Title: BIOMATERIALS AND ARTIFICIAL ORGAN BM1303 S'Sudha Lecturer Dept of Biomedical Engg
1 BIOMATERIALS AND ARTIFICIAL ORGAN
BM1303S.SudhaLecturer Dept of Biomedical
Engg
2UNIT I
3INTRODUCTION TO BIOMATERIALS
- During the last two decades, significant advances
have been made in thedevelopment of biocompatible
and biodegradable materials for
medicalapplications. - In the biomedical field, the goal is to develop
and characterize artificial materialsor, in other
words, spare parts for use in the human body to
MEASURE,RESTORE and IMPROVE physical functions
and enhance survival and qualityof life.
4Whats a biomaterial?
- 1980 - Passive and inert point of view
- Any substance or drugs, of synthetic or
natural origin, which can be used for any period
alone or as part of a system and that increases
or replaces any tissue,organ or function of the
body - 1990 Active point of view
- Non-living material used in a medical device
and designed to interact with biological systems
5Classification of biomaterials
- First generation INERT
- Do not trigger any reaction in the host neither
rejected nor recognition do not bring any good
result - Second generation BIOACTIVE
- Ensure a more stable performance in a long time
or for the period you want - Third generation BIODEGRADABLE
- It can be chemically degraded or decomposed by
natural effectors (weather, soil bacteria,
plants, animals)
6What is a biocompatible material?
- Synthetic or natural material used in intimate
contact with living tissue (it canbe implanted,
partially implanted or totally external). - Biocompatible materials are intended to
interface with biological system toEVALUATE,
TREAT, AUGMENT or REPLACE any tissue, organ or
function ofthe body. - A biocompatible device must be fabricated from
materials that will not elicit an adverse
biological response
7Mechanical Properties of Metals
- How do metals respond to
external loads? - Stress and Strain
- Tension
- Compression
- Shear
- Torsion
- Elastic deformation
- Plastic Deformation
- Yield Strength
- Tensile Strength
- Ductility
- Toughness
- Hardness
8Stress-Strain Behavior
- Elastic deformation
- Reversible when the stress
- is removed, the material
- returns to the dimension it
- had before the loading.
- Usually strains are small
- (except for the case ofplastics).
- Plastic deformation
- Irreversible when the stress
- is removed, the material
- does not return to its
- previous dimension.
9Stress-Strain Behavior Plastic deformation
- Plastic deformation
- stress and strain are not proportional the
deformation is not reversible deformation occurs
by breaking and rearrangement of atomic bonds (in
crystalline materials primarily by motion of
dislocations)
10Typical mechanical properties of metals
- The yield strength and tensile strength vary
with prior - thermal and mechanical treatment, impurity
levels, - etc. This variability is related to the behavior
of - dislocations in the material. But elastic
- moduli are relatively insensitive to these
effects. - The yield and tensile strengths and modulus of
- elasticity decrease with increasing temperature,
- ductility increases with temperature.
11Mechanics of Materials
- The point up to which the stress and strain are
linearly related is called the proportional
limit. - The largest stress in the stress strain curve is
called the ultimate stress. - The stress at the point of rupture is called the
fracture or rupture stress. - The region of the stress-strain curve in which
the material returns to the undeformed state when
applied forces are removed is called the elastic
region. - The region in which the material deforms
permanently is called the plastic region. - The point demarcating the elastic from the
plastic region is called the yield point. The
stress at yield point is called the yield stress.
12Mechanics of Materials
- The permanent strain when stresses are zero is
called the plastic strain. - The off-set yield stress is a stress that would
produce a plastic strain corresponding to the
specified off-set strain. - A material that can undergo large plastic
deformation before fracture is called a ductile
material. - A material that exhibits little or no plastic
deformation at failure is called a brittle
material. - Hardness is the resistance to indentation.
- The raising of the yield point with increasing
strain is called strain hardening. - The sudden decrease in the area of cross-section
after ultimate stress is called necking.
13Viscoelasticity
- Definition time-dependent material
- behavior where the stress response of that
- material depends on both the strain applied
- and the strain rate at which it was applied!
