Biomaterials for Soft Tissue Replacement 1
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Transcript of Biomaterials for Soft Tissue Replacement 1
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BIOMATERIALS Biomedical Engineering
Sem-III
Prof. Arunkumar Ram
Module 9: Biomaterials for
Soft Tissue Replacement
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INTRODUCTION
On what factors does success of biomaterials
depends?
1.
Materials used2. Design considerations
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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INTRODUCTION
The success of soft
tissue implant has
been primarily
because of
development of
synthetic polymers.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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INTRODUCTION
Why success of soft tissue is on polymers?
• Polymers can be tailor made to match the
properties of soft tissues.
• Made into various physical forms
• Liquids for space fillings
• Fibers for sutures materials
• Films for catheter balloons
• Knitted fabrics for blood vessels
• Solid forms for weight bearing applications
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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INTRODUCTION
Why success of soft tissue is on polymers?
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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INTRODUCTION
Why success of soft tissue is on polymers?
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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INTRODUCTION
Why success of soft tissue is on polymers?
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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INTRODUCTION
Minimal requirement for a soft tissue implant
• They should achieve a close approximation of
physical properties especially flexibility and texture.
• They should not deteriorate or change properties
after implantation with time.
• They should not cause adverse tissue reaction.
• They should be non carcinogenic, nontoxic, non
allergenic, non immunogenic.
• They should be sterilizable.
• They should be low cost8
Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
Two kinds of sutures
• Absorbable
• Non Absorbable
• Also classified on the basis of their origin
• Natural Sutures (catgut, silk and cotton)
• Synthetic Sutures (nylon, polyethylene, polypropylene
• Also classified on their physical form
• Monofilament
• Multifilament
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
The absorbable suture catgut made up of collagen derived
from sheep intestinal submucosa.
Treated with chromic salt (chromium salt) to increase its
strength and is cross linked.
This treatment extends the life of catgut suture by 3-7
days upto 20-40 days
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
It is very interesting to know….
Stress concentration at a surgical knot
decreases the suture strength of catgut by half,
no matter what kind of knotting technique you
use.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
Most effective knotting technique is the square knot
technique with three ties to prevent loosening.
But one of the studies reveal that whether you make loose
knot or tight knot, there is no measureable difference in
the wound healing
But recommended to have loose suturing, it lessens pains
and reduces cutting soft tissues.12
Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
Catgut and other absorbable sutures (PGA, PLA) invokes
tissue reactions although the effect diminishes as they are
being absorbed.
Silk and cotton show more reaction as compared to synthetic
sutures like polyester, nylon, polyacronitrile.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
Risk of Infection
If suture is contaminated, risk of infection may increase
many folds.
Polypropylene, nylon, PGA sutures developed lesserdegrees of infection than sutures made from chromic
catgut and polyester.
The cause of infection is micro organism not biomaterial
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
Surgical Tapes and Staples
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
Surgical Tapes and Staples
Why are surgical tapes used?
1. Avoid pressure necrosis (death of body cells/tissues)
2. Scar tissue formations
3. Problem of stitch abscesses (collection of pus)
4. Problems of Weakened Tissues
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
Problem with Surgical Tapes/Band aids
1. Misaligned Wound edges
2. Poor adhesion caused by moisture, dirt.
3. Wound drainage
4. Late separation of tapes etc…
Applications
Assembling scraps of donor skin for skin graft.
