Abstract

Background: The ideal product for soft tissue replacement is durable, nonimmunogenic, and noninfectious. AlloDerm (LifeCell Corp., Branchburg, New Jersey), Enduragen (Stryker Corp., Kalamazoo, Michigan), and DermaMatrix (Synthes, Inc., West Chester, Pennsylvania) are frequently used for soft tissue replacement, but comparative analysis of these materials over an extended time period has not been reported. DuraMatrix (bovine tendon matrix; Stryker Corp.) is also promising, demonstrating desirable properties not only as a dural substitute but also for soft tissue replacement.

Objectives: The authors analyze in vivo gross and microscopic changes over time with four commercially available dermal matrices, utilizing the murine model for a controlled environment.

Methods: AlloDerm, Enduragen, DermaMatrix, and DuraMatrix implants measuring 1 × 1 cm were each implanted in 40 adult mice, in individual dorsal submuscular pockets. The mice were then sacrificed in groups of 10 at three, six, nine, and 12 months. The implants and surrounding tissues were excised and evaluated for gross and microscopic appearance.

Results: Histological analysis of the specimens demonstrated similar encapsulation, implant infiltration, and surrounding inflammation over time. Enduragen implants demonstrated the least amount of host cell infiltration, whereas AlloDerm demonstrated the most. Grossly, Enduragen maintained its original shape and became firmer over time, whereas AlloDerm became spherical and softer. DermaMatrix and DuraMatrix both maintained their original shape and consistency. Implant migration, explantation, infection, or allergic reactions were not noted.

Conclusions: All of the materials studied demonstrated high levels of host tolerance and tissue integration. AlloDerm demonstrated signs of resorption, whereas Enduragen maintained its size and became firmer in consistency. Together with the histological results, this suggests a proportional relationship between the amount of host cell integration and implant resorption.

As survival rates from cancer, trauma, and other destructive processes have increased, today’s plastic surgeon faces an increased demand for soft tissue reconstruction. In response to this demand, multiple alloplastic and synthetic materials have been developed, providing valuable treatment options for many types of reconstruction. Acellular dermal matrices (ADM) have been central to these developments. These allogenic products, composed mostly of collagen and elastin proteins, act as scaffolding into which host cells can incorporate, providing durable soft tissue replacement with high levels of tolerance, low antigenicity, and no donor site morbidity.1

These products are composed of either human or porcine dermis that is rendered acellular by franchised and undisclosed methods. At the time of inception of this study, two of the most commonly utilized matrices were AlloDerm (LifeCell Corp., Branchburg, New Jersey) and DermaMatrix (Synthes, Inc., West Chester, Pennsylvania). Two less commonly used materials were Enduragen and DuraMatrix (both manufactured by Stryker Corp., Kalamazoo, Michigan) (Table 1). AlloDerm, which is composed of human cadaver dermis, remains frequently utilized despite published data indicating that when subject to significant forces (such as those seen in abdominal wall reconstruction), significant stretching and a reduction in overall size of the implant occur over time.2,3 When compared with Enduragen, AlloDerm has a higher load-to-failure but stretches more significantly.4 In a previous study, DermaMatrix and AlloDerm showed similar levels of neovascularization and host tissue integration in mastectomy sites of patients undergoing expander-based reconstruction.5 DuraMatrix, which is composed of bovine Achilles tendon Type I collagen, was formulated for use as a dural substitute but demonstrates qualities similar to those desired of dermal matrices.

Multiple studies, including previous studies performed by the authors, have evaluated and compared the individual properties of multiple dermal matrices.6,7 The current study expands on our previous studies by utilizing a larger sample size and comparing all four dermal matrices: AlloDerm, Enduragen, DermaMatrix, and DuraMatrix. The purpose of this study was to analyze the in vivo gross and microscopic changes over time with four commercially available dermal matrices, utilizing the murine model for a controlled environment.

Table 1.

