Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Revenue, net	$ 7,514	$ 6,497	$ 13,917	$ 12,578
Cost of goods sold	3,796	3,405	7,154	6,589
Gross margin	3,718	3,092	6,763	5,989
Operating expense:
Research and development	1,866	1,860	3,536	3,924
Selling, general and administrative	14,907	11,228	30,158	22,693
Total operating expense	16,773	13,088	33,694	26,617
Operating loss	(13,055)	(9,996)	(26,931)	(20,628)
Other income (expense), net:
Interest expense, net	(958)	(939)	(1,819)	(1,878)
Other income (expense), net	(6)	(25)	47	(28)
Total other income (expense), net	(964)	(964)	(1,772)	(1,906)
Loss before income taxes	(14,019)	(10,960)	(28,703)	(22,534)
Provision for income taxes	0	0	0	0
Net loss	(14,019)	(10,960)	(28,703)	(22,534)
Preferred stock dividend	(550)	(550)	(1,100)	(1,100)
Net loss attributable to common stockholders	$ (14,569)	$ (11,510)	$ (29,803)	$ (23,634)
Net loss per share of common shares outstanding - basic and diluted (usd per share)	$ (2.73)	$ (12.46)	$ (5.64)	$ (36.97)
Weighted average common shares outstanding - basic and diluted (in shares)	5,333,422	923,727	5,287,659	639,358