SI-BONE (SIBN) 10-Q 4 Aug 21 2021 Q2 Quarterly report Financial data

Cover

Cover - shares	6 Months Ended
	Jun. 30, 2021	Jul. 31, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2021
Document Transition Report	false
Entity File Number	001-38701
Entity Registrant Name	SI-BONE, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	26-2216351
Entity Address, Address Line One	471 El Camino Real
Entity Address, Address Line Two	Suite 101
Entity Address, City or Town	Santa Clara
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	95050
City Area Code	408
Local Phone Number	207-0700
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	SIBN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		33,271,020
Entity Central Index Key	0001459839
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q2
Amendment Flag	false

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 48,125	$ 53,581
Short-term investments	128,508	142,851
Accounts receivable, net of allowance for doubtful accounts of $264 and $263, respectively	11,894	13,611
Inventory	8,151	5,633
Prepaid expenses and other current assets	2,434	2,565
Total current assets	199,112	218,241
Property and equipment, net	7,868	4,527
Other non-current assets	352	374
TOTAL ASSETS	207,332	223,142
Current liabilities:
Accounts payable	3,918	3,271
Accrued liabilities and other	8,706	10,199
Total current liabilities	12,624	13,470
Long-term borrowings	39,630	39,455
Other long-term liabilities	880	854
TOTAL LIABILITIES	53,134	53,779
Commitments and contingencies
STOCKHOLDERS’ EQUITY
Preferred stock, $0.0001 par value; 5,000,000 shares authorized; no shares issued and outstanding	0	0
Common stock, $0.0001 par value; 100,000,000 shares authorized; 33,236,270 and 32,583,220 shares issued and outstanding, respectively	3	3
Additional paid-in capital	419,235	408,113
Accumulated other comprehensive income	460	524
Accumulated deficit	(265,500)	(239,277)
TOTAL STOCKHOLDERS’ EQUITY	154,198	169,363
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 207,332	$ 223,142

CONDENSED CONSOLIDATED BALANC_2

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 264	$ 263
Preferred stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Preferred stock authorized (in shares)	5,000,000	5,000,000
Preferred stock issued (in shares)	0	0
Preferred stock outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock authorized (in shares)	100,000,000	100,000,000
Common stock issued (in shares)	33,236,270	32,583,220
Common stock outstanding (in shares)	33,236,270	32,583,220

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Income Statement [Abstract]
Revenue	$ 22,194	$ 14,049	$ 42,636	$ 30,870
Cost of goods sold	2,375	2,117	4,575	4,049
Gross profit	19,819	11,932	38,061	26,821
Operating expenses:
Sales and marketing	23,084	15,755	44,006	35,036
Research and development	3,149	2,165	6,104	4,255
General and administrative	6,551	4,151	12,491	9,551
Total operating expenses	32,784	22,071	62,601	48,842
Loss from operations	(12,965)	(10,139)	(24,540)	(22,021)
Interest and other income (expense), net:
Interest income	46	329	107	827
Interest expense	(1,075)	(2,683)	(2,139)	(3,914)
Other income (expense), net	13	21	349	(136)
Net loss	(13,981)	(12,472)	(26,223)	(25,244)
Other comprehensive income (loss):
Changes in foreign currency translation	35	(2)	(80)	10
Unrealized gain (loss) on marketable securities	(5)	(85)	16	136
Comprehensive loss	$ (13,951)	$ (12,559)	$ (26,287)	$ (25,098)
Net loss per share, basic (in usd per share)	$ (0.42)	$ (0.44)	$ (0.80)	$ (0.91)
Net loss per share, diluted (in usd per share)	$ (0.42)	$ (0.44)	$ (0.80)	$ (0.91)
Weighted-average number of common shares used to compute basic net loss per share (in shares)	32,978,914	28,492,582	32,836,040	27,872,505
Weighted-average number of common shares used to compute diluted net loss per share (in shares)	32,978,914	28,492,582	32,836,040	27,872,505

CONDENSED CONSOLIDATED STATEM_2

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Stockholders' equity, beginning of period (in shares) at Dec. 31, 2019		25,163,803
Stockholders' equity, beginning of period at Dec. 31, 2019	$ 63,008	$ 3	$ 258,121	$ 464	$ (195,580)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock from public offering, net of underwriting discounts, commissions and offering costs (in shares)		3,135,053
Issuance of common stock from public offering, net of underwriting discounts, commissions and offering costs	62,978		62,978
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		43,334
Issuance of common stock upon exercise of stock options, net of shares withheld	174		174
Issuance of common stock upon vesting of restricted stock units (in shares)		63,938
Stock-based compensation	2,622		2,622
Vesting of early exercised stock options	27		27
Foreign currency translation	12			12
Net unrealized gain on marketable securities	221			221
Net loss	(12,772)				(12,772)
Stockholders' equity, end of period (in shares) at Mar. 31, 2020		28,406,128
Stockholders' equity, end of period at Mar. 31, 2020	116,270	$ 3	323,922	697	(208,352)
Stockholders' equity, beginning of period (in shares) at Dec. 31, 2019		25,163,803
Stockholders' equity, beginning of period at Dec. 31, 2019	63,008	$ 3	258,121	464	(195,580)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Foreign currency translation	10
Net unrealized gain on marketable securities	136
Net loss	(25,244)
Stockholders' equity, end of period (in shares) at Jun. 30, 2020		28,612,451
Stockholders' equity, end of period at Jun. 30, 2020	107,868	$ 3	328,079	610	(220,824)
Stockholders' equity, beginning of period (in shares) at Mar. 31, 2020		28,406,128
Stockholders' equity, beginning of period at Mar. 31, 2020	116,270	$ 3	323,922	697	(208,352)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		46,608
Issuance of common stock upon exercise of stock options, net of shares withheld	185		185
Issuance of common stock related to employee stock purchase plan	991		991
Issuance of common stock related to employee stock purchase plan (in shares)		74,685
Issuance of common stock upon vesting of restricted stock units (in shares)		85,030
Stock-based compensation	2,955		2,955
Vesting of early exercised stock options	26		26
Foreign currency translation	(2)			(2)
Net unrealized gain on marketable securities	(85)			(85)
Net loss	(12,472)				(12,472)
Stockholders' equity, end of period (in shares) at Jun. 30, 2020		28,612,451
Stockholders' equity, end of period at Jun. 30, 2020	107,868	$ 3	328,079	610	(220,824)
Stockholders' equity, beginning of period (in shares) at Dec. 31, 2020		32,583,220
Stockholders' equity, beginning of period at Dec. 31, 2020	169,363	$ 3	408,113	524	(239,277)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		93,975
Issuance of common stock upon exercise of stock options, net of shares withheld	601		601
Issuance of common stock upon vesting of restricted stock units (in shares)		131,339
Stock-based compensation	4,030		4,030
Vesting of early exercised stock options	9		9
Foreign currency translation	(115)			(115)
Net unrealized gain on marketable securities	21			21
Net loss	(12,242)				(12,242)
Stockholders' equity, end of period (in shares) at Mar. 31, 2021		32,808,534
Stockholders' equity, end of period at Mar. 31, 2021	161,667	$ 3	412,753	430	(251,519)
Stockholders' equity, beginning of period (in shares) at Dec. 31, 2020		32,583,220
Stockholders' equity, beginning of period at Dec. 31, 2020	$ 169,363	$ 3	408,113	524	(239,277)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)	234,892
Foreign currency translation	$ (80)
Net unrealized gain on marketable securities	16
Net loss	(26,223)
Stockholders' equity, end of period (in shares) at Jun. 30, 2021		33,236,270
Stockholders' equity, end of period at Jun. 30, 2021	154,198	$ 3	419,235	460	(265,500)
Stockholders' equity, beginning of period (in shares) at Mar. 31, 2021		32,808,534
Stockholders' equity, beginning of period at Mar. 31, 2021	161,667	$ 3	412,753	430	(251,519)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock upon exercise of stock options, net of shares withheld (in shares)		140,917
Issuance of common stock upon exercise of stock options, net of shares withheld	650		650
Issuance of common stock related to employee stock purchase plan	1,566		1,566
Issuance of common stock related to employee stock purchase plan (in shares)		104,861
Issuance of common stock upon vesting of restricted stock units (in shares)		181,958
Stock-based compensation	4,257		4,257
Vesting of early exercised stock options	9		9
Foreign currency translation	35			35
Net unrealized gain on marketable securities	(5)			(5)
Net loss	(13,981)				(13,981)
Stockholders' equity, end of period (in shares) at Jun. 30, 2021		33,236,270
Stockholders' equity, end of period at Jun. 30, 2021	$ 154,198	$ 3	$ 419,235	$ 460	$ (265,500)