Qualities of Each Dermal Matrix Soft Tissue Substitute

Product Source Sterility Processing Information CrossLinked 
AlloDerm (LifeCell Corp.) Cadaveric human acellular dermis Considered “aseptic” A buffered salt solution eliminates the epidermis. Next, unwanted cell types within the dermis are solubilized and washed away using a patented sequence of nondenaturing detergent washes. The processed tissue is then preserved using a patented freeze-drying process. Non-crosslinked 
DermaMatrix (Stryker Corp.) Cadaveric human acellular dermis Passes USP <71> for sterility Salt solution and detergent remove epidermis and dermis, followed by treatment in a disinfectant solution that combines detergents with acidic and antiseptic reagents. Next, it is freeze-dried and packed in a terminally sterilized double pouch and envelope. Non-crosslinked 
Enduragen (Synthes, Inc.) Bovine dermis Sterilely supplied Proprietary enzymatic digestion and crosslinking manufacturing process Crosslinked 
DuraMatrix (Stryker Corp.) Highly purified Type I collagen from bovine Achilles tendon Sterilely supplied Proprietary chemical cleansing, sheet processing, dehydration for packing Crosslinked 
Product Source Sterility Processing Information CrossLinked 
AlloDerm (LifeCell Corp.) Cadaveric human acellular dermis Considered “aseptic” A buffered salt solution eliminates the epidermis. Next, unwanted cell types within the dermis are solubilized and washed away using a patented sequence of nondenaturing detergent washes. The processed tissue is then preserved using a patented freeze-drying process. Non-crosslinked 
DermaMatrix (Stryker Corp.) Cadaveric human acellular dermis Passes USP <71> for sterility Salt solution and detergent remove epidermis and dermis, followed by treatment in a disinfectant solution that combines detergents with acidic and antiseptic reagents. Next, it is freeze-dried and packed in a terminally sterilized double pouch and envelope. Non-crosslinked 
Enduragen (Synthes, Inc.) Bovine dermis Sterilely supplied Proprietary enzymatic digestion and crosslinking manufacturing process Crosslinked 
DuraMatrix (Stryker Corp.) Highly purified Type I collagen from bovine Achilles tendon Sterilely supplied Proprietary chemical cleansing, sheet processing, dehydration for packing Crosslinked 

Methods

Study Design

The study was approved by the Institutional Animal Care and Use Committee at the Baylor College of Medicine. After receiving approval, 40 adult ICR strain mice were implanted with each of the four dermal matrix materials. Each 1 × 1-cm implant was placed into an individual dorsal, submuscular pocket. The subjects were randomly assigned into groups of 10; the groups were subsequently sacrificed at four time intervals (three, six, nine, and 12 months). At the time of sacrifice, the implanted materials and surrounding tissues were excised. The gross appearance of the implanted materials and surrounding tissues was noted, and the tissues were sectioned for histologic analysis. In addition to gross and microscopic appearance, the mice were also examined for implant migration or extrusion.

Surgical Technique: Graft Implantation

All mice were initially anesthetized with a single intramuscular injection of ketamine, xylazine, and acepromazine solution in accordance with subject mass. The dorsal aspect was then shaved and prepared with a povidone-iodine (Betadine; Purdue Frederick Co., Norwalk, Connecticut) solution. Following adequate sedation, 0.1 mL of 0.1% lidocaine with 1:1,000,000 epinephrine was injected into the subcutaneous plane along each of the four proposed incisions (cranial and caudal aspects of the dorsum, bilaterally). Four longitudinal incisions were then made along the dorsum, each measuring 1 cm. Blunt dissection was carried out to divide four isolated, subcutaneous pockets measuring approximately 1.5 × 1.5 cm. With a single implant allotted to a single pocket, standardized 1 × 1-cm implants of AlloDerm, Enduragen, DermaMatrix, and DuraMatrix were then placed subcutaneously. The implants were oriented identically in each animal. Each implant was anchored to underlying fascia with a single 6-0 rapid-absorbing catgut suture. Each pocket was then irrigated with sterile saline and closed with a continuous resorbable suture. At completion, each murine subject possessed individual, isolated implants of AlloDerm, Enduragen, DermaMatrix, and DuraMatrix.

Surgical Technique: Graft Harvest and Histological Analysis

Following carbon dioxide euthanasia of the animals, full pelts were harvested at each of the four time points: three, six, nine, and 12 months (Figure 1). Great care was taken to complete the excision with all implanted materials and surrounding tissues intact. Extracted specimens were evaluated for their gross appearance, including shape, texture, rigidity, and signs of implant migration or extrusion. All specimens then underwent hematoxylin and eosin (H&E) staining in a standardized fashion, as follows.

Figure 1.

Two dorsal soft tissue pelts (harvested from two mice) show preservation of the encapsulation around the implants.

Figure 1.

Two dorsal soft tissue pelts (harvested from two mice) show preservation of the encapsulation around the implants.

