Substantial Doubt about Going Concern [Policy Text Block]

Liquidity

The Company had an accumulated deficit of $753.4 million and working capital of $165.7 million as of June 30, 2021. The Company has not established sufficient sales revenues to cover its operating costs and believes it may require additional capital in the future to proceed with its operating plan.

The Company believes the COVID-19 pandemic will continue to negatively impact its operations and ability to implement its market development efforts, which will have a negative effect on its financial condition.

In the first quarter of 2021, the Company raised additional capital through equity offerings, including raising net proceeds of $73.4 million in a January 2021 public offering, $28.6 million in a January 2021 registered direct offering, and $27.3 million in an at-the-market offering launched in 2020 (the “2020 ATM Offering”). Also, outstanding Series B, C and D warrants were exercised in the six months ended June 30, 2021 for aggregate proceeds to the Company of $30.6 million.

In the second quarter of 2021, the Company launched the 2021 ATM Offering and raised proceeds, net of legal costs and commissions, of $1.0 million under this offering in the three months ended June 30, 2021.

As of June 30, 2021, the Company had cash and cash equivalents, excluding restricted cash, of approximately $157.1 million.

While the Company believes that its existing cash and cash equivalents as of June 30, 2021 will be sufficient to sustain operations for at least the next 12 months from the issuance of these financial statements, the Company believes it may need to obtain additional financing in the future to proceed with its business plan. Management's plan to obtain additional resources for the Company may include additional sales of equity under the 2021 ATM Offering or otherwise, traditional financing, such as loans, entry into a strategic collaboration, entry into an out-licensing arrangement or provision of additional distribution rights in some or all of our markets. However, management cannot provide any assurance that the Company will be successful in accomplishing any or all of its plans.

Use of Estimates, Policy [Policy Text Block]

Use of Estimates

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. Significant items subject to such estimates and assumptions include impairment considerations for long- term intangible assets, fair value estimates related to contingent consideration, warrant liabilities, stock compensation expense, revenue recognition, accounts receivable reserves, excess and obsolete inventory reserves, inventory classification between current and non-current, measurement of lease liabilities and corresponding ROU assets, and deferred tax asset valuation allowances.

The COVID-19 pandemic has caused significant social and economic restrictions that have been imposed in the United States and abroad, which has resulted in significant volatility in the global economy and led to reduced economic activity. In the preparation of these financial statements and related disclosures, the Company has assessed the impact that COVID-19 has had on its estimates, assumptions, forecasts, and accounting policies. The Company continues to monitor closely the COVID-19 pandemic impact on its estimates, assumptions and forecasts used in the preparation of its financial statements. As the COVID-19 situation is unprecedented and ever evolving, future events and effects related to COVID-19 cannot be determined with precision, and actual results could significantly differ from estimates or forecasts.

Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block]

Cash and Cash Equivalents and Restricted Cash

The Company considers all highly liquid investments with original maturities of 90 days or less at the time of purchase to be cash equivalents.

Restricted cash as of June 30, 2021 and December 31, 2020 includes $1.0 million and $1.2 million, respectively, in cash accounts held as collateral primarily under the terms of an office operating lease, credit cards, and automobile leases.

Receivable [Policy Text Block]

Accounts Receivable

Accounts receivable are recorded at net realizable value, which includes an allowance for estimated uncollectible accounts. The allowance for uncollectible accounts was determined on a customer specific basis based on deemed collectability. The allowance for doubtful accounts was $1.7 million and $1.8 million as of June 30, 2021 and December 31, 2020, respectively.

Goodwill and Intangible Assets, Policy [Policy Text Block]

Intellectual Property

Intellectual property consists of purchased patent rights and developed technology acquired as part of previous business acquisitions. Amortization of the patent rights is recorded using the straight-line method over the estimated useful life of the patents of 10 years. Amortization of the developed technology is recorded using the straight-line method over the estimated useful life of 5 to 7 years.

The Company periodically evaluates intellectual property for impairment whenever events or changes in circumstances indicate that the carrying amount may not be recoverable. To determine the recoverability, the Company evaluates the probability that future estimated undiscounted net cash flows will be less than the carrying amount of the assets. If such estimated cash flows are less than the carrying amount of the assets, then such assets are written down to their fair value. No impairment of intellectual property was identified during the three and six months ended June 30, 2021 and 2020.

Debt, Policy [Policy Text Block]

Notes Payable – Payroll Protection Program

The Company’s policy is to account for forgivable loans received through the U.S. Small Business Administration (the “SBA”) under the CARES Act Payroll Protection Program (“PPP”), as debt in accordance with ASC 470, Debt, and other related accounting pronouncements. The forgiveness of debt, in whole or part, is recognized once the debt is extinguished, which occurs when the Company is legally released from the liability by the SBA. Any portion of debt forgiven, adjusted for accrued interest forgiven and unamortized debt issuance costs, is recorded as a gain on extinguishment of debt, and presented in the condensed consolidated statements of operations and comprehensive loss. On June 10, 2021, the Company received notification from the SBA that the principal amount of its PPP loan of $2.8 million and related interest had been forgiven.

