Reporting guideline: STROBE
A retrospective review was done for mastoidectomies performed between July 2011 and July 2018 by 2 senior surgeons were identified via the electronic surgical logbook. Patients with primary cholesteatomas were included, excluding congenital cholesteatomas and incomplete data. Data extracted comprised preoperative demographics, high-resolution CT (HRCT) 0.5mm thickness temporal bone scan results, intraoperative findings and hearing results.
Diagnostic accuracy and correlations of non-contrast HRCT scans with intraoperative findings were analysed for 1) erosion of structures: ossicular chain, tegmen tympani, tympanic facial canal and semicircular canal, 2) location of squames and 3) ossicular chain encasement. The technique of matrix preservation or removal was dependent on surgeon choice and intraoperative findings, such as presence of intact endosteum. Material to repair LFs was also noted. Average air conduction (AC), bone conduction (BC) and air-bone gap (ABG) pure tone threshold (PTA) were performed at 500Hz, 1kHz and 2kHz for all patients pre- and post-operatively. A change of BC PTA of 10dB or more is considered clinically significant.
Statistical analysis was conducted using chi square test using IBM SPSS statistic package, version 25. Cholesteatomas were categorized into “LF” and “No LF” groups. Continuous variables such as age and hearing levels were reported as mean (standard deviation, range). Comparisons of categorical variables were performed using the Pearson chi-squared test.