on december 31 , 2019 , we divested substantially all of the assets relating to vilex 's adult product offerings to a wholly-owned subsidiary of squadron capital llc ( `` squadron `` ) in exchange for a $ 25.0 million reduction in a term note owed to squadron in connection with the initial acquisition . as part of the sale , we also executed an exclusive license arrangement with squadron providing for perpetual access to certain intellectual property and a mutual distribution agreement . on march 9 , 2020 , we purchased all the issued and outstanding membership interest of telos partners , llc ( `` telos `` ) for $ 3.3 million in total consideration . telos is a boutique regulatory consulting firm formed in colorado . on april 1 , 2020 , we purchased all the issued and outstanding membership interest of apifix , ltd. ( `` apifix `` ) for ( a ) $ 2.0 million in cash , and ( b ) 934,783 shares of the company 's common stock , $ 0.00025 par value per share , representing approximately $ 35.0 million ( based on a closing share price of $ 37.63 on april 1 , 2020. apifix , a corporation organized under the laws of israel , has developed a minimally invasive deformity correction system for patients with adolescent idiopathic scoliosis ( `` apifix system `` ) . in addition , we have also agreed to pay as part of the purchase price the following anniversary payments , subject to certain limitations and adjustments : ( i ) approximately $ 13.0 million on the second anniversary of the closing date , provided that such payment will be paid earlier if 150 clinical procedures using the apifix system are completed in the united states before such anniversary date , ( ii ) $ 8.0 million on the third anniversary of the closing date ; and ( iii ) $ 9.0 million on the fourth anniversary of the closing date . in addition , to the extent that the product of our revenues from the apifix system for the twelve months ended june 30 , 2024 multiplied by 2.25 exceeds the anniversary payments actually made for the third and fourth years , we have agreed to pay the selling shareholders a system sales payment in the amount of such excess . the anniversary payments and system sales payment may each be made in cash or cash and common stock . on june 10 , 2020 , we purchased certain intellectual property assets from band-lok , llc , a north carolina limited liability company ( `` band-lok `` ) , related to its tether clamp and implantation system ( `` tether clamp system `` ) for approximately $ 3.4 million in total consideration . we use the tether clamp system in connection with our bandloc 5.5/6.0 system . we were previously the sole licensee of the purchased assets under a license agreement with band-lok . we market and sell our products internationally in 44 countries through independent stocking distributors and sales agencies . our independent stocking distributors manage the billing relationship with each hospital in their respective territories and are responsible for servicing the product needs of their surgeon customers . in 2017 , we began to supplement our international stocking distributors with sales agencies using direct sales programs in the united kingdom , ireland , australia and new zealand where we sell directly to the hospitals . we began selling direct to canada in september 2018 , belgium and the netherlands in january 2019 , italy in march 2020 and germany , switzerland and austria in january 2021. additionally , in march 2019 , we established an operating company in the netherlands in order to enhance our operations in europe . in these markets , we work through sales agencies that are paid a commission , similar to our u.s. sales model . these arrangements have generated an increase in revenue and gross margin . for the years ended december 31 , 2020 , 2019 and 2018 , international sales accounted for approximately 11 % , 24 % and 24 % of our revenue , respectively . we believe there are significant opportunities for us to strengthen our position in u.s. and international markets by increasing investments in consigned implant and instrument sets , strengthening our global sales and distribution infrastructure and expanding our product offering . we have grown our revenue from approximately $ 10.2 million for the year ended december 31 , 2011 to $ 71.1 million for the year ended december 31 , 2020. the average annual growth rate for the company exceeded 20 % from 2009 through 2019 , partially obtained through strategic acquisitions . for the years ended december 31 , 74 2020 , 2019 and 2018 , our revenue was $ 71.1 million , $ 72.6 million and $ 57.6 million , respectively , and our net loss was $ 32.9 million , $ 13.7 million and $ 12.0 million , respectively . our net loss for the year ended december 31 , 2018 included $ 2.0 million of non-cash accelerated vesting of restricted stock compensation expense related to our october 2017 ipo . impact of covid-19 on our business a novel strain of the coronavirus disease ( `` covid-19 `` ) was first identified in wuhan , china in december 2019 , and the related outbreak was subsequently declared