- Examples
- biological materials
- polymer plastics
- metals at high temperatures
14Elastic versus viscoelastic behaviors
- For a constant applied strain
- An elastic material has a unique material
response - A viscoelastic material has infinite material
responses depending on the strain-rate
15Viscoelastic Hysteresis
- Viscoelastic solid
- some energy is dissipated with dashpots (as
heat)some energy is stored in springs. Area in
the hysteresis loop is a function of loading rate - For viscoelastic material, energy is dissipated
regardless of whether strains(or stresses) are
small or large - Under repetitive loading, a viscoelastic
material will heat up
16Wound healing
- All wounds heal following a a specific sequence
of phases which may overlap - The process of wound healing depends on the type
of tissue which has been damaged and the nature
of tissue disruption - The phases are
- Inflammatory phase
- Proliferative phase
- Remodelling or maturation phase
17The ways in which wounds heal
- Three basic classifications exist
- Healing by primary intention
- Two opposed surfaces of a clean, incised wound
- (no significant degree of tissue loss) are held
together. - Healing takes place from the internal layers
outwards - Healing by secondary Intention
- If there is significant tissue loss in the
formation of the - wound, healing will begin by the production of
- granulation tissue wound base and walls.
- Delayed primary healing
- If there is high infection risk patient is
given antibiotics - and closure is delayed for a few days e.g.
bites
18Wound assessment
Lab tests TcPO2
Signs of infection
Size, depth location
Odour or exudate
WOUND ASSESSMENT
- Wound bed
- necrosis
- granulation
Wound edge
Surrounding skin colour, moisture,
19The healing process
- Day 0 5
- The healing response starts at the moment of
injury the clotting cascade is initiated - This is a protective tissue response to stem
blood loss - The inflammatory phase is characterised by heat,
swelling, redness, pain and loss of function at
the wound site - Early (haemostasis)
- Late (phagocytosis)
- This phase is short lived in the absence of
infection or contamination
20Granulation
- Day 3 14
- Characterised by the formation of granulation
tissue in the wound - Granulation tissue consists of a combination of
cellular elements including - Fibroblasts, inflammatory cells, new capillaries
embedded in a loose extra-cellular collagen
matrix, fibronectin and hyularonic acid
21Moist wound healing
- Basic concept is that the presence of exudate
will provide an environment that stimulates
healing - Exudate contains
- Lysosomal enzymes, WBCs, Lymphokines, growth
factors.. - There are clinical studies which have shown that
wounds maintained in a moist environment have
lower infection rates and heal more quickly
22Factors affecting healing
- Immune status
- Blood glucose levels (impaired white cell
function) - Hydration (slows metabolism)
- Nutrition
- Blood albumin levels (building blocks for
repair, colloid osmotic pressure - oedema) - Oxygen and vascular supply
- Pain (causes vasoconstriction)
- Corticosteroids (depress immune function)
23Host Reactions to Biomaterials
- Effect of the Implant on the Host
- Local
- Blood material interactions
- Protein adsorption
- Coagulation
- Fibrinolysis
- Platelet adhesion, activation, release
- Complement activation
- Leukocyte adhesion, activation
- Hemolysis
- Toxicity
24- Modification of normal healing
- Encapsulation
- Foreign body reaction
- Pannus formation
- Infection
- Tumorgenesis
- Systemic and remote
- Embolization
- Hypersensitivity
- Elevation of implant elements in the blood
- Lymphatic particle transport
25Effect of the Host on the Implant
- Physical mechanical effects
- Abrasive wear
- Fatigue
- Stress corrosion, cracking
- Corrosion
- Degeneration and dissolution
- Biological effects
- Absorption of substances from tissues
- Enzymatic degradation
- Calcification
26Temporal Variation of Inflammatory Response
27- Activated by injury to vascularized connective
tissue - Series of reactions
- Various cells
- Controlled by endogenous and autocoid mediators
28UNIT II
29Types of Metallic Implants
- Stainless steel
- Cobalt Based Alloys
- Titanium Alloys
30Stainless Steels
- Fe 60-65 wt, Cr 17-19 wt , Ni 12-14 wt
- Carbon content reduced to 0.03 wt for better
The most common stainless steel 316Lresistance
to in vivo corrosion. - Why reduce carbon Reduce carbide (Cr23C6)
formation at grain boundary. Carbide impairs
formation of surface oxide - Why add chromium corrosion resistance by
formation of surface oxide. - Why add nickel improve strength by increasing
face centered cubic phase (austenite)
31Stainless Steels
- Good stainless steel
- Austenitic (face centered cubic)
- No ferrite (body centered cubic)
- No carbide
- No sulfide inclusions
- Grain size less then 100mm
- Uniform grain size
32Cobalt Based Alloys
- Common types for surgical applications
- ASTM F75
- ASTM F799
- ASTM F790
- ASTM F 562
33Cobalt Alloys ASTM F75
- Co-Cr-Mo
- Surface oxide thus corrosion resistant
- Wax models from molds of implants
- Wax model coated with ceramic and wax melted away
- Alloy melted at 1400 C and cast into ceramic
molds.
