Summary of Significant Accounting Policies | Note 2. Basis of presentation The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (GAAP). Use of estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts in the consolidated financial statements and accompanying notes. Actual results could differ materially from those estimates and assumptions. Management considers many factors in selecting appropriate financial accounting policies and controls and in developing the estimates and assumptions that are used in the preparation of these consolidated financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. The most significant estimates in the accompanying consolidated financial statements relate to revenue recognition and stock‑based compensation expense. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, this process may result in actual results differing materially from those estimated amounts used in the preparation of the consolidated financial statements. Foreign currency translation The accompanying consolidated financial statements are presented in United States (U.S.) dollars. The Company considers the local currency to be the functional currency for its international subsidiaries. Accordingly, their assets and liabilities are translated into U.S. dollars using the exchange rate in effect on the balance sheet date. Revenues and expenses are translated at average exchange rates prevailing throughout the periods presented. As a result, currency translation adjustments arising from period to period are charged or credited to accumulated other comprehensive income (loss) in stockholders’ equity. For the year ended December 31, 2018, the Company reported a gain from foreign currency translation adjustments of approximately $1.4 million. For the year ended December 31, 2017, the Company reported a loss from foreign currency translation adjustments of approximately $1.1 million and for the year ended December 31, 2016, the Company reported a gain from foreign currency translation adjustments of approximately $0.5 million. Unrealized gains and losses that arise from exchange rate fluctuations on transactions denominated in a currency other than the functional currency, primarily gains and losses on intercompany loans, are included in the consolidated statements of operations as a component of other (expense) income, net. For the year ended December 31, 2018, the Company reported a net foreign currency transaction loss of $1.6 million, for the year ended December 31, 2017, the Company reported a net foreign currency transaction gain of $1.0 million and for the year ended December 31, 2016, the Company reported a net foreign currency transaction loss of $0.4 million. Cash, cash equivalents and short-term investments The Company invests its excess cash in marketable securities, including money market funds, money market securities, bank certificates of deposits, corporate bonds, corporate commercial paper, U.S. government bonds and U.S. government agency bonds. For financial reporting purposes, liquid investment instruments purchased with an original maturity of three months or less are considered to be cash equivalents. Cash and cash equivalents are recorded at face value or cost, which approximates fair market value. The Company maintains cash balances in excess of amounts insured by the Federal Deposit Insurance Commission. Investments are stated at fair value as determined by quoted market prices. Investments are considered available for sale and, accordingly, unrealized gains and losses are included in accumulated other comprehensive income (loss) within stockholders’ equity. The Company’s entire investment portfolio, except for restricted cash, is considered to be available for use in current operations and, accordingly, all such investments are stated at fair value using quoted market prices and classified as current assets, although the stated maturity of individual investments may be one year or more beyond the balance sheet date. The Company did not have any trading securities or restricted investments at December 31, 2018, December 31, 2017 or December 31, 2016. Realized gains and losses and declines in value, if any, judged to be other‑than‑temporary on available for sale securities, are reported in other (expense) income, net. When securities are sold, any associated unrealized gain or loss previously reported as a separate component of stockholders’ equity is reclassified out of stockholders’ equity and recorded in the statements of operations in the period sold using the specific identification method. Accrued interest and dividends are included in other (expense) income, net. The Company periodically reviews its available for sale securities for other than temporary declines in fair value below the cost basis, and whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable. Restricted cash The Company had its bank issue a letter of credit in the amount of $8.8 million related to its Aliso Viejo, California office building lease, which will commence on May 1, 2019. The letter of credit is secured with an amount of cash held in a restricted account equal to its face value, or $8.8 million as of December 31, 2018. Beginning as of the first day of the thirty-seventh month of the lease term, and on each twelve month anniversary thereafter, the letter of credit will be reduced by 20% until the letter of credit amount has been reduced to $2.0 million. See Note 10. Commitments and Contingencies for additional information related to the Aliso Viejo, California office building lease and associated letter of credit commitment. Concentration of credit risk and significant customers Financial instruments, which potentially subject the Company to significant concentration of credit risk, consist primarily of cash, cash equivalents, short-term investments and accounts receivable. