Comparison of hearing thresholds obtained with Baha preoperative assessment tools and those obtained with the osseointegrated implant

We conducted a study of the Baha bone-anchored hearing aid system to quantify the difference between (1) hearing thresholds obtained through preoperative testing methods with the Baha sound processor attached to three different bone-conduction testing devices and (2) thresholds obtained postoperatively with the sound processor attached to a surgically placed osseointegrated titanium implant. Twenty-three patients underwent free-field testing in four situations: with the Baha sound processor attached to (1) the Baha Testband (transcutaneous transmission), (2) the Baha Softband (transcutaneous transmission), (3) a test rod (bone conduction via the teeth), and (4) the osseointegrated implant (percutaneous transmission). The main outcome measure was the result of a comparison of the thresholds obtained with the three preoperative test methods and those obtained with the osseointegrated implant. We found that aided thresholds obtained with the osseointegrated implant were significantly better (p < 0.05) than those obtained with the three preoperative test methods. The degree of superiority increased with higher frequencies. We conclude that thresholds of 1 to 18 dB better than those obtained by preoperative test methods can be expected postoperatively with the osseointegrated implant. The damping effect of sound transmission via the teeth or transcutaneously must be accounted for in making predictions of postoperative outcome.