Other accrued expenses and other non-current liabilities - Other accrued expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Other accrued expenses and other non-current liabilities
Accrued inventory	$ 512	$ 459
Accrued royalties	378	476
Accrued professional services	828	655
Accrued development costs	190	151
Accrued other	689	757
Total accrued expenses	$ 2,597	$ 2,498