Correcting nerve tissues for neural growth, etc…
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
STAPLES
Staples made up of metals (Ta, Stainless steel, TI-Ni Alloy)
can be used for closure of large surgical incision
In procedures like Cesrean section
Intestinal surgery
Surgery for bone fracture
Tissue response is similar to synthetic sutures.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
STAPLES
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
STAPLES
Time for a Video
1_GIA Surgical Stapler.mp4
2_surgery simple interrupted suturing
wound.mp4
(WARNING: Light hearted people close
your eyes)20
Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e
s t e r : I I I
http://localhost/var/www/apps/conversion/tmp/scratch_3/1_GIA%20Surgical%20Stapler.mp4http://localhost/var/www/apps/conversion/tmp/scratch_3/2_surgery%20simple%20interrupted%20suturing%20%20wound.mp4http://localhost/var/www/apps/conversion/tmp/scratch_3/2_surgery%20simple%20interrupted%20suturing%20%20wound.mp4http://localhost/var/www/apps/conversion/tmp/scratch_3/2_surgery%20simple%20interrupted%20suturing%20%20wound.mp4http://localhost/var/www/apps/conversion/tmp/scratch_3/2_surgery%20simple%20interrupted%20suturing%20%20wound.mp4http://localhost/var/www/apps/conversion/tmp/scratch_3/1_GIA%20Surgical%20Stapler.mp4
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SUTURES, SURGICAL T APES AND
A DHESIVES
Tissue Adhesives
Special environment of tissues and their
regenerative capacity makes tissue adhesives
difficult.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m e
s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
Ideal Characteristics of Tissue Adhesives
Should be able to wet and bond tissue
Be capable of rapid polymerization without
producing much heat or toxic by products
Be Resorbable
Not to interfere with normal healing process
Have ease of applications during surgery Be Sterilizable
Have adequate shell life
Ease of large scale production22
Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
Alkyl-α-cyanoacrylate is best know tissue
adhesive
With addition of some plasticizers and
adhesive they are commercially available as
Eastman 910®, Crazy Glue®
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B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
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SUTURES, SURGICAL T APES AND
A DHESIVES
0
100
200
300400
500
600
700
1 3 7 10 14
Suture
Methyl-2-
cyanoacrylate
TIME (days)
Bond Strength
(grams)
Bond Strength of Wounds with different closure materials 24
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B i o m a t e r i a l s
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SUTURES, SURGICAL T APES AND
A DHESIVES
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Bond strength of adhesive treated wound is about
half that of sutured wounds after 10 days.
Because of lower strength and lesser
predictability of in vivo performance, this is
limited to use after trauma in fragile tissues or
after extensive surgery in soft tissue.
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PERCUTANEOUS AND SKIN IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Percutaneous devices (Trans or through the
skin)
Artificial kidneys, hearts
Prolonged injection of drugs and nutrients.
Artifical skin (maintaining body temperature of
several burned patients)
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PERCUTANEOUS AND SKIN IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Percutaneous Devices
Problem of obtaining a functional and viable interface
between the tissue and implant (percutaneous) is due to
following factors
1. Initial attachment of the implant with the tissue may
occur but this may not continue for a long time
• Dermal tissue cells turn over continuously and dynamically
2. Down growth of epithelium around the implant mayoccur.
3. Opening large enough may give way for bacteria to
penetrate.
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PERCUTANEOUS AND SKIN IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m e s t e r : I I I
Percutaneous Devices
Many variables are involved in development of
percutaneous devices
1. End-use factors
• Transmission of information (biopotentials, temperature,
pressure, blood flow rate)
• Energy (electrical stimulation, power for heart assistdevice)
• Matter (cannula for blood)
• Load (attachment of prosthesis)
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PERCUTANEOUS AND SKIN IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Percutaneous Devices
Many variables are involved in development of
prcutaneous devices
2. Engineering factors
• Material selection: polymers, ceramics, metals, and composites
• Design Variation: button, tube, porous or smooth surface.
• Mechanical Stresses: soft or hard tissue interface, porous or smoothinterfaces
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PERCUTANEOUS AND SKIN IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Percutaneous Devices
Many variables are involved in development of
prcutaneous devices
3. Biological factors
• Implant host: man, dog, hog, rabbit, sheep, etc
• Implant location: abdominal, dorsal, forearm, etc.
4. Human Factors
• Postsurgical care
• Implantation technique
• Esthetic look
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PERCUTANEOUS AND SKIN IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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PD-Skin Interface
D
A
B
C
E
Epidermis
Dermis
Hypodermis
Fascia
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PERCUTANEOUS AND SKIN IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
PD-Skin Interface
A. Interface between epidermis and PD should be completely
sealed against invasin by foreign organisms
B. Interface between dermis and PD should reinforce the
sealing of A, as well as resist mechanical stresses.
