The clinical efficacy of the 3D-printed transparent facemask on management of facial burn scars

Abstract

Background: Facial hypertrophic scars resulting from burn injuries can cause deformities that severely affect the normal appearance and function of the face, leading to significant physical and psychological damage. Pressure therapy and silicone gel are widely used non-invasive interventions for the prevention and treatment of hypertrophic scars. However, applying these treatments to the face is challenging because the face has complex geometric features, which makes the design and fabrication of appropriate pressure masks challenging. The emergence of new 3D printing materials and techniques may substantially improve the ease and accuracy of producing pressure masks. Such techniques may also exploit computer-aided, biomechanical design to improve therapeutic efficacy. Aims and Objectives: The aim of the study is to investigate the efficacy of the newly developed 3D-printed transparent facemask for management of facial hypertrophic scars. The objectives of the study include: 1. validating a measurement tool (dermoscope) to measure scar vascularity and pigmentation; 2. developing a biomechanical model to assist 3D printed transparent facemask design; 3. finding out the clinical efficacy of the 3D printed transparent facemask, including short-term efficacy in terms of pressure measurement, and long-term efficacy in terms of clinical outcomes after treatment. Methods: In phase I of the study, twenty subjects with hypertrophic scars were assessed using the Vancouver Scar Scale (VSS), spectrocolorimeter and dermoscope. Correlations between the measurements by these tools and reliability parameters were examined. In phase II of the study, patients' faces were scanned using a portable 3D scanner, and the scans were turned into printable 3D mask files using computer-aided design. A biomechanical model of the 3D mask was established to analyze the pressure distribution on a standard subject. The design of the 3D mask was made based on the biomechanical principles obtained through finite element analysis of the standard model. The 3D mask design file was printed out with transparent and biocompatible 3D printing material and lined with silicone gel on the inside surface. These custommade 3D-printed transparent facemasks were used with 12 patients, including 2 young children, to allow assessment of clinical efficacy. The pressure dosages provided by the 3D-printed transparent facemasks were compared with those provided by traditional pressure masks. The clinical efficacy of the 3D-printed transparent facemask was evaluated using objective and subjective scar measurement tools. Results: In phase I of the study, strong correlation was found between spectrocolorimetric and dermoscopic redness a* readings (r = 0.818, p < 0.01), as well as between VSS vascularity scores and dermoscopic redness a* readings (ρ = 0.775, p < 0.01). The ICC (3, 1) of the dermoscopic redness a* was 0.989 (95% CI: 0.980 to 0.994, p <0.01), and that of lightness L* was 0.860 (95% CI: 0.766 to 0.918, p < 0.01). The ICC (2, 2) of dermoscopic redness a* was 0.953 (95% CI: 0.896 to 0.979, p < 0.01) and that of lightness L* was 0.824 (95% CI: 0.639 to 0.919, p < 0.01). In phase II of the study, the biomechanical model of the 3D-printed transparent facemask using a healthy subject was successfully established with 52477 nodes and 231879 elements. The 3D-printed transparent facemask for clinical use was fabricated based on the optimized biomechanical design. The 3D-printed transparent facemask proved easy to produce and it provided more balanced and effective pressure than traditional pressure masks. The average pressure with 3D-printed transparent facemask was significantly higher than traditional masks(p<0.05). The 3D-printed transparent facemask reduced scar thickness and hardness more than traditional pressure masks (p<0.05). Patients positively evaluated the 3D-printed transparent facemask, and significant difference was found between the patient's ratings for the 3D-printed transparent facemask and traditional pressure masks (p<0.05). The 3D-printed transparent facemask is also effective and more convenient than traditional masks for treating pediatric patients. Conclusion: Dermoscope is a promising objective tool for vascularity and pigmentation assessments of hypertrophic scars with good validity and reliability. 3D-printed transparent facemask is a successful technological innovation that shows great potential for precise and customized rehabilitation of facial burns. It may provide an effective alternative to current treatment modalities and thereby help reduce facial hypertrophic scars of tens of thousands of burn patients, facilitating thei rreintegration into normal life.