9. Stock-Based Compensation

The Company accounts for stock-based compensation arrangements with employees in accordance with Accounting Standards Codification (ASC) 718, Compensation—Stock Compensation. ASC 718 requires the recognition of compensation expense, using a fair value-based method, for costs related to all share-based payments including stock options. The Company estimates forfeitures expected to occur to determine the amount of compensation cost recognized in each period.

In addition to restricted stock units, the Company grants performance stock units (PSUs) to certain members of the management team. These PSUs vest over a three-year period, subject to continued service, and are based on (1) the total shareholder return (TSR) of the Company’s common stock price compared to the S&P Healthcare Equipment Select Industry Index (the Index) over a two-year period or (2) specific revenue targets over a two-year performance period. Additionally, in 2022, the Company made PSU grants to its then CEO that included attainment criteria that required the Company's stock price to reach certain pre-specified stock prices. Since TSR and stock price attainment are considered market conditions, the PSUs based on TSR and stock price attainment have fair values that are determined at the grant date using the Monte Carlo simulation model, with the recorded expense based on fair value. Since revenue targets are considered performance conditions, the PSUs based on revenue targets have a fair value that is equal to the closing stock price on the grant date, with the recorded expense based on the fair value and the probability of achievement, which is reassessed at each reporting period.