How to Approach Healing the Diabetic Foot: The Synthetic Dermal Matrix Solution

May - June 2022

How to Approach Healing the Diabetic

Foot: The Synthetic Dermal Matrix Solution

Editorial Summary

Soft tissue reconstruction of the diabetic foot is a challenge for clinicians. Primary closure is not an option and healing with secondary intention is not always optimal.

Other options include local flap closure, skin grafts, pedicled flaps and free tissue transfer.

This article provides an overview and comparison of biological and synthetic dermal matrices, and a summary of the advantages of synthetic dermal matrices, supported by two case studies.

There is a diabetic foot ulceration epidemic occurring, with up to 25% of diabetics in the USA going on to develop a foot ulcer in their life. The total cost of diabetes in the USA is $176 billion, with an estimated annual cost for diabetic foot ulceration of $15 billion2

Similarly, in the UK alone there was an increase from 176,000 to 342,000 patients with diabetic foot ulceration3. This is a staggering 95% rise from 2012/ 2013 to 2017/ 18, which equates to a 20% increase in diabetic foot ulcer (DFU) patients each year due to a combination of new ulcerations and non-healing wounds.

Historical Approach vs Innovation

Historically, dressings result in macrounorganised wounds, they must be discarded once changed, and require multiple dressing changes, can cause thermal disruption, and need to be altered depending on the wound type.

Dermal matrices aid the production of micro-

organised wounds. These types of devices require only one application and only the sealing membrane must be discarded. During integration of the matrix, the wound is temporised, and fenestration allows for management of wound exudate and optimal wound healing.

When comparing biological and synthetic matrices, synthetic matrices have clear advantages.

Biological Matrices4

• Biological matrices consist of collagen, which can act as an active food source for bacteria.

• They have a low reliability against infection.

• They are expensive.

• There are ethical and religious considerations.

Synthetic Matrices4

Synthetic matrices are produced from inert materials.

They are more cost-effective to manufacture.

There are few barriers to their use.

• They are robust in the presence of infections.

Mr Ross Robinson

Podiatrist & Clinical Product Specialist, PolyNovo®

London, United Kingdom

Diabetic foot disease is now considered the tenth leading cause of global disease burden and disability1. Simple dressings, advanced dressings, Negative Pressure Wound Therapy (NPWT), and biological matrices have all been utilized effectively in the past and continue to be widely used. This article gives a concise overview of the advantages and application of a synthetic dermal matrix in the diabetic foot.

Figure 1:

Patient at 7 months

Synthetic Matrix Overview

Uniform growth of tissue throughout

Patient at 8 months

Macrophages have eaten through smooth wall of polymer

Patient at 12 months

BTM

NovoSorb® BTM is a fully synthetic device with all components made of polyurethane. It has a sealing membrane that physiologically closes the wound, providing a physical barrier from external contamination. It has fenestrations which allows the drainage of excess fluid that could interfere with integration or become a nidus for infection.

NovoSorb® BTM has an open cell porous matrix. Neovascularisation occurs in this matrix through the interconnected chambers, allowing infiltration with cells related to wound repair.

Corners are softening and rounding

Figure 1 shows a human punch biopsy sample of integrated NovoSorb® BTM. Over time, degradation occurs, and the polymer gradually disappears. By 18 months no residual polymer was seen5.

Some of the benefits of temporising wounds include the prevention of moisture loss, providing a barrier to infection, and physiologically closing the wound until sealing membrane removal and definitive closure performed.

Foreign Body Response (FBR) almost completely gone

Fat cells (adipocytes)

Note dissipation of giant cells (left arrow). Few remnants continue to degrade (right arrow).

Patient at 18 months

BTM is full hydrolyzed and a fully vascularized neo-dermis remains. Corresponding disappearance of macrophages.

The Matrix

The NovoSorb® BTM matrix has a low density and is approximately 94.2% porous. It has interconnected pores and has multiple interconnections per ‘chamber’. NovoSorb® BTM prevents long collagen links forming, allows free movement of key cells and provides scaffolding for the extracellular matrix (ECM).

The 2mm-thick open cell matrix converts a large complex wound into many tiny ones that the body can heal in an organized manner. Made from a polyurethane polymer, it does not contain any animal collagen, so is not a food source for bacteria, and can often be retained in

Surgical Approach to Healing the Diabetic Foot, Using a Synthetic Dermal Matrix

“Some of the benefits of temporising wounds include the prevention of moisture loss, providing a barrier to infection, and physiologically closing the wound until sealing membrane removal and definitive closure performed.”

place if an infection occurs.

