history/important differences 316L stainless steel vs titanium alloys

1. PRESENTOR-DR MOHAMMED
NAYEEMUDDIN
MODERATOR-DR SACHIN SHAH

2.  METALS AND IMPLANTS IN ORTHOPAEDICS
---HISTORY
---IMPLANTS OF FRACTURE FIXATION :EVOLUTION
---PHYSICAL PROPERTIES
---TESTING OF IMPLANTS
---METALLIC IMPLANTS
---NON METALLIC IMPLANTS
---BIOMATERIALS USED IN ORTHOPAEDICS
---CARBON COMPOUNDS AND POLYMERS
 BIOABSORABLE IMPLANTS IN ORTHOPAEDICS
---ADVANTAGES
---DISADVANTAGES
---FUTURE.

3.  Implants are devices or tissues that are
placed inside or on the surface of the body.
 Many implants are prosthetics, intended to
replace missing body parts.
 STIFFNESS – it is the resistance of a structure
to deformation.
 RIGIDITY – it is used in context of fracture
fixation describes an implant or of a bone-
implant construct physical property of
resisting deformation under load.
 ELASTICITY- it is the ability of a material to
recover its original shape after deformation.

4.  PLASTICITY – the ability of a material to be
formed to a new shape without fracture and
retain that shape after load removal.
 DUCTILITY – the ability of solid material is to
be deformed under tensile stress and to be
stretched into a wire without fracture. It
also bestows capacity to be shaped eg.
Construction of bone plates.

5.  HISTORY-
 With the advent of antiseptic surgery
b/w 1860s and 1870s by LORD
JOSEPH LISTER and anaesthesia by
MORTON (ETHER) and SIMPSON
(CHLOROFORM),the surgery
developed rapidly.
 When the development of technology
in metallurgy and plastic took place –
IMPLANT SURGERY simultaneously
developed rapidly.
 A further impetus to internal fixation
was given by discovery of X –RAYS BY
ROENTGEN in 1896.
LORD LISTER
Wilhelm Conrad Röntgen

6.  In the pre listerian days , many surgeons were
using hooks , pins and wires made of various
metals – gold ,silver ,platinum or iron to
manipulate and hold fracture fragment in
position.
 Bell in 1804 used silver coated steel pins and
noted corrosion in them.
 It was noted even at that time two different
metals produced electrolytic corrosion.
 LAVERT in animal experiment found platinum
was the most inert metal but platinum, gold and
silver were found to be too soft for clinical
use.

7.  The real development of implant surgery for
fracture fixation started advent of aseptic
surgery.
 LISTER himself was one of the first to
successfully wire a fractured patella using a
silver wire.
 HANSMANN(1866) was one of the early person
to fix a fracture with PLATE AND SCREW.
 --his implants were made of nickel plated sheet
steel, since corrosion and breakup of implants
was well known then , he used plates which
were bent at right angles and use to protrude
out of wound and likewise screw heads were
outside the skin,
 --the whole implant was removed by 6-8wks
,when the fracture fragment was expected to be
GUMMY.

8.  SIR WILLIAM ARBUTHNOT LANE (BRITISH
SURGEON & PHYSICIAN )
 He was the early pioneer, who placed plate
and screw fixation on sound footing.
 He devised his form of plates.
 It was made of “STOUT STEEL” a high
carbon steel of fairly high percentage of
carbon.
 He devised “NO TOUCH” technique , to
prevent wound infections and his own
results bear testimony of his great skills.
 However he and many other surgeons fail to
distinguish b/w real wound infection vs
infection caused by corrosion of metals.
 His implants became brittle in nature and
used to break at the junction of central bar
and the 1st hole.
Sir William Arbuthnot Lane

9.  At the time that LANE was popularizing his
ideas in UK , the LAMBOTTE BROTHERS ,
ELIE and especially ALDIN were working in
belgium on the fixation on fractures
 They used other metals like aluminium, silver
,brass , magnesium and copper plates as well
as steel coated with gold and silver.
 Their plates were curved to fit the curvature
of the bone.
 The total disintegration of the magnesium
plates used with steel screws underlined the
effects of electrical corrosion when two
separate metals were used.

10.  SHERMAN(1912).
 He improved the design of LANE’S plate to
make it stronger.
 His implants were made of “VANADIUM
STEEL”, an alloy containing much less carbon
and 0.1-0.15% of vanadium along with small
amounts of chromium and molybdenum.
 In spite of this, staining of tissue was found
by iron indicating presence of corrosion
products.