C. Interface between hypodermis and PD should reinforce the
function of B
D. Implant material should meet all requirement of an implant
for soft tissue replacement.
E. The line where epidermis, air and PD meet is called a three
phase line which is similar to A
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PERCUTANEOUS AND SKIN IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
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S e m e s t e r : I I I
Artificial Skin
• An example of percutaneous implants.
• Material that can adhere to a large(burned) surface
and thus prevent the loss of fluids, electrolytes, and
other biomolecules until the wound is healed.
• Autografting and Homografting are the only
permanent skin implant solution available.
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PERCUTANEOUS AND SKIN IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Artificial Skin
• Several polymeric materials including reconstituted
collagen have also been tried as burns dressings.
• Among them are co-polymers of vinyl chloride and
acetate and methyl-2-cynoacrylate.
• Plastic tapes have sometimes been used to hold skin
grafts during microtoming (ultrathin sectioning)
and grafting procedures.
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PERCUTANEOUS AND SKIN IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m e s t e r : I I I
Artificial Skin
• Several polymeric materials including reconstituted
collagen have also been tried as burns dressings.
• Among them are co-polymers of vinyl chloride and
acetate and methyl-2-cynoacrylate.
• Plastic tapes have sometimes been used to hold skin
grafts during microtoming (ultrathin sectioning)
and grafting procedures.
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M AXILLOFACIAL IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Maxillofacial Implants
The art and science of anatomic, functional, or
cosmetic reconstruction by means of artificial
substitutes of those regions in the maxilla,
mandible, and face that are missing or defective
because of surgical intervention, trauma, etc.
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M AXILLOFACIAL IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Maxillofacial Implants
There are many polymeric materials available for
extraoral implants which requires
1. Color and texture should match with the patients
2. Mechanically and chemically stable
3. Easily fabricated
Polyvinyl chloride and acetate copolymers Polymethyl
methacrylate silicone and polyurethane rubbers, are
currently used.
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M AXILLOFACIAL IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Maxillofacial Implants
For maxillary, mandibular and facial bone defects,
metallic materials such as tantalum, titaniu and Co-Cr
alloys etc. are used.
For soft tissues like gum and chin, polymers such as
silicone rubber, PMMA etc. are used for augmentation.
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E AR AND E YE IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Ear Implants
The use of implants can restore the
conductive loss from otosclerosis (a heredity defect that
involves a change in the bony tissue of the ear
Chronic otitis media (inflammation of middle ear, which
may cause partial or complete impairment of the ossicular
chain: malleus, incus and stapes)
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E AR AND E YE IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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Ear Implants
Stapes Prosthesis
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E AR AND E YE IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
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Ear Implants
Incus Replacement Prosthesis
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E AR AND E YE IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
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Ear Implants
Whole ossicular chain Prosthesis
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E AR AND E YE IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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Ear Implants
Polyethylene total ossicular replacement
This porous polyethylene total ossicular replacement
implant is used to obtain a firm fixation of the implant bytissue in growth.
Helps in sound conduction.
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E AR AND E YE IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
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Ear Implants
Materials used
Poly tetra fluoroethylene
Ploy ethylene
Silicone rubber
Stainless steel
Tantalum
Polytetrafluoroethylene-carbon composite (Proplast)
Porous polyethylene (Plastipore)
Pyrolite Carbon (Pyrolite)
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E AR AND E YE IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Ear Implants
Artificial Ear Implants capable of processing speech have
been developed and are undergoing clinical evaluation.
Implants have got electrode to stimulate the cochlearnerve cells.
Also speech processor-converts sound waves into electrical
signals.
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E AR AND E YE IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m e s t e r : I I I
Ear Implants
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E AR AND E YE IMPLANTS
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
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S e m e s t e r : I I I
Ear Implants
3_How the VIBRANT SOUNDBRIDGE Middle Ear
Implant Works.mp4
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m e s t e r : I I I
Eye Implants
• Eye implants used to restore the functionality of
cornea and lens when they are damaged or diseased.
