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Príloha 3: Porovnanie odhadovaných nákladov verejného zdravotného poistenia Comparison of costs for compulsory health insurance The results of a cost effectiveness analysis using the above assumptions are shown in Table 1 below. Table 1: Cost-effectiveness Bonebridge vs. BAHA Strategy Incremental costs Utility BB £12,274.00 0.670 BAHA £ 13,699.00 0.590 ΔUtility Cost/QALY 0.08 £ 17,812.5 In total an average costs and incremental effect analysis wasestimated from 3 main sources: Snik, 2006, Hol, 2004, and Colquitt, 2011.The summarized calculation resulted in following estimates for adults patients: it shows that the Bonebridge has a cost effectiveness ratio (£ 17,812.5 per QALY) which is within the generally accepted range for surgical procedures that do not extend life. The overall difference between BAHA and a Bonebridge in terms of costs is £1,425.00. Choice of Comparator A number of medical and surgical options exist to treat middle and outer ear pathologies. The choice of treatment depends on a number of factors, including the degree and severity of the pathology, the prognosis of improvement, and the hearing status of the individual. In mild cases of conductive or mixed hearing loss and where a good prognosis of recovery is seen within a relatively short time frame, treatment with medication or a simple surgical procedure may be sufficient to resolve both the pathological condition and its effects on hearing. Limitations of Conventional Hearing Aids Conventional hearing aids are currently limited to the treatment of sensorineural hearing loss. A modern hearing aid consists of one or more microphone(s), a sound processing unit, an amplifier and a loudspeaker. Various types of hearing aids are available in these configurations: behind the ear (BTE), in the ear (ITE), in the canal (ITC), and completely in the ear canal (CIC). In the last decade, numerous improvements have been made in hearing aid technology on the basis of digitalization and miniaturization. However, conventional hearing aids have drawbacks, some of which are based on their technical and acoustic characteristics possibly due to their placement in or on the ear. A serious technical limitation of conventional hearing aids is that the output signals of their speakers are physically limited to approximately 5 kHz. In comparison, consonants in spoken language contain frequencies up to 8 kHz and the range of hearing goes up to 20 kHz. Additionally, in patients with an air-bone gap, the amplification of an air-conduction hearing aid needs to be increased substantially, as in contrast to a bone-conduction device (e.g., the BAHA), an air conduction hearing aid has to compensate for (part of) the air-bone gap. This can be a problem because the amplification and output levels of an air-conduction hearing aid are limited, owing to increased susceptibility to feedback and, as with every hearing aid, to possible saturation of the amplifier. Accordingly, as the width of the air-bone gap increases, patients’ performance with the air conduction hearing aid might gradually approach that with the BAHA. With an air-bone gap of 25 to 30 dB a breakeven point might be expected (Mylanus et al, 1998). An important physiological drawback of conventional hearing aids is that they occlude the external auditory canal. The ear mould must completely obdurade the ear in order to minimize direct acoustical feedback. However, tight moulds reduce wearing comfort and often lead to termination of use. Furthermore, ear moulds reduce aeration of the ear and thus increase the risk of infection in the external auditory canal. The conventional bone conduction hearing aid is difficult to use (Bance, 2002). A vibrator is pressed firmly against the skin of the skull by a steel spring coupled to a pressure band. The pressure from this often causes discomfort, pressure sores, and headache. To overcome these issues, patients often loosen the coupling and experience a resultant decline in acoustic transmission (Arlinger and Kylen, 1977). Even with good contact, the skin and subcutaneous tissues can damp the acoustic signals by up to 20 dB, resulting in poor sound quality (Håkansson et al, 1984; Mylanus et al, 1994a). Candidates for BCHAs fall into two main groups. The first group comprises of patients with congenital aural atresia; these patients cannot wear air conduction hearing aids and are therefore limited to bone conduction devices for amplification. The second group comprises of patients with chronically draining ears. This is the larger group in most BAHA series (Håkansson et al, 1994; Cooper et al, 1996). Often these patients have undergone tympanomastoid surgery and have draining mastoid cavity. Plugging the ear canal with an air conduction hearing aid may exacerbate the ear discharge. Benefits of Active Middle Ear Implants Implantable middle ear transducers can reduce these drawbacks considerably. For patients with sensorineural or conductive hearing loss and pathologies such as chronic otitis media, chronic otitis externa, psoriasis or a number of other dermatological pathologies of the ear, the Bonebridge or a bone anchored hearing aid (BAHA) are the primary alternatives. The main comparator used in the economic model is therefore the BAHA device. Will the Bonebridge device be used in addition to or instead of the comparator? In the economic model the Bonebridge device would be used instead of the bone anchored hearing aid. How does the Bonebridge device differ from the comparator? Although both devices are designed for direct stimulation of the cochlea through bone conduction while bypassing the external auditory canal and middle ear of patients with a mixed or conductive hearing loss who cannot benefit or wear conventional hearing aids, the BAHA involves inserting a percutaneous bone screw into the cranium behind the ear. An abutment connects the sound processor to the implanted bone screw. Sound is transferred through vibration