K2M 10-Q 6 May 15 2015 Q1 Quarterly report Financial data

DOCUMENT_AND_ENTITY_INFORMATIO

DOCUMENT AND ENTITY INFORMATION DOCUMENT AND ENTITY INFORMATION	3 Months Ended
	Mar. 31, 2015	Apr. 20, 2015
Entity [Abstract]
Entity Registrant Name	K2M Group Holdings, Inc.
Entity Central Index Key	1499807
Current Fiscal Year End Date	-19
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Amendment Flag	FALSE
Entity Common Stock, Shares Outstanding		39,655,132

CONDENSED_CONSOLIDATED_BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$39,020	$11,411
Accounts receivable, net	35,074	33,937
Inventory, net	53,179	52,617
Deferred income taxes	2,821	3,437
Prepaid expenses and other current assets	4,917	3,911
Total current assets	135,011	105,313
Property and equipment, net	4,397	4,220
Goodwill and intangible assets, net	160,822	163,423
Other assets, net	28,789	29,672
Total assets	329,019	302,628
Current liabilities:
Accounts payable	17,690	14,018
Accrued expenses	10,052	10,077
Accrued payroll liabilities	7,998	11,488
Total current liabilities	35,740	35,583
Deferred income taxes	7,863	8,479
Other liabilities	870	112
Total liabilities	44,473	44,174
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.001 par value, 750,000,000 shares authorized; 39,605,130 and 37,366,098 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	40	37
Additional paid-in capital	424,523	386,795
Accumulated other comprehensive income	4,473	1,827
Accumulated deficit	-144,490	-130,205
Total stockholders’ equity	284,546	258,454
Total liabilities and stockholders’ equity	$329,019	$302,628

CONSOLIDATED_BALANCE_SHEETS_Un

CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Common stock, par value per share (in usd per share)	$0.00	$0.00
Common stock, shares authorized (in shares)	750,000,000	750,000,000
Common stock, shares issued (in shares)	39,605,130	37,366,098
Common stock, shares outstanding (in shares)	39,605,130	37,366,098

CONDENSED_CONSOLIDATED_STATEME

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Income Statement [Abstract]
Revenue	$50,424	$42,251
Cost of revenue	17,497	14,414
Gross profit	32,927	27,837
Operating expenses:
Research, development and engineering	4,633	3,197
Sales and marketing	25,010	22,448
General and administrative	13,329	15,890
Total operating expenses	42,972	41,535
Loss from operations	-10,045	-13,698
Other income (expense):
Foreign currency transaction (loss) gain	-4,137	222
Interest expense	-80	-1,247
Total other expense, net	-4,217	-1,025
Loss before income tax expense	-14,262	-14,723
Income tax expense	23	24
Net loss	-14,285	-14,747
Accretion and adjustment of preferred stock to fair value		-1,180
Accretion and adjustment of preferred stock to fair value	0
Net loss attributable to stockholders	($14,285)	($15,927)
Net loss per share attributable to common stockholders:
Basic and diluted (in dollars per share)	($0.37)	($0.71)
Weighted average shares outstanding:
Basic and diluted (in shares)	38,739,798	22,523,358

CONDENSED_CONSOLIDATED_STATEME1

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net loss	($14,285)	($14,747)
Other comprehensive income (loss):
Foreign currency translation adjustment	2,646	-86
Other comprehensive income (loss)	2,646	-86
Comprehensive loss	($11,639)	($14,833)

CONDENSED_CONSOLIDATED_STATEME2

CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS’ EQUITY (Unaudited) (USD $)	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	IPO [Member]	IPO [Member]	IPO [Member]
In Thousands, except Share data, unless otherwise specified							Common Stock [Member]	Additional Paid-in Capital [Member]
Beginning Balance at Dec. 31, 2014	$258,454	$37	$386,795	$1,827	($130,205)
Beginning Balance (in shares) at Dec. 31, 2014	37,366,098	37,366,098
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss	-14,285				-14,285
Other comprehensive income	2,646			2,646
Stock-based compensation	1,901		1,901
Issuances of common stock (in shares)							2,044,990
Issuances of common stock						35,448	2	35,446
Exercise of options (in shares)	278,704	194,042
Exercise of options	382	1	381
Ending Balance at Mar. 31, 2015	$284,546	$40	$424,523	$4,473	($144,490)
Ending Balance (in shares) at Mar. 31, 2015	39,605,130	39,605,130

CONDENSED_CONSOLIDATED_STATEME3

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating activities
Net loss	($14,285)	($14,747)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	6,036	9,705
Provision for allowance for doubtful accounts	41	137
Provision for inventory reserve	1,239	721
Stock-based compensation	1,901	375
Amortization of issuance and discount costs included in interest expense	0	67
Deferred income taxes	21	0
Changes in operating assets and liabilities:
Accounts receivable	-1,345	-508
Inventory	-1,536	-6,075
Prepaid expenses and other assets	-2,745	-4,305
Accounts payable, accrued expenses, and accrued payroll liabilities	3,655	5,447
Net cash used in operating activities	-7,018	-9,183
Investing activities
Purchase of surgical instruments	-1,430	-2,058
Purchase of property and equipment	-649	-658
Purchase of intangible assets	-17	-18
Net cash used in investing activities	-2,096	-2,734
Financing activities
Proceeds from issuance of notes to stockholders	0	14,634
Proceeds from issuances of common stock, net of issuance costs	36,455	1,939
Issuances and exercise of stock-based compensation benefit plans, net of income tax	382	-942
Net cash provided by financing activities	36,837	15,631
Effect of exchange rate changes on cash and cash equivalents	-114	13
Net increase in cash and cash equivalents	27,609	3,727
Cash and cash equivalents at beginning of period	11,411	7,419
Cash and cash equivalents at end of period	39,020	11,146
Significant noncash financing activities
Deferred offering costs	1,007	2,291
Cash paid for:
Income taxes	52	0
Interest	24	255
Series A Redeemable Convertible Preferred Stock [Member]
Significant noncash financing activities
Accretion of redeemable convertible preferred stock	0	1,195
Series B Redeemable Convertible Preferred Stock [Member]
Significant noncash financing activities
Accretion of redeemable convertible preferred stock	$0	($15)