CONDENSED CONSOLIDATED STATEM_3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities
Net loss	$ (26,223)	$ (25,244)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation	8,287	5,577
Depreciation and amortization	845	505
Bad debt expense	0	200
Accretion (amortization) of discount on marketable securities	721	(20)
Realized gain on marketable securities	0	(43)
Amortization of debt issuance costs	175	100
Loss on extinguishment of debt	0	1,534
Loss on sale and disposal of property and equipment	125	80
Changes in operating assets and liabilities:
Accounts receivable	1,746	1,287
Inventory	(2,482)	500
Prepaid expenses and other assets	157	875
Accounts payable	554	(290)
Accrued liabilities and other	(1,415)	(2,289)
Net cash used in operating activities	(17,510)	(17,228)
Cash flows from investing activities
Maturities of marketable securities	56,977	33,500
Sales of marketable securities	0	12,592
Purchases of marketable securities	(43,337)	(34,768)
Purchases of property and equipment	(4,191)	(1,264)
Net cash provided by investing activities	9,449	10,060
Cash flows from financing activities
Proceeds from follow-on public offering, net of underwriting discounts, commissions and offering costs	0	62,978
Proceeds from debt financing	0	45,297
Principal repayments of debt financing	0	(45,297)
Payments of debt issuance costs	0	(589)
Payments of prepayment penalty and lender fees	0	(843)
Proceeds from issuance of common stock under employee stock purchase plan	1,566	991
Proceeds from the exercise of stock options	1,251	359
Net cash provided by financing activities	2,817	62,896
Effect of exchange rate changes on cash and cash equivalents	(212)	6
Net (decrease) increase in cash and cash equivalents	(5,456)	55,734
Cash and cash equivalents at
Beginning of period	53,581	10,435
End of period	48,125	66,169
Supplemental disclosure of non-cash information
Vesting of early exercised stock options	18	53
Unpaid purchases of property and equipment	106	145
Unpaid debt issuance costs	$ 0	$ 161

The Company and Nature of Busin

The Company and Nature of Business	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and Nature of Business	The Company and Nature of Business SI-BONE, Inc. (the “Company”) was incorporated in the state of Delaware on March 18, 2008 and is headquartered in Santa Clara, California. The Company is a medical device company that has pioneered a proprietary minimally invasive surgical implant system to fuse the sacroiliac joint for treatment of the most common types of sacroiliac joint disorders that cause lower back pain. The Company introduced its primary product, the iFuse Implant System, or iFuse, in 2009 in the U.S., in 2010 in certain countries in the European Union, and in 2015 in certain countries in the rest of the world. In the first quarter of 2020, the Company received $63.0 million of net proceeds from its first follow-on public offering of 4,300,000 shares of the Company's common stock, of which 2,490,053 shares were offered and sold by the Company, and the exercise of underwriter's option to purchase from the Company an additional 645,000 shares of the Company's common stock, at a public offering price of $21.50 per share. The total public offering costs incurred in connection with the follow-on offering were allocated based on the gross proceeds received by the Company and the other selling shareholders on a pro-rated basis. Public offering cost of $0.4 million allocated to selling of shares by the Company was charged against the gross proceeds received from the follow-on offering. Public offering costs of $0.2 million allocated to selling of shares by the selling shareholders was recognized as transaction costs within general and administrative expenses on the consolidated statements of operations in the year ended December 31, 2020. In October 2020, the Company received $71.6 million of net proceeds from its second follow-on public offering of shares of the Company's common stock, of which 3,000,000 shares were offered and sold by the Company, and the exercise of underwriter's option to purchase from the Company an additional 478,507 shares of the Company's common stock, at a public offering price of $22.00 per share. In addition to the shares sold by the Company in this second follow-on offering, the selling stockholder sold 190,053 shares of the Company's common stock previously held by the selling stockholder at a price to the public of $22.00 per share. The Company did not receive any proceeds from the sale by the selling stockholder. Risks and Uncertainties The Company is subject to continuing risk and uncertainties as a result of the COVID-19 pandemic, and is closely monitoring the impact of the pandemic on all aspects of its business, including the impacts on its customers, patients that would benefit from utilizing the Company's products, employees, suppliers, vendors, business partners and distribution channels. Economies worldwide continue to be negatively impacted by the COVID-19 pandemic, in particular with recurrent outbreaks and mutations of the virus, despite advances in vaccines, and the Company anticipates these disruptions will continue. As such the Company's future results of operations and liquidity could be adversely impacted by a variety of factors related to the COVID-19 pandemic, including those discussed in the section entitled "Risk Factors" of the Company's Annual Report on Form 10-K for the year ended December 31, 2020. As of the date of issuance of these condensed consolidated financial statements, the extent to which the COVID-19 pandemic may materially impact the Company's financial condition, liquidity, or results of operations remains uncertain. The Company is also subject to risks common to medical device companies including, but not limited to, new technological innovations, dependence on key personnel, protection of proprietary technology, compliance with government regulations, product liability, the ability to obtain adequate coverage and reimbursement from third-party payors and uncertainty of market acceptance of products. The Company is dependent on third-party manufacturers and suppliers, in some cases single source suppliers. The Company currently has limited long term contracts with its key suppliers and is subject to risks such as manufacturing failures, non-compliance with regulatory requirements, price fluctuations, inability to properly meet demand and third-party supplier discontinuation of operations.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2020 has been derived from the audited consolidated financial statements at that date but does not include all of the information required by GAAP for complete financial statements. These unaudited interim condensed consolidated financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments that are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three and six months ended June 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 or for any other interim period or for any other future year. The accompanying condensed consolidated financial statements should be read in conjunction with the audited financial statements and related notes thereto for the year ended December 31, 2020 contained in the Company’s Annual Report on Form 10-K filed with the SEC on March 10, 2021. 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 disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Estimates are based on historical experience, where applicable and other assumptions believed to be reasonable by the management. Actual results could differ from those estimates. Significant Accounting Policies The Company’s significant accounting policies are disclosed in the Company’s Annual Report on Form 10-K for the year ended December 31, 2020. There have been no material changes to these accounting policies. JOBS Act Accounting Election As an emerging growth company under the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”), the Company has been eligible to take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. The Company has elected to take advantage of the extended transition period for adopting new or revised accounting standards that have different effective dates for public and private companies. Those standards apply to companies until the earlier of the date that it is (i) no longer an emerging growth company or (ii) affirmatively and irrevocably opt out of the extended transition period provided in the JOBS Act. As a result, these condensed consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates. On June 30, 2021, the Company’s public float exceeded $700 million and as such the Company will be deemed to be a large accelerated filer under Rule 12b-2 of the Exchange Act, commencing with the Company’s Annual Report on Form 10-K for the 2021 fiscal year. The Company will retain its current filer status until the end of 2021. As a large accelerated filer, the Company will no longer qualify as an emerging growth company nor be eligible to rely on the benefits afforded to emerging growth companies under the JOBS Act. Segments The Company manages and operates as one reportable segment. The Company derives substantially all of its revenue from sales to customers in the U.S. Revenue by geography is based on billing address of the customer. No single country outside the U.S. accounts for more than 10% of the total revenue during the periods presented. Long-lived assets held outside the U.S. are immaterial. The table below summarizes the Company's revenue by geography: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (in thousands) United States $ 20,230 $ 13,221 $ 39,000 $ 28,518 International 1,964 828 3,636 2,352 $ 22,194 $ 14,049 $ 42,636 $ 30,870 Recently Issued Accounting Standards Not Yet Effective In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842), which requires that lessee's recognize a right-of-use asset and a lease liability for all leases with lease terms greater than twelve months in the balance sheet. A lease liability is a lessee's obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset is an asset that represents the lessee’s right to use, or control use of, a specified asset for the lease term for all leases (with the exception of short-term leases) at the adoption date. In July 2018, the FASB issued ASU 2018-10 and ASU 2018-11, which provides clarification on the narrow aspects of the guidance and provide an additional transition method to adopt the new leases standard. The new transition method allows an entity to recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. In March 2019, the FASB issued ASU 2019-01, which provides clarification on implementation issues associated with adopting ASU 2016-02. The new leases standard must be adopted using a modified retrospective transition method and allows for the application of the new guidance at the beginning of the earliest comparative period presented or at the adoption date. In November 2019, the FASB issued ASU 2019-10, which revised the mandatory effective dates of the new leases standard. Further, due to the impact of the COVID-19, in June 2020, the FASB issued ASU 2020-05 to further defer the effective date for one year for entities in the “all other” categories. For public companies, the new guidance became effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2018. For all other entities, the new guidance is now effective for fiscal years beginning after December 15, 2021 and interim periods within fiscal years beginning after December 15, 2022. Early adoption is still permitted for any interim or annual financial statements not yet issued. The Company expects to disclose the adoption of this standard for the fiscal year ending December 31, 2021. The Company is currently evaluating the impact of this standard on its consolidated financial statements including the timing of its adoption. The Company anticipates electing several practical expedients that permit the Company not to reassess (1) whether a contract is or contains a lease, (2) the classification of existing leases, and (3) whether previously capitalized initial direct costs would qualify for capitalization under ASC 842. The Company expects that the adoption of this new standard will have a material impact on its balance sheet. The most significant impact would be the recognition of operating lease right-of-use assets and liability. The standard is not expected to have a material impact to the Company's consolidated statements of income and cash flows. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. FASB issued ASU 2019-05 in May 2019, ASU 2019-08 and ASU 2019-11 in November 2019 for codification improvements of Topic 326. The new standard revises the accounting requirements related to the measurement of credit losses and will require organizations to measure all expected credit losses for financial assets based on historical experience, current conditions and reasonable and supportable forecasts about collectability. Assets must be presented in the financial statements at the net amount expected to be collected. In November 2019, the FASB issued ASU 2019-10, which defers the effective date of ASU 2016-13 for public companies that are eligible to be smaller reporting companies and all other companies, to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. In February 2020, the FASB issued ASU 2020-02, which provides guidance regarding methodologies, documentation, and internal controls related to expected credit losses. The Company is currently evaluating the impact of this standard on its consolidated financial statements but does not expect the standard will have a material impact on the Company's consolidated financial statements. The Company expects to disclose the adoption of this standard for the fiscal year ending December 31, 2021 In May 2021, the FASB issued ASU 2021-04 “Earnings Per Share (Topic 260), Debt—Modifications and Extinguishments (Subtopic 470-50), Compensation— Stock Compensation (Topic 718), and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815- 40) Issuer’s Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options” which clarifies and reduces diversity in an issuer’s accounting for modifications or exchanges of freestanding equity-classified written call options that remain equity classified after modification or exchange. An entity should measure the effect of a modification or an exchange of a freestanding equity-classified written call option that remains equity classified after modification or exchange as follows: i) for a modification or an exchange that is a part of or directly related to a modification or an exchange of an existing debt instrument or line-of-credit or revolving-debt arrangements (hereinafter, referred to as a “debt” or “debt instrument”), as the difference between the fair value of the modified or exchanged written call option and the fair value of that written call option immediately before it is modified or exchanged; ii) for all other modifications or exchanges, as the excess, if any, of the fair value of the modified or exchanged written call option over the fair value of that written call option immediately before it is modified or exchanged. The amendments in this update are effective for all entities for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years. An entity should apply the amendments prospectively to modifications or exchanges occurring on or after the effective date of the amendments. The Company is currently evaluating the impact of this update on its consolidated financial statements. While the Company does not expect the adoption of ASU 2021-04 to materially impact the Company's consolidated financial statements and related disclosures because it does not currently anticipate modifications to its outstanding equity-classified written call options, the impact on the Company's consolidated financial statements and disclosures will depend on the facts and circumstances of any specific future transactions.

