Prosthetic Prosthetic Biomaterials Biomaterials

used in the earused in the earMustafa and HamelMustafa and Hamel

ShelinaShelina(Sam)(Sam)MeganMeganAmritaAmritaHowardHoward

Autografted earAutografted earDisadvantagesDisadvantages Lack of availability in Lack of availability in

chronically diseased chronically diseased earsears

Prolonged operative Prolonged operative time to obtain and time to obtain and shape the material shape the material

Resorption and/or loss Resorption and/or loss of rigidity (especially of rigidity (especially with cartilage) with cartilage)

Possible fixation to Possible fixation to the walls of the the walls of the middle ear.middle ear.

Very surgically Very surgically intensive processintensive process

AdvantagesAdvantages Would not be rejected Would not be rejected

from the body or from the body or initiate a host initiate a host response due to being response due to being formed from tissue formed from tissue from the bodyfrom the body

Ear is able to Ear is able to distinguish sounds distinguish sounds betterbetter

Artificial Tympanic Artificial Tympanic MembraneMembrane

Tympanic membrane is a thin Tympanic membrane is a thin membrane that separates the membrane that separates the external ear from the middle external ear from the middle earear

Function to transmit sound Function to transmit sound from the air to the ossicles from the air to the ossicles inside the middle earinside the middle ear

Rupture or perforations of the Rupture or perforations of the tympanic membrane leads to tympanic membrane leads to conductive hearing lossconductive hearing loss

A tympanic membrane A tympanic membrane prosthesis is:prosthesis is:

FlatFlat Planar membrane sized to Planar membrane sized to

cover the perforationcover the perforation Each mechanical fixation Each mechanical fixation

device has: device has: A sharp, piercing distal end, A sharp, piercing distal end, An enlarged proximal endAn enlarged proximal end A shaft. A shaft.

http://www.freepatentsonline.com/http://www.freepatentsonline.com/6309419.html6309419.html

TYMPANOPLASTYTYMPANOPLASTY

Tissue is taken either from the back of Tissue is taken either from the back of the ear or from the small cartilaginous the ear or from the small cartilaginous lobe of skin in front the ear called the lobe of skin in front the ear called the tragus. tragus.

The tissues are thinned and dried. The tissues are thinned and dried. An absorbable gelatin sponge is placed An absorbable gelatin sponge is placed

under the drum to allow for support of under the drum to allow for support of the graft. the graft.

The graft is then inserted underneath the The graft is then inserted underneath the remaining drum remnant and the drum remaining drum remnant and the drum remnant is folded back onto the remnant is folded back onto the perforation to provide closure. perforation to provide closure.

Thin silastic sheeting is placed against Thin silastic sheeting is placed against the top of the graft to prevent it from the top of the graft to prevent it from sliding out of the earsliding out of the ear

A small amount of Gelfoam is placed on A small amount of Gelfoam is placed on the outside of the silastic to hold it into the outside of the silastic to hold it into position in a sandwich type layerposition in a sandwich type layer

http://www.earsurgery.org/tympan.html

Bone grafts for bone Bone grafts for bone replacement in the ear:replacement in the ear:

Long standing perforations are Long standing perforations are more severe due to infection and more severe due to infection and degredation of the middle ear degredation of the middle ear bonesbones Ossicular reconstruction at Ossicular reconstruction at

time of tympanoplastytime of tympanoplasty

Decide if bone is replaced at time Decide if bone is replaced at time of operationof operation

Bone degredation occurs at tip of Bone degredation occurs at tip of incusincus Connects to stapesConnects to stapes Prior infections prevent Prior infections prevent

circulation to tip of bonecirculation to tip of bone Wears away – no contactWears away – no contact

Ossicular reconstruction can be Ossicular reconstruction can be performed in two ways…….performed in two ways…….

http://www.tonmeister.ca/main/textbook/node319.html

Bone grafts for bone Bone grafts for bone replacement in the ear:replacement in the ear:

Small gap = bone or cartilage Small gap = bone or cartilage from tragus or behind earfrom tragus or behind ear