GENERAL_AND_SUMMARY_OF_SIGNIFI

GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES
	K2M Group Holdings, Inc. (the Company) was formed as a Delaware corporation on June 29, 2010. On July 2, 2010, K2M, Inc. (K2M), a company initially incorporated in 2004, entered into an Agreement and Plan of Merger (the Merger Agreement) with Altitude Group Holdings, Inc. (Altitude) and Altitude Merger Sub, Inc. (Merger Sub). Altitude was a newly formed corporation and an indirect wholly-owned subsidiary of Welsh, Carson, Anderson & Stowe XI, L.P. On August 12, 2010 (the Merger Date), upon the closing of the transactions under the Merger Agreement, Merger Sub merged with and into K2M with K2M being the surviving corporation of such merger (the Merger) and Altitude was renamed K2M Group Holdings, Inc.
	The Company is a global medical device company focused on designing, developing and commercializing innovative and proprietary complex spine technologies and techniques. The Company’s complex spine products are used by spine surgeons to treat some of the most difficult and challenging spinal pathologies, such as deformity (primarily scoliosis), trauma, and tumor. The Company has applied its product development expertise in innovating complex spine technologies and techniques to the design, development, and commercialization of an expanding number of proprietary minimally invasive surgery, or MIS products. The Company’s MIS products are designed to allow for less invasive access to the spine and faster patient recovery times as compared to traditional open access surgical approaches for both complex spine and degenerative spine pathologies. The Company has also leveraged these core competencies in the design, development and commercialization of an increasing number of products for patients suffering from degenerative spinal conditions.
	Issuance of Common Stock
	On February 2, 2015, the Company completed a second public offering of 6,044,990 shares of its common stock at a price of $18.75 per share.  The Company sold 2,044,990 shares of common stock in the offering and selling stockholders sold 4,000,000 shares of common stock in the offering. The Company received net proceeds from the offering of approximately $35,400 after deducting the underwriting discount and offering expenses.
	The proceeds of the primary portion of the offering will be used by the Company for working capital and general corporate purposes which is expected to include the expansion of the Company's global distribution network and the purchase of inventory to support sales efforts. Use of proceeds may also include the acquisition of or investment in complementary products, technologies or businesses. The principal purposes of the secondary offering were to facilitate an orderly distribution of shares by the selling stockholders and to increase the public float of the Company's shares. The Company did not receive any proceeds from shares of common stock sold by the selling stockholders.
	In connection with the offering, certain of the selling stockholders granted the underwriters an option to purchase from them additional shares of common stock at the public offering price, less underwriting discounts.  On February 12, 2015, the underwriters exercised this option and purchased 906,748 shares of common stock from the selling stockholders at a price of $18.75 per share before underwriting discounts.  The Company received no proceeds from the sale of these shares.
	Unaudited Interim Results
	The accompanying condensed consolidated balance sheets as of March 31, 2015 and December 31, 2014, the condensed consolidated statements of operations, the condensed consolidated statements of comprehensive income (loss) for the three months ended March 31, 2015 and 2014, the condensed consolidated statements of changes in stockholders’ equity as of March 31, 2015, and the condensed consolidated statements of cash flows for the three months ended March 31, 2015 and 2014 are unaudited. The unaudited interim financial statements have been prepared on the same basis of accounting as the annual financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company’s financial position and results of operations and cash flows for the periods presented. The results for the three months ended March 31, 2015 are not necessarily indicative of future results. All information as of March 31, 2015 and for the three month periods ending March 31, 2015 and 2014 within these notes to the consolidated financial statements is unaudited.
	Principles of Consolidation
	The accompanying consolidated financial statements include the accounts of the Company and all of its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
	Use of Estimates
	The preparation of financial statements in conformity with generally accepted accounting principles in the United States (US GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
	Net Loss per Share
	Basic net loss per common share is determined by dividing the net loss allocable to common stockholders by the weighted average number of common shares outstanding during the periods presented, without consideration of common stock equivalents. Diluted loss per share is computed by dividing the net loss allocable to common stockholders by the weighted average number of shares of common stock and common stock equivalents outstanding for the period. The treasury stock method is used to determine the dilutive effect of the Company’s stock option grants and the if-converted method is used to determine the dilutive effect of the Company’s Series A redeemable convertible preferred stock or Series A Preferred and Series B redeemable convertible preferred stock or Series B Preferred, until their conversion into common stock in May 2014. The weighted average shares used to calculate both basic and diluted loss per share are the same because common stock equivalents were excluded in the calculation of diluted loss per share because their effect would be anti-dilutive.
	Foreign Currency Translation and Other Comprehensive Loss
	The account balances of foreign subsidiaries are translated into U.S. dollars using exchange rates for assets and liabilities at the balance sheet date and average prevailing exchange rates for the period for revenue and expense accounts. Adjustments resulting from translation are included in other comprehensive income (loss), which is the Company’s only component of accumulated other comprehensive loss.
	Remeasurement gains and losses from foreign currency transactions are included in the consolidated statements of operations in the period in which they occur.
	Recent Accounting Pronouncements
	The Company qualifies as an “emerging growth company” (EGC) pursuant to the provisions of the JOBS Act and has elected to take advantage of the extended transition period provided in Section 7(a)(2)(B) of the Securities Act which permits EGCs to defer compliance with new or revised accounting standards (the EGC extension) until non-issuers are required to comply with such standards. Accordingly, so long as the Company continues to qualify as an EGC, it will not have to adopt or comply with new accounting standards until non-issuers are required to comply with such standards.
	In May 2014, the FASB amended the existing accounting standards for revenue recognition. The amendments are based on the principle that revenue should be recognized to depict the transfer of goods and services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. For public entities, other than EGCs that have elected the EGC extension, the guidance will be effective for annual reporting periods beginning after December 15, 2016. EGCs that have elected the EGC extension, including the Company, and non-public entities will be required to comply with the guidance for annual reporting periods beginning after December 15, 2017. Early adoption is not permitted. The amendments may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of the initial application. In April 2015, the FASB proposed a one-year deferral of the effective date for its revenue recognition standard which would defer the aforementioned implementation dates by one year. The Company is evaluating the impact of these amendments and the transition alternatives on its consolidated financial statements.
	In April 2015, the FASB issued guidance to simplify the presentation of debt issuance costs by requiring them to be presented as a deduction from the corresponding debt liability, rather than reported as an asset. This will make the presentation of debt issuance costs consistent with the presentation of debt discounts and premiums. This new guidance affects only the presentation of debt issuance costs, not recognition and measurement. For public entities other than EGCs that have elected the EGC extension, the guidance will be effective for annual reporting periods beginning after December 15, 2015, and interim periods within those fiscal years. For all other entities, EGCs that have elected the EGC extension, including the Company, and non-public entities will be required to comply with the guidance on a retrospective basis for fiscal years beginning after December 15, 2015, and interim periods within the fiscal years beginning after December 15, 2016. Although adoption of this new guidance may impact how such items are classified on the Company’s balance sheet, the Company does not anticipate that its adoption of this guidance will have a material impact on its financial position, results of operations or cash flows. There will be no changes in the presentations of the Company’s other consolidated financial statements.
	In April 2015, the FASB issued guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract.  For public entities, other than EGC’s that have elected the EGC extension, the guidance is effective for annual reporting periods, including interim periods within those annual reporting periods, beginning after December 15, 2015. For all other entities, including the Company, it is effective for annual reporting periods beginning after December 15, 2015 and interim periods in annual reporting periods beginning after December 15, 2016. Early adoption is permitted for all entities. The Company is evaluating the impact of this guidance on its consolidated financial statements.