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. Additionally, the Company has established guidelines regarding investment instruments and their maturities which are designed to maintain preservation of principal and liquidity. The Company believes that the concentration of credit risk in its accounts receivable is mitigated by its credit evaluation process, relatively short collection terms and the level of credit worthiness of its customers. During the years ended 2018, 2017 and 2016, none of the Company’s customers accounted for more than 10% of revenues. Accounts receivable The Company sells its products directly to hospitals, ambulatory surgery centers and distributors in the U.S. and internationally. The Company periodically assesses the payment performance of these customers and establishes reserves for anticipated losses when necessary, which losses historically have not been significant and have not exceeded management’s estimates. Accounts receivable are recorded at the invoiced amount and do not bear interest. The Company maintains an allowance for doubtful accounts based on historical collection experience and expectations of future collection based on current market conditions. The allowance for doubtful accounts is management’s best estimate of the amount of probable credit losses. Account balances are charged against the allowance when it is probable the receivable will not be recovered. The Company’s allowance for doubtful accounts was approximately $0.7 million, $0.6 million and $0.5 million as of December 31, 2018, December 31, 2017 and December 31, 2016, respectively. Additionally, no customers accounted for more than 10% of net accounts receivable as of any such date. Inventory Inventory is valued at the lower of cost and net realizable value. Cost is determined by the first‑in, first‑out method. Management evaluates inventory for excess quantities and obsolescence and records an allowance to reduce the carrying value of inventory as determined necessary. Long lived assets Property and equipment is recorded at cost. Depreciation of property and equipment is generally provided using the straight‑line method over the estimated useful lives of the assets, which range from three to five years. Leasehold improvements are amortized over their estimated useful life or the related lease term, whichever is shorter. Maintenance and repairs are expensed as incurred. All long lived assets are reviewed for impairment in value when changes in circumstances dictate, based upon undiscounted future operating cash flows, and appropriate losses are recognized and reflected in current earnings to the extent the carrying amount of an asset exceeds its estimated fair value, determined by the use of appraisals, discounted cash flow analyses or comparable fair values of similar assets. The Company recorded no impairment charges during 2018, 2017 or 2016. Intangible assets Intangible assets are recorded at cost and are amortized over the estimated useful life. Intangible assets in the accompanying balance sheets are comprised of the cost of the Company’s buyout of a royalty payment obligation and the value of non-compete agreements entered with former international distributors. (See Note 5). Fair value of financial instruments The carrying amounts of cash equivalents, accounts receivable, accounts payable, and accrued liabilities are considered to be representative of their respective fair values because of the short‑term nature of those instruments. The valuation of assets and liabilities is subject to fair value measurements using a three‑tiered approach and fair value measurements are classified and disclosed by the Company in one of the following three categories: Level 1: Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2: Quoted prices for similar assets and liabilities in active markets, quoted prices in markets that are not active, or inputs which are observable, either directly or indirectly, for substantially the full term of the asset or liability; and Level 3: Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable (i.e., supported by little or no market activity). Revenue recognition Effective January 1, 2018, the Company adopted Accounting Standards Codification (ASC) 606, Revenue Recognition – Revenue from Contracts with Customers and its related amendments (ASC 606). The Company adopted the standard by applying the modified retrospective method to contracts that were not complete as of the date of initial application. The Company’s accounting for revenue under ASC 606 is materially consistent with the accounting for revenue under ASC 605 and therefore the cumulative effect of adoption was immaterial. The reported results for the year ended December 31, 2018 reflect the application of ASC 606 guidance, while the reported results for periods prior to January 1, 2018 were prepared under the guidance of ASC 605. The Company accounts for revenue in accordance with ASC 606 and applies the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the Company satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. As part of the Company's adoption of ASC 606, the Company elected to use the following practical expedients: (i) to exclude disclosures of transaction prices allocated to remaining performance obligations when the Company expects to recognize such revenue within one year; (ii) to expense costs as incurred for costs to obtain a contract when the amortization period would have been one year or less, which mainly includes the Company's internal sales force compensation program; (iii) to account for shipping and handling costs as fulfillment costs (i.e., as an expense) rather than promised service (i.e., a revenue element); and (iv) to exclude from revenue the taxes collected from customers relating to product sales which are remitted to governmental authorities. The Company derives its revenue from sales of its products in the United States and internationally. Customers are primarily comprised of ambulatory surgery centers and hospitals, with distributors being used in certain international locations where the Company does not have a direct commercial presence. The Company concluded that one performance obligation exists for