Introduction

Cochlear implantation is a generally admitted surgical procedure for individuals with severe to profound sensorineural hearing loss who cannot benefit from conventional hearing aids. This solution has been routinely used since the 1970s and thousands of people (children and adults) have been successfully implanted. The benefits of this solution are without any doubts. However, cochlear implantation, like every surgical procedure, can cause some complications. They are usually related to the patients and only sometimes to surgery or to the implant [1].

Skin flap complications after cochlear implantation are associated with infection and inflammation of soft tissue covering the cochlear implant body. They can be divided into minor, which usually resolve spontaneously or can be managed by local/topical ambulatory treatment, and major, which require treatment in hospital involving surgical procedures and, often, explantation. The frequency of major complications is reported in 1.08–8.2 % of implanted patients [2–5] and cannot be reduced over the years of experience.

The aim of this study is to analyse the incidence and causative factors of major skin flap complications (MSFC) after cochlear implantations in our group of patients and to present our experience in different treatment options and its effectiveness.

Materials and methods

The study was based on the retrospective analysis of medical charts of 1076 patients operated on with cochlear implants in our department between 1994 and 2013: 632 children (302 female and 330 male, aged 1–18 years with the mean of 5.39 and median of 3.5) and 444 adults (227 female and 217 male, aged 18.5–81.5 years with the mean of 46.54 and median of 47.5). All patients were fitted with the same type of cochlear implant (silicone-coated implant body—Cochlear Ltd., Australia), with the same surgical protocol and postsurgical follow-up (Table 1). The only modification over the years was the type of skin incision. A long “C”-shaped incision was performed in 452 implantations; since 2007 it was changed into a short linear retroauricular incision (624 implantations).

Table 1 Cochlear implantation surgical protocol and follow-up in our department
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Analysis aimed to identify individuals with MSFC defined as skin flap complications requiring in-hospital treatment with surgical intervention. Out of 1076 medical charts, 19 were selected due to reported MSFC. Patients underwent the defined protocol of complication treatment (Table 2).

Table 2 Protocol of major skin flap complication treatment in our department
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A project database was created with a list of data to be collected: (a) incidence (frequency, onset and duration of complaints), (b) risk factors (age, sex, general medical condition, episodes of head trauma, hygiene, variation in surgical protocol, bacteriology) and (c) treatment (options and outcomes).

Obtained data were stored and statistically analysed in a MS Excel database. To compare the frequency of MSFC in the children versus adults group, in female versus male and in the long versus short incision group, a test of proportion was used. The investigation was approved by the local Ethics Committee.

Results

Incidence

MSFC were detected and treated in 1.76 % (n = 19) out of a total 1076 implantations. In two cases, skin complications were detected after a second implantation (Table 3, patients 8 and 19). The onset of skin complication ranged from 1 month after primary implantation up to 10 years and 7 months afterwards, with a mean time of 33.2 months. The symptoms of MSFC comprised gradually developing redness, ulceration and soft tissue defect as well as the acute painful abscess of the operated side. Patients with MSFC are presented in Table 3 and examples of MSFC are presented in Figs. 1 and 2.

Table 3 Patients with major skin flap complications (according to the date of first symptoms)
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Fig. 1
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Major skin flap complication

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Fig. 2
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Major skin flap complication with spontaneous explantation of cochlear implant body

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Risk factors

The frequency of MSFC in the paediatric population was 2.06 % (n = 13) and in adults 1.35 % (n = 6). The difference between those two groups (0.71 %) is not statistically significant [0.71 % Chi2(1) = 0.757, p = 0.3844, 95 % CI −1.1260; 2.3800].

The analysis of sex showed MSFC in 2,32 % of female and 1,82 % of male in paediatric group [difference 0.4997 % Chi2(1) = 0.20, p = 0.6584, 95 % CI −2.0112; 3.1596, result statistically insignificant] and 2.2 % of female and 0.46 % of male in adults group [difference 1.7418 % Chi2(1) = 2.52, p = 0.1121, 95 % CI −0.8130; 1.7418, result statistically insignificant).