ACCOUNTS_RECEIVABLE

ACCOUNTS RECEIVABLE	3 Months Ended
	Mar. 31, 2015
Receivables [Abstract]
ACCOUNTS RECEIVABLE	ACCOUNTS RECEIVABLE
	The following table summarizes the Company's accounts receivables, net of allowances:
		March 31,			December 31,
		2015			2014
	Accounts receivable	$	37,573		$	36,431
	Allowances	(2,499		)	(2,494		)
	Accounts receivable, net	$	35,074		$	33,937

INVENTORY

INVENTORY	3 Months Ended
	Mar. 31, 2015
Inventory Disclosure [Abstract]
INVENTORY	INVENTORY
	The following table summarizes the Company's inventory, net of allowance:
		March 31,			December 31,
		2015			2014
	Finished goods	$	80,500		$	78,331
	Inventory allowances	(27,321		)	(25,714		)
	Inventory, net	$	53,179		$	52,617
	Inventory includes surgical instruments available for sale with a carrying value of $8,545 and $8,491 at March 31, 2015 and
	December 31, 2014, respectively.

GOODWILL_AND_INTANGIBLE_ASSETS

GOODWILL AND INTANGIBLE ASSETS	3 Months Ended
	Mar. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS	GOODWILL AND INTANGIBLE ASSETS
	Goodwill and intangible assets comprise the following:
		As of March 31, 2015
		Estimated		Gross		Accumulated			Net
		Useful Lives				Amortization
	Goodwill	—		$	121,814	$	—		$	121,814
	Indefinite-lived intangible assets:
	Trademarks	—		12,900		—			12,900
	In-process research and development	—		900		—			900
	Other	—		278		—			278
	Subtotal			14,078		—			14,078
	Subject to amortization
	Developed technology	4 - 6 years		62,000		(47,906		)	14,094
	Licensed technology	4 - 6 years		52,600		(52,213		)	387
	Customer relationships	4 - 7 years		29,700		(19,623		)	10,077
	Patents and other	2 - 17 years		1,432		(1,060		)	372
	Subtotal			145,732		(120,802		)	24,930
	Total			$	281,624	$	(120,802	)	$	160,822
		As of December 31, 2014
		Estimated		Gross		Accumulated			Net
		Useful Lives				Amortization
	Goodwill	—		$	121,814	$	—		$	121,814
	Indefinite-lived intangible assets:
	Trademarks	—		12,900		—			12,900
	In-process research and development	—		900		—			900
	Other	—		278		—			278
	Subtotal			14,078		—			14,078
	Subject to amortization
	Developed technology	4 - 6 years		62,000		(46,460		)	15,540
	Licensed technology	4 - 6 years		52,600		(52,175		)	425
	Customer relationships	4 - 7 years		29,700		(18,563		)	11,137
	Patents and other	2 - 17 years		1,414		(985		)	429
	Subtotal			145,714		(118,183		)	27,531
	Total			$	281,606	$	(118,183	)	$	163,423
	Amortization expense was $2,622 and $7,551 for the three months ended March 31, 2015 and 2014, respectively.
	As of March 31, 2015, the expected amortization expense for the remainder of 2015 and the following four years and thereafter is as follows:
		31-Mar-15
	2015	$	7,657
	2016	10,209
	2017	6,595
	2018	100
	2019 and thereafter	369
	Total	$	24,930

OTHER_ASSETS

OTHER ASSETS	3 Months Ended
	Mar. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
OTHER ASSETS	OTHER ASSETS
	Other assets comprises the following:
		March 31,		December 31,
		2015		2014
	Surgical instruments, net	$	20,684	$	21,392
	Restricted cash	7,959		8,114
	Other	146		166
	Total	$	28,789	$	29,672
	Surgical instruments are stated net of accumulated amortization of $20,374 and $18,610 at March 31, 2015 and December 31, 2014, respectively. Amortization expense was $2,155 and $1,308 for the three months ended March 31, 2015 and 2014, respectively.
	As of March 31, 2015 and December 31, 2014, restricted cash includes amounts placed in escrow for tenant improvement costs of approximately $6,700 for the Company's new corporate headquarters. Restricted cash also includes deposits made on pending bids or contracts with customers of $1,290 and $1,447 as of March 31, 2015 and December 31, 2014, respectively.

ACCRUED_EXPENSES

ACCRUED EXPENSES	3 Months Ended
	Mar. 31, 2015
Payables and Accruals [Abstract]
ACCRUED EXPENSES	ACCRUED EXPENSES
	Accrued expenses consist of the following:
		March 31,		December 31,
		2015		2014
	Accrued commissions	$	4,315	$	4,942
	Accrued royalties	2,123		2,464
	Other	3,614		2,671
	Total	$	10,052	$	10,077

STOCKBASED_COMPENSATION

STOCK-BASED COMPENSATION	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION
	As of March 31, 2015, the Company has four stock-based compensation plans: The 2014 Employee Omnibus Incentive Plan (Omnibus Incentive Plan), the 2014 Employee Stock Purchase Plan (ESPP), the 2010 Equity Award Plan and the 2010 Independent Agent Plan, collectively, “the Plans”. The purpose of the Plans are to provide incentives to employees, directors, agents and advisors of the Company. The Plans are administered by the Company’s board of directors or its delegates. The number, type of equity incentive, exercise or share purchase price, and vesting terms are determined in accordance with the Plans, as applicable.
	As of March 31, 2015, there were a total of 1,264,523 shares of common stock available for future grants under the plans.
	The Company recognized the following stock-based compensation expense related to employees and non-employees:
			Three Months Ended March 31,
			2015			2014
	Cost of revenue		$	181		$	7
	Research, development, and engineering		149			21
	Sales and marketing		756			197
	General and administrative		815			150
			$	1,901		$	375
	Employees		$	1,827		$	269
	Non-employees		74			106
	Total		$	1,901		$	375
	A summary of stock option plans activity during the three months ended March 31, 2015 is as follows:
			Shares		Weighted-			Weighted-	Aggregate
					Average			Average	Intrinsic
					Exercise			Remaining	Value (1)
					Price			Contractual
								Term
								(years)
	Outstanding at December 31, 2014		4,277,229		$	9.55		5.83	$	48,418
	Granted		32,921		18.89
	Exercised		(278,704	)	7.11
	Expired		—		—
	Forfeited		(8,240	)	11.54
	Outstanding at March 31, 2015(2)		4,023,206		$	9.79		5.81	$	49,243
	Vested or expected to vest:
	At March 31, 2015(3)		3,806,103		$	9.71		5.72	$	46,985
	Vested:
	At March 31, 2015		2,046,172		$	8.09		4.25	$	28,582
	-1	Calculated using the estimated per-share fair market value of the Company's common stock on March 31, 2015 and December 31, 2014, which was $22.05, and $20.87, respectively.
	-2	The total includes 993,472 performance-based options at March 31, 2015.
	-3	Outstanding options, net of forfeiture rate.
	The Company recognized stock-based compensation expense of $537 and $375 for the three months ended March 31, 2015 and 2014, respectively related to the stock options.
	As of December 31, 2014 and March 31, 2015 there were 765,023 unvested restricted stock units (RSUs) outstanding. No RSUs were granted or vested during the three months ended March 31, 2015. The Company recognized stock-based compensation expense of $1,297 and $0 for the three months ended March 31, 2015 and 2014, respectively. The unrecognized compensation expense related to the unvested RSUs was $6,910 at March 31, 2015 and is expected to be recognized over a period of 1.4 years.

