CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (Unaudited) - USD ($) $ in Thousands	Total	SafeOp Surgical, Inc.	SafeOp Surgical, Inc. Milestone 2	Series A Convertible Preferred Stock	Series B Convertible Preferred Stock	Common Stock	Common Stock SafeOp Surgical, Inc.	Common Stock SafeOp Surgical, Inc. Milestone 2	Additional paid-in capital	Additional paid-in capital SafeOp Surgical, Inc.	Additional paid-in capital SafeOp Surgical, Inc. Milestone 2	Shareholder note receivable	Treasury stock	Accumulated other comprehensive income (loss)	Accumulated deficit
Balance at Dec. 31, 2017	$ (26,658)					$ 2			$ 436,803			$ (5,000)	$ (97)	$ 1,093	$ (459,459)
Balance, shares at Dec. 31, 2017				5,000		19,857,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	812								812
Issuance of stock for public offering, net of offering costs	42,823								42,823
Issuance of Series B preferred stock, net of offering costs, shares					45,000
Common stock issued for conversion of Series A preferred stock, shares				(1,000)		637,000
Common stock issued for vesting of restricted stock awards, net of shares repurchased for tax liability, shares						38,000
Common stock issued for warrant exercises	4,128								4,128
Common stock issued for warrant exercises, shares						2,061,000
Issuance of common stock and warrants for the acquisition of SafeOp		$ 11,468								$ 11,468
Issuance of common stock and warrants for the acquisition of SafeOp, shares							$ 2,975
Prepaid forward contract for the additional shares to be issued for the acquisition of SafeOp		938								938
Foreign currency translation adjustments	(22)													(22)
Net loss	(1,916)														(1,916)
Balance at Mar. 31, 2018	31,573					$ 2			496,972			(5,000)	(97)	1,071	(461,375)
Balance, shares at Mar. 31, 2018				4,000	45,000	25,568,000
Balance at Dec. 31, 2017	(26,658)					$ 2			436,803			(5,000)	(97)	1,093	(459,459)
Balance, shares at Dec. 31, 2017				5,000		19,857,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	(18,347)
Balance at Sep. 30, 2018	24,213					$ 4			506,078			(5,000)	(97)	1,034	(477,806)
Balance, shares at Sep. 30, 2018				4,000		43,053,000
Balance at Dec. 31, 2017	(26,658)					$ 2			436,803			(5,000)	(97)	1,093	(459,459)
Balance, shares at Dec. 31, 2017				5,000		19,857,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for acquisition of SafeOp - Milestone 2, shares							443,421
Balance at Dec. 31, 2018	17,574					$ 4			523,525			(5,000)	(97)	1,064	(501,922)
Balance, shares at Dec. 31, 2018				4,000		43,368,000
Balance at Mar. 31, 2018	31,573					$ 2			496,972			(5,000)	(97)	1,071	(461,375)
Balance, shares at Mar. 31, 2018				4,000	45,000	25,568,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,222								1,222
Conversion of Series B preferred stock	(42,823)								(42,823)
Conversion of Series B preferred stock, shares					(45,000)
Common stock issued for conversion of Series B preferred stock	42,824					$ 2			42,822
Common stock issued for conversion of Series B preferred stock, shares						14,349,000
Common stock issued for vesting of restricted stock awards, net of shares repurchased for tax liability, shares						28,000
Common stock issued for warrant exercises	4,500								4,500
Common stock issued for warrant exercises, shares						2,250,000
Issuance of common stock for acquisition of SafeOp - Milestone 2		364								364
Issuance of common stock for acquisition of SafeOp - Milestone 2, shares							115,621
Prepaid forward contract for the additional shares to be issued for the acquisition of SafeOp		(460)								(460)
Common stock issued for employee stock purchase plan and stock option exercises	260								260
Common stock issued for employee stock purchase plan and stock option exercises, shares						90,000
Series B issuance costs	(174)								(174)
Foreign currency translation adjustments	10													10
Net loss	(7,076)														(7,076)
Balance at Jun. 30, 2018	30,220					$ 4			502,683			(5,000)	(97)	1,081	(468,451)
Balance, shares at Jun. 30, 2018				4,000		42,401,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,716								1,716
Common stock issued for stock option exercises	14								14
Common stock issued for stock option exercises, shares						8,000
Common stock issued for vesting of restricted stock awards, net of shares repurchased for tax liability, shares						27,000
Issuance of common stock for acquisition of SafeOp - Milestone 2		697	$ 1,446							697	$ 1,446
