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Accepted: 16 November 2017
Percutaneous bone-anchored hearing system implant survival
after 550 primary implant surgeries
The Bone-Anchored Hearing System (BAHS) has become an estab-
lished option for rehabilitation of several type of hearing impair-
ment such as conductive hearing loss, mixed hearing loss and
Overall good outcomes have been reported.
Nevertheless, complications such as inflammation of the skin
around the percutaneous abutment, pain and implant loss are
related to BAHS.
For implant loss stability, primary and secondary stability are
important concepts. Primary stability is defined as implant stability
immediately after surgery. Dental studies show that primary stability
is influenced by implant design, surgical technique, bone quantity
and bone quality.
Secondary stability is defined as stability over
time and is determined by primary stability and osseointegration. In
dental implants, osseointegration is influenced by surgical trauma,
implant design, smoking status and other subject-related factors such
as diabetes and hygiene.
In BAHS, implant loss rates of 8.3%-18% have been reported.
3-mm implants, young age, age of 60 or higher and male status have
been described as risk factors for implant loss.
In this study, we
aimed to analyse implant survival rates for BAHS surgery including
risk factors for the population in Maastricht University Medical Cen-
tre+ (MUMC), the Netherlands.
MATERIALS AND METHOD
Due to the retrospective nature of this study and anonymisation of
data, ethical approval was not required according to the Medical
Research Involving Human Subjects Act in the Netherlands.
This is a retrospective case study of subjects receiving a BAHS
implant between 1991 and January 2017 in MUMC. A database
containing all subjects that have received a BAHS implant was
used. Implant length, abutment length, manufacturer and if appli-
cable extrusion or explant surgery are captured in this database.
The database was checked by a second researcher for inconsis-
Statistical analyses were performed using R version 3.3.2 (R Foun-
dation for Statistical Computing, Vienna, Austria). Statistical signifi-
cance was established at P ≤ .05. Mean (M) age at implantation,
standard deviation age (SD), mean follow-up time and SD for fol-
low-up were calculated for all implants. Kaplan-Meier curves were
created for overall survival. 1-year, 5-year, 10-year and 15-year
implant survival rates were calculated for primary placed 4-mm
implants, 3-mm implants and for 4-mm implants placed after
implant loss. Based on previous reported possible risk factors,
the effect of 3-mm implants, second 4-mm implant, male sex,
young age (<18) and age >60 at implantation was examined in a
multivariable analysis using a Cox’s proportional hazards regression
model. An explorative analysis including new generation implants
with a wide diameter (4,5 mm) as an additional factor was exam-
ined. Hazard ratios (HR) and 95% confidence intervals (CI) were
determined for all factors.
From 1991 to January 2017, 536 subjects were implanted with
550 primary BAHS implants at MUMC. Five hundred and eleven 4-
mm (92.9%) implants and 39 3-mm (7.1%) implants were inserted
in 536 subjects of which 266 (49.6%) were males and 270 females
(50.4%). Mean age was 49 years (SD = 18) with a mean follow-up
time of 7.48 years (SD = 5.0). Five hundred and eleven 4-mm
implants were inserted with a mean follow-up time of 7.5 years
(SD = 5.1). Mean age at implantation for 4-mm implants was 51
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