In-House, Fast FDM Prototyping of a Custom Cutting Guide for a Lower-Risk Pediatric Femoral Osteotomy

In vitro comparative study of deformation of 3D-printed models using different polylactic acids treated by steam sterilization

INTRODUCTION

3D printing, which is becoming ever more widespread in orthopedic surgery, requires specific materials. Polylactic acid (PLA) is the most widely used in general-purpose 3D printing, but its thermosensitivity can be incompatible with sterilization. Even so, it is easy to use, inexpensive, non-toxic and biodegradable. Controversy surrounds its use. 3D printing of directly sterilizable PLA parts according to surgeons' needs would be highly advantageous, but doubts remain. We therefore performed an in vitro study to determine which PLAs resist steam sterilization regarding deformation.

HYPOTHESIS

The study hypothesis was that, depending on make and shape, 3D-printed PLA parts can retain their properties after steam sterilization.

MATERIAL AND METHODS

We selected 4 makes of PLA and used each to print 4 simple cubes and 4 complex shapes corresponding to cuboid bones. They were subjected to steam sterilization under normal French hospital conditions. The size of the cubes was measured before and after sterilization, using a digital caliper.

RESULTS

Cuboid parts in HT-PLA and PLA-WANAO showed mean deformation of -0.02mm and -0.4mm, respectively after sterilization, the differences being non-significant (p=0.679 and p=0.241, respectively). Cuboid parts in PLA-SUNLU and PLA-G3D showed significant mean deformation: respectively, -1.37mm (p=0.026) and -35.03mm (p>0.001). Cubes in all types of PLA showed significant mean deformation: HT-PLA, -0.61mm (p=0.004); PLA-SUNLU, -2.70mm (p=0.002); PLA-G3D, -28.64mm (p>0.001); and PLA-WANAO, -1.33mm (p=0.010).

DISCUSSION

The study confirmed recent findings that steam sterilization is feasible with certain PLA-printed parts, with deformations less than 1mm, and that choice of PLA is crucial for success. Computer-designed objects (here, cubes) did not resist sterilization without significant deformation. Analysis of resistance to various stresses was not performed, and therefore it cannot be claimed that the process could be used other than for printing anatomic parts. Use of 3D printing in French hospitals is probably a real source of innovation and improvement in care quality; however, a legal framework needs establishing for the use of 3D-printed parts, to ensure patient safety and promote research in this field.

LEVEL OF EVIDENCE

III; prospective in vitro study.

Clinical Applications of "In-Hospital" 3D Printing in Hip Surgery: A Systematic Narrative Review

Introduction: Interest in 3D printing for orthopedic surgery has been increasing since its progressive adoption in most of the hospitals around the world. The aim of the study is to describe all the current applications of 3D printing in patients undergoing hip surgery of any type at the present time. Materials and Methods: We conducted a systematic narrative review of publications indexed in MedLine through the search engine PubMed, with the following parameters: 3D printing AND (orthopedics OR traumatology) NOT tissue engineering NOT scaffold NOT in vitro and deadline 31 July 2023. After reading the abstracts of the articles, papers were selected according to the following criteria: full text in English or Spanish and content related to hip surgery. Those publications involving experimental studies (in vitro or with anatomical specimens) or 3D printing outside of hospital facilities as well as 3D-printed commercial implants were excluded. Results are presented as a reference guide classified by disease, including the used software and the steps required for the development of the idea. Results: We found a total of 27 indications for in-house 3D printing for hip surgery, which are described in the article. Conclusions: There are many surgical applications of 3D printing in hip surgery, most of them based on CT images. Most of the publications lack evidence, and further randomized studies should be encouraged to assess the advantages of these indications.

Stress-Based Lattice Structure Design for a Motorbike Application

Background

The "drive by wire" mechanism for managing the throttle is not applied to every modern motorcycle, but it is often managed through a steel wire. Here, there is a cam on the throttle control. Its shape allows the throttle opening to be faster or slower and its angle of rotation, required for full opening, to be greater or less. The maximum angle a rider's wrist can withstand depends on numerous musculoskeletal mobility factors, often limited by falls or surgery.

Methods

Using a Progrip knob with interchangeable cams allows the customization of a special cam profile, to ensure the best engine response to throttle rotation and ergonomics for the rider. The use of FEA software and lattice structures, allows to realize a lightweight and efficient design, targeted for fabrication with additive manufacturing technologies.

Results

The cam was manufactured by exploiting MSLA technology. Finally, a dimensional inspection procedure was performed before assembly. The main result is to have obtained a lighter and cheaper component than the original.

