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In this article, Victoria Bristow (Cambridge, UK) discusses the NovoSorb Biodegradable Temporising Matrix (BTM) from PolyNovo and shares a case report demonstrating its use in the treatment of a patient with chronic limb-threatening ischaemia (CLTI) and extensive tissue loss. According to Bristow, “BTM provides a useful adjunct to aid wound healing in revascularised CLTI patients with extensive tissue loss, especially when exposed tendons and bones are present”.
NovoSorb BTM has been studied reasonably extensively in patients with burns, necrotising fasciitis and, more recently, in diabetic foot disease. However, there is a paucity of literature in the setting of tissue loss secondary to CLTI.
Dermal templates are indicated for the use of deep dermal or full thickness wounds. The gold standard treatment for these wounds is autologous split thickness skin grafting, which is not often possible due to contraindications for use of active bleeding and/or infection, known malignancy, or exposed underlying structures including bone, tendon, nerves, or vessels.1
BTM is a dermal matrix that is commonly used in extensive and hardto- heal wounds. The dermal matrix adjunct can cover important structures to maintain structural function such as vessels, joint capsules, bone, and tendons. This is important in vascular patients, enabling them to continue to be mobile and avoid major limb amputation, which could lead to a longer hospital admission and, for some, loss of independent living. The matrix is initially placed over the defect to create a neodermis.
This is where dermal grafts come into their own. Another positive of using dermal matrix grafts is that they can be applied in both acute and chronic stages of wound healing.
Novosorb BTM is a completely synthetic matrix that is made of 2mm polyurethane bilayer dermal template, which consists of both a porous matrix and a sealing membrane. A benefit of BTM being synthetic allows for the graft to be placed without worrying about immunity rejection or disease transmission. It is also inexpensive to manufacture and can be placed in those with cultural objections to using animalderived products.2
Most recently, an Australian study by Guerriero et al looked at barriers to wound healing in the neuropathic and neuro-ischaemic diabetic foot cohort using a biodegradable synthetic matrix.3 This study was a single-centre, prospective observational study, the aim of the which was to look at complete wound healing as well as amputation outcomes. The inclusion criteria within the study included anyone who had a diabetic foot ulcer treated with BTM between December 2019 and October 2021. All the participants recruited had to have a confirmed diagnosis of diabetes with a HBA1c of 48mmols or more, were over 18 years old, had a wound distal to the malleolus and were treated with BTM. They used the wound, ischaemia, and foot infection (WIFI) score to assess amputation risk. In total they applied BTM to 22 patients with 23 wounds. Complete wound healing—which they defined as 100% epithelialisation with no exudate—was seen in 15 patients; three wounds failed to go on to fully heal; two patients required major amputations and three patients underwent minor amputations. All patients who had BTM applied underwent revascularisation and surgical debridement. However, no objective level of perfusion was documented. Within this study they placed all patients in negative pressure wound therapy (NPWT) post BTM application for 14 days at a reduced level of 75mmhg.
Case report
Our first case using BTM was a 62-yearold male who presented with CLTI and extensive tissue loss involving the dorsum of the foot, multiple toes, and the calf. On presentation to the emergency department, he had extensive necrosis and lower limb ischaemia with only a femoral pulse palpable on the right leg (Figure 1). On discussion with the patient and his daughter, it was revealed that he had presented three times at a local district hospital and was misdiagnosed.
He was admitted to the vascular ward for further investigations and revascularisation by the means of a leftto- right femoral crossover graft using a polytetrafluoroethylene (PTFE) graft and his inflow was improved with an iliac angioplasty.
Debridement of the foot was required including amputation of the second to fifth toes. BTM was applied to the dorsum of the foot and the calf. Delamination was carried out at eight weeks. His wounds were fully healed at 24 weeks.
Discussions then began with the team whether his leg was salvageable due to the large area of tissue loss. It was decided that the patient would be discharged home to continue to allow the leg to demarcate. He was reviewed regularly in the outpatient clinic. Sharp debridement was carried out but there was concern that this eschar was covering and protecting important structures including tendons, bone, and blood vessels.
A consultant colleague and I had recently attended a talk showcasing BTM in burns patients from Australia. These case studies had large areas of tissue loss and it was felt this product would be suitable to the vascular patient group.
The patient was counselled as to this being the first time this product was being used by our centre but was aware due to the large amount of tissue coverage needed the only other option would have been a below-knee amputation and the patient was keen to try and salvage his limb in the first instance.
The matrix was applied in theatre under general anaesthesia in full sterile conditions. With the BTM the wound needs to be able to bleed through the matrix to encourage angiogenesis and create a neodermis. It is secured using staples and negative pressure wound therapy (NPWT) is placed on top this was used for protection and as well as exudate control.
Interestingly, not all studies looking at dermal templates recommend application of NPWT postsurgical application of BTM. NPWT has been used in varying wounds in both acute and hard-to-heal wounds since the 1990s. However, an interesting recent article by Austin in the Journal of Wound Care looked at a case series in which patients receiving NPWT in conjunction with BTM increases the rate of integration.4
The case series was conducted using a retrospective approach of reviewing the clinical records of 28 patients. A total of 23 patients had successful integration, 16 of the patients received both BTM and NWPT and 12 patients received BTM alone. The NWPT group had a P score of (0.046) making it statistically significant. Limitations of this study include that it was non-blinded and a non-randomised chart review. It was also a very small sample size and only from one centre.
In our case, dressings were done weekly by the specialist nurse for seven weeks, wound photos were taken at every visit and the NPWT was replaced on both the forefoot and posterior calf. Contraction of the wound was visible but very limited.
After seven weeks the graft was delaminated: the staples were removed, and the sealing membrane was peeled back. Once removed some slough was present but there was granulation tissue present with islands of epithelisation occurring.
Simple dressings were then applied from this point onwards with silver as the primary dressing, as per the instructions for use from Polynovo. This was carried out by district nurses until week 24 at which the wound had fully healed (Figures 2a and 2b).
To conclude, we have found that BTM provides a useful adjunct to aid wound healing in revascularised CLTI patients with extensive tissue loss, especially when exposed tendons and bones are present. Furthermore, the patient in this case experienced minimal pain throughout the duration of treatment. We have also found that NPWT adds specific benefits of removing excess exudate, promoting healing, and accelerating angiogenesis.
References
- Braza M and Fahrenkopf M. Split skin grafts. Florida: Treasure Island. 2023.
- Shahroki S, Arno A and Jeschke M. The use of dermal substitutes in burn surgery: acute phase. Wound Healing Society. 2014;22:14–22.
- Guerriero F, Clark R, Miller M and Delaney C. Over coming barriers to wound healing in a neuropathic and neuro-ischaemic diabetic foot cohort using a novel bilayer biodegradable synthetic matrix. Biomedicines. 2023;11(3):721.
- Austin C. Biodegradable temporising matrix: use of negative pressure wound therapy shows a significantly higher success rate. Journal of Wound Care. 2023;3(32):159–166.
Victoria Bristow is a vascular specialist nurse at Cambridge University Hospitals in Cambridge, UK.
Consent was gained from the patient to share his photos in this case study.
