Keywords
hearing aids - deafness - otologic surgical procedures
Introduction
Initially introduced in Sweden in the early 1970s, bone-anchored hearing aids (BAHAs)
were approved for use in the United States in the late 1990s.[1]
[2]
[3] Bone-anchored hearing aids are indicated for individuals with conductive or mixed
hearing loss when conventional hearing aids are contraindicated or unfeasible, as
well as those with single-sided deafness.[4]
[5] The device transmits sound from a processor though an osseointegrated titanium implant
embedded in the temporal bone, and it stimulates the cochlea through bone conduction.[5]
[6]
[7] Bone-anchored hearing aids have provided significant benefits for individuals who
are not candidates for surgery or conventional hearing aids, and have shown improvements
in auditory gain of 10 to 25 dB when compared with traditional bone conduction hearing
aids.[5]
[8]
[9]
[10]
[11]
The BAHA consists of a sound processor that attaches to a percutaneous titanium abutment
affixed to an osseointegrated titanium fixture. The standard surgical technique for
placement of the titanium implant involves the use of pedicled skin grafts and extensive
subcutaneous tissue thinning down to the periosteum.[12] Despite being largely successful, this technique is not without its shortcomings.
Multiple variations for placement of the percutaneous BAHA have since been developed,
and unfortunately continue to be beleaguered by soft tissue complications, including
skin flap necrosis, flap infection, skin growth over the abutment, failure of osseointegration,
and extrusion of the titanium implant.[13]
[14]
[15]
[16]
[17]
[18]
[19] To avoid the adverse skin complications and aesthetic concerns associated with the
percutaneous BAHA, a new magnetic bone conduction hearing implant system has been
developed.[20]
[21] Instead of a percutaneous abutment, the magnetic system involves both implanted
and external magnets that support the sound processor and transfer sound to the osseointegrated
titanium implant.[21] Recent studies of this new device have shown a favorable adverse event profile and
improved cosmesis, with no severe soft tissue complications and only few cases of
skin erythema and irritation.[21]
Since 2008, we have employed multiple techniques for BAHA implantation, and have experienced
an array of soft tissue complications associated with each technique. In this study,
a single surgeon's experience with six different techniques for BAHA implantation
is presented. This project's purpose is to compare multiple techniques for BAHA implantation
regarding postoperative complications, operative time, and duration between the surgery
and the first use of the BAHA. Although various comparisons of BAHA implantation techniques
have been performed, no study comparing multiple techniques by a single surgeon exists
in the literature. Moreover, this study is unique in that it compares the operative
outcomes of both percutaneous and magnetic BAHA implantation techniques.
Materials and Methods
Cohort
After the Institutional Review Board (IRB) approval was obtained, a retrospective
study was conducted of all patients receiving implantation of a BAHA from August 2008
to October 2014 by a single surgeon. The system implanted in each case was either
the percutaneous Baha Connect or the magnetic Baha Attract (Cochlear Ltd., Sydney,
Australia). The medical records were obtained, and the data was collected, including:
patient age, gender, side operated, abutment length, operative time, duration until
first use of the BAHA, operative technique, and postoperative complications. A complication
was defined as an instance that would require additional postoperative care, including
steroid or antibiotic treatment, debridement, surgical revision, or implant removal.
Soft tissue complications were further classified according to the Holgers classification
system ([Table 1]). Two cases in the time series reviewed were excluded because of insufficient data.
Data was entered into an Excel database spreadsheet (Microsoft Corp., Redmond, WA).
The statistical analysis was performed on the collected data using analysis of variance
(ANOVA), Tukey pairwise comparison, chi-square, and paired t-test. The statistical significance was determined using a level of p < 0.05.
Table 1
Holgers classification system for skin reactions at the BAHA implantation site
|
Grade
|
Description
|
|
0
|
Reaction-free skin around the abutment
|
|
1
|
Redness with slight swelling around the abutment
|
|
2
|
Redness, moistness, and moderate swelling
|
|
3
|
Redness, moistness, and moderate swelling with tissue granulation around the abutment
|
|
4
|
Overt signs of infection resulting in removal of the implant
|
Surgical Techniques
All surgeries were performed in a single stage under general anesthesia by a single
surgeon. Six different techniques were employed as summarized below. The dermatome
technique was the first employed and the Attract technique is the most recent.
