Måns Eeg-Olofsson

Stability, survival, and tolerability of a novel baha implant system: six-month data from a multicenter clinical investigation

Objective: Determination of the difference in implant stability between a novel Baha implant system (test) and the previous-generation implant system (control). Methods: In an open, randomized, prospective multicenter clinical investigation, 77 adult patients with Baha implants were included. Test and control implants were randomly assigned in proportions of 2:1. Implant stability quotient (ISQ) values were recorded using resonance frequency analysis at the time of implantation and at 10 days, at 4, 6, 8, and 12 weeks, and at 6 months after surgery. Skin reactions were evaluated according to the Holgers classification. Sound processor fitting was performed from 6 weeks after implantation. Results: Significantly higher mean ISQ values, measured between 0 and 6 months, were obtained for test compared to control implants (70.4 versus 65.4, p < 0.0001). Statistically significant differences were obtained for the study population as a whole and for the subgroup of patients loaded at 6 ± 1 weeks after implant surgery (63.6% of patients). Up to 12 weeks, Holgers rates were comparable, whereas at 6 months, more skin reactions (Grades 1 and 2) were observed in the control implant group. No reduction in mean ISQ values was observed after implant loading. Conclusion: The test implant showed higher mean ISQ values at the time of placement and over time. The level of osseointegration reached with the implants in adults as early as 6 weeks after implantation was sufficient to support the sound processor. The test implant system is expected to provide additional benefits related to the improvement of the degree of osseointegration, especially for patients with thin or compromised bone.

Transmission of bone-conducted sound in the human skull measured by cochlear vibrations

One limitation with the Bone Anchored Hearing Aid (Baha®) is too poor amplification for patients with moderate to severe sensorineural hearing losses. Therefore, we investigated if bone conducted (BC) sound transmission improves when the stimulation approaches the cochlea. Also the influence from the squamosal suture on BC sound transmission was investigated. Both sides of the heads on seven human cadavers were used and vibrational stimulation was applied at eight positions on each side with a frequency range of 0.1–10 kHz. A laser Doppler vibrometer was used to measure the resulting velocity of the cochlear promontory. It was found that the velocity of the promontory increases as the stimulation position approaches the cochlea; this was especially apparent at distances within 2.5 cm from the ear canal opening and when the stimulation position was in the opened mastoid. At frequencies above 500 Hz there was on average 10 to 20 dB greater vibrational response at the cochlea when the stimulation was close to the cochlea compared with the normal Baha® position. Moreover, even if there were general indications of attenuation of BC sound when passing the squamosal suture, an effect from the suture could not be conclusively determined.

Percutaneous versus transcutaneous bone conduction implant system: a feasibility study on a cadaver head.

Objective: Percutaneous bone-anchored hearing aid (BAHA) is an important rehabilitation alternative for patients who have conductive or mixed hearing loss. However, these devices use a percutaneous and bone-anchored implant that has some drawbacks reported. A transcutaneous bone conduction implant system (BCI) is proposed as an alternative to the percutaneous system because it leaves the skin intact. The BCI transmits the signal to a permanently implanted transducer with an induction loop system through the intact skin. The aim of this study was to compare the electroacoustic performance of the BAHA Classic-300 with a full-scale BCI on a cadaver head in a sound field. The BCI comprised the audio processor of the vibrant sound bridge connected to a balanced vibration transducer (balanced electromagnetic separation transducer). Methods: Implants with snap abutments were placed in the parietal bone (Classic-300) and 15-mm deep in the temporal bone (BCI). The vibration responses at the ipsilateral and contralateral cochlear promontories were measured with a laser Doppler vibrometer, with the beam aimed through the ear canal. Results: Results show that the BCI produces approximately 5 dB higher maximum output level and has a slightly lower distortion than the Classic-300 at the ipsilateral promontorium at speech frequencies. At the contralateral promontorium, the maximum output level was considerably lower for the BCI than for the Classic-300 except in the 1-2 kHz range, where it was similar. Conclusion: Present results support the proposal that a BCI system can be a realistic alternative to a BAHA.

A novel bone conduction implant (BCI): Engineering aspects and pre-clinical studies