The tissue was processed following an adequate fixation period in 10% buffered formalin. The resultant formalin-fixed tissue underwent grade alcohol and xylene dehydration and paraffin embedding. The paraffin-embedded tissue underwent sectioning on a tissue microtome, with 3-µm sections placed on glass slides. The glass slides were stained with hematoxylin and eosin (H&E) using an automated slide stainer. The stained slides were then coverslipped with an automated coverslipper. The specimens were examined for surrounding capsule thickness, inflammation and cellular components, and collagen ingrowth within the dermal matrix.

Results

Gross Examination

On gross examination, all implants retained approximately the same dimensions as upon implantation; however, objective measurement of mass or volume could not be accurately completed due to the lack of a distinct interface between the implant and host tissue, especially over longer time periods. Neighboring dermal, subcutaneous, and muscular tissues appeared relatively unaffected by implant materials, and no signs of infection or allergic reaction were present. There was no incidence of graft migration or extrusion.

The texture and shape of both DermaMatrix and DuraMatrix remained largely unchanged over all time periods. AlloDerm was noted to be softer and more spherical in shape upon explantation, showing signs of resorption. Enduragen was noted to be more firm but retained the same shape as upon implantation (Figure 2; Table 2).

Figure 2.

A representative sample of the mouse pelt, showing the spherical change in shape that occurred in the AlloDerm implant (arrow).

Figure 2.

A representative sample of the mouse pelt, showing the spherical change in shape that occurred in the AlloDerm implant (arrow).

Table 2.

Key Histological and Gross Findings

 Three Months Six Months Nine Months One Year Host Cell Infiltration Shape and Consistency 
AlloDerm (LifeCell Corp.) •Thin fibrous capsule surrounding implant with minimal chronic inflammation •Thickening of fibrous capsule
• Marked chronic inflammatory reaction at implant periphery with infiltration of implant material
• Occasional foreign body giant cells 
•Increased thickness of fibrous capsule
• Scattered inflammatory cells in fibrous capsule
• Absence of marked inflammatory reaction at implant periphery 
•Dense connective tissue capsule with abundant chronic inflammation
• Inflammatory cells infiltrate into periphery of implant material
• Dense eosinophilic appearance to collagen fibers in implant
• Apparent rupture of implant material in one animal with foreign body giant cell inflammatory reaction and cholesterol clefts 
High Decreasing rigidity, spherical 
Enduragen (Stryker Corp.) •Thin to moderately thickened fibrous capsule surrounding implant
• Minimal to no inflammatory response 
•Moderately thickened fibrous capsule surrounding implant
• Dense chronic inflammatory infiltrate at periphery of implant with infiltration of implant at periphery
• Occasional foreign body giant cells 
•Moderately dense fibrous capsule surrounding implant with rare scattered chronic inflammatory cells •Moderately dense fibrous capsule surrounding implant
• Focal areas with minimal to mild chronic inflammation at periphery of implant 
Low Became rigid, retained shape 
DermaMatrix (Synthes, Inc.) •Mildly to focally moderately thickened fibrous capsule
• Minimal chronic inflammation 
•Moderately thickened fibrous capsule
• Marked chronic inflammation at periphery of implant with infiltration of periphery of implant
•Occasional foreign body giant cells 
•Mild to moderate fibrous capsule
• Minimal chronic inflammation
• Dense eosinophilic collagen fibers in implant 
•Moderately thickened fibrous capsule
• Mild to moderate chronic inflammation at implant periphery
• Dense eosinophilic collagen fibers in implant 
Medium Unchanged 
DuraMatrix (Stryker Corp.) •Maintained shape and consistency
• Minimal inflammation with thin capsule formation 
•Thin capsule again noted
•Moderate chronic inflammation at the implant periphery 
•Moderately thickened capsule with mild to moderate inflammatory reaction scattered throughout
• Superficial fibroblastic infiltration of the implant seen 
•Moderately thickened capsule with mild to moderate inflammatory reaction scattered throughout, which was relatively unchanged from previous time point
• More extensive superficial infiltration of the implant material
• Interface between capsule and implant less well-defined. 
Medium Unchanged 
 Three Months Six Months Nine Months One Year Host Cell Infiltration Shape and Consistency 
AlloDerm (LifeCell Corp.) •Thin fibrous capsule surrounding implant with minimal chronic inflammation •Thickening of fibrous capsule
• Marked chronic inflammatory reaction at implant periphery with infiltration of implant material
• Occasional foreign body giant cells 
•Increased thickness of fibrous capsule
• Scattered inflammatory cells in fibrous capsule
• Absence of marked inflammatory reaction at implant periphery 
•Dense connective tissue capsule with abundant chronic inflammation
• Inflammatory cells infiltrate into periphery of implant material
• Dense eosinophilic appearance to collagen fibers in implant
• Apparent rupture of implant material in one animal with foreign body giant cell inflammatory reaction and cholesterol clefts 
High Decreasing rigidity, spherical 
Enduragen (Stryker Corp.) •Thin to moderately thickened fibrous capsule surrounding implant
• Minimal to no inflammatory response 
•Moderately thickened fibrous capsule surrounding implant
• Dense chronic inflammatory infiltrate at periphery of implant with infiltration of implant at periphery
• Occasional foreign body giant cells 
•Moderately dense fibrous capsule surrounding implant with rare scattered chronic inflammatory cells •Moderately dense fibrous capsule surrounding implant
• Focal areas with minimal to mild chronic inflammation at periphery of implant 
Low Became rigid, retained shape 
DermaMatrix (Synthes, Inc.) •Mildly to focally moderately thickened fibrous capsule
• Minimal chronic inflammation 
•Moderately thickened fibrous capsule
• Marked chronic inflammation at periphery of implant with infiltration of periphery of implant
•Occasional foreign body giant cells 
•Mild to moderate fibrous capsule
• Minimal chronic inflammation
• Dense eosinophilic collagen fibers in implant 
•Moderately thickened fibrous capsule
• Mild to moderate chronic inflammation at implant periphery
• Dense eosinophilic collagen fibers in implant 
Medium Unchanged 
DuraMatrix (Stryker Corp.) •Maintained shape and consistency
• Minimal inflammation with thin capsule formation 
•Thin capsule again noted
•Moderate chronic inflammation at the implant periphery 
•Moderately thickened capsule with mild to moderate inflammatory reaction scattered throughout
• Superficial fibroblastic infiltration of the implant seen 
•Moderately thickened capsule with mild to moderate inflammatory reaction scattered throughout, which was relatively unchanged from previous time point
• More extensive superficial infiltration of the implant material
• Interface between capsule and implant less well-defined. 
Medium Unchanged 

