Limb Salvage After Necrotizing Fasciitis Caused by Prevotella Bivia

Necrotizing fasciitis involves the fascia and subcutaneous tissues, leading to severe tissue destruction, systemic toxicity, and often requires surgical debridement or amputation.^1,2 Prompt diagnosis and treatment with broad-spectrum antibiotics and surgical intervention are critical to improving outcomes.³

Prevotella bivia is an anaerobic, gram-negative bacterium commonly found in the female genital tract and its most often association is with pelvic infections. There are, however, documented cases where P. bivia, either alone or as part of polymicrobial infection, has contributed to necrotizing fasciitis, particularly in immunocompromised patients or in infections originating near the perineal or lower extremity areas.⁴ P. bivia infections tend to be polymicrobial and may be recognized via blood cultures, wound cultures, or tissue biopsy.^5-9 Soft tissue emphysema may be present; however, it is less common in anaerobic infections.⁶ Antibiotic treatment for P. bivia generally involves metronidazole or amoxicillin-clavulanate.⁸

Strattice^™ Reconstructive Tissue Matrix (Allergan Aesthetics) is an acellular dermal matrix (ADM) derived from porcine dermis.^10-12 It is processed to remove cells while preserving the extracellular matrix, which provides a structural scaffold to support tissue regeneration and host cell integration.^10-12 This matrix is commonly used in reconstructive surgeries, such as abdominal wall repair, breast reconstruction, and hernia repair, particularly when there is native tissue compromise or infection risk. It maintains better biocompatibility and flexibility, which can support better tissue incorporation and potentially reduce inflammatory response compared to crosslinked grafts. It is also considered more resistant to infection than systemic meshes, making it ideal for contaminated surgical fields.^10-12 

When one discusses the plantar soft tissue scaffold, this includes the thick, fibrous structures on the bottom of the foot, particularly the plantar fascia, fat pad, dermis, and associated musculature. These tissues are essential for shock absorption, weight distribution, and pressure protection during gait. 

In a transmetatarsal amputation (TMA), there is removal of the forefoot across the metatarsal shafts. While this aims to preserve as much limb length as possible, it can disrupt the plantar pedal architecture. Debridement of necrotic tissue further can also complicate the surgical outcome, depending on tissue viability or lack thereof. 

This case study aims to highlight a rare case of necrotizing fasciitis stemming from a foot ulceration infected with Prevotella bivia and our use of a meshed porcine dermal matrix xenograft to recreation of the plantar soft tissue scaffold after limb salvage surgery to achieve healing and restore limb function.

Key Details of the Case Presentation

We present the case of a 64-year-old male patient with past medical history of type 2 diabetes mellitus with peripheral neuropathy, peripheral vascular disease, chronic kidney disease, and prior contralateral Charcot neuroarthropathy. The patient presented to the emergency department with a necrotic, dusky right second digit, ascending cellulitis of the right anterior leg, abscesses in multiple right foot compartments, and a wound to his distal right second toe which had appeared within the week prior. His regular podiatrist in the community recommended and performed an incision and drainage of that digit and started the patient on oral antibiotics. At his postoperative follow-up appointment 2 days later, the community surgeon recommended he go directly to the VA emergency department with the expectation of amputation.

After chart review and during his initial bedside evaluation, our team obtained a thorough history. We then performed a lower extremity focused exam, which included vascular, dermatologic, neurologic, and musculoskeletal work-ups. Ordered lab work and imaging included radiographs and computed tomography (CT) of the lower extremity, complete blood count, basic metabolic panel, erythrocyte sedimentation rate, and C-reactive protein (CRP). Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) Score was 10, indicating the patient was high risk for necrotizing fasciitis. An ankle-brachial index obtained a week prior demonstrated a toe pressure of 78 mmHg, suggestive of peripheral arterial disease, but supporting the presence of adequate flow for healing. We also obtained a wound culture and sent that specimen for culture and sensitivity testing. 

Physical exam demonstrated palpable pedal pulses, diminished protective sensation, and no gross deformity of the right foot, the left foot showed bony prominences and midfoot collapse secondary to a history of Charcot arthropathy. The right second digit demonstrated a distal ulceration with necrosis and duskiness with ascending cellulitis to the mid anterior leg. On imaging, cortical erosions were appreciated to the distal second phalanx with extensive soft tissue edema and emphysema throughout the second toe. Lab results showed an elevated white blood cell count, an elevated CRP, low serum sodium, and elevated blood urea nitrogen (BUN) and creatinine.

Pertinent Points on the Treatment Course

The patient was admitted for necrotizing fasciitis with gas gangrene. We performed a right second toe amputation for source control at the bedside in the emergency department with local anesthetic before transfer to the floor. A consultation with vascular surgery resulted in a recommendation of below-knee amputation, which the patient refused. The patient subsequently went into septic shock and care continued in the intensive care unit. Infectious disease was also consulted and managed the patient’s antibiosis the for the entirety of his care.

