Goodwill and Other Intangible Assets

The changes in the net carrying amount of goodwill for the years ended December 31, are as follows:



	2018			2017
Balance as of January 1,	$	401,954		$	397,664

Goodwill resulting from business combinations	—			2,209

Foreign currency translation	(1,514		)	2,081

Balance as of December 31,	$	400,440		$	401,954

During 2017, we entered into a business combination for which we recorded $2.2 million to goodwill. Total accumulated goodwill impairment losses aggregated $107.0 million at December 31, 2018 and 2017, respectively.

Other intangible assets consist of the following:



	December 31, 2018						December 31, 2017
	Weighted Average Amortization Period (Years)	Gross Carrying Amount		Accumulated Amortization			Gross Carrying Amount		Accumulated Amortization
Intangible assets with definite lives:

Customer and distributor relationships	29	$	214,577	$	(97,131	)	$	214,685	$	(86,137	)

Sales representation, marketing and promotional rights	25	149,376		(42,000		)	149,376		(36,000		)

Patents and other intangible assets	14	61,473		(44,242		)	69,668		(42,127		)

Developed technology	16	91,965		(7,369		)	62,283		(3,352		)

Intangible assets with indefinite lives:

Trademarks and tradenames		86,544		—			86,544		—

	24	$	603,935	$	(190,742	)	$	582,556	$	(167,616	)

On January 3, 2012, the Company entered into an agreement with MTF to obtain the right to represent, market, and promote MTF's allograft tissues within the field of sports medicine. The initial consideration from the Company included a $63.0 million up-front payment for the rights and certain assets, with an additional $84.0 million contingently payable over a four year period depending on MTF meeting supply targets for tissue. On January 6, 2016, we paid the final $16.7 million additional consideration installment.

Amortization expense related to intangible assets which are subject to amortization totaled $23.2 million, $21.3 million and $20.0 million for the years ending December 31, 2018, 2017 and 2016, respectively, and is included as a reduction of revenue (for amortization related to our sales representation, marketing and promotional rights) and in selling and administrative expense (for all other intangible assets) in the consolidated statements of comprehensive income. Included in developed technology is $21.3 million of earn-out consideration that was paid during 2018 and an additional accrual of $8.4 million that is considered probable as of December 31, 2018 associated with a prior asset acquisition. The accrual is recorded in other current liabilities at December 31, 2018. This developed technology has a weighted average useful life of 15 years.

During the year ended December 31, 2018, the Company wrote off $9.5 million related to an in-process research and development asset and recorded the net charge to research and development expense. Refer to Notes 12 and 13 for further details.

The estimated amortization expense related to intangible assets at December 31, 2018 and for each of the five succeeding years is as follows:



	Amortization included in expense	Amortization recorded as a reduction of revenue	Total
2019	17,978	6,000	$	23,978
2020	17,995	6,000	$	23,995
2021	17,042	6,000	$	23,042
2022	15,583	6,000	$	21,583
2023	14,879	6,000	$	20,879