Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Revenue, net	$ 8,463	$ 6,926	$ 22,380	$ 19,504
Cost of goods sold	4,264	3,749	11,418	10,338
Gross margin	4,199	3,177	10,962	9,166
Operating expense:
Research and development	1,619	1,763	5,155	5,687
Selling, general and administrative	14,724	12,025	44,882	34,718
Total operating expense	16,343	13,788	50,037	40,405
Operating loss	(12,144)	(10,611)	(39,075)	(31,239)
Other income (expense), net:
Interest expense, net	(1,050)	(926)	(2,869)	(2,804)
Other income (expense), net	(50)	6	(3)	(22)
Total other income (expense), net	(1,100)	(920)	(2,872)	(2,826)
Loss before income taxes	(13,244)	(11,531)	(41,947)	(34,065)
Provision for income taxes	0	0	0	0
Net loss	(13,244)	(11,531)	(41,947)	(34,065)
Preferred stock dividend	(557)	(550)	(1,657)	(1,650)
Net loss attributable to common stockholders	$ (13,801)	$ (12,081)	$ (43,604)	$ (35,715)
Net loss per share of common shares outstanding - basic and diluted (usd per share)	$ (1.91)	$ (9.74)	$ (7.35)	$ (42.43)
Weighted average common shares outstanding - basic and diluted (in shares)	7,215,654	1,240,192	5,934,072	841,837