Over the following days the patient returned to the operating room for multiple toe and metatarsal amputations with serial debridement, ultimately leading to a TMA. The patient was deemed medically stabilized prior to each OR encounter. Each time we thought we’d achieved source control, including after the initial toe amputation, the infection would return necessitating a wider and more proximal amputation. Of note, the patient had extensive plantar soft tissue necrosis from his infection, resulting in significant challenges to ultimate healing and limb preservation. One week later, a revisional transmetatarsal amputation took place for removal of all nonviable soft tissue and bone. Extensive damage was noted to the skin, tendons, muscles, and other soft tissues. The patient again declined to consent for a below-knee amputation. As a result, then, the remaining transmetatarsal stump had minimal plantar and intermetatarsal soft tissues and inadequate skin available for closure.

During the TMA revision, we wrapped a single-layer thickness of meshed pericardium allograft over the distal metatarsal shafts. We also sutured together 3 layers of porcine dermal xenograft and attached it to the soft tissues surrounding the metatarsal bases for plantar padding along the metatarsal remnants. We then meshed a single layer of the porcine dermal graft and placed it within the open wound to cover the exposed area, suturing it to the deep aspect of the skin flaps to act as a basement layer. Two retention-type sutures helped to approximate the skin flaps to secure and protect the newly placed grafts. We initiated negative pressure wound therapy (NPWT) continued this approach over the following 2 months. 

After significant granulation of the wound bed, the patient underwent a split thickness skin graft (STSG). Post-grafting, the patient began wearing a prior diabetic shoe with a built-in metatarsal pad, which led to failure of the central plantar portion of the STSG. He was placed back onto an offloading shoe and local wound care was continued. 

Epithelialization of the central plantar portion of the TMA stump did not occur over the course of a six-month period with local wound care efforts. After full evaluation of possible etiologies for this failure to progress, we scheduled the patient for an Achilles tendon lengthening to address an adductovarus deformity that we felt was leading to increased pressure along the distal stump, as well as a second STSG.

Observations and Lessons Learned

The infection in this case originated from a seemingly minor foot ulcer and quickly progressed, necessitating a transmetatarsal amputation. The infection’s severity, compounded by the patient’s diabetes, peripheral vascular disease, and septic shock, left the surgical team with extensive plantar soft tissue loss, presenting a major reconstructive challenge. The authors highlight the use of a multi-layered meshed porcine dermal matrix xenograft to recreate the plantar soft tissue scaffold, a critical component for foot function and protection post-TMA. We feel that this approach demonstrates the potential of biologic matrices to support tissue regeneration and avoid more proximal amputations, even in severely compromised patients.

Longitudinal follow-up showed initial granulation, but epithelialization remained incomplete after the first autograft in part due to mechanical stress from improper footwear. This underscores the importance of postoperative care and offloading strategies. Ultimately, a second STSG and Achilles tendon lengthening achieved full wound closure and functional preservation at one year.

The case reinforces the biomechanical importance of the plantar soft tissue scaffold, and the versatility of biologic grafts in complex, contaminated wounds. It also highlights the interplay between surgical technique, patient adherence to recommendations, and biomechanical management in long-term limb salvage outcomes.

It is important to note that this case was performed at the Southern Arizona Veteran Affairs Health Care System; therefore, cost and reimbursement were not factors in determining treatment. All wound care products used all reimbursable through Medicare and private insurance and have their own designated HCPCS codes. The cost to benefit ratio would need to be assessed on an individual provider and patient basis. All pricing of the wound care products used in this case are available to the public through the Department of Veteran Affairs Federal Supply Schedule. Providers should consult their specific Local Coverage Determinations and insurance coverage policies for coverage information that applies to their patients. 

Conclusion

When presented with this case, our goals of therapy were to prevent a more proximal amputation, eradicate the infection, minimize patient discomfort, restore function of the limb, and achieve complete wound closure. The wound did in fact progress to complete closure after a year of advanced wound care, including xenografting and autografting. Our approach allowed us to avoid a more proximal amputation and to restore full function to the patient’s limb. 

Dr. Curbo is Chief Podiatry Resident in the Department of Veteran Affairs at Southern Arizona Veteran Affairs Healthcare System in Tucson, AZ.

Dr. Evensen and Dr. Jolley are Podiatrists in the Department of Veteran Affairs at Southern Arizona Veteran Affairs Healthcare System in Tucson, AZ.

The authors of this article declare no conflict of interest. The companies involved had no role in the design of the study; in the collection, analyses, or interpretation of date; in the writing of the manuscript, or in the decision to publish the results

This material is based upon work supported by the Department of Veterans Affairs, Veterans Health Administration, and Office of Research and Development. The authors gratefully acknowledge the Southern Arizona VA Health Care System which provided facilities and materials for this research. 

References

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