Use of a collagen–elastin matrix for hard to treat soft tissue defects

Abstract

As deep soft tissue defects with exposed bone, cartilage or tendons are not suitable for wound closure with skin mesh grafts, other techniques are needed. We report on six patients, one female and five males, aged between 32 and 89 years, and deep soft tissue defects with exposed tendons, cartilage or bone. The aetiology of these defects was vascular (n = 3), tumour surgery (2), and post‐traumatic (1). Wounds were treated with a collagen–elastin matrix applied above the exposed structures. In five patients, the procedure was combined with mesh graft transplantation in the same setting. Follow‐up varied between 12 and 40 weeks. Wound healing was uncomplicated in all transplanted patients until first dressing change after 7 days. All but one transplant showed a 100% take rate and the transplant was stable within 10–14 days. A complete wound closure was also achieved without transplantation, but this took 8 weeks. No adverse effects were noted. There was no skin contracture of the skin grafts. Collagen–elastin matrix with split‐thickness skin grafts is a useful tool in deep soft tissue. The time to heal can be reduced.

INTRODUCTION

Larger soft tissue defects may occur because of trauma including burning or after skin tumour resection. As long as bony, cartilaginous or tendinous structures are exposed, skin transplants are not successful. Transplant healing is dependent on nutrition by connective tissue layers with a sufficient microcirculation. The procedures to create a healthy granulation tissue above tendons, bone and cartilage are often time‐consuming and not always successful (1). Bone, cartilage or tendons can be severely injured and may lose stability and function. Dermal tissue substitutes have been developed to encompass complications of a delayed wound healing (2).

A dermal substitute consisting of a native (non‐cross‐linked) collagen matrix supplemented by elastin hydrolysate has been developed, known as Matriderm™. It is available in sheets of 1 and 2 mm thickness and may be covered in a single‐step procedure with immediate split‐thickness skin grafting. In experimental models the matrix reduces wound contracture; histologically, collagen bundles in the scar are more randomly orientated 3, 4. There is no diminished take of split‐thickness graft and only marginally prolonged healing time compared with the split‐thickness graft alone. Clinical trials with a long‐term clinical evaluation showed no difference in scar elasticity between the described dermal substitute and split‐thickness graft alone 5, 6.

We report a case series of patients with deep soft tissue defects and exposed underlying structures in dermatologic surgery.

PATIENTS AND METHODS

We report a case series with six patients, one female and five males aged between 32 and 89 years (Table 1). Three patients suffered from leg ulcers of different aetiologies with exposed tendons. Two patients had larger skin defects on the scalp or nose after micrographically controlled tumour surgery with exposed bone or cartilage. In these patients, the adjacent skin was severely sun damaged. Although usually used to gain a better aesthetic outcome, local flaps would have not been suitable here. Therefore, mesh‐graft transplants from less ultraviolet light (UV)‐exposed areas were used. The last and youngest patient presented with a temporal scalp defect with exposed scull bone after traffic injury.

Table 1.

Demographics of patients, wound situation and outcome

Patient no.	Age	Gender	Indication	Exposed structures	Outcome
1	88	Male	BCC, scalp	Bone	Complete healing (10 days)
2	83	Male	BCC, nose	Cartilage	Complete healing (10 days)
3	78	Male	Leg ulcer, of the right distal lower leg	Achilles tendon	Complete healing (12 days)
4	75	Male	Leg ulcer after necrotising fasciitis	Tendons	Complete healing (14 days)
5	32	Male	Scalp defect	Bone	Complete healing (8 weeks)
6	89	Female	Mixed vascular leg ulcer, left side	Tendons	Primary healing but partial loss of transplant after 2 weeks

BCC, basal cell carcinoma.

All patients had been treated according to good ulcer care but spontaneous healing was either impossible or the risk of infection, loss of tendons, cartilage or bone was too high. Therefore, we used a dermal template. The collagen–elastin matrix (Matriderm™; Dr. Suwelack Skin & Healthcare, Germany) comes in sheets of 74 × 52 × 1 mm. Matriderm™ is a native, structurally intact matrix of bovine collagen and elastin. These extracellular matrix proteins serve as a scaffold for reconstitution of the skin and the modulation of scar tissues. The matrix serves as a support structure for the in‐growth of cells and vessels. The elastin component improves the stability and elasticity of the regenerating tissue. As the healing process advances, fibroblasts produce their own extracellular matrix and Matriderm™ is resorbed. Matriderm™ remains stable and elastic in wet conditions without any chemical cross‐linking agents. The dried sterile sheets are reconstituted in Ringer's solution for a couple of minutes until the sheet becomes transparent. We applied the collagen–elastin matrix on wounds above the exposed structures (bones, cartilage or tendons).

In five patients, we used a sandwich technique where we transplanted mesh grafts above Matriderm™ in the same session. Mesh grafts were fixed and covered by a non‐adhesive silicone sheath (Mepithel™) and covered by multilayered bandages. First dressing change was carried out after 7 days.

In patient #4, the large soft tissue defect was close to his knee joint. The transplant was covered with a microporous white foam (GranuFoam™) and vacuum‐assisted closure (V.A.C.™; KCI Licensing, Inc., San Antonio, TX) with intermittent negative pressure was applied for 7 days after surgery.

In the patient with the scalp defect, Matriderm™ was used without grafting, because a cranioplasty was planned for later. Dressing changes were performed on a regular base every other week until wound closure after 8 weeks. Follow‐up of patients varied between 12 and 40 weeks.

