Resonance frequency analysis of osseo-integrated implants for bone conduction in a pediatric population - A novel approach for assessing stability for early loading

ObjectivesThe purpose of our study was to directly measure the stability of a bone anchored hearing device (BAHD) abutment using resonance frequency analysis (RFA) in a pediatric population. RFA was used to guide early loading of the abutment following single stage surgery.MethodsThe principle behind RFA is to obtain a numerical value relating to stability. A Smartpeg (1 cm commercially manufactured attachment) is screwed onto the abutment - its resonance in a magnetic field is measured with an Osstell recording device. The degree of movement (vibration) is inversely proportional to the stability of the abutment and a numerical figure, the Implant Stability Quotient (ISQ), is derived. RFA measurements were obtained at surgery, 4 weeks and 16 weeks post implant surgery. Patients were fitted with the new CochlearTM Baha® BI300 series implant using a one-stage procedure and based on RFA stability measures, loading of the sound processor occurred any time from 1 week after implant surgery if the RFA measure was 60 units or over.ResultsTwenty two consecutive patients were recruited. Eight patients had bilateral BAHD's fitted giving a total of 30 implants. The age range was 2-16 years with an average age of 9 years at time of fitting. The time interval from surgery to loading the processor ranged from 1 to 16 weeks, with an average time of 6 weeks. The mean ISQ value at time of surgery was 61.29 (95% CI = 2.03), at 4 weeks was 61.92 (95% CI = 2.97) and at 16 weeks was 63.45 (95% CI = 3.18).ConclusionsOur study shows we have been able to operate a successful program of earlier BAHD loading using single stage surgery in children. This is supported by favorable RFA measures of implant stability with average ISQ values of over 60 units.