Marketable Securities

Marketable Securities	6 Months Ended
	Jun. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Marketable Securities	Marketable Securities All of the Company's marketable securities were available-for-sale and were classified based on their maturities. Marketable securities with remaining maturities at the date of purchase of three months or less are classified as cash equivalents. Short-term investments are securities that original maturity or remaining maturity is greater than three months and not more than twelve months. Long-term investments are securities for which the original maturity or remaining maturity is greater than twelve months. The table below summarizes the marketable securities: June 30, 2021 Amortized Cost Unrealized Gains Unrealized Losses Aggregate Fair Value (in thousands) Money market funds $ 44,653 $ — $ — $ 44,653 Cash equivalents 44,653 — — 44,653 U.S. treasury securities 84,420 11 — 84,431 Corporate bonds 11,600 1 (1) 11,600 Commercial paper 32,477 — — 32,477 Short-term investments 128,497 12 (1) 128,508 Total marketable securities $ 173,150 $ 12 $ (1) $ 173,161 December 31, 2020 Amortized Cost Unrealized Gains Unrealized Losses Aggregate Fair Value (in thousands) Money market funds $ 45,948 $ — $ — $ 45,948 Commercial paper 1,400 — — 1,400 Cash equivalents 47,348 — — 47,348 U.S. treasury securities 74,779 4 (7) 74,776 Corporate bonds 8,940 4 (6) 8,938 Commercial paper 59,137 — — 59,137 Short-term investments 142,856 8 (13) 142,851 Total marketable securities $ 190,204 $ 8 $ (13) $ 190,199 Unrealized gains and losses on available-for-sale securities are recorded in accumulated other comprehensive income (loss) on the condensed consolidated balance sheets. The Company evaluates its investments to assess whether those in unrealized loss positions are other-than-temporarily impaired. The Company considers impairments to be other-than-temporary if it is related to deterioration in credit risk or if it is likely the Company will sell the securities before the recovery of their cost basis. The Company did not identify any of its marketable securities as other-than-temporarily impaired as of June 30, 2021 or December 31, 2020.

Fair Value Measurement

Fair Value Measurement	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Fair Value Measurement	Fair Value Measurement Carrying amounts of certain of the Company’s financial instruments, including cash equivalents, accounts receivable, accounts payable and accrued liabilities, approximate fair value due to their relatively short maturities and market interest rates, if applicable. The carrying value of the Company’s long-term debt also approximates fair value based on management’s estimation that a current interest rate would not differ materially from the stated rate. There were no other financial assets or liabilities that required fair value hierarchy measurements and disclosures for the periods presented. The table below summarizes the fair value of the Company’s marketable securities measured at fair value on a recurring basis based on the three-tier fair value hierarchy: June 30, 2021 Level 1 Level 2 Level 3 Total (in thousands) Marketable securities Money market funds $ 44,653 $ — $ — $ 44,653 U.S. treasury securities 84,431 — — 84,431 Corporate bonds — 11,600 — 11,600 Commercial paper — 32,477 — 32,477 Total marketable securities $ 129,084 $ 44,077 $ — $ 173,161 December 31, 2020 Level 1 Level 2 Level 3 Total (in thousands) Marketable securities Money market funds $ 45,948 $ — $ — $ 45,948 U.S. treasury securities 74,776 — — 74,776 Corporate bonds — 8,938 — 8,938 Commercial paper — 60,537 — 60,537 Total marketable securities $ 120,724 $ 69,475 $ — $ 190,199

Balance Sheet Components

Balance Sheet Components	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Balance Sheet Components	Balance Sheet Components Inventory As of June 30, 2021 and December 31, 2020, inventory consisted entirely of finished goods. Property and Equipment, net: June 30, 2021 December 31, 2020 (in thousands) Machinery and equipment $ 9,261 $ 6,342 Construction in progress 2,771 1,692 Computer and office equipment 869 714 Leasehold improvements 503 503 Furniture and fixtures 231 233 13,635 9,484 Less: Accumulated depreciation and amortization (5,767) (4,957) $ 7,868 $ 4,527 Construction in progress pertains to cost of individual components of a custom instrument set used for surgical placement of the Company’s products that have not yet been placed into service. Depreciation expense was $0.5 million and $0.3 million for the three months ended June 30, 2021 and 2020, respectively, and $0.8 million and $0.5 million for the six months ended June 30, 2021 and 2020, respectively. Accrued Liabilities and Other : June 30, 2021 December 31, 2020 (in thousands) Accrued compensation and related expenses $ 7,495 $ 9,175 Accrued professional services 459 511 Others 752 513 $ 8,706 $ 10,199

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Operating Leases The Company has a non-cancelable operating lease for an office building space, located in Santa Clara, California which expires in May 2025. The Company also has non-cancelable operating leases for its office building spaces in Gallarate, Italy and Knaresborough, United Kingdom, which expire in August 2027 and December 2025, respectively. Effective April 30, 2021, the Company terminated its office lease in Mannheim, Germany, and commenced a new lease that can be terminated at any time with six months written notice to the landlord. Further, the Company also leases vehicles under operating lease arrangements for certain of its personnel in Europe which expire at various times throughout 2021 to 2025. Rent expense is recorded over the lease terms on a straight-line basis. Rent expenses charged to operations under operating leases were $0.3 million for the three months ended June 30, 2021 and 2020, and $0.6 million for the six months ended June 30, 2021 and 2020. The table below summarizes aggregate future minimum lease payments under all leases as of June 30, 2021: Year ending December 31, (in thousands) Remainder of 2021 $ 576 2022 1,091 2023 995 2024 926 2025 385 Thereafter 24 $ 3,997 Purchase Commitments and Obligations The Company has certain purchase commitments related to its inventory management and training materials with certain suppliers wherein the Company is required to provide forecasts and purchase certain amounts included in such forecasts. The contractual obligations represent future cash commitments and liabilities under agreements with third parties and exclude orders for goods and services entered into in the normal course of business that are not enforceable or legally binding. These outstanding commitments amounted to $1.8 million and $0.3 million as of June 30, 2021 and December 31, 2020, respectively. Indemnification The Company enters into standard indemnification arrangements in the ordinary course of business. Pursuant to these arrangements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified parties for losses suffered or incurred by the indemnified party, in connection with any trade secret, copyright, patent or other intellectual property infringement claim by any third-party with respect to the Company’s technology. The term of these indemnification agreements is generally perpetual. The maximum potential amount of future payments the Company could be required to make under these agreements is not determinable because it involves claims that may be made against the Company in the future, but have not yet been made. The Company has entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers, other than liabilities arising from willful misconduct of the individual. The Company has not incurred costs to defend lawsuits or settle claims related to these indemnification agreements. No liability associated with such indemnifications has been recorded to date.