34Cobalt Alloys ASTM F75
- Three caveats
- Carbide formation corrosion. Solution
annealing at 1225 C for one hour. - Large grain size reduced mechanical strength
- Casting defects stress concentration,
propensity to fatigue failure
35Cobalt Alloys ASTM F799, ASTM F90
- Cobalt Alloys ASTM F799
- Modified form of F75 hot forged after casting
- Mechanical deformation induces a shear induced
transformation of FCC structure to HCP. - Fatigue, yield and ultimate properties are twice
of F75. - Cobalt Alloys ASTM F90
- W and Ni are added to improve machinability and
fabrication - Mechanical properties similar to F75
- Mechanical properties double F75 if cold worked
36Titanium Based Alloys
- Lighter
- Good mechanical properties
- Good corrosion resistance due to TiO2solid oxide
layer - Ti-6 wt Al-4 wt V (ASTM F136) is widely used
- Contains impurities such as N, O, Fe, H, C
- Impurities increase strength reduce ductility
37Titanium Alloys ASTM F136
- HCP structure transforms to BCP for temperatures
greater than 882 C. - Addition of Al stabilizes HCP phase by increasing
transformation temperature - V has the inverse effect.
38ceramic
- Any of various hard, brittle, heat-resistant and
corrosion-resistant materials made by shaping and
then firing a nonmetallic mineral,such as clay,
at a high temperature - Clinical success requires
- Achievement of a stable interface with
connective tissue - Functional match of the mechanical behavior
of the implant with the tissue to be replaced - Critical Issues
- Integrity of bioceramic
- Interaction with the tissue
39Hydroxyapatites (HA)
- Chemically similar to mineral component of bones
- It will support bone ingrowth and
osseointegration - when used in orthopaedic, dental and
maxillofacial applications - Chemical formula Ca5(PO4)3OH
- Hexagonal Bravais lattice
- The chemical nature of hydroxyapatite lends
itself to substitution common substitutions
involve carbonate, fluoride and chloride
substitutions for hydroxyl groups
40Uses for HA
- Facial augmentation with hydroxyapatite has been
used for the following - corrections Cheek, Chin, Jaw, Nose, Browbone.
- Skeletal repair biomaterials
- Ocular prosthesis
- Hydroxyapatite from coral
- The eye muscles can be attacheddirectly to this
implant, allowing it to move within the
orbit-just like the natural eye.
41Calcium Phosphate Bioceramics
- There are several calcium phosphate ceramics that
are consideredbiocompatible most are resorbable
and will dissolve when exposed tophysiological
environments. - Hydroxyapatite is thermodynamically stable at
physiological pH values actively takes part in
bone bonding, forming strong chemical bonds with
surrounding bone - Mechanical properties unsuitable for load-bearing
applications such as orthopaedics - Used as a coating on materials such as titanium
and titanium alloys,where it can contribute its
'bioactive' properties, while the metallic
component bears the load - Coatings applied by plasma spraying
42(No Transcript)
43UNIT III
44Polymeric Biomaterials
- What is a polymer?
