Management of the Incus Body in Ossiculoplasty

Abstract

Objective (1) Evaluate the sound transfer impact of removal of the incus body in ossicular chain reconstruction (OCR) using an incus strut prosthesis. (2) Provide basic science data to assist clinical decision making in ossiculoplasty. Study Design Basic science. Setting Cadaveric temporal bone research laboratory. Subjects and Methods Ossicular chain reconstruction with an incus strut prosthesis was performed on 7 human temporal bones with and without the incus body. The difference in round window membrane (RWM) peak-to-peak displacements (90-dB sound pressure level, 250-8000 Hz) using single-point laser Doppler vibrometry (LDV) was compared with observed baseline, intact ossicular chain values. Results Comparing OCR using an incus strut prosthesis to an intact ossicular chain across all 7 temporal bones, the largest differences in RWM velocity occurred at 1011 and 2011 Hz. With increasing frequencies, RWM velocities of the OCR approached the intact ossicular chain. Using a Wilcoxon rank-sum test comparing the ossicular chain with and without the incus body showed no statistically significant difference across all frequencies ( P = .925). Removing the incus body resulted in improved median RWM velocity (×10−2 mm/s) by 0.6 at 1011 Hz and a decrease of 0.6 at 2011 Hz. A rank-sum test to evaluate the difference at 1011 and 2011 Hz did not demonstrate statistical significance. Conclusion Removal of the incus body in OCR using an incus strut prosthesis did not significantly change sound transfer function of the middle ear relative to its preservation. Our data suggest the impact of the retained mass in OCR to be minimal.