BUSINESS COMBINATION - ApiFix Consideration (Details) - ApiFix - USD ($) $ in Thousands		12 Months Ended
	Apr. 01, 2020	Dec. 31, 2020
Business Acquisition [Line Items]
Cash consideration	$ 2,000	$ 2,000
Payment of ApiFix transaction related costs		67
Issuance of common stock	35,176	35,176
Business Combination, Contingent Consideration, Anniversary Payments, Present Value		22,620
Anniversary Payments	30,000	30,000
Business Combination, Contingent Consideration, System Sales Payment, Present Value		27,190
System sales payment	$ 41,741	41,741
Business Combination, Contingent Consideration, Present Value		87,053
Total consideration transferred		$ 108,984