Warrant Liabilities [Policy Text Block]

Warrant Liabilities

The Company’s Series B Warrants (see Note 8) were measured at fair value using a simulation model which took into account, as of the valuation date, factors including the current exercise price, the expected life of the warrant, the current price of the underlying stock, its expected volatility, holding cost and the risk-free interest rate for the term of the warrant (see Note 3). The warrant liability was revalued at each reporting period and changes in fair value were recognized in the condensed consolidated statements of operations and comprehensive loss. The selection of the appropriate valuation model and the inputs and assumptions that are required to determine the valuation requires significant judgment and requires management to make estimates and assumptions that affect the reported amount of the related liability and reported amounts of the change in fair value. Actual results could differ from those estimates, and changes in these estimates are recorded when known. All remaining outstanding Series B Warrants were exercised in the first quarter 2021.

Revenue Recognition Leases, Operating [Policy Text Block]

Senhance System Leasing

The Company enters into lease arrangements with certain qualified customers. Revenue related to arrangements including lease elements are allocated to lease and non-lease elements based on their relative standalone selling prices. Lease elements generally include a Senhance System, while non-lease elements generally include instruments, accessories, and services. For some lease arrangements, the customers are provided with the right to purchase the leased System at some point during and/or at the end of the lease term. In some arrangements lease payments are based on the usage of the System.

In determining whether a transaction should be classified as a sales-type, operating, or direct financing lease, the Company considers the following terms at lease commencement: (1) whether title of the Senhance System transfers automatically or for a nominal fee by the end of the lease term, (2) whether the present value of the minimum lease payments equals or exceeds substantially all of the fair value of the leased System, (3) whether the lease term is for the major part of the remaining economic life of the leased System, (4) whether the lease grants the lessee an option to purchase the leased System that the lessee is reasonably certain to exercise, and (5) whether the underlying System is of such a specialized nature that it is expected to have no alternative use to the Company at the end of the lease term. All such arrangements through June 30, 2021 are classified as operating leases.

Revenue related to lease elements from operating lease arrangements is generally recognized on a straight-line basis over the lease term or based upon System usage and is presented as product revenue. Revenue related to lease elements from operating lease arrangements was approximately $0.3 million and $0.1 million for the three months ended June 30, 2021 and 2020, respectively, and $0.7 million and $0.2 million for the six months ended June 30, 2021 and 2020, respectively.

Research and Development Expense, Policy [Policy Text Block]

Research and Development Costs

Research and development expenses primarily consist of engineering, product development and regulatory expenses, incurred in the design, development, testing and enhancement of our products. Research and development costs are expensed as incurred.

Income Tax, Policy [Policy Text Block]

Income Taxes

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets or liabilities for the temporary differences between financial reporting and tax basis of the Company’s assets and liabilities, and for tax carryforwards at enacted statutory rates in effect for the years in which the asset or liability is expected to be realized. The effect on deferred taxes of a change in tax rates is recognized in income during the period that includes the enactment date. In addition, valuation allowances are established when necessary to reduce deferred tax assets and liabilities to the amounts expected to be realized. The Company has elected to account for global intangible low-taxed income (“GILTI”) as a period expense in the year the tax is incurred.

The Company recognizes the financial statement benefit of an income tax position only after determining that the relevant taxing authority would more likely than not sustain the position following audit. For tax positions meeting the more likely than not threshold, the amount recognized in the financial statements is the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement with the relevant taxing authority. The Company recognizes interest accrued related to unrecognized tax benefits and penalties in the provision for income taxes.

Tax regulations within each jurisdiction are subject to the interpretation of the related tax laws and regulations and require application of significant judgment. The Company is subject to U.S. federal and various state, local and foreign jurisdictions. Due to the Company’s net operating loss carryforwards, the Company may be subject to examination by authorities for all previously filed income tax returns.

Segment Reporting, Policy [Policy Text Block]

Segments

The Company operates in one business segment—the research, development and sale of medical device robotics to improve minimally invasive surgery. The Company’s chief operating decision maker (determined to be the Chief Executive Officer) does not manage any part of the Company separately, and the allocation of resources and assessment of performance are based on the Company’s consolidated operating results.

Approximately 77% and 27% of the Company’s total consolidated assets are located within the U.S. as of June 30, 2021 and December 31, 2020, respectively. The remaining assets are mostly located in Europe and are primarily related to the Company’s facility in Italy, and include intellectual property, other current assets, property and equipment, cash, accounts receivable, other long-term assets and inventory of $47.6 million and $56.8 million as of June 30, 2021 and December 31, 2020, respectively. Total assets outside of the United States amounted to 23% and 73% of total consolidated assets as of June 30, 2021 and December 31, 2020, respectively. Long-lived assets in the U.S. were 21% and 11%, Italy were 37% and 48%, and Switzerland were 40% and 41%, as of June 30, 2021 and December 31, 2020, respectively. The Company recognizes sales by geographic area based on the country in which the customer is based. For the three months ended June 30, 2021 and 2020, 25% and 24%, respectively, of net revenue were generated in the United States; while 53% and 56%, respectively, were generated in Europe; and 22% and 20% were generated in Asia. For the six months ended June 30, 2021 and 2020, 17% and 25%, respectively, of net revenue were generated in the United States; while 32% and 52%, respectively, were generated in Europe; and 51% and 23% were generated in Asia.