Abstract
Bone conduction devices (BCDs) are an important option for hearing rehabilitation. The surgery for implantation of percutaneous BCDs has been evolved to more minimally invasive procedures. The most widespread used procedure is the linear incision technique with tissue preservation (LITT-P). There is a trend to use punch only techniques like
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the standardized Minimally Invasive Ponto Surgery (MIPS) procedure. This thesis focusses on the development of these minimally invasive surgical techniques in order to substantiate an evidence based fundament.
Chapter 2 described our retrospective cohort study comparing the dermatome and linear incision technique with soft tissue reduction (LITT-R). These results showed no difference in (adverse) soft tissue reactions between these two surgical procedures, tough skin thickening was noticed significantly more after the dermatome technique. This led to the conclusion, in accordance with literature, that the LITT-R should be advocated.
Within the LITT-R, the implant could be placed inside or outside of the line of incision. Chapter 3 aimed to address this question. No differences were found in post-surgical soft tissue reactions in our large scale retrospective cohort study, so there was no preference for placement of the skin-penetrating abutment in the procedure of the LITT-R.
Chapter 4 showed our retrospective cohort study comparing the LITT-R with the linear incision technique with tissue preservation (LITT-P). No difference was found in soft tissue reactions. Adverse soft tissue reaction were significantly more encountered in the LITT-R cohort, though skin thickening was noticed more in the LITT-P group. This study substantiated the preference of the LITT-P over the LITT-R. Moreover, the LITT-P showed in previous studies favorable results in less numbness, shorter surgical time and cosmetics.
In Chapter 5, we described the 22 months results from our multicenter RCT comparing the LITT-P and MIPS. There were no differences in (adverse) soft tissue reactions, wound dehiscence, tissue overgrowth, pain and quality of life. The MIPS cohort had better results on surgical time, skin sensibility, cosmetic scores and skin sagging. The ISQ was higher in the LITT-P cohort at various intervals and a (non-significant) higher proportion of implants was lost in the MIPS group. Some hypotheses were postulated: angulated and/or incomplete insertion, risk of excessive heat generation and entrapment of soft tissue fragments in the osteotomy. In conclusion, both surgical procedures demonstrate favorable outcomes.
An example of advancements in the MIPS was the development of a new drilling system called MONO. Chapter 6 showed our experimental study on human temporal bone samples. The MONO drill bit was compared to the guide drills used for LITT-P and MIPS techniques in terms of dura response to drill trauma. The conclusion was that the MONO system was not more inclined to penetrate the dura than the conventional systems.
Chapter 7 presented our health economic cost analysis to between the MIPS and LITT-P technique. All costs in the perioperative and postoperative routing were considered during long-term follow-up, which led to a difference in mean cost per patient between both techniques of €77.83 in favor of the MIPS. Additional analysis of scenarios in which all patients were operated under general or local anesthesia or with recalculation when using current implant survival rates showed that differences were also in favor of the MIPS. It can be concluded that the MIPS is an economically responsible technique.
BCD surgery is dynamic and innovative. Ongoing developments should be expected. These future perspectives are in the field of optimization of the MIPS procedure, implementation of health economic aspects within BCD surgery and increasing focus on patient related outcome measures. Finally, the active transcutaneous BCDs are an interesting trend, which could avoid several complications of the percutaneous BCDs.
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