Evaluation of Soft Tissue Healing and Implant Stability of Cochlear Baha BI300/BA400 Implant System Loaded From 1 Week Post-surgery After Linear Incision Without Soft Tissue Reduction.

Background Implant stability

Until recently, the implants used in Baha surgery have exclusively been standard Brånemark type of titanium implants with an as-machined surface finish. The recommended procedure for Baha implantation with the machined titanium implants uses a 12-week healing period before loading the implant with a sound processor, in order to allow sufficient time for the implant to become integrated in the bone. The Cochlear Baha BI300 Series implant was designed to improve implant stability at placement and over time, thus making it possible to reduce the time to sound processor fitting. The implant features a wider diameter compared to the previous generation Baha implant, small-sized threads at the cylindrical portion of the implant underneath the flange, and a roughened implant surface due to formation of titanium oxide after blasting.

Six-month data from a multi-centre clinical investigation comparing the new implant with the previous generation Baha implant using a 6-week loading protocol, shows significantly higher Implant Stability Quotient (ISQ) values (measured by resonance frequency analysis) for the new implant at each time point, and no reduction in stability after loading (Dun et al., 2011). The data from the study suggest that the implant stability achieved 6 weeks after implantation is sufficient to support the sound processor. The data also suggest that a further reduction of the time to sound processor fitting may be possible, provided favourable bone conditions at the implant site and provided satisfactory soft tissue status at the time of loading. Hence, a clinical investigation with implant loading 21 days post-surgery was initiated by the team in Nijmegen, and 6-month data from the investigation confirm that it is safe to attach the sound processor after 3 weeks (Faber et al., 2012). Early results from two other studies using loading times of 4 weeks (McLarnon et al., 2012) and 2 weeks (Green et al., 2011), respectively, have also been presented and show good outcomes. All studies have been performed on patients with good bone quality.

Data from a prospective study with 49 patients loaded from 2 weeks post-surgery show no initial dip in stability and show no decrease in stability in the period after processor loading (ongoing study, awaiting publication). The stability of the implant in this study after one week is sufficient for processor loading at this time. No studies exist that investigates the effect on stability after processor loading 1 week postoperatively.

Implant stability measurement