Borrowings

Borrowings	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Borrowings	Borrowings Term Loan The following table summarizes the outstanding borrowings from the term loan described below, as of the dates presented: June 30, 2021 December 31, 2020 (in thousands) Principal outstanding and final fee $ 41,000 $ 41,000 Less: Unamortized debt issuance costs (587) (661) Unaccreted value of final fee (783) (884) Outstanding debt, net of debt issuance costs and unaccreted value of final fee $ 39,630 $ 39,455 Classified as: Long-term borrowings $ 39,630 $ 39,455 In October 2017, the Company entered into a term loan with Biopharma Credit Investments IV Sub LP (“Pharmakon”) in for total loan proceeds of $40.0 million (the “Pharmakon Term Loan”). The Pharmakon Term Loan included an interest-only period for 35 months through September 2020 and then equal quarterly principal payments plus interest through December 2022. The Pharmakon Term Loan carried a fixed interest rate of 11.5% and allowed for early prepayment. The prepayment penalty fee was equal to the remaining interest due if prepaid within the first 30 months, a 2% penalty for months 31-48, and a 1% penalty for months 49-60. The Company paid in full and terminated the Pharmakon Term Loan in May 2020. The outstanding debt as of June 30, 2021 and December 31, 2020 is related to a term loan pursuant to the Loan and Security Agreement dated May 29, 2020, entered into by the Company with Solar Capital Partners (“Solar”). Pursuant to the Loan and Security Agreement, Solar provided an aggregate principal amount of $40.0 million term loan (the “Solar Term Loan”). The total debt issuance costs of $0.8 million associated with the Solar Term Loan were recorded in the condensed consolidated balance sheet as a direct deduction from the carrying amount of the loan, and are amortized as a component of interest expense using straight-line method over the life of the term loan. In accordance with the Loan and Security Agreement, the Company paid in full and terminated the Pharmakon Term Loan, which was accounted for as debt extinguishment in accordance with the accounting standards. The Company recognized the unamortized debt issuance costs of $0.7 million and the prepayment penalty and lender fees of $0.8 million related to Pharmakon Term Loan as a loss on debt extinguishment. The costs and fees are reflected as interest expense in the consolidated statement of operations for the year ended December 31, 2020. The Solar Term Loan bears interest at a rate per annum equal to 9.40% plus London Interbank Offered Rate (“LIBOR”), payable monthly in arrears. LIBOR means the greater of (i) 0.33% or (ii) one-month LIBOR (or a comparable replacement rate to be determined by the collateral agent if the LIBOR is no longer available), which rate shall reset monthly. The Solar Term Loan matures in 60 months on June 1, 2025 (“Maturity Date”), with an interest-only period of 36 months through June 2023, and then repaid in equal monthly principal payments plus interest through maturity date. Pursuant to the Loan and Security Agreement, the Company may voluntarily prepay the Solar Term Loan, in full or in part, but only in increments of $10.0 million, for a prepayment premium in an amount equal to 3.0% of the principal if prepaid in year one, 1.25% of the principal if prepaid in year two, and 0.50% of the principal if prepaid in year three or later. The prepayment premium will be waived if the Company voluntarily prepays and refinances the outstanding balance with Solar. The Solar Term Loan is secured by substantially all of the Company’s assets. The effective interest rate related to the Solar Term Loan was 10.6% for the three and six months ended June 30, 2021 and 11.8% and 12.0% for the three and six months ended June 30, 2020, respectively. The Company is also obligated to pay a final fee equal to $1.0 million or 2.5% of the aggregate principal amount of the Solar Term Loan, which was fully earned by Solar on the effective date of the Loan and Security Agreement. With respect to the Solar Term Loan, this final fee shall be due and payable on the earliest of (i) the maturity date, (ii) the acceleration of the loan balance or (iii) its full prepayment, refinancing, substitution or replacement. The final fee was included within the long-term borrowings and is accreted to interest expense using straight-line method over the life of the term loan. The table below summarizes the future principal and final fee payments under the Solar Term Loan as of June 30, 2021: Year ending December 31, (in thousands) 2021 (remaining six months) $ — 2022 — 2023 11,667 2024 20,000 2025 9,333 Total principal and final fee payments $ 41,000 Subject to other customary covenants set forth in the Loan and Security Agreement with Solar, the Company is required to maintain unrestricted cash and cash equivalents based on the trailing 12-month net products revenues tested on a monthly basis as follows: (a) $15.0 million if net product revenue is less than $75.0 million; or (b) $7.5 million if net product revenue is greater than or equal to $75.0 million, but less than $100.0 million (the “minimum liquidity requirement”). The Company is not subject to minimum liquidity requirement when trailing twelve-month net product revenues exceeds $100.0 million. Upon the occurrence of an event of default of certain customary covenants, including the minimum liquidity requirements, as specified in the Loan and Security Agreement, subject to specified cure periods, all amounts owed by the Company would begin to bear interest at a rate that is 5.0% above the rate effective immediately before the event of default and may be declared immediately due and payable by Solar. As of June 30, 2021, the Company was in compliance with all debt covenants. Though there are uncertainties surrounding the impact of the COVID-19 pandemic that may impact its future revenue, the Company believes that it has sufficient cash and cash equivalents to meet the minimum liquidity requirements in the foreseeable succeeding periods. CARES Act

Stock-Based Incentive Compensat

Stock-Based Incentive Compensation Plans	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Stock-Based Incentive Compensation Plans	Stock-Based Incentive Compensation Plans Stock Options The table below summarizes the stock option activity for the six months ended June 30, 2021: Number of Weighted- Outstanding as of December 31, 2020 2,405,957 $8.54 Exercised (234,892) 5.33 Canceled and forfeited (23,170) 16.02 Outstanding as of June 30, 2021 2,147,895 8.81 As of June 30, 2021, the unrecognized compensation cost related to stock options was $2.1 million, which is expected to be recognized over a period of approximately 1.4 years. There were no stock options granted during the three months ended June 30, 2020 and six months ended June 30, 2021. The table below summarizes the weighted average grant date fair value per share and the assumptions used to estimate the grant date fair value using the Black-Scholes option-pricing model of the stock options granted in the six months ended June 30, 2020: Six Months Ended June 30, 2020 Weighted average grant date fair value per share $8.37 Expected term (years) 5.5 to 7.0 Expected volatility 46.7% to 47.2% Risk-free interest rate 1.56% to 1.64% Dividend yield —% Early Exercise of Unvested Stock Options Early exercises of stock options under the Company's 2008 Stock Option Plan are subject to a right of repurchase by the Company of any unvested shares. The repurchase rights lapse over the original vesting period of the options. The Company accounts for the cash received in consideration for the early exercised options as a liability included in accrued liabilities, which is then reclassified to stockholders’ equity as the options vest. As of June 30, 2021 and December 31, 2020, the Company had a total of 1,945 shares and 5,836 shares of common stock, respectively, subject to repurchase under the Company's 2008 Stock Option Plan. Restricted Stock Units The table below summarizes restricted stock units activity for the six months ended June 30, 2021: Number of Shares Weighted Average Grant Date Fair Value Outstanding as of December 31, 2020 1,165,295 $20.07 Granted 1,000,129 29.72 Vested (313,297) 20.14 Canceled and forfeited (132,763) 25.51 Outstanding as of June 30, 2021 1,719,364 25.25 As of June 30, 2021, the unrecognized compensation cost related to the restricted stock units was $37.4 million, which is expected to be recognized over a period of approximately 3.1 years. Employee Stock Purchase Plan The Company’s 2018 Employee Stock Purchase Plan (the “ESPP”) allows eligible employees to purchase shares of the Company's common stock through payroll deductions at the price equal to 85% of the lesser of the fair market value of the stock as of the first date or the ending date of each six The fair value of the ESPP shares is estimated using the Black-Scholes option pricing model, which is being amortized over the requisite service period. The Company issued 104,861 shares and 74,685 shares under the ESPP, representing approximately $1.6 million and $1.0 million in employee contributions, for six months ended June 30, 2021 and June 30, 2020, respectively. As of June 30, 2021 and December 31, 2020, total accumulated ESPP related employee payroll deductions amounted to $0.3 million and $0.4 million, respectively, which were included within accrued compensation and related expenses in the condensed consolidated balance sheets. Stock-Based Compensation The table below presents the detail of stock-based compensation expense amounts included in the condensed consolidated statements of operations: Three Months Ended Six Months Ended 2021 2020 2021 2020 (in thousands) Cost of goods sold $ 129 $ 85 $ 303 $ 156 Sales and marketing 2,125 1,347 4,024 2,488 Research and development 404 288 823 528 General and administrative 1,599 1,235 3,137 2,405 $ 4,257 $ 2,955 $ 8,287 $ 5,577

