Techniques, Surfaces and Bacterial Invasion when Using Bone Anchored Hearing Implants

Background: Development of tissue preservation techniques in bone anchored hearing implant surgery has develop a minimally invasive technique (MIPS) which is a suture less surgical technique. Surfaces of abutments is an ongoing discussion whether to make the surface smooth or rough as is also the bacteria invasion around the abutment after insertion.

Methods: Data recorded from using the MIPS system included intra- and post-operative complications, surgical time, skin healing after surgery and Holgers scores. A prospective study using a machined surface compared to a polished one was performed in Sweden, also collecting bacterial samples for enumeration from the area around the abutment, on the abutment and in tissue in close relation to the abutment. Microbiological profiles were correlated to the clinical soft tissue manifestations.

Results: Intra-operative complications were rare and post-operative results show very fast healing with a low rate of skin reactions after using the MIPS technique (non-adverse skin reactions in 94.7% of follow-up visits).

The clinical parameters, and total viable bacteria per abutment or in tissue biopsies (CFU/mm²⁾ did not differ between polished and machined abutments. However, in the space between the skin and abutment the total CFU/mm² anaerobes, aerobes and staphylococci were significantly higher for the polished abutment. Staphylococcal species were commonly identified with the common skin colonizer S. epidermidis. S. aureus was isolated but only in about 50% of the samples. Anaerobic bacteria were detected in the tissue biopsies before implantation.

Conclusions: Minimally invasive Ponto surgery is a surgery with few intra-operative complications, excellent healing and good short-term skin tolerability. The modification of the abutment topography did not affect the clinical outcome during the first year. Biochemical identification of common species included S. epidermidis and S. aureus, where presence of S. aureus represents a risk factor for associated infections.