Large gap = incus bone removedLarge gap = incus bone removed modelled into a tooth-like modelled into a tooth-like

prosthesisprosthesis Re-inserted between stapes and Re-inserted between stapes and

malleusmalleus

Other options include:Other options include: T.O.R.P and P.O.R.P - titaniumT.O.R.P and P.O.R.P - titanium Artificial strut – hydroxyapatitieArtificial strut – hydroxyapatitie

Porous so allows ingrowth of Porous so allows ingrowth of blood vessels and blood vessels and osseointegrationosseointegration

Less chance of rejectionLess chance of rejection Porous plasticsPorous plastics

Rejection occuredRejection occured

http://www.earsurgery.org/tympan.html

http://upload.wikimedia.org/wikipedia/commons/b/b8/Ear.jpg

Ossicular replacements...Ossicular replacements...Come into use in 3 cases:Come into use in 3 cases: Erosion or absence of the incusErosion or absence of the incus Erosion or absence of the incus Erosion or absence of the incus

and malleusand malleus Erosion or absence of the incus Erosion or absence of the incus

and stapesand stapesEar infections (Waddington Ear infections (Waddington

disease).disease).

Two types of replacement:Two types of replacement:PORPs: Partial Ossicular PORPs: Partial Ossicular

Replacement Prosthesis Replacement Prosthesis (between oval window and (between oval window and eardrum)eardrum)

TORPs: Total Ossicular TORPs: Total Ossicular Replacement Prosthesis Replacement Prosthesis (between ossicle chain and (between ossicle chain and eardrum or oval window). eardrum or oval window).

http://illumin.usc.edu/article.php?articleID=19&page=3

Requirements:Requirements: RigidRigid DurableDurable

Possible materials:Possible materials: High density High density

polymerspolymers Hydroxyapatite Hydroxyapatite Stainless steel Stainless steel CeramicCeramic Gelfoam – Gelfoam –

absorbable gelatin.absorbable gelatin.http://www.ghorayeb.com/OSSICULARRECONSTRUCTION.html

http://illumin.usc.edu/article.php?articleID=19&page=2

Artificial Ear (Cochleal Artificial Ear (Cochleal implant)implant)

AdvantagesAdvantages

Allows you to Allows you to HearHear

Permenant- Permenant- (Dependant on (Dependant on Part Reliability)Part Reliability)

Not just a Sound Not just a Sound Amplifier (i.e. Amplifier (i.e. Hearing Aid)Hearing Aid)

DisadvantagesDisadvantages The implantation The implantation

process inevitably process inevitably results in damage results in damage to nerve cells to nerve cells within the cochleawithin the cochlea

Incapable of Incapable of replicating the replicating the quality of sound quality of sound processed by a processed by a natural cochleanatural cochlea

May be at higher May be at higher risk for meningitis. risk for meningitis.

Artificial CochleaArtificial Cochlea The cochlea is the portion of the inner ear that senses The cochlea is the portion of the inner ear that senses

sound vibrations and converts them into electrical signals sound vibrations and converts them into electrical signals that the auditory system can interpret.that the auditory system can interpret.

An artificeal choclea replaces the function of damaged or An artificeal choclea replaces the function of damaged or removed cochlea.removed cochlea.

They consist of a microelectromechanical-system (MEMS) They consist of a microelectromechanical-system (MEMS) which employs a frequency sensitive membrane immersed which employs a frequency sensitive membrane immersed in fluid.in fluid.

Different parts of the membrane vibrate depending of the Different parts of the membrane vibrate depending of the frequency of the sound input this is then translated into a frequency of the sound input this is then translated into a nervous signal that is passed into the auditory nerve.nervous signal that is passed into the auditory nerve.

Artificial CochleaArtificial Cochlea

http://a330.g.akamai.net/7/330/2540/20080924145228/www.edn.com/contents/images/20eyes1LG.jpg

ReferencesReferences

http://www.earsurgery.org/tympan.hhttp://www.earsurgery.org/tympan.htmltml