a pandemic by the world health organization and a national emergency by the president of the united states . as a result of the pandemic , we have experienced significant business disruption . for example , in order to meet the demand for covid-19-related hospitalizations , various governments , governmental agencies and hospital administrators required certain hospitals to postpone some elective procedures . story_separator_special_tag depreciation and amortization expenses increased $ 3.4 million , or 74 % , from $ 4.6 million for the year ended december 31 , 2019 to $ 8.0 million for the year ended december 31 , 2020. the increase was primarily due to the amortization on intangible assets acquired through the orthex , telos and apifix acquisitions and the purchase of the band-lok intellectual property and increased investments in consigned surgical instrument sets . research and development expenses research and development expenses decreased $ 0.4 million , or 8 % , from $ 5.7 million for the year ended december 31 , 2019 to $ 5.3 million for the year ended december 31 , 2020. the decrease was driven by a reduced investment in research and development project expenses as a result of the sales decline related to the covid-19 pandemic . total other expenses total other expenses increased $ 3.3 million , or 92 % , from $ 3.6 million for the year ended december 31 , 2018 to $ 6.9 million for the year ended december 31 , 2020. the increase in other expense is due to the fair value adjustment of $ 3.5 million related to the apifix contingent consideration payment . 79 comparison of the years ended december 31 , 2019 and 2018 the following table sets for the our results of operations for the years ended december 31 , 2019 and 2018 : replace_table_token_6_th revenue the following tables set forth our revenue by geography and product category for the years ended december 31 , 2019 and 2018 : replace_table_token_7_th replace_table_token_8_th revenue increased $ 15.0 million , or 26 % , from $ 57.6 million for the year ended december 31 , 2018 to $ 72.6 million for the year ended december 31 , 2019. the increase was due primarily to trauma and deformity sales growth of $ 9.7 million , or 24 % , primarily driven by sales of our pediatric nailing platform | femur , pediplate , and orthex hexapod system , and scoliosis sales growth of $ 4.8 million , or 29 % , primarily driven by sales of our response tm and other licensed products . nearly all of the increase in each of the trauma and deformity and scoliosis categories was due to the increase in unit volume sold and not a result of price changes . cost of revenue and gross margin cost of revenue was $ 17.9 million and $ 14.9 million for the years ended december 31 , 2019 and 2018 , respectively . gross margin was 75 % for the year ended december 31 , 2019 and 74 % for the year ended december 31 , 2018. the increase in gross margin was due primarily to a decrease in cost of goods sold related to the addition of sales agents in our international markets along with increase sales . sales and marketing expenses sales and marketing expenses increased $ 4.7 million , or 18 % , from $ 26.6 million for the year ended december 31 , 2018 to $ 31.3 million for the year ended december 31 , 2019. the increase was due primarily to increased sales commission expenses , driven by the increase in unit volume sold , and marketing expenses . 80 general and administrative expenses general and administrative expenses increased $ 5.7 million , or 27 % , from $ 20.9 million for the year ended december 31 , 2018 to $ 26.7 million for the year ended december 31 , 2019. the increase was due primarily to the addition of personnel and resources to support the growth of our business as well as increased quality and regulatory resources and consultants to comply with new fda and eu regulatory requirements . depreciation and amortization expenses increased $ 1.7 million , or 59 % , from $ 2.9 million for the year ended december 31 , 2018 to $ 4.6 million for the year ended december 31 , 2019. the increase was primarily due to prior increased investments in consigned surgical instrument sets and amortization on intangible licenses . we also purchased $ 13.2 million in amortizable intangibles associated with the acquisition of orthex on june 4 , 2019 , which increased amortization expense in the current year . research and development expenses research and development expenses increased $ 1.0 million , or 21 % , from $ 4.7 million for the year ended december 31 , 2018 to $ 5.7 million for the year ended december 31 , 2019. the increase was due to the addition of personnel to support our product pipeline and the growth of our business . other expenses other expenses were $ 3.6 million for each of the years ended december 31 , 2019 and 2018 , respectively . the expense in both of these periods consisted primarily of interest expense on long-term debt . liquidity and capital resources we have incurred operating losses since inception and negative cash flows from operating activities of $ 18.4 million , $ 17.8 million and $ 15.6 