Long-term stability and survival rates of a novel Oticon Medical bone conduction device implant

Bone conduction hearing systems was introduced in 1977 and has now been used
clinically for over 30 years. More than 75,000 patients have been fitted with
the system worldwide and long-term clinical follow-up studies have shown an
overall implant survival rate of more than 90%. However higher failure rates
have been reported to occur in patients with compromised bone and in children.
With the aim to improve outcomes for all patient groups and also to reduce the
loading times and enable the patient to benefit from the device earlier a new
implant design was developed by Oticon Medical based on known technology of
bone anchored hearing aids as well as knowhow from the dental industry. This
clinical prospective study will investigate the clinical outcomes of this new
implant.
With the aim to improve outcomes for all patient groups and reduce the loading
times a new implant design was developed by Oticon Medical based on known
technology of bone anchored hearing aids as well as knowhow from the dental
industry. As a general concept it has been found that screw shaped implant
design develops higher mechanical retention as well as greater ability to
transfer compressive forces. The screw design not only minimizes micromotion of
the implant but also improves the initial stability. In addition there is
evidence in the literature that stability may be improved by increasing the
implant diameter and/or decreasing the drill diameter. The implant length has
also been shown to influence the outcome of immediate loading of dental
implants. This is primarily due to the fact that increase in length, equals
increase in surface area. Micro threads at the upper part of the implant have
been shown to limit or delays bone resorption and the literature also suggests
that marginal bone loss tend to stop at the first tread. Skin reactions have
been found to be caused by movement of the skin, thick skin, or poor skin
condition around the implant. The literature also suggests that the
accumulation of bacteria in the skin penetration and skin movement in relation
to the abutment is a cause for skin reactions. Based on this knowledge the
screw shape of the Ponto wide implant is designed with a maximized implant
surface and a conical flange for increased support. The treads extend all the
way up to the implant flange and the implant is further equipped with a micro
groove under the flange. In addition the diameter is increased and by
optimizing the cutting abilities the drill diameter has been decreased. The
design of the new Ponto implant has also a unique new cutting geometry which
means it cuts more efficiently and gentle in to the bone tissue. Except for
offering a high initial bone contact and stability, it means that the diameter
of the drilled hole in the bone can be reduced without making it harder for the
implant to engage and be inserted in the hole. With the new design, the drill
diameter was reduced to 3,7 mm compared to a 4,0 mm drill diameter that is
required for a traditional implant design of a 4,5 mm diameter implant. It is
the final countersink drilling that prepares the hole in the living bone that
will interact with the implant in the osseointegration process. The Ponto
abutment has been designed with a tight seal to the implant to avoid micro gaps
for bacteria to grow and be transported in. The Ponto abutment design allows
the skin to be supported by the underlying bone and periost all the way up to
the abutment without having it to go into a groove or lying more unsupported on
top of the implant flange. In addition to that the abutment interface against
the skin is smooth without any grooves for dirt and bacteria to be collected
in.

The overall aim of the study is to investigate the Ponto wide implant
considering; initial implant stability, stability over time, skin reaction and
long term success when loaded at 3 weeks post surgery. Patients* quality of
life improvements following implantation will also be surveyed.
More specifically the primary objective of this clinical study is to test the
hypothesis;
1. The new Ponto wide diameter implant offers increased implant stability
measured as ISQ compared to the previous generation Ponto implant.
2. Loading of the sound processor at 3 weeks after surgery does not affect the
stability of the implant.
And the secondary objective is to investigate when in time implant stability is
the lowest as the initial mechanical stability is gradually replaced by
biological stability.

The clinical investigation is an open, randomized, prospective, controlled,
study enrolling 60 adult patients. Patient inclusion will be performed among
patients that already have been audiologically and otologically evaluated and
found suitable candidates for treatment with a bone anchored hearing aid. The
patients will be randomized to either of the two implants in proportions of 2:1
(test *control). The randomization will be blinded to patients and
investigators until the time of surgery. Both study groups will come for
check-ups at 7 days, 14 days, 21 days, 28 days, 6 and 12 weeks, 6, 12, 24 and
36 months following implant insertion. At each visit a clinical evaluation will
be made where implant stability is measured using ISQ. At each visit skin
status is also assessed. 3 weeks after surgery the patients will be fitted with
the sound processor. To determine benefit of implantation of the Ponto device,
each patient will be surveyed, using the Glasgow Benefit Inventory. The Glasgow
Benefit Inventory (GBI) is a measure of patient benefit developed especially
for otorhinolaryngological (ORL) interventions. Patient benefit is the change
in health status resulting from the intervention. The GBI is an 18-item,
post-surgical questionnaire given to patients.

The intervention is surgical placing of a new type of titanium implant to
connect a BCD. 60 patients will participate in the study, of which 40 will
receive the test, wide implant, while the other 20 patients will receive the
conventional implant. Distribution will be drawn by lot. Besides the different
implant type, both groups will be treated exactly the same.

The risk of participating in the study is low and comparable with corresponding
rehabilitation outside the study. The implant surgery is identical to the
regular surgery and will not contribute to any additional risk. By following
the patients over time this will give an indication on the design modifications
contribution to increasing overall implant survival rate. The patients will be
fitted with their sound processor 3 weeks before regular practice which will
speed up the rehabilitation. No complication other than those that might occure
when rehabilitating patients with a bone anchored hearing aid oustide the study
is anticipated. Treatment of possible complications for patients in the study
will be the same as for regular implant patients. All adverse events will be
registered and taken into consideration when compiling the final report. The
result of the study in finding timing of the lowest implant stability will give
important direction for further research within this field. Participation in
the study will require more frequent follow-ups for the patient than what is
normally required. This will require an extra effort for the patient however
the patient will have the opportunity to more frequently interact with the
treating physician.