3D patient-specific surgical printing cutting blocks guides and spacers for open- wedge high tibial osteotomy (HTO) - do it yourself

Abstract

Introduction Opening wedge osteotomy has recently gained popularity, thanks to the recent implementation of locking plates, which have shown equivalent stability with greater reproducibility, accuracy, and longevity than the closing wedge techniques and a lower prosthetic conversion rate. The two most important factors for success in opening HTO success are proper patient selection and correction accuracy of the mechanical axis. This accuracy depends on two basic steps- proper preoperative planning and precise surgical reproducibility. Based on digital image planification, we present a new “do-it-yourself” 3D cutting guides system. Material planification of the desired correction was performed using lower limb weight bearing digital xray and orthoview software. Based on a conventional CT scan, DICOM images were then imported into the radiological post-processing software (OsiriX). A positioning guide for Kirschner wires and wedge spacers were printed in three dimensions (Da Vinci, XYZ Printing) for facilitating the osteotomy and obtaining the planned correction. The surgeon makes the whole process in a do-it-yourself style. This new technique was used in a pilot feasibility study in eight patients. Previous opening osteotomies with the standard technique were used as control (20 cases). Surgical time, fluoroscopic time, cost and accuracy of the axial correction were measured. Results The use of a custom positioning guide reduced the surgical (31 minutes less) and fluoroscopic times (6.9 times less) while achieving a high-axis correction accuracy compared with the standard technique. Digitally planned and executed osteotomies under 3D printed osteotomy positioning guides help the surgeon to minimize human error while reducing surgical time. Once acquired the printer, the increase in cost is mostly due to the scanner expenses (150 euros) and the printed material (6 euros per set). Discussion Several techniques based on intraoperative navigation have shown an increased surgical accuracy in HTO for modifying axial alignment and for controlling tibial slope on the sagittal plane, with respect to classic techniques based on anatomic landmarks and introperative fluoroscopy. The main disadvantage of navigation is the long learning curve, coupled with increased surgical time. The 3D-guided technique allows for a more precise preoperative planning, a simpler and faster surgical technique with no learning curve and an accurate correction of the mechanical axis. In confront to the standard technique, it lowers exposure to radiation (6.9 times). Potential benefits related with shorter surgical time are a reduced blood loss and lower infection rates. At our institution, the reduction in surgical time represents a difference in costs of 507 euros per operation. Conclusion The reproducibility of this technique is very robust, allowing a transfer of the steps planned in a virtual environment to the operating table with non-negligible benefits.