Case Series of Reconstruction Applying NovoSorb Biodegradable Temporising Matrix: Preliminary Practice and Findings in the United Kingdom

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Biodegradable temporizing matrix (BTM, also known as BTM NovoSorb) is an artificial synthetic polymer that does not contain any biological materials.¹ It was developed by PolyNovo Biomaterials Pty Ltd in Australia and first used on humans in a 2014 pilot burn trial to address the demand for a synthetic dermal matrix for wound reconstruction surgery.^2,3 It comprises 2 layers: an outer layer acting as a sealing membrane to restrict moisture loss and protect against foreign pathogens, and an inner, adhesive bonding layer that bridges between the sealing membrane and foam. The NovoSorb foam is a 2-mm-thick, open-cell matrix that functions as dermal scaffolding, facilitating circulation and reconstruction.³ It has been granted approval for use in the reconstruction of complex wounds in multiple countries, including the United Kingdom.⁴

Complex wounds are generally characterized by the exposure of tendon and bone, as well as the failure of reconstructive procedures such as skin grafts. Even patients with multiple comorbidities can undergo skin grafting for complex reconstructions, typically 4 weeks after applying BTM. This approach can lead to sensory function regeneration in the early stage, enhancing its effectiveness and robustness.⁵ An advantage of applying BTM in surgical practice is the reduction in shrinking, granulation, and associated myofibroblast-mediated contraction arising from split-thickness skin grafts.⁶ It is also considered to be a treatment option resistant to infections because of the absence of sensitizing proteins, in addition to improved contour and pliability.⁷ The variable mechanical properties, structural versatility, and biocompatibility offer space to accommodate various shapes and depths of wounds, for which BTM is cut to size and shaped with scissors and positioned with surgical staples or sutures.⁸ The soft matrix provides robust, reliable, and superior cosmetic results for patients with full-thickness burns.⁹ Fibroblasts are embedded in the matrix, and they initiate the production of collagen after adhesion and proliferation, forming flexible and mildly elastic scaffold, and offering long-term wound stability.²

Free-tissue transfer is commonly regarded as the gold standard of reconstruction in complex wounds; however, patient comorbidities and other factors may be contraindications for free-tissue transfer surgery. With the application of BTM, the operating time is shortened, and morbidity is lowered compared with pedicled or free flaps, indicative of a reduction in surgical risk and complication.^5,10 The synthetic dermal matrix can, in addition, act as a layer for subsequent subcutaneous fat injection in the future.¹⁰ The temporizing design enables some degree of flexibility; patients have the temporary artificial matrix implanted while waiting for histopathological testing. The objective of the study is to retrospectively evaluate the clinical use, indications, and outcomes of BTM in wound management by analyzing wound characteristics, treatment timelines, and associated complications.

A consecutive case series review of patients who were treated with BTM at the Plastic Surgery Department, Lister Hospital, East and North Hertfordshire NHS Trust, Stevenage, United Kingdom, was performed from October 2021 to February 2023. Patient demographics, comorbidities, defect etiology, size of the defect, the reason for BTM use, operation details, and complications (if any) were documented using information acquired from the medical records. The time spent in initial hospital stay, the time from BTM implantation to integration, and the time spent on hospital stay for post-graft were recorded. The indications for BTM were grouped as follows: (1) covering wounds with exposed bone, (2) covering wounds with exposed tendon, (3) covering surgical wounds, and (4) burn wound temporization. Complications were grouped into the following categories: infection and non-adherence.

Surgical technique

BTM was used as specified by the manufacturer⁷ for all cases. Before the application of BTM, sharp debridement and clinical observation were employed to prepare the wound bed, remove devitalized tissue, and ensure that no active signs of infection were present. Initial dressings prior to BTM use were varied and included the use of topical negative pressure, according to the surgeon’s clinical decision.

The first stage involved the inset of BTM to the wound bed and quilting sutures to ensure maximal contact surface area was achieved. Sutures used for inset were varying sizes of Ethilon (J&J MedTech), Prolene (J&J MedTech), and Vicryl Rapide (J&J MedTech). The secondary dressings most commonly used were Jelonet (Smith & Nephew) with a sponge tie-over or Mepitel (Mölnlycke), gauze, and a bandage. Likewise, choices were made according to clinician preference and anatomical location.

