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Comparison of two different titanium couplers for an active middle ear implant
Burkard Schwab1, Rolf Salcher, Magnus Teschner
1Department of Otolaryngology, Head and Neck Surgery, Hannover Medical School, Hannover, Germany.
Objective:
To compare surgical methods, functional gain, and speech discrimination using two different coupling methods for an active middle ear implant. Of several couplers enabling placement of the active element at various locations, two function directly at a cochlear membrane, bypassing a missing or malformed ossicular chain. This study evaluates whether either of these methods is more beneficial.
Study Design:
Retrospective case review.
Setting:
ENT surgical clinic.
Patients:
Forty-seven German-speaking patients with moderate to severe mixed hearing loss.
Interventions:
Records of patients implanted with either a round window (RW) or oval window (OW) coupler and active implant were examined. Preoperative and postoperative bone and air-conduction thresholds, auditory gain, and speech perception were compared.
Main Outcome Measures:
Functional gain, Freiburger monosyllables in quiet.
Results:
The range of hearing benefit shown by functional gain in patients implanted with the RW coupler (median) was between 22.5 dB (at 0.25 kHz) and 52.5 dB (2 and 3 kHz). In the OW group, improvement was similar, ranging from 21 dB (at 8 kHz) to 50 dB (1 and 2 kHz). Patients in both groups showed a similar improvement in speech recognition. Median preoperative unaided word recognition was 0% at 60 dB HL for both patient groups, improved postoperatively in both groups to median 85% correct at 65 dB HL and 95% at 80 dB HL.
Conclusion:
Placement of an active middle ear implant using the RW and the OW coupler was found to be safe, although the surgical methods differ. Safety and efficacy of both couplers present no significant differences.
