Stability, long term survival and tolerability of a novel Baha® implant system, a multi-centre investigation.

The Baha® system is an implant for patients with typical conductive or mixed
(conductive and sensoneural) hearing loss. In principle; a titanium fixture,
which is integrated with the bone tissue of the skull, is connected to an
external vibrating unit via a skin penetrating abutment. The vibrator is
transforming sound into vibrations, which is conducted via the titanium fixture
to the skull and onwards to the hearing organ, the cochlea.
Today, the fixture is a standard Brånemark type of implant, which initially was
developed by Nobel Pharma AB, which later became Entific medical systems AB and
was bought by Cochlear Ltd. There is a clear connection to dental implants
although, the Baha® system are subjected to less stress and must use much
shorter fixtures (typically 4 mm long).

As there has been substantial development of titanium fixtures for the dental
industry, there are good reasons for improving the Baha® implant system.
The standard Baha® implant is a class IIb medical device and the new
modifications will not change the classification.
There are mainly two modifications to the new implant system. First, a change
of design, which distributes the load on the bone better.
The second modification is the surface topography of the fixture. A
modification resulting in a moderately rough surface is achieved. The
modification method used has been used with excellent clinical results in
dental practice for more than 10 years. There is no reason to believe that the
fixture in the Baha® application should react adverse to that.
An improved fixture can allow earlier loading. Today, 12 weeks are recommended
to achieve good osseointegration. In clinical routine care a shorter period
then the 12 weeks are often used though. With the new system the 12 week period
can probably be significantly shortened. The novel fixture will most likely
have a better stability and an improved long-term survival.
The new Baha® implant system is to all knowledge and considerations an
improvement without any increased patient risk. To fully evaluate the new
system, a randomized clinical trial will be done.

Primary Objective:
To show superiority of the novel fixtures compared to standard fixtures
regarding stability of the implants measured as ISQ values.

Secondary Objectives:
1. To compare the long time survival of the standard fixtures and abutments
with the novel fixtures and abutments in the Baha system.
2. To compare safety of the standard fixtures with the novel fixtures measured
as local reactions and Adverse Events and Adverse Device Effects. These events
will be recorded as local reactions at the implant site and any adverse events.
3. To support loading of Baha sound processor at 6 weeks post implant.

The bone anchored hearing implant (Baha®) has been used clinically for about 30
years and some 35.000 patients have been fitted with the system. The Baha® is a
hearing implant used for patients with conductive, sensorineural or mixed
hearing loss.

A central issue to bone anchored hearing implants (Baha®) is that the titanium
fixture is properly integrated with the skull bone. This integration is often
referred to as osseointegration where outermost titanium dioxide (TiO2) layer
is biochemically bonded to calcium phosphate of the bone.

Similar to the advancements in dental implant technology, there are some
improvements that can be incorporated in the Baha® implant system. The two main
improvements we are focusing on is A) a design with better load bearing
properties and B) a surface topography of the fixture with better
osseointegrating abilities. The suggested modifications will, according to
state of the art science as well as clinical experience, improve the success
rate for the patients and introduce an option for earlier loading of the sound
processor.

The hypothesis is that there is a difference in stability between the novel
implant and the standard/control implant. The implant stability is measured by
a Resonance Frequency Analysis.
The novel implants and the standard/control implants will be randomised in
blocks of 3 in the proportions 2:1.

The patient must meet the following criteria to be included; adult patients,
i.e. >=18 years, written informed consent, eligible for the Baha system, bone
thickness at the implant site of at least 4 mm, eligible for implantation with
the two fixtures; 3,75 alternatively 4,5 mm wide, no known disease or treatment
that compromises / will compromise the bone quality at the implant site.

The investigation is designed as an open, multi-centre, randomised,
comparative, prospective long term investigation.
The timetable for the study will be 10 patient follow-up visits 10 days, 4, 6,
8, 12 weeks and 6, 12, 24 and 36 months after fixture insertion.The total study
time will be 3,5 year including patient enrollment period.

The comparator is a standard 4,0 mm titanium fixture and abutment in the Baha
system.
Test Product: The test product is the novel fixture and abutment for the Baha
system developed by Cochlear BAS AB.
In the study 72 patients will be enrolled at 4 clinics. The aim will be 66
evaluable patients.

The insertion of the novel fixture will essentially be similar to the
conventional Baha fixture insertion.
The test device (fixture and abutment pre-mounted) will be inserted with the
abutment inserter. In case of need for abutment removal, a counter torque
wrench is used together with standard screwdriver unigrip 95mm.
Since the new fixture is slightly wider, a wider hole must be drilled using
accompanying drill set.
A healing cap with new dimensions will be used during the healing period.
RFA measurements will be done from time 0, visit 1, and onwards. The RFA
measurements will be done with the abutment in place.

Risks involved in this study are related to the novel design of the fixture and
abutment that 2 of 3 patients will receive. The standard system is known to be
well tolerated and to have a good survival rate; 94%. The novel design changes
are not expected to be less well tolerated then the standard design of the
fixture and the abutment. The titanium surface used for the novel fixture and
abutment is a well known surface for dental applications, it has a slightly
modified topography compared with the standard fixture and abutment.
Therefore, it is not foreseen that the novel design will increase the risk for
the patient relative to the standard system. The new Baha implant system is to
all knowledge and considerations an improvement without any increased patient
risk. Follow up is done regularly and in the case of untoward events the
patients are encouraged to contact the clinic. The patients will be provided
with contact details.

The novel fixture and implant have been developed to provide a fixture and
abutment that performs better over time, i.e. has greater stability, less
reactions locally and has a higher survival rate. If this is the case then this
will be a benefit for the 2 thirds of the patients allocated to the novel
system. The study will have regular and more standardised follow-up then
conventional care. Otherwise there will be no treatment benefits for the
patients.

An interimanalysis is planned after 6 months.
Feedback of research results will be communicated to the participants and other
interested persons in a coprehensible way.

I the patient information leaflet all necessary information to the participants
will be presented, included risks and study plan.
The participant will give a written consent and will keep copies of both the
information sheet and the consent.

The novel design changes are not expected to be less well tolerated then the
standard design of the fixture and the abutment. The titanium surface used for
the novel fixture and abutment is a well known surface, which has a slightly
modified topology compared with the standard fixture and abutment. Therefore,
it is not foreseen that the novel design will increase the risk for the patient
relative to the standard system.

The most likely risk is that an infection could occur in the interface between
the skin and the implant. Very rarely such infections lead to implant loss.
Most often these infections are successfully treated.
During the study follow-up period this and other possible adverse effects will
be investigated carefully. The patients are encouraged to contact the
investigator if any problems occur in between the planned visits.
The study follows the standard procedures for a Baha implantation.