Where it could be facilitated, and with patient factors considered, dressings management took place on an outpatient basis. At dressings changes, the BTM was inspected, cleaned, and redressed by specialist nurses.

The second stage involved delamination of the sealing membrane and refreshing the surface of the neo-dermis. A split-thickness skin graft was then harvested and inset to the wound margins. Skin grafts were inset with Vicryl Rapide sutures or tissue glue. Skin grafts were assessed for take between 5 and 7 days postoperatively.

Complications management

Infection was defined as the BTM developing a yellow-grey color and purulent exudate accumulating in the matrix underneath the dressing membrane when patients were postoperatively followed up at the dressing clinic. The nursing team reviewed the wound site and examined the presence of purulent exudate when the dressing was changed. Once identified, the nursing team applied manual pressure to release the purulent fluid until drained and washed the wound site with aqueous chlorhexidine. The nursing team flagged any medical concern and the patient was reviewed by the surgical team.

Nonadherence of BTM was defined as any part of the BTM not attached to the wound surface 3 to 4 weeks post-application, when the patient was reviewed at the plastic dressing clinic.

This case series included 12 patients with a median age of 63 years (range, 34-97 years); 75% (9 out of 12) were female. The decision for applying BTM was made by the responsible consultant, who took into consideration the patient’s demographics and defect factors, including covering exposed bone (5 cases), covering exposed tendon (5 cases), covering exposed surgical wound (1 case), and covering burn wound after terminalization (1 case). The sites of defects were the head (3 cases), hand (4 cases), wrist (1 case), abdomen (1 case), forearm (1 case), ankle (1 case), and chest (1 case).

The treated defects resulted from acute burn (1 case); infected animal bite wound (2 cases); dermal infection (1 case); complex surgical wound (2 cases); tumor excision, including basal cell carcinoma and squamous cell carcinoma (4 cases); bone reconstruction (1 case); and traumatic tissue loss (1 case).

Table. Case summary

Patient 5 presented to the Plastic Surgery Department with a confirmed diagnosis of basal cell carcinoma and received advice regarding the application of BTM and Mohs surgery. The indication for the application of BTM was to cover the exposed nasal bone and upper lateral cartilage. Clinical photography in Figure 1 was undertaken subsequent to Mohs surgery, prior to BTM application.

Figure 1. Photo of patient 5 taken post-Mohs excision of basal cell carcinoma and before the application of the biodegradable temporizing matrix (anterior view).

After 4 weeks, patient 5 returned to the theater to address a contour deficiency. No auxillary procedure was performed. Figure 2 depicts the clinical progress. Subsequently, 3 months post-application of the skin graft, the patient exhibited discernible enhancements in contour and aesthetic appearance, as shown in Figure 3. No postoperative complications were noted, and the patient was discharged from the hospital.

Figure 2. Patient 5 with basal cell carcinoma on the nose shown 4 weeks post-application of the biodegradable temporizing matrix to address the contour defect (left: anterior view; right: right lateral view).

Figure 3. Patient 5 with basal cell carcinoma on the nose shown 3 months post-application of the skin graft (left: anterior view; right: right lateral view).

Patient 9 presented to the Plastic Surgery Department with a confirmed diagnosis of basal cell carcinoma and received advice regarding the utilization of BTM and burring of the outer table of the cranium. The purpose for the application of BTM was to cover the exposed outer table of the skull. The clinical photography in Figure 4 was undertaken subsequent to burring of the outer table of the cranium, prior to BTM application.

Figure 4. Patient 9, who underwent excision of basal cell carcinoma after burring of the outer table of the cranium, shown 4 weeks post-application of the biodegradable temporizing matrix at the vertex of the scalp.

Three months post–skin graft application, patient 9 revisited the clinic, displaying notable enhancements in contour and aesthetic appearance. No additional auxiliary procedures were undertaken. Figure 5 illustrates the clinical progress observed during the outpatient clinic follow-up. Notably, no postoperative complications were recorded, leading to the patient's discharge from the hospital.

Figure 5. Patient 9, who underwent excision of a basal cell carcinoma after burring of the outer table of the cranium, shown 3 months post-application of the split-thickness skin graft on the biodegradable temporizing matrix at the vertex of scalp.