COMMITMENTS_AND_CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	3 Months Ended
	Mar. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES
	On December 11, 2014, the Company entered into a Deed of Lease (the “Lease Agreement”) with TC Oaklawn Owner, LLC (the “Landlord”) with respect to the Company’s new corporate headquarters to be located in two adjacent buildings in Leesburg, Virginia (the “Buildings”). On March 13, 2015 the Company received $790 of cash grant incentives from several government originators, which were included in cash and cash equivalents at March 31, 2015. There are no restrictions on the use of the cash proceeds. Pursuant to the grant agreements, the Company or the Landlord are required to make certain investments in the Buildings and the Company is required to increase its workforce in Leesburg by 96 by December 31, 2017. As a result of these commitments, the Company has recorded a long-term liability on its balance sheet of $790 until such conditions are met.
	Intellectual Property
	In the normal course of business, the Company enters into agreements to obtain the rights to certain intellectual property. These agreements may require an up-front payment, milestone payments and/or royalties. Typically, the Company has certain rights to cancel these agreements, with notice, without additional payments due other than the amount due at the time of cancellation. As of March 31, 2015, the aggregate amount of these future payments, assuming achievement of applicable milestones and non-cancellation, was $1,613 over a period not less than five years. Royalties ranging from 2% to 10% of net sales may be due on the sales of related products. Some of the agreements contain minimum annual royalty amounts.
	In November 2011, the Company entered into an agreement to purchase certain proprietary technology which could require it to make additional aggregate payments of up to $13,350 should certain milestones be met, including milestones related to regulatory applications and approvals. Cumulative payments under this agreement totaled $100 through March 31, 2015. In addition, milestone payments of $500, $2,000 and $4,000 are due upon the achievement of net sales of related products of $10,000, $25,000 and $50,000, respectively. A royalty payment of 7% of net sales of related products may be due until such sales reaches $20,000. The product related to this agreement has not yet been commercialized.
	The medical device industry is characterized by frequent claims and litigation, including claims regarding patent and other
	intellectual property rights, as well as, improper hiring practices. The Company is not aware of any pending or threatened legal proceeding against it that the Company expects would have a material adverse effect on its business, operating results or financial condition. However, the Company is a party in multiple legal actions involving claimants seeking various remedies, including monetary damages, and none of the outcomes are certain or entirely within the Company's control.

RELATED_PARTIES

RELATED PARTIES	3 Months Ended
	Mar. 31, 2015
Related Party Transactions [Abstract]
RELATED PARTIES	RELATED PARTIES
	In connection with the Merger, the Company and K2M entered into a management agreement with the major stockholder of the Company. Fees paid for such agreement totaled $0 and $263 for the three months ended March 31, 2015 and 2014, respectively. The Company records such costs in general and administrative expense in its condensed consolidated statements of operations. The management agreement was terminated in May 2014 following the Company's IPO.
	In connection with the second public offering completed on February 2, 2015, certain stockholders of the Company granted the underwriters an option to purchase from such selling shareholders additional shares of common stock at the public offering price, less underwriting discounts. On February 12, 2015, the underwriters exercised this option and purchased 906,748 shares of common stock from selling shareholders at a price of $18.75 per share before underwriting discounts. The Company received no proceeds from the sale of these shares.

INCOME_TAXES

INCOME TAXES	3 Months Ended
	Mar. 31, 2015
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES
	The provision for income taxes for the three months ended March 31, 2015 and 2014 includes both domestic and foreign income taxes at applicable statutory rates adjusted for permanent differences and valuation allowances. For the three months ended March 31, 2015 and 2014, the income tax expense was $23 and $24, resulting in an effective tax rate of (0.2)% in each period. The effective tax rate differs from the statutory rate due to permanent differences, an increase to the valuation allowance and foreign tax rate differentials.

NET_LOSS_PER_SHARE

NET LOSS PER SHARE	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
NET LOSS PER SHARE	NET LOSS PER SHARE
	The following table sets forth the computation of basic and diluted loss per share attributable to the Company’s common stockholders:
		Three Months Ended March 31,
		2015				2014
	Net loss per common share:
	Net loss	$	(14,285	)		$	(14,747	)
	Less: accretion and adjustment of Series A Preferred and Series B Preferred	—				(1,180		)
	Net loss attributable to common stockholders	$	(14,285	)		$	(15,927	)
	Basic and diluted loss per common share
	Basic and diluted weighted average common shares outstanding	38,739,798				22,523,358
	Basic and diluted loss per common share	$	(0.37	)		$	(0.71	)
	Diluted loss per share for the three months ended March 31, 2015 and 2014 does not reflect the following weighted average potential common shares, as the effect would be antidilutive:
		Three Months Ended March 31,
		2015			2014
	Series A Preferred and Series B Preferred	—			5,577,016
	Stock options	4,023,206			3,919,000
	Restricted stock units	765,023			576,132

SEGMENT_AND_GEOGRAPHICAL_CONCE

SEGMENT AND GEOGRAPHICAL CONCENTRATION	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
SEGMENT AND GEOGRAPHICAL CONCENTRATION	SEGMENT AND GEOGRAPHICAL CONCENTRATION
	Operating segments are defined as components of an enterprise for which separate discrete financial information is available and evaluated regularly by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance. The Company globally manages the business within one reporting segment. Segment information is consistent with how management reviews the business, makes investing and resource allocation decisions and assesses operating performance. Products are sold principally in the United States. International revenue represented 30.3%
	of total revenue for the three months ended March 31, 2015; however, revenue earned in any individual foreign country is below 10% of the Company’s consolidated revenue.
	The following table represents total revenue by geographic area, based on the location of the customer:
		Three Months Ended March 31,
		2015		2014
	United States	$	35,162	$	29,765
	International	15,262		12,486
	Total	$	50,424	$	42,251
	The Company classifies sales within the United States into three categories: complex spine pathologies, minimally invasive procedures and degenerative and other conditions. A significant portion of the Company’s international revenue is derived from the Company’s distributor partners who do not report their product usage at the surgeon or hospital level, which prevents us from providing a specific breakdown for our international revenue among our three product categories. These sales transactions are settled when the Company ships the product to the agent.
	To further align its procedure categorizations, beginning in the second quarter of 2014, the Company began to report MIS sales attributable to complex spine procedures, which were historically reported in the minimally invasive category, within the complex spine category. Accordingly, the complex spine category presented below includes MIS sales attributable to complex spine procedures of $1,746 for the three months ended March 31, 2014 which was historically reported in the minimally invasive category.
	The following table represents domestic revenue by procedure category:
		Three Months Ended March 31,
		2015		2014
	Complex spine	$	14,221	$	11,930
	Minimally invasive	5,809		4,739
	Degenerative	15,132		13,096
		35,162		29,765
	International	15,262		12,486
	Total	$	50,424	$	42,251

