophages
Lymphocytes
Fibroblats
Bone minerals
FB giant cells

1.
2.
3.
4.
Modified
Macrophages may remain in vicinity
of implants..
Significant number of lymphocytes
& plasma cells near the implant
Multinucleated giant cells
All implants surrounded by fibrous
capsule
CLINICAL RELEVANCE




Chronic inflammation
Loosening
Sterile abscess
neoplasia
IMPLANT FAILURE

1.
2.
3.
Every implant is subjected to
various forces because of
Gravity
Muscle action
Wt bearing

1.
2.
3.
4.
5.
Forces are
Tension
Compression
Bending
Shear
torsion



Implant –loading in tension—more force--deformation.
As force removed implant gets back to its
original shape– elastic deformation
Force excess—implant does not get back
to its original shape, there after even if
force is decreased material continues to
deform till implant fails-plastic
deformation.

1.
2.
3.
Deformation dependant on
Force applied
Original length
Original cross-sectional area


Deformation with respect to original
length—strain
Force applied per unit area--stress
Stress
Strain





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Strength
Rigidity or ductility
Yield stress, max stress, ultimate stress
Ductile failure
Brittle failure
Fatigue failure
Creep
Stress concentration