A Biodegradable Polyurethane Dermal Matrix in Reconstruction of Free Flap Donor Sites

A Pilot Study

Marcus J.D. Wagstaff, BSc(Hons), MBBS, PhD, FRCS(Plast), FRACS; Bradley J. Schmitt, BAppSc, MPhys; Patrick Coghlan, MBBS; James P. Finkemeyer, BBioMedSci, BMBS; Yugesh Caplash, MBBS, MS, MCh, FRACS; John E. Greenwood, AM, BSc(Hons), MBChB, MD, DHlthSc, FRCS(Eng), FRCS(Plast), FRACS

Disclosures

ePlasty. 2015;15 

In This Article

Abstract and Introduction

Abstract

We have developed a biodegradable temporizing matrix (BTM) capable of supporting secondary split-skin graft-take in animal studies. We report its first long-term implantation and use as a dermal scaffold in humans. This preliminary study assesses its ability to integrate, its ease of delamination, its ability to sustain split-skin graft in complex wounds, the degree of wound contraction, and ultimately the quality of the scar at 1 year postimplantation. Ten patients were recruited, each requiring elective free flap reconstruction. Free flap donor sites created were anterolateral thigh flaps, fibular osseocutaneous flaps, or radial/ulnar forearm (RF/UF) flaps. The BTM was implanted when the flap was detached from its donor site. Dressing changes were performed twice weekly. The time elapsed between implantation and delamination depended on the type of flap and thus the wound bed left. Once integrated, the BTMs were delaminated in theatre, and the surface of the "neodermis" was refreshed by dermabrasion, prior to application of a split-skin graft. The BTM integration occurred in all patients (100% in 6 patients, with 90%, 84%, 76%, and 60% integration in the remainder). Integrated BTM sustained successful graft-take in all patients. Complete take was marred in 2 patients, over areas of BTM that had not integrated and graft application was performed too early. The BTM can be applied into wounds in humans and can integrate, persist in the presence of infection, and sustain split-skin overgrafting, despite the trial group presenting with significant comorbidities.

Introduction

We have been developing a totally synthetic dermal replacement scaffold for use in major burn injury, using a polyurethane open-cell foam (Novosorb).[1–7] The primary aims of this dressing are (1) to temporize extensive debrided wounds while waiting for donor site recovery for delayed split-skin grafting, (2) to allow integration of vascular tissue into the foam to create a neodermis, (3) to sustain split-skin grafting once integrated, and (4) to reduce wound contraction during the remodeling phase. The secondary goal is to provide a platform onto which an autologous cultured composite skin can be applied, thus eliminating the need for extensive split-skin graft harvest.

The foam is 2-mm-thick and biodegradable by hydrolysis, with a nonbiodegradable polyurethane seal bonded to the upper surface. Unlike other dermal replacement technologies, it does not contain any biological molecules such as collagen, potentially offering a greater resistance to infection. This has been reported in porcine studies with up to 4 weeks' exposure and stable graft take. The bonded seal prevents evaporative water loss and, after integration, is peeled away to expose the vascularized foam for skin grafting.

Successful integration and split-skin graft take has been demonstrated in controlled wounds in pigs over 4 weeks and the design was further optimized. To assess the safety of short-term human implantation, we performed a randomized control trial, using the unsealed foam in a thick form as a topical negative pressure in pressure ulcers, with the foam replaced every 2 to 3 days over an 8-week period. No adverse reactions were noted, and the foam was performed as effectively as the control dressing.[8]

To study long-term implantation, integration, contraction, and scar outcomes, we proposed its use in a cohort of elective, complex, full-thickness wounds normally requiring skin graft cover, namely free-flap donor sites. In particular, split-skin graft cover over the radial forearm flap[9] donor site often results in graft breakdown over the flexor carpi radialis, subsequently requiring debridement of the tendon to allow healing by secondary intention.[10–16] This can lead to scar tethering and reduced power during wrist flexion. The use of other dermal substitutes has been reported in such wounds to improve outcomes.[17–20]

This study therefore reports on the first human long-term implantation of the biodegradable temporizing matrix (BTM) in 10 patients with free-flap donor sites. Quantitative, qualitative, and photographic data have been collected from wound creation, implantation, through the integration phase to split-skin grafting and through to scar outcomes at 1 year postimplantation. Our reflection on the handling and outcomes of this study has led to further optimization of the BTM for use in a subsequent cohort of 10 patients.

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