GENERAL_AND_SUMMARY_OF_SIGNIFI1

GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - (Policies)	3 Months Ended
	Mar. 31, 2015
Accounting Policies [Abstract]
Principles of Consolidation	Principles of Consolidation
	The accompanying consolidated financial statements include the accounts of the Company and all of its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates
	The preparation of financial statements in conformity with generally accepted accounting principles in the United States (US GAAP) requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Net Loss per Share	Net Loss per Share
	Basic net loss per common share is determined by dividing the net loss allocable to common stockholders by the weighted average number of common shares outstanding during the periods presented, without consideration of common stock equivalents. Diluted loss per share is computed by dividing the net loss allocable to common stockholders by the weighted average number of shares of common stock and common stock equivalents outstanding for the period. The treasury stock method is used to determine the dilutive effect of the Company’s stock option grants and the if-converted method is used to determine the dilutive effect of the Company’s Series A redeemable convertible preferred stock or Series A Preferred and Series B redeemable convertible preferred stock or Series B Preferred, until their conversion into common stock in May 2014. The weighted average shares used to calculate both basic and diluted loss per share are the same because common stock equivalents were excluded in the calculation of diluted loss per share because their effect would be anti-dilutive.
Foreign Currency Translation and Other Comprehensive Loss	Foreign Currency Translation and Other Comprehensive Loss
	The account balances of foreign subsidiaries are translated into U.S. dollars using exchange rates for assets and liabilities at the balance sheet date and average prevailing exchange rates for the period for revenue and expense accounts. Adjustments resulting from translation are included in other comprehensive income (loss), which is the Company’s only component of accumulated other comprehensive loss.
	Remeasurement gains and losses from foreign currency transactions are included in the consolidated statements of operations in the period in which they occur.
Recent Accounting Pronouncements	Recent Accounting Pronouncements
	The Company qualifies as an “emerging growth company” (EGC) pursuant to the provisions of the JOBS Act and has elected to take advantage of the extended transition period provided in Section 7(a)(2)(B) of the Securities Act which permits EGCs to defer compliance with new or revised accounting standards (the EGC extension) until non-issuers are required to comply with such standards. Accordingly, so long as the Company continues to qualify as an EGC, it will not have to adopt or comply with new accounting standards until non-issuers are required to comply with such standards.
	In May 2014, the FASB amended the existing accounting standards for revenue recognition. The amendments are based on the principle that revenue should be recognized to depict the transfer of goods and services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods and services. For public entities, other than EGCs that have elected the EGC extension, the guidance will be effective for annual reporting periods beginning after December 15, 2016. EGCs that have elected the EGC extension, including the Company, and non-public entities will be required to comply with the guidance for annual reporting periods beginning after December 15, 2017. Early adoption is not permitted. The amendments may be applied retrospectively to each prior period presented or retrospectively with the cumulative effect recognized as of the date of the initial application. In April 2015, the FASB proposed a one-year deferral of the effective date for its revenue recognition standard which would defer the aforementioned implementation dates by one year. The Company is evaluating the impact of these amendments and the transition alternatives on its consolidated financial statements.
	In April 2015, the FASB issued guidance to simplify the presentation of debt issuance costs by requiring them to be presented as a deduction from the corresponding debt liability, rather than reported as an asset. This will make the presentation of debt issuance costs consistent with the presentation of debt discounts and premiums. This new guidance affects only the presentation of debt issuance costs, not recognition and measurement. For public entities other than EGCs that have elected the EGC extension, the guidance will be effective for annual reporting periods beginning after December 15, 2015, and interim periods within those fiscal years. For all other entities, EGCs that have elected the EGC extension, including the Company, and non-public entities will be required to comply with the guidance on a retrospective basis for fiscal years beginning after December 15, 2015, and interim periods within the fiscal years beginning after December 15, 2016. Although adoption of this new guidance may impact how such items are classified on the Company’s balance sheet, the Company does not anticipate that its adoption of this guidance will have a material impact on its financial position, results of operations or cash flows. There will be no changes in the presentations of the Company’s other consolidated financial statements.
	In April 2015, the FASB issued guidance to customers about whether a cloud computing arrangement includes a software license. If a cloud computing arrangement includes a software license, then the customer should account for the software license element of the arrangement consistent with the acquisition of other software licenses. If a cloud computing arrangement does not include a software license, the customer should account for the arrangement as a service contract.  For public entities, other than EGC’s that have elected the EGC extension, the guidance is effective for annual reporting periods, including interim periods within those annual reporting periods, beginning after December 15, 2015. For all other entities, including the Company, it is effective for annual reporting periods beginning after December 15, 2015 and interim periods in annual reporting periods beginning after December 15, 2016. Early adoption is permitted for all entities. The Company is evaluating the impact of this guidance on its consolidated financial statements.

ACCOUNTS_RECEIVABLE_Tables

ACCOUNTS RECEIVABLE - (Tables)	3 Months Ended
	Mar. 31, 2015
Receivables [Abstract]
Schedule of Accounts Receivable	The following table summarizes the Company's accounts receivables, net of allowances:
		March 31,			December 31,
		2015			2014
	Accounts receivable	$	37,573		$	36,431
	Allowances	(2,499		)	(2,494		)
	Accounts receivable, net	$	35,074		$	33,937

INVENTORY_Tables

INVENTORY - (Tables)	3 Months Ended
	Mar. 31, 2015
Inventory Disclosure [Abstract]
Schedule of Current Inventory	The following table summarizes the Company's inventory, net of allowance:
		March 31,			December 31,
		2015			2014
	Finished goods	$	80,500		$	78,331
	Inventory allowances	(27,321		)	(25,714		)
	Inventory, net	$	53,179		$	52,617

