This was a prospective study of the first 30 consecutive patients implanted using the DermaLockTM (BA400) abutment at our institution (February-September 2013).

Intra-operatively, soft tissue thickness was measured to guide selection of abutment length. Subsequently, a 2-3cm linear incision was made to gain access and extended to a small cruciate incision around the designated implant site (figure 2). No dermal reduction was undertaken and thereafter implant insertion was performed in a standard fashion. Post-operatively, patients were followed for a minimum of six months and any complications recorded. Time to loading of the sound processor was also noted. Four months after loading patients were asked to complete the Glasgow Benefit Inventory (GBI) by means of postal survey.

Methods

Osseointegrated Hearing Implant Surgery with Soft Tissue Preservation Using the CochlearTM DermaLockTM (BA400) Abutment

Mark D Wilkie, Kalyan M Chakravarthy, Costantinos Mamais, Robert H Temple Department of Otorhinolaryngology – Head & Neck Surgery, Countess of Chester Hospital, UK

Recently, several authors have proposed contemporary soft tissue preservation techniques for osseointegrated hearing implant surgery1-5. All such reports, however, have utilised traditionally shaped titanium-based implant systems.

In 2012, the CochlearTM introduced the DermaLockTM (BA400) abutment (figure 1), the first designed specifically for soft tissue preservation surgery. We present our early experience with this abutment with corresponding patient-reported outcomes.

Introduction

Mean patient age was 61 years (range 23-91 years) and mean follow-up eight months (range 6-13 months). Mean operating time was 16 minutes (range 9-22 minutes). The distribution of abutment lengths used was as follows: 6mm (n=5), 8mm (n=8), 10mm (n=10), 12mm (n=7). Post-operatively, rapid and favourable wound healing was observed in all cases, with no noticeable defect and minimal hair loss (figure 3).

Four patients (13.3%) suffered subsequent periabutment soft tissue reactions, all of which were successfully managed conservatively. Grading of the soft tissue outcomes is detailed in table 1. Respective general health, social support, and physical health GBI mean subscale scores were +51 (95% CI; 42-60), +19 (95% CI; 8-30), and +8 (95% CI; -1-17). The overall score is depicted in table 2 and compared with previous studies reporting GBI scores with traditional surgical techniques.

Results & Discussion

Holger’s Grade Characteristics Number of Patients (%)

0 No reaction 26 (86.7)

1 Redness, slight swelling 2 (6.7)

2 Redness, moistness, moderate swelling 1 (3.3)

3 Redness, moistness, moderate swelling, granulations 1 (3.3)

4 Overt signs of infection requiring implant removal 0 (0)

Table 1: Soft tissue outcomes in our patient group as graded by Holger’s classification.

• Our preliminary findings support soft tissue preservation surgery and indicate that the technology on which the DermaLockTM abutment is based may indeed translate favourably into clinical practice, possibly improving soft tissue outcomes in this context.

• We have also demonstrated that patient-reported quality-of-life may be enhanced when using a soft tissue preservation approach.

Conclusions

References: 1 – Hawley K, Haberkamp TJ. Otolaryngol Head Neck Surg 2013;148:653-7. 2 – Hultcrantz M. Otol Neurotol. 2011;32:1134-1139. 3 – Husseman J, Szudek J, Monksfield P, Power D, O'Leary S, Briggs R. J Laryngol Otol 2013;127:S33-8. 4 – Lanis A, Hultcrantz M. Otol Neurotol 2013;34:715-22.

Current Study Arunachalam et al6 McLarnon et al7 Gillet et al8

Overall GBI Score +38 (31-45) +31 (22-41) +33 (25-42) +32 (10-55)

Number in Study 30 60 94 59

Response Rate 87% 85% 73% 69%

Table 2: Overall GBI compared with those reported for traditional soft tissue reduction techniques.

Figure 3: Typical post-operative appearances at 1 week (A) and 8 weeks (B and C) following implantation

A B

Figure 1

Figure 2: Intra-operative appearances pre- and post-closure

During healing, the epidermis is very active and proliferative. Its

primary function is to cover the open wound and reduce the risk of

infection. A strong adhesion to the extracellular matrix is known to

prevent excessive cell migration and pocket formation, while creating a

barrier for micro-organisms.15,17,19 These are believed to be key factors in

obtaining successful outcomes for surgery with soft tissue preservation.