Additional patient-related risk factors were detected in 73.6 % (n = 14) out of 19 patients with MSFC. Within the paediatric group, the most common were acute otitis media (3 months to 10 years after implantation): 23.1 % (3 of 13), trauma of the head: 23.1 % (3 of 13) and poor hygiene: 23.1 % (3 of 13). In adults, general medical conditions, e.g. a history of cardiac infarction, diabetes or renal failure were observed in 50 % (3 of 6) cases.

The frequency of MSFC after cochlear implantation with long “C”-shaped incision was 2.43 % (11 of 452) and with short retroauricular incision was 1.28 % (8 of 624) [difference 1.15 % Chi2(1) = 2.00, p = 0.1573, 95 % CI −0.5749; 3.1636, result statistically insignificant].

Bacteriological culturing of MSFC showed Staphylococcus aureus to be the most frequent pathogen (78.6 %) followed by Staphylococci and Gram-negative spp.

Treatment

Intensive targeted therapy with antibiotics was the first step of treatment in all patients (Table 1).

Revision surgery without explantation was done in 52.6 % (n = 10) of cases, and more than one operation was performed in 21.0 % (n = 4). Debridement and primary suturing of the wound was not effective. Rotational skin flap, performed in four cases, was not effective either except in one case supplemented by free skin flap reconstruction which gave a good and permanent positive result. Rotational two-layer flaps were done four times and were successful in three cases. The technique used since 2011 is based on preparation of two flaps: skin with subcutaneous tissue (external layer) and muscle with fascia (internal layer). The muscle was mobilised in the temporal region (superiorly to the pinna) and repositioned posteriorly and inferiorly, and skin was mobilised in the occipital region and rotated anteriorly to cover the targeted local complication. The idea of rotational two-layer flap is presented in Fig. 3. Patients after successful revision of MSFC by two-layer flap are presented in Fig. 4.

Fig. 3
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Rotational two-layer flap: the idea

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Fig. 4
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Patients after successful revision of skin flap complication with rotational two-layer flap

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Explantation was performed in 78.9 % (n = 15) of cases: without previous revision in 47.4 % (n = 9) and after unsuccessful revision in 31.6 % (n = 6). Explantation led to complete wound healing in all patients.

Second cochlear implantation proceeded in 73.6 % (n = 14) of cases. Implantation of the contralateral ear before explantation of the affected one was performed in four cases and prior to revision surgery in one (patient 13). Implantation of the contralateral ear after explantation was performed in five cases (range 2 months to 5 years after). Reimplantation of the same ear was conducted in three cases (7 months to 5 years after explantation). In one patient (patient 9), the contralateral ear was implanted before and the affected ear was reimplanted 10 months after explantation, so this child uses two implants.

Discussion

The frequency of MSFC after cochlear implantation reported in the literature ranges from 1.08 % [2] to 8.2 % [3]. The current study revealed skin complications in 1.76 % of the population, placing our patients within the same range. Such differences can be explained by the number of variables including factors related to patient, surgery or device.

The most frequent patient-related factors discussed in the literature are age and additional comorbidities. The influence of age on soft tissue infection is still an unsettled question. Younger age can be considered as a negative factor due to the higher risk of head trauma and immaturity of the immune system. Garcia-Valdecasas et al. [6] found no important differences between the frequency of MSFC in adults (5.7 %) and in children (6.2 %); however, the frequency in both groups was altogether high. Also, Low et al. [5] observed a similar frequency of MSFC in children (1.83 %) and adults (1.62 %). In our study, the frequency of MSFC in children was higher than in adults (2.06 versus 1.35 %) but these results are statistically insignificant. The influence of comorbidities is also not very clear. Hopfenspirger at al. [3] observed MSFC in a paediatric group more frequently in patients with specific chronic conditions, e.g. tracheotomy (23 %) in comparison to healthy implanted children (6.6 %). On the other hand, Garcia-Valdecasas et al. [6] observed no difference in the frequency of skin flap complications between patients with and without comorbidities. Allergic reactions to the device and radiotherapy of the temporal bone before cochlear implant surgery should also be taken into account [1, 5]. In our group, we have also noted additional local factors. In children, these were trauma of the head, which was noted in three cases (23.1 %), episodes of acute otitis media of the implanted ear (3 months to 10 years after implantation) in three cases (23.1 %) and poor hygiene in three cases (23.1 %). In the adult population, general comorbidities like history of cardiac infarction, diabetes and renal failure predominated. Additionally in adults group we have observed higher frequency of MSFC in female then in male (results statistically insignificant) which can be explain by the difference in soft tissue thickness covering the implant.