GOODWILL_AND_INTANGIBLE_ASSETS1

GOODWILL AND INTANGIBLE ASSETS - (Tables)	3 Months Ended
	Mar. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Intangible Assets and Goodwill	Goodwill and intangible assets comprise the following:
		As of March 31, 2015
		Estimated		Gross		Accumulated			Net
		Useful Lives				Amortization
	Goodwill	—		$	121,814	$	—		$	121,814
	Indefinite-lived intangible assets:
	Trademarks	—		12,900		—			12,900
	In-process research and development	—		900		—			900
	Other	—		278		—			278
	Subtotal			14,078		—			14,078
	Subject to amortization
	Developed technology	4 - 6 years		62,000		(47,906		)	14,094
	Licensed technology	4 - 6 years		52,600		(52,213		)	387
	Customer relationships	4 - 7 years		29,700		(19,623		)	10,077
	Patents and other	2 - 17 years		1,432		(1,060		)	372
	Subtotal			145,732		(120,802		)	24,930
	Total			$	281,624	$	(120,802	)	$	160,822
		As of December 31, 2014
		Estimated		Gross		Accumulated			Net
		Useful Lives				Amortization
	Goodwill	—		$	121,814	$	—		$	121,814
	Indefinite-lived intangible assets:
	Trademarks	—		12,900		—			12,900
	In-process research and development	—		900		—			900
	Other	—		278		—			278
	Subtotal			14,078		—			14,078
	Subject to amortization
	Developed technology	4 - 6 years		62,000		(46,460		)	15,540
	Licensed technology	4 - 6 years		52,600		(52,175		)	425
	Customer relationships	4 - 7 years		29,700		(18,563		)	11,137
	Patents and other	2 - 17 years		1,414		(985		)	429
	Subtotal			145,714		(118,183		)	27,531
	Total			$	281,606	$	(118,183	)	$	163,423
Schedule of Expected Amortization Expense	As of March 31, 2015, the expected amortization expense for the remainder of 2015 and the following four years and thereafter is as follows:
		31-Mar-15
	2015	$	7,657
	2016	10,209
	2017	6,595
	2018	100
	2019 and thereafter	369
	Total	$	24,930

OTHER_ASSETS_Tables

OTHER ASSETS - (Tables)	3 Months Ended
	Mar. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Other Assets	Other assets comprises the following:
		March 31,		December 31,
		2015		2014
	Surgical instruments, net	$	20,684	$	21,392
	Restricted cash	7,959		8,114
	Other	146		166
	Total	$	28,789	$	29,672

ACCRUED_EXPENSES_Tables

ACCRUED EXPENSES - (Tables)	3 Months Ended
	Mar. 31, 2015
Payables and Accruals [Abstract]
Schedule of Accrued Expenses	Accrued expenses consist of the following:
		March 31,		December 31,
		2015		2014
	Accrued commissions	$	4,315	$	4,942
	Accrued royalties	2,123		2,464
	Other	3,614		2,671
	Total	$	10,052	$	10,077

STOCKBASED_COMPENSATION_Tables

STOCK-BASED COMPENSATION - (Tables)	3 Months Ended
	Mar. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of stock-based compensation expense	The Company recognized the following stock-based compensation expense related to employees and non-employees:
			Three Months Ended March 31,
			2015			2014
	Cost of revenue		$	181		$	7
	Research, development, and engineering		149			21
	Sales and marketing		756			197
	General and administrative		815			150
			$	1,901		$	375
	Employees		$	1,827		$	269
	Non-employees		74			106
	Total		$	1,901		$	375
Schedule of employee stock option plan activity	A summary of stock option plans activity during the three months ended March 31, 2015 is as follows:
			Shares		Weighted-			Weighted-	Aggregate
					Average			Average	Intrinsic
					Exercise			Remaining	Value (1)
					Price			Contractual
								Term
								(years)
	Outstanding at December 31, 2014		4,277,229		$	9.55		5.83	$	48,418
	Granted		32,921		18.89
	Exercised		(278,704	)	7.11
	Expired		—		—
	Forfeited		(8,240	)	11.54
	Outstanding at March 31, 2015(2)		4,023,206		$	9.79		5.81	$	49,243
	Vested or expected to vest:
	At March 31, 2015(3)		3,806,103		$	9.71		5.72	$	46,985
	Vested:
	At March 31, 2015		2,046,172		$	8.09		4.25	$	28,582
	-1	Calculated using the estimated per-share fair market value of the Company's common stock on March 31, 2015 and December 31, 2014, which was $22.05, and $20.87, respectively.
	-2	The total includes 993,472 performance-based options at March 31, 2015.
	-3	Outstanding options, net of forfeiture rate.

NET_LOSS_PER_SHARE_Tables

NET LOSS PER SHARE - (Tables)	3 Months Ended
	Mar. 31, 2015
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Earnings Per Share	The following table sets forth the computation of basic and diluted loss per share attributable to the Company’s common stockholders:
		Three Months Ended March 31,
		2015				2014
	Net loss per common share:
	Net loss	$	(14,285	)		$	(14,747	)
	Less: accretion and adjustment of Series A Preferred and Series B Preferred	—				(1,180		)
	Net loss attributable to common stockholders	$	(14,285	)		$	(15,927	)
	Basic and diluted loss per common share
	Basic and diluted weighted average common shares outstanding	38,739,798				22,523,358
	Basic and diluted loss per common share	$	(0.37	)		$	(0.71	)
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	Diluted loss per share for the three months ended March 31, 2015 and 2014 does not reflect the following weighted average potential common shares, as the effect would be antidilutive:
		Three Months Ended March 31,
		2015			2014
	Series A Preferred and Series B Preferred	—			5,577,016
	Stock options	4,023,206			3,919,000
	Restricted stock units	765,023			576,132

SEGMENT_AND_GEOGRAPHICAL_CONCE1

SEGMENT AND GEOGRAPHICAL CONCENTRATION - (Tables)	3 Months Ended
	Mar. 31, 2015
Segment Reporting [Abstract]
Schedule of Revenue by Geographic Area	The following table represents total revenue by geographic area, based on the location of the customer:
		Three Months Ended March 31,
		2015		2014
	United States	$	35,162	$	29,765
	International	15,262		12,486
	Total	$	50,424	$	42,251
Schedule of Revenue by Products	The following table represents domestic revenue by procedure category:
		Three Months Ended March 31,
		2015		2014
	Complex spine	$	14,221	$	11,930
	Minimally invasive	5,809		4,739
	Degenerative	15,132		13,096
		35,162		29,765
	International	15,262		12,486
	Total	$	50,424	$	42,251

