INTRODUCTION
Surgically implanted bone conduction hearing devices come in three main categories: percutaneous, passive, and active transcutaneous devices (Audiol Res. 2021;11:207–219). The Cochlear OSIA 2 System is one of the most recent active transcutaneous bone conduction hearing devices. It is made up of the OSI200 implant, which contains a coil, magnet, and actuator fixated to the titanium BI300 implant (Cochlear Osia OSI200 Implant: Physician’s Guide). The OSIA 2 System is indicated for patients with conductive or mixed hearing loss with bone conduction pure tone average thresholds of ≤55 dB hearing level or single-sided deafness. The OSIA 2 System reduces the risk of signal attenuation and the skin complications, which were limitations of previous percutaneous and older transcutaneous devices (Cochlear Osia OSI200 Implant: Physician’s Guide). The authors present their surgical modifications to the placement of the OSIA 2 System with a minimally invasive technique that incorporates a bi-leveled small horizontal incision instead of the C- or J-shaped traditional incision, with minimal dissection and endoscopic-guided placement of the fixation screw. This modification shortens the operative time, and in our hands leads to less postoperative pain, intraoperative bleeding, and better esthetics. The technique is hereby described for the first time in children and we have implanted children below the 12 years limit currently set by the FDA.
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October 2023METHOD
Following ethical review board approval, we describe our approach and present a prospective pilot study of seven children with aural atresia who underwent a minimally invasive OSIA implant surgery (MOSIA). Outcomes reported were postoperative pain, numbness, surgical site infection, wound dehiscence, device exposure, patient satisfaction, and complications. The Wong–Baker faces pain scale designed by the International Association for the Study of Pain and/or the Face, Legs, Activity, Cry, Consolability pain scale were used by certified nurses in the post-anesthesia care unit to assess pain depending on age and development.
Surgical Planning
The OSI200 implant template was modified by creating a hole in the template’s neck with a 2-mm punch biopsy tool, 1.5 cm from the center of the pre-existing hole in the template. The template is then used to outline and mark the desired implant site. We followed the manufacturer’s recommendation and aligned the implant with the external auditory canal, taking care not to interfere with the pinna and placement of glasses (Cochlear Osia OSI200 Implant: Physician’s Guide). In children with microtia, the implant site was outlined approximately 5–6 cm from the presumed ear meatus to preserve the skin for future ear reconstruction. The skin thickness at the magnet location is then measured with a 25 g hypodermic needle and forceps, with a maximum thickness of 9 mm recommended for excellent magnet retention (Cochlear Osia OSI200 Implant: Physician’s Guide).
To prevent device exposure in case of wound breakdown, we injected methylene blue to mark two separate points: the implant site and the newly formed hole in the template’s neck. These markings serve to delineate two separate plane dissection levels, namely the skin level and the muscular/periosteal level. We believe this modification is important in decreasing the risk of implant exposure in case of dehiscence.
Incisions and Biplane Dissection Modifications
We used a transverse skin incision over the implant site rather than the linear, J-shaped, or posterior C-shaped incisions recommended by the manufacturer (Cochlear Osia OSI200 Implant: Physician’s Guide). The transverse skin incision allows for easier access and reduces dissection. We introduced the biplane dissection, subcutaneous and muscular/periosteal, at two different levels to prevent device exposure. The two methylene blue markings that were applied earlier assisted in identifying the two levels during dissection.