the majority of its contracts with customers which is to deliver products in accordance with the Company’s normal delivery times. Revenue is recognized when this performance obligation is satisfied, which is the point in time when the Company considers control of a product to have transferred to the customer. Revenue recognized reflects the consideration to which the Company expects to be entitled in exchange for those products or services. The Company has determined the transaction price to be the invoice price, net of adjustments, which includes estimates of variable consideration for product returns. The Company offers volume-based rebate agreements to certain customers and, in these instances, the Company provides a rebate (in the form of a credit memo) at the contract’s conclusion, if earned by the customer. In such cases, the transaction price is allocated between the Company’s delivery of product and the issuance of a rebate at the contract’s conclusion for the customer to utilize on prospective purchases. The performance obligation to issue a customer’s rebate, if earned, is transferred over time and the Company’s method of measuring progress is the output method, whereby the progress is measured by the estimated rebate earned to date over the total rebate estimated to be earned over the contract period. The provision for volume-based rebates is estimated based on customers' contracted rebate programs and the customers’ projected sales levels. The Company periodically monitors its customer rebate programs to ensure the rebate allowance is fairly stated. The Company’s rebate allowance is included in accrued liabilities in the consolidated balance sheets and estimated rebates accrued were not material during the periods presented. Customers are not granted specific rights of return; however, the Company may permit returns of product from customers if such product is returned in a timely manner and in good condition. The Company provides a warranty on its products for one year from the date of shipment, and any product found to be defective or out of specification will be replaced at no charge during the warranty period. Estimated allowances for sales returns and warranty replacements are recorded at the time of sale of the product and are estimated based upon the historical patterns of product returns matched against sales, and an evaluation of specific factors that may increase the risk of product returns. Product returns and warranty replacements to date have been consistent with amounts reserved or accrued and have not been significant. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates which would affect net product revenue and earnings in the period such variances become known. Shipping and handling costs All shipping and handling costs are expensed as incurred and are charged to general and administrative expense. Charges to customers for shipping and handling are credited to general and administrative expense. Advertising costs All advertising costs are expensed as incurred. Advertising costs incurred during the years ended December 31, 2018, December 31, 2017 and December 31, 2016 were approximately $1.8 million, $2.1 million and $1.6 million, respectively. Income taxes Income taxes are accounted for using an asset and liability approach that requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of temporary differences between the financial reporting basis and the tax basis of the Company’s assets and liabilities at the applicable tax rates, along with net operating loss and tax credit carryovers. The Company records a valuation allowance against its deferred tax assets to reduce the net carrying value to an amount that it believes is more likely than not to be realized. Management has considered estimated taxable income and ongoing prudent and feasible tax planning strategies in assessing the amount of the valuation allowance. Based upon the weight of available evidence, which includes the Company’s historical operating performance and limited potential to utilize tax credit carryforwards, the Company has determined that total deferred tax assets should be fully offset by a valuation allowance. When the Company establishes or reduces the valuation allowance against its deferred tax assets, its provision for income taxes will increase or decrease, respectively, in the period such determination is made. The Company is required to file federal and state income tax returns in the United States and various other state jurisdictions. The Company also files income tax returns in the foreign countries in which its subsidiaries operate. The preparation of these income tax returns requires the Company to interpret the applicable tax laws and regulations in effect in such jurisdictions, which could affect the amount of tax paid by us. Additionally, the Company follows an accounting standard addressing the accounting for uncertainty in income taxes that prescribes rules for recognition, measurement, and classification in the consolidated financial statements of tax positions taken or expected to be taken in a tax return. The Tax Cuts and Jobs Act (the Act) was enacted on December 22, 2017 resulting in significant modifications to existing law. The Company follows the guidance of Staff Accounting Bulletin (SAB) 118, which provides additional clarification regarding the application of ASC 740 in situations where the Company does not have the necessary information available, prepared or analyzed in reasonable detail to complete the accounting for certain income tax effects of the Act for the reporting period in which the Act was enacted. SAB 118 provides for a measurement period beginning in the reporting period that includes the Act’s enactment and ending when the Company has obtained, prepared and analyzed the information needed in order to complete the accounting requirements, but in no circumstances should the measurement period extend beyond one year from the enactment date. The Company has completed its analysis of the Act’s income tax effects. In