Acquisition of SafeOp Surgical, Inc.	12 Months Ended
Dec. 31, 2019
Business Combinations [Abstract]
Acquisition of SafeOp Surgical, Inc.	8. Acquisition of SafeOp Surgical, Inc. On March 8, 2018, the Company acquired SafeOp, a privately-held provider of neuromonitoring technology designed to enable effective intra-operative nerve health assessment. At the time of the acquisition, SafeOp had FDA 510(k) approval for a somatosensory evoked potential (“SSEP”) monitoring technology. The Company has developed a product that will allow for both free run and triggered specific recording of muscle activity, also known as Electromyography (“EMG”). The Company received FDA clearance for SafeOp’s EMG technology in February 2019 to complement the SSEP solution, and anticipates commercialization of the combined technology solution in mid-2019. In addition to expanding the Company’s market presence in lateral spine surgery, the Company believes that the SafeOp solution will allow it to integrate neuromonitoring into its broader product portfolio and accelerate the transition to procedural integration of the entire portfolio. Under the term of the definitive merger agreement, the Company paid $15.1 million in cash and issued 3,265,132 shares of common stock. The Company paid the full $15.1 million in cash consideration during the year ended December 31, 2018. On March 8, 2018, the Company issued 2,975,209 shares of common stock valued at $9.8 million, based on the closing share price of $3.30, and issued an additional 115,621 shares of common stock during the second quarter of 2018 and the remaining 174,302 during the third quarter of 2018. In March 2018, the Company also issued $3.0 million in convertible notes that were convertible into a total of 987,578 shares of common stock, which included total interest incurred, and issued warrants to purchase 2.2 million shares of common stock at an exercise price of $3.50 per share and contain a five year life. The convertible notes matured on March 9, 2019 and were settled in cash. Upon maturity, the Company recognized the value associated with the beneficial conversion feature calculated at issuance of $0.2 million within interest expense on the Company’s consolidated statement of operations for the year ended December 31, 2019. Shares of common stock were issued upon achievement of post-closing milestones as described further below. The warrants remain outstanding as of December 31, 2019. The first of the two milestones was achieved during the year ended December 31, 2018 and resulted in the issuance of 443,421 shares of common stock as payment. The second milestone pertaining to regulatory approval was achieved and the Company issued 886,843 shares of common stock as payment during the three months ended March 31, 2019. Prior to achievement, the contingent consideration was recorded as a liability and measured at fair value using a probability-weighted income approach, utilizing significant unobservable inputs including the probability of achieving each of the potential milestones and an estimated discount rate related to the risks of the expected cash flows attributable to the milestones. The fair value of the contingent consideration, and the associated liability relating to the contingent consideration at each reporting date, was re-assessed with the changes in fair value reflected in earnings. For the year ended December 31, 2019, the fair value for the contingent consideration increased by $0.3 million due to the proximity of the achievement of the milestone. The amount was recorded within research and development expense on the consolidated statement of operations and a corresponding increase in the liability on the Company’s consolidated balance sheet. The full liability was relieved upon achievement of the remaining milestone during the period.

Acquisition of SafeOp Surgical, Inc.

12 Months Ended

Dec. 31, 2019

8. Acquisition of SafeOp Surgical, Inc.

On March 8, 2018, the Company acquired SafeOp, a privately-held provider of neuromonitoring technology designed to enable effective intra-operative nerve health assessment. At the time of the acquisition, SafeOp had FDA 510(k) approval for a somatosensory evoked potential (“SSEP”) monitoring technology. The Company has developed a product that will allow for both free run and triggered specific recording of muscle activity, also known as Electromyography (“EMG”). The Company received FDA clearance for SafeOp’s EMG technology in February 2019 to complement the SSEP solution, and anticipates commercialization of the combined technology solution in mid-2019. In addition to expanding the Company’s market presence in lateral spine surgery, the Company believes that the SafeOp solution will allow it to integrate neuromonitoring into its broader product portfolio and accelerate the transition to procedural integration of the entire portfolio.

Under the term of the definitive merger agreement, the Company paid $15.1 million in cash and issued 3,265,132 shares of common stock. The Company paid the full $15.1 million in cash consideration during the year ended December 31, 2018. On March 8, 2018, the Company issued 2,975,209 shares of common stock valued at $9.8 million, based on the closing share price of $3.30, and issued an additional 115,621 shares of common stock during the second quarter of 2018 and the remaining 174,302 during the third quarter of 2018.

In March 2018, the Company also issued $3.0 million in convertible notes that were convertible into a total of 987,578 shares of common stock, which included total interest incurred, and issued warrants to purchase 2.2 million shares of common stock at an exercise price of $3.50 per share and contain a five year life. The convertible notes matured on March 9, 2019 and were settled in cash. Upon maturity, the Company recognized the value associated with the beneficial conversion feature calculated at issuance of $0.2 million within interest expense on the Company’s consolidated statement of operations for the year ended December 31, 2019. Shares of common stock were issued upon achievement of post-closing milestones as described further below. The warrants remain outstanding as of December 31, 2019.

The first of the two milestones was achieved during the year ended December 31, 2018 and resulted in the issuance of 443,421 shares of common stock as payment. The second milestone pertaining to regulatory approval was achieved and the Company issued 886,843 shares of common stock as payment during the three months ended March 31, 2019. Prior to achievement, the contingent consideration was recorded as a liability and measured at fair value using a probability-weighted income approach, utilizing significant unobservable inputs including the probability of achieving each of the potential milestones and an estimated discount rate related to the risks of the expected cash flows attributable to the milestones. The fair value of the contingent consideration, and the associated liability relating to the contingent consideration at each reporting date, was re-assessed with the changes in fair value reflected in earnings. For the year ended December 31, 2019, the fair value for the contingent consideration increased by $0.3 million due to the proximity of the achievement of the milestone. The amount was recorded within research and development expense on the consolidated statement of operations and a corresponding increase in the liability on the Company’s consolidated balance sheet. The full liability was relieved upon achievement of the remaining milestone during the period.