Dermatome Technique
The technique used is as described by Stalfors and Tjellstrom and utilizes a dermatome
to create a 0.6 mm thick and 25 mm wide anteriorly-based skin flap.[18] Soft tissue down to the level of the periosteum is debulked and removed and the
periosteum is then elevated in the region to accommodate the titanium implant. After
securing the implant in the temporal bone, a 4-mm skin-biopsy punch (Miltex Inc.,
York, PA, USA) is then used to perforate the skin flap over the implant. The skin
flap is then threaded over the implant and sutured to the surrounding periosteum.
A dressing is applied, and the healing cap is placed over the abutment. The abutment
length was not recorded in any cases utilizing the dermatome technique.
U-shaped Flap Technique
The technique used is as described by Stalfors and Tjellstrom and proceeds similarly
to the dermatome technique.[18] The primary difference is that rather than using a dermatome, a scalpel is used
to create a 3–4 cm anteriorly based skin flap and debulk the underlying soft tissue
to the level of the temporal bone periosteum. The abutment length varied from 4 to
12 mm among cases utilizing the U-shaped flap technique.
Linear Technique
The technique used is as described by Mylanus and Cremers and de Wolf et al, and it
involves a 3 cm vertically-oriented incision with soft tissue reduction 2 cm around
the periphery of the incision.[22]
[23] The periosteum is elevated, and the implant placed in the standard fashion according
to the manufacturer's recommendations. The implant is brought through the incision,
and the skin edges are approximated to the periosteum surrounding the implant. A dressing
is applied, and the healing cap is placed over the abutment. The abutment length varied
from 5.5 to 8.5 mm among cases utilizing the linear technique.
Linear Technique with Biopsy Punch
The technique is similar to the linear technique described by de Wolf et al, and is
further summarized by Gordon and Coelho.[11]
[23] The primary difference is that rather than bringing the implant through the incision,
a 4-mm skin-biopsy punch is used to deliver the implant placed just anterior to the
vertical incision. The abutment length varied from 5.5 to 9 mm among cases utilizing
the linear technique with biopsy punch.
Biopsy Punch
The technique used is as described by Wilson and Kim, and it uses a 4-mm skin-biopsy
punch to incise the skin and resect the underlying soft tissue and periosteum.[5] The titanium implant is then placed in the usual fashion, a dressing is applied,
and the healing cap is placed over the abutment. An 8.5 mm abutment was employed in
all cases utilizing the biopsy punch technique.
Attract
The technique used follows the manufacturers guidelines, and is outline by Iseri et
al[20] A 6 cm diameter C-shaped incision is utilized to create a full-thickness skin flap.
The soft tissue is reduced if measured thicker than 6 mm, and the bone surrounding
the implant and internal magnet is smoothed if necessary. Following implantation of
the titanium fixture and internal magnet, the skin flap is replaced, the wound is
closed primarily with sutures, a drain is placed and a dressing is applied ([Fig. 1]).
Fig. 1 (A) An 18 gauge needle dipped in methylene blue is used to mark the temporal bone where
the implant will be placed. A 3cm semi-circle is then marked as the incision site.
(B) The flap is taken down to periosteum with soft tissue reduced. (C) The implant is drilled in place with magnet secured in proper position. (D) A drain is placed and the flap is sutured primarily with layered closure.
Results
A total of 90 patients underwent unilateral BAHA implant surgery during the study
period, and 88 (43 female, 45 male) were included in data analysis. The average patient
age was 58 years, and the ages ranged from 13 to 83 years. The BAHA implantation was
performed on the left side in 47 cases, and on the right side in 41 cases. Six patients
underwent the dermatome technique, 25 the linear technique, 6 the biopsy punch technique,
15 the linear technique with biopsy punch, 23 the U-shaped flap, and 13 patients underwent
BAHA implantation via the Attract system ([Table 2]). The average surgical time and days until fitting of the processor and first use
of the BAHA were calculated based on each technique employed and are shown in [Table 2]. There were no cases of lost processors and no patient required any change in the
strength of the Attract magnet.