Histological Analysis: AlloDerm

At three months, AlloDerm implants demonstrated a thin, fibrous capsule surrounding the implant with minimal chronic inflammation (Figure 3). AlloDerm samples from the six-month time point displayed a thickened fibrous capsule and occasional foreign body giant cells (Figure 4). In addition, these specimens were associated with a marked chronic inflammatory reaction and a slight inflammatory infiltrate within peripheral implant tissues. At nine months, these implants showed increased thickness of the fibrous capsule with infrequent intracapsular inflammation. AlloDerm samples harvested at 12 months displayed dense connective tissue capsules with abundant chronic inflammation and a dense eosinophilic appearance to the intraimplant collagen fibers (Figure 5). In addition, a single AlloDerm implant specimen demonstrated apparent rupture. The histological evaluation in this case showed a marked foreign body giant cell inflammatory reaction with cholesterol clefts.

Figure 3.

An AlloDerm implant is shown three months postimplantation, demonstrating a thin, fibrous capsule (arrows) surrounding the implant with minimal chronic inflammation. (Hematoxylin and eosin staining)

Figure 3.

An AlloDerm implant is shown three months postimplantation, demonstrating a thin, fibrous capsule (arrows) surrounding the implant with minimal chronic inflammation. (Hematoxylin and eosin staining)

Figure 4.

An AlloDerm implant is shown six months postimplantation, displaying a thickened fibrous capsule (short arrows) and occasional foreign body giant cells (long arrow). (Hematoxylin and eosin staining)

Figure 4.

An AlloDerm implant is shown six months postimplantation, displaying a thickened fibrous capsule (short arrows) and occasional foreign body giant cells (long arrow). (Hematoxylin and eosin staining)

Figure 5.

An AlloDerm implant is shown 12 months postimplantation, displaying a dense connective tissue capsule (short arrow) with abundant chronic inflammation (long arrow). (Hematoxylin and eosin staining)

Figure 5.

