CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Operating activities:
Net loss	$ (57,002)	$ (28,975)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	7,578	6,789
Stock-based compensation	10,956	5,304
Amortization of debt discount and debt issuance costs	3,709	2,087
Amortization of right-of-use asset	930
Provision for doubtful accounts	242	164
Provision for excess and obsolete inventory	8,624	3,733
Deferred income tax benefit	(438)	(1,405)
Gain on settlement		(6,168)
Beneficial conversion feature from convertible notes	242
Loss on extinguishment of debt		590
Loss on disposal of instruments	127	130
Accretion to contingent consideration	289	846
Changes in operating assets and liabilities:
Accounts receivable, net	(1,298)	(396)
Inventories, net	(14,712)	(5,014)
Prepaid expenses and other current assets	186	(268)
Other assets	262	(90)
Other long-term assets	(3,308)
Accrued expenses and other	6,647	1,677
Accounts payable	6,003	16
Deferred revenue		(261)
Lease liability	2,239
Other long-term liabilities	(4,397)	(4,367)
Net cash used in operating activities	(33,121)	(25,608)
Investing activities:
Purchases of property and equipment	(13,032)	(6,514)
Cash paid for acquisition of SafeOp Surgical, Inc.		(15,103)
Cash paid for acquisition of intangible assets		(400)
Cash received from sale of equipment		348
Net cash used in investing activities	(13,032)	(21,669)
Financing activities:
Proceeds from public offering, net	53,848
Proceeds from sale of common stock, net	1,977	51,902
Borrowings under lines of credit	114,710	90,459
Repayments under lines of credit	(112,934)	(89,993)
Principal payments on capital lease obligations	(27)	(96)
Proceeds from issuance of term debt, net	9,700	34,077
Principal payments on term loan and notes payable	3,091	32,464
Net cash provided by financing activities	64,183	53,885
Effect of exchange rate changes on cash	29	(20)
Net increase in cash	18,059	6,588
Cash at beginning of year	29,054	22,466
Cash at end of year	47,113	29,054
Supplemental disclosure of cash flow information:
Cash paid for interest	5,969	5,141
Cash paid for income taxes	161	134
Supplemental disclosure of noncash investing and financing activities:
Common stock warrants issued with term loan draw	13,664	1,708
Purchases of property and equipment in accounts payable	1,275	940
SafeOp Surgical, Inc.
Adjustments to reconcile net loss to net cash used in operating activities:
Accretion to contingent consideration	300
Supplemental disclosure of noncash investing and financing activities:
Common stock and warrants issued for the acquisition of SafeOp		12,529
Common stock issued for achievement of SafeOp contingent consideration	$ 2,889	$ 1,446