and is made possible through intimate contact between the BAHA system and the cranium. Therefore, the BAHA device consists of three parts: 1. A titanium screw that is surgically embedded in the skull that integrates with the skull over time (osseointegration), 2. A cone-shaped external abutment, which is exposed outside the skin that connects with the screw, and 3. A sound processor (hearing device) that clips onto the abutment and transmits sound vibrations to the external abutment of the titanium implant. The implant vibrates the skull and inner ear, which stimulates the nerve fibres of the inner ear, allowing hearing. The major difficulty with BAHAs is the need to clean the percutaneous screw daily and the substantial infection rate associated with the screw. In addition to the advantages outlined above, key points in favour of BB as opposed to the BAHA are as follows: Direct drive of the bone ensures effective stimulation. State-of-the-art signal processing provides good audiological outcomes. There is no force on the implant/transducer therefore making osseointegration largely irrelevant. The loss of screws associated with the BAHA is mostly due to the fact that the screw is subjected to significant forces from snapping on/off the sound processor or trauma. Good osseointegration is required to avoid screw failure. Skin infection rates and other complications arelow with the Bonebridge, as noted above,, and are reduced to the very low level associated with cochlear implants and middle-ear implants. The BAHA was originally indicated only for conductive and mixed hearing loss. In 2002, however, the BAHA was cleared by the FDA for use in the treatment of single-sided deafness (SSD), which is sensorineural in origin. The indications for use of the BAHA device to compensate for unilateral sensorineural hearing loss are: Profound to severe hearing loss on the affected side as indicated by air-conduction pure-tone thresholds worse than 90 dB hearing level. Poor ability to discriminate speech as indicated by speech discrimination score of worse than 15 %. Normal hearing on the contralateral side as indicated by pure-tone thresholds better than 20 dB hearing level. Candidates for the BAHA device should also be 5 years or older, have good manual dexterity or a caretaker to snap the device onto the implanted abutment and they should be capable of maintaining the necessary hygiene at the site of the abutment. Safety, efficacy and adverse events Long-term data on the safety and efficacy of the Bonebridge device is not yet available. The results of the first audiological tests following implantation clearly demonstrate the effectiveness of the device as a means for compensating for hearing loss. Furthermore, no adverse events have been recorded during the follow-up of these patients. Although no evidence on adverse events is available for the Bonebridge device, potential risks of device failure and risks associated to the surgery cannot be excluded. Since the design of the Bonebridge is similar i to cochlear implants, it may be assumed that the devices are associated with a similar risk of skin infection. In the case of cochlear implants, these are typically very low. All complications and treatments were systematically reviewed by Venail et al. (2008) with a maximum follow-up of 18 years. The risk of severe infection (eventually requiring explantation) was 1.4 % (7 of 500). These results indicate that the likelihood of skin infection or major adverse events associated with the Bonebridge are extremely low. The reliability of the Bonebridge device can be speculated based on long-term data for the Vibrant Soundbridge, and therefore can be expected to be very high. The cumulative survival rate, which is the percentage of implants that are still functioning after a given period is 99.29 % for the Vibrant Soundbridge after a period of 5 years. The major comparator of the BB, the BAHA implant, has on the contrary several complications. Recently several publications tried to assess the rate of complications and adverse event associated with the BAHA. A number of studies have shown that the rate and severity of skin reactions among BAHA users can be very high. Overall, the rate of severe skin reaction associated with BAHA use and found in the published literature ranges between 3.4% and 69.6%. For example, a recent article by Faber describes a retrospective study of 248 adult BAHA users (Faber et al, 2009). Skin reactions were observed in 130 patients (52.4 %): in 84 patients the most severe skin reaction was Holgers grade 1 (33.9 %), in 32 patients this was Holgers grade 2 (12.9 %), in 12 patients this was grade 3 (4.8 %), and only 2 patients had a grade 4 skin reaction (0.8 %) In this group, 46 patients (18.5 %) had a skin reaction that required treatment (classified as Holgers grade 2-4). This type of reaction occurred only once in 33 of the 46 patients (71.7 %). Due to the percutaneous nature of the device soft tissue complications are much more common and most often involve irritation of the skin surrounding the implant. Other complications include: skin flap necrosis, wound dehiscence, bleeding or hematoma formation, and persistent pain. (Wazen et al, 2011,Table 2 ). Table 2: Incidence of soft tissue complication (adapted from Wazen et al, 2011) Moreover, Siau reported that chronic implant site pain represents the main reason why implants are removed electively, and affects 2 per cent of all implants (Siau et al, 2012). This complication has important medico-legal implications and should be discussed when obtaining informed consent for implantation. Implant losses and revision surgery were addressed in a recent review from Tjellström with a worst-case scenario calculation that gives a total number of (13%) lost implants and of 2.2% rate of revision surgeries (Tjellström and Stalfors, 2012). Another potential complication is wound and scalp problems at the site of implant, or in the case of the BAHA device, the screw. These