All cases would have otherwise required a more complex reconstructive procedure. The median time for inpatient stay was 3.5 days, where 6 cases were day cases, and the remaining 6 cases were admitted as inpatients. The shortest inpatient stay was 6 days, while the longest was 30 days with a complicated postoperative infection on the right forearm after significant soft tissue damage from a dog bite and open reduction internal fixation surgery.

Nine of 12 cases went on to receive application of a skin graft; the remaining 3 cases proceeded to heal by secondary intention. Of those 9 cases, the average time interval between BTM implantation and skin graft application was 33.2 days. For those patients who had a skin graft after the BTM integration, all patients underwent the procedure as a day case.

Postoperative complications of infection were encountered in 1 case, but there were no cases of non-adhesion concerns among the 12 patients. The infected case was superficial in nature and treated with a bedside washout. There was no delay in skin graft application and no long-term complications. Superficial infections were treated according to the trust’s antibiotics guidelines. Patient 12 did not receive a split-thickness skin graft and, as a result, the infection did not delay the definitive reconstruction procedure. As for other cases presented with complications, patient 6 had Achilles tendon repair surgery completed prior to BTM application; however, he had already developed signs of infections prior to BTM application. Thus, it was not considered as postoperative complication associated with BTM products, although it might have delayed the split-thickness skin graft application and the wound debridement; washout and split-thickness skin graft procedure were performed 64 days after the BTM implantation.

This case series of 12 patients includes defects from head to ankle caused by burns, surgical wounds, dermal infections, or traumatic loss. The median time for inpatient stay was 3.5 days, and patients who required skin grafts after full BTM integration were treated as day cases. One case had the postoperative complication of infection.

BTM has been found to be straightforward to apply and does not contribute to an additional critical step in the surgery. The surgical team accumulated experience in treating various defects in different anatomical positions and concluded that the skin graft take was satisfactory on the newly formed dermis. Following the Mohs surgery for patient 5 and the removal of the outer table of the cranium through burring for patient 9, it displayed effectiveness in treating basal cell carcinoma in the facial and head regions, respectively. It also contributes to the consecutive case series published by Solanki et al in New Zealand,⁷ which primarily focused on burns, necrotizing soft tissue infections, and traumatic tissue loss. With BTM, the length of hospital stay was minimal; 6 of 12 patients were discharged within a day. It was noted that occasional cases remained inpatient beyond expectation; however, it was not due to BTM-induced pathologies.

The success of BTM integration with no signs of infection can be predicted by day 14. Infections are commonly characterized by microbial contamination and unfavorable wound healing,¹¹ and their complications secondary to improper wound management may relate to sepsis and septic shock.¹² The presence of exudate induces early biodegradation detrimental to organized collagen deposition and effective wound modeling leading to scar formation.¹³The surgical team reported 1 case of postoperative infection, which was documented 11 days after BTM implantation for patient 12. In addition, the BTM product is a fully sterile, synthetic dermal substitute that offers compelling alternative to free-tissue transfer by reducing infection risk and complications through its non-biological composition, which acts as a microbial barrier against external contamination while promoting neodermis formation.

Nonetheless, the BTM is restricted to 2-dimensional cutting by surgeons and is unable to fully account for step defects, unlike 3-dimensional (3D) printing technology. Given that complex wounds can present in variable shapes, a 3-layer BTM can be introduced to improve contour and aesthetic outcome,¹⁰ which may be achieved by a 3-dimensional scanner and printer. The failure of general dermal matrices, including borderline vascularity or infection and staged process of reconstruction, was also noted.⁵ In addition, since BTM is a patented product, it carries a cost-implication concern, which the surgeon should weigh into the benefits and costs of various treatment options. A cost evaluation project may potentially be justifiable to establish indications of BTM use in the long term.

From a clinical perspective, the low infection rate, enhanced skin contouring, and favorable cosmetic results achieved at a reasonable cost with minimal hospitalization provide compelling reasons to contemplate universal adoption of BTM. This is especially pertinent in the facial and head and neck regions, where contouring and cosmetic outcomes are of paramount importance. Further case series reviews and randomized clinical trials should be carried out to investigate the association between BTM implantation and infection rate.