Abstract
Proof-of-concept computational models were developed and applied as tools to gain insights into biomechanical interactions and variations of oxygen gradients of wounded tissue subject to negative pressure wound therapy (NPWT), following trans-femoral amputation. A macro-scale finite-element model of a lower limb was first developed based on computed tomography data, and distributions of maximum and minimum principal stress values we calculated for a region of interest (ROI). Then, the obtained results were applied iteratively as new sets of boundary conditions for a specific spatial position in a capillary sub-model. Data from coupled capillary stress and mass- diffusion sub-models were transferred to the macro-scale model to map the spatial changes of tissue oxygen gradients in the ROI. The −70 mmHg NPWT resulted in a dramatic change of a wound surface area and the greatest relative contraction was observed at −150 mmHg. Tissue lateral to the depth of the wound cavity revealed homogenous patterns of decrease in oxygenation area and the extent of such decrease was dependent on the distance from the wound surface. However, tissue lateral to the width of the wound demonstrated heterogeneous patterns of change, as evidenced by both gradual increase and decrease in the oxygenation area. The multiscale models developed in the current study showed a significant influence of NPWT on both macro-deformations and changes of tissue oxygenation. The patterns of changes depended on the depth of the tissue, the geometry of the wound, and also the location of tissue plane.
Highlights
The care of complex wounds is one of the most significant challenges for healthcare systems today
The multiscale models developed in the current study showed a significant influence of negative pressure wound therapy (NPWT) on both macro-deformations and changes of tissue oxygenation
The computational model of tissue surrounding an excision wound cavity with the presence of filler in a residual limb of trans-femoral amputation exposed to the NPWT demonstrated that the wound filler was compressed against the inner-surface of the wound bed, followed by concentric deformation of the surrounding tissue in the superficial wound edges
Summary
The care of complex wounds is one of the most significant challenges for healthcare systems today. The residual extremity is covered with well-vascularized muscle, fascia, and skin. In the case of traumatic amputation, the remaining skin structure is not always sufficient to fully cover the wounded area and it is difficult to dress (Hinck et al 2010; Couch and Stojadinovic 2011; Richter and Knudson 2013a; Armstrong et al 2016). NPWT has become an accepted option for managing and treating trauma cases (Kanakaris et al 2007). It is beginning to be appreciated more widely in management of both high- and low-energy trauma wounds and open fractures of the lower extremity because of its ability to handle high volumes of exudate and provide a closed wound environment (Jeffery 2009)
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