RESULTS

All wounds were free of signs of infection. Matriderm™ was reconstituted with Ringer's solution. Handling of the collagen–elastin sheets was easy. The sheets were placed above exposed tendons, cartilage or bony structures. The sheets were fixed by the mesh‐graft transplant or (in patient #5) by a secondary non‐adhesive foam dressing. Operation time was not enhanced.

Healing was uncomplicated in all transplanted patients until first dressing change. We lost a transplant later in patient #6, who suffered from a long‐standing (<3 years) leg ulcer of the distal lower leg of mixed vascular aetiology. The arterial component could not be improved by vascular surgery but was said to be compensated. She also suffered from cardiac disease and diabetes mellitus. After 2 weeks she developed a wound infection with loss of transplant despite systemic antibiosis. All other patients could be released from the hospital with stable transplants and complete wound closure after 1–2 weeks (Table 1). Patient #4, who had the largest soft tissue defect, achieved a complete take of the graft with the support of V.A.C.™ therapy. There was no skin contracture of the skin grafts. Patient #5, without surgery, developed a complete wound closure that was stable during follow‐up for 7 months. No adverse effects were noted (1, 2).

Figure 1.

Patient #3 with a chronic leg ulcer above the Achilles tendon. (A) Before surgery; (B) 7 days after sandwich transplantation with collagen–elastin matrix and mesh graft; (C) 6 months later: stable transplant.

Figure 2.

Patient #4 after surgery for necrotising fasciitis. (A) Exposed infrapatellar tendons. (B) Placement of the reconstituted collagen–elastin matrix above exposed tendons. (C) Mesh‐graft transplantation. (D) Three weeks after surgery is completed and stable take of the graft.

DISCUSSION

The gold standard for the closure of larger full‐thickness skin defects is autologous skin grafts. However, poor skin quality and scar contracture are well‐known problems in functional, highly strained regions. The use of dermal substitutes is an appropriate way to minimise scar contraction and, thereby, to optimise the quality of the reconstructed skin (2).

Several acellular dermal substitutes have been developed worldwide. Integra™ (Integra Life Sciences Corp., Plainsboro, NJ) is a bovine irreversibly cross‐linked collagen–glycosaminoglycan (chondroitin‐6‐sulphate) copolymer with silicone backing successfully used for the treatment of burn wounds and for the repair of hypertrophic scars and keloids. Oasis™ is a collagen matrix from porcine small intestinal submucosa with a long shelf‐life (Cook Biotech, West Lafayette, IN) established in gynaecology and urology. AlloDerm™ (KCI LifeCell Corpor., San Antonio, TX) is an allogeneic (human) dermal matrix with an intact basement membrane mostly used for hernia repair and breast reconstruction 7, 8, 9, 10.

Matriderm™ is a collagen–elastin matrix containing native bovine collagen type I, II and V coated with elastin hydrolysate derived from bovine ligamentum nuchae in a concentration of three weight‐to‐weight ratio that showed improved wound healing, vascularisation, transplant nutrition and survival, less contractures and better functional and aesthetic outcome in animal models and clinical practise 3, 4, 5, 6.

Collagen–elastin matrix has been used successfully to cover burn wounds combined with mesh‐graft transplantation or split‐skin transplantation without meshing as a one‐step procedure 11, 12, 13, 14, 15, 16. Another indication for the dermal matrix substitute is the closure of traumatic defects or defects after tumour surgery with exposed tendons 17, 18. Seventeen patients with full‐thickness skin defects of the upper extremity were treated with unmeshed skin graft in the functional critical region of the distal upper extremity in a single‐step procedure. The take rate of the matrix‐and‐skin graft was 96%. No limitation concerning hand function was observed (17)

There has been no systemic investigation of these dermal substitutes in head‐to‐head studies. Only recently, an experimental study in a rat model compared Integra™ and Matriderm™ in a two‐step procedure with matrix implantation and subsequent epidermal grafting. In terms of vascularisation and thickness of resulting neodermis, both products produced comparable results (14).

We applied collagen–elastin matrix to six patients in dermatologic surgery to close soft tissue defects with exposed subcutaneous structures such as tendons, bone or cartilage. Five of the six patients were elderly (75–89 years of age) with multiple comorbidities, such as pulmonary, cardiac or vascular disease, and diabetes mellitus.

In five patients, mesh‐graft transplantation was performed in the same session. In patient #4, vacuum‐assisted closure was applied using the microporous foam above the mesh‐graft transplant. It has been reported that V.A.C.™ therapy can furthermore support wound healing and in particular wound bed granulation 19, 20. The procedure has also been used to secure split‐thickness skin grafts 21, 22. We observed an excellent healing of the large defect.

In a single patient with combined vascular disease leading to leg ulcer and diabetes, a secondary wound infection caused a loss of the mesh graft after 2 weeks (patient #6).

Patient #5 was treated with Matriderm™ alone. Here, a complete and stable wound closure of a full‐thickness scalp defect with exposed bone could be achieved within 8 weeks.

Matriderm™ seems to be a useful tool to achieve a final wound closure in partial‐ and full‐thickness soft tissue defects of various aetiologies. It can be combined, depending on the individual situation, with mesh‐graft transplantation with or without vacuum‐assisted closure. This is an advantage for challenging wound problems. In our hands, this procedure has become a valuable tool.