| Net Loss Per Share of Common Stock |
3. Net Loss Per Share of Common Stock Basic net loss per share of common stock is computed using the weighted average number of shares of common stock outstanding during the period. Diluted net loss per share is computed using the weighted average number of common stock, adjusted to include conversion of certain stock options and warrants for common stock and release of common stock in connection with restricted stock units during the period, as follows: | | | Years ended December 31, | | | | | 2017 | | 2016(1)
| | 2015 | | | Numerator: | | | | | | | | | | | | | | | | | | | | | | | | Net loss applicable to common stockholders | | $ | (29,122) | | $ | (33,815) | | $ | (24,245) | | | Adjustment for gain on fair value of warrant liability | | | - | | | (4,286) | | | (2,505) | | | Adjusted net loss used for dilution calculation | | $ | (29,122) | | $ | (38,101) | | $ | (26,750) | | | | | | | | | | | | | | | Denominator | | | | | | | | | | | | Weighted-average number of shares outstanding | | | 35,609 | | | 18,126 | | | 14,606 | | | Effect of potential dilutive shares | | | - | | | 496 | | | 3 | | | Dilutive weighted-average number of shares outstanding | | | 35,609 | | | 18,622 | | | 14,609 | | | | | | | | | | | | | | | Net loss per share applicable to common stockholders | | | | | | | | | | | | Basic | | $ | (0.82) | | $ | (1.87) | | $ | (1.66) | | | Diluted | | $ | (0.82) | | $ | (2.05) | | $ | (1.83) | | | (1) | Recognition of previously deferred revenue and cost of goods in the year ended December 31, 2016 reduced net loss applicable to common stockholders by $2,358, or $0.13 per share (see Note 2. Basis of Presentation and Summary of Significant Accounting Policies and Estimates – Medical Device Revenue and Cost of Revenue Recognition).
| The following potential dilutive securities were excluded from the computation of diluted net loss per share because including them would have been anti-dilutive: | | | Years ended December 31, | | | | | 2017 | | 2016 | | 2015 | | | Options to purchase common stock | | | 3,156 | | | 2,477 | | | 1,963 | | | Restricted stock units | | | 616 | | | - | | | - | | | Warrants for common stock | | | 3,396 | | | 1,963 | | | 1,963 | | | Common stock issuable upon conversion of preferred shares | | | - | | | - | | | 1,876 | | | Total common stock equivalents | | | 7,168 | | | 4,440 | | | 5,802 | |
|