Influence of the Coupling on the Hearing Outcome After Implantation of an Active Middle Ear Implant: Comparison of the Transmission Behavior in Temporal Bone Experiments With Clinical Data.

OBJECTIVES: The active middle ear implant, Vibrant Soundbridge (VSB), can be implanted with a variety of couplers. Hearing outcome after implantation has been investigated in both temporal bone (TB) experiments and patient studies, but the relationship between experimental and clinical data is still weak in the literature. Therefore, experimental data from TB experiments should be compared with patient data in a retrospective study, in which the floating mass transducer is used with couplers of the third generation. Actuator coupling structures included the long (LP coupler) and short (SP coupler) incus process, the stapes head (Clip coupler), and the round window membrane (RW soft coupler). METHODS: In the TB experiments, the sound transmission after vibroplasty on the above-mentioned actuator coupling structures was determined in 32 specimens by means of laser Doppler vibrometry on the stapes footplate. Data of 69 patients were analyzed. The main target audiometric parameters were the postoperative aided word recognition score (WRS) in the free field at 65 dB SPL (WRS 65 dB in %), the preoperative and postoperative pure-tone average (PTA4, including the frequencies 0.5, 1, 2, and 4 kHz) of the bone conduction hearing threshold (PTA4BC), the aided postoperative air conduction hearing threshold in the free field (PTA4FF) and the direct threshold (Vibrogram) at least 6 months postoperatively. The coupling efficiency of the actuator (Vibrogram-PTA4BC) as well as the effective hearing gain (PTA4FF-PTA4BC) was compared between the couplers. RESULTS: The analysis in the main speech range (0.5-4 kHz) indicated that in the TB experiments, the LP coupler tends to have the best coupling quality at low frequencies (500-1000 Hz). This was up to 15 dB above the worst actuator (RW soft coupler). However, the results missed the significance level ( p > 0.05). In the high frequencies (2000-4000 Hz), the Clip coupler showed the best coupling quality. This was 15 dB above the worst actuator (SP coupler). However, the results missed the significance level ( p > 0.05), too. The postoperative WRS at 65 dB SPL and the postoperative PTA4FF were independent of the actuator coupling structure. The PTA4BC was stable at 6 months postoperatively. For the PTA4 of the coupling efficiency, there were no significant differences between the actuator coupling structures (LP 8.9 dB ± 12.9; SP 9.5 ± 6.5 dB; Clip 5.2 ± 10.5 dB; RW 12.7 ± 11.0 dB). However, the tendential inferiority of the RW soft coupler with regard to transmission in the low-frequency range and the tendential superiority of the Clip coupler in the high-frequency range that have already been displayed experimentally could be confirmed in the clinical results. However, the clinical results missed the significance level, too ( p > 0.05). CONCLUSIONS: In vivo, there are no significant differences in the postoperative outcome stratified according to coupling the target structure. The differences known from the experimental setting were repressed by individual biasing factors. However, to ensure sufficient postoperative speech intelligibility, the frequency-specific transmission behavior of the couplers should be taken into account when setting the indication for VSB implantation.

Virtual Quality Control in Middle Ear Surgery: Is Image-guided Tympanoscopy a Valuable Tool for Depicting Borderline Situations?

HYPOTHESIS: Before modern imaging was introduced, revision surgery was the only way to evaluate possible reasons for inadequate improvement in hearing after ossicular replacement during reconstructive middle ear surgery. BACKGROUND: The aim of this study was to evaluate freely navigable virtual tympanoscopy using different computed tomographic modalities. We compared cone-beam computed tomography (CBCT), flat panel computed tomography (FPCT), and conventional computed tomography in helical mode (CTH), volume mode (CTV), and ultra high resolution mode (CTD). METHODS: Four temporal bone specimens were reconstructed with partial or total ossicular replacement prostheses. The best functional results for prosthetic coupling were achieved under the control of laser Doppler vibrometry (LDV). Afterward, a progressive step-by-step decoupling of the prostheses was carried out. Different prosthesis positions were evaluated by LDV as well as different computed tomographic modalities with 3D reconstruction of each dataset. RESULTS: Anatomical structures were better depicted and the best position and coupling of inserted prostheses were achieved using CBCT. All imaging techniques could be used to control the position of middle ear prostheses, but CBCT provided the highest resolution and the best image quality in both 2D and 3D reformations and in 3D-animated video representation. CONCLUSION: Compared with several other imaging modalities, CBCT was best at depicting miscellaneous coupling problems. Noninvasive detection of coupling problems caused by minimal loss of contact between prostheses and middle ear ossicles will influence the clinical outcome. This early detection will help to determine whether revision surgery is needed.