Net Loss Per Share of Common St

Net Loss Per Share of Common Stock	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Net Loss Per Share of Common Stock	Net Loss Per Share of Common Stock The table below summarizes the computation of basic and diluted net loss per share: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (in thousands, except share and per share data) Net loss $ (13,981) $ (12,472) $ (26,223) $ (25,244) Weighted-average shares used to compute basic and diluted net loss per share 32,978,914 28,492,582 32,836,040 27,872,505 Net loss per share, basic and diluted $ (0.42) $ (0.44) $ (0.80) $ (0.91) Because the Company has reported a net loss in all periods presented, outstanding stock options, restricted stock units, shares subject to repurchase, ESPP purchase rights and common stock warrants are anti-dilutive and therefore diluted net loss per common share is the same as basic net loss per common share for the periods presented. The following anti-dilutive common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Stock options 2,147,895 2,652,683 2,147,895 2,652,683 Restricted stock units 1,719,364 1,333,501 1,719,364 1,333,501 Shares subject to repurchase 1,945 9,732 1,945 9,732 ESPP purchase rights 34,070 124,266 34,070 124,266 Common stock warrants 118,122 118,122 118,122 118,122 4,021,396 4,238,304 4,021,396 4,238,304

Related Party Transaction

Related Party Transaction	6 Months Ended
	Jun. 30, 2021
Related Party Transactions [Abstract]
Related Party Transaction	Related Party Transaction On February 24, 2020, the Company entered into a joint development agreement (the “Development Agreement”) with SeaSpine Orthopedics Corporation (“SeaSpine”) to develop a next generation device for sacropelvic fixation. Mr. Keith Valentine, who serves as the President, Chief Executive Officer and a member of the board of directors of SeaSpine, also serves as a member of the Company's Board of Directors since August 2015. On April 27, 2021, Addendum No.1 to the Development Agreement was entered into by and between the Company and SeaSpine to extend certain obligations as described under the Development Agreement to a consultant of the Company. Pursuant to the development plan, SeaSpine shall use reasonable efforts to assist in the development of the potential product offering, including licensing certain existing intellectual property to be incorporated into such product. Under the terms of the Development Agreement, the Company agreed to make monthly payments to SeaSpine to reimburse for full time resources employed by SeaSpine responsible to conduct the development activities. For the three months ended June 30, 2021 and 2020, the Company expensed $13,854 and $10,000, respectively, of the reimbursement charges from SeaSpine. For the six months ended June 30, 2021 and 2020, the Company expensed $23,854 and $44,000, respectively, of the reimbursement charges from SeaSpine. The reimbursement charges were recorded within research and development expense in the condensed consolidated statements of operations. There were no outstanding liabilities to SeaSpine as of June 30, 2021 and December 31, 2020.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2021
Income Tax Disclosure [Abstract]
Income Taxes	Income TaxesIn determining quarterly provisions for income taxes, the Company uses the annual estimated effective tax rate applied to the actual year-to-date profit or loss, adjusted for discrete items arising in that quarter. The Company updates its estimate of its annual effective tax rate at the end of each quarterly period. The estimate takes into account annual forecasted income (loss) before income taxes, the geographic mix of income (loss) before income taxes and any significant permanent tax items. The Company did not have provision for income taxes for the three and six months ended June 30, 2021 and 2020. The Company continues to maintain a full valuation allowance against its net deferred tax assets due to the uncertainty surrounding realization of such assets. The Company accounts for the uncertainty in income taxes by utilizing a comprehensive model for the recognition, measurement, presentation and disclosure in financial statements of any uncertain tax positions that have been taken or are expected to be taken on an income tax return. There had been no changes in the estimated uncertain tax benefits recorded as of December 31, 2020.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	The accompanying unaudited condensed consolidated financial statements have been prepared in accordance with generally accepted accounting principles in the United States of America (“U.S. GAAP”) and applicable rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by U.S. GAAP have been condensed or omitted, and accordingly the balance sheet as of December 31, 2020 has been derived from the audited consolidated financial statements at that date but does not include all of the information required by GAAP for complete financial statements.
Principles of Consolidation	These unaudited interim condensed consolidated financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments that are necessary for a fair statement of the Company’s consolidated financial information. The results of operations for the three and six months ended June 30, 2021 are not necessarily indicative of the results to be expected for the year ending December 31, 2021 or for any other interim period or for any other future year.
Use of Estimates	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 disclosure of contingent assets and liabilities as of the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. Estimates are based on historical experience, where applicable and other assumptions believed to be reasonable by the management. Actual results could differ from those estimates.
JOBS Act Accounting Election	JOBS Act Accounting Election As an emerging growth company under the Jumpstart Our Business Startups Act of 2012 (the “JOBS Act”), the Company has been eligible to take advantage of certain exemptions from various reporting requirements that are applicable to other public companies that are not emerging growth companies. The Company has elected to take advantage of the extended transition period for adopting new or revised accounting standards that have different effective dates for public and private companies. Those standards apply to companies until the earlier of the date that it is (i) no longer an emerging growth company or (ii) affirmatively and irrevocably opt out of the extended transition period provided in the JOBS Act. As a result, these condensed consolidated financial statements may not be comparable to companies that comply with the new or revised accounting pronouncements as of public company effective dates. On June 30, 2021, the Company’s public float exceeded $700 million and as such the Company will be deemed to be a large accelerated filer under Rule 12b-2 of the Exchange Act, commencing with the Company’s Annual Report on Form 10-K for the 2021 fiscal year. The Company will retain its current filer status until the end of 2021. As a large accelerated filer, the Company will no longer qualify as an emerging growth company nor be eligible to rely on the benefits afforded to emerging growth companies under the JOBS Act.
Segments	SegmentsThe Company manages and operates as one reportable segment.
Recently Adopted Accounting Pronouncement and Recently Issued Accounting Standards	Recently Issued Accounting Standards Not Yet Effective In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, Leases (Topic 842), which requires that lessee's recognize a right-of-use asset and a lease liability for all leases with lease terms greater than twelve months in the balance sheet. A lease liability is a lessee's obligation to make lease payments arising from a lease, measured on a discounted basis; and a right-of-use asset is an asset that represents the lessee’s right to use, or control use of, a specified asset for the lease term for all leases (with the exception of short-term leases) at the adoption date. In July 2018, the FASB issued ASU 2018-10 and ASU 2018-11, which provides clarification on the narrow aspects of the guidance and provide an additional transition method to adopt the new leases standard. The new transition method allows an entity to recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. In March 2019, the FASB issued ASU 2019-01, which provides clarification on implementation issues associated with adopting ASU 2016-02. The new leases standard must be adopted using a modified retrospective transition method and allows for the application of the new guidance at the beginning of the earliest comparative period presented or at the adoption date. In November 2019, the FASB issued ASU 2019-10, which revised the mandatory effective dates of the new leases standard. Further, due to the impact of the COVID-19, in June 2020, the FASB issued ASU 2020-05 to further defer the effective date for one year for entities in the “all other” categories. For public companies, the new guidance became effective for fiscal years, and for interim periods within those fiscal years, beginning after December 15, 2018. For all other entities, the new guidance is now effective for fiscal years beginning after December 15, 2021 and interim periods within fiscal years beginning after December 15, 2022. Early adoption is still permitted for any interim or annual financial statements not yet issued. The Company expects to disclose the adoption of this standard for the fiscal year ending December 31, 2021. The Company is currently evaluating the impact of this standard on its consolidated financial statements including the timing of its adoption. The Company anticipates electing several practical expedients that permit the Company not to reassess (1) whether a contract is or contains a lease, (2) the classification of existing leases, and (3) whether previously capitalized initial direct costs would qualify for capitalization under ASC 842. The Company expects that the adoption of this new standard will have a material impact on its balance sheet. The most significant impact would be the recognition of operating lease right-of-use assets and liability. The standard is not expected to have a material impact to the Company's consolidated statements of income and cash flows. In June 2016, the FASB issued ASU 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. FASB issued ASU 2019-05 in May 2019, ASU 2019-08 and ASU 2019-11 in November 2019 for codification improvements of Topic 326. The new standard revises the accounting requirements related to the measurement of credit losses and will require organizations to measure all expected credit losses for financial assets based on historical experience, current conditions and reasonable and supportable forecasts about collectability. Assets must be presented in the financial statements at the net amount expected to be collected. In November 2019, the FASB issued ASU 2019-10, which defers the effective date of ASU 2016-13 for public companies that are eligible to be smaller reporting companies and all other companies, to fiscal years beginning after December 15, 2022, including interim periods within those fiscal years. In February 2020, the FASB issued ASU 2020-02, which provides guidance regarding methodologies, documentation, and internal controls related to expected credit losses. The Company is currently evaluating the impact of this standard on its consolidated financial statements but does not expect the standard will have a material impact on the Company's consolidated financial statements. The Company expects to disclose the adoption of this standard for the fiscal year ending December 31, 2021 In May 2021, the FASB issued ASU 2021-04 “Earnings Per Share (Topic 260), Debt—Modifications and Extinguishments (Subtopic 470-50), Compensation— Stock Compensation (Topic 718), and Derivatives and Hedging—Contracts in Entity’s Own Equity (Subtopic 815- 40) Issuer’s Accounting for Certain Modifications or Exchanges of Freestanding Equity-Classified Written Call Options” which clarifies and reduces diversity in an issuer’s accounting for modifications or exchanges of freestanding equity-classified written call options that remain equity classified after modification or exchange. An entity should measure the effect of a modification or an exchange of a freestanding equity-classified written call option that remains equity classified after modification or exchange as follows: i) for a modification or an exchange that is a part of or directly related to a modification or an exchange of an existing debt instrument or line-of-credit or revolving-debt arrangements (hereinafter, referred to as a “debt” or “debt instrument”), as the difference between the fair value of the modified or exchanged written call option and the fair value of that written call option immediately before it is modified or exchanged; ii) for all other modifications or exchanges, as the excess, if any, of the fair value of the modified or exchanged written call option over the fair value of that written call option immediately before it is modified or exchanged. The amendments in this update are effective for all entities for fiscal years beginning after December 15, 2021, including interim periods within those fiscal years. An entity should apply the amendments prospectively to modifications or exchanges occurring on or after the effective date of the amendments. The Company is currently evaluating the impact of this update on its consolidated financial statements. While the Company does not expect the adoption of ASU 2021-04 to materially impact the Company's consolidated financial statements and related disclosures because it does not currently anticipate modifications to its outstanding equity-classified written call options, the impact on the Company's consolidated financial statements and disclosures will depend on the facts and circumstances of any specific future transactions.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2021
Accounting Policies [Abstract]
Schedule of Revenue by Geography	The table below summarizes the Company's revenue by geography: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (in thousands) United States $ 20,230 $ 13,221 $ 39,000 $ 28,518 International 1,964 828 3,636 2,352 $ 22,194 $ 14,049 $ 42,636 $ 30,870

