the patient had a 25% tbsa burn , which included a mixture of second - degree , deep second - degree , and third - degree burns involving the anterior aspect of the right lower extremity , the medial aspect of the left lower extremity , and the dorsum of both feet ( figure 1a ) . b. patient s burns demonstrate conversion of second - degree burns to third - degree burns after 5 days . after 5 days , the patient s burns demonstrated progression from second - degree burns to deeper second - degree and third - degree burns ( figure 1b ) . seven days postinjury , the patient underwent tangential excision of necrotic tissue of her lower extremities , which led to wounds clinically assessed to require fbc matrix and subsequent stsg based on our burn treatment protocol . a total of 1100 cm and 2400 cm of fbc was meshed 3:1 and 4:1 and applied to the debrided areas of the left and right lower extremity , respectively . the wounds were dressed with bridal veil , xeroform , softsorb soaked in an antibiotic solution containing neosporin g.u . the patient s postoperative course was benign , and during her first dressing change ( 3 days postoperatively ) , the fbc was noted to be intact and in the early stages of engraftment ( figure 2a ) . postoperative evaluation after 10 days demonstrated tissue regeneration ( figure 2b ) , and the wounds were deemed suitable for skin grafting . when the patient was taken to the operating room 2 days later for skin grafting , islands of reepithelialization were noted in the center of the wound bed covering areas where fbc was applied . punch biopsies were taken at this time in an effort to elucidate pertinent microscopic activity . a. after 3 days , fbc was adherent to wound bed with granulation tissue beginning to fill the interstices of the fbc . two punch biopsies were taken 12 days post - fbc application as noted in figures 3 and 4 . biopsies were placed in 10% buffered formalin and processed by strata pathology services ( lexington , ma ) . hematoxylin and eosin ( h&e ; polyscientific , bay shore , ny ) staining was performed to assess the dermis . to distinguish between human dermal collagen fibers and bovine collagen fibers , tissue sections were stained with an antibody specific to bovine collagen type i and a fluorescein isothiocyanate conjugated secondary antibody ( millipore , billerica , ma ) . a fluorescent cellular counterstain was used to visualize nuclei within tissue sections ( hoeschst 34580 , life technologies , grand island , ny ) . keratinocytes were identified using antibodies to cytokeratin 5 , a fibrous structural protein , and p63 , an essential transcription factor for epithelial development and proliferation . cd31a was used to evaluate endothelial cell borders , and ki-67 was used as a cellular marker for proliferation . a. a punch biopsy was taken from the right leg as indicated in a1 by the dotted circle . tissue was processed and stained with ( b , c ) h&e , ( d , e ) bovine collagen type i ( green ) and hematoxylin to color cellular nuclei ( blue ) , ( f ) cd31a , ( g ) ki-67 . a. a punch biopsy was taken from the left leg as denoted by the dotted circle . tissue was processed and stained with ( b , c ) h&e , ( d ) bovine collagen type i ( green ) and hematoxylin to color cellular nuclei ( blue ) , ( e ) cd31a , ( f ) ki-67 , ( g ) ck5 , and ( h ) p63 . bv , blood vessels ; ec , epidermal cells ; fbc , fetal bovine collagen ; h&e , hematoxylin and eosin . h&e staining of the biopsy obtained from the right lower extremity demonstrated a full thickness wound containing dermal collagen fibers ( figure 3a  e ) . immunohistochemical staining of serial sections from this biopsy revealed the presence of bovine collagen type i repopulated with the patient s cells ( figure 3e ) . the thickness of this tissue was approximately 1 mm and contained histotypic dermal collagen fibers populated with cells at a similar density to that of uninjured human dermis . proliferating cells and vasculature were found in the fbc , suggesting the repopulation of the dermis with the patient s cells ( figure 4f , g ) . these results represent the early stages of wound healing after fbc application . the biopsy obtained from the left lower extremity revealed islands of reepithelialization that could be seen clinically as well as histologically ( figure 4a  c ) . staining indicated the biopsy contained irregular mixtures of regions with remnants of dermal and epidermal components ( figure 4c , d ) . immunohistochemical staining of serial sections