11.  VON BAYER in 1908 introduced pins for
fixation of “small fragments” at the intra
articular level.
 EARNEST HEY GROVES in 1893 stressed
the value of rigid fixation and showed
that movement at the fracture site
encouraged corrosion and break up of
the fixation device.
 He was the 1st to try fixing fractures of
the femoral neck by round pins
introduced through the trochanter , as
well as the use of round intramedullary
rods for the fractures of the shaft of long
bones.
 This idea was forgotten till revived by
KUNTSHER in 1940.
Ernest William Hey Groves

12.  The story of stainless steel, it is said ,
started in SIBERIA with discovery of a new
mineral “CHROMITE” way back in 1776.
 The metal chromium extracted from
chromite , a decade later, was found to
posses an unusual property, AN EXTREMELY
GOOD RESISTANCE TO CORROSION.
 Then onwards chromium plating of metallic
surface became popular.

13.  The discovery of chromium prompted
scientists in Europe and America to alloy with
IRON.
 The idea was to produce a good engineering
material at a reasonable cost.
 It was L GULLIET of France who was the 1st to
make alloy systems close to what we call
stainless steel.
 P MONNARTZ of Germany after a research of
3 years 1st noticed that its rustlessness comes
with making alloy when the concentration of
CHROMIUM is atleast 13%.

14.  The 18-8 SMo was the 1st stainless steel to
give satisfactorily as an SURGICAL IMPLANT.
 Its corrosion resistance is high and it is one
of the best form of steel available.
 But In 1959 ,BECHTOL,FERGUSSON AND
LAING published their authoriatative work ,
” Metals and Engineering in Bone and Joint
Surgery ” , which described the superior
property of type 316 stainless steel, after
further work 316L STAINLESS STEEL is used
coz of low carbide content.

15.  In last 30 years another metal which came
into use is TITANIUM because of its total
inertness(chemically inactive) in the body.
 Titanium has found more favours with neuro
surgeons for covering the skull defects .
 TITANIUM,VITALLIUM have the
fabrication(invention)versatility and strength
of stainless steel and excellent compatibilty
in the body.
 This metal was primarily used for aerospace
application and is just starting to be used in
the fabrication of surgical implants.

16.  A brief review of the various advances in
the design of implants for fracture
fixation other than plates and screws is
interesting
 For fractures of femoral neck , SMITH-
PETERSON in 1937 introduced the solid
triflanged nail.
 JOHNSON modified it into cannulated
nail.
 TOURNTON AND MCLAUGHLIN separately
introduced the extra plate attachment to
improve the fixation of the distal
fragment.
 Numerous other models including the
JEWETT ONE PIECE FIXATION device has
been introduced since then.

17.  For the fracture of shaft of long bones especially
femur , tibia and humerus , kuntscher revived
the idea of intra medullary fixation but improved
on hey groves original idea of round rods by
using clover leaf or V-shaped nails.
 Use of compression to bring about early fracture
healing has found increasing favours.
 DANIS of BELGIUM was the 1st to write about the
biomechanics of fracture healing produced by a
compression plate and screws.
 He was the 1st to describe “PRIMARY HEALING ”
of fracture.

18.  Sir JOHN CHARNLEY introduced
and popularised the compression
method of arthodesis of joints
especially the knee.
 The AO GROUP
(ARBEITGEMEINTSCHAFTS FUR
OSTEOSYNTHESEFRAGEN) was
formed in BIEL , switzerland by 13
surgeons on NOVEMBER 6th 1958.
 A combination of high powered
technology, metallurgical
excellence and a high level of
technical skill in optimum
operating conditions has allowed a
total change in the concept of
many fractures by combining the
principles of rigid fixation
,compression and early mobility.
Sir John Charnley
(1911-1982)

20.  When formulating a standard specification for
instrument and an implant , the following
requirements are given due to consideration.
 • Material sharpness of cutting instruments,
freedom from surface defects
 • Corrosion resistance
 • Fatigue resistance
 • Shape and dimensional compatibility
 • Tensile, torsional and bending properties
 • Interchangeability
 • Performance and ease of operation
 • Sterilization
 • Freedom from toxic effects
 • Marking and packaging.

