Be there or be square: Should we adopt non-rectangular dressing shapes in single-use negative pressure wound therapy?

Single-use negative-pressure wound therapy (suNPWT) dressings for closed surgical incisions are predominantly rectangular, despite long-time evidence from biomechanics that sharp or small-radius corners generate localized stress concentrations in underlying tissues. Optimizing dressing geometry and stiffness distribution may reduce the peri-incisional stress concentrations and improve closure.

To determine how dressing shape and regional stiffness variations influence the peri-wound skin stresses and stress concentrations and the incision closure biomechanics under a negative pressure level of -125 mmHg.

A validated three-dimensional finite element model of a sutured midline incision was developed. Five homogeneous dressing shapes (rectangular, circular, elliptical, stadium, and dome) of identical contact area and material properties were compared for reduction in peak lateral skin stresses (ΔS). The best-performing dressing shape underwent further testing in eight stiffness configurations (homogeneous, or with stiffer/softer peripheral regions in symmetric or axisymmetric patterns). The lateral displacement of the peri-wound skin was used as a measure for the closure work. A sensitivity analysis was conducted on chosen model variants for broader transferability and for exploring potential covariance between dressing shape and material properties.

Among the homogeneous dressing shapes, the circular dressing achieved the greatest stress reduction (ΔS = 2.9 %) versus the rectangular control (0.9 %). In the circular form, incorporating a stiffer peripheral symmetric ring around a softer core improved performance (ΔS = 3.2 %) while maintaining substantial lateral displacement (3.35 mm), achieving an optimal combination of stress relief with closure assistance. A fully stiff homogeneous dressing maximized the ΔS (6.5 %) but provided negligible closure support, whereas a fully soft dressing behaved conversely. The sensitivity analysis did not change these quantitative rankings across the studied model variants.

Eliminating sharp or small-radius geometric discontinuities and tuning the regional stiffness can markedly attenuate peri-incisional stresses without compromising the contribution of the dressing to the closure work. Circular suNPWT dressings with a peripheral stiffer ring offer a biomechanically superior, manufacturable alternative to conventional rectangular designs, warranting further pre-clinical and clinical evaluations.