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Prosthetic Biomaterials used in the ear

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

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Prosthetic Biomaterials used in the ear

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

  2. Autografted ear 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 Disadvantages • 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

  3. 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. http://www.freepatentsonline.com/6309419.html Artificial Tympanic Membrane

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

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

  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 http://upload.wikimedia.org/wikipedia/commons/b/b8/Ear.jpg http://www.earsurgery.org/tympan.html

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

  8. Requirements: • Rigid • Durable • Possible materials: • High density polymers • Hydroxyapatite • Stainless steel • Ceramic • Gelfoam – absorbable gelatin. http://www.ghorayeb.com/OSSICULARRECONSTRUCTION.html http://illumin.usc.edu/article.php?articleID=19&page=2

  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)

  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.

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

  12. References • http://www.earsurgery.org/tympan.html

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