problems can take one of two forms: one is the shifting or extrusion of the implant, the other is an infection of the area surrounding the implant extrusion or the flap pulling apart and becoming vulnerable to infection. In such cases, patients are usually treated with a regimen of antibiotics. How does the Bonebridge device differ from the Vibrant Soundbridge? The Vibrant Soundbridge System (VSB) is a semi-implantable electromagnetic hearing device consisting of an implant and an external sound processor worn behind the ear. An external audio processor converts sound into electromagnetic waves and transmits them through the skin, which causes the implant and the ossicles to vibrate. The implant component of the system, called the Vibrating Ossicular Prosthesis (VORP), is attached to the incus, one of the three small bones (ossicles) in the middle ear. The VORP consists of the so-called Floating Mass Transducer (FMT), a conductor link, and an internal coil. The VORP converts the electromagnetic signals transmitted by the external sound processor into vibrations that directly drive and move the ossicles and amplify their natural movement. These vibrations then conduct the sound to the inner ear and are interpreted by the brain as sound. The audio processor is applied to the patient’s head after the patient has healed from surgery. This external component of the Soundbridge system contains a microphone, processing electronics and a battery for power. The audio processor is held to the patient’s head by a magnet. The VSB is intended to improve hearing acuity in patients who have mild to severe hearing loss and who cannot wear a standard acoustic hearing aid for medical or physiological reasons or who are dissatisfied with the level of sound perception or quality of sound provided by standard acoustic hearing aids. Under the current indication, the Soundbridge is used to treat persons with sensorineural, conductive and mixed hearing loss, who have a mild to severe hearing loss and desire an alternative to an acoustic hearing aid or require one for medical reasons. Prior to receiving the device, it is recommended that an individual have experience with appropriately fit hearing aids. 1. For the treatment of mild to severe SNHL, a patient should meet the following criteria: Pure-tone air-conduction threshold levels at or within the levels listed below (Table 3) and shown in Figure 1. Pure-tone air-conduction thresholds for both ears shall be within 20 dB HL of each other at the above frequencies. Air-bone gap at 0.5, 1, 2 and 4 kHz no greater than 10 dB HL at two or more of these frequencies. Normal tympanometry. A patient shall present a normal ear anatomy and shall not have previously undergone middle ear surgery. The patient shall have no history of post-adolescent, chronic middle ear infections or inner ear disorders such as vertigo or Meniere’s syndrome. Speech audiometry curve adequate to the respective PTA. Speech understanding > 50 % (at 65 dB SPL) for word lists with amplification or at most comfortable level under earphones. Currently have used a conventional hearing aid for at least 3 months and 4 hours per day prior to evaluation or not be able to wear or benefit from a conventional hearing aid for medical reasons. A patient shall be psychologically and emotionally stable with realistic expectations of the benefits and limitations of the VSB. The ear selected for implantation of the VSB shall be equal to or worse than the un-implanted ear. Table 3: Air conduction threshold levels for SNHL indication Frequency (kHz) 0.5 1 1.5 2 3 4 Lower Limit (dB HL) 10 10 10 15 25 40 Upper Limit (dB HL) 65 75 80 80 85 85 Figure 1: Indication range (Air conduction) for the Soundbridge for sensorineural hearing loss (SNHL) For this VSB indication range, there is no overlap present compared to the Bonebridge. The individual patient’s treatment, respectively, has to be decided by the medical doctor. 2. Patients with a mild to severe conductive and mixed hearing loss (C/MHL), who cannot successfully be treated with conventional middle ear surgery, should meet the following criteria: Pure-tone bone-conduction threshold levels at or within the levels listed below (Table 4) and shown in Figure 2. Stable bone conduction thresholds within the shaded area (Figure 2). Speech audiometry curve adequate to the respective PTA. Middle ear anatomy must facilitate the placement of the FMT on a suitable vibratory structure. Round window or the oval window must be accessible. Absence of active middle ear infections. Adequate motivation and expectations. Table 4: Bone conduction threshold levels for C/MHL indication Frequency (kHz) 0.5 1 1.5 2 3 Lower Limit (dB HL) 0 0 0 0 0 Upper Limit (dB HL) 45 50 55 65 65 Figure 2: Indication range (Bone conduction) for the Soundbridge for conductive and mixed hearing loss (C/MHL) For this indication, there is a clear overlap compared to the Bonebridge (Figure 3). Based on the audiological and medical evaluation of the individual patient, the decision which implant is the best solution has to be made by a medical doctor again, based on: Is there a bone conduction difference of greater than 15 dB HL between the ears? If yes, application of the Bonebridge might be contraindicated by an over-stimulation of the contralateral ear and therefore treatment with a VSB might be of more benefit for the patient. But further studies have to be done to prove this assumption. Patients, who need a higher degree of amplification, should also be treated with a VSB. In cases where the medical background of the patient does not allow a proper fixation of the VSB FMT and the bone conduction values are not at the lower end of the indication range, treatment with the Bonebridge may be favourable. Figure 3: Overlapping (bone conduction thresholds in indication ranges between VSB (violet) and BB (brown)) For chronically discharging ears where a middle ear implant is contraindicated the Bonebridge may be the method of choice.