Movements of the intact and reconstructed ossicular chain during changes in static pressure

Long-Term Hearing Results of Endoskeletal Ossicular Reconstruction in Chronic Ears Using Titanium Prostheses Having a Helical Coil: Part 1-Kraus K-Helix Crown, Incus to Stapes

OBJECTIVES

1) To assess long-term hearing results after endoskeletal ossicular chain reconstruction (eOCR) using the titanium Kraus K-Helix Crown prosthesis, implanted incus to stapes, with glass-ionomer cement (GIC) in chronic ears and 2) to determine safety of the prosthesis and cement.

STUDY DESIGN

Prospective, nonrandomized, sequential, single center, single surgeon.

SETTING

Private practice, ambulatory surgical center.

PATIENTS

N = 15 males (42%) and 21 females (58%). Mean age was 40.4 years (range, 6-81 years); 38 ears (22 right ears [58%] and 16 left ears [42%]).

INTERVENTIONS

eOCR in chronic ears. Comprehensive preoperative and postoperative hearing measurements were performed for up to 9 years.

MAIN OUTCOME MEASURES

Postoperative hearing results at 1 year showed statistically significant improvement as compared with preoperative hearing. Long-term hearing results remained stable and showed no statistically significant change over 9 years.

RESULTS

Estimated mean pure-tone air conduction average improved by 14.5 dB (95% confidence interval = 10.3-18.7). Estimated mean speech reception thresholds improved by 15.5 dB (10.8-20.2). Word recognition scores improved by -2.2% (-5.3 to 1.0). The estimated mean postoperative air-bone gap was 10.5 dB (7.2-13.8). The estimated mean calculated air-bone gap was 11.3 dB (8.0-14.5). The estimated mean change in high-tone bone conduction (HTBC) average was +3.5 dB (0.9-6.0). Two prostheses extruded (5%). No patients experienced any unanticipated serious adverse effects or events.

CONCLUSION

eOCR using the K-Helix Crown prosthesis, incus to stapes, and GIC can significantly improve hearing at 1 year and maintain stable hearing over 9 years. Both prosthesis and cement are safe.

Performance Evaluation of Coupling Variants for an Active Middle Ear Implant Actuator: Output, Conductive Losses, and Stability of Coupling With Ambient Pressure Changes

INTRODUCTION

This study aims to investigate the performance of an active middle ear implant actuator for various coupling configurations. Actuator output and conductive losses were measured, and the stability of coupling was evaluated by challenging the link between actuator and ossicles through pressure events in magnitudes that occur in daily life.

METHODS

Actuator coupling efficiency and the occurrence of conductive losses were measured in 10 temporal bones through laser Doppler vibrometry on the stapes footplate for various coupling types (incus short process with and without laser hole, incus long process, stapes head). To test the stability of coupling, actuator output was measured before and after daily-life pressure events that were simulated; Valsalva maneuvers (500 cycles of -40 to +60 hPa) and jumping into a swimming pool and diving 3 m deep (a step change of 300 hPa).

RESULTS

Actuator output was similarly high for all types of coupling to the incus (short process and long process) and most efficient for coupling to the stapes head. Conductive losses occurred in two temporal bones (TBs) for short process coupling but for seven TBs for coupling to the incus long process. All coupling types were stable and did not lose efficiency after pressure events in the low-frequency range (<1 kHz). Losses in output of 13 to 24 dB were observed in one TB at frequencies from 3 to 6 kHz.

CONCLUSION

Actuator output was similarly high for all types of coupling to the incus but coupling to the incus long process led to a higher occurrence of conductive losses. All three coupling configurations connected the actuator securely to the ossicular chain, under variations of barometric pressure that can be expected in daily life.

The motion of conventional and novel total ossicular replacement prostheses during changes in static pressure

Purpose

To investigate the motion of prostheses used to reconstruct ears with an absent stapes arch.

Study Design

We have studied the motion of conventional total ossicular replacement prostheses (TORPs) and a novel incusstapes replica prosthesis (ISRP), which connects the malleus head to the footplate, during changes in middle ear pressure (+400 to −400 dPa) in fresh human temporal bones using digital video clips and photographs. The pressure in the (sealed) external auditory meatus was varied using a manual tympanometer. The displacements of the prostheses in the medial to lateral plane have been measured using the dimensioning tool of Corel Draw.

Results

During changes in static pressure, TORPs move more in the lateral to medial plane than ISRPs. The motion of ISRPs is similar to that of the intact ossicular chain.

Conclusion

The ISRP design is less likely to damage the cochlea during changes in static pressure than a conventional TORP, but the maximum medial displacement of the TORPs studied was less than 0.1 mm.

The influence of incudostapedial joint separation on the middle ear transfer function

Objectives

One of the risks in middle ear surgery is high frequency hearing loss. It is believed that manipulations on the middle ear ossicles with the instruments may cause overstimulation of the inner ear and damage of the hear cells. Controversy arises whether temporary separation of the ossicles has any impact on middle ear transfer function and hearing threshold after surgery. The aim of the study is to evaluate the influence of incudostapedial joint (ISJ) separation on middle ear function in an experimental model.