million for the years ended december 31 , 2020 , 2019 and 2018 , respectively . as of december 31 , 2020 , we had an accumulated deficit of $ 161.8 million . we anticipate that our losses will continue in the near term as we continue to expand our product portfolio and invest in additional consigned implant and instrument sets to support our expansion into existing and new markets . since inception , we have funded our operations primarily with proceeds from the sales of our common and preferred stock , convertible securities and debt , as well as through sales of our products . as of december 31 , 2020 we had cash , cash equivalents and restricted cash of $ 30.1 million and short-term investments of $ 55.1 million . we believe our existing cash and cash equivalents , amounts available under the loan agreement , cash receipts from sales of our

cash used in operating activities net cash used in operating activities was $ 18.4 million , $ 17.8 million and $ 15.6 million for the years ended december 31 , 2020 , 2019 and 2018 , respectively . the primary use of this cash was to fund our operations related to the development and commercialization of our products in each of these years . net cash used for working capital was $ ( 5.0 ) million , $ ( 11.4 ) million and $ ( 9.6 ) million for the years ended december 31 , 2020 , 2019 and 2018 , respectively . during 2020 , we increased inventory by $ 12.1 million as we deployed additional inventory , including $ 1.6 million due to the repurchase of inventory from a stocking distributor in germany , austria and switzerland that we converted to a sales agency , and accounts receivable increased by $ 0.5 million . these uses of cash for working capital were offset by our legal settlement accrual of $ 6.3 million and an increase in accounts payable of $ 3.1 million as we purchased inventory on account for deployment into the field . during 2019 , we increased inventory by $ 9.8 million as we deployed additional inventory and accounts receivable increased by $ 5.8 million as our sales increased . during 2018 , we increased inventory by $ 4.8 million as we deployed additional inventory following our ipo and accounts receivable increased by $ 3.8 million as our sales increased . we had a net loss of $ 32.9 million , $ 13.7 million and $ 12.0 million for the years ended december 31 , 2020 , 2019 and 2018 , respectively , which drove a difference in the use of operating cash between the periods . our net loss for the year ended december 31 , 2018 included a $ 2.0 million non-cash expense associated with the accelerated vesting of our restricted stock related to our ipo . cash used in investing activities net cash used in investing activities was $ 69.8 million , $ 61.9 million and $ 6.0 million for the years ended december 31 , 2020 , 2019 and 2018 , respectively .


 Write a concise suspicious activity report of the following text delimited by triple backquotes. Return your response as a formal report which covers the key points highlighting the location,dates,entity names and account holder information in chronological order of the text.
     ```cash used in operating activities net cash used in operating activities was $ 18.4 million , $ 17.8 million and $ 15.6 million for the years ended december 31 , 2020 , 2019 and 2018 , respectively . the primary use of this cash was to fund our operations related to the development and commercialization of our products in each of these years . net cash used for working capital was $ ( 5.0 ) million , $ ( 11.4 ) million and $ ( 9.6 ) million for the years ended december 31 , 2020 , 2019 and 2018 , respectively . during 2020 , we increased inventory by $ 12.1 million as we deployed additional inventory , including $ 1.6 million due to the repurchase of inventory from a stocking distributor in germany , austria and switzerland that we converted to a sales agency , and accounts receivable increased by $ 0.5 million . these uses of cash for working capital were offset by our legal settlement accrual of $ 6.3 million and an increase in accounts payable of $ 3.1 million as we purchased inventory on account for deployment into the field . during 2019 , we increased inventory by $ 9.8 million as we deployed additional inventory and accounts receivable increased by $ 5.8 million as our sales increased . during 2018 , we increased inventory by $ 4.8 million as we deployed additional inventory following our ipo and accounts receivable increased by $ 3.8 million as our sales increased . we had a net loss of $ 32.9 million , $ 13.7 million and $ 12.0 million for the years ended december 31 , 2020 , 2019 and 2018 , respectively , which drove a difference in the use of operating cash between the periods . our net loss for the year ended december 31 , 2018 included a $ 2.0 million non-cash expense associated with the accelerated vesting of our restricted stock related to our ipo . cash used in investing activities net cash used in investing activities was $ 69.8 million , $ 61.9 million and $ 6.0 million for the years ended december 31 , 2020 , 2019 and 2018 , respectively .
