Subsequent Event	12 Months Ended
Dec. 31, 2019
Subsequent Events [Abstract]
Subsequent Event	15. Subsequent Event Tender Offer Agreement On February 28, 2020, the Company entered into a Tender Offer Agreement (the “Tender Offer Agreement”) with EOS Imaging S.A., a société anonyme organized and existing under the laws of France (“EOS”), pursuant to which the Company or one of its affiliates will commence a public tender offer to purchase all of the issued and outstanding ordinary shares, nominal value €0.01 per share (collectively, the “Shares”), and outstanding convertible bonds (“OCEANEs”), of EOS. The tender offer will consist of a cash tender offer price of €2.80 (or approximately $3.08) per Share and €7.01 (or approximately $7.71) per OCEANE, respectively (the “Cash Offer”), or at the option of EOS shareholders, 0.50 of a share of common stock, par value $0.0001 per share, of the company (“ATEC Common Stock”) per Share (the “Exchange Offer” and, together with the Cash Offer, the “Offer Consideration”). The tender offer will need to be filed with and cleared by the Autorité des marches financiers (the “AMF”), which filing is expected to occur in late April 2020, prior to the commencement of the tender offer. EOS is a leader in outcome-improving orthopedic medical imaging and software solutions that inform the entire surgical process. Commitment Letter In connection with entry into the Tender Offer Agreement, the Company entered into a commitment letter, dated February 28, 2020 (the “Commitment Letter”), with Perceptive Credit Holdings III, LP (together with its affiliates, “Perceptive”), pursuant to which, subject to the terms and conditions set forth therein, Perceptive has committed to provide $130 million in secured debt financing, up to $60 million of which (the “Refinancing Portion”) will be made available to retire the Company’s existing credit facilities with MidCap Funding IV, LLC and Squadron Medical Finance Solutions, LLC. The remaining commitment by Perceptive to provide an additional $70 million (which may be increased to up to $100 million at the request of the Company if agreed by Perceptive in its sole discretion) in secured debt financing (the “Tender Offer Portion”) will be made available to fund the Cash Offer portion of the Offer Consideration, provided the Company may elect not to incur all or a portion of such Tender Offer Portion to the extent it is unnecessary to fund such Cash Offer amount. In the event the Company elects not to incur the Tender Offer Portion of Perceptive’s commitment, Perceptive will make available up to $15 million in secured debt financing (the “Supplemental Portion”), in addition to the Refinancing Portion, to be used for the Company’s and its subsidiaries’ general corporate and working capital needs. The funding of each of the debt facilities provided for in the Commitment Letter is subject to the satisfaction of customary conditions for facilities of such type that are set forth therein, including entry into definitive documentation reflecting the terms of the Commitment Letter and no material adverse effect with respect to EOS. Under the terms of the Commitment Letter, the Company has agreed to issue certain warrants to Perceptive representing the right to acquire ATEC Common Stock in connection with the incurrence of the Refinancing Portion (the “Refinancing Warrants”), the incurrence and use of the Tender Offer Portion to consummate the tender offer (the “Tender Offer Warrants”) and the incurrence of the Supplemental Portion (the “Supplemental Warrants” and, together with the Refinancing Warrants and Tender Offer Warrants, the “Warrants”), as applicable. The price per share for 50% of the Refinancing Warrants shall be the lower of (x) the 5-day volume weighted average price of the ATEC Common Stock (“5-day VWAP”) immediately prior to the date of the Commitment Letter and (y) the 5-day VWAP immediately prior to the closing date of the Refinancing Portion, subject to a floor of $4.60 per share (the “Base Refinancing Warrant Price”). The price per share for the remaining 50% of the Refinancing Warrants shall be equal to the Base Refinancing Warrant Price plus an additional 12.5% premium. The price per share for 50% of the Tender Offer Warrants shall be the lower of (x) the 5-day VWAP immediately prior to the date of the Commitment Letter or (y) the 5-day VWAP immediately prior to the date such Tender Offer Warrants are issued, subject to a floor of $4.60 per share (the “Base Tender Offer Warrant Price”). The price per share for the remaining 50% of the Tender Offer Warrants shall be equal to the Base Tender Offer Warrant Price plus an additional 12.5% premium. The price per share for 50% of the Supplemental Warrants shall be the lower of (x) the 5-day VWAP immediately prior to the date of the Commitment Letter or (y) the 5-day VWAP immediately prior to the date the Supplemental Portion is incurred, subject to a floor of $4.60 per share (the “Base Supplemental Warrant Price”). The price per share for the remaining 50% of the Supplemental Warrants shall be equal to the Base Supplemental Warrant Price plus an additional 12.5% premium. The Refinancing Warrants, Tender Offer Warrants and Supplemental Warrants will be exercisable into a number of shares of ATEC Common Stock representing 18.5% of the aggregate principal amount borrowed in respect of the Refinancing Portion, 9% of the aggregate principal amount borrowed in respect of the Tender Offer Portion and used to consummate the Tender Offer and 9% of the aggregate principal amount borrowed in respect of the Supplemental Portion, respectively, in each case calculated using the Base Refinancing Warrant Price, Base Tender Offer Warrant Price or Base Supplemental Warrant Price, as applicable.