21.  Implants can be tested under following
categories:
1) • Physical
2) • Chemical
3) • Structural
4) • Biological.

22. I.Physical Tests
 Following points are considered under this
category:
a)• Appearance: Indian Standards Institute
[(ISI), the former name of the Bureau of
Indian Standards (BIS)]
Specification directs that the implants
should be free from cracks, draw marks,
pits, burrs and surface contamination.
They should be polished bright .
b).Weight: Screws of identical diameter,
geometry and length should weigh same,
provided they are of the same alloy.

23. c)• Magnetism:
The austenitic(primary phase) stainless steel
(ISI 316) is nonmagnetic.
 A magnet is applied to the implant and
tested for its magnetism.
 A small implant can be lifted up by the
magnet ,
 A large implant when suspended will be
found to zoom(move) with the magnet.

24. d)• Hardness:
It is the ability to resist plastic deformation
under identical load.
Rockwell superficial hardness testing to
scale 30T is used to comply with
nondestructive testing and to check even the
small components as well.
• This test involves a load of 30 kg and an
indentor of 1/16 inch diameter ball. Two
readings are taken and the mean is
calculated.

25.  • Other methods.
“IMPACT TEST” -- with an elevated standard
pendulum, the implant is struck and the
energy absorbed in the fracture is measured.
•” Spark test”:
 Molybdenum has a characteristic spark
profile.
• The implant is abraded on a standard
grinding wheel, and spark trajectories are
noted for the characteristics.

26.  These are studied under the following heads:
A. • Molybdenum detection test
B. • Molybdenum percentage estimation
C. • Corrosion test.
 ISI 316 steel should contain molybdenum
between 2.0% and 3.5%.

27. A. Molybdenum Detection Test
 “Mini-Moly Detector” kit (produced by Met
Associates, Navsari, Gujarat State) is available in
the market. It consists of an especially
developed electrolyte solution and electrodes
with a portable dry cell power source. The test
procedure is as follows.
 A drop of the electrolyte is placed on the
stainless steel under test, and the electrodes are
placed against the electrolyte solution. to turn
pink or rosy red. If molybdenum is present, the
drop will retain its hue and if not, the hue will
fade rapidly.

28. B. Molybdenum Percentage Estimation
 This can be carried out by various metal
testing laboratories in all major cities.
C. Corrosion Test (Aqua Regia)
 It contains hydrochloric acid and nitric acid
in the proportion of 3:1, and it is a strong
solvent.
 If the implants are of identical alloys, they
should dissolve identically. The percentage
loss is estimated and compared with the
standard one.

29.  These are considered under the following two heads:
 1. Design specification
 2. Mechanical stability.
1.Design Specification.
 ISI has laid down specifications for each implant.
 For example,
bone screw can be checked against the following points:
• Angle and diameter of the head
• Slots
• Thread diameter
• Core diameter
• Edge width
• Angle of the thread and pitch
• Angle of the tip and flutes.
 2. Mechanical Stability.
Geometry of the bone plates with regard to the location of screw
holes, thickness and acute bends are studied and compared with
the ISI specifications.

30.  ISI has specified methods for testing biological
compatibility of metals for surgical implants.
 Magnetic implants are liable to corrode by
galvanic reaction in the body and hence should
be rejected.
 There has been argument that during
manufacturing process, cutting tools would
impart certain magnetism to implants. This
argument is not tenable since in the process of
buffing and subsequent cleaning, the magnetic
particles would be wiped away and the implant
should become nonmagnetic.
 Every surgeon should test all his implants before
purchase by various methods mentioned before.

31.  Regarding mechanical stability, certain
biomechanical principles need to be strictly
adhered to,
 They are:
1. • Holes in the plates are potential sites of
weakness
2. • Thicker the plate, more rigid it is
3. • Acute angles and sharp bends in the
implants should be avoided, and
4. • One piece implant is better mechanically
than joined implant.

32. STAINLESS STEEL 316L
(Fe+Cr+Ni+Mo+C+Mn+Si)
 There are at least 50 alloys and grades of alloys identified as
commercial stainless steel. Only a few are useful as implant
biomaterial in fracture surgery.
 Stainless steel designated as ASTM(American Society for
Testing and Materials) F-55, -56 (grades 316 and 316L) is used
extensively for fracture fixation implants.
 Type 316L stainless steel is an iron-based alloy.
 Alloying with chromium generates a protective, self-
regenerating chromium oxide layer which provides a major
protection against corrosion.
 The addition of molybdenum decreases the rate of slow,
passive dissolution of the chromium oxide layer by up to
1,000 times. Molybdenum further protects against pitting
corrosion. Nickel imparts further corrosion resistance and
facilitates the production process, while limited quantities of
manganese and silicon are added to control some
manufacturing problems.