THE DERMALOCK ABUTMENT DESIGN

The Cochlear™ Baha® DermaLock™ Abutment (BA400) (Figure 2) is

designed with a pronounced concavity in its lower section in order to

stabilise soft tissue. The abutment surface in contact with soft tissue is

also coated with a layer of hydroxyapatite. This coating facilitates tight

integration between the dermis and the abutment.

The hydroxyapatite coating on the DermaLock Abutment is applied

with a plasma-spray technique. Factors such as surface roughness, layer

thickness and the surface texture were carefully selected to optimise

the mechanical properties and durability of the coating. The thickness

of the coating is approx. 80μm and, before plasma-spraying takes

place, the abutment surface is blasted with aluminium oxide powder to

optimise the durability of the coating.

As the surface of the hydroxyapatite-coated part of the DermaLock

Abutment is rougher compared to a titanium abutment, cleaning

tests were conducted to verify that any bacteria on the hydroxyapatite

surface can be effectively removed using existing cleaning guidelines for

Cochlear Baha abutments. The result of the cleaning tests confirms that

there were no differences in cleaning effectiveness compared to the

BA300 Abutment.20

Multiple abutment choices

The DermaLock Abutment is available in four different lengths to

match the varying thickness of an individual patient’s soft tissue (Figure

3). The hydroxyapatite coating is applied up to 3 mm below the top of

the abutment (2 mm below the top of the 6 mm abutment).

Multiple abutment choices and the internal snap coupling provide

maximum clearance between the skin and the sound processor, as

well as a low projection above the skin. For example, if the soft tissue

thickness is 7 mm, a 10 mm DermaLock Abutment could be selected,

providing 3 mm of clearance (Figure 4).

12 mm10 mm8 mm6 mm

Figure 2. DermaLock Abutment shape and coating

Concave shape

Hydroxyapatite-

coated surface

Figure 3. 6 mm, 8 mm, 10 mm and 12 mm DermaLock Abutment lengths.

Figure 4. Abutments in 2 mm intervals, together with an internal snap cou-

pling, provide the lowest achievable profile while preserving soft tissue.

Figure 1: The DermaLockTM abutment features a pronounced concavity on its lower section and is coated with a layer of hydroxyapatite, both unique design characteristics which facilitate tight integration between abutment and surrounding soft tissues to prevent adverse soft tissue reactions.

5 – Wilson DF, Kim HH. Otolaryngol Head Neck Surg 2013;149:473-7. 6 – Arunachalam PS, Kilby D, Meikle D, Davison T, Johnson IJ. Laryngoscope 2001;111:1260-3. 7 – McLarnon CM, Johnson I, Davidson T et al. Otol Neurotol 2012;33:1578-82 8 – Gillett D, Fairley JW, Chandrashaker TS, Bean A, Gonzalez J. J Laryngol Otol 2006;120:537-42.

Introduction: Recently, a novel hydroxyapatite-coated concave bone-anchored hearing device abutment was introduced, the first designed specifically to improve outcomes in soft tissue preservation osseointegrated hearing implant surgery. We sought to evaluate our early experience with this abutment. Methods: The first 30 consecutive patients undergoing osseointegrated hearing implant surgery using the CochlearTM DermaLockTM (BA400) abutment at our institution (February-September 2013) were studied. Follow-up was for a minimum of six months. The following data were collected: operative duration; would healing; post-operative complications, chiefly soft tissue reactions graded by Holger’s classification; post-intervention patient-perceived health-related quality-of-life, as assessed by the Glasgow Benefit Inventory (GBI). Results: The mean operating time was 16 minutes (range 9-22 minutes). Favourable and rapid wound healing was observed in all cases. Three patients (10%) reported transient periabutment paraesthesia. Four patients (13.3%) suffered adverse soft tissue reactions, all of which were successfully managed conservatively, and graded as follows: Holger’s grade 1 (n=2), 2 (n=1), and 3 (n=1). Respective overall, general health, social support, and physical health GBI mean scores were +38 (95% confidence interval [CI]; 31-45), +51 (95% CI; 42-60), +19 (95% CI; 8-30), and +8 (95% CI; -1-17). Conclusions: Our preliminary clinical and patient-reported outcomes support soft tissue preservation surgery, and indicate that the technology on which the CochlearTM DermaLockTM (BA400) abutment is based may enhance soft tissue outcomes in this context. We recommend further appraisal of this approach on a larger scale with more extensive follow-up.

Abstract

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