Marketable Securities (Tables)

Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2021
Investments, Debt and Equity Securities [Abstract]
Schedule of Marketable Securities	The table below summarizes the marketable securities: June 30, 2021 Amortized Cost Unrealized Gains Unrealized Losses Aggregate Fair Value (in thousands) Money market funds $ 44,653 $ — $ — $ 44,653 Cash equivalents 44,653 — — 44,653 U.S. treasury securities 84,420 11 — 84,431 Corporate bonds 11,600 1 (1) 11,600 Commercial paper 32,477 — — 32,477 Short-term investments 128,497 12 (1) 128,508 Total marketable securities $ 173,150 $ 12 $ (1) $ 173,161 December 31, 2020 Amortized Cost Unrealized Gains Unrealized Losses Aggregate Fair Value (in thousands) Money market funds $ 45,948 $ — $ — $ 45,948 Commercial paper 1,400 — — 1,400 Cash equivalents 47,348 — — 47,348 U.S. treasury securities 74,779 4 (7) 74,776 Corporate bonds 8,940 4 (6) 8,938 Commercial paper 59,137 — — 59,137 Short-term investments 142,856 8 (13) 142,851 Total marketable securities $ 190,204 $ 8 $ (13) $ 190,199

Fair Value Measurement (Tables)

Fair Value Measurement (Tables)	6 Months Ended
	Jun. 30, 2021
Fair Value Disclosures [Abstract]
Schedule of Marketable Securities Measured at Fair Value on Recurring Basis	The table below summarizes the fair value of the Company’s marketable securities measured at fair value on a recurring basis based on the three-tier fair value hierarchy: June 30, 2021 Level 1 Level 2 Level 3 Total (in thousands) Marketable securities Money market funds $ 44,653 $ — $ — $ 44,653 U.S. treasury securities 84,431 — — 84,431 Corporate bonds — 11,600 — 11,600 Commercial paper — 32,477 — 32,477 Total marketable securities $ 129,084 $ 44,077 $ — $ 173,161 December 31, 2020 Level 1 Level 2 Level 3 Total (in thousands) Marketable securities Money market funds $ 45,948 $ — $ — $ 45,948 U.S. treasury securities 74,776 — — 74,776 Corporate bonds — 8,938 — 8,938 Commercial paper — 60,537 — 60,537 Total marketable securities $ 120,724 $ 69,475 $ — $ 190,199

Balance Sheet Components (Table

Balance Sheet Components (Tables)	6 Months Ended
	Jun. 30, 2021
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Property and Equipment, Net	Property and Equipment, net: June 30, 2021 December 31, 2020 (in thousands) Machinery and equipment $ 9,261 $ 6,342 Construction in progress 2,771 1,692 Computer and office equipment 869 714 Leasehold improvements 503 503 Furniture and fixtures 231 233 13,635 9,484 Less: Accumulated depreciation and amortization (5,767) (4,957) $ 7,868 $ 4,527
Schedule of Accrued Liabilities and Other	Accrued Liabilities and Other : June 30, 2021 December 31, 2020 (in thousands) Accrued compensation and related expenses $ 7,495 $ 9,175 Accrued professional services 459 511 Others 752 513 $ 8,706 $ 10,199

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
Schedule of Aggregate Future Minimum Lease Payments	The table below summarizes aggregate future minimum lease payments under all leases as of June 30, 2021: Year ending December 31, (in thousands) Remainder of 2021 $ 576 2022 1,091 2023 995 2024 926 2025 385 Thereafter 24 $ 3,997

Borrowings (Tables)

Borrowings (Tables)	6 Months Ended
	Jun. 30, 2021
Debt Disclosure [Abstract]
Schedule of Outstanding Borrowings	The following table summarizes the outstanding borrowings from the term loan described below, as of the dates presented: June 30, 2021 December 31, 2020 (in thousands) Principal outstanding and final fee $ 41,000 $ 41,000 Less: Unamortized debt issuance costs (587) (661) Unaccreted value of final fee (783) (884) Outstanding debt, net of debt issuance costs and unaccreted value of final fee $ 39,630 $ 39,455 Classified as: Long-term borrowings $ 39,630 $ 39,455
Schedule of Future Principal and Final Fee Payments	The table below summarizes the future principal and final fee payments under the Solar Term Loan as of June 30, 2021: Year ending December 31, (in thousands) 2021 (remaining six months) $ — 2022 — 2023 11,667 2024 20,000 2025 9,333 Total principal and final fee payments $ 41,000

Stock-Based Incentive Compens_2

Stock-Based Incentive Compensation Plans (Tables)	6 Months Ended
	Jun. 30, 2021
Share-based Payment Arrangement [Abstract]
Schedule of Stock Option Activity	The table below summarizes the stock option activity for the six months ended June 30, 2021: Number of Weighted- Outstanding as of December 31, 2020 2,405,957 $8.54 Exercised (234,892) 5.33 Canceled and forfeited (23,170) 16.02 Outstanding as of June 30, 2021 2,147,895 8.81
Schedule of Valuation Assumptions Related to Stock Option Awards	The table below summarizes the weighted average grant date fair value per share and the assumptions used to estimate the grant date fair value using the Black-Scholes option-pricing model of the stock options granted in the six months ended June 30, 2020: Six Months Ended June 30, 2020 Weighted average grant date fair value per share $8.37 Expected term (years) 5.5 to 7.0 Expected volatility 46.7% to 47.2% Risk-free interest rate 1.56% to 1.64% Dividend yield —%
Schedule of Restricted Stock Unit Activity	The table below summarizes restricted stock units activity for the six months ended June 30, 2021: Number of Shares Weighted Average Grant Date Fair Value Outstanding as of December 31, 2020 1,165,295 $20.07 Granted 1,000,129 29.72 Vested (313,297) 20.14 Canceled and forfeited (132,763) 25.51 Outstanding as of June 30, 2021 1,719,364 25.25
Schedule of Stock-Based Compensation	The table below presents the detail of stock-based compensation expense amounts included in the condensed consolidated statements of operations: Three Months Ended Six Months Ended 2021 2020 2021 2020 (in thousands) Cost of goods sold $ 129 $ 85 $ 303 $ 156 Sales and marketing 2,125 1,347 4,024 2,488 Research and development 404 288 823 528 General and administrative 1,599 1,235 3,137 2,405 $ 4,257 $ 2,955 $ 8,287 $ 5,577

