Implantable Bone Conduction Hearing Aids

M. Kompis, M. -D. Caversaccio

• Publisher: S. Karger
• Year: 2011
• ISBN:
  9783805597005
• Topic: Medicine
• Subtopic: Physiotherapy, Physical Medicine & Rehabilitation

Three decades after the introduction of the first bone-anchored hearing aids, the available systems have improved significantly and the field is expanding faster than ever. New technologies such as digital signal processing have opened new avenues unique to bone conduction hearing aids. Better insights into the physiology of bone-conducted hearing have not only changed the field but also provided ideas for new areas of application.In this volume of Advances in Oto-Rhino-Laryngology, renowned researchers and experienced clinicians from all over the world present the latest findings and practices. Reviews on the theoretical background of bone conduction hearing, presentation of currently available hearing aid systems, chapters on monaural and binaural hearing with implantable bone conduction hearing aids, a comparison with conventional hearing aids and a glimpse into the future of implantable bone conduction hearing aids render this volume an invaluable reference book to ENT surgeons, audiologists, hearing aid acousticians and researchers alike.

Surgical Aspects

Kompis M, Caversaccio M-D (eds): Implantable Bone Conduction Hearing Aids.
Adv Otorhinolaryngol. Basel, Karger, 2011, vol 71, pp 63-72

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Complications of Bone-Anchored Hearing Devices

Jack J. Wazen · Benjamin Wycherly · Julie Daugherty

Silverstein Institute, Ear Research Foundation, Sarasota, Fla., USA

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Abstract

Complications of bone-anchored hearing devices occur with both soft issue and bone. 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. Bone complications are classified as either early or late. Early complications are due to failure of osseointegration, while late complications are usually the result of either chronic infection or trauma. Pediatric patients are a unique group of implant patients and are more likely to have complications of both soft tissue and bone. Most complications can be managed in the office with topical therapy and wound care, although revision surgery may be required in extensive skin overgrowth cases. Proper patient selection, meticulous surgical technique, and patient hygiene around the implant are the most critical aspects in minimizing complications in patients with osseointegrated implants.

Copyright © 2011 S. Karger AG, Basel

The principles of osseointegration and the surgical techniques have been covered elsewhere and will not be repeated in this chapter. Our focus here will be on the complications encountered in such surgery, how to treat them and how to avoid them. We will divide the complications into bone and soft tissue complications, and include a discussion of pediatric considerations.

The simplicity, high success rate and patient satisfaction in the osseointegrated auditory implants far outweigh the surgical risks and complications. However, failure to adhere to the basic surgical principles of the procedure has led to higher reported complication rates in some centers and patient populations. We will therefore describe the different types of complications and how to avoid them.

Bone Complications

Implant Loss

Complications related to the bone causing implant loss can be categorized as early (failure of osseointegration) or delayed (loss of osseointegration, or ‘disintegration’) [1].

Prerequisites for successful osseointegration include: status of bone, implant design, implant material and finish, surgical technique and implant loading conditions [2].

Numerous studies report various rates of bone complications and implant loss for bone-anchored hearing aid (Baha) recipients. Early failure of osseointegration resulting in implant loss ranged from 0.4 to 9.3% [3-5], while delayed implant loss caused by infection or trauma ranged from 0.4 to 2.7% [6-10]. Children have a higher rate of implant loss [11]. Faber et al. [12] propose the cause of the higher extrusion rate in children is that the child’s skull is thinner and has a lower mineral content compared to the adult skull. Skull thickness is not just dependent on age, but also related to craniofacial abnormalities such as in Treacher-Collins’ syndrome [13]. Reyes et al. [6] suggest that bone resorption at the bonemetal surface causes implant loss when there is no history of trauma. Implant loss rates in children range from 5.3 to 30%, with a greater proportion reported as early failures [14-17]. In a series of children implanted under the age of 5 years at The Birmingham BAHA program, an implant failure rate of 40% was reported [11]. Infection, incomplete implant insertion, failure of osseointegration and trauma have been reported as the main causes of implant loss in the pediatric population [13]. The evolution of the surgical technique to include placement of a spare implant (sleeper) in children during the initial surgery has reduced the rate of replacement surgery [3]. However, factors that contribute to loss of the primary implant may affect the integrity of the sleeper [13].