Abstract Percutaneous bone anchored hearing aids (BAHA) are today an important rehabilitation alternative for patients suffering from conductive or mixed hearing loss. Despite their success they are associated with drawbacks such as skin infections, accidental or spontaneous loss of the bone implant, and patient refusal for treatment due to stigma. A novel bone conduction implant (BCI) system has been proposed as an alternative to the BAHA system because it leaves the skin intact. Such a BCI system has now been developed and the encapsulated transducer uses a non-screw attachment to a hollow recess of the lateral portion of the temporal bone. The aim of this study is to describe the basic engineering principals and some preclinical results obtained with the new BCI system. Laser Doppler vibrometer measurements on three cadaver heads show that the new BCI system produces 0–10 dB higher maximum output acceleration level at the ipsilateral promontory relative to conventional ear-level BAHA at speech frequencies. At the contralateral promontory the maximum output acceleration level was considerably lower for the BCI than for the BAHA. Sumario Los auxiliares auditivos anclados al hueso (BAHA) en forma percutánea son hoy en día una alternativa importante de rehabilitación para pacientes que sufren de pérdidas auditiva conductivas o mixtas. A pesar de su éxito, ellos se asocian con algunos problemas, tales como infecciones de la piel, pérdida accidental o espontánea del implante óseo, o el rechazo del paciente al tratamiento por razones de estigma. Se ha prop-uesto un novedoso sistema de implante de conducción ósea (BCI) que deja la piel intacta, como una alternativa al sistema BAHA. El sistema de BCI ha sido ya desarrollado y el transductor encapsulado utiliza una unión sin tornillo a un receso hueco en la porción lateral del hueso temporal. El objetivo de este estudio es describir los principios básicos de ingeniería y algunos resultados pre-clínicos obtenidos con el nuevo sistema BCI. Mediciones con un vibrómetro Laser Doppler sobre tres cabezas de cadáver muestran que el nuevo sistema BCI produce un nivel más alto de aceleración máxima de salida de 0–10 dB en el promontorio ipsilateral, en relación con el BAHA convencional a la altura del oído, en las frecuencias del lenguaje. En el promontorio contralateral, el nivel máximo de aceleración de salida fue considerablemente más bajo para el BCI que para el BAHA.

New developments in bone-conduction hearing implants: a review

The different kinds of bone-conduction devices (BCDs) available for hearing rehabilitation are growing. In this paper, all BCDs currently available or in clinical trials will be described in categories according to their principles. BCDs that vibrate the bone via the skin are referred to as skin-drive devices, and are divided into conventional devices, which are attached with softbands, for example, and passive transcutaneous devices, which have implanted magnets. BCDs that directly stimulate the bone are referred to as direct-drive devices, and are further divided into percutaneous and active transcutaneous devices; the latter have implanted transducers directly stimulating the bone under intact skin. The percutaneous direct-drive device is known as a bone-anchored hearing aid, which is the BCD that has the largest part of the market today. Because of some issues associated with the percutaneous implant, and to some extent because of esthetics, more transcutaneous solutions with intact skin are being developed today, both in the skin-drive and in the direct-drive category. Challenges in developing transcutaneous BCDs are mostly to do with power, attachment, invasiveness, and magnetic resonance imaging compatibility. In the future, the authors assume that the existing percutaneous direct-drive BCD will be retained as an important rehabilitation alternative, while the transcutaneous solutions will increase their part of the market, especially for patients with bone-conduction thresholds better than 35 dB HL (hearing level). Furthermore, the active transcutaneous direct-drive BCDs appear to be the most promising systems, but to establish more detailed inclusion criteria, and potential benefits and drawbacks, more extensive clinical studies are needed.

Implications for contralateral bone conducted transmission as measured by cochlear vibrations

Hypothesis: The velocity response at the contralateral cochlea from bone-conducted (BC) stimulation depends on the stimulation position. Background: BC sound transmission in the human skull is complex and differs from air-conducted sound. BC sound stimulates both cochleae with different amplitudes and time delays influencing hearing perception in a way that is not completely understood. One important parameter is the stimulation position on the human skull. Method: By applying BC stimulation at 8 positions on both sides of 7 human cadaver skulls, the contralateral velocity response of the cochlear promontory was investigated in the frequency range of 0.1 to 10 kHz. Using previous data from ipsilateral stimulation, the transcranial transmission (TT) and effects of bilateral stimulation to one cochlea was calculated. Results: The contralateral transmission from the 8 positions showed small differences, but the TT showed a generally increased cochlear separation when the stimulation position approached the cochlea. The effect of simultaneous bilateral stimulation was calculated, showing a low-frequency negative effect for correlated signals, whereas uncorrelated signals gave 3-dB gain. At higher frequencies, there was less interaction of the combined stimulation because of the greater intercochlear separation. Also, the greatest time difference between ipsilateral transmission and contralateral transmission was at positions close to the cochlea. Conclusion: The stimulation position only slightly affects the amplitude and phase of the contralateral cochlear velocity response. However, because of the great influence from the ipsilateral transmission, a position close to the cochlea would be beneficial for patients with bilateral BC hearing aids.

