Related Party Transactions	3 Months Ended
Mar. 31, 2016
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Vertegen In April 2007, the Company entered into a license agreement with Vertegen, Inc., or Vertegen, which was amended in May 2015 (the “Vertegen Agreement”). Vertegen is an entity that is wholly owned by Dr. Lang, the Company’s Chief Executive Officer. Under the Vertegen Agreement, Vertegen granted the Company an exclusive, worldwide license under specified Vertegen patent rights and related technology to make, use and sell products and services in the fields of diagnosis and treatment of articular disorders and disorders of the human spine. The company may sublicense the rights licensed to it by Vertegen. The Company is required to use commercially reasonable efforts, at its sole expense, to prosecute the patent applications licensed to the Company by Vertegen. Pursuant to the Vertegen Agreement, the Company is required to pay Vertegen a 6% royalty on net sales of products covered by the patents licensed to the Company by Vertegen, the subject matter of which is directed primarily to spinal implants, and any proceeds from the Company enforcing the patent rights licensed to the Company by Vertegen. Such 6% royalty rate will be reduced to 3% in the United States during the five-year period following the expiration of the last-to-expire applicable patent in the United States and in the rest of the world during the five-year period following the expiration of the last-to-expire patent anywhere in the world. The Company has not sold any products subject to this agreement and has paid no royalties under this agreement. The Company has paid approximately $140,000 in expenses as of March 31, 2016 in connection with the filing and prosecution of the patent applications licensed to the Company by Vertegen. The Vertegen Agreement may be terminated by the Company at any time by providing notice to Vertegen. In addition, Vertegen may terminate the Vertegen Agreement in its entirety if the Company is in material breach of the agreement, and the Company fails to cure such breach during a specified period. Asia strategy In connection with the issuance and sale of the Company’s Series E-1 and Series E-2 preferred stock, the Company entered into a letter agreement with an investor that provides that $5.0 million of the proceeds received by the Company from the investor for the sale of the Company’s Series E-1 and Series E-2 preferred stock could only be used in connection with the marketing and sale of the Company’s products in Asia and that a committee of the Company’s board of directors should be formed for the purposes of directing and overseeing the investment of such proceeds. This letter agreement terminated upon the closing of the Company’s IPO. Upon the termination of this letter agreement, the Company was no longer required to invest such proceeds in the manner that had been required by the letter agreement and it is not required to maintain such an Asia strategy committee. While the Company is not obligated to maintain such a committee, the Company’s board of directors has determined to continue to have such a committee for a period of two years from the closing of its IPO. Based on the restriction on the use of the proceeds received in connection with the letter agreement, the proceeds were classified as restricted cash and an investment activity. Upon the closing of the Company’s IPO in July 2015, pursuant to the conditions of the letter agreement in connection with the Asia strategy, $3.5 million of the proceeds received in connection with the letter agreement were reclassified from restricted cash to cash and cash equivalents. As of March 31, 2016 and December 31, 2015, none of the proceeds were included in restricted cash. Revenue share agreement As described in Note J, the Company is a party to certain agreements with advisors to participate as a member of the Company’s scientific advisory board. In September 2011, the Company entered into an amended and restated revenue share agreement with Philipp Lang, M.D., the Company’s Chief Executive Officer, which amended and restated a similar agreement entered into in 2008 when Dr. Lang stepped down as chair of the Company’s scientific advisory board and became the Company’s Chief Executive Officer. This agreement provides that the Company will pay Dr. Lang a specified percentage of its net revenues, ranging from 0.875% to 1.33%, with respect to all of its current and planned products, including the Company’s iUni, iDuo, iTotal CR, iTotal PS and iTotal Hip products, as well as certain other knee, hip and shoulder replacement products and related instrumentation the Company may develop in the future. The specific percentage is determined by reference to product classifications set forth in the agreement and is tiered based on the level of net revenues collected by the Company on such product sales. The Company’s payment obligations expire on a product-by-product basis on the last to expire of the Company’s patents on which Dr. Lang is a named inventor that claim the applicable product. These payment obligations survive any termination of Dr. Lang’s employment with the Company. The Company incurred revenue share expense paid to Dr. Lang of $249,000 and $181,000 and for the three months ended March 31, 2016 and 2015, respectively.