Fully Implantable Active Middle Ear Implants After Subtotal Petrosectomy With Fat Obliteration: Preliminary Clinical Results.

OBJECTIVES: In patients with chronic middle ear disease, especially after revision surgery for ventilation problems and mixed hearing loss, active middle ear implants may provide an alternative treatment option. The fully implantable active middle-ear implant (FI-AMEI) is designed for implantation in a ventilated mastoid with an intact posterior canal wall. Until now, there have been no reports on audiometric results after implantation of a FI-AMEI in a fat-obliterated cavity after subtotal petrosectomy (SPE). STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Twelve patients were included after numerous previous tympanoplasty surgeries for severe mixed hearing loss and FI-AMEI implantation. INTERVENTION: In five patients, the FI-AMEI was implanted in a cavity, with fat obliteration, after SPE. Seven patients received FI-AMEI implantation after intact canal wall (ICW) surgery. MAIN OUTCOME MEASURE(S): Audiometric results (pure-tone audiometry, Freiburger monosyllables) are demonstrated for 12 patients after an observation period of 3 months. RESULTS: The improvement in monosyllable score was 40 to 85% for the 12 patients. Free-field-aided thresholds showed high heterogeneity. CONCLUSION: FI-AMEI implantation combined with SPE provides an alternative approach to hearing rehabilitation to non-FI-AMEI implantation. Studies with a high number of patients and long-term observation periods are necessary to statistically verify these results.

Sensor-actuator component for a Floating Mass Transducer-based fully implantable hearing aid.

We propose a novel system based on the Floating Mass Transducer (FMT) to be used as the active component of a fully implantable, Vibrant Soundbridge-like middle ear implant. The new system replaces the external microphone used in the currently available design with an implantable piezoelectric sensor that is inserted into the incudostapedial joint and picks up the vibrations transmitted to the long process of the incus. The FMT is coupled to the round window of the cochlea. We characterize the system by measuring the gain in intracochlear sound pressure using laser Doppler vibrometry at a surgically installed "third window" into the cochlea of six temporal bones. Closed-loop feedback oscillations limit the system's available output. We show that using an adaptive control algorithm, a mean functional gain of up to 40 dB is achieved, which is similar to Soundbridge functional gain. The concept matches the FMT's one-point fixation philosophy and offers several advantages over other designs, namely an easy and time-efficient surgery, reversibility of implantation, and natural hearing for the prospective patient.

Function, Applicability, and Properties of a Novel Flexible Total Ossicular Replacement Prosthesis With a Silicone Coated Ball and Socket Joint.

HYPOTHESIS: A total ossicular replacement prosthesis (TORP) with a silicone coated ball and socket joint (BSJ) is able to compensate pressure changes and therefore provide better sound transmission compared with rigid prostheses. BACKGROUND: Dislocation and extrusion are known complications after TORP reconstruction, leading to revisions and recurrent hearing loss. Poor aeration of the middle ear, scar tension, and static pressure variations in conjunction with rigid prosthesis design causes high tension at the implant coupling points. METHODS: A novel TORP prototype with a silicone coated BSJ has been developed. Experimental measurements were performed on nine fresh cadaveric human temporal bones of which five were used for a comparison between rigid TORP and flexible TORP tympanoplasty. The middle ear transfer function was measured at ambient pressure and at 2.5 kPa, both positive and negative pressure, applied in the ear canal. RESULTS: The flexible TORP design yields a better transmission of sound after implantation and at negative pressure inside the tympanic cavity, compared with rigid TORP. In average, it provides an equivalent sound transfer like the intact middle ear. At positive pressure, the flexible TORP performs slightly worse. Both performed worse than the intact middle ear, which is related to an uplifting of the prostheses. CONCLUSION: The findings may be considered preliminary as this experimental study was limited to just one of the many different possible situations of tympanoplasty and it involved a small sample size. Nevertheless, the results with the flexible TORP were promising and could encourage further investigations on such prostheses.

