Middle ear mechanics of cartilage tympanoplasty evaluated by laser holography and vibrometry.
OBJECTIVE
To assess the effects of thickness and position of cartilage used to reconstruct the tympanic membrane (TM) using a novel technique, time-averaged laser holography.


BACKGROUND
Cartilage is commonly used in TM reconstruction to prevent formation of retraction pockets. The thickness, position, and shape of the cartilage graft may adversely affect TM motion and hearing. We sought to systematically investigate these parameters in an experimental setting.


METHODS
Computer-assisted optoelectronic laser holography was used in 4 human cadaveric temporal bones to study sound-induced TM motion for 500 Hz to 8 kHz. Stapes velocity was measured with a laser Doppler vibrometer. Baseline (control) measurements were made with the TM intact. Measurements were repeated after a 0.5- or 1.0-mm-thick oval piece of conchal cartilage was placed on the medial TM surface in the posterior-superior quadrant. The cartilage was rotated so that it was either in contact with the bony tympanic rim and manubrium or not.


RESULTS
At frequencies less than 4 kHz, the cartilage graft had only minor effects on the overall TM fringe patterns. The different conditions had no effects on stapes velocity. Greater than 4 kHz, TM motion was reduced over the grafted TM, both with 0.5- and 1.0-mm-thick grafts. No significant differences in stapes velocity were seen with the 2 different thicknesses of cartilage compared with control.


CONCLUSIONS
Computer-assisted optoelectronic laser holography is a promising technique to investigate middle ear mechanics after tympanoplasty. Such positioning may prevent postoperative TM retraction. These findings and conclusions apply to cartilage placed in the posterior-superior TM quadrant.
Aarnisalo
Antti A
AA
Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA. antti.aarnisalo@hus.fi
Cheng
Jeffrey T
JT
Ravicz
Michael E
ME
Hulli
Nesim
N
Harrington
Ellery J
EJ
Hernandez-Montes
Maria S
MS
Furlong
Cosme
C
Merchant
Saumil N
SN
Rosowski
John J
JJ
D000161:Acoustic Stimulation; D000368:Aged; D000369:Aged, 80 and over; D002102:Cadaver; D003627:Data Interpretation, Statistical; D004425:Ear Cartilage / Q000502:physiology / Q000601:surgery*; D004432:Ear, Middle / Q000502:physiology / Q000601:surgery*; D005260:Female; D006696:Holography / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D017078:Laser-Doppler Flowmetry; D008297:Male; D008875:Middle Aged; D013506:Otologic Surgical Procedures; D013199:Stapes / Q000502:physiology; D013701:Temporal Bone; D014432:Tympanic Membrane / Q000601:surgery*; D014732:Vibration