A total of 300 patients was identified and included in the present analysis. Of these, 101 (33.7%) were female. Mean age at the time of admission was 54.2 ± 20.1 years. The most frequent wound aetiology was burns (n=179, 59.7%), followed by mechanical trauma (n=59, 19.7%), pyogenic infections (n=14, 4.7%) and tumours (n=6, 2.0%).
It was shown that most of the cases could successfully be reconstructed with an overall take rate of 83% (BTM) and 86% (STSG on BTM). A major positive predictor for STSG take rate was the BTM take rate. Additionally, it was found that positive wounds swabs before BTM application and longer time from trauma-to-BTM-application negatively predict BTM take rates.
In our department, we saw a shift from using allografts for the initial temporary coverage of large burn wounds towards an early BTM application, when full-thickness wounds were not suitable for immediate STSG and/or the patient was unstable. One of the main reasons for the application of BTM is the absence of a well-perfused wound bed, which does not allow for immediate STSG8. After a period of usually 3-4 weeks and adequate integration of BTM, a viable and stable wound bed is created. Then, STSG can be applied to the wound. In some cases, such as in patients with diabetes or peripheral artery disease BTM needs more time for recapillarization. Therefore, it is important to clinically observe and evaluate the condition of BTM to find the correct timing for grafting.
In some institutions, BTM is also used to cover technically STSG-ready wounds in order to improve scarring, for example over joints. This may be an area of interest for further (long-term) studies.
In third degree burns, epifascial necrectomy can be avoided, when BTM is placed on top of viable fatty tissue. To a certain extent, this also allows the coverage of critical structures such as tendons and joint capsules without the necessity for free flaps or other more invasive and technically advanced methods, while preserving the contour of the body surface. As shown in this study, the exposure of tendons and joint capsules were no negative predictors for BTM and STSG take rates. Especially in high-volume centres, microsurgical reconstruction of large wounds with exposed functional tissue such as bones or tendons, free flaps are usually the gold standard in order to receive permanent coverage17, 18, 19. However, some patients may not be ideal candidates for free flap reconstruction due to age, lack of adequate blood supply in the extremities, comorbidities or anticoagulation. These cohorts however, may be eligible for BTM transplantation as an alternative to amputations, when small areas of functional structures are exposed. Nonetheless, long-term data on the stability and functional outcome of these treatments compared to free flaps is needed.
There are numerous potential advantages of BTM compared to other dermal substitutes or treatment methods including the absence of donor site morbidity in the first surgery, the rather easy application and wound care as well as low complication rates which make the use especially suitable for patients with multiple comorbidities. For these patients, BTM can be a rescue option or an alternative to amputations because it requires fewer resources and operation time compared to free flaps or large autologous skin grafting, especially in patients who are unfit for immediate excision and autologous grafting9. BTM might also represent a barrier for potential infections which might be seen more often in temporary coverages with allograft. When using BTM, no major consecutive dressing changes are needed, and physical therapy can usually start early. Furthermore, the second surgery can also be postponed until the patient is stable and/or sufficient donor sites are available for STSG. When used in major burns, no frequent changes of allograft as temporary coverage are needed for 3-4 weeks until BTM is healed and can be grafted.
The present study yielded less favourable results in terms of lower take rates of BTM and STSG when certain comorbidities such as diabetes, peripheral artery disease or high BMI. This is in line with several studies which reported a significantly higher risk for lower graft take and longer healing times in patients with diabetes and patients with vascular interventions20, 21.Interestingly, smoking was not found to be associated with either BTM or STSG take. Many previous studies on autografts in burns and other areas showed a negative association between nicotine use and graft take as seen in a recent meta-analysis.
The costs of BTM application were not evaluated in this study, but should be considered, especially in large wounds8. As it is a two-step approach, theoretically there is a prolonged hospital stay necessary until sufficient integration is present and the second surgery can be performed. However, in our experience, patients with small wounds can quickly be mobilized, regain strength and even get discharged with outpatient wound care and be readmitted shortly before the second surgery without any loss of quality of care.
Conclusion To our knowledge, we herein present the largest cohort of patients that were treated with BTM. We were able to show that complex wounds of different sizes and aetiologies that do not qualify for immediate STSG can be treated successfully with BTM and lead to satisfactory results in terms of high take rates of both BTM and STSG. Infected wounds led to poor BTM take rate whereas good BTM take rate led to high STSG take rates.
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