BUSINESS SEGMENT - Schedule of Revenue by Category (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net revenue	$ 14,568	$ 15,820	$ 15,077	$ 12,094	$ 11,681	$ 12,375	$ 11,802	$ 9,762	$ 57,559	$ 45,620	$ 37,298
Trauma and deformity
Segment Reporting Information [Line Items]
Net revenue									39,695	32,801	26,844
Scoliosis
Segment Reporting Information [Line Items]
Net revenue									16,662	11,585	9,349
Sports medicine/other
Segment Reporting Information [Line Items]
Net revenue									$ 1,202	$ 1,234	$ 1,105