- Long chain molecules that consist of a number of
repeating units (mers) - Fabricated from monomers which change somehow in
polymerization - Loss of H20, HCl or other molecule
- Polymer properties are more complex than for
simpler materials - Types of polymers
- Biological polymers
- DNA, cellulose, starch, proteins, rubber, etc
- Often reconstituted to form usable polymer
- Mainly collected from animals
- Synthetic polymers
- Fabricated from petroleum products (generally)
- May be also a modified biological polymer
- Most plastics and similar materials
45Classification
- examples examples examples
46Classes of Polymers (I)
- Thermoplastic polymers
- Long chains with very limited or no cross-linking
- They behave in a plastic, ductile manner (above
Tg) - Melt when heated and are thus easily remolded and
recycled - Thermoset polymers
- Highly cross-linked, 3D network structures
- Generally brittle (at most temperatures)
- Decompose when heated and cant easily be
reshaped or recycled
47Classes of Polymers (II)
- Elastomers and rubbers
- Large amounts of elastic deformation
- Some (light) cross-linking
- Typically, about 1 in 100 molecules are
cross-linked on average - Average number of cross-links around 1 in 30
yields a more rigid and brittle material (closer
to a thermoset) - Crosslinks allows material to return to original
shape without plastic deformation
elastomer
thermoset
48Definitions
- Oligomer- molecules with nlt10 (less than ten
monomers) - Degree of polymerization, P number of monomer
residues per chain - Functionality number of bonding sites per
monomer.A monomer must possess at least two
bonding sites - Homopolymer
- A-A-A-A-A-A-A-A
- Copolymer
- Random A-B-A-A-A-B-B-A-B-B-B-A-B-B
- Alternating A-B-A-B-A-B-A-B-A-B
- Block A-A-A-A-A-B-B-B-B-B-B
- Graft As with Bs on branches
- Linear polymer- no branches
- Branched polymer - multiple branches
- Crosslinked polymer- links between branches
49Polymer Basics
- Polymerization process
- Initiation I ? 2R (the active center which acts
as a chain carrier is created) - Propagation RM1 M ? RM2 (growth of
macromolecular chain) - Termination kinetic chain is brought to halt
50- Synthesis Reactions
- Addition polymerization
- Condensation polymerization
- Source Askeland Phule p 677
51(No Transcript)
52PE (Polyethylene) PP (Polypropylene)
- Used in high density form astubing for drains and
catheters - Ultra high molecular weight form used as acetabul
component in artificial hips and other
prosthetic joints - Has good toughness and wear resistance
- Resistant to lipid absorption
- High rigidity
- Good chemical resistance
- Good tensile strength
- Excellent stress cracking resistance
- Used for sutures and hernia repair
53PTFE (Polytetrafluoroethylene)PVC(Polyvinylchlori
de)
- Aka Teflon
- Very hydrophobic
- Good lubricity
- Low wear resistance
- Used for catheters and vascular grafts (Gore-Tex)
- Made flexible and soft bythe addition of
plasticizers - Not suitable for long term use because
plasticizers can be extracted by thebody - Used as tubing for blood transfusions, feeding
anddialysis, and blood storagebags
54Elastomers - Entropy
If you stretch it far enough the chains will line
up straight enough to crystallize
55Elastomer vs. Thermoplastic Elastomers
- Some amorphous polymer exhibit elastomeric
behavior, yet have no chemical crosslinks - Usually block copolymers possessing both rubbery
regions and stiff regions in the chain - Physical interactions between stiff chain regions
act a physical crosslinks - Rubbery regions allow large
deformations - Thermoplastic in nature can be
melted since there are no chemical
crosslinks
Styrene butadiene styrene (SBS)
56Thermosets
- Disadvantage
- Thermosets are difficult to re-form
- Advantages in engineering design applications
- High thermal stability and insulating properties
- High rigidity and dimensional stability
- Resistance to creep and deformation under load
- Light-weight
- Crosslinking of thermosets
- 10-50 of the mers in a chain are crosslinked
- Heat treatment, vulcanization processes link
existing chains - Two part chemistries (resin and curing agent) are
mixed and react at room temp or elevated
temperatures multi-functional end groups
57Polymers as Biomaterials
- Hydrogels
- swellable materials, usually acrylic copolymers,
e.g. poly(2-hydroxyethyl methacrylate) PHEMA - More in lecture 10
- Piezoelectric materials
- materials that generate transient electrical
charges on their surfaces upon mechanical
deformation, e.g. polyvinylidene fluoride,
collagen - Resorbable materials
- Resorbed with time, e.g. polyglycolic and
polylactic acid - More in lecture 11
58Fluorinated Polymers
- PTFE
- Plain or expanded (Gore-Tex)
- Vascular grafts, sutures, middle ear prostheses
- Fluorocarbons
- High affinity for oxygen
- Blood substitutes
- Vinylidene Fluoride (PVDF)
- Piezoelectric
- Actuators, nerve guidance
PTFE unsuccessful in joint replacements