Transmission of bone conducted sound - Correlation between hearing perception and cochlear vibration

The vibration velocity of the lateral semicircular canal and the cochlear promontory was measured on 16 subjects with a unilateral middle ear common cavity, using a laser Doppler vibrometer, when the stimulation was by bone conduction (BC). Four stimulation positions were used: three ipsilateral positions and one contralateral position. Masked BC pure tone thresholds were measured with the stimulation at the same four positions. Valid vibration data were obtained at frequencies between 0.3 and 5.0 kHz. Large intersubject variation of the results was found with both methods. The difference in cochlear velocity with BC stimulation at the four positions varied as a function of frequency while the tone thresholds showed a tendency of lower thresholds with stimulation at positions close to the cochlea. The correlation between the vibration velocities of the two measuring sites of the otic capsule was high. Also, relative median data showed similar trends for both vibration and threshold measurements. However, due to the high variability for both vibration and perceptual data, low correlation between the two methods was found at the individual level. The results from this study indicated that human hearing perception from BC sound can be estimated from the measure of cochlear vibrations of the otic capsule. It also showed that vibration measurements of the cochlea in cadaver heads are similar to that measured in live humans.

The Bone Conduction Implant-First Implantation, Surgical and Audiologic Aspects.

Objective To report on preoperative assessment, surgery, and audiologic outcome of the first patient implanted with the bone conduction implant (BCI). Background The BCI is a bone conduction hearing device with an intact skin solution where the transducer is implanted close to the ear canal opening. By avoiding a percutaneous screw attachment to the skull, the BCI is anticipated to reduce complications associated with the Bone-Anchored Hearing Aid (BAHA) solution. Methods The first patient to receive a BCI was a 42-year-old woman with a unilateral mixed hearing loss due to tympanosclerosis. Preoperative and postoperative cone beam computed tomography and a virtual planning tool for 3D reconstruction were used to optimize and control the position of the BCI in the mastoid. The transducer was placed in a 5-mm deep seating in the mastoid and secured with a titanium bar. Free field tone and speech audiometry were conducted to evaluate the audiologic outcome at baseline (1 month postoperatively) and 1 month after baseline. Results The BCI was placed in the position according to the preoperative 3D planning. On average, the tone thresholds improved by 30 dB, speech reception thresholds by 25.5 dB and speech signal-to-noise ratio by 9.7 dB. The surgical procedure was considered simple and safe. Conclusion The BCI can be implanted by a safe and easy surgical procedure. 3D preoperative planning can be helpful to optimize the BCI position. The BCI is a realistic alternative to the BAHA.

Long-term stability, survival, and tolerability of a novel osseointegrated implant for bone conduction hearing: 3-year data from a multicenter, randomized, controlled, clinical investigation

Objective To compare the 3-year stability, survival, and tolerability of 2 osseointegrated implants for bone conduction hearing: a wide 4.5-mm-diameter moderately roughened implant with a rounded 6-mm abutment (test) and a 3.75-mm diameter as-machined implant with a conically shaped 5.5-mm abutment (control). Study Design In this randomized, prospective, controlled, multicenter clinical study, 77 adult patients were included. Test and control implants were randomly assigned in proportions of 2:1. The implants were loaded with the sound processor from 6 weeks postimplantation. Follow-up after surgery was conducted at 10 days; at 4, 6, 8, and 12 weeks; and at 6, 12, 24, and 36 months after surgery. At every visit, implant stability quotient (ISQ) values were recorded by means of resonance frequency analysis (RFA), and skin reactions were evaluated according to Holgers’ classification. Results Statistically significantly higher mean ISQ values were recorded for the test implant compared with the control implant at each evaluation time point. Between 2 and 3 years after surgery, ISQ values decreased but remained above baseline values. Implant survival was high for both implants: 96.2% of the test implants and 100% of the control implants survived these 3 years. Statistically significantly improved soft tissue outcomes were observed in the test implant group. Conclusion This extensive long-term clinical investigation demonstrated that the test implant is more stable in terms of ISQ-values and provides high tolerability for the soft tissue. The results show that implant loading at 6 weeks is safe.

Bone conduction hearing sensitivity in normal-hearing subjects: Transcutaneous stimulation at BAHA vs BCI position

Abstract Objective: Bone conduction (BC) stimulation closer to the cochlea has previously been shown to give higher cochlear promontory acceleration measured by laser Doppler vibrometry (LDV). This study is investigating whether stimulation closer to the cochlea also gives improved hearing sensitivity. Furthermore, the study compares shifts in hearing sensitivity (BC thresholds) and ear-canal sound pressure (ECSP). Design: BC hearing thresholds and ECSP have been measured for stimulation at two positions: the existing bone-anchored hearing aid (BAHA) position, and a new bone conduction implant (BCI) position that is located closer to the cochlea. Study sample: The measurements were made on 20 normal-hearing subjects. Results: Depending on frequency, the ipsilateral hearing threshold was 3–14 dB better, and the ipsilateral ECSP was 2–12 dB higher for the BCI than for the BAHA position, with no significant differences between threshold and ECSP shifts at group level for most frequencies, and individually only for some subjects. Conclusions: It was found that both the objective ECSP and the subjective hearing threshold measurements gave similar improvement as previous LDV measurements for stimulation closer to the cochlea. One exception was that the LDV measurements did not show the improved sensitivity for frequencies below 500 Hz found here.