Net revenue for the fourth quarter of 2020 was $106.8 million, compared to $74.6 million for the fourth quarter of 2019, an increase of $32.2 million, or 43%. The increase in net revenue was driven by a $30.2 million increase, or 48%, in net revenue of Advanced Wound Care products and a $1.9 million increase, or 17%, in net revenue of Surgical & Sports Medicine products, compared to the fourth quarter of 2019. The increase in Advanced Wound Care net revenue was primarily attributable to the expanded sales force, increased sales to existing and new customers, and increased adoption of our amniotic product portfolio, including our Affinity product. The increase in Surgical & Sports Medicine net revenue was primarily attributable to the expanded sales force and penetration of existing and new customer accounts, partially offset by postponement or cancellation of medical procedures as a result of COVID-19. Net revenue from the sale of PuraPly products for the fourth quarter of 2020 was $45.3 million, compared to $39.9 million for the fourth quarter of 2019, an increase of $5.4 million, or 13%. Net revenue from the sale of PuraPly products represented approximately 42% of net revenue in the fourth quarter of 2020, as compared to 53% of net revenue in the fourth quarter of 2019.
Gross profit for the fourth quarter of 2020 was $81.3 million, or 76% of net revenue, compared to $54.3 million, or 73% of net revenue, for the fourth quarter of 2019, an increase of $27.0 million, or 50%. The increase in gross profit resulted primarily from increased sales volume due to the strength in our Advanced Wound Care and Surgical & Sports Medicine products as well as a shift in product mix to our higher gross margin products.
Operating expenses for the fourth quarter of 2020 were $59.5 million, compared to $56.0 million for the fourth quarter of 2019, an increase of $3.5 million, or 6%. R&D expense was $6.3 million for the fourth quarter of 2020, compared to $3.6 million in the fourth quarter of 2019, an increase of $2.7 million, or 73%. The increase was primarily due to an increase in process development costs associated with a new contract manufacturer, increased headcount associated with our existing Advanced Wound Care and Surgical & Sports Medicine products, an increase in product costs associated with our pipeline products not yet commercialized, and an increase in the clinical study and related costs necessary to seek regulatory approvals for certain of our products. Selling, general and administrative expenses were $53.2 million, compared to $52.4 million in the fourth quarter of 2019, an increase of $0.8 million, or 2%. The increase in selling, general and administrative expenses was primarily due to additional headcount, primarily in our direct sales force, increased sales commissions due to increased sales, and increased other selling expenses, including credit card processing fees and royalties. These increases were partially offset by decreased expenses related to travel and marketing programs amid travel restrictions in place due to the COVID-19 pandemic.
Operating income for the fourth quarter of 2020 was $21.8 million, compared to an operating loss of $1.8 million for the fourth quarter of 2019, an increase of $23.5 million, primarily due to higher revenue and gross profit compared to the prior year period.
Total other expenses, net, for the fourth quarter of 2020 were $2.9 million, compared to $2.6 million for the fourth quarter of 2019, an increase of $0.3 million, or 11%. The increase was primarily due to higher interest expense resulting from the increased borrowings under the 2019 Credit Agreement.
Net income for the fourth quarter of 2020 was $18.5 million, or $0.16 per share, compared to a net loss of $4.4 million, or $0.04 per share, for the fourth quarter of 2019, an increase of $22.9 million, or $0.20 per share.
Adjusted EBITDA of $24.9 million for the fourth quarter of 2020, compared to Adjusted EBITDA of $0.8 million for the fourth quarter of 2019, an increase of $24.1 million.
As of December 30, 2020, the Company had $84.8 million in cash and restricted cash and $84.8 million in debt obligations, of which $15.1 million were capital lease obligations, compared to $60.4 million in cash and restricted cash and $100.6 million in debt obligations, of which $17.5 million were capital lease obligations as of December 31, 2019.