59Polymethyl methacrylate
- PMMA
- A hydrophobic linear chain polymer that is
transparent, amorphous and glassy at room
temperature (also known as plexiglass or lucite) - Good light transmittance, toughness, and
stability - A good material for intraocular lenses and hard
contact lenses - Also used as a bone cement
60Polyethylene
- PE
- High density form (HDPE)
- Used for tubing in catheters and drains
- High molecular weight form (UHMWPE)
- Contact surface in artificial hips, knees
- Good toughness, resistance to fat and oils, and
low cost
61Polyethylene Glycol
- PEG
- Short chain neutral hydrophilic polymer
- Shown to repel cells due to surface energy
- Used for coatings non-thrombogenic
- Wound healing polymerization on the wound
- Microencapsulation and drug delivery
62Biological Polymers
- Many cellular and extracellular materials are
polymers - Polysaccharides (made from monosaccharides)
- Cellulose
- Alginate
- Proteins (made from amino acids)
- Collagen
- Actin
- Fibrin
- Nucleic Acids (made from nucleotides)
- DNA
- RNA
- More in lecture 12
63Silicones
- Silicone polymers
- e.g. Polydimethylsinoxane (PDMS)
- No carbon backbone silicone and oxygen instead
- Elastomers (with crosslinks)
- Silicones as biomaterials
- Very low Tg
- Excellent flexibility and stability
- Used in catheters, pacemaker leads,
- vascular grafts, and breast and
- facial implants
- High oxygen permeability - membrane
- oxygenators
64Common clinical applications and types of
polyCommon clinical applications and types of
polymersused in medicine
65Polymers In Specific Applications
65
66UNIT IV
67Soft Tissue Implants
- Attempts have been made to replace or augment
most of the soft tissues in the body - Connective tissues skin, ligament, tendon,
cartilage - Vascular tissue blood vessels, heart valves
- Organs heart, pancreas, kidney
- Other eye, ear, breast
- Most soft tissue implants are constructed from
synthetic polymers - Possible to choose and control the physical and
mechanical properties - Flexibility in manufacturing
- "Soft tissue implants" can also be designed for
soft tissue repair
68Sutures
- Used to repair incisions and lacerations
- Important characteristics for sutures
- Tensile strength
- Flexibility
- Non-irritating
69Tissue Adhesives
- Used for repair of fragile, non-suturable tissues
- Examples Liver, kidney, lung
- The bond strength for adhesive closed tissues is
not as strong after 14 days as for suture closed
tissues
70Percutaneous Implants
- Refers to implants that cross the skin barrier
- In contact with both the outside environment and
the biological environment - Used for connection of the vascular system to
external "organs" - Dialysis
- Artifical heart
- Cardiac bypass
- Also used for long term delivery of medication or
nutrition (IV) - Main Problems
- Attachment of skin (dermis) to implant difficult
to maintain through ingrowth due to rapid
turnover of cells - Implant can be extruded or invaginated due to
growth of skin around the implant - Openings can also allow for the entrance of
bacteria, which may lead to infection
71Artifical Skin
- Is actually a percutaneous implant -- contacts
both external and biological environments - No current materials available for permanent skin
replacement - Design ideas
- Graft should be flexible enough to conform to
wound bed and move with body - Should not be so fluid-permeable as to allow the
underlying tissue to become dehydrated but should
not retain so much moisture that edema (fluid
accumulation) develops under the graft
72Artificial Skin - Possibilities
- Polymeric or collagen-based membrane
- Some are too brittle and toxic for use in burn
victims - Flexibility, moisture flux rate, and porosity can
be controlled - Fabrics and sponges designed to promote tissue
ingrowth - Have not been successful
- Immersion of patients in fluid bath or silicone
fluid to prevent early fluid loss, minimize
breakdown of remaining skin, and reduce pain - Culturing cells in vitro and using these to
create a living skin graft - Does not require removal of significant portions
of skin
73Soft Tissue Augmentation
- Generally used for reconstructive or cosmetic
enhancement - Functions include one or more of the following
- Space filler
- Mechanical support
- Fluid carrier or storer
- Common applications for soft tissue augmentation
are - Maxillofacial implants
- Eye and ear implants
- Fluid transfer implants
- Breast implants
74Maxillofacial implants
- Designed to replace or enhance hard or soft
tissue in the jaw and face - Intraoral prosthetics (implanted) are used to
reconstruct areas that are missing or defective
due to surgical intervention, trauma, or
congenital condition - Must meet all biocompatibility requirements
- Metals such as tantalum, titanium, and Co-Cr
alloys can be used to replace bony defects - Polymers are generally used for soft tissue
augmentation - Gums, chin, cheeks, lips, etc.
