Immediate Application of Biodegradable Temporizing Matrix To a Muscle Free Flap for Complex Soft Tissue Reconstruction

Lower limb compound fractures with degloving injuries are life-changing events that can result in significant deformity and loss of function. Such injuries pose substantial challenges in management, particularly so in the pediatric population. Contractures limiting joint function and impairing quality of life occur in 25% of children after burn injuries^1,2,3 and are more likely for lower limb injuries than for those of the upper limb.¹ For this reason, there is much room for improvement in handling children and adolescents with significant soft tissue injuries of the lower limb.

Traditionally, the mainstay of treatment of complex compound tibial fractures involves free tissue transfer to provide vascularized soft tissue coverage over the open fracture and autograft to the remaining areas of skin loss and over muscle free flaps. Whereas wound closure may be satisfactorily achieved with this approach in skeletally mature individuals, long-term issues related to scar contractures from autograft can require subsequent procedures. This problem is further exacerbated in the pediatric population where subsequent growth of the child can lead to reduced range of movement from growth restrictions. For the last 3 decades, in anticipation of such complications, dermal regenerative matrices have been used to provide improved skin pliability for reconstruction.⁴

Dermal matrices such as Integra (Integra LifeSciences Corporation) and Matriderm (MedSkin Solution) can be used as either a single- or dual-staged procedure. Both products are biological in origin and thus are at risk of infection and partial or whole dermal template loss. Dressing care of the products must be meticulous to avoid infection while awaiting neovascularisation before second-stage grafting. These concerns regarding propensity to infection and by extension cost-effectiveness⁴ have led to the development of a new entirely synthetic dermal template.

Biodegradable temporizing matrix (BTM, PolyNovo) is a fully synthetic polyurethane bilaminar matrix that temporizes the wound, reconstructs the dermis, and subsequently enhances soft tissue volume and pliability.⁵ Whereas the use of BTM is well documented for acute burn care and reconstruction, to date there are no reports of BTM as an immediate adjunct to free flap reconstruction to augment the soft tissue envelope volume. Given the putative advantages, we report the use of immediate BTM application over a free muscle flap for complex lower limb reconstruction in a child.

A previously healthy 7-year-old child sustained bilateral open tibial fractures with severe degloving having been run over by an articulated lorry. Definitive wound closure of both open fractures with free tissue transfer was performed on day 8 post injury following serial debridement as skin necrosis demarcated. The right open tibial fracture was covered with a right-sided anterolateral thigh free flap. The left open tibial fracture was covered with a left-sided myocutaneous latissimus dorsi free flap, with a small skin island for monitoring. A free muscle flap was chosen due to the size of exposed fracture and the paucity of further fasciocutaneous donor sites in this young child.

Given the severity of degloving to muscle/fascia, primary application of a dermal template was chosen to augment subsequent soft tissue volume and improve graft pliability. The degloved wound (from mid-thigh to ankle, circumferentially; (Figure 1) was covered with BTM, including over the latissimus dorsi myocutaneous flap, leaving the skin island exposed for flap monitoring. BTM was also used on the right anterolateral thigh flap donor site and negative pressure wound therapy applied to both legs (Figure 2).

BTM delamination was performed 20 days following application (day 30 post injury) with almost 100% integration (Figure 3). All the BTM was covered with meshed autograft, with 100% graft take at 48 hours and subsequent dressing changes (Figure 4). External fixation of the left tibial fracture was performed 10 days later through the stable skin graft and BTM. Due to the presence of the bilateral open tibial fractures and extensive soft tissue injuries it was anticipated the patient would not be weight-bearing on either leg for some time. The fibula was intact on the left side and holding the leg out to length. It was hoped that the left side would unite enough with the intact fibula and plaster of Paris splint for support that metalwork could be avoided. However, the bone did not unite and was unstable during theatre dressing changes; thus, as soon as the latissimus dorsi flap and BTM were integrating and stable, the Taylor spatial frame was applied in theatre (Figure 5). 

Dermal matrices offer a staged reconstructive option, improving vascularity, contour, texture, and pliability of the wound bed before definitive closure and thereby offering favorable advantages to autograft alone by replacing lost dermis with thicker uniform contour and hopefully reduced wound contraction.⁶

Whereas synthetic material is traditionally thought to be more prone to microbial infections, BTM typically offers increased resistance against infections compared with biological dermal substitutes. Any collections within the template can be expressed through the fenestrations or through an incision, and as the product is inert, the template itself does not become infected and degrade. The institution where this study was performed has not experienced any BTM loss from infection, and BTM has gained popularity amongst nursing staff as it is easy to care for.

This is the first reported case of immediate BTM application over a myocutaneous free flap to augment soft tissue volume during complex lower limb reconstruction. In this case, the rationale of using BTM was to provide a robust and pliable tissue layer, which, when skin grafted, provided an improved cosmesis and long-term functional outcomes than skin grafting alone. Though other dermal substitutes can be used, BTM was used due to its higher resistance against infections, for which this patient is at an increased risk given the nature of the injury. Furthermore, BTM application reduced the metabolic demand, avoiding the early creation of graft donor sites and the need for graft nutrition in a child having undergone bilateral free flap tissue transfer. By staging the reconstruction, it was felt to be advantageous for both healing and rehabilitation as joint movement can commence relatively early at 10 to 14 days following BTM application.

No issues were encountered when applying BTM directly to the muscle free flap, ensuring it was contoured and quilted with staples and leaving only a small skin island for flap monitoring. The anterolateral thigh donor volume was also enhanced, avoiding graft application directly to the underlying muscle and improving skin pliability.

In summary, immediate BTM application was found to be a useful adjunct to free tissue transfer and soft tissue reconstruction in a wound that traditionally would have been managed with autograft alone. BTM had no negative effect on free flap monitoring or healing, and by combining in a single stage, long-term skin quality has hopefully been improved. Whether this has reduced the need for subsequent contracture release is unknown.

Affiliations: Department of Plastic Surgery, Royal Victoria Infirmary, Newcastle upon Tyne, England

Correspondence: Sachin Teelucksingh MRCS; sachin.teelucksingh@nhs.net

Disclosures: The authors have no relevant financial or nonfinancial interests to disclose.