Impact of Prosthesis Length on Tympanic Membrane's and Annular Ligament's Stiffness and the Resulting Middle Ear Sound Transmission.

HYPOTHESIS: Prosthesis' length creates tension in ossicular reconstructions, which directly effects the middle ear sound transmission. BACKGROUND: Relatively long prostheses are often used to stabilize the middle ear reconstruction to prevent dislocation. Thereby, tension on the flexible components such as the tympanic membrane (TM) and the annular ligament (AL) is increased. Only little is known on the amount of displacement-related stiffening of the TM and AL, as well as the consecutive reduction in middle ear transfer function (METF). METHODS: An expandable total ossicular replacement prosthesis was tensionfree inserted in nine cadaveric temporal bones between the malleus handle and the stapes footplate. Upon heat activation the prosthesis was lengthened, thus inducing tension on the reconstruction. The METF was assessed before and after elongation. TM's and AL's stiffness were determined by measuring their force-displacement characteristics. RESULTS: Upon activation the prostheses were elongated between 50 and 200 µm. A frequency-dependent METF reduction was measured with a decrease of 5 to 25 dB below 1.0 kHz. At frequencies >2.0 kHz the reduction was less prominent or the METF showed even an improvement of up to 10 dB. TM's stiffness remained constant during the elongation-induced displacement, whereas the AL's stiffness increased. The METF reduction below 1.0 kHz correlated with the increasing AL's stiffness. CONCLUSION: Tension has a significant impact on the METF after middle ear reconstruction. As little tension as possible should be used to enable best sound transmission. Stabilization of prosthesis should be achieved with dislocation devices to ensure secure coupling to the ossicular remnants without creating additional tension.

Fully implantable hearing aid in the incudostapedial joint gap.

A fully implantable hearing aid is introduced which is a combined sensor-actuator-transducer designed for insertion into the incudostapedial joint gap (ISJ). The active elements each consist of a thin titanium membrane with an applied piezoelectric single crystal. The effectiveness of the operating principle is verified in a temporal bone study. We also take a closer look at the influence of an implantation-induced increase in middle ear stiffness on the transducer's output. An assembly of the transducer with 1 mm thickness is built and inserted into six temporal bones. At this thickness, the stiffness of the annular ligament is considerably increased, which leads to a loss in functional gain for the transducer. It is assumed that a thinner transducer would reduce this effect. In order to examine the performance for a prospective reduced pretension, we increased the gap size at the ISJ by 0.5 mm by removing the capitulum of the stapes in four temporal bones. The TM is stimulated with a broadband multisine sound signal in the audiological frequency range. The movement of the stapes footplate is measured with a laser Doppler vibrometer. The sensor signal is digitally processed and the amplified signal drives the actuator. The resulting feedback is minimized by an active noise control least mean square (LMS) algorithm which is implemented on a field programmable gate array. The dynamic range and the functional gain of the transducer in the temporal bones are determined. The results are compared to measurements from temporal bones without ISJ extension and to the results of Finite Elements Model (FE model) simulations. In the frequency range above 2 kHz a functional gain of 30 dB and more is achieved. This proposes the transducer as a potential treatment for high frequency hearing loss, e.g. for patients with noise-induced hearing loss. The transducer offers sufficient results for a comprehensive application. Adaptations in the transducer design or surgical approach are necessary to cope with ligament stiffening issues. These cause insufficient performance for low frequencies under 1 kHz.

