Maier Johannes, Weiherer Maximilian, Huber Michaela, Palm Christoph
Regensburg Medical Image Computing (ReMIC), Ostbayerische Technische Hochschule Regensburg (OTH Regensburg), Galgenbergstraße 32, 93053 Regensburg, Germany.
Department of Trauma Surgery & Emergency Department, University Hospital Regensburg, Franz-Josef-Strauß-Allee 11, 93053 Regensburg, Germany.
Quant Imaging Med Surg. 2019 Jan;9(1):30-42. doi: 10.21037/qims.2018.09.17.
Currently, it is common practice to use three-dimensional (3D) printers not only for rapid prototyping in the industry, but also in the medical area to create medical applications for training inexperienced surgeons. In a clinical training simulator for minimally invasive bone drilling to fix hand fractures with Kirschner-wires (K-wires), a 3D-printed hand phantom must not only be geometrically but also haptically correct. Due to a limited view during an operation, surgeons need to perfectly localize underlying risk structures only by feeling of specific bony protrusions of the human hand.
The goal of this experiment is to imitate human soft tissue with its haptic and elasticity for a realistic hand phantom fabrication, using only a dual-material 3D printer and support-material-filled metamaterial between skin and bone. We present our workflow to generate lattice structures between hard bone and soft skin with iterative cube edge (CE) or cube face (CF) unit cells. Cuboid and finger shaped sample prints with and without inner hard bone in different lattice thickness are constructed and 3D printed.
The most elastic available rubber-like material is too firm to imitate soft tissue. By reducing the amount of rubber in the inner volume through support material (SUP), objects become significantly softer. Without metamaterial, after disintegration, the SUP can be shifted through the volume and thus the body loses its original shape. Although the CE design increases the elasticity, it cannot restore the fabric form. In contrast to CE, the CF design increases not only the elasticity but also guarantees a local limitation of the SUP. Therefore, the body retains its shape and internal bones remain in its intended place. Various unit cell sizes, lattice thickening and skin thickness regulate the rubber material and SUP ratio. Test prints with higher SUP and lower rubber material percentage appear softer and vice versa. This was confirmed by an expert surgeon evaluation. Subjects adjudged pure rubber-like material as too firm and samples only filled with SUP or lattice structure in CE design as not suitable for imitating tissue. 3D-printed finger samples in CF design were rated as realistic compared to the haptic of human tissue with a good palpable bone structure.
We developed a new dual-material 3D print technique to imitate soft tissue of the human hand with its haptic properties. Blowy SUP is trapped within a lattice structure to soften rubber-like 3D print material, which makes it possible to reproduce a realistic replica of human hand soft tissue.
目前，三维（3D）打印机不仅在工业中用于快速成型，在医学领域也用于为缺乏经验的外科医生创建培训用的医疗应用。在用于使用克氏针（K 线）固定手部骨折的微创骨钻孔临床训练模拟器中，3D 打印的手部模型不仅在几何形状上，而且在触觉上都必须正确。由于手术过程中的视野有限，外科医生需要仅通过触摸人手的特定骨突来完美定位潜在的风险结构。
本实验的目的是仅使用双材料 3D 打印机以及皮肤和骨骼之间填充支撑材料的超材料，来模仿具有触觉和弹性的人体软组织，以制造逼真的手部模型。我们展示了通过迭代立方体边缘（CE）或立方体面（CF）晶胞在硬骨和软皮肤之间生成晶格结构的工作流程。构建并 3D 打印了具有不同晶格厚度、有无内部硬骨的长方体和手指形状的样品。
现有的最具弹性的类似橡胶的材料太硬，无法模仿软组织。通过支撑材料（SUP）减少内部体积中的橡胶量，物体变得明显更软。没有超材料时，分解后，支撑材料可以在整个体积中移动，从而物体失去其原始形状。虽然 CE 设计增加了弹性，但它无法恢复织物形状。与 CE 相反，CF 设计不仅增加了弹性，还保证了支撑材料的局部限制。因此，物体保持其形状，内部骨骼保持在其预定位置。各种晶胞尺寸、晶格加厚和皮肤厚度调节橡胶材料和支撑材料的比例。支撑材料含量高而橡胶材料百分比低的测试打印件显得更软，反之亦然。这得到了一位专业外科医生评估的证实。受试者判定纯类似橡胶的材料太硬，而仅填充支撑材料或 CE 设计中的晶格结构的样品不适合模仿组织。与具有良好可触及骨结构的人体组织触觉相比，CF 设计的 3D 打印手指样品被评为逼真。
我们开发了一种新的双材料 3D 打印技术，以模仿具有触觉特性的人手软组织。充气支撑材料被困在晶格结构中，以软化类似橡胶的 3D 打印材料，这使得再现人手软组织的逼真复制品成为可能。
