A Novel 3-dimensional–Printed Hand Model to Simulate Bony Fixation With Kirschner Wires Without Fluoroscopy

Abstract

PURPOSE: Simulation has become a mainstay in medical training. The field of 3-dimensional (3D) printing offers additional benefits to medical simulation, allowing for the development of affordable, custom anatomic models. Surgical subspecialties, like plastic surgery and orthopedics, can reap significant benefits from this technology. Specifically, developing the art of operative planning and mastering unique procedural skills are essential to the armamentarium of the plastic surgeon. One skill that is particularly difficult to master in early training is the use of Kirschner wires (K-wires) for bony fixation of the hand and wrist. Brichacek et al1 have used 3D printing for this specific training purpose, but their construct of silicone and iron-based bones requires fluoroscopy for evaluation of metacarpal K-wire placement, involving more than minimal risk of radiation exposure to trainees (Brichacek et al1). Herein, the purpose of this project is to develop a 3D-printed hand and wrist model that serves as a training and evaluation tool for K-wire placement that is novel, cost-effective, durable, and does not require fluoroscopy. METHODS: This novel hand model utilizes 3D printing technology and silicone molding. Data obtained from a computed tomography scan of a healthy hand and wrist were used to 3D print a reusable mold for the fabrication of the silicone-based “soft tissue.” Computed tomography scan data were also used to print out the bony structures of the hand and wrist (carpal bones, metacarpals, and phalanges) from ABS Filament on a UPrint SE+ 3D printer (Stratasys; Eden Prairie, Minn.). Three-dimensional–printed bones were placed in the 3D-printed mold and sealed with silicone to recreate the surrounding soft tissue. Thin filaments connecting the bones were broken after the silicone set, allowing for realistic simulation of hand joint mobility. Bony structures were exchanged and replaced after use via a palmar incision. RESULTS: To test durability of the model, 20 K-wire placements were performed. Preliminary trials demonstrated the silicone to be durable, withstanding multiple K-wire passes without breakdown. Additionally, the metacarpal bones were easily replaced for repeat use. Bones were intentionally printed with a linear infill pattern (lattice matrix) to evaluate disruption of the lattices by K-wire passes. Accuracy and proficiency of K-wire placement are assessed by direct visualization of the disrupted matrix compared to conventional assessment with fluoroscopy. Total cost of material for each hand model was $25.00. For reference, the largest bone in the hand (metacarpal) could be replaced for a material cost of $0.50. CONCLUSIONS: Implementation of 3D printing and silicone casting can be used to produce a cost-effective and reproducible training tool for bony fixation of the hand and wrist. We are currently validating our 3D-printed K-wire placement hand and wrist model for educational utility among plastic surgery residents. Radiation exposure can also be avoided by studying the placement of K-wires through direct visualization of the altered 3D-printed matrix. REFERENCE: 1. Brichacek M, Diaz-Abele J, Shiga S, et al. Three-dimensional printed surgical simulator for Kirschner wire placement in hand fractures. Plast Reconstr Surg Glob Open. 2018;6:e1706.