1. Prosthetic Biomaterials used in the ear
Mustafa and Hamel
Shelina
(Sam)
Megan
Amrita
Howard

2. Autografted ear Disadvantages Advantages
Lack of availability in chronically diseased ears
Prolonged operative time to obtain and shape the material
Resorption and/or loss of rigidity (especially with cartilage)
Possible fixation to the walls of the middle ear.
Very surgically intensive process
Advantages
Would not be rejected from the body or initiate a host response due to being formed from tissue from the body
Ear is able to distinguish sounds better

3. Artificial Tympanic Membrane
Tympanic membrane is a thin membrane that separates the external ear from the middle ear
Function to transmit sound from the air to the ossicles inside the middle ear
Rupture or perforations of the tympanic membrane leads to conductive hearing loss
A tympanic membrane prosthesis is:
Flat
Planar membrane sized to cover the perforation
Each mechanical fixation device has:
A sharp, piercing distal end,
An enlarged proximal end
A shaft.
Perforations can be due to infection or injuries to the ear. Childhood perforations are usually self healing. Symptoms of perforations are drainage from the ear canal, bloody discharge and loss of hearing. The first order of treatment include ear drops, antibiotics and ear powders. It usually heals after a few weeks.

4. TYMPANOPLASTY
Tissue is taken either from the back of the ear or from the small cartilaginous lobe of skin in front the ear called the tragus.
The tissues are thinned and dried.
An absorbable gelatin sponge is placed under the drum to allow for support of the graft.
The graft is then inserted underneath the remaining drum remnant and the drum remnant is folded back onto the perforation to provide closure.
Thin silastic sheeting is placed against the top of the graft to prevent it from sliding out of the ear
A small amount of Gelfoam is placed on the outside of the silastic to hold it into position in a sandwich type layer
If the perforation is very large an incision behind the ear is performed. This elevates the entire outer ear forward, gaining access to the perforation.
Once the hole is exposed fully, the perforated remnant is rotated forward, and the bones of hearing are inspected. There may be scar tissue and bands surrounding the bones of hearing.
Having identified the bones of hearing, the ossicular chain is pressed to determine if the chain is mobile and functioning. If the chain is mobile, then the remaining surgery concentrates on repairing the drum defect.
Tissue is taken either from the back of the ear or from the small cartilaginous lobe of skin in front the ear called the tragus. The tissues are thinned and dried. An absorbable gelatin sponge is placed under the drum to allow for support of the graft. The graft is then inserted underneath the remaining drum remnant and the drum remnant is folded back onto the perforation to provide closure.

5. Bone grafts for bone replacement in the ear:
Long standing perforations are more severe due to infection and degredation of the middle ear bones
Ossicular reconstruction at time of tympanoplasty
Decide if bone is replaced at time of operation
Bone degredation occurs at tip of incus
Connects to stapes
Prior infections prevent circulation to tip of bone
Wears away – no contact
Ossicular reconstruction can be performed in two ways…….

6. Bone grafts for bone replacement in the ear:
Small gap = bone or cartilage from tragus or behind ear
Large gap = incus bone removed
modelled into a tooth-like prosthesis
Re-inserted between stapes and malleus
Other options include:
T.O.R.P and P.O.R.P - titanium
Artificial strut – hydroxyapatitie
Porous so allows ingrowth of blood vessels and osseointegration
Less chance of rejection
Porous plastics
Rejection occured

7. Ossicular replacements...
Come into use in 3 cases:
Erosion or absence of the incus
Erosion or absence of the incus and malleus
Erosion or absence of the incus and stapes
Ear infections (Waddington disease).
Two types of replacement:
PORPs: Partial Ossicular Replacement Prosthesis (between oval window and eardrum)
TORPs: Total Ossicular Replacement Prosthesis (between ossicle chain and eardrum or oval window).
Erosion of these bones can occur due to ear infections, such as, Waddington disease: degradation of the bones leads to development of scar tissue, binding the bones together, fixing them in place.
TORPs span between the oval window and the ear drum, and PORPs between the end of an intact portion of the ossicle chain and either the eardrum or oval window

8. Requirements: Possible materials: Rigid Durable High density polymers
Hydroxyapatite
Stainless steel
Ceramic
Gelfoam – absorbable gelatin.
Rigid: to transmit sound but relatively low density to stiffness ratio.
Durable: Maintain properties and integrity for a long time.
Gelfoam: sterile compressed sponge
All these materials are brittle and rigid. Rigidity is desirable for acoustical purposes. Attempts were made to overcome the brittle nature by combining it with surgical grade rubber – very limited success.

9. Artificial Ear (Cochleal implant)
Disadvantages
The implantation process inevitably results in damage to nerve cells within the cochlea
Incapable of replicating the quality of sound processed by a natural cochlea
May be at higher risk for meningitis.
Advantages
Allows you to Hear
Permenant- (Dependant on Part Reliability)
Not just a Sound Amplifier (i.e. Hearing Aid)
Advantages
Not just A Sound Amplifier (i.e. Hearing Aid)
Disadvantages
The implantation process inevitably results in damage to nerve cells within the cochlea, which often results in a permanent loss of most residual natural hearing
The device can help the recipient better hear and understand sounds in their environment, it is simply incapable of replicating the quality of sound processed by a natural cochlea. As a result, some recipients can only distinguish the difference between simple sounds, such as a ringing phone vs a doorbell, while others can clearly understand speech in quiet environments. The success rate depends on a variety of factors, including technology used and condition of the recipient's cochlea.

10. Artificial Cochlea
The cochlea is the portion of the inner ear that senses sound vibrations and converts them into electrical signals that the auditory system can interpret.
An artificeal choclea replaces the function of damaged or removed cochlea.
They consist of a microelectromechanical-system (MEMS) which employs a frequency sensitive membrane immersed in fluid.
Different parts of the membrane vibrate depending of the frequency of the sound input this is then translated into a nervous signal that is passed into the auditory nerve.
The cochlea is the portion of the inner ear that senses sound vibrations and converts them into electrical signals that the auditory system can interpret
The cochlea is an example of active cellular mechanical forcing and structural processing in which the shape and physical composition of the sensory organ work in combination to accomplish a complex transform
The cochlea is a curled structure, which is filled with fluid that moves in response to the vibrations coming through the oval window from the middle ear. Along the length of the cochlea are thousands of hairs that are set in motion in the liquid at the resonance points of the incoming sound wave

11. Artificial Cochlea
Artificial cochlea: an example of structural processing
Prying Eyes: A MEMS-based artificial cochlea mimics the real thing in form and function.
By Robert Cravotta, Technical Editor -- EDN, 10/2/2008

12. References