Hearing outcome after sequential cholesteatoma surgery.

The objective of this study was to assess hearing outcome after sequential cholesteatoma surgery stratified for exclusively transcanal technique (ETC), combined transcanal and transmastoidal technique (TCM) and canal wall down surgery (CWD) and to analyze the impact of ossicular reconstruction technique (partial ossicular replacement prostheses/PORP and total ossicular replacement prostheses/TORP) on hearing outcome. This study is a retrospective case review and clinical case study conducted in a tertiary referral center. Patients who underwent 376 cholesteatoma surgeries (2007-2009) and 92 ears in clinical re-examination at least 12 months postoperatively were included. Sequential cholesteatoma surgery with ETC, TCM, or CWD; ossiculoplasty with PORP or TORP were the interventions administered. Pre- and postoperative air-bone gap (ABG) and air conduction threshold (AC) for 0.5-3 kHz were the main outcome measures. Overall, the mean preoperative ABG decreased from 25.3 ± 1.3 to 19.8 ± 0.9 dB with a mean ABG closure of 5.4 ± 1.3 dB (p ≤ 0.001). According to surgical technique, the postoperative ABG after CWD 23.5 ± 2.1 was significantly worse compared to ETC (17.3 ± 1.0 dB, p < 0.05) and TCM (19.4 ± 1.3 dB). A significant ABG closure was observed after ETC (6.8 ± 2.0 dB, p < 0.01) and TCM (6.5 ± 2.0 dB, p < 0.01) contrary to CWD (2.1 ± 2.9 dB, p > 0.05). Patients receiving PORP showed a significantly less ABG postoperatively (19.0 ± 0.9 dB, p ≤ 0.05) compared to the TORP group (24.1 ± 2.5 dB). However, a significant hearing gain was assessed after PORP- (4.7 ± 1.6 dB, p ≤ 0.01) and TORP- implantation (10.4 ± 3.7 dB, p ≤ 0.01). Sequential cholesteatoma surgery allowed for an excellent hearing outcome postoperatively. An intact posterior canal wall and a present stapes suprastructure were identified to predict a significantly superior hearing result. In addition to the technical and prosthetic considerations, the audiological outcome was confounded by the attending middle ear pathology.

Health-related quality of life measurement after cholesteatoma surgery: comparison of three different surgical techniques.

The objective of this study was to compare health-related quality of life (HRQOL) after sequential cholesteatoma surgery including exclusively transcanal technique (ETC), combined transcanal transmastoidal technique (TCM) and canal wall down surgery with obliteration (CWD). It was a clinical case study conducted in a tertiary referral center. 97 patients at least 12 months after cholesteatoma surgery were included. Interventions included sequential cholesteatoma surgery with ETC, TCM or CWD; ossiculoplasty with partial and total ossicular replacement prostheses. HRQOL assessed by Chronic Otitis Media Outcome Test 15 including an overall score and three subscores ('ear symptoms', 'hearing function' and 'mental health') as well as a general evaluation of HRQOL and the frequency of physician consultations, audiometric outcome related to HRQOL were the main outcome measures. Patients, who had undergone sequential cholesteatoma surgery, showed moderate restrictions in HRQOL postoperatively. Stratified for the three surgical techniques, patients receiving ETC tended to report lower restrictions in HRQOL. The ETC group offered a significantly lower value in the subscore 'ear symptoms'. The 'hearing function' was attributed to be the most restriction criteria for all techniques. The overall score and all subscores correlated moderately with the postoperative air conduction threshold. The strongest correlation coefficient was achieved for the subscore 'hearing function' (r(s) = 0.49, p < 0.001). Sequential cholesteatoma surgery offers acceptable moderate restrictions in HRQOL postoperatively. Patients receiving canal wall down surgery with obliteration showed equivalent limitations in HRQOL compared to closed techniques (ETC, TCM). The postoperative air conduction threshold was shown not to be a sufficient indicator for HRQOL. Therefore, disease-specific validated and reliable measuring instruments for HRQOL should be transferred from clinical research to clinical practice to provide an individualized postoperative assessment after cholesteatoma surgery.