Table 2
Comparison of patients undergoing BAHA implantation using various techniques
|
Characteristic
|
Dermatome
|
Linear
|
Biopsy Punch (BP)
|
Linear with BP
|
U-shaped Flap
|
Attract
|
p
|
|
n = 6
|
n = 25
|
n = 6
|
n = 15
|
n = 23
|
n = 13
|
|
|
Mean age
(years)
|
54.8
|
55.8
|
60.5
|
58.9
|
59.3
|
56
|
0.94
|
|
Location
(% right-sided)
|
50
|
44
|
66.7
|
46.7
|
47.8
|
38.5
|
0.92
|
|
Gender
(% male)
|
33.3
|
56
|
83.3
|
60
|
34.8
|
53.8
|
0.26
|
|
Complications
(Total)
|
6
|
19
|
12
|
20
|
22
|
1
|
< 0.01
|
|
Major complications
(Holgers 3 & 4)
|
3
|
14
|
6
|
13
|
9
|
0
|
?
|
|
Average. surgical time (min.)
|
67
|
54
|
30
|
51
|
41
|
62
|
< 0.01
|
|
Average. time to 1st use (days)
|
90
|
91
|
97
|
88
|
92
|
59
|
0.16
|
There was no statistically significant difference regarding age, side of surgery,
gender, or abutment length between the various techniques ([Table 2]). All postoperative complications were recorded for the cohort. A total of 80 complications
were documented, including skin irritation requiring the use of topical steroids,
cellulitis around the implant site, overgrowth of skin over the abutment, hematoma
formation, granulation tissue requiring debridement, wound dehiscence, and overt infection
requiring removal of the implant. These complications were classified based on the
Holgers criteria and are shown in [Table 3]. A significant difference in the total postoperative complications existed among
the six techniques used (ANOVA; p < 0.01). A Tukey pairwise comparison indicated a significant difference between the
Attract and biopsy punch techniques. Furthermore, when a direct comparison of the
percutaneous and the Attract techniques was analyzed, the total number of postoperative
complications was significantly lower for the Attract technique in comparison to the
other percutaneous techniques (paired t-test; p < 0.01) ([Table 2]).
Table 3
Soft tissue complications by technique employed
|
Holgers Classification
|
1
|
2
|
3
|
4
|
Total Complications
|
Total cases
|
Cases without complications (%)
|
|
Dermatome
|
2
|
1
|
2
|
1
|
6
|
6
|
50
|
|
Linear
|
5
|
0
|
9
|
5
|
19
|
25
|
44
|
|
Biopsy Punch (BP)
|
3
|
3
|
5
|
1
|
12
|
6
|
33.3
|
|
Linear with BP
|
7
|
0
|
12
|
1
|
20
|
15
|
26.7
|
|
U-shaped Flap
|
7
|
6
|
8
|
1
|
22
|
23
|
43.5
|
|
Attract
|
1
|
0
|
0
|
0
|
1
|
13
|
92.3
|
|
Total
|
|
|
|
|
80
|
88
|
47.7
|
Regarding the operative time, the analysis of the data demonstrated that a significant
difference existed between the six techniques employed (ANOVA; p < 0.01). A Tukey pairwise comparison test indicated that the operative time for the
biopsy punch technique was significantly shorter than both the Attract and dermatome
techniques. When the percutaneous and the Attract techniques were directly compared,
the average surgical time was significantly shorter for the percutaneous BAHA implantation
(paired t-test; p < 0.01).
There was no statistically significant difference between the average duration of
time until fitting of the BAHA processor among the various techniques (ANOVA; p = 0.16). When the percutaneous and the Attract techniques were directly compared,
though, the average time to fitting of the processor and the first use of the BAHA
system was significantly shorter for the Attract system (paired t-test; p < 0.01).