from this biopsy revealed the presence of a 0.75-mm thick region of bovine collagen type i ( figure 4d ) . proliferating cells and vasculature were found throughout the biopsied tissue ( figure 4e , f ) . a stratified squamous epithelium was present on top of the bovine collagen dermal fibers as well as within the interstices of the fbc ( figure 4h , i ) . approximately 1 mm and 2 mm from the surface of the wound , small clusters of keratinocytes were detected adjacent to adipocytes visible by cytokeratin 5 staining . a percentage of the epidermal cells also stained positive for p63 ( figure 4 ) . this biopsy demonstrated the capacity for the fbc to be repopulated and revascularized with the patient s own cells and provided a supportive environment for epidermal cell migration and reepithelialization . during the next few days , wounds covered with fbc continued to undergo reepithelialization , and as a result , on postoperative day 18 , a final decision was made not to perform skin grafting . on postoperative day 26 , significant reepithelialization of her wounds was observable ( figure 5a ) , and the patient was discharged on postoperative day 30 . a. after 26 days , ( b ) 53 days , ( c ) 80 days , ( d ) 102 days , ( e ) 6 months , ( f ) 9 months , ( g ) 12 months , ( h ) 26 months after fbc application . on postoperative day 53 , the patient displayed additional reepithelialization and repigmentation ( figure 5b ) . examination of the patient s skin on postoperative day 80 and day 102 revealed complete wound closure and additional repigmentation ( figure 5c , d ) . subsequent follow - up of the patient after 6 months , 9 months , 12 months , and 26 months revealed healthy , soft , and supple skin , without any visible signs of hypertrophy or fibrosis ( figure 5e  h ) . after 5 days , the patient s burns demonstrated progression from second - degree burns to deeper second - degree and third - degree burns ( figure 1b ) . seven days postinjury , the patient underwent tangential excision of necrotic tissue of her lower extremities , which led to wounds clinically assessed to require fbc matrix and subsequent stsg based on our burn treatment protocol . a total of 1100 cm and 2400 cm of fbc was meshed 3:1 and 4:1 and applied to the debrided areas of the left and right lower extremity , respectively . the wounds were dressed with bridal veil , xeroform , softsorb soaked in an antibiotic solution containing neosporin g.u . the patient s postoperative course was benign , and during her first dressing change ( 3 days postoperatively ) , the fbc was noted to be intact and in the early stages of engraftment ( figure 2a ) . postoperative evaluation after 10 days demonstrated tissue regeneration ( figure 2b ) , and the wounds were deemed suitable for skin grafting . when the patient was taken to the operating room 2 days later for skin grafting , islands of reepithelialization were noted in the center of the wound bed covering areas where fbc was applied . punch biopsies were taken at this time in an effort to elucidate pertinent microscopic activity . a. after 3 days , fbc was adherent to wound bed with granulation tissue beginning to fill the interstices of the fbc . two punch biopsies were taken 12 days post - fbc application as noted in figures 3 and 4 . biopsies were placed in 10% buffered formalin and processed by strata pathology services ( lexington , ma ) . hematoxylin and eosin ( h&e ; polyscientific , bay shore , ny ) staining was performed to assess the dermis . to distinguish between human dermal collagen fibers and bovine collagen fibers , tissue sections were stained with an antibody specific to bovine collagen type i and a fluorescein isothiocyanate conjugated secondary antibody ( millipore , billerica , ma ) . a fluorescent cellular counterstain was used to visualize nuclei within tissue sections ( hoeschst 34580 , life technologies , grand island , ny ) . keratinocytes were identified using antibodies to cytokeratin 5 , a fibrous structural protein , and p63 , an essential transcription factor for epithelial development and proliferation . cd31a was used to evaluate endothelial cell borders , and ki-67 was used as a cellular marker for proliferation . a. a punch biopsy was taken from the right leg as indicated in a1 by the dotted circle . ( d , e ) bovine collagen type i ( green ) and hematoxylin to color cellular nuclei ( blue ) , ( f ) cd31a , ( g ) ki-67 . a. a punch biopsy was taken from the left leg as denoted by the dotted circle . tissue was processed