3. Select Condensed Consolidated Balance Sheet Details

Accounts Receivable, net

Accounts receivable, net consist of the following (in thousands):

	June 30, 2018			December 31, 2017
Accounts receivable	$	11,542		$	15,328
Allowance for doubtful accounts		(137	)		(506	)
Accounts receivable, net	$	11,405		$	14,822

Inventories, net

Inventories, net consist of the following (in thousands):

	June 30, 2018			December 31, 2017
Raw materials	$	5,437		$	4,969
Work-in-process		968			502
Finished goods		37,740			37,933
		44,145			43,404
Less reserve for excess and obsolete finished goods		(15,968	)		(16,112	)
Inventories, net	$	28,177		$	27,292

Property and Equipment, net

Property and equipment, net consist of the following (in thousands except as indicated):

	Useful lives (in years)		June 30, 2018			December 31, 2017
Surgical instruments		4	$	52,288		$	53,198
Machinery and equipment		7		5,920			5,503
Computer equipment		3		3,761			3,500
Office furniture and equipment		5		2,856			2,794
Leasehold improvements	various			1,759			1,714
Construction in progress	n/a			153			336
				66,737			67,045
Less accumulated depreciation and amortization				(54,677	)		(54,375	)
Property and equipment, net			$	12,060		$	12,670

Total depreciation expense was $1.5 million and $1.6 million for the three months ended June 30, 2018 and 2017 and $3.0 million and $3.2 million for the six months ended June 30, 2018 and 2017, respectively. At both June 30, 2018 and December 31, 2017, assets recorded under capital leases of $2.1 million were included in the machinery and equipment balance. Amortization of assets under capital leases is included in depreciation expense.

Intangible Assets, net

In conjunction with the acquisition of SafeOp in March 2018, the Company recorded $21.6 million of new intangible assets. See Note 8 for further information regarding the acquisition. Intangible assets, net consist of the following (in thousands, except as indicated):

	Remaining Avg. Useful lives (in years)		June 30, 2018			December 31, 2017
Developed technology		12	$	26,975		$	13,876
Intellectual property		—		1,004			1,004
License agreements		—		5,738			5,738
Trademarks and trade names		—		792			732
Customer-related		2		7,458			7,458
Distribution network		4		4,027			4,027
In process research and development		—		8,400			—
				54,394			32,835
Less accumulated amortization				(28,012	)		(27,587	)
Intangible assets, net			$	26,382		$	5,248

Total amortization expense was $0.1 million and $0.3 million for the three months ended June 30, 2018 and 2017 and $0.4 million and $0.5 million for the six months ended June 30, 2018 and 2017, respectively.

Future amortization expense related to intangible assets as of June 30, 2018 is as follows (in thousands):

Year Ending December 31,
Remainder of 2018	$	403
2019		1,426
2020		1,411
2021		1,411
2022		1,411
Thereafter		20,320
	$	26,382

Accrued Expenses

Accrued expenses consist of the following (in thousands):

	June 30, 2018		December 31, 2017
Commissions and sales milestones	$	3,661	$	3,360
Payroll and payroll related		3,060		2,968
Litigation settlement obligation		4,400		4,400
Professional fees		3,567		1,484
Royalties		1,339		1,269
Restructuring and severance accruals		482		520
Taxes		197		246
Guaranteed collaboration compensation, current		—		4,485
Interest		349		376
Acquisition related - contingent consideration		3,300		—
Other		4,252		3,138
Total accrued expenses	$	24,607	$	22,246