- Injectable silicone had been examined for use in
correcting facial deformities however, it has
been found to cause severe tissue reactions in
some patients and can migrate - Extraoral prosthetics (external attachment)
should - Match the patients skin in color and texture
- Be chemically and mechanically stable
- Not creep, change colors, or irritate skin
- Be easily fabricated
- Have been fabricated out of numerous polymers
75Fluid Transfer Implants
- May be designed as permanent implants to treat
chronic problems - Hydrocephalus
- Build up of cerebrospinal fluid in the brain
- Can result in brain damage if pressure becomes
too high - Treated by draining the fluid to the vascular
system or abdominal cavity - Uses a permanent shunt from the ventricles of the
brain, under the skin, to the receiving tissue - Tubing is made of silicone rubber made radiopaque
to allow for observation with x-rays - Ear Infections
- "Tubes" in the ears are drainage tubes designed
to remove fluid from the middle ear - Constructed from teflon or other inert materials
- Not permanent implants (removed after several
years)
76Orthopaedic Soft Tissue
- Replacement of cartilage, ligaments, and tendons
- Difficult to obtain fixation with bone
- Screws or pins involve stress concentrations and
the possibility of corrosion - Strength of anchorage depends on thickness of
cortical bone at attachment site - In many cases autographs are used - may be
patellar tendon for ACL reconstruction - Allographs - cryo-preserved, fresh-frozen, or
freeze dried specimens taken from cadavers - Often attached to treated bony insertion sites
which can be used as bone grafts (See Figure 6) - Preservation and cold sterilization procedures
may adversely affect properties of implants - Available from tissue banks
77Artificial Orthopaedic Soft Tissues
- Ligament Augmentation Devices (LAD's)
- Artificial materials used to take some of the
stress normally applied to a ligament while
healing occurs - May or may not be resorbable
- Gore-Tex non-resorbable
- PDS resorbable plastic
- Contradictory results exist in the literature as
to the effectiveness of LAD's - Ligament scaffolds
- Made of polyester or other polymers
- Used to induce tissue ingrowth
- May be implanted alone or with a section of
tissue (fat pat, fascia lata, piece of tendon) to
increase rate of ingrowth - Region of fixation for artifical ligaments or
reconstructions with LAD's for the ACL deviates
from normal more than for reconstructions with
patellar tendon alone - Fibrous tissue instead of normal transition from
ligament to bone
78Total Hip Replacement
- A prosthetic hip that is implanted in a similar
fashion as is done in people. It replaces the
painful arthritic joint. - The modular prosthetic hip replacement system
used today has three components the femoral
stem, the femoral head, and the acetabulum. Each
component has multiple sizes which allow for a
custom fit. - The components are made of cobalt chrome
stainless steel and ultra high molecular weight
polyethylene. Cementless and cemented prosthesis
systems are available.
79Common Causes of Hip Pain and Loss of Hip Mobility
- Osteoarthritis
- Usually occurs after age 50 and often in an
individual with a family history of arthritis. In
this form of the disease, the articular cartilage
cushioning the bones of the hip wears away. The
bones then rub against each other, causing hip
pain and stiffness.
80OperationRemoving the Femoral Head
- Once the hip joint is entered, the femoral head
is dislocated from the acetabulum. - Then the femoral head is removed by cutting
through the femoral neck with a power saw.
81Reaming the Acetabulum
- After the femoral head is removed, the cartilage
is removed from the acetabulum using a power
drill and a special reamer. - The reamer forms the bone in a hemispherical
shape to exactly fit the metal shell of the
acetabular component.
82Inserting the Acetabular Component
- A trial component, which is an exact duplicate of
your hip prosthesis, is used to ensure that the
joint will be the right size and fit for the
client. - Once the right size and shape is determined for
the acetabulum, the acetabular component is
inserted into place.
83Preparing the Femoral Canal
- To begin replacing the femoral head, special
rasps are used to shape and scrape out femur to
the exact shape of the metal stem of the femoral
component. - Once again, a trial component is used to ensure
the correct size and shape. The surgeon will also
test the movement of the hip joint.
84Inserting Femoral Stem
- Once the size and shape of the canal exactly fit
the femoral component, the stem is inserted into
the femoral canal.
