Ovine forestomach matrix, or OFM, belongs to a family of biomaterials known as extracellular matrix bioscaffolds. The material is processed from the layered tissue of the sheep’s forestomach, preserving much of its natural structural architecture, including collagen fibers and associated proteins that mammalian tissues recognize as familiar building instructions. When surgeons suture or lay an OFM device into a wound, it does not simply patch the defect. Instead, it acts as a temporary biological scaffold that invites the patient’s own cells to migrate in, form new blood vessels, and progressively rebuild missing or damaged tissue. Over weeks to months, the body remodels and ultimately replaces the scaffold with functional vascularized tissue. This regenerative mechanism is what distinguishes bioscaffolds from purely inert synthetic implants, and it is also why their safety profile, particularly regarding infection and immune reactions, matters so much to reconstructive surgeons.

The MASTRR Registry was deliberately designed to capture the messiness of real clinical practice. It is a prospective, multicenter, single-arm, open-label observational study operating under the IDEAL framework, a structured pathway for evaluating surgical and device innovations that explicitly recommends observational registries at both the exploratory and long-term surveillance stages. Rather than enrolling only the healthiest patients with the cleanest wounds, the registry applied broad inclusion criteria with minimal exclusions, enrolling patients across trauma, colorectal, burn, and limb salvage specialties. The study received centralized institutional review board oversight, is registered with ClinicalTrials.gov under identifier NCT05243966, and is ultimately approved to enroll up to 800 subjects, making it, according to the investigators, the largest registry-based study of its kind for bioscaffolds in soft tissue reconstruction.

The patient population captured in this interim analysis was, by any measure, medically formidable. Most subjects were middle-aged men, with a median age of 54 years, and more than half carried an American Society of Anesthesiologists physical status classification of III, indicating severe systemic disease that limits daily function. Nearly 36 percent had type 2 diabetes, about 30 percent had vascular disease, and almost a quarter used nicotine products, all factors known to impair wound healing. The defects themselves were equally challenging: nearly 60 percent were chronic, having persisted for more than a month, and roughly 90 percent were classified as clean-contaminated or contaminated under the Centers for Disease Control and Prevention wound classification system. Exposed bone, tendon, or viscera appeared in 11.4 percent of defects, and confirmed osteomyelitis, a serious infection of bone, was present in 15 percent. The median defect area for dermal reconstructions was 24 square centimeters, with some reaching far larger.

The range of conditions treated underscores the versatility the registry was built to probe. Diabetic foot ulcers accounted for 22.6 percent of defects, many of them deep Wagner grade 2 or 3 wounds, followed by traumatic injuries at 16.5 percent, ostomy takedown reconstructions at 11.2 percent, pilonidal sinus disease at 10.8 percent, and pressure injuries at 9.7 percent, most of the latter being stage 4 wounds involving muscle and exposed structures. Surgeons deployed the OFM devices in three main ways: topically for dermal reconstruction in 65.2 percent of cases, as an implant to reinforce soft tissue flaps or fill dead space in about a quarter of cases, and to augment closure of fistulae, including perianal, enterocutaneous, and rectovaginal types, in roughly 10 percent. Notably, a median of just one product application was needed per defect, and negative pressure wound therapy was used adjunctively in fewer than a quarter of procedures.

The safety results are the heart of the analysis. Fifty-nine adverse events were reported across the 411 subjects during a median follow-up of 27.1 weeks, meaning 12.2 percent of patients experienced one or more events, a figure that falls to 8 percent when only events involving the treated defect are considered. Each event was graded for severity using the Common Terminology Criteria for Adverse Events framework and assessed for causality under ISO 14155 guidance, the international standard for clinical investigation of medical devices. The verdict was striking: 79.9 percent of events were deemed unrelated to the device and 18.6 percent unlikely related, with no events classified as definitely or possibly related and a single probable case. That lone event involved redness, pain, and swelling on a lower extremity defect suggestive of an allergic reaction, prompting partial removal of the graft; the patient was treated with antihistamines, went on to receive a split-thickness skin graft, and completed wound closure while remaining in the study.