```    
 Suspicious Activity Report : on december 31 , 2019 , we divested substantially all of the assets relating to vilex 's adult product offerings to a wholly-owned subsidiary of squadron capital llc ( `` squadron `` ) in exchange for a $ 25.0 million reduction in a term note owed to squadron in connection with the initial acquisition . as part of the sale , we also executed an exclusive license arrangement with squadron providing for perpetual access to certain intellectual property and a mutual distribution agreement . on march 9 , 2020 , we purchased all the issued and outstanding membership interest of telos partners , llc ( `` telos `` ) for $ 3.3 million in total consideration . telos is a boutique regulatory consulting firm formed in colorado . on april 1 , 2020 , we purchased all the issued and outstanding membership interest of apifix , ltd. ( `` apifix `` ) for ( a ) $ 2.0 million in cash , and ( b ) 934,783 shares of the company 's common stock , $ 0.00025 par value per share , representing approximately $ 35.0 million ( based on a closing share price of $ 37.63 on april 1 , 2020. apifix , a corporation organized under the laws of israel , has developed a minimally invasive deformity correction system for patients with adolescent idiopathic scoliosis ( `` apifix system `` ) . in addition , we have also agreed to pay as part of the purchase price the following anniversary payments , subject to certain limitations and adjustments : ( i ) approximately $ 13.0 million on the second anniversary of the closing date , provided that such payment will be paid earlier if 150 clinical procedures using the apifix system are completed in the united states before such anniversary date , ( ii ) $ 8.0 million on the third anniversary of the closing date ; and ( iii ) $ 9.0 million on the fourth anniversary of the closing date . in addition , to the extent that the product of our revenues from the apifix system for the twelve months ended june 30 , 2024 multiplied by 2.25 exceeds the anniversary payments actually made for the third and fourth years , we have agreed to pay the selling shareholders a system sales payment in the amount of such excess . the anniversary payments and system sales payment may each be made in cash or cash and common stock . on june 10 , 2020 , we purchased certain intellectual property assets from band-lok , llc , a north carolina limited liability company ( `` band-lok `` ) , related to its tether clamp and implantation system ( `` tether clamp system `` ) for approximately $ 3.4 million in total consideration . we use the tether clamp system in connection with our bandloc 5.5/6.0 system . we were previously the sole licensee of the purchased assets under a license agreement with band-lok . we market and sell our products internationally in 44 countries through independent stocking distributors and sales agencies . our independent stocking distributors manage the billing relationship with each hospital in their respective territories and are responsible for servicing the product needs of their surgeon customers . in 2017 , we began to supplement our international stocking distributors with sales agencies using direct sales programs in the united kingdom , ireland , australia and new zealand where we sell directly to the hospitals . we began selling direct to canada in september 2018 , belgium and the netherlands in january 2019 , italy in march 2020 and germany , switzerland and austria in january 2021. additionally , in march 2019 , we established an operating company in the netherlands in order to enhance our operations in europe . in these markets , we work through sales agencies that are paid a commission , similar to our u.s. sales model . these arrangements have generated an increase in revenue and gross margin . for the years ended december 31 , 2020 , 2019 and 2018 , international sales accounted for approximately 11 % , 24 % and 24 % of our revenue , respectively . we believe there are significant opportunities for us to strengthen our position in u.s. and international markets by increasing investments in consigned implant and instrument sets , strengthening our global sales and distribution infrastructure and expanding our product offering . we have grown our revenue from approximately $ 10.2 million for the year ended december 31 , 2011 to $ 71.1 million for the year ended december 31 , 2020. the average annual growth rate for the company exceeded 20 % from 2009 through 2019 , partially obtained through strategic acquisitions . for the years ended december 31 , 74 2020 , 2019 and 2018 , our revenue was $ 71.1 million , $ 72.6 million and $ 57.6 million , respectively , and our net loss was $ 32.9 million , $ 13.7 million and $ 12.0 million , respectively . our net loss for the year ended december 31 , 2018 included $ 2.0 million of non-cash accelerated vesting of restricted stock compensation expense related to our october 2017 ipo . impact of covid-19 on our business a novel strain of the coronavirus disease ( `` covid-19 `` ) was first identified in wuhan , china in december 2019 , and the related outbreak was subsequently declared a pandemic by the world health organization and a national emergency by the president of the united states . as a result of the pandemic , we have experienced significant business disruption . for example , in order to meet the demand for covid-19-related hospitalizations , various governments , governmental agencies and hospital administrators required certain hospitals to postpone some elective procedures . story_separator_special_tag depreciation and amortization expenses increased $ 3.4 million , or 74 % , from $ 4.6 million for the year ended december 31 , 2019 to $ 8.0 million for the year ended december 31 , 2020. the increase was primarily due to the amortization on intangible assets acquired through the orthex , telos and apifix acquisitions and the purchase of the band-lok intellectual property and increased investments in consigned surgical instrument sets . research and development expenses research and development expenses decreased $ 0.4 million , or 8 % , from $ 5.7 million for the year ended december 31 , 2019 to $ 5.3 million for the year ended december 31 , 2020. the decrease was driven by a reduced investment in research and development project expenses as a result of the sales decline related to the covid-19 pandemic . total other expenses total other expenses increased $ 3.3 million , or 92 % , from $ 3.6 million for the year ended december 31 , 2018 to $ 6.9 million for the year ended december 31 , 2020. the increase in other expense is due to the fair value adjustment of $ 3.5 million related to the apifix contingent consideration payment . 79 comparison of the years ended december 31 , 2019 and 2018 the following table sets for the our results of operations for the years ended december 31 , 2019 and 2018 : replace_table_token_6_th revenue the following tables set forth our revenue by geography and product category for the years ended december 31 , 2019 and 2018 : replace_table_token_7_th replace_table_token_8_th revenue increased $ 15.0 million , or 26 % , from $ 57.6 million for the year ended december 31 , 2018 to $ 72.6 million for the year ended december 31 , 2019. the increase was due primarily to trauma and deformity sales growth of $ 9.7 million , or 24 % , primarily driven by sales of our pediatric nailing platform | femur , pediplate , and orthex hexapod system , and scoliosis sales growth of $ 4.8 million , or 29 % , primarily driven by sales of our response tm and other licensed products . nearly all of the increase in each of the trauma and deformity and scoliosis categories was due to the increase in unit volume sold and not a result of price changes . cost of revenue and gross margin cost of revenue was $ 17.9 million and $ 14.9 million for the years ended december 31 , 2019 and 2018 , respectively . gross margin was 75 % for the year ended december 31 , 2019 and 74 % for the year ended december 31 , 2018. the increase in gross margin was due primarily to a decrease in cost of goods sold related to the addition of sales agents in our international markets along with increase sales . sales and marketing expenses sales and marketing expenses increased $ 4.7 million , or 18 % , from $ 26.6 million for the year ended december 31 , 2018 to $ 31.3 million for the year ended december 31 , 2019. the increase was due primarily to increased sales commission expenses , driven by the increase in unit volume sold , and marketing expenses . 80 general and administrative expenses general and administrative expenses increased $ 5.7 million , or 27 % , from $ 20.9 million for the year ended december 31 , 2018 to $ 26.7 million for the year ended december 31 , 2019. the increase was due primarily to the addition of personnel and resources to support the growth of our business as well as increased quality and regulatory resources and consultants to comply with new fda and eu regulatory requirements . depreciation and amortization expenses increased $ 1.7 million , or 59 % , from $ 2.9 million for the year ended december 31 , 2018 to $ 4.6 million for the year ended december 31 , 2019. the increase was primarily due to prior increased investments in consigned surgical instrument sets and amortization on intangible licenses . we also purchased $ 13.2 million in amortizable intangibles associated with the acquisition of orthex on june 4 , 2019 , which increased amortization expense in the current year . research and development expenses research and development expenses increased $ 1.0 million , or 21 % , from $ 4.7 million for the year ended december 31 , 2018 to $ 5.7 million for the year ended december 31 , 2019. the increase was due to the addition of personnel to support our product pipeline and the growth of our business . other expenses other expenses were $ 3.6 million for each of the years ended december 31 , 2019 and 2018 , respectively . the expense in both of these periods consisted primarily of interest expense on long-term debt . liquidity and capital resources we have incurred operating losses since inception and negative cash flows from operating activities of $ 18.4 million , $ 17.8 million and $ 15.6 million for the years ended december 31 , 2020 , 2019 and 2018 , respectively . as of december 31 , 2020 , we had an accumulated deficit of $ 161.8 million . we anticipate that our losses will continue in the near term as we continue to expand our product portfolio and invest in additional consigned implant and instrument sets to support our expansion into existing and new markets . since inception , we have funded our operations primarily with proceeds from the sales of our common and preferred stock , convertible securities and debt , as well as through sales of our products . as of december 31 , 2020 we had cash , cash equivalents and restricted cash of $ 30.1 million and short-term investments of $ 55.1 million . we believe our existing cash and cash equivalents , amounts available under the loan agreement , cash receipts from sales of our

