Revenue - Revenue by product and customer (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Product sales, net	$ 26,151	$ 19,011	$ 47,961	$ 37,038
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Disaggregation of Revenue [Line Items]
Product sales, net	87	(51)	50	(189)
Implants | Contracted rate | Third party distributor
Disaggregation of Revenue [Line Items]
Product sales, net	12,989	7,363	22,776	15,155
Implants | Contracted rate | Provider or Facility
Disaggregation of Revenue [Line Items]
Product sales, net	3,450	3,409	6,676	6,083
Implants | Time-and-materials Contract | Third party distributor
Disaggregation of Revenue [Line Items]
Product sales, net	3,459	2,639	6,202	3,647
Implants | Time-and-materials Contract | Time-and-materials Contract
Disaggregation of Revenue [Line Items]
Product sales, net	281	297	603	580
Biopsy kits | Direct bill
Disaggregation of Revenue [Line Items]
Product sales, net	557	468	1,099	904
Epicel | Direct bill
Disaggregation of Revenue [Line Items]
Product sales, net	$ 5,328	$ 4,886	$ 10,555	$ 10,858