• Cornea is usually transplanted from a suitable donor.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m
e s t e r : I I I
Eye Implants
Usually made from “transparent” acrylics, especially
PMMA, which has a comparatively high refractive
index (1.5)
Intraoccular lenses implanted surgically to replace
the original eye lens
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m
e s t e r : I I I
Eye Implants
4_Eye Implants For The Blind.avi.mp4
5_Retinal Implants.mp4
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m
e s t e r : I I I
Blood Interfacing Implants divided into two categories
Short Term Devices
Membranes for artificial organs (kidney and heart/lung
machine)
Tubes catheters for transport of blood
Long term Implants
Vascular implants
Implantable artificial organs
Pacemakers
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m
e s t e r : I I I
Requirement for Blood Interfacing Devices
Blood Compatibility
Blood Coagulation
Implant should not cause blood coagulation
Implants should not cause damage to proteins, enzymes,
and blood components (RBC, WBC and Platelets)
Implants should not cause hemolysis (red blood cell
rupture)
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m
e s t e r : I I I
Vascular Implants
Early Arterial replacements were solid wall tubes made of
glass, aluminum, gold, silver and PMMA.
These implants developed clots and became useless.
1950’s porous implants were introduced, but there was tissue
ingrowth. This minimizes clotting.
Proper fixation of the Implant.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m
e s t e r : I I I
Vascular Implants
Crimping of Blood vessels done to prevent kinking when the
implants is flexed.
Crimping allows expansion of the graft in the longitudinaldirection which reduces strain on the prosthesis wall.
Arteries expand circumferentially and longitudinally to
accommodate the pulsatile flow of the blood.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d
u l e 9
S e m
e s t e r : I I I
Vascular Implants
The type of material, geometry of implant influence the rate
and nature of tissue ingrowth.
No. of polymeric material used to fabricate implants Nylon
Polyester
PTFE
Polypropylene
Silicon Rubber
Recently a pyrolytic carbon coated arterial graft has been developed by
technique of ULTI deposition
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants
Four Valves in Human body
Left ventricular valves become incompetent more
frequently
More importantly Aortic Valve
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants
An artificial heart valve is a mechanism that mimics the
function of a human heart valve
It’s used for patients with a heart valvular disease or have a
damaged valve
Heart valves are used to provide the heart with a
unidirectional blood flow
They act as pumps
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants
1960’s –Flexible leaflets that mimicked the natural valves.
But the leaflets could not bear the fatigue for more than 3
Years.
Hemolysis, Regurgitation, incompetence were major problem
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants
Material Requirement for heart valves same as that of
vascular implants.
Additional requirement of blood flow and pressure regulation.
Formed elements of blood should not be damaged.
Blood pressure should not drop below clinically significant
value.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants-Types
Mechanical- There are three types. The caged ball, tilting
disk, and bi-leaflet
Tissue(biological)- valves that are used from animals to
implant them back into humans
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants
All the types of mechanical heart valves are still in use today.
Usually made of titanium or carbon which makes them strong
and very durable
Three types of mechanical heart valves
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants
Using valves from other animals.
The porcine valve of a pig is the
most comparable valve to a human.
Xenotransplantation
Pericardial valves: Biological valve
tissue can be taken from a cow or
horses pericardial sac and be sewed
to a metal frame.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants
All valves have sewing ring that is covered with various polymeric
fabrics.
This helps during initial fixation of the implant
Later the ingrown tissue will render the fixation viable in a
manner similar to the porous vascular implants.
The cage itself is usually made of metals and covered with fabrics
to reduce noise, or with pyrolytic carbon.
The disc is coated with pyrolytic carbon at the same time.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants
The ball (or disc) is usually made of a hollow structure composed
of solid polymers
Polypropylene
Polyoxymethylene
Polychlorotrifluoroethylene
Metals (titanium, Co-Cr alloys) or pyrolytic carbon deposited on graphite
substrate.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants-Advantages
Mechanical heart valves: The biggest advantage is the
durability. While the tissue heart valves are estimated to last
about 10-15 years, a mechanical heart valve can last 30 year
Tissue heart valves: There is minimal blood regurgitation,
minimal transvalvular pressure gradient, self repairing.