Net Loss Per Share of Common _2

Net Loss Per Share of Common Stock (Tables)	6 Months Ended
	Jun. 30, 2021
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Loss per Share	The table below summarizes the computation of basic and diluted net loss per share: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 (in thousands, except share and per share data) Net loss $ (13,981) $ (12,472) $ (26,223) $ (25,244) Weighted-average shares used to compute basic and diluted net loss per share 32,978,914 28,492,582 32,836,040 27,872,505 Net loss per share, basic and diluted $ (0.42) $ (0.44) $ (0.80) $ (0.91)
Schedule of Anti-dilutive Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Share	The following anti-dilutive common stock equivalents were excluded from the computation of diluted net loss per share for the periods presented: Three Months Ended June 30, Six Months Ended June 30, 2021 2020 2021 2020 Stock options 2,147,895 2,652,683 2,147,895 2,652,683 Restricted stock units 1,719,364 1,333,501 1,719,364 1,333,501 Shares subject to repurchase 1,945 9,732 1,945 9,732 ESPP purchase rights 34,070 124,266 34,070 124,266 Common stock warrants 118,122 118,122 118,122 118,122 4,021,396 4,238,304 4,021,396 4,238,304

The Company and Nature of Bus_2

The Company and Nature of Business (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 31, 2020	Mar. 31, 2020	Dec. 31, 2020
First follow-on public offering
Subsidiary, Sale of Stock [Line Items]
Net proceeds from sale of stock		$ 63
Number of shares issued (in shares)		2,490,053
Public offering price (in dollars per share)		$ 21.50
Allocated public offering costs		$ 0.4
First follow-on public offering and secondary offering
Subsidiary, Sale of Stock [Line Items]
Number of shares in transaction, including shares in secondary offering (in shares)		4,300,000
Underwriters option
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)	478,507	645,000
Second follow-on public offering
Subsidiary, Sale of Stock [Line Items]
Net proceeds from sale of stock	$ 71.6
Number of shares issued (in shares)	3,000,000
Public offering price (in dollars per share)	$ 22
Secondary offering by selling shareholders
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)	190,053
Public offering price (in dollars per share)	$ 22
Allocated public offering costs			$ 0.2

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Narrative (Details)	6 Months Ended
	Jun. 30, 2021segment
Accounting Policies [Abstract]
Number of reportable segments	1
Number of operating segments	1

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Revenue by Geography (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Revenue	$ 22,194	$ 14,049	$ 42,636	$ 30,870
United States
Disaggregation of Revenue [Line Items]
Revenue	20,230	13,221	39,000	28,518
International
Disaggregation of Revenue [Line Items]
Revenue	$ 1,964	$ 828	$ 3,636	$ 2,352

Marketable Securities (Details)

Marketable Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Cash equivalents
Carrying Value	$ 44,653	$ 47,348
Short-term investments
Amortized Cost	128,497	142,856
Unrealized Gains	12	8
Unrealized Losses	(1)	(13)
Aggregate Fair Value	128,508	142,851
Total marketable securities, Amortized Cost	173,150	190,204
Total marketable securities, Unrealized Gains	12	8
Total marketable securities, Unrealized Losses	(1)	(13)
Total marketable securities, Aggregate Fair Value	173,161	190,199
Money market funds
Cash equivalents
Carrying Value	44,653	45,948
U.S. treasury securities
Short-term investments
Amortized Cost	84,420	74,779
Unrealized Gains	11	4
Unrealized Losses	0	(7)
Aggregate Fair Value	84,431	74,776
Corporate bonds
Short-term investments
Amortized Cost	11,600	8,940
Unrealized Gains	1	4
Unrealized Losses	(1)	(6)
Aggregate Fair Value	11,600	8,938
Commercial paper
Cash equivalents
Carrying Value		1,400
Short-term investments
Amortized Cost	32,477	59,137
Unrealized Gains	0	0
Unrealized Losses	0	0
Aggregate Fair Value	$ 32,477	$ 59,137

Fair Value Measurement (Details

Fair Value Measurement (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Marketable securities
Marketable securities	$ 173,161	$ 190,199
Money market funds
Marketable securities
Marketable securities	44,653	45,948
U.S. treasury securities
Marketable securities
Marketable securities	84,431	74,776
Corporate bonds
Marketable securities
Marketable securities	11,600	8,938
Commercial paper
Marketable securities
Marketable securities	32,477	60,537
Level 1
Marketable securities
Marketable securities	129,084	120,724
Level 1 | Money market funds
Marketable securities
Marketable securities	44,653	45,948
Level 1 | U.S. treasury securities
Marketable securities
Marketable securities	84,431	74,776
Level 1 | Corporate bonds
Marketable securities
Marketable securities	0	0
Level 1 | Commercial paper
Marketable securities
Marketable securities	0	0
Level 2
Marketable securities
Marketable securities	44,077	69,475
Level 2 | Money market funds
Marketable securities
Marketable securities	0	0
Level 2 | U.S. treasury securities
Marketable securities
Marketable securities	0	0
Level 2 | Corporate bonds
Marketable securities
Marketable securities	11,600	8,938
Level 2 | Commercial paper
Marketable securities
Marketable securities	32,477	60,537
Level 3
Marketable securities
Marketable securities	0	0
Level 3 | Money market funds
Marketable securities
Marketable securities	0	0
Level 3 | U.S. treasury securities
Marketable securities
Marketable securities	0	0
Level 3 | Corporate bonds
Marketable securities
Marketable securities	0	0
Level 3 | Commercial paper
Marketable securities
Marketable securities	$ 0	$ 0

Balance Sheet Components - Prop

Balance Sheet Components - Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Property and Equipment, Net
Property and equipment, gross	$ 13,635	$ 9,484
Less: Accumulated depreciation and amortization	(5,767)	(4,957)
Property and equipment, net	7,868	4,527
Machinery and equipment
Property and Equipment, Net
Property and equipment, gross	9,261	6,342
Construction in progress
Property and Equipment, Net
Property and equipment, gross	2,771	1,692
Computer and office equipment
Property and Equipment, Net
Property and equipment, gross	869	714
Leasehold improvements
Property and Equipment, Net
Property and equipment, gross	503	503
Furniture and fixtures
Property and Equipment, Net
Property and equipment, gross	$ 231	$ 233

Balance Sheet Components - Narr

Balance Sheet Components - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Depreciation expense	$ 0.5	$ 0.3	$ 0.8	$ 0.5

Balance Sheet Components - Accr

Balance Sheet Components - Accrued Liabilities and Other (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Accrued Liabilities and Other
Accrued compensation and related expenses	$ 7,495	$ 9,175
Accrued professional services	459	511
Others	752	513
Accrued liabilities and other	$ 8,706	$ 10,199

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Other Commitments [Line Items]
Rent expense	$ 300,000	$ 300,000	$ 600,000	$ 600,000
Purchase commitments related to inventory management and training materials	1,800,000		1,800,000		$ 300,000
Indemnification Agreement
Other Commitments [Line Items]
Costs to defend lawsuits or settle claims			0
Liability associated with indemnifications	$ 0		$ 0

Commitments and Contingencies_2

Commitments and Contingencies - Aggregate Future Minimum Lease Payments (Details) $ in Thousands	Jun. 30, 2021USD ($)
Aggregate Future Minimum Lease Payments
Remainder of 2021	$ 576
2022	1,091
2023	995
2024	926
2025	385
Thereafter	24
Total	$ 3,997

Borrowings - Summary of Borrowi

Borrowings - Summary of Borrowings (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Debt Disclosure [Abstract]
Principal outstanding and final fee	$ 41,000	$ 41,000
Less: Unamortized debt issuance costs	(587)	(661)
Unaccreted value of final fee	(783)	(884)
Outstanding debt, net of debt issuance costs and unaccreted value of final fee	39,630	39,455
Long-term borrowings	$ 39,630	$ 39,455