Cholesteatoma recidivism: comparison of three different surgical techniques.

OBJECTIVE: To compare cholesteatoma recidivism rates after exclusive transcanal technique (ETC), combined transcanal and mastoidal technique (TCM, both subsets of intact canal wall technique, ICW), and canal wall down surgery (CWD). STUDY DESIGN: Retrospective case review and clinical case study SETTING: Tertiary referral center. PATIENTS: 406 cholesteatoma surgeries (2007-2009), 116 ears in clinical re-examination at least 1 year postoperatively. INTERVENTION: Sequential cholesteatoma surgery with ETC, TCM, or CWD. MAIN OUTCOME MEASURES: Cholesteatoma recidivism, residual and recurrent disease, localization of recidivism, validity of clinical findings. RESULTS: Out of 406 patients, ETC was performed in 227 (56%), TCM in 122 (30%), and CWD in 57 (14%) cases. Recidivism rates after ICW (15%) and CWD (16%) were almost similar. Recidivism was more frequent after ETC (11%) than after TCM (25%). Residuals were observed in 2% after ETC, 6.5% after TCM, and 7% after CWD. Incidence of recurrent disease was 9% for ETC, 18% for TCM, and 9% for CWD. Preferred localization of recidivism was the tympanic cavity after ETC (92%) and CWD (56%) and the mastoid cavity after TCM (53%). The clinical re-examination showed no further recidivistic disease. CONCLUSIONS: Sequential surgery is an effective and successful strategy in cholesteatoma eradication, providing a similar recidivism rate compared to following cholesteatoma retrograde and resection of the posterior canal wall. Lower recidivism after ETC was observed as a consequence of limited disease and the postoperative middle ear status determined the higher rate of recurrence after TCM. Therefore, the restricted visualization of the middle ear during ICW surgery does not increase the rate of recidivism, compared with CWD, as described in other studies. Cholesteatoma recidivism is mainly attributed to the surgeon's experience that outweighs the chosen strategy.

The ostrich middle ear for developing an ideal ossicular replacement prosthesis.

The aim of the study was to investigate the validity of the avian middle ear model for researching the tympanoplasty mechanics. We studied the morphological details, acoustic transmission and quasi-static behavior of the ostrich tympano-ossicular system. The stained specimens of the ostrich middle ear were examined under a light microscope. The sound transfer function and quasi-static performance of the ostrich middle ear were evaluated using laser Doppler vibrometry. The application of pressure to the tip of the extracolumella causes a buckling movement of the ossicle between the cartilaginous and bony parts. Histologically, the intracolumellar connection can be identified as a junction zone between bone and hyaline cartilage. Sound conduction through the human middle ear is less effective than it is through the ostrich middle ear. The greatest difference (35 dB) was observed in the low-frequency region. Because the extracolumella bends, the medial displacements of the eardrum were not fully transmitted to the footplate. The amplitude of the ostrich columella footplate quasi-static medial displacements significantly exceeded that of the human footplate in both intact and reconstructed middle ears. The ostrich middle ear is a suitable model for designing total ossicular replacement implants. The main protective mechanism in the ostrich middle ear under quasi-static stress is a buckling movement of the extracolumella. The total ossicular prostheses of the new generation should contain an elastic element that allows an adaptation to greater quasi-static eardrum movements.

Influence of the middle ear anatomy on the performance of a membrane sensor in the incudostapedial joint gap.

