Clinical and health economic evaluation with a new Baha® abutment design combined with a minimally invasive surgical technique

1 Clinical experience with Baha
Bone conduction implants (BCI) such as the Baha® system were first clinically
described in 1977 by Tjellström et al., and since then more than 80.000
patients have been treated with this technique. The Baha system consists of a
titanium implant, which is integrated with the bone tissue of the skull and is
connected to an external sound processor via a skin penetrating abutment. The
sound processor transforms sound to vibrations that are transmitted via the
abutment and titanium implant to the skull bone and then to the cochlea. This
provides hearing amplification for patients who experience profound hearing
loss for various reasons and who are unable to benefit from a conventional
hearing aid.

2 The surgical procedure
The surgical procedures that are currently used for Baha surgery make use of a
dermatome or scalpel techniques (e.g. linear or C-shaped incisions) to remove
subcutaneous tissue down to the periosteum, thus creating a thin, hair-free
skin flap. The rationale for skin thinning is to reduce the mobility of the
skin surrounding the abutment to minimise the risk for infection or other local
skin reactions.
Despite extensive soft tissue reduction, the most common complications
associated with Baha implants are related to adverse skin reactions around the
abutment. The reduction of the skin also adds complexity to the surgical
procedure that is otherwise a routine type of skin incision. A less invasive
surgical technique avoiding reducing the thickness of the skin would render a
simpler and shorter procedure and would be aesthetically appealing to the
patients, as permanent hair removal in the area around the abutment would not
be required. Faster healing and less numbness (sensory loss/ paraesthesia at
the implant site may also be expected if the soft tissue thickness is left
intact. Recent published investigations have indicated that good outcomes may
be achieved using surgical procedures without skin thinning.

3 Abutment design and materials
Findings in the literature indicate that soft tissue stability may be improved
by the use of improved abutment designs and/or improved materials.
In order to remove the need to perform soft tissue reduction during Baha
surgery to improve the cosmetic outcome and further simplify the Baha surgical
procedure a new abutment (Cochlear Baha BA400 Abutment) has been developed by
Cochlear Bone Anchored Solutions (Mölnlycke, Sweden).The new abutment has a
design aimed to improve soft tissue adherence to the abutment and limit pocket
formation, which is believed to be key for maintaining good soft tissue health.
The abutment has been designed with a concave shape at the lower aspect of the
abutment, and the titanium surface has been partly coated with a hydroxyapatite
layer. The concave shape is believed to be beneficial in stabilising the soft
tissue by increasing the length of the soft tissue-to-implant contact and by
creating a void space in which a blood clot forms that provides space for new
soft tissue regeneration as proposed by Rompen et al. Hydroxyapatite is a
well-known biomaterial, which finds its application in different types of
medical implants, such as orthopaedic and dental implants. Pre-clinical and
clinical investigations on different percutaneous implant devices have shown
that hydroxyapatite provides enhanced soft tissue contact thus limiting
epidermal down growth and pocket formation (providing a barrier against
bacterial infiltration) and stabilising the soft tissue.

The new abutment, Cochlear Baha BA400, together with a surgical procedure that
do not require soft tissue reduction was CE marked in June 2012.

1 Primary objective
To demonstrate that the minimally invasive surgical procedure in combination
with the use of the BA400 abutment is associated with a reduction of
inflammation/ infection, overgrowth, pain and numbness at the site of
implantation compared to the traditional surgical procedure in combination with
the use of the standard Baha abutment (Cochlear Baha BA300 Abutment).
To demonstrate that the minimally invasive surgical procedure in combination
with the use of the BA400 abutment is associated with a reduction in direct
medical costs, due to shorter surgical procedures, faster wound healing and
less complications compared to the traditional surgical procedure in
combination with the use of the standard Baha abutment (Cochlear Baha BA300
Abutment).

2 Secondary objectives
* To demonstrate that the new surgical procedure and use of the BA400 in
comparison with traditional surgical procedure and the use of BA300, is
associated with:
* Less symptoms of inflammation and infection (Holgers index)
* Less tissue thickening/overgrowth
* Less pain
* Less numbness
* Faster wound healing
* Better aesthetic
* Shorter surgical procedures
* Safety evaluation (loss of implant, adverse events and device deficiency)

3 Tertiary objective
To demonstrate that subjects experience an improved quality of life when
receiving a Baha.

An international multicentre, open, randomised, comparative, parallel group,
prospective clinical investigation.
14 months investigation with a 2 year follow-up.

The surgical placement (conventional versus the simplified surgical technique)
of the comparator (Baha BA300) or investigational device (Baha BA400)

1. Burden
The extra burden for patients in participating in this study is minimal and
consists mainly out of the completion of multiple questionnaires and a
investment of time over a period of 3 years. The study does not contain any
invasive diagnostics nor does it contain any other disadvantageous procedures
for patients.

2. Risks
There are no foreseeable additional risks (when compared to the conventional
Baha procedure) for patients in participating in this study. Bone anchored
hearing aids have been implanted for over 35 years now. The adjustment of the
design of the Baha in this study is minimal and is substantiated by
pre-clinical and clinical studies. The simplified surgical technique is already
being put to practice in several clinics around the world and clinical studies
have deemed it safe. The product has been certified with a CE marking.