total, the Company recorded $25.2 million related to the remeasurement of deferred tax assets which was fully offset by a corresponding decrease in the valuation allowance. Further, the Company has recorded the tax impact of IRC Section 162(m) as amended by the Act, which resulted in a reduction to its deduction of compensation paid to covered executives. Research and development expenses Major components of research and development expense include personnel costs, preclinical studies, clinical trials and related clinical product manufacturing, materials and supplies, and fees paid to consultants. Research and development costs are expensed as goods are received or services are rendered. Costs to acquire technologies to be used in research and development that have not reached technological feasibility and have no alternative future use are also expensed as incurred. At each financial reporting date, the Company accrues the estimated unpaid costs of clinical study activities performed during a period by third party clinical sites with whom the Company has agreements that provide for fees based upon the quantities of subjects enrolled and clinical evaluation visits that occur over the life of the study. The cost estimates are determined based upon a review of the agreements and data collected by internal and external clinical personnel as to the status of enrollment and subject visits, and are based upon the facts and circumstances known to the Company at each financial reporting date. If the actual performance of activities varies from the assumptions used in the cost estimates, the accruals are adjusted accordingly. There have been no material adjustments to the Company’s prior period accrued estimates for clinical trial activities through December 31, 2018. Stock‑based compensation The Company recognizes compensation expense for all stock-based awards granted to employees and nonemployees, including members of its board of directors. The fair value of stock option awards is estimated at the grant date using the Black-Scholes option pricing model, and the portion that is ultimately expected to vest is recognized as compensation cost over the requisite service period using the straight-line method. The determination of the fair value-based measurement of stock options on the date of grant using an option pricing model is affected by the determination of the fair value of the underlying stock as well as assumptions regarding a number of highly complex and subjective variables. These variables include, but are not limited to, the Company’s stock price volatility over the expected term of the grants, and actual and projected employee stock option exercise behaviors. In the future, as additional empirical evidence regarding these estimates becomes available, the Company may change or refine its approach of deriving them, and these changes could impact the fair value-based measurement of stock options granted in the future. Changes in the fair value-based measurement of stock awards could materially impact the Company’s operating results. The fair values of stock option awards made to nonemployees are re-measured at each reporting period using the Black-Scholes option pricing model. Compensation expense for these stock option awards is determined by applying the re-measured fair values to the shares that have vested during a period. The fair value of restricted stock unit (RSU) awards made to employees and nonemployees is equal to the closing market price of the Company’s common stock on the grant date. Comprehensive income (loss) All components of comprehensive income (loss), including net (loss) income, are reported in the consolidated financial statements in the period in which they are recognized. Comprehensive income (loss) is defined as the change in equity during a period from transactions and other events and circumstances from non‑owner sources, including unrealized gains and losses on marketable securities and foreign currency translation adjustments. Net (loss) income per share Basic net (loss) income per share is calculated by dividing the net (loss) income by the weighted average number of common shares that were outstanding for the period, without consideration for common stock equivalents. For periods when the Company realizes a net loss, no common stock equivalents are included in the calculation of weighted average number of dilutive common stock equivalents as the effect of applying the treasury stock method is considered anti-dilutive. For periods when the Company realizes net income, diluted net income per share is calculated by dividing the net income by the weighted average number of common shares plus the sum of the weighted average number of dilutive common stock equivalents outstanding for the period determined using the treasury stock method. Common stock equivalents are comprised of stock options, RSUs outstanding under the Company’s stock option plans and shares issuable under the Company’s Employee Stock Purchase Plan (ESPP). The Company’s computation of net (loss) income per share is as follows (in thousands, except per share amounts): As of December 31, Numerator: Net (loss) income - basic $ (12,951) $ (92) $ 4,522 Denominator: Weighted average number of common shares outstanding - basic 35,317 34,381 32,928 Common stock equivalents from outstanding common stock options - - 3,514 Common stock equivalents for ESPP - - 16 Common stock equivalents from outstanding common stock warrants - - 1 Weighted average number of common shares outstanding - diluted 35,317 34,381 36,459 Basic net (loss) income per share $ (0.37) $ (0.00) $ 0.14 Diluted net (loss) income per share $ (0.37) $ (0.00) $ 0.12 Potentially dilutive securities not included in the calculation of diluted net (loss) income per share because to do so would be anti‑dilutive were as follows (in common stock equivalent shares, in thousands): As of December 31, Stock options outstanding 5,614 5,516 1,099 Unvested restricted stock units 244 173 — Employee stock purchase plan 3 28 — 