There is a great demand for implantable microphones for future generations of implantable hearing aids, especially Cochlea Implants. An implantable middle ear microphone based on a piezoelectric membrane sensor for insertion into the incudostapedial gap is investigated. The sensor is designed to measure the sound-induced forces acting on the center of the membrane. The sensor mechanically couples to the adjacent ossicles via two contact areas, the sensor membrane and the sensor housing. The sensing element is a piezoelectric single crystal bonded on a titanium membrane. The sensor allows a minimally invasive and reversible implantation without removal of ossicles and without additional sensor fixation in the tympanic cavity. This study investigates the implantable microphone sensor and its implantation concept. It intends to quantify the influence of the sensor's insertion position on the achievable microphone sensitivity. The investigation considers anatomical and pathological variations of the middle ear geometry and its space limitations. Temporal bone experiments on a laboratory model show that anatomical and pathological variations of the middle ear geometry can prevent the sensor from being placed optimally within the incudostapedial joint. Beyond scattering of transfer functions due to anatomic variations of individual middle ears there is the impact of variations in the sensor position within the ossicular chain that has a considerable effect on the transfer characteristics of the middle ear microphone. The centering of the sensor between incus and stapes, the direction of insertion (membrane to stapes or to incus) and the effect of additional contact points with surrounding anatomic structures affect the signal yield of the implanted sensor. The presence of additional contact points has a considerably impact on the sensitivity, yet the microphone sensitivity is quite robust against small changes in the positioning of the incus on the sensor. Signal losses can be avoided by adjusting the position of the sensor within the joint. The findings allow the development of an improved surgical insertion technique to ensure maximally achievable signal yield of the membrane sensor in the ISJ and provides valuable knowledge for a future design considerations including sensor miniaturization and geometry. Measurements of the implanted sensor in temporal bone specimens showed a microphone sensitivity in the order of 1 mV/Pa. This article is part of a special issue entitled "MEMRO 2012".

New total ossicular replacement prostheses with a resilient joint: experimental data from human temporal bones.

HYPOTHESIS: New flexible total ossicular prostheses with an integrated microjoint can compensate for large static displacements in the reconstructed ossicular chain. When properly designed, they can mimic the function of the joints of the intact chain and ensure good vibration transfer in both straight and bent conditions. BACKGROUND: Prosthesis dislocations and extrusions are frequently observed after middle ear surgery. They are mainly related to the altered distance between the coupling points because of large static eardrum displacements. METHODS: The new prostheses consist of 2 titanium shafts, which are incorporated into a silicone body. The sound transfer function and stapes footplate displacement at static loads were evaluated in human temporal bones after ossicular reconstruction using prostheses with 2 different silicones with different hardness values. The stiffness and bending characteristics of the prostheses were investigated with a quasi-static load. RESULTS: The sound transfer properties of the middle ears with the prostheses inserted under uncompressed conditions were comparable with those of ears with intact ossicular chains. The implant with the soft silicone had improved acoustic transfer characteristics over the implant with the hard silicone in a compressed state. In the quasi-static experiments, the minimum medial footplate displacement was found with the same implant. The bending characteristics depended on the silicone stiffness and correlated closely with the point and angle of the load incidence. CONCLUSION: The titanium prostheses with a resilient joint that were investigated in this study had good sound transfer characteristics under optimal conditions as well as in a compressed state. As a result of joint bending, the implants compensate for the small changes in length of the ossicular chain that occur under varying middle ear pressure. The implants require a stable support at the stapes footplate to function properly.

Osseointegration of titanium prostheses on the stapes footplate.

The success of middle ear reconstructive surgery depends on stable coupling between the prosthesis and residual ossicles. To establish a stable fixed point on the stapes footplate for subsequent prosthesis reconstruction, a titanium footplate anchor was coated with osteoinductive substances to induce a controlled osseointegration on the footplate. Various studies have shown that collagen-based matrices with and without bone growth and differentiation factors can induce and enhance bone formation and consequently increase implant stability. The ears of 23 one-year-old Merino sheep (n = 46) were divided into five groups and implanted with a specially designed footplate anchor. The surface of each implant was modified by applying a collagenous matrix (collagen I or II) either with immobilized bone morphogenic protein (BMP-4) or transforming growth factor-ss, respectively, to stimulate osteoblastic activation and differentiation on the stapes footplate with subsequent osseointegration. Polychrome labeling was used to assess new bone formation and remodeling during the study. After study termination on day 84, synchrotron radiation-based computed microtomography and histomorphometry were used to identify bone implant contact. Eight implants showed radiographical and/or histological evidence of integration by newly formed bone. An osseointegration could histologically be proven in two of these eight specimens, and additional ectopic bone formations were seen in another 21 specimens. In all animals, bone turnover on the footplate was proven by polychrome labeling. This study proves the general ability to induce a controlled osseointegration of titanium implants biologically activated with artificial extracellular matrices on their surfaces on the stapes footplate in a mammalian organism.