33.  The carbon component increases the
strength but in the alloy is undesirable.
 Type 316L stainless steel has a very low
permissible level of carbon to minimize this
problem.
 Though it is a strong, stiff and biocompatible
material, 316L stainless steel has a slow but
finite corrosion rate.
 Concerns about the long-term effects of
nickel ions, however, prevail. Stainless steel
is best suited for short-term implantation in
the body as in fracture fixation

34.  Stainless steel is frequently used because
 the base materials are cheap,
 the alloy can be formed using common
techniques, and its mechanical properties can be
controlled over a wide range for strength and
ductility(is when a solid material stretches
under tensile stress)
 The elastic modulus(absolute value) of stainless
steel is approximately 12 times higher than the
elastic modulus of cortical bone.

35.  The cobalt-chromium-tungsten-nickel alloy
(ASTM F-90) is used for manufacture of
fracture fixation implants.
 In clinical practice it is used to make wire
and internal fixation devices including
plates, intramedullary rods, and screws.

36.  Titanium is the ninth most abundant element in
the earth’s crust.
 The pure element is very reactive; it is the only
element that burns in nitrogen.
 However, the metal rapidly becomes coated with
an oxide layer, making it physiologically inert
and resistant to most chemicals.
 Titanium is used for making orthopedic implants
in two forms:
1. commercially pure
2. variety of alloys.
 Titanium-aluminum-vanadium alloy (ASTM F-136)
is commonly referred to as Ti6AI4V. This alloy is
widely used to manufacture implants.

37.  Commercially, pure titanium is not a single
chemical element, but is alloyed by a level of
oxygen dissolved into the metal. It also has
traces of iron, nitrogen, carbon and hydrogen.
 Titanium has an elastic modulus approximately
half that of the stainless steel and cobalt-
chromium alloys.
 The corrosion resistance of pure titanium is
outstanding because a very dense and stable
layer of titanium oxide (Ti02) is formed. This
protective oxide layer may be destroyed
mechanically during implantation by instruments
such as bending pliers.

38.  The passive layer is restored spontaneously,
rapidly and effectively (repassivation).
 In the presence of unstable fixation, the
titanium components of an internal fixation
system are subjected to fretting conditions
and produce metal debris.
 Such debris causes gray or black coloration
of the surrounding tissues.
 This discoloration, which is not a result of
corrosion, is “harmless”.

39. FACTORS STAINLESS STEEL TITANIUM ALLOY
1. ELASTICITY AND
DUCTILITY
LESS MORE
2.ENDURANCE
LIMITS(STRESS LIMITS)
SAME SAME
3.COST CHEAP COSTLY
4.CORROSION RESISTANCE
& TOXIC IONS
+VE COZ OF
CHROMIUM N
NICKEL
-VE
5.ALLERGIC REACTION. +VE -VE
6.SECOND OPERATION MAY REQUIRE HIGH COST IS OFTEN
COMPENSATED COZ
IMPLANT CAN BE LEFT
INSITU & 2ND SURGERY
IS OFTEN UNNECESSARY.

40.  It is a Shape Memory Alloy (SMA) was
discovered in 1965.
 Nitinol is an acronym for nickel titanium naval
ordnance laboratory, where the alloy’s
remarkable properties were discovered.
 The alloy contains nearly equal numbers of
nickel and titanium atoms, leading to its
common compositional representation as NiTi.
 Shape Memory Alloy can be “trained” to take on
a predetermined shape in response to a stimulus
such as a change in temperature.

41.  Implant made from SMA has the ability to return
to its original shape after the environment
temperature rises to a certain level (e.g. 37 deg
C). Its shape can be changed easily at low
temperature (e.g. O-5 deg C).
 SMA can be bent, compressed, or deformed in
many other ways, but can then be made to
recover its original shape by heating.
 USES/CLINICAL APPLICATIONS:
a. Compressive staples for fibula and scaphoid,
b. Clamp-on bone plates,
c. long bone fixator and patella fixator

42.  Biomaterials now have a large subsection of
nonmetallic implants which find use in
miscellaneous other indications.
 Biomaterials can be defined as being
“natural or synthetic substances, capable of
being tolerated permanently or temporarily
by the human body.’
 Biocompatibility of these biomaterials could
be graded as inert (ceramics), interactive
(tantalum), viable (biodegradable polymers),
replant (cultured native tissue).