Borrowings - Narrative (Details

Borrowings - Narrative (Details) - USD ($)	May 29, 2020	Oct. 31, 2017	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Debt Instrument [Line Items]
Recognition of unamortized debt discount and issuance costs on debt extinguishment							$ 700,000
Prepayment penalty and lender fees on debt extinguishment							800,000
Final fee			$ 783,000		$ 783,000		884,000
Deferred liability for social security taxes, CARES Act			1,000,000		1,000,000		1,000,000
Proceeds from debt financing					0	$ 45,297,000
Accrued liabilities
Debt Instrument [Line Items]
Deferred liability for social security taxes, CARES Act			500,000		500,000		500,000
Other long-term liabilities
Debt Instrument [Line Items]
Deferred liability for social security taxes, CARES Act			$ 500,000		$ 500,000		$ 500,000
Term loan | Pharmakon Term Loan
Debt Instrument [Line Items]
Fixed interest rate (percent)		11.50%
Debt period payment, interest only period		35 months
Proceeds from debt financing		$ 40,000,000
Term loan | Pharmakon Term Loan | Prepayment Penalty, 31-48 Months
Debt Instrument [Line Items]
Debt prepayment penalty percentage (percent)		2.00%
Term loan | Pharmakon Term Loan | Prepayment Penalty, 49-60 Months
Debt Instrument [Line Items]
Debt prepayment penalty percentage (percent)		1.00%
Term loan | Solar Term Loan
Debt Instrument [Line Items]
Aggregate principal amount	$ 40,000,000
Unamortized debt discount and issuance cost	$ 800,000
Fixed interest rate (percent)	9.40%
Debt maturity term (in months)	60 months
Debt period payment, interest only period	36 months
Allowable prepayment increments per agreement	$ 10,000,000
Prepayment premium in year one (percent)	3.00%
Prepayment premium in year two (percent)	1.25%
Prepayment premium in year three or later (percent)	0.50%
Effective interest rate during the period (percent)			10.60%	11.80%	10.60%	12.00%
Final fee	$ 1,000,000
Final fee as percentage of aggregate principal amount (percent)	2.50%
Incremental interest rate increase upon default of minimum liquidity covenant (percent)	5.00%
Term loan | Solar Term Loan | Basis spread option
Debt Instrument [Line Items]
Basis spread on variable rate	0.33%
Term loan | Solar Term Loan | Net product revenue less than $75 million
Debt Instrument [Line Items]
Debt covenant minimum cash balance	$ 15,000,000
Term loan | Solar Term Loan | Net product revenue less than $75 million | Maximum
Debt Instrument [Line Items]
Product revenue threshold for minimum liquidity covenant	75,000,000
Term loan | Solar Term Loan | Net product revenue more than $75 million and less than $100 million
Debt Instrument [Line Items]
Debt covenant minimum cash balance	7,500,000
Term loan | Solar Term Loan | Net product revenue more than $75 million and less than $100 million | Maximum
Debt Instrument [Line Items]
Product revenue threshold for minimum liquidity covenant	100,000,000
Term loan | Solar Term Loan | Net product revenue more than $75 million and less than $100 million | Minimum
Debt Instrument [Line Items]
Product revenue threshold for minimum liquidity covenant	75,000,000
Term loan | Solar Term Loan | Net product revenue more than $100 million
Debt Instrument [Line Items]
Debt covenant minimum cash balance	0
Term loan | Solar Term Loan | Net product revenue more than $100 million | Minimum
Debt Instrument [Line Items]
Product revenue threshold for minimum liquidity covenant	$ 100,000,000

Borrowings - Debt Maturity (Det

Borrowings - Debt Maturity (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Future principal and final fee payments
2021 (remaining six months)	$ 0
2022	0
2023	11,667
2024	20,000
2025	9,333
Total principal and final fee payments	$ 41,000	$ 41,000

Stock-Based Incentive Compens_3

Stock-Based Incentive Compensation Plans - Narrative (Details) $ in Thousands	3 Months Ended			4 Months Ended	6 Months Ended		8 Months Ended
	Jun. 30, 2021USD ($)shares	Mar. 31, 2021	Jun. 30, 2020USD ($)shares	Apr. 30, 2020	Jun. 30, 2021USD ($)shares	Jun. 30, 2020USD ($)shares	Dec. 31, 2020USD ($)purchase_periodshares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, stock options	$ 2,100				$ 2,100
Stock options granted (in shares) | shares			0		0
Early exercise of stock options, share subject to repurchase (in shares) | shares	1,945				1,945		5,836
Issuance of common stock related to employee stock purchase plan	$ 1,566		$ 991
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, expected period for recognition (in years)					1 year 4 months 24 days
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost, expected period for recognition (in years)					3 years 1 month 6 days
Unrecognized compensation cost	37,400				$ 37,400
2018 ESPP
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock as a percent of fair market value (percent)		85.00%
Employee stock purchase program offering period interval (in months)				6 months			12 months
Number of purchase periods in offering interval | purchase_period							2
Issuance of common stock related to employee stock purchase plan (in shares) | shares					104,861	74,685
Issuance of common stock related to employee stock purchase plan					$ 1,600	$ 1,000
Accrued compensation and related expenses for employee payroll deductions	$ 300				$ 300		$ 400

Stock-Based Incentive Compens_4

Stock-Based Incentive Compensation Plans - Stock Option Activity (Details)	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Number of Shares
Outstanding, beginning of period (in shares) | shares	2,405,957
Exercised (in shares) | shares	(234,892)
Canceled and forfeited (in shares) | shares	(23,170)
Outstanding, end of period (in shares) | shares	2,147,895
Weighted-Average Exercise Price
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 8.54
Exercised (in dollars per share) | $ / shares	5.33
Canceled and forfeited (in dollars per share) | $ / shares	16.02
Outstanding, end of period (in dollars per share) | $ / shares	$ 8.81

Stock-Based Incentive Compens_5

Stock-Based Incentive Compensation Plans - Valuation Assumptions for Stock Options (Details)	6 Months Ended
	Jun. 30, 2020$ / shares
Black-Scholes option-pricing model assumptions
Weighted average grant date fair value per share (in dollars per share)	$ 8.37
Stock Options
Black-Scholes option-pricing model assumptions
Expected volatility, minimum (percent)	46.70%
Expected volatility, maximum (percent)	47.20%
Risk-free interest rate, minimum (percent)	1.56%
Risk-free interest rate, maximum (percent)	1.64%
Dividend yield (percent)	0.00%
Stock Options | Minimum
Black-Scholes option-pricing model assumptions
Expected term (years)	5 years 6 months
Stock Options | Maximum
Black-Scholes option-pricing model assumptions
Expected term (years)	7 years

Stock-Based Incentive Compens_6

Stock-Based Incentive Compensation Plans - Restricted Stock Units Activity (Details) - Restricted Stock Units	6 Months Ended
	Jun. 30, 2021$ / sharesshares
Number of Shares
Outstanding, beginning of period (in shares) | shares	1,165,295
Granted (in shares) | shares	1,000,129
Vested (in shares) | shares	(313,297)
Canceled and forfeited (in shares) | shares	(132,763)
Outstanding, end of period (in shares) | shares	1,719,364
Weighted Average Grant Date Fair Value
Outstanding, beginning of period (in dollars per share) | $ / shares	$ 20.07
Granted (in dollars per share) | $ / shares	29.72
Vested (in dollars per share) | $ / shares	20.14
Canceled and forfeited (in dollars per share) | $ / shares	25.51
Outstanding, end of period (in dollars per share) | $ / shares	$ 25.25

Stock-Based Incentive Compens_7

Stock-Based Incentive Compensation Plans - Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 4,257	$ 2,955	$ 8,287	$ 5,577
Cost of goods sold
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	129	85	303	156
Sales and marketing
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	2,125	1,347	4,024	2,488
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	404	288	823	528
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 1,599	$ 1,235	$ 3,137	$ 2,405

Net Loss Per Share of Common _3

Net Loss Per Share of Common Stock - Computation of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Earnings Per Share [Abstract]
Net loss	$ (13,981)	$ (12,242)	$ (12,472)	$ (12,772)	$ (26,223)	$ (25,244)
Weighted-average number of common shares used to compute diluted net loss per share (in shares)	32,978,914		28,492,582		32,836,040	27,872,505
Weighted-average number of common shares used to compute basic net loss per share (in shares)	32,978,914		28,492,582		32,836,040	27,872,505
Net loss per share, basic (in usd per share)	$ (0.42)		$ (0.44)		$ (0.80)	$ (0.91)
Net loss per share, diluted (in usd per share)	$ (0.42)		$ (0.44)		$ (0.80)	$ (0.91)

Net Loss Per Share of Common _4

Net Loss Per Share of Common Stock - Antidilutive Common Stock Equivalents Excluded from Computation of Earnings Per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	4,021,396	4,238,304	4,021,396	4,238,304
Stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	2,147,895	2,652,683	2,147,895	2,652,683
Restricted stock units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	1,719,364	1,333,501	1,719,364	1,333,501
Shares subject to repurchase
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	1,945	9,732	1,945	9,732
ESPP purchase rights
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	34,070	124,266	34,070	124,266
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Common stock equivalents excluded from computation of diluted net loss per share	118,122	118,122	118,122	118,122

Related Party Transaction (Deta

Related Party Transaction (Details) - SeaSpine - Joint development agreement - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Related Party Transaction [Line Items]
Reimbursement charges expensed	$ 13,854	$ 10,000	$ 23,854	$ 44,000
Outstanding liability to SeaSpine	$ 0		$ 0		$ 0
Term of product royalty sales period (in years)			10 years