NovoSorb® BTM should be applied to a fully debrided wound, trimmed to shape and secured with staples or sutures. Haemoserous fluid from the wound migrates into the matrix, delivering white blood cells, including macrophages and neutrophils, which ‘jump start’ the immune response and stimulate new blood vessel formation. Fibroblasts deposit collagen, building the extracellular matrix which will provide strength and structure for the new tissue.

When the matrix has fully integrated, the sealing membrane can be removed to expose the robust neodermis, which is ready for definitive closure. NovoSorb® BTM progressively biodegrades and is absorbed over time. This material supports the reconstruction of a diverse range of complex wounds, even over exposed bones and tendons, to improve cosmetic and functional outcomes when compared with skin grafting alone.

Case Studies

In this case, NovoSorb® BTM was applied over extensor tendons which were extensively exposed after a traumatic degloving injury6

Figure 2 shows the wound post initial debridement.

Figure 3 shows progress at nine weeks post BTM application. At this stage, the sealing membrane has been delaminated to reveal a robust, well vascularised neodermis ready for grafting.

An ultrasound showed that there was no feature of peritendon inflammation, and that the tendon can be seen to move through the deep and superficial tissues without impediment. The fibrillary structure of the tendon is intact and normal6.

The results nine months after BTM are very satisfactory. The contour allows this patient to wear normal footwear and there is no fixed extension of the joints. Additionally, despite the lack of paratenon prior to reconstruction, the tendons functionally glide under the repair, allowing good toe movement.

In this next case, a 73-year-old Caucasian lady with comorbidities, including non-insulindependent diabetes mellitus, hypertension, and anaemia), developed a wound on her foot from minor trauma. Due to her diabetes and comorbidities, the wound failed to heal and developed into an infected diabetic foot ulcer. Serial debridement was performed, and she was left with a large defect on the dorsum of her foot. NovoSorb® BTM was applied, dressed, and topical negative pressure wound therapy (NPWT) was applied. The patient was discharged after 1 week to a care facility7 (Figure 4).

Pre-operative

One week after NovoSorb® BTM application

Surgical Approach to Healing the Diabetic Foot, Using a Synthetic Dermal Matrix

“NovoSorb® BTM should be applied to a fully debrided wound, trimmed to shape and secured with staples or sutures.”

Figure 2:

Figure 3: Figure 4:

References

1. Lazzarini PA, Pacella RE, Armstrong DG, van Netten JJ. Diabetes-related lower-extrem ity complications are a leading cause of the global burden of disability. Diabet Med. 2018 May 23. doi: 10.1111/dme.13680. Epub ahead of print. PMID: 29791033.

2. Diabetic Foot: Facts and Figures [Internet]. https://diabeticfootonline.com; [cited 20 May 2022]. Available from: https://tinyurl.com/9bx55hxp

3. Guest JF, Fuller GW, Vowden P. Cohort study evaluating the burden of wounds to the UK’s National Health Service in 2017/2018: update from 2012/2013. BMJ Open. 2020 Dec 22;10(12):e045253. doi: 10.1136/bmjopen-2020-045253. PMID: 33371051; PMCID: PMC7757484.

4. Greenwood JE, Dearman BL. Comparison of a sealed, polymer foam biodegradable tem porising matrix against Integra(R) dermal regeneration template in a porcine wound model. J Burn Care Res. 2012; 33:163-73. doi: 10.1097/BCR.0b013e318233fac1. PMID: 22002205

5. Wagstaff MJD, Schmitt B, Coghlan P, Finkemeyer JP, Caplash Y, Greenwood JE. A biodegradable polyurethane dermal matrix in reconstruction of free flap donor sites: A pilot study. Eplasty. 2015; 15:102–18. https://pubmed.ncbi.nlm.nih.gov/25987938/. PMID: 25987938 PMCID: PMC4412164

6. Damkat-Thomas L, Greenwood JE, Wagstaff MJD. A Synthetic Biodegradable Temporis ing Matrix in Degloving Lower Extremity Trauma Reconstruction: A Case Report. Plast Reconstr Surg Glob Open. 2019 Apr 2;7(4):e2110. doi: 10.1097/GOX.0000000000002110. PMID: 31321161; PMCID: PMC6554176.

7. PolyNovo MK-019 V2.0. Case Report - Infected Diabetic Foot Ulcer. On file.

Problems with the negative pressure wound therapy were encountered. The patient was readmitted with clinical evidence of infection, that was systemically treated. The NovoSorb® BTM was able to be retained despite the infection. Removal of the sealing membrane was performed at 4.5 weeks, a split-thickness skin graft applied, and the patient went on to heal uneventfully.

Globally, millions of diabetic patients with DFU face the imminent prospect of lower limb amputation or death. Synthetic matrices offer an alternate option for reconstruction. Composed of inert materials, robust and cheap to produce, they offer significant advantages in this complex reconstructive challenge.

BTM delaminated, ready to graft Four months after skin graft