and stained with ( b , c ) h&e , ( d ) bovine collagen type i ( green ) and hematoxylin to color cellular nuclei ( blue ) , ( e ) cd31a , ( f ) ki-67 , ( g ) ck5 , and ( h ) p63 . bv , blood vessels ; ec , epidermal cells ; fbc , fetal bovine collagen ; h&e , hematoxylin and eosin . h&e staining of the biopsy obtained from the right lower extremity demonstrated a full thickness wound containing dermal collagen fibers ( figure 3a  e ) . immunohistochemical staining of serial sections from this biopsy revealed the presence of bovine collagen type i repopulated with the patient s cells ( figure 3e ) . the thickness of this tissue was approximately 1 mm and contained histotypic dermal collagen fibers populated with cells at a similar density to that of uninjured human dermis . proliferating cells and vasculature were found in the fbc , suggesting the repopulation of the dermis with the patient s cells ( figure 4f , g ) . these results represent the early stages of wound healing after fbc application . the biopsy obtained from the left lower extremity revealed islands of reepithelialization that could be seen clinically as well as histologically ( figure 4a  c ) . staining indicated the biopsy contained irregular mixtures of regions with remnants of dermal and epidermal components ( figure 4c , d ) . immunohistochemical staining of serial sections from this biopsy revealed the presence of a 0.75-mm thick region of bovine collagen type i ( figure 4d ) . proliferating cells and vasculature were found throughout the biopsied tissue ( figure 4e , f ) . a stratified squamous epithelium was present on top of the bovine collagen dermal fibers as well as within the interstices of the fbc ( figure 4h , i ) . approximately 1 mm and 2 mm from the surface of the wound , small clusters of keratinocytes were detected adjacent to adipocytes visible by cytokeratin 5 staining . a percentage of the epidermal cells also stained positive for p63 ( figure 4 ) . this biopsy demonstrated the capacity for the fbc to be repopulated and revascularized with the patient s own cells and provided a supportive environment for epidermal cell migration and reepithelialization . h&e staining of the biopsy obtained from the right lower extremity demonstrated a full thickness wound containing dermal collagen fibers ( figure 3a  e ) . immunohistochemical staining of serial sections from this biopsy revealed the presence of bovine collagen type i repopulated with the patient s cells ( figure 3e ) . the thickness of this tissue was approximately 1 mm and contained histotypic dermal collagen fibers populated with cells at a similar density to that of uninjured human dermis . proliferating cells and vasculature were found in the fbc , suggesting the repopulation of the dermis with the patient s cells ( figure 4f , g ) . the biopsy obtained from the left lower extremity revealed islands of reepithelialization that could be seen clinically as well as histologically ( figure 4a  c ) . staining indicated the biopsy contained irregular mixtures of regions with remnants of dermal and epidermal components ( figure 4c , d ) . immunohistochemical staining of serial sections from this biopsy revealed the presence of a 0.75-mm thick region of bovine collagen type i ( figure 4d ) . proliferating cells and vasculature were found throughout the biopsied tissue ( figure 4e , f ) . a stratified squamous epithelium was present on top of the bovine collagen dermal fibers as well as within the interstices of the fbc ( figure 4h , i ) . approximately 1 mm and 2 mm from the surface of the wound , small clusters of keratinocytes were detected adjacent to adipocytes visible by cytokeratin 5 staining . a percentage of the epidermal cells also stained positive for p63 ( figure 4 ) . this biopsy demonstrated the capacity for the fbc to be repopulated and revascularized with the patient s own cells and provided a supportive environment for epidermal cell migration and reepithelialization . during the next few days , wounds covered with fbc continued to undergo reepithelialization , and as a result , on postoperative day 18 , a final decision was made not to perform skin grafting . on postoperative day 26 , significant reepithelialization of her wounds was observable ( figure 5a ) , and the patient was discharged on postoperative day 30 . a. after 26 days , ( b ) 53 days , ( c ) 80 days , ( d ) 102 days , ( e ) 6 months , ( f ) 9 months , ( g ) 12 months , ( h ) 26 months after fbc application . long - term follow - up of the patient after