GENERAL_AND_SUMMARY_OF_SIGNIFI2

GENERAL AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - (Details) (USD $)	0 Months Ended	3 Months Ended		0 Months Ended
In Thousands, except Share data, unless otherwise specified	Feb. 02, 2015	Mar. 31, 2015	Mar. 31, 2014	Feb. 12, 2015
Significant Accounting Policies [Line Items]
Stock Issued During Period, Shares, Shares Held by Company and Shareholders (in share)	6,044,990
Share Price (in usd per share)	$18.75
Stock issued during the period (in shares)	2,044,990
Stock Issued During Period, Shares, Shares Held by Shareholders (in shares)	4,000,000
Proceeds from Issuance of Common Stock	$35,400	$36,455	$1,939
Underwriters [Member]
Significant Accounting Policies [Line Items]
Share Price (in usd per share)				$18.75
Stock Issued During Period, Shares, Issued for Services (in shares)				906,748

ACCOUNTS_RECEIVABLE_Details

ACCOUNTS RECEIVABLE - (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Receivables [Abstract]
Accounts receivable	$37,573	$36,431
Allowances	-2,499	-2,494
Accounts receivable, net	$35,074	$33,937

INVENTORY_Details

INVENTORY - (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Inventory [Line Items]
Finished goods	$80,500	$78,331
Inventory allowances	-27,321	-25,714
Inventory, net	53,179	52,617
Surgical and Medical Instruments [Member]
Inventory [Line Items]
Inventory, net	$8,545	$8,491

GOODWILL_AND_INTANGIBLE_ASSETS2

GOODWILL AND INTANGIBLE ASSETS - (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Schedule of Intangible Asset by Major Class [Line Items]
Goodwill	$121,814		$121,814
Indefinite-lived intangible assets	14,078		14,078
Subject to amortization, Gross	145,732		145,714
Accumulated Amortization	-120,802		-118,183
Total	24,930		27,531
Intangible Assets, Gross	281,624		281,606
Intangible Assets, Net	160,822		163,423
Amortization expense	2,622	7,551
Developed Technology Rights [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Subject to amortization, Gross	62,000		62,000
Accumulated Amortization	-47,906		-46,460
Total	14,094		15,540
Licensed technology [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Subject to amortization, Gross	52,600		52,600
Accumulated Amortization	-52,213		-52,175
Total	387		425
Customer Relationships [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Subject to amortization, Gross	29,700		29,700
Accumulated Amortization	-19,623		-18,563
Total	10,077		11,137
Patents and Other [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Subject to amortization, Gross	1,432		1,414
Accumulated Amortization	-1,060		-985
Total	372		429
Trademarks [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Indefinite-lived intangible assets	12,900		12,900
In-process research and development [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Indefinite-lived intangible assets	900		900
Other [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Indefinite-lived intangible assets	$278		$278
Minimum [Member] | Developed Technology Rights [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Estimated Useful Lives	4 years	4 years
Minimum [Member] | Licensed technology [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Estimated Useful Lives	4 years	4 years
Minimum [Member] | Customer Relationships [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Estimated Useful Lives	4 years	4 years
Minimum [Member] | Patents and Other [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Estimated Useful Lives	2 years	2 years
Maximum [Member] | Developed Technology Rights [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Estimated Useful Lives	6 years	6 years
Maximum [Member] | Licensed technology [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Estimated Useful Lives	6 years	6 years
Maximum [Member] | Customer Relationships [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Estimated Useful Lives	7 years	7 years
Maximum [Member] | Patents and Other [Member]
Schedule of Intangible Asset by Major Class [Line Items]
Estimated Useful Lives	17 years	17 years

GOODWILL_AND_INTANGIBLE_ASSETS3

GOODWILL AND INTANGIBLE ASSETS Schedule of Expected Amortization Expense (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Goodwill and Intangible Assets Disclosure [Abstract]
2015	$7,657
2016	10,209
2017	6,595
2018	100
2019 and thereafter	369
Total	$24,930	$27,531

OTHER_ASSETS_Details

OTHER ASSETS - (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Restricted Cash and Cash Equivalents Items [Line Items]
Surgical instruments, net	$20,684		$21,392
Deposits Assets, Noncurrent	7,959		8,114
Other	146		166
Total	28,789		29,672
Surgical instruments accumulated amortization	20,374		18,610
Amortization expense	2,155	1,308
Escrow Deposits [Member] | Other Assets [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted Cash and Cash Equivalents	6,700
Demand Deposits [Member] | Other Assets [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted Cash and Cash Equivalents	$1,290		$1,447

ACCRUED_EXPENSES_Details

ACCRUED EXPENSES - (Details) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Payables and Accruals [Abstract]
Accrued commissions	$4,315	$4,942
Accrued royalties	2,123	2,464
Other	3,614	2,671
Total	$10,052	$10,077

STOCKBASED_COMPENSATION_Alloca

STOCK-BASED COMPENSATION - Allocation of Share-based Compensation (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	$1,901,000	$375,000
Cost of Revenue [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	181,000	7,000
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	149,000	21,000
Selling and Marketing Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	756,000	197,000
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	815,000	150,000
Employee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	1,827,000	269,000
Nonemployee [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	$74,000	$106,000

STOCKBASED_COMPENSATION_Summar

STOCK-BASED COMPENSATION - Summary of Stock Option Activity (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015		Mar. 31, 2014	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding Beginning Balance, Shares	4,277,229
Granted, Shares	32,921
Exercised, Shares	-278,704
Expired, Shares	0
Forfeited, Shares	-8,240
Outstanding Ending Balance, Shares	4,023,206	[1]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning, Weighted-Average Exercise Price (in usd per share)	$9.55
Granted, Weighted-Average Exercise Price (in usd per share)	$18.89
Exercised, Weighted-Average Exercise Price (in usd per share)	$7.11
Expired, Weighted-Average Exercise Price (in usd per share)	$0
Forfeited, Weighted-Average Exercise Price (in usd per share)	$11.54
Ending, Weighted-Average Exercise Price (in usd per share)	$9.79
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Outstanding, Weighted- Average Remaining Contractual Term (years)	5 years 9 months 22 days		5 years 9 months 29 days
Outstanding, Weighted- Average Remaining Contractual Term (years)	5 years 9 months 22 days		5 years 9 months 29 days
Outstanding, Aggregate Intrinsic Value	$48,418	[2]
Outstanding, Aggregate Intrinsic Value	49,243	[2]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest [Abstract]
Vested or expected to vest, shares	3,806,103	[3]
Vested or expected to vest, Weighted-Average Exercise Price (in usd per share)	$9.71
Vested or expected to vest, Weighted-Average Remaining Contractual Term	5 years 8 months 19 days
Vested or expected to vest, Aggregate Intrinsic Value	46,985	[2]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested [Abstract]
Vested, shares	2,046,172
Vested, Weighted-Average Exercise Price (in usd per share)	$8.09
Vested, Weighted-Average Remaining Contractual Term	4 years 3 months
Vested, Aggregate Intrinsic Value	$28,582	[2]
Fair value valuation, estimated fair market value of stock (in dollars per share)	$22.05			$20.87
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding Ending Balance, Shares	993,472
[1]	The total includes 993,472 performance-based options at March 31, 2015.
[2]	Calculated using the estimated per-share fair market value of the Company's common stock on March 31, 2015 and December 31, 2014, which was $22.05, and $20.87, respectively.
[3]	Outstanding options, net of forfeiture rate.