85Attaching the Femoral Head
- The metal ball that replaces the femoral head is
attached to the femoral stem.
86The Completed Hip Replacement
- Client now has a new weight bearing surface to
replace the affected hip. - Before the incision is closed, an x-ray is made
to ensure new prosthesis is in the correct
position.
87Treatment by Kinesiologist-Early Postoperative
Exercises-
- Regular exercises to restore your normal hip
motion and strength and a gradual return to
everyday activties. - Exercise 20 to 30 minutes a day divided into 3
sections. - Increase circulation to the legs and feet to
prevent blood clots - Strengthen muscles
- Improve hip movement
88UNIT V
89Artificial heart valve
- An artificial heart valve is a device implanted
in the heart of a patient with heart valvular
disease. When one of the four heart valves
malfunctions, the medical choice may be to
replace the natural valve with an artificial
valve. This requires open-heart surgery.
90Types of heart valve prostheses
- There are two main types of artificial heart
valves the mechanical and the biological valves. - Mechanical heart valves
- Percutaneous implantation
- Stent framed
- Not framed
- Sternotomy/Thoracotomy implantation
- Ball and cage
- Tilting disk
- Bi-leaflet
- Tri-leaflet
- Biological heart valves
- Allograft/isograft
- Xenograft
91Types of mechanical heart valves
92Design challenges of heart valve prostheses
- A replaceable model of Cardiac Biological Valve
Prosthesis. - Thrombogenesis / haemocompatibility
- Mechanisms
- Forward and backward flow shear
- Static leakage shear
- Presence of foreign material (i.e. intrinsic
coagulation cascade) - Cellular maceration
- Valve-tissue interaction
- Wear
- Blockage
- Getting stuck
- Dynamic responsiveness
- Failure safety
- Valve orifice to anatomical orifice ratio
- Trans-valvular pressure gradient
- Minimal leakages
- Replaceable Models of Biological Valves
93Artificial limb
- An artificial limb is a type of prosthesis that
replaces a missing extremity, such as arms or
legs. The type of artificial limb used is
determined largely by the extent of an amputation
or loss and location of the missing extremity.
Artificial limbs may be needed for a variety of
reasons, including disease, accidents, and
congenital defects.
94Lower Limb Prosthesis
- Components of the Prosthesis
- Socket- Forms the connection between the residual
limb and the prosthesis. - Sleeve- Provides suction suspension for
prosthesis. - Shank (pylon)- Transfers weight from socket to
the foot-ankle. - Foot-ankle- Absorbs shock and impact and provides
stability.
95Dental implant
- A dental implant is an artificial tooth root
replacement and is used in prosthetic dentistry
to support restorations that resemble a tooth or
group of teeth. There are several types of dental
implants. The major classifications are divided
into osseointegrated implant and the
fibrointegrated implant. Earlier implants, such
as the subperiosteal implant and the blade
implant were usually fibrointegrated
96WHAT IS A DENTAL IMPLANT?
- Dental implant is an artificial titanium
fixture (similar to those used in orthopedics) - which is placed surgically into the jaw bone to
- substitute for a missing tooth and its root(s).
97Surgical Procedure
STEP 1 INITIAL SURGERY STEP 2 OSSEOINTEGRATION
PERIOD STEP 3 ABUTMENT CONNECTION STEP 4
FINAL PROSTHETIC RESTORATION
Success Rates
lower jaw, front 90 95 lower jaw, back 85
90 upper jaw, front 85 95 upper jaw, back
65 85
98First Implant Design by Branemark
All the implant designs are obtained by
the modification of existing designs.
John Brunski
99Astra Tech.
Comparison of Implant Systems
ITI
Bicon
100Perfectly elastic large displacement non-linear
contact finite element analysis for different
insertion depths.
- Contact pressure increases linearly with
insertion depth.
101Elastic-plastic large displacement non-linear
contact finite element analysis for different
insertion depths
Bilinear Isotropic Hardening Model
Stress (MPA)
Strain
102Contact Pressure Distribution for Different
Insertion Depths
- Contact pressure increases non-linearly with
larger - insertion depths.
103FUTURE WORK
- Comparison of different implant designs in
- terms of stress distribution in the bone due to
- occlusal loads.
- Modeling non-homogenous bone material
- properties by incorporating with CT scan data.
- Comparison of different implant-abutment
- interfaces