5,861 5,717 1,099 Recently adopted accounting pronouncements In August 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments (ASU 2016-15), which provides guidance on how certain cash receipts and cash payments are to be presented and classified in the consolidated statement of cash flows. ASU 2016-15 was effective for the Company beginning on January 1, 2018 and was required to be adopted retrospectively. In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash (ASU 2016-18), which enhances and clarifies the guidance on the classification and presentation of restricted cash in the statement of cash flows. ASU 2016-18 was effective for the Company beginning on January 1, 2018 and was required to be adopted retrospectively. In January 2017, the FASB issued ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business (ASU 2017-01). The amendments are intended to help companies evaluate whether transactions should be accounted for as acquisitions (or disposals) of assets or businesses. When substantially all of the fair value of gross assets acquired is concentrated in a single asset (or a group of similar assets), the assets acquired would not represent a business. This introduces an initial required screening that, if met, eliminates the need for further assessment. To be considered a business, an acquisition would have to include an input and a substantive process that together significantly contribute to the ability to create outputs. To be a business without outputs, there will need to be an organized workforce. The ASU also narrows the definition of the term “outputs” to be consistent with how it is described in ASC 606. The amendments were effective for annual periods beginning after December 15, 2017, including interim periods within those periods with early adoption permitted. The Company adopted the guidance effective January 1, 2018 and the guidance did not have a material impact on its consolidated financial statements; however, any prospective impact to the Company’s consolidated financial statements will depend on the terms specified in any future transactions subject to the guidance in ASU 2017-01. In May 2017, the FASB issued ASU No. 2017-09, Compensation - Stock Compensation - Scope of Modification Accounting (ASU 2017-09). The standard provides clarification on when modification accounting should be used for changes to the terms or conditions of a share-based payment award. This standard does not change the accounting for modifications but clarifies that modification accounting guidance should only be applied if there is a change to the value, vesting conditions, or award classification and would not be required if the changes are considered non-substantive. The standard was effective for annual periods beginning after December 15, 2017, and interim periods within those annual periods and early adoption was permitted. The Company adopted the guidance on a prospective basis effective January 1, 2018 and the adoption of ASU 2017-09 did not have a material impact on its consolidated financial statements; however, any future impact to share-based compensation expense will depend on the terms specified in any new changes to share-based payment awards subsequent to the adoption. Recently issued accounting pronouncements not yet adopted In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) (ASU 2016-02), which amends the existing accounting standards for leases. In September 2017, the FASB issued ASU No. 2017-13 which provides additional clarification and implementation guidance on the previously issued ASU No. 2016-02. Under the new guidance, a lessee will be required to recognize a lease liability and right-of-use asset for all leases with terms in excess of twelve months. The new guidance also modifies the classification criteria and accounting for sales-type and direct financing leases, and requires additional disclosures to enable users of financial statements to understand the amount, timing, and uncertainty of cash flows arising from leases. Consistent with current guidance, a lessee’s recognition, measurement, and presentation of expenses and cash flows arising from a lease will continue to depend primarily on its classification. The accounting standard is effective for fiscal years beginning after December 15, 2018, including interim periods within those fiscal years. The Company has adopted the requirements of the new lease standard effective January 1, 2019 and has elected the optional transition method to apply the standard as of the effective date and therefore, the Company will not apply the standard to the comparative periods presented in the consolidated financial statements. The Company will elect the transition package of three practical expedients permitted within the standard, which eliminates the requirements to reassess prior conclusions about lease identification, lease classification, and initial direct costs. The Company will not elect the hindsight practical expedient, which permits the use of hindsight when determining lease term and impairment of right-of-use assets. Further, the Company will elect a short-term lease exception policy, permitting the Company to not apply the recognition requirements of this standard to short-term leases (i.e. leases with terms of 12 months or less) and an accounting policy to account for lease and non-lease components as a single component for certain classes of assets. The Company is finalizing its analysis of certain key assumptions that will be utilized at the transition date including the incremental borrowing rate. The primary effect of the new standard will be to record right-of-use assets and obligations for current operating leases which will have a material impact on the balance sheet and significant incremental disclosures in the financial statement footnotes. The transition adjustment is not expected to have a material impact on the statement of operations. In February 2018, the FASB issued ASU No. 2018-02, Income Statement – Reporting Comprehensive Income (Topic 220): R |