Partial ossicular reconstruction: comparison of three different prostheses in clinical and experimental studies.

OBJECTIVE: To compare the reconstruction results of a long incus process defect using 3 different partial ossicular replacement prostheses (PORP). STUDY DESIGN: Temporal bone experiments and retrospective case review. SETTING: Tertiary referral center. EXPERIMENTAL MATERIAL AND PATIENTS: The experimental study was performed on 18 temporal bones; 66 patients with retraction pockets, chronic otitis media with or without cholesteatoma. INTERVENTIONS: Ossiculoplasty using 3 different PORP: titanium angle prosthesis, autologous incus interposition, and titanium clip prosthesis. MAIN OUTCOME MEASURES: Laser Doppler vibrometry in temporal bones measured transmission properties of the PORP. Patients were retrospectively assessed up to 5 years after surgery. Audiologic data were analyzed for preoperative and postoperative air conduction and air-bone gap at 0.5, 1, 2, 3, and 4 kHz. Statistical analyses compared the outcome in the experimental and clinical setting. RESULTS: Experimentally, the titanium PORP showed similar transmission properties because the overall difference to the intact specimen was -4.14 +/- 0.59 dB for the titanium angle prosthesis and -4.61 +/- 0.57 dB for the titanium clip prosthesis. The transmission after an autologous incus interposition was significantly worse (-9.32 +/- 0.39 dB, p < or = 0.001) compared with the other prostheses. Patients' mean postoperative air-bone gap was 25.5 +/- 1.2 dB and less than 20 dB in at least 66% of cases without any significant differences between the groups. CONCLUSION: In the clinical setting, the confounding factors that influence the acoustic outcome after partial ossiculoplasty obscure the prosthesis-related transmission factors that can otherwise be derived in the experimental setting. The results do not generally favor the use of 1 specific prosthesis, rather they suggest that the correct choice of a prosthesis be based on the anatomic and pathophysiologic conditions found in the individual patient.

Laser Doppler vibrometry of the middle ear in humans: derivation dependence, variability, and bilateral differences.

OBJECTIVE: Derivation dependence, inter- and intrasubject/intertest variability, bilateral differences of the eardrum vibration characteristics have been investigated using laser Doppler vibrometry (LDV). MATERIAL AND METHODS: A total of 31 normally hearing adults were examined. In each subject, both ears were consecutively stimulated by the chirp acoustic stimulus that covered 500-3700-Hz frequencies. The laser beam was directed to and the reflection was consecutively picked up from the tympanic membrane surface. RESULTS: LDV curves derived from different eardrum loci possessed dissimilar characteristics. The derivation area dependence was particularly apparent for the stimulus frequency constituents above 1500 Hz. The intersubject variability of LDV parameters exceeded the intrasubject/intertest one. The intersubject divergences looked selectively distinct for the frequencies over 2000 Hz. Under repeated recordings, LDV parameters remained stable. The intertest differences, if appeared, concerned predominantly the magnitudes of separate frequency bands. LDV waveforms registered by experienced and beginner investigators were alike. Bilaterally derived LDV curves regularly differed from each other. In individual cases, the bilateral divergences approximated the intersubject deviation. CONCLUSIONS: The derivation area on the eardrum should be taken into account when estimating the actual LDV recording. Over repeated recordings in separate individuals, LDV waveforms are stable while the experience of investigator has slight if any influence on the principal LDV characteristics. Due to bilateral differences in the middle ear transfer function, in LDV testing of the ear suspected to the pathology, LDV recording from the opposite healthy ear could hardly be taken as an appropriate reference sample.