discharge was uneventful . on postoperative day 53 examination of the patient s skin on postoperative day 80 and day 102 revealed complete wound closure and additional repigmentation ( figure 5c , d ) . subsequent follow - up of the patient after 6 months , 9 months , 12 months , and 26 months revealed healthy , soft , and supple skin , without any visible signs of hypertrophy or fibrosis ( figure 5e  h ) . in this case study , we report on a patient with a 25% tbsa burn treated with fbc matrix postexcision that healed without subsequent autologous skin grafting . long - term evaluation after 26 months post - fbc application indicated healthy skin , without any visible signs of disfigurement . moreover , repigmentation was visible over 85% of the treated areas . immunohistological analysis of biopsies obtained 12 days post - fbc application demonstrated that the fbc was capable of generating a dermal component approximately 0.75 mm to 1 mm in thickness with the capacity to support reepithelialization . additionally , it was noted that the wound bed contained a mixture of full thickness and deep partial thickness zones . staining for human keratinocyte markers indicated small islands of remaining epidermal cells found adjacent to the deep reticular dermis . keratinocytes located next to the intradermal epithelial structures are hypothesized to have migrated through the fbc matrix and contribute to the reepithelialization of the wound . although biopsies were not obtained at later time points , it can be inferred that a fully stratified layer of keratinocytes formed and that a basement membrane was established between the epidermal and dermal components of the skin , based on the continued durability of the skin and the lack of recidivism observed during follow - up . the results from this case demonstrate a potential treatment strategy to reduce the amount of donor skin needed to reconstruct wounds during surgical intervention , especially wounds with indeterminate depth . the burn injury may be excised , treated with fbc to regenerate dermal tissue , and reassessed to determine areas requiring skin grafting based on the amount of reepithelialization . if reepithelialization is not noted within 2 to 3 weeks , there is no delay in treatment regimen , and autologous skin grafting can proceed over the newly generated dermal tissue as originally planned . however , if areas of reepithelialization are visible , close monitoring of the rate of reepithelialization is necessary to determine whether the reepithelialization may result in the closure of the wound without stsg . long - term follow - up indicated excellent functional and cosmetic outcomes for an injury of this extent and size that healed without autologous grafting . consistent with previous reports that use fbc , the outcomes of this study suggest that the regenerated dermal tissue aided by the fbc contributed to the durability , functionality , and appearance of the healed wound . in summary , these results encourage further use of fbc to treat patients with deep partial thickness and full thickness burns for possible wound coverage .
the treatment of full thickness skin wounds commonly associated with large burns continues to represent a challenging clinical entity . 
 the current treatment for large tbsa burns is split thickness autologous skin grafting ; however , this treatment often results in poor textural durability , hypertrophic scarring , and fibrotic contractures . in this case report , we describe our experience and long - term follow - up results after the application of fetal bovine collagen ( fbc ) matrix ( primatrix , tei biosciences , boston , ma ) to burn wounds clinically assessed as full thickness that healed without the need for subsequent skin grafting . 
 the patient presented with 25% tbsa burns and was debrided and covered with fbc on postburn day 7 . by postoperative day 12 , the patient had large areas of reepithelialization distributed throughout the wound bed . by postoperative day 26 , 
 the patient had significantly more areas of wound closure and was discharged . 
 reepithelialization and repigmentation continued , and long - term follow - up after 26 months demonstrated complete reepithelialization and nearly complete repigmentation , without the appearance of contractures or hypertrophic scarring . 
 this case report highlights the use of fbc as a scaffold capable of dermal regeneration and spontaneous reepithelialization with an excellent long - term functional and cosmetic outcome .