Related Party Transactions

Vertegen

In April 2007, the Company entered into a license agreement with Vertegen, Inc., or Vertegen, which was amended in May 2015 (the “Vertegen Agreement”). Vertegen is an entity that is wholly owned by Dr. Lang, the Company’s Chief Executive Officer. Under the Vertegen Agreement, Vertegen granted the Company an exclusive, worldwide license under specified Vertegen patent rights and related technology to make, use and sell products and services in the fields of diagnosis and treatment of articular disorders and disorders of the human spine. The company may sublicense the rights licensed to it by Vertegen. The Company is required to use commercially reasonable efforts, at its sole expense, to prosecute the patent applications licensed to the Company by Vertegen. Pursuant to the Vertegen Agreement, the Company is required to pay Vertegen a 6% royalty on net sales of products covered by the patents licensed to the Company by Vertegen, the subject matter of which is directed primarily to spinal implants, and any proceeds from the Company enforcing the patent rights licensed to the Company by Vertegen. Such 6% royalty rate will be reduced to 3% in the United States during the five-year period following the expiration of the last-to-expire applicable patent in the United States and in the rest of the world during the five-year period following the expiration of the last-to-expire patent anywhere in the world. The Company has not sold any products subject to this agreement and has paid no royalties under this agreement. The Company has paid approximately $140,000 in expenses as of March 31, 2016 in connection with the filing and prosecution of the patent applications licensed to the Company by Vertegen. The Vertegen Agreement may be terminated by the Company at any time by providing notice to Vertegen. In addition, Vertegen may terminate the Vertegen Agreement in its entirety if the Company is in material breach of the agreement, and the Company fails to cure such breach during a specified period.

Asia strategy

In connection with the issuance and sale of the Company’s Series E-1 and Series E-2 preferred stock, the Company entered into a letter agreement with an investor that provides that $5.0 million of the proceeds received by the Company from the investor for the sale of the Company’s Series E-1 and Series E-2 preferred stock could only be used in connection with the marketing and sale of the Company’s products in Asia and that a committee of the Company’s board of directors should be formed for the purposes of directing and overseeing the investment of such proceeds. This letter agreement terminated upon the closing of the Company’s IPO. Upon the termination of this letter agreement, the Company was no longer required to invest such proceeds in the manner that had been required by the letter agreement and it is not required to maintain such an Asia strategy committee. While the Company is not obligated to maintain such a committee, the Company’s board of directors has determined to continue to have such a committee for a period of two years from the closing of its IPO. Based on the restriction on the use of the proceeds received in connection with the letter agreement, the proceeds were classified as restricted cash and an investment activity. Upon the closing of the Company’s IPO in July 2015, pursuant to the conditions of the letter agreement in connection with the Asia strategy, $3.5 million of the proceeds received in connection with the letter agreement were reclassified from restricted cash to cash and cash equivalents. As of March 31, 2016 and December 31, 2015, none of the proceeds were included in restricted cash.

Revenue share agreement

As described in Note J, the Company is a party to certain agreements with advisors to participate as a member of the Company’s scientific advisory board. In September 2011, the Company entered into an amended and restated revenue share agreement with Philipp Lang, M.D., the Company’s Chief Executive Officer, which amended and restated a similar agreement entered into in 2008 when Dr. Lang stepped down as chair of the Company’s scientific advisory board and became the Company’s Chief Executive Officer. This agreement provides that the Company will pay Dr. Lang a specified percentage of its net revenues, ranging from 0.875% to 1.33%, with respect to all of its current and planned products, including the Company’s iUni, iDuo, iTotal CR, iTotal PS and iTotal Hip products, as well as certain other knee, hip and shoulder replacement products and related instrumentation the Company may develop in the future. The specific percentage is determined by reference to product classifications set forth in the agreement and is tiered based on the level of net revenues collected by the Company on such product sales. The Company’s payment obligations expire on a product-by-product basis on the last to expire of the Company’s patents on which Dr. Lang is a named inventor that claim the applicable product. These payment obligations survive any termination of Dr. Lang’s employment with the Company. The Company incurred revenue share expense paid to Dr. Lang of $249,000 and $181,000 and for the three months ended March 31, 2016 and 2015, respectively.