Discussion
Since their introduction, the implementation of BAHAs has offered improved auditory
performance, and provided an additional option for hearing rehabilitation among individuals
that would otherwise be unsuitable candidates for conventional hearing aids. Various
techniques for BAHA implantation have been described, with more contemporary approaches
attempting to minimize or avoid the high rate of soft-tissue complications seen with
other techniques. Nonetheless, soft-tissue complications continue to vary in severity
among patients, and the overall rate of complications differs significantly throughout
the literature. According to one review, the overall rate of complications ranged
from 15.2 to 88% among 10 published studies.[24] What is more, the complication rates reported in relation to a given technique for
BAHA implantation have varied among authors. Wilkinson et al experienced a 16.9% total
complication rate in their series of 71 patients implanted with the linear incision
technique, whereas de Wolf et al experienced skin reactions in 51% of their patient
population.[7]
[23] These findings highlight the difficulty in comparing the complication rates of multiple
techniques among various authors, as one must expect significant variability.
In this study, we compared the complication rates and operative times among six different
techniques for BAHA implantation performed by a single surgeon. As shown in [Table 3], a total of 80 complications occurred among the 88 procedures performed. Although
many patients experienced multiple complications, only 47.7% of the entire population
experienced no soft tissue reactions postoperatively. Moreover, among the percutaneous
surgeries, the rate of cases performed without complications was best for the dermatome
technique, with only half of the cases experiencing adverse soft-tissue reactions.
In contrast to the high rate of soft-tissue complications among percutaneous BAHA
implantations in this and other series, use of the magnetic Attract system resulted
in significantly less overall complications in our series. While audiometric outcomes
were not established in this study, previous research has shown that with the Attract
there is no direct stimulation of the implant, and therefore, there is a loss of energy
through the skin at higher frequencies ranging from 10 to 15 dB.[21] Indeed, only one complication occurred in the Attract group, and it was classified
as a Holgers class 1 complication. In addition, 92.3% of the Attract cases did not
experience any complications. These results are supported by the study conducted by
Briggs et al, in which only 4 cases of mild skin erythema were noted in their series
of 27 implanted patients, and no major complications occurred.[21] The erythema noted in each case was likely caused by the pressure exerted by the
magnet on the soft-tissues. Although the magnet may be cause irritation due to the
pressure exerted, it seems to carry less risk for bacterial seeding and chronic inflammation
of the soft tissues than a percutaneous implant.
The analysis of our data demonstrated another advantage of the Attract system in comparison
to percutaneous techniques for BAHA implantation, which was that the time to fitting
the processor was shortest for the Attract population (average time to fitting processor:
percutaneous 88–97 days; Attract 59 days). Thus, with the Attract system, the patients
have to wait a significantly shorter amount of time until the first use of their BAHA.
Despite the improvement reached on soft-tissue reactions, the Attract technique took
significantly longer to perform than one of the percutaneous techniques (avg. time
of 62 minutes for the Attract and 30 minutes for biopsy punch). Given the potential
reduction in healthcare costs associated with decreased operative time, this finding
can have substantial impact. Likewise, a similar finding was made by Gordon and Coelho
in demonstrating that the biopsy punch technique could be performed in significantly
less time that the linear incision technique.[11] Thus, when comparing the Attract and biopsy punch techniques, the decreased operative
time for the biopsy punch technique must be weighed against its significantly greater
risk of soft-tissue reactions.
Several limitations of this study are worthy of mention. Since the Attract technique
is the most contemporary of all the BAHA implantation techniques in our series, we
have less longitudinal data regarding the care of this patient cohort. Thus, long
term complications associated with the implant have yet to be determined. Furthermore,
the Attract system would be expected to have a more favorable length of surgery, as
it is the most contemporary of the approaches. Even so, it took longer to perform,
on average, than most of the percutaneous techniques despite the improvement in the
surgical proficiency over time. This further highlights the substantially increased
amount of time needed to implant the Attract system. While the audiological results
of our cohort were consistent with previously published reports,[5]
[8]
[9]
[10]
[11] future studies are needed to elucidate whether differences in audiometric outcomes
exists between varying BAHA devices and techniques. Lastly, additional variables of
cosmesis and postoperative pain were not included in this data analysis, but are important
aspects of the BAHA implant surgery and worthy of further study.
Conclusion
Significant differences in operative outcomes exist among the various techniques for
BAHA implantation. Based on the statistical analysis of our data, the Attract system
requires longer operative time, but it is associated with less postoperative complications
than percutaneous techniques and its processor may be fitted significantly sooner.