Ray et al. [7] showed that the rate of MSFC after cochlear implantation in patients operated on with a small incision (vertical post-aural incision) is significantly lower than in patients with large incision (retroauricular “C”-shaped incision or post-auricular incision with a horizontal posterior limb)—1.1 versus 2.3 %. Also, Davids et al. [2] emphasized that a small incision could be the reason for the small number of MSFC encountered in his paediatric cochlear implant group (1.08 %). Our study also showed that the change to a short incision could reduce the frequency of MSFC from 2.43 to 1.28 %.

Bacteriological examination is essential to ensure the use of proper and successful therapy with antibiotics supporting revision surgery. The literature reports the two most common pathogens as Staphylococcus aureus [3, 5, 8] and Pseudomonas aeruginosa [3, 6, 9]. In our material, swabs from the infected skin over the implant identified Staphylococcus aureus as the most frequent pathogen (78.6 %). Pseudomonas aeruginosa was found only in one patient.

The first surgical treatment option for MSFC is usually wound debridement, excision of infected tissue, decontamination of the device and skin closure. Rotational skin flap or dislocation of the transducer under healthy soft tissue can be performed. Such treatment should be supported by intensive targeted antibiotic therapy [10]. This management is aimed at eliminating inflammation and complete wound healing with the preserved device, but the success rate is variable and not warranted. The main reason for the treatment failure is the bacterial biofilm which covers the surface of an implant [11]. Low et al. [5] performed salvage surgery in six out of eight patients with MSFC with very good results. He used rotational skin flap in five cases, which was successful in two, and transposition of the device body in one case which was successful. Three out of five patients from the failed skin flap reconstruction group underwent subsequent transposition surgery with success. On the other hand, Garcia-Valdecasas et al. [6] tried conservative treatment and surgical cleaning in a group of nine cases with surgical-side infection, but it was not effective in all of them, so finally all these patients were explanted. Also, Hopfenspirger et al. [3] described 22 cases with MSFC after cochlear implantation of which 21 required explantations. In our department, revision surgery without explantation was always considered as a first treatment option but it was finally done in 52.6 %. Our surgical technique changed from debridement and suture of the wound, which failed in all cases, to wound debridement and covering the implant body by a rotational two-layer flap with a success rate of 75 %. This flap was composed of two layers: skin with subcutaneous tissue (external layer) and muscle with fascia (internal layer). Created flaps from healthy regions were subsequently superimposed onto each other over the exposed implant. The resultant closure with good peripheral blood supply was effective in 3 out of 4 cases with no further complication observed on follow-up visits.

The ultimate treatment of MSFC is implant explantation. It is usually indicated if primary revision surgery with device preservation has failed or it is advocated as an alternative to primary revision surgery if there is: (a) a high risk of intra-cranial complication; (b) a severe wound breakdown with complete extrusion of the cochlear implant body or (c) an allergic reaction to the device or foreign body reaction with device failure [1, 5]. In our patients with MSFC, explantation was performed in 78.9 % of cases (in 47.4 % without previous revision surgery and in 31.6 % after unsuccessful revision). Explantation always led to complete wound healing. Similar to others [2, 5, 6, 9], the electrode was cut and left inside the cochlea to prevent cochlea obliteration and to facilitate future reimplantation.

Second cochlear implantation is a very important issue for patients after explantation or qualified to explantation. Depending on the audiological conditions in the contralateral ear and soft tissue status after explantation, the contralateral or previously explanted ear can be implanted. The contralateral ear can be also implanted even before explantation to avoid a period without any device. In our study, second cochlear implantation was done in 73.6 % of cases (n = 14). In all but two cases requiring second explantation it was well tolerated.

Conclusions

MSFC after cochlear implantations are rare, but their treatment is complex and difficult. Revision surgery with resection of infected tissue and formation of a rotational two-layer flap preceded and supplemented by intensive targeted antibiotic therapy can be effective and should be the first treatment option. Spontaneous implant explantation, abscess or unsuccessful primary treatment are indications for implant removal as the ultimate solution. Explantation, if possible, should be preceded or followed by cochlear implantation on the contralateral ear, or followed by reimplantation of the same ear after wound healing.