Acellular Porcine Urinary Bladder Matrix for the Treatment of an Avulsive Scalp Wound in Irradiated Tissue on a Chronically Immunocompromised Patient: A Case Presentation

Biological materials composed of extracellular matrix (ECM) harvested from a wide variety of tissues and organs are widely used as viable alternative options for tissue reconstruction.  A new product, MatriStem by ACell, has shown promise in regards to regeneration of healthy functional tissue as opposed to scar formation.  MatriStem is comprised of an acellular extracellular matrix scaffold comprised of porcine urinary bladder matrix (UBM).  Its unique bimodal surface characteristics consist of an intact basement membrane and an organized connective tissue bed comprised of urinary bladder lamina propia.  The basement membrane is conducive to epithelial and endothelial cell attachment, proliferation and differentiation, while the lamina propia allows for integration of the product into the wound bed and host connective tissues, and supports vascular ingrowth.  In addition, the processing of the MatriStem product allows for retention of multiple growth factors including vascular endothelial growth factor (VEGF), transforming growth factor beta (TGFβ), platelet derived growth factor (PDGF), bone morphogenic protein 4 (BMP4), and basic fibroblast growth factor (BFGF) to assist in regeneration and healing.   Recent studies have demonstrated antimicrobial properties of UBM-ECM to both S. aureus and E. colias well as a predominance of macrophage phenotype 2 (M2) in the early postoperative period which has been shown to correlate with less scar formation and more healthy functional tissue regeneration with increased chemotactic activity. 

The case being presented is a 62 year old Caucasian male with a 3.0 x 3.5cm avulsive scalp wound down to cranium. The avulsive wound was located at the site of a previous squamous cell carcinoma excised using Mohs surgery coupled with radiation therapy. The patient also was on chronic immunosuppressive therapy following a right kidney transplant. Initially, the wound was managed with wet-to-dry dressing changes twice daily and antibacterial ointment.  Failure of progressive improvement during the follow up period warranted surgical options such as a rotational flap or the use of a biological material.  The patient elected for the biological material.  He was brought to the operating room where the wound was debrided until healthy bleeding soft tissue margins were evident. Exposed cranial bone was also shaved using a large round bur until bleeding points were evident.  The result of the debridement procedure was a 7 x 6cm defect.  The defect was then filled with 500mg of MatriStem powder.  The MatriStem wound sheet (7 x 10cm) was trimmed and secured in place on the top of the defect using skin staples. A bolster dressing was then applied on top of the reconstructed defect area.  The patient was followed up weekly as an outpatient where MatriStem powder and wound sheets were reapplied as necessary until complete healing and re-epithelialization occurred. 

In the presented case, the MatriStem product allowed for successful reconstruction of an avulsive scalp soft tissue defect. It avoided the comorbidities associated with a large rotational flap and created a well healed, healthy tissue bed rather than scar tissue.  While more research is needed to determine all of its applications in the scope of oral and maxillofacial surgery, the product is showing promising results in enhancement of wound healing in the presence of both local and systemic hindering factors (radiotherapy/immunosupression).

1 – Brennan EP, Reing J, Badylak SF, et al. Antibacterial activity within degradation products of biological scaffolds composed of extracellular matrix. Tissue Engineering 12 (10), 2006; 2949-2955.
2 – Brown BN, Londono R, Badylak SF, et al. Macrophage phenotype as a predictor of constructive remodeling following the implantation of biologically derived surgical mesh materials. Acta Biomaterialia 8, 2012; 978-987.