An AlloDerm implant is shown 12 months postimplantation, displaying a dense connective tissue capsule (short arrow) with abundant chronic inflammation (long arrow). (Hematoxylin and eosin staining)

Histological Analysis: Enduragen

At three months, Enduragen demonstrated a thin fibrous capsule surrounding the implant with a minimal inflammatory response. At six months, these samples displayed moderately thickened fibrous implant capsules with occasional foreign body giant cells. In addition, a dense chronic inflammatory infiltrate was noted within peripheral Enduragen tissues (Figure 6). The nine-month time point was marked by moderately dense fibrous capsules surrounding the implants with rare scattered chronic inflammatory cells. At the final harvest time point, moderately dense fibrous implant capsules were associated with focal areas of minimal-to-mild chronic inflammation along the periphery.

Figure 6.

An Enduragen implant is shown six months postimplantation, displaying a moderately thickened fibrous implant capsule (short arrow) with occasional foreign body giant cells (not shown). In addition, a dense chronic inflammatory infiltrate (long arrow) was noted within the periphery of the implant. (Hematoxylin and eosin staining)

Figure 6.

An Enduragen implant is shown six months postimplantation, displaying a moderately thickened fibrous implant capsule (short arrow) with occasional foreign body giant cells (not shown). In addition, a dense chronic inflammatory infiltrate (long arrow) was noted within the periphery of the implant. (Hematoxylin and eosin staining)

Histological Analysis: DermaMatrix

At three months, DermaMatrix implant capsules were mildly thickened with minimal adjacent chronic inflammation. DermaMatrix samples at six months displayed moderately thickened fibrous capsules and occasional foreign body giant cells. In addition, peripheral implant materials were infiltrated with a significant chronic inflammation. At both nine and 12 months, DermaMatrix samples were marked by moderately thickened fibrous implant capsules, with dense eosinophilic collagen fibers within implant tissues (Figure 7).

Figure 7.

A DermaMatrix implant is shown nine months postimplantation, marked by a moderately thickened fibrous implant capsule (arrow) with dense eosinophilic collagen fibers within the implant. (Hematoxylin and eosin staining)

Figure 7.

A DermaMatrix implant is shown nine months postimplantation, marked by a moderately thickened fibrous implant capsule (arrow) with dense eosinophilic collagen fibers within the implant. (Hematoxylin and eosin staining)

Histological Analysis: DuraMatrix

At three months, DuraMatrix demonstrated minimal inflammation with thin capsule formation. At six months, there was a mildly thickened fibrous capsule with moderate chronic inflammation at the implant periphery. At nine months, there was a moderately thickened fibrous capsule, with a mild to moderate inflammatory reaction scattered throughout. Additionally, superficial fibroblastic infiltration of the implant was observed (Figure 8). Finally, at 12 months, there was a moderately thickened capsule similar to that seen at nine months. Mild to moderate inflammatory reaction was also seen scattered throughout the fibrous capsule. There was superficial infiltration of implant material at the periphery, and the interface between capsule and implant had become ill-defined, with more extensive fibroblastic infiltration of the implant material.

Figure 8.

A DuraMatrix implant is shown nine months postimplantation, demonstrating a moderately thickened fibrous capsule (short arrow) with a mild to moderate inflammatory reaction (long arrow) scattered throughout the fibrous capsule. Superficial fibroblastic infiltration of the implant was also seen (not shown). (Hematoxylin and eosin staining)

Figure 8.

A DuraMatrix implant is shown nine months postimplantation, demonstrating a moderately thickened fibrous capsule (short arrow) with a mild to moderate inflammatory reaction (long arrow) scattered throughout the fibrous capsule. Superficial fibroblastic infiltration of the implant was also seen (not shown). (Hematoxylin and eosin staining)

Discussion

The ideal soft tissue substitute must be durable, nonantigenic, noninfectious, and well-tolerated by the host. In addition, many specific applications require additional characteristics, such as soft consistency for breast reconstruction, the ability to withstand multiple vectors of tension for abdominal wall hernia repair, and firm consistency for dorsal nasal reconstruction.8,9 Despite the relative success of ADM for soft tissue reconstruction, it is still important to further demarcate which substitutes are best suited for which type of reconstruction, to minimize complications and the need for surgical revision.

Although the knowledge regarding these products is continually increasing, there is a lack of data that compare the individual products in a prospective and, more importantly, controlled environment. Although animal studies may be limited in terms of clinical implications, they provide an even ground upon which future and more specific clinical comparisons can be made. In the present study, implantation of the products in the same animal provided a high level of control and minimized the chances of individual variability.