Subsequent Event

12 Months Ended

Dec. 31, 2019

15. Subsequent Event

Tender Offer Agreement

On February 28, 2020, the Company entered into a Tender Offer Agreement (the “Tender Offer Agreement”) with EOS Imaging S.A., a société anonyme organized and existing under the laws of France (“EOS”), pursuant to which the Company or one of its affiliates will commence a public tender offer to purchase all of the issued and outstanding ordinary shares, nominal value €0.01 per share (collectively, the “Shares”), and outstanding convertible bonds (“OCEANEs”), of EOS. The tender offer will consist of a cash tender offer price of €2.80 (or approximately $3.08) per Share and €7.01 (or approximately $7.71) per OCEANE, respectively (the “Cash Offer”), or at the option of EOS shareholders, 0.50 of a share of common stock, par value $0.0001 per share, of the company (“ATEC Common Stock”) per Share (the “Exchange Offer” and, together with the Cash Offer, the “Offer Consideration”). The tender offer will need to be filed with and cleared by the Autorité des marches financiers (the “AMF”), which filing is expected to occur in late April 2020, prior to the commencement of the tender offer. EOS is a leader in outcome-improving orthopedic medical imaging and software solutions that inform the entire surgical process.

Commitment Letter

In connection with entry into the Tender Offer Agreement, the Company entered into a commitment letter, dated February 28, 2020 (the “Commitment Letter”), with Perceptive Credit Holdings III, LP (together with its affiliates, “Perceptive”), pursuant to which, subject to the terms and conditions set forth therein, Perceptive has committed to provide $130 million in secured debt financing, up to $60 million of which (the “Refinancing Portion”) will be made available to retire the Company’s existing credit facilities with MidCap Funding IV, LLC and Squadron Medical Finance Solutions, LLC. The remaining commitment by Perceptive to provide an additional $70 million (which may be increased to up to $100 million at the request of the Company if agreed by Perceptive in its sole discretion) in secured debt financing (the “Tender Offer Portion”) will be made available to fund the Cash Offer portion of the Offer Consideration, provided the Company may elect not to incur all or a portion of such Tender Offer Portion to the extent it is unnecessary to fund such Cash Offer amount. In the event the Company elects not to incur the Tender Offer Portion of Perceptive’s commitment, Perceptive will make available up to $15 million in secured debt financing (the “Supplemental Portion”), in addition to the Refinancing Portion, to be used for the Company’s and its subsidiaries’ general corporate and working capital needs. The funding of each of the debt facilities provided for in the Commitment Letter is subject to the satisfaction of customary conditions for facilities of such type that are set forth therein, including entry into definitive documentation reflecting the terms of the Commitment Letter and no material adverse effect with respect to EOS.

Under the terms of the Commitment Letter, the Company has agreed to issue certain warrants to Perceptive representing the right to acquire ATEC Common Stock in connection with the incurrence of the Refinancing Portion (the “Refinancing Warrants”), the incurrence and use of the Tender Offer Portion to consummate the tender offer (the “Tender Offer Warrants”) and the incurrence of the Supplemental Portion (the “Supplemental Warrants” and, together with the Refinancing Warrants and Tender Offer Warrants, the “Warrants”), as applicable. The price per share for 50% of the Refinancing Warrants shall be the lower of (x) the 5-day volume weighted average price of the ATEC Common Stock (“5-day VWAP”) immediately prior to the date of the Commitment Letter and (y) the 5-day VWAP immediately prior to the closing date of the Refinancing Portion, subject to a floor of $4.60 per share (the “Base Refinancing Warrant Price”). The price per share for the remaining 50% of the Refinancing Warrants shall be equal to the Base Refinancing Warrant Price plus an additional 12.5% premium. The price per share for 50% of the Tender Offer Warrants shall be the lower of (x) the 5-day VWAP immediately prior to the date of the Commitment Letter or (y) the 5-day VWAP immediately prior to the date such Tender Offer Warrants are issued, subject to a floor of $4.60 per share (the “Base Tender Offer Warrant Price”). The price per share for the remaining 50% of the Tender Offer Warrants shall be equal to the Base Tender Offer Warrant Price plus an additional 12.5% premium. The price per share for 50% of the Supplemental Warrants shall be the lower of (x) the 5-day VWAP immediately prior to the date of the Commitment Letter or (y) the 5-day VWAP immediately prior to the date the Supplemental Portion is incurred, subject to a floor of $4.60 per share (the “Base Supplemental Warrant Price”). The price per share for the remaining 50% of the Supplemental Warrants shall be equal to the Base Supplemental Warrant Price plus an additional 12.5% premium. The Refinancing Warrants, Tender Offer Warrants and Supplemental Warrants will be exercisable into a number of shares of ATEC Common Stock representing 18.5% of the aggregate principal amount borrowed in respect of the Refinancing Portion, 9% of the aggregate principal amount borrowed in respect of the Tender Offer Portion and used to consummate the Tender Offer and 9% of the aggregate principal amount borrowed in respect of the Supplemental Portion, respectively, in each case calculated using the Base Refinancing Warrant Price, Base Tender Offer Warrant Price or Base Supplemental Warrant Price, as applicable.