Acquisition of SafeOp Surgical, Inc. - Additional Information (Details) - USD ($)			3 Months Ended			12 Months Ended
	Mar. 09, 2018	Mar. 08, 2018	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2018	Mar. 31, 2018
Business Acquisition [Line Items]
Convertible note convertible to common stock							14,300,000
Accretion to contingent consideration						$ 846,000
Minimum
Business Acquisition [Line Items]
Useful lives						1 year
Maximum
Business Acquisition [Line Items]
Useful lives						20 years
SafeOp Surgical, Inc.
Business Acquisition [Line Items]
Business acquisition date	Mar. 08, 2018
Increase in net loss due to operating expenses						$ 2,800,000
Cash paid	$ 15,100,000					15,103,000
Stock issued for acquisition, value		$ 9,800,000
Closing share price		$ 3.30
Convertible notes issued	$ 3,000,000
Convertible note convertible to common stock	987,578
Number of warrants issued	2,200,000
Exercise price of warrants per share	$ 3.50
Convertible note, maturity date	Mar. 09, 2019
Intangible assets							$ 21,600,000
Transaction costs						1,600,000
Additional shares of common stock value issuable subject to performance milestones						4,300,000
Accretion to contingent consideration						800,000
SafeOp Surgical, Inc. | Ten Days After Submission Of An Application For Regulatory Clearance
Business Acquisition [Line Items]
Stock issued for acquisition, value						1,446,000
Additional shares of common stock value issuable subject to performance milestones						1,400,000
SafeOp Surgical, Inc. | Ten Days After Receipt of Clearance from Regulatory Authority
Business Acquisition [Line Items]
Additional shares of common stock value issuable subject to performance milestones						2,900,000
SafeOp Surgical, Inc. | EPAD Tradename
Business Acquisition [Line Items]
Intangible assets						$ 60,000
SafeOp Surgical, Inc. | EPAD Tradename | Minimum
Business Acquisition [Line Items]
Useful lives						1 year
SafeOp Surgical, Inc. | Developed SSEP Technology
Business Acquisition [Line Items]
Intangible assets						$ 13,100,000
SafeOp Surgical, Inc. | Developed SSEP Technology | Maximum
Business Acquisition [Line Items]
Useful lives						20 years
SafeOp Surgical, Inc. | Common Stock
Business Acquisition [Line Items]
Number of shares of common stock agreed to issue	3,265,132
Stock issued for acquisition		2,975,209		174,302	115,621
SafeOp Surgical, Inc. | Common Stock | Subsequent Event
Business Acquisition [Line Items]
Stock issued for acquisition			886,843
SafeOp Surgical, Inc. | Common Stock | Ten Days After Submission Of An Application For Regulatory Clearance
Business Acquisition [Line Items]
Stock issued for acquisition				443,421		443,000