How does closure of tympanic membrane perforations affect hearing and middle ear mechanics? An evaluation in a patient cohort and temporal bone models.

OBJECTIVE: This study aimed to determine how tympanic membrane (TM) perforations and their closure, using a paper-patch technique, affect middle-ear mechanics and, thus, conductive hearing for different sizes of the TM perforation. STUDY DESIGN: Temporal bone (TB) study and prospective clinical trial. SETTING: Tertiary referral center. PATIENTS: Nine patients with chronic otitis media for more than 3 months. INTERVENTION: The TM perforations were closed with a paper patch in all 9 patients. In 5 of 9 patients, myringoplasty was performed. Matching TM perforations were created in a TB model (n = 8) and closed using the paper patch. MAIN OUTCOME MEASURES: Air-bone gap was measured in all 9 patients of the patient cohort with TM perforations before and after closure and in 5 patients after myringoplasty. Stapes velocity and sound pressure difference between the ear canal and middle-ear cavity were measured in TBs with intact TM, with TM perforations, and with the perforations closed by the paper patch. All measurements in the patient cohort and TBs were performed for different sizes of TM perforations to determine if the effects varied as a function of size. RESULTS: Degree of the air-bone gap differed as a function of size of the TM perforations and its recovery after closure, and myringoplasty was independent of the size of the TM perforation in the frequency range of 0.25 to 4 kHz. In the TB measurements, although pressure difference across the TM was almost fully recovered by closing the perforation with a paper patch, recovery of the stapes motion was limited at frequencies above 4.5 kHz for larger sizes of TM perforations. CONCLUSION: Hearing loss caused by TM perforations depends on the size of the perforation. Hearing returns almost completely across the frequency range after closure except above 4 kHz for larger perforations. This is because the structural damage caused by large TM perforations cannot be completely restored by application of a paper patch.

The influence of postoperative tissue formation on sound transmission after stapes surgery.

In the surgical treatment of otosclerosis, the coupling between the stapes prosthesis and the long process of the incus is critical. After surgery, connective tissue and mucosa may grow over the coupling area and thereby influence the sound transmission properties of the incus-prosthesis interface. It was the hypothesis of this study that tissue ongrowth in the incus-prosthesis interface has little influence on sound transmission following stapes surgery. The goals of the study were to: (1) investigate the extent of postoperative tissue ongrowth over the stapes prosthesis; (2) objectively evaluate intra- and postoperative sound transmission properties of revision stapes surgery and compare the findings to those from primary surgery; (3) quantify the influence of ongrown tissue on sound transmission after stapes surgery. A group of 10 patients undergoing revision stapes surgery was investigated with audiological evaluations and intraoperative laser Doppler interferometry, and with scanning electron microscopy of the explanted incus with its adherent prosthesis in 6 patients. Results were compared to a group of patients undergoing primary otosclerosis surgery and temporal bone experiments. Results indicated that tissue grows over the prosthesis, as identified in all specimens. Sound transmission properties were evaluated intraoperatively (i.e., incus mobility and prosthesis-fixation quality), and found to correlate well with the functional hearing results. Ongrowing mucosa in the incus-prosthesis interface had only a minimal effect on sound transmission properties and cannot compensate adequately for insufficient prosthesis fixation. Therefore, it is essential that the stapes prosthesis is properly fixed during primary otosclerosis surgery.

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.

¿Qué sabemos de otoesclerosis? aspectos anatomopatológicos / What do we know about otosclerosis? anatomo-pathological aspects

La otoesclerosis es una enfermedad que produce hipoacusia de conducción por un proceso de remodelación ósea denominado otoespongiosis. Se han estudiado aspectos anatomopatológicos para evaluar el foco de inicio, y las características de este proceso llamado otoespongiosis. Nos motivó a realizar este estudio el deseo de conocer qué pasaba en nuestra población, clasificar las observaciones anatomopatológicas, relacionar estos aspectos microscópicos con aspectos clínicos como: tiempo de evolución clínica y aspecto macroscópico de la platina. Para esto se realizó un estudio prospectivo tomando todos los pacientes operados de estapedostomía en el Hospital Clínico de la Universidad de Chile desde octubre 2003 a octubre 2004. Fueron un total de 22 pacientes que se agruparon en 4 subgrupos según su aspecto anatomopatológico. Este estudio mostró que la otoesclerosis es más frecuente en mujeres en la quinta década de vida, en el oído derecho y presenta un tiempo de evolución clínica promedio de 7 años, que no varía con el grado de otoespongiosis de la supraestructura del estribo. Se observó un 45 por ciento de otoespongiosis en los huesecillos estudiados, aspecto no descrito en la bibliografía. No se observó correlación entre el aspecto microscópico y macroscópico de la platina, lo que sugiere otros focos de otoespongiosis o un avance rápido desde la fissula antefenestra a las cruras del estribo. Se continuará este estudio aumentando la muestra y realizando un seguimiento a los pacientes para relacionar el resultado anatomopatológico y el resultado auditivo post-estapedostomía.

[Biomaterial studies in cultures of human stapedial bone-like cells]. / Untersuchung unterschiedlicher Biomaterialien in einer Knochenzellkultur des menschlichen Steigbügels.