43.  • Metal and metal alloys: As discussed
earlier in this chapter
 • Ceramics and ceramo-metallic materials
 • Carbon materials and composites,
polymers.
 Ceramics and Ceramometallic Materials

44.  Ceramic is a synthesized, inorganic, solid, crystalline
material excluding metals.
They can be classified into:
 1.Bioinert Ceramics 2. Bioactive ceramics
3.Bioresorable ceramics
1. BIOINERT CERAMICS
 They are incorporated in the bone in accordance with
pattern of contact osteogenesis.
 There two types , alumina ceramics (A1203) and
zirconia ceramics (Zr02).
 Alumina is chemically more stable than PSZ in vivo,
 While PSZ is mechanically stronger than alumina and
both of them exhibit much better wear resistant
characteristics compared to stainless steel .
 Used in making ceramic hip prostheses

45. 2. Bioactive Ceramics
 These have a characteristic of osteoconduction
and the capability of chemical bonding with
living bone tissue in accordance with the pattern
of “bonding osteogenesis’
 These include glasses, glass ceramics and
ceramics that elicit a specific biological response
at the interface between the material and the
bone tissue which results in the formation of a
bond between them.
 Bioglass , apatitewollastonite containing glass
ceramics (AW-GC) and synthetic hydroxyapatite
(HA) are representative materials currently used
for clinical applications.
 Using AW-GC various bone prostheses like
vertebral prosthesis, iliac crest prostheses,
intervertebral spacers, laminoplasty spacers
were fabricated.

46. 3.Bioresorbable Ceramics
 These are gradually absorbed in vivo and
replaced by bone in the bone tissue.
 The pattern of their incorporation in the
bone tissue is considered similar to contact
osteogenesis, although the interface
between bioresorbable ceramics and bone is
not stable as that observed with bioinert
ceramics.

47. Carbon Compounds
 In spite of unrivalled endurance to fatigue,
biomedical carbon is not gaining popularity.
 Due to less structural flexibility, less bending
resistance, intolerance to lengthening it is
not gaining popularity.
 Particles found in the spleen means that we
should be careful in using these components.

48. Polymers
Silicones
 These are chemically inert, have good biotolerance, and high
hydrophobic capacity.
 They are used in plastic surgery or in orthopedics in the form of
elastomer, rubbers for joint prostheses of fingers.
Polyacrylics
 Polymethyl methacrylate (PMMA) is used as the
polymer of choice in securing implant to bone since
its introduction in 1970s by Sir John Charnley.
 It is provided in two parts, liquid monomer which
helps methacrylate powder to polymerize.
Radiopaque barium sulfate or zirconia helps its
visualization on radiographs.
 The reaction is exothermic.
 Clinical studies show that thermal necrosis caused by
the heat does not affect overall performance.
Antibiotics added can aid in prophylaxis or treatment
of infection.

49.  Tissue engineering is a multidisciplinary field
that enlists the knowledge and experience of
scientists involved in materials science,
biomedical engineering, cell and molecular
biology, and clinical medicine to produce of
biomaterials that can replace ill functioning or
missing tissues or organs.
 Tissue engineered biomaterials are clearly an
important development.
 We can imagine being able to reach into the
freezer, take out a cell culture, treat it with
growth factors on a scaffold matrix, and
produce almost any tissue in the human body.
This may be a common clinical practice in
future.

51.  Introduction
 The principal focus in modern implant development is
on developing devices that are stronger, durable and
more acceptable to the body.
 Biodegradable implants have allowed a paradigm
shift away from bionic (mechanical replacement)
engineering toward true biologic solutions in
orthopaedics reconstruction.
 There are inherent problems with the use of these
metallic devices like stress shielding
phenomenon( reduction in bone density (osteopenia)
as a result of removal of typical stress from the bone
by an implant ), pain, local irritation.
 Retained metallic implants carry risk of infection.
Metal ion release implants are recorded, though long-
term effects of these are not yet known.

52.  History
 Low molecular weight polyglycolic acid (PGA)
was synthesized by Bischoff and Walden in 1893.
‘the first synthetic absorbable suture was
developed from PGA by American Cyanamid Co.
in 1962.
 ‘Vicryl’ has been successfully used since 1975;
similar materials have shown no carcinogenic,
teratogenic, toxic, or allergic side effects; mild
nonspecific inflammation may be encountered
sometimes.
 Use of PGA as reinforcing pins, screws, and
plates for bone surgery was first suggested by
Schmitt and Polistina.