Does not require and anti-coagulant drug.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants-Disadvantages
Mechanical heart valves – In order to decrease the risk of
blood clotting, the patient must take blood thinners. Some
patients can hear their mechanical heart valve open and
close.
Tissue heart valves – Wear, there is a small possibility that the
body will reject the valve, inability to implant them into infantsand children.
.
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Prof. Arunkumar Ram Dept. of Biomedical Engg.
B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Heart Valve Implants-Implanting
Both mechanical and tissue heart valves require open heart
surgery
It’s more common in tissue valves for a re-operation
Complete recovery from surgery could be a couple of weeks
to several months
Currently: 55% mechanical valves
45% tissue valves
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Artificial Heart
Useful for short term use in keeping the patients with
end stage heart disease alive until a transplant heart
becomes available.
Concern is the power supply
Externally powered supply
Can keep alive person for 112 days
But external connection restricted the movements.
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Artificial Heart
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Artificial Heart
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Pacemakers
A cardiac pacemaker use to assist the regular contraction rhythm
of heart muscles.
It should deliver the exact amount of electrical stimulation to the
heart at varying heart rates.
Consist of conducting electrodes attached to stimulator.
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Pacemakers
Electrodes are well insulated with rubber (usually silicone or
polyurethane) except for tip which is sutured or directly
embedded into the cardiac wall.
The tip is usually made up of non corrosive noble metal with
reasonable mechanical strength such as Pt-10%Ir Alloy.
The most significant problems are the fatigue of the electrodes
(they are coiled like spring to prevent this) and formation of
collagenous scar tissue at the tip, which increases threshold
electrical resistance at the point of tissue contact.
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Pacemakers
Battery and electronic components are sealed by a titanium case
while the electrodes outlet are sealed by polypropylene cuff.
Changed after 2-5 years due to limitation of the power source.
Nuclear powered pacemaker is also commercially available.
Lithium powered batteries now available
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Pacemakers
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Artificial Kidney Dialysis Membrane
Primary function of kidney to remove metabolic waste product.
Achieved by passing blood through glomerulus under a pressure
about 75 mm Hg.
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Artificial Kidney Dialysis Membrane
The main filtrate is urea (70 times the urea content of normal
blood)
Sodium
Chloride
Bicarbonated
Potassium
Glucose
Creatinine and uronic acid
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Artificial Kidney Dialysis Membrane
Artificial kidney uses a synthetic semipermeable membrane to
perform the filtering action in a way similar to that of a natural
kidney
The membrane is the key component of the artificial kidney
machine.
In addition it also consists of a bath of saline fluid into which the
waste products diffuse out from the blood to a vein.
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Artificial Kidney Dialysis Membrane
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Artificial Kidney Dialysis Membrane
Three types of kidney dialyzers are available
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B i o m a t e r i a l s
M o d u l e 9
S e m
e s t e r : I I I
Artificial Kidney Dialysis Membrane
Flat Plate Dialyzer
First developed and have two or four layers.
Blood passes through the spaces between the membrane layers while the
dialysate passes through the spaces between the membrane and restraining
boards.
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B i o m a t e r i a l s
M o
d u l e 9
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Artificial Kidney Dialysis Membrane
Coil Membrane
Consist of two cellophane tubes (9 cm in circumference and 108 cm long) are
flattened and coiled with an open mesh spacer material of nylon.
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B i o m a t e r i a l s
M o
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e s t e r : I I I
Artificial Kidney Dialysis Membrane
Hollow Fiber Membrane
Made up of hollow fibers
Each fibers have dimension of 255 and 285 um inside and outside diameter and
13.5 cm long.
Each unit contains about 11,000 hollow fibers.
The blood flows through the fibers while dialysate is passed outside of the
fibers
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Artificial Kidney Dialysis Membrane
The fibers can also be made from (soda-lime) glass which is made
porous by phase separation techniques.
Can be cleaned and sterilized.
Majority membranes are made up of cellophanes, which is derived
from cellulose.
Cupraphane
Visking