(WHS-P26) FINITE ELEMENT ANALYSIS MODELING AND PRECLINICAL STUDY TO ASSESS THE TISSUE STRAINS AND GRANULATION DURING NEGATIVE PRESSURE WOUND THERAPY WITH INSTILLATION USING A FELTED FOAM WITH 10MM HOLES
Friday, May 17, 2024
7:30 AM – 5:00 PM East Coast USA Time
Background: Not all patients with wounds are able to undergo surgical debridement. Negative pressure wound therapy with instillation (NPWTi) using a felted, reticulated open cell foam with an array of 10 mm holes (VCC*) has been used in clinic with NPWTi to eliminate non-viable material from the wound bed1. The current study uses Finite Element Modelling (FEA) to elaborate the biomechanical stresses, strains and work imparted to tissue with VCC versus the same felted foam without through holes (VC**). A porcine study was conducted to compare theoretical FEA results with those in actual sloughy wounds.
Methods: For this FEA model, skin was modeled as Neo-Hookean with a Young’s Modulus of 0.05 MPa and Poisson’s ratio of 0.15. Foam samples were compressed between steel platens to 70% compression to generate stress strain curves used in the model. For the preclinical study, full-thickness wounds were created at day 0 in a swine model. This study complied with the Animal Welfare Act and followed recommendations in the Guide for the Care and Use of Laboratory Animals. In vitro derived-slough was applied to the wounds at day 0 and NPWTi using VCC was initiated using a 10 min soak period and 3.5 h negative pressure period at -125mmHg. Dressings were changed every 2 or 3 days.
Results: Peak maximum principal strain imparted to tissue at -125mmHg with was 27.8% for VCC and 0.8% for VC. The frictional work around the holes in the VCC was 0.18 mJ. When the modelled holes were removed (VC), frictional work across the foam was negligible. The strain energy imparted to tissue with VCC was approximately 0.83 mJ for and 1.36 x 10-4 for VC. At study term, the granulation tissue thickness for wounds using VCC was significantly thicker than for VC (9.7 ± 0.1 mm vs 7.4 ± 0.5 mm; p = 0.02).
Conclusions: The through holes in VCC leads to higher forces imparted to the tissue than for VC. Frictional work around the 10mm holes which may pin the tissue in place under the holes leading to higher strain energy as the tissue is pulled up into the holes. This work done by the dressing with NPWTi may allow for fracturing of the devitalized tissue which then may be removed during the instillation cycle. The preclinical results corresponded to the FEA. There was more slough removed at earlier timepoints with VCC vs VC with an associated increase in granulation tissue. 1. Matthews, M.R. Cureus, 2018. DOI: 10.7759/cureus.3632