Baumann Molly E, Blackstone Britani N, Malara Megan M, Clairmonte Isabelle A, Supp Dorothy M, Bailey J Kevin, Powell Heather M
Department of Biomedical Engineering, The Ohio State University, Columbus, OH, United States.
Department of Materials Science and Engineering, The Ohio State University, Columbus, OH, United States.
Burns. 2020 Jun;46(4):937-948. doi: 10.1016/j.burns.2019.10.009. Epub 2019 Nov 23.
Fractional CO lasers have been used in clinical settings to improve scarring following burn injury. Though used with increasing frequency, the appropriate laser settings are not well defined and overall efficacy of this therapy has not been definitively established. As it has been proposed that for thick hypertrophic scars proportionally greater fluence and thus deeper ablation into the scar tissue would be most effective, the goal of this study was to examine the role of ablation depth on scar outcomes in a highly-controlled porcine model for burn scars-after grafting.
Properties of laser ablated wells were quantified on ex vivo pig skin as a function of laser energy (20, 70 or 150mJ). Full-thickness burn wounds were created on the dorsum of red Duroc pigs with the eschar excised and grafted with a split-thickness autograft meshed and expanded 1.5:1. After four weeks of healing, sites were treated with either 20, 70, or 150mJ pulse energy from a fractional CO laser at 5% density or left untreated as a control. Sites were treated every four weeks with three total sessions. Scar area, pigmentation, erythema, roughness, histology, and biomechanics were evaluated prior to each laser treatment at day 28, 56, and 83, as well as four weeks after the final laser treatment, day 112. Additional biopsies were collected at day 112 for gene expression analysis.
The depth of the laser ablated wells increased with increasing pulse energy while the width of the wells was smaller in the 20mJ group and not significantly different in the 70 and 150mJ groups. Scar properties (area, color, biomechanics) were not significantly altered by laser therapy at any of the laser energies tested versus controls. Average scar roughness was improved by laser therapy in a dose dependent manner with scars treated with 150mJ of energy having the smoothest surface; however, these changes were not statistically significant. Assessment of matrix metalloproteinase 9 gene expression showed a slight upregulation in scars treated with 70 or 150mJ versus control scars and scars treated with 20mJ pulse energy.
The current study demonstrated that the properties of the ablative well (depth and width) are not linearly correlated with laser pulse energy, with only a small increase in well depth at energies between 70 and 150mJ. Overall, the study suggests that there is little difference in outcomes as a function of laser energy. Fractional CO laser therapy did not result in any statistically significant benefit to scar properties assessed by quantitative, objective measures, thus highlighting the need for additional clinical investigation of laser therapy efficacy with non-treated controls and objective measures of outcome.
分数二氧化碳激光已应用于临床，用于改善烧伤后的瘢痕形成。尽管其使用频率不断增加，但合适的激光参数尚未明确界定，且该疗法的总体疗效也未得到确切证实。由于有人提出，对于厚的增生性瘢痕，成比例地增加能量密度从而更深地消融瘢痕组织可能最为有效，因此本研究的目的是在高度可控的猪烧伤瘢痕移植模型中，研究消融深度对瘢痕结局的作用。
在离体猪皮肤上，根据激光能量（20、70或150mJ）对激光消融孔的特性进行定量分析。在红色杜洛克猪的背部制造全层烧伤创面，切除焦痂后移植1.5:1网状扩张的中厚自体皮片。愈合四周后，用分数二氧化碳激光以5%的密度，分别采用20、70或150mJ的脉冲能量对创面进行治疗，或不治疗作为对照。每隔四周治疗一次，共治疗三次。在每次激光治疗前的第28、56和83天，以及最后一次激光治疗后的第112天（四周后），对瘢痕面积、色素沉着、红斑、粗糙度、组织学和生物力学进行评估。在第112天采集额外的活检样本进行基因表达分析。
激光消融孔的深度随脉冲能量的增加而增加，而20mJ组的孔宽度较小，70mJ组和150mJ组的孔宽度无显著差异。与对照组相比，在所测试的任何激光能量下，激光治疗均未显著改变瘢痕特性（面积、颜色、生物力学）。激光治疗以剂量依赖的方式改善了平均瘢痕粗糙度，接受150mJ能量治疗的瘢痕表面最光滑；然而，这些变化无统计学意义。基质金属蛋白酶9基因表达评估显示，与对照瘢痕和接受20mJ脉冲能量治疗的瘢痕相比，接受7
