3D Printing: "Reprap" Surgery with an "Undo" Button

We at SALSA have long embraced the benefits of inter-connectivity and Open Source solutions; surgical planning and collaboration are no exception. The concept of 3D surgical “printing” (templating and simulation) in lower extremity reconstruction is not entirely commonplace. This is likely for a number of reasons. With the continual maturation of free and Open Source software applications as well as the ever increasing capabilities of Reprap technology, these limitations are overcome.

Charcot foot reconstruction is a challenging endeavor with significant intraoperative demands and uncertainties. Even experienced surgeons benefit from preoperative preparation in order to reduce operative time and potential complications. Classic 2D templating techniques may fall short when faced with the multiplane and complex nature of neuroarthropathic architecture. For this, a scenario to improve surgical delivery was Co-designed by members of Dekalb Medical Residency, Southern Arizona Limb Salvage Alliance researchers, and Freeside Atlanta and then performed by Dr. S. Patrick Dunn DPM.

Clinical and Radiograph films of patient’s foot.

This process started with a high resolution Computed Tomography scan. These standard DICOM images were able to be processed with Axial data in (freeware) Osirix Image Viewer. These files were then used for 3D Surface Rendering. As has been described, this offers a physicians an improved sense of spatial pathology. This constructed model is then something which can be imported into an a 3D application of your choice. For our purposes, we were able to use a combination of Meshlab and Blender, for this study.

Computed Tomography demonstrating significant architectural destruction and luxation

We started by importing the Stereo Lithography data (STL) data into Blender and templating out a multiplane wedge/chevron across our anatomic reconstruction. This was then then “practiced” as a booleon resection in the objects geometry. This simulation technique afforded real-time viewing and assessment of osseous apposition. The process could be undone and reattempted for optimal outcome, as many times as desired. Once a satisfactory simulation was achieved, measurements and axis orientation was able to be measured to scale (Blender units must first be calibrated to match the CT scale).

Furthermore, this STL formatted data was then utilized for making three dimensional “prints” of the patient’s anatomy. This physical prints may be manufactured on the technology and method of your choosing. For our purposes, we chose the selective deposition/binding methods offered by the Zcorp printing technology for printing sawbone replicas.

Simulated osteotomies matched up to realworld osteotomies. Booleon simulation may be performed in a variety of freeware or profession 3D applications.

These printing machines are often expensive at market value. Reprap enthusiast and non-institutional “Printistas” have adopted these devices and have made several modifications o the proprietary hardware as well as printing recipe’s to serve a number of desired outcomes. Our models were printed on the Z400/402 machine technology, which was modified by nullset, with his published technique for DIY printer cartridge making.

Before these models could be printed, the geometry and surface information needed to be further optimized. Our member, Patch, performed this in Meshlab, in order to optimize the geometry prior to ZPrint importation. These printed models were to attempt “freehand” osteotomies, matching the measured landmarks from the simulated ones, which were used to size and fit an Ilizarov frame construct. This construct was subsequently sterilized and used for the procedure itself, to follow.

Telemedical preoperative planning was discussed amongst surgeons at two locations, (Tucson, AZ and Decatur, GA) via live video link, whereby alternative fixation options, instrumentation, additional hardware and closure techniques were exchanged.

The operative procedure was conducted by utilizing percutaneous K-wires to match the orientation of the multiplane wedge resection simulated. Once this was in place, the sequential resection performed and reduction was achieved. Additional internal fixation was implanted and the external Ilizarov construct was applied with minimal modification.

The techniques described are evolutionary advances to current surgical planning and preparation. The integration of open source software solutions with DIY hardware hacking and Reprap technology will continue to demonstrate feasible improvements to quality of care and reduction of cost in the post-modern medical era. More to come? The second phase are printing biocompatable “parts” just as recent advances in solid organ “printing” have shown.

-Nicholas Giovinco and David G. Armstrong