Events occurring at the index defect itself were infrequent and mostly minor. Superficial infections occurred at 2.9 percent of subjects, wound dehiscence at 3.2 percent, and deep tissue infection at just 0.7 percent, with only three deep infections reported across the entire cohort and none requiring device extraction. Pilonidal sinus reconstruction generated the highest share of defect-related events, largely dehiscence of the primary closure, while seven of the 33 index defect events required reoperation, most commonly simple incision and drainage. Eight deaths were reported during the study, but clinical review attributed all of them to progression of severe pre-existing cardiopulmonary, renal, or malignant disease, and none were considered related to the index procedure or the OFM treatment. The remaining events were systemic or incidental, including pneumonia, sepsis, and thrombophlebitis, reflecting the frailty of the population rather than the device.

Perhaps the most provocative comparison in the paper concerns infection. A long-running argument in biomaterials holds that synthetic scaffolds should resist infection better than tissue-derived biologics, yet the registry data suggest otherwise. A recent meta-analysis of a polyurethane-based bioscaffold in complex reconstruction, pooling 34 studies and 208 subjects, reported an overall complication rate of 27.9 percent and an infection rate of 25.8 percent. Another comparative meta-analysis found postoperative infection rates of 26.24 percent for polyurethane matrices and 18.79 percent for a crosslinked collagen and chondroitin sulfate scaffold in burns, while a third reported a generalized infection incidence of 16.9 percent for the latter material. Against those figures, the 0.7 percent deep infection rate and 2.9 percent superficial infection rate observed with OFM in a heavily contaminated, comorbid population challenge the assumption that synthetics hold an infection advantage, and the authors of those earlier meta-analyses had themselves urged clinicians to weigh risks carefully before adopting those products.

The registry framework has also proven productive beyond safety surveillance, generating a series of indication-specific subgroup analyses from a common prospective data collection platform. These include complex lower extremity reconstruction, where a median of 30 days was needed to achieve complete granulation tissue coverage; traumatic defects across four level 1 trauma centers, where vascularized tissue coverage was achieved in a median of 22.5 days; deep partial-thickness burns, where a single OFM application produced a median 14-day healing time with minimal pain and favorable scar scores; and late-stage pressure injuries, where approximately 60 percent wound area reduction was achieved without postoperative complications. A comparative study of pilonidal sinus reconstruction found that adding an OFM graft under a fasciocutaneous advancement flap significantly reduced surgical dehiscence, lowered treatment costs, and improved patient quality of life relative to a matched cohort reconstructed without the graft.

The investigators are careful to acknowledge the limits of their evidence. The registry lacks a contemporaneous control group, so direct comparative claims about relative safety cannot be drawn; the deliberately heterogeneous population, while ideal for an IDEAL stage 2b evaluation, may obscure indication-specific differences; the interim analysis carries a median follow-up of only about 27 weeks, leaving late complications and long-term durability to be characterized; and adverse event categorization relied on investigator judgment. Even so, as one of the largest prospective evaluations of a bioscaffold in soft tissue reconstruction reported to date, the interim MASTRR data make a compelling case that a scaffold spun from an abundant food-industry byproduct can be deployed safely in some of the most hostile wounds surgery has to offer, and that registry-based real-world evidence deserves a permanent seat alongside randomized trials in judging emerging medical devices.

Subject of Research: Real-world safety of ovine forestomach matrix bioscaffolds in complex soft tissue reconstruction

Article Title: Safety of Ovine Forestomach Matrix Across 474 Soft Tissue Defects: Interim Results from the Prospective Multicenter MASTRR Registry

Article References: Short, T., Lawlor, J., Martyka, P., Wolf, J. H., Felton, J. M., Smith, A. A., Nasseri, Y. Y., Barnajian, M., Vassy, W. M., Cormican, M., Kumar, P., Choi, J. J., Lau, L., Loftus, J. H., Bernal, N. P., Butts, C. A., Dillingham, C. S., Leneweaver, K. J., Simon, J., … May, B. C. H. (2026). Safety of Ovine Forestomach Matrix Across 474 Soft Tissue Defects: Interim Results from the Prospective Multicenter MASTRR Registry. Advances in Therapy. https://doi.org/10.1007/s12325-026-03768-0

Image Credits: AI Generated

DOI: 10.1007/s12325-026-03768-0

Keywords: ovine forestomach matrix, bioscaffold, soft tissue reconstruction, MASTRR Registry, adverse events, real-world evidence, wound healing, diabetic foot ulcers, trauma surgery, burns, pilonidal sinus, IDEAL framework