Issuance of common stock for acquisition of SafeOp - Milestone 2, shares							174,302	443,000
Prepaid forward contract for the additional shares to be issued for the acquisition of SafeOp		$ (478)								$ (478)
Foreign currency translation adjustments	(47)													(47)
Net loss	(9,355)														(9,355)
Balance at Sep. 30, 2018	24,213					$ 4			506,078			(5,000)	(97)	1,034	(477,806)
Balance, shares at Sep. 30, 2018				4,000		43,053,000
Balance at Dec. 31, 2018	17,574					$ 4			523,525			(5,000)	(97)	1,064	(501,922)
Balance, shares at Dec. 31, 2018				4,000		43,368,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	1,565								1,565
Distributor equity incentives	42								42
Distributor equity incentives, shares						15,000
Common stock issued for conversion of Series A preferred stock, shares				(4,000)		1,858,000
Recognition of beneficial conversion feature -SafeOp Convertible Notes	242								242
Common stock issued for stock option exercises	14								14
Common stock issued for stock option exercises, shares						8,000
Common stock issued for vesting of restricted stock awards, net of shares repurchased for tax liability	(183)								(183)
Common stock issued for vesting of restricted stock awards, net of shares repurchased for tax liability, shares						442,000
Issuance of common stock for acquisition of SafeOp - Milestone 2			$ 2,889								$ 2,889
Issuance of common stock for acquisition of SafeOp - Milestone 2, shares							886,843	887,000
Foreign currency translation adjustments	75													75
Net loss	(12,968)														(12,968)
Balance at Mar. 31, 2019	9,250					$ 4			528,094			(5,000)	(97)	1,139	(514,890)
Balance, shares at Mar. 31, 2019						46,578,000
Balance at Dec. 31, 2018	17,574					$ 4			523,525			(5,000)	(97)	1,064	(501,922)
Balance, shares at Dec. 31, 2018				4,000		43,368,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for acquisition of SafeOp - Milestone 2, shares							886,843
Net loss	(39,971)
Balance at Sep. 30, 2019	57,654					$ 6			603,518			(5,000)	(97)	1,120	(541,893)
Balance, shares at Sep. 30, 2019						60,665,000
Balance at Mar. 31, 2019	9,250					$ 4			528,094			(5,000)	(97)	1,139	(514,890)
Balance, shares at Mar. 31, 2019						46,578,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	2,140								2,140
Distributor equity incentives	138								138
Distributor equity incentives, shares						45,000
Common stock issued for vesting of restricted stock awards, net of shares repurchased for tax liability, shares						217,000
Common stock issued for warrant exercises	723								723
Common stock issued for warrant exercises, shares						255,000
Common stock issued for employee stock purchase plan and stock option exercises	664								664
Common stock issued for employee stock purchase plan and stock option exercises, shares						278,000
Issuance of common stock warrants	13,664								13,664
Foreign currency translation adjustments	18													18
Net loss	(12,436)														(12,436)
Balance at Jun. 30, 2019	14,161					$ 4			545,423			(5,000)	(97)	1,157	(527,326)
Balance, shares at Jun. 30, 2019						47,373,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation	3,411								3,411
Distributor equity incentives	40								40
Distributor equity incentives, shares						15,000
Issuance of stock for public offering, net of offering costs	53,974					$ 2			53,972
Issuance of Series B preferred stock, net of offering costs, shares						12,535,000
Common stock issued for conversion of Series A preferred stock, shares						97,000
Common stock issued for warrant exercises	600								600
Common stock issued for warrant exercises, shares						333,000
Common stock issued for vesting of performance and restricted stock awards, net of shares repurchased for tax liability	(30)								(30)
Common stock issued for vesting of performance and restricted stock awards, net of shares repurchased for tax liability, shares						286,000
Common stock issued for employee stock purchase plan and stock option exercises	102								102
Common stock issued for employee stock purchase plan and stock option exercises, shares						26,000
Foreign currency translation adjustments	(37)													(37)
Net loss	(14,567)														(14,567)
Balance at Sep. 30, 2019	$ 57,654					$ 6			$ 603,518			$ (5,000)	$ (97)	$ 1,120	$ (541,893)
Balance, shares at Sep. 30, 2019						60,665,000