53.  It is a hard, tough, crystalline polymer with an
average molecular weight of 20,000-145,000 and
melting point of 224-230°C.
 In orthopedic implants poly-L-lactic acid (PLLA)
has been used more extensively because it
retains its initial strength longer than poly-D-
lactic acid (PDLA).
 PGA belongs to the category of fast degrading
polymers, and intraosseously implanted PGA
screws have been shown to completely disappear
within 6 months.
 PLLA, on the other hand, has a very long
degradation time and has been shown to persist
in tissues for as long as 5 years post-
implantation.

54.  Advantages
 The biggest advantage is that since these
implants have the potential for being completely
absorbed, the need for a second operation for
removal is overcome
 Long-term interference with tendons, nerves
and the growing skeleton is avoided.
 Additionally, the risk of implant-association
stress shielding and infections is reduced.
 An important aspect is that these implants do
not interfere with clinical imaging, allowing MRIs
at any stage after surgical implantation.

55. 1. Biodegradable implants are available for
stabilization of fractures, osteotomies, bone grafts
and fusions particularly in cancellous bones, as well
as for reattachment of ligaments, tendons,
meniscal tears and other soft tissue structures.
2. Arthroscopic surgery is the most recent orthopedic
discipline to embrace biodegradable implant
technology. It is used extensively for anterior
cruciate ligament (ACL) reconstruction in the form
of interference screws and transfixion screws. In
the shoulder rotator cuff tears, shoulder instability,
and biceps lesions that require labrum repair or
biceps tendon tenodesis can be managed with these
implants.
3. Bioresorbable material use in pediatric situations
was perhaps the earliest recorded use in orthopedic
literature. These have been used as self-reinforced
absorbable rods for fixation of physeal fractures, in
paediatric olecranon and elbow #s.

56. 4.Ankle fracture fixation is another area where
self-reinforced absorbable rods have been
successfully employed. Bioabsorbable implants
offer specific advantages in the foot where
removal of the hardware is mandatory in some
fixations like syndesmotic disruptions and
Lisfranc’s dislocations.
5.There are bioabsorbable implants now available
for use in humeral condyle, distal radius and
ulna, radial head and other metaphyseal areas.
Bioabsorbable meshes are available for
acetabular reconstructions.
6. Bioabsorbable implants are also variously used
in cranio-maxillofacial surgery and dental
surgery.

57.  There are quite a few problems that need to be addressed with
the use of these devices.
 Primarily, the inadequate stiffness of the device and weakness
compared to metal implant can pose implantation difficulties
like screw breakage during insertion and also make early
mobilization precarious.
 The other potential disadvantages are an inflammatory
response described with bioabsorbable implants, rapid loss of
initial implant strength and higher re-fracture rates.
 Bostman et al. reported an 11% incidence of foreign body
reaction to PGA screws in malleolar fracture. However, the
fracture fixation did not suffer in any case.
 Problem areas of concern regarding faster resorbed implants
are due to the fact that the body mechanisms are not able to
clear away the products of degradation, when they are
produced at faster rate. This leads to a foreign body reaction,
which however, has only been recorded in the clinical
situation. No experimental study has been able to document
this, nor have the exact mechanisms and causes identified.
 Many manufacturers are introducing colored implants, but the
literature records significantly higher rates of inflammatory
reaction with the use of colored implants.

58.  Bioabsorbable implant research is an evolving science.
Resorbable plates can be covalently BMP-2 and represents
a novel protein delivery technique. BMP-2 covalently
linked to resorbable plates has been used to facilitate
bone healing. Covalent linking of compounds to plates
represents a novel method for delivering concentrated
levels of growth factors to a specific site and potentially
extending their half-life.
 An area for future development would have to focus on
developing implants that degrade at the “medium term’
Since the screw that persists in its track for 5 years or
more does not offer the advantage of bioresorbability,
newer molecules may have to be studied.
 In vitro studies have shown promising results of antibiotic
elution from bioabsorbable microspheres and beads.
 Animal in vivo tests have shown that antibiotic
impregnated polymers can successfully treat induced
osteomyelitis in rabbits and dogs.
 All in one, this is a concept that has perhaps come to stay.
What the future holds in this sphere, is something we will
have to wait and see.