STOCKBASED_COMPENSATION_Narrat

STOCK-BASED COMPENSATION - Narrative (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
	plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Stock Plans	4
Employee Stock Purchase Plans, Shares Reserved for Future Issuance (in shares)	1,264,523
Allocated stock-based compensation expense	$1,901,000	$375,000
Employee Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated stock-based compensation expense	537,000	375,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number (in shares)	765,023
Allocated stock-based compensation expense	1,297,000	0
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized	$6,910,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition	1 year 4 months 24 days

COMMITMENTS_AND_CONTINGENCIES_

COMMITMENTS AND CONTINGENCIES - (Details) (USD $)	3 Months Ended		1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Nov. 30, 2011
	Position
Long-term Purchase Commitment [Line Items]
Revenue from Grants	$790,000
Grant, Terms and Conditions, Required Increase in Workforce by Specified Date	96
Unearned Grants	790,000
Initial payment to acquire proprietary technology	17,000	18,000
Licensed technology [Member]
Long-term Purchase Commitment [Line Items]
Other Commitment	1,613,000
Minimum contractual term	5 years
Licensed technology [Member] | Minimum [Member]
Long-term Purchase Commitment [Line Items]
Future maximum royalty payments	2.00%
Licensed technology [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Future maximum royalty payments	10.00%
In Process Research and Development [Member]
Long-term Purchase Commitment [Line Items]
Future maximum royalty payments			7.00%
Initial payment to acquire proprietary technology	100,000
Milestone payment one			500,000
Milestone payment two			2,000,000
Milestone payment three			4,000,000
Milestone for milestone payment one			10,000,000
Milestone for milestone payment two			25,000,000
Milestone for milestone payment three			50,000,000
Milestone for ending royalty payments, cumulative sales			20,000,000
In Process Research and Development [Member] | Maximum [Member]
Long-term Purchase Commitment [Line Items]
Other Commitment			$13,350,000

RELATED_PARTIES_Details

RELATED PARTIES - (Details) (USD $)	3 Months Ended		0 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Feb. 12, 2015	Feb. 02, 2015
Related Party Transaction [Line Items]
Stock Issued During Period, Value, Issued for Services (in usd per share)				$18.75
Major Stockholder [Member] | Related Party Transaction, Management Service Fee [Member]
Related Party Transaction [Line Items]
General and administrative	$0	$263
Underwriters [Member]
Related Party Transaction [Line Items]
Stock Issued During Period, Shares, Issued for Services (in shares)			906,748
Stock Issued During Period, Value, Issued for Services (in usd per share)			$18.75

INCOME_TAXES_Details

INCOME TAXES - (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Income Tax Disclosure [Abstract]
Income tax (benefit) expense	$23	$24
Effective income tax rate, percent	-0.20%

NET_LOSS_PER_SHARE_Details

NET LOSS PER SHARE - (Details) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Earnings Per Share [Abstract]
Net loss	($14,285)	($14,747)
Less: accretion and adjustment of Series A Preferred and Series B Preferred	0
Less: accretion and adjustment of Series A Preferred and Series B Preferred		-1,180
Net loss attributable to stockholders	($14,285)	($15,927)
Basic and diluted weighted average common shares outstanding	38,739,798	22,523,358
Basic and diluted loss per common share (in dollars per share)	($0.37)	($0.71)

NET_LOSS_PER_SHARE_Antidilutiv

NET LOSS PER SHARE - Antidilutive Shares (Details)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Series A and B Convertible Preferred Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Earnings Per Share (in shares)	0	5,577,016
Stock options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Earnings Per Share (in shares)	4,023,206	3,919,000
Restricted Stock Units (RSUs) [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Earnings Per Share (in shares)	765,023	576,132

SEGMENT_AND_GEOGRAPHICAL_CONCE2

SEGMENT AND GEOGRAPHICAL CONCENTRATION - Narrative (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
	Segment
Segment Reporting Information [Line Items]
Number of reportable segments	1
Revenue	$50,424	$42,251
International [Member]
Segment Reporting Information [Line Items]
Revenue	15,262	12,486
United States [Member]
Segment Reporting Information [Line Items]
Revenue	35,162	29,765
Sales Revenue, Net [Member]
Segment Reporting Information [Line Items]
Revenue	50,424	42,251
Sales Revenue, Net [Member] | International [Member]
Segment Reporting Information [Line Items]
Revenue	15,262	12,486
Sales Revenue, Net [Member] | United States [Member]
Segment Reporting Information [Line Items]
Revenue	35,162	29,765
Sales Revenue, Net [Member] | Geographic Concentration Risk [Member] | International [Member]
Segment Reporting Information [Line Items]
International revenue as a percentage of total revenue	30.30%
Sales Revenue, Net [Member] | Geographic Concentration Risk [Member] | United States [Member]
Segment Reporting Information [Line Items]
International revenue as a percentage of total revenue	10.00%
Complex Spine Attributable to Minimally Invasive Surgery [Member] | United States [Member]
Segment Reporting Information [Line Items]
Revenue		$1,746

SEGMENT_AND_GEOGRAPHICAL_CONCE3

SEGMENT AND GEOGRAPHICAL CONCENTRATION - Revenues by Geographic Area (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Segment Reporting Information [Line Items]
Revenue	$50,424	$42,251
Sales Revenue, Net [Member]
Segment Reporting Information [Line Items]
Revenue	50,424	42,251
United States [Member]
Segment Reporting Information [Line Items]
Revenue	35,162	29,765
United States [Member] | Sales Revenue, Net [Member]
Segment Reporting Information [Line Items]
Revenue	35,162	29,765
International [Member]
Segment Reporting Information [Line Items]
Revenue	15,262	12,486
International [Member] | Sales Revenue, Net [Member]
Segment Reporting Information [Line Items]
Revenue	$15,262	$12,486

SEGMENT_AND_GEOGRAPHICAL_CONCE4

SEGMENT AND GEOGRAPHICAL CONCENTRATION - Revenues by Product (Details) (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Revenue from External Customer [Line Items]
Revenue	$50,424	$42,251
United States [Member]
Revenue from External Customer [Line Items]
Revenue	35,162	29,765
United States [Member] | Complex Spine [Member]
Revenue from External Customer [Line Items]
Revenue	14,221	11,930
United States [Member] | Minimally Invasive [Member]
Revenue from External Customer [Line Items]
Revenue	5,809	4,739
United States [Member] | Degenerative [Member]
Revenue from External Customer [Line Items]
Revenue	15,132	13,096
International [Member]
Revenue from External Customer [Line Items]
Revenue	$15,262	$12,486