The results of our study indicate that all of the implants have a high level of tolerance in the murine model. This was exemplified by the lack of implant extrusion, migration, infection, or allergic reaction. In this study, there was no evidence of intense inflammatory response to any of the materials, attesting to the minimal antigenicity of these products. As with all foreign bodies, the host is initially unable to resorb implanted dermal matrices. Instead, surrounding inflammation gives way to encapsulation, inflammatory cell infiltration, and eventual fibrovascular ingrowth. By three months, the process of encapsulation was apparent in all samples. At this time point, Enduragen samples demonstrated a minimal inflammatory response in comparison to the more moderate inflammatory reaction to the human cadaveric implants. Although Enduragen eventually displayed a similar inflammatory cell infiltration, this did not occur until the nine-month time point. These findings suggest that the porcine matrix is more impervious to inflammatory cells than its human cadaveric counterparts. This resistance to infiltration may be secondary to its franchised preparation process, which is known to consist of more extensive collagen crosslinking, or may be secondary to another factor related to its xenographic nature. More importantly, the relative resistance of Enduragen to host cell infiltration may be the reason the product retains its shape and firmness compared to other human-derived products. As the literature describes, Enduragen is comparable to ear cartilage grafts in providing rigid support for reconstructive and aesthetic support of the eyelid.10

Conversely, at the final 12-month time period, AlloDerm demonstrated the highest level of host cells within the implant material. This finding supports the idea that the amount of host cell infiltration dictates changes in consistency: higher levels of infiltration cause increased resorption of the scaffolding proteins and loss of shape, and low levels of infiltration cause less resorption and a persistent (or even increased) firmness of the implant. The concept of host cell integration causing a more supple consistency in the dermal matrix also makes sense intuitively. Adding host cells to a scaffolding system that is basically human dermis without host cells should yield a result similar to native dermis (Table 2).2

High levels of resorption with AlloDerm have previously been described in the literature. Sclafani et al3 found a 50% decrease in size of AlloDerm sheets within the first six months of implantation, after which the size stabilized. Owens and Yukna11 found “complete degradation of the [AlloDerm] substrate.” Butler et al12 demonstrated that changes in stretch and consistency of AlloDerm were dependent on the tension placed on it during surgical placement.

Although all of the dermal matrices incorporated well into the host tissues, our study provided evidence that the various types of matrices behave differently on histological and macroscopic levels. Specifically, AlloDerm demonstrated more resorption and softening, whereas Enduragen had a more persistent and rigid structure. Also of note is that DuraMatrix, which is not currently widely used for soft tissue reconstruction, performed similarly to the other dermal matrices in vivo and because of this should be included in further comparative studies of soft tissue substitutes. Additionally, DermaMatrix performed similarly to DuraMatrix, retaining its structure with a moderate host cell infiltration and thickened capsule. However, it had a larger degree of superficial infiltration of the implant material and a less well-defined interface between the capsule and the implant.

The presence of collagen crosslinking may have played a role in some of the outcomes of this study. Crosslinking is meant to reduce resorption and improve fibroblast infiltration into the dermal matrix. In this study, collagen crosslinking appeared to reduce host cell infiltration, which allowed the material to retain its rigidity and shape; however, this was also associated with a reduction in collagen infiltration into the implant, when compared to the non-crosslinked materials.

It should be noted that the data in this study cannot be used to provide absolute indications and contraindications for the placement of specific types of dermal matrices in specific clinical scenarios for several reasons. First, these results occurred in a murine model, and it still remains unclear to what degree, if at all, these results would correlate with results in the clinical setting. Second, because tension plays a role in the long-term biomechanical and structural changes associated with the materials, it is unclear whether these findings would hold true for breast and abdominal wall reconstruction, where significant forces are involved. However, the study does provide sound data that are consistent with previous reports of clinical findings.

Conclusions

In this study comparing the in vivo and gross microscopic changes over time with four soft tissue replacement materials, the results demonstrated a difference in the mechanical behavior of AlloDerm and Enduragen implants in a murine model. AlloDerm demonstrated signs of resorption, softening, and change in shape, whereas Enduragen demonstrated persistence in shape and increased firmness with time. DuraMatrix, a relatively new option, should be considered in future investigations as another dermal matrix soft tissue substitute.

Disclosures

The authors declared no potential conflicts of interest with respect to the authorship and publication of this article.

Funding

The Stryker Corporation provided funding for the purchasing of animals, animal housing, and food expenses, funding for personnel based on hours worked towards the completion of this project, and funded the purchase of the different dermal matrix substitutes.

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