Methods

With the use of single point laser Doppler vibrometer (LDV) stapes velocity in the intact chain and after ISJ separation was measured in 5 fresh human cadaver temporal bones.

Results

In all cases there was a decrease in stapes velocity after ISJ separation. Mead stapes velocity was reduced for 1 dB in 800 Hz to 9 dB in frequencies above 1,000 Hz. The decrease of velocity was greater in higher frequencies.

Conclusion

Separation of the ISJ does not reduce significantly the middle ear function.

Experimental measurement and modeling analysis on mechanical properties of incudostapedial joint

The incudostapedial (IS) joint between the incus and stapes is a synovial joint consisting of joint capsule, cartilage, and synovial fluid. The mechanical properties of the IS joint directly affect the middle ear transfer function for sound transmission. However, due to the complexity and small size of the joint, the mechanical properties of the IS joint have not been reported in the literature. In this paper, we report our current study on mechanical properties of human IS joint using both experimental measurement and finite element (FE) modeling analysis. Eight IS joint samples with the incus and stapes attached were harvested from human cadaver temporal bones. Tension, compression, stress relaxation and failure tests were performed on those samples in a micro-material testing system. An analytical approach with the hyperelastic Ogden model and a 3D FE model of the IS joint including the cartilage, joint capsule, and synovial fluid were employed to derive mechanical parameters of the IS joint. The comparison of measurements and modeling results reveals the relationship between the mechanical properties and structure of the IS joint.

[Vibrations of the human tympanic membrane measured with Laser Doppler Vibrometer]

The knowledge of the physiology of the normal ear is important to understand the function of the ear. It is especially crucial in the reconstruction of the destroyed ear to apply the knowledge of the normal ear. We present results of tympanic membrane vibrations measurements using Laser Doppler Vibrometer in human temporal bone specimens. Six temporal bone specimens were harvested within 48 hours of death and stored cooled until preparation. The preparation included mastoidectomy with posterior tympanotomy and partial resection of the facial nerve to visualize the stapes with its footplate. We measured velocity and displacement of each quadrant of the tympanic membrane and the umbo with the laser Vibrometer equipped with velocity and displacement decoders. The sensor head OFV-534 produced and read the reflected laser beam directed at a measured point with a dedicated micromanipulator attached to an operating microscope. A retro-reflective tape was used to enhance the reflection of the laser beam. Vibrations were induced by a acoustic stimulation at the tympanic membrane. The results of the measurements were corrected to a sound pressure in the external ear canal. Laser Doppler Vibrometer system allows an undisturbed measurement of vibrations in the middle ear. Posterior quadrants of the tympanic membrane have greater velocity and displacement than anterior quadrants in lower frequencies up to 2 kHz.

Middle ear admittance and hearing abnormalities in individuals with osteoarthritis

In osteoarthritis, the joint cartilage breaks down. Cartilage exists within the incudomalleolar and incudostapedial joints. In addition, the cartilage-covered base of the stapes footplate is bound to the cartilage-covered rim of the oval window by the annular ligament. Thus, higher prevalence of middle ear abnormalities and hearing loss can be expected in osteoarthritis due to degeneration of the cartilage and the subsequent abnormal repair response. In this study, tympanometric and audiometric data were obtained from 15 individuals diagnosed with osteoarthritis and 15 gender- and age-matched individuals without the diagnosis of arthritis. Results showed a significantly higher prevalence of middle ear abnormalities and hearing loss in ears with arthritis when compared to the control group. Interestingly, osteoarthritis and hearing loss are considered among the top chronic health concerns in older individuals although the connection between these two conditions has not been previously reported.

Hearing results with the titanium ossicular replacement prostheses

The purpose was to study the hearing results in patients receiving a Kurz titanium Bell partial ossicular replacement prosthesis (PORP) or an Aerial total ossicular replacement prosthesis (TORP). The study was a retrospective chart review in a tertiary otologic referral center. A computerized otologic database was used to identify 111 patients implanted with either a PORP or TORP prosthesis. Audiograms were reviewed and air-bone gaps were calculated for each patient. The improvement of the average air-bone gap (ABG) was 10.2 and 12.7 dB at 3 and 20 months after ossiculoplasty, respectively. Sixty-six percent of patients (73/111) had a postoperative air-bone gap of 20 dB or less. The ABG for the titanium PORP prosthesis was 14.3+/-9.7 dB, compared with 25.2+/-13.7 dB for the TORP prosthesis (P <0.05). The ABG to within 20 dB or less was obtained in the PORP group in 77% of the cases, versus 52% of the cases in the TORP group (P <0.05). Two extrusions of the prostheses were observed at 17 and 20 months after surgery (1.8%). Revision procedures for functional failure were carried out in 20 patients (18%). The rate of sensorineural hearing loss was 3.6%. The major factors influencing good audiometric results were the surgical procedure preserving the external auditory canal and the presence of the stapes. The best hearing results were achieved when a PORP was used in an intact canal wall (ICW) procedure, and the worst hearing results were achieved when a TORP was used in a canal wall down (CWD) procedure. The titanium Kurz prosthesis has been an effective implant at our institution for ossicular reconstruction.