BACKGROUND: Cell culture studies may provide information on the behavior of biomaterials in the intended implant environment. Cell cultures from such an environment could be used for the development of middle ear implants. MATERIAL AND METHODS: Secondary bone-like cell cultures derived from human stapes were exposed to different materials [Al(2)O(3) ceramic, glass ceramic (Ceravital), gold and titanium]. Proliferation was studied for up to 40 days. RESULTS: The proliferation of cultured stapes bone-like cells did not differ significantly between the four tested biomaterials. The well known cytotoxic effect of copper, which was used as a control, was evident. CONCLUSIONS: Four biomaterials [Al(2)O(3) ceramic, glass ceramic (Ceravital), gold and titanium] have similar biocompatibility and no toxicity when tested in human stapes cell cultures. This in vitro model may be of considerable value for the further development of middle ear implants, e.g., when coated with bone morphogenetic proteins.

Evaluation of a cement incus replacement prosthesis in a temporal bone model.

In reconstruction of the ossicular chain for a damaged incus, it is important that the incus replacement prosthesis (IRP) length is ideal in order to provide optimal tension between the tympanic membrane or malleus and stapes head to achieve the best post-operative hearing result. Even though the length of commercially available IRPs can be adjusted, it still may be difficult to achieve clinically. We describe experiments in a human temporal bone model using dental cement as an IRP after removal of the incus. This cement IRP (CIRP) hardens in situ and becomes the length of the gap to be spanned so that tension should be ideal. Two different CIRPs were studied; one was a conventional rod-type CIRP connecting either the umbo or mid-malleus handle to the stapes head. The second was a Y-shaped CIRP (Y-CIRP), connecting two sites on the malleus to the stapes head. The wide Y-CIRP connected the malleus head and umbo to the stapes head, while the narrow Y-CIRP connected the malleus neck and mid-handle to the stapes head. The acoustic performance of these experimental CIRPs was studied using a laser Doppler vibrometer system in 12 fresh human temporal bones. The CIRP demonstrated better acoustic performance than conventional IRPs studied previously in the same model. While all the CIRPs showed similar function below 2.0 kHz, the narrow Y-CIRP appeared best above 3.0 kHz. A prosthesis of this type may have an acoustic advantage over conventional IRPs.

Acoustic input impedance of the stapes and cochlea in human temporal bones.

The acoustic input impedance of the stapes and cochlea ZSC represents the mechanical load driven by the tympanic membrane, malleus and incus. ZSC was calculated from broad-band measurements (20 Hz to 11 kHz) of stapes displacement made with an optical motion sensor and of sound pressure at the stapes head in a human temporal-bone preparation. Measurements were made in 12 fresh temporal bones with the round window insulated from the sound stimulus. Below 1 kHz, the magnitude of ZSC was approximately inversely proportional to frequency, and ZSC angle was between 0.10 and -0.20 periods. This behavior is consistent with a mixed stiffness and resistance. Between 1 and 4 kHz, ZSC was resistance-dominated with a magnitude between 40 and 100 mks acoustic G omega that was roughly independent of frequency, and its angle was between -0.12 and 0 periods. Between 4 and 7 kHz, the magnitude of ZSC was either constant or increased with frequency while ZSC angle was near 0. Between 7 and 8 kHz, both ZSC magnitude and angle decreased sharply with frequency, and both increased somewhat at higher frequencies. The input impedance of the cochlea ZC was estimated in one ear from ZSC measurements made before and after draining the inner ear fluids. ZC was stiffness-dominated below 100 HZ, and resistance-dominated from 100 Hz to 5 kHz. The frequency-dependent magnitude of ZSC in our bones is similar to those reported by other investigators in cadaver temporal bones (Nakamura et al., 1992; Kurokawa and Goode, 1995). Our ZSC measurements are qualitatively similar to theoretical predictions (Zwislocki, 1962; Kringlebotn, 1988), but are a factor of 3 greater in magnitude, implying that ZSC may be more resistive and stiffer than previously thought. We found inter-ear variations of a factor of 4 (12 dB), which may explain some of the clinically observed variations in size of the air bone gap in individuals with middle ear lesions or after middle-ear reconstructive surgery.

Otospongiosis: morphologic and microchemical investigation after NaF-treatment.

Element analysis of microareas of otospongiotic specimens is described. A total of 36 otospongiotic stapes are ultrasectioned without decalcification and examined using a transmission and a scanning electron microscopy (STEM-mode). The latter was equipped with an energy dispersive x-ray analyzer. Twenty of the stapes came from patients who have had sodium fluoride (NaF) treatment (15 to 45 mg/day) for a minimum of 12 months. The otospongiotic stapes are classified as spongiotic and sclerotic according to their pathologic characteristics and state of mineralization. Using the Ca/P ratio as criterion--measured by the characteristic x-ray fluorescence--it was shown in a blind study that the NaF-treated otospongiotic stapes had a statistically higher Ca/P ratio, indicating that the fluoride may stabilize otospongiotic lesions, particularly the spongiotic type with unstable mineralization.