The implant size indicated for the pediatric population has been disputed by clinicians. Some studies report an increased implant loss rate with 3-mm implants [16, 18-19]. However, de Wolf et al. [3] and Lloyd et al. [14] found no significant difference in implant length and rate of implant loss. Further, they found no correlation between osseointegration in drill holes that ended in bone and those which exposed dura or the sigmoid sinus. Current evidence confirms the minimal temporal bone thickness needed to hold a 3-mm implant is 2.5 mm [20].

Other population subsets that have been identified to have an increased incidence of bone complications include patients with diabetes mellitus, chronic steroid use and smokers [21-24]. Animal studies have established that diabetes impedes osseointegration of titanium implants [25]. Studies show patients with pre-existing conditions that affect wound healing and bone density need longer than 3 months for complete osseointegration, and delayed loading with the processor to reduce the risk of implant extrusion [26]. No studies are available evaluating osseointegration in bone diseases. However, Uppal et al. [27] report successful Baha surgery and sustained osseointegration of an implant in a 72-year-old man with advanced Paget’s disease. Studies demonstrate that bone complications do not increase in the elderly population that is predisposed to diseases that diminish bone density, such as osteoporosis [18].

Another group that demonstrate a higher bone complication rate are patients who have undergone radiation therapy to the implant region. Ganström [28] found that the adjunctive use of hyperbaric oxygen therapy enhances osseointegration. In these patients and those with preexisting bone disease, the two-stage technique is recommended.

Clinical standards of care to promote osseointegration in Baha surgery include [18]:

– proper selection of the implant site, preferably along the temporalis line where the bone is thicker with smaller air cells

– fastidious surgical technique with constant cooling irrigation of the implant site and proper handling of the implant

– uninterrupted connection between bone and implant

– adequate healing time

– even distribution of stress over the implant

Bone Infection

The incidence of osteitis is quite rare, and even in cases of recurrent soft tissue infections, the bone appears to be quite resistant to infection. Only one case of an intracranial complication from a Baha has been reported in the literature [29]. This occurred after an unsuccessful attempt at changing the abutment and was subsequently complicated by prolonged postoperative wound infection that developed into an intracerebral abscess.

Soft Tissue Complications

Complications of Baha most commonly involve the soft tissue surrounding the implant. The goal of soft tissue handling in Baha surgery is decreased mobility of soft tissue relative to bone, hairless skin, and a gentle slope of the soft tissue toward the implant. Immobile skin reduces inflammation a...

Table of contents

• Cover Page
• Front Matter
• Historical Background of Bone Conduction Hearing Devices and Bone Conduction Hearing Aids
• Acoustic and Physiologic Aspects of Bone Conduction Hearing
• An Overview of Different Systems: The Bone-Anchored Hearing Aid
• The Ponto Bone-Anchored Hearing System
• Partially Implantable Bone Conduction Hearing Aids without a Percutaneous Abutment (Otomag): Technique and Preliminary Clinical Results
• Surgery for the Bone-Anchored Hearing Aid
• Paediatric Baha
• Complications of Bone-Anchored Hearing Devices
• Audiological Results with Baha®in Conductive and Mixed Hearing Loss
• Conductive Hearing Loss and Bone Conduction Devices: Restored Binaural Hearing?
• Bone-Anchored Devices in Single-Sided Deafness
• Factors Influencing the Decision for Baha in Unilateral Deafness: The Bern Benefit in Single-Sided Deafness Questionnaire
• Challenges and Recent Developments in Sound Processing for Baha®
• Headbands, Testbands and Softbands in Preoperative Testing and Application of Bone-Anchored Devices in Adults and Children
• Bone-Anchored Hearing Aids versus Conventional Hearing Aids
• The Future of Bone Conduction Hearing Devices
• Author Index
• Subject Index