Conclusions

This study has allowed the design of a mechanical component consisting of innovative shape, light weight, and ergonomics. Furthermore, it demonstrates the effectiveness in the use of lattice structures to enable weight optimization of a component while minimizing the increase in its compliance.

3D printing for bone regeneration: challenges and opportunities for achieving predictability

3D printing offers attractive opportunities for large-volume bone regeneration in the oro-dental and craniofacial regions. This is enabled by the development of CAD-CAM technologies that support the design and manufacturing of anatomically accurate meshes and scaffolds. This review describes the main 3D-printing technologies utilized for the fabrication of these patient-matched devices, and reports on their pre-clinical and clinical performance including the occurrence of complications for vertical bone augmentation and craniofacial applications. Furthermore, the regulatory pathway for approval of these devices is discussed, highlighting the main hurdles and obstacles. Finally, the review elaborates on a variety of strategies for increasing bone regeneration capacity and explores the future of 4D bioprinting and biodegradable metal 3D printing.

Current Concepts in the Resection of Bone Tumors Using a Patient-Specific Three-Dimensional Printed Cutting Guide

Orthopedic oncology has begun to use three-dimensional-printing technology, which is expected to improve the accuracy of osteotomies, ensure a safe margin, and facilitate precise surgery. However, several difficulties should be considered. Cadaver and clinical studies have reported more accurate osteotomies for bone-tumor resection using patient-specific cutting guides, especially in challenging areas such as the sacrum and pelvis, compared to manual osteotomies. Patient-specific cutting guides can help surgeons achieve resection with negative margins and reduce blood loss and operating time. Furthermore, this patient-specific cutting guide could be combined with more precise reconstruction using patient-specific implants or massive bone allografts. This review provides an overview of the basic technologies used in the production of patient-specific cutting guides and discusses their current status, advantages, and limitations. Moreover, we summarize cadaveric and clinical studies on the use of these guides in orthopedic oncology.

The Flipping-Wedge Osteotomy: How 3D Virtual Surgical Planning (VSP) Suggested a Simple and Promising Type of Osteotomy in Pediatric Post-Traumatic Forearm Deformity

(1) Background: The application of computer-aided planning in the surgical treatment of post-traumatic forearm deformities has been increasingly widening the range of techniques over the last two decades. We present the “flipping-wedge osteotomy”, a promising geometrical approach to correct uniapical deformities defined during our experience with virtual surgical planning (VSP); (2) Methods: a case of post-traumatic distal radius deformity (magnitude 43°) treated with a flipping-wedge osteotomy in an 11-year-old girl is reported, presenting the planning rationale, its geometrical demonstration, and the outcome of the procedure; (3) Results: surgery achieved correction of both the angular and rotational deformities with a neutral ulnar variance; (4) Conclusions: flipping-wedge osteotomy may be a viable option to achieve correction in forearm deformities, and it deserves further clinical investigation.

Development of Nanocoated Filaments for 3D Fused Deposition Modeling of Antibacterial and Antioxidant Materials

Three-dimensional (3D) printing is one of the most futuristic manufacturing technologies, allowing on-demand manufacturing of products with highly complex geometries and tunable material properties. Among the different 3D-printing technologies, fused deposition modeling (FDM) is the most popular one due to its affordability, adaptability, and pertinency in many areas, including the biomedical field. Yet, only limited amounts of materials are commercially available for FDM, which hampers their application potential. Polybutylene succinate (PBS) is one of the biocompatible and biodegradable thermoplastics that could be subjected to FDM printing for healthcare applications. However, microbial contamination and the formation of biofilms is a critical issue during direct usage of thermoplastics, including PBS. Herein, we developed a composite filament containing polybutylene succinate (PBS) and lignin for FDM printing. Compared to pure PBS, the PBS/lignin composite with 2.5~3.5% lignin showed better printability and antioxidant and antimicrobial properties. We further coated silver/zinc oxide on the printed graft to enhance their antimicrobial performance and obtain the strain-specific antimicrobial activity. We expect that the developed approach can be used in biomedical applications such as patient-specific orthoses.

Custom Massive Allograft in a Case of Pelvic Bone Tumour: Simulation of Processing with Computerised Numerical Control vs. Robotic Machining

The use of massive bone allografts after the resection of bone tumours is still a challenging process. However, to overcome some issues related to the processing procedures and guarantee the best three-dimensional matching between donor and recipient, some tissue banks have developed a virtual tissue database based on the scanning of the available allografts for using their 3D shape during virtual surgical planning (VSP) procedures. To promote the use of future VSP bone-shaping protocols useful for machining applications within a cleanroom environment, in our work, we simulate a massive bone allograft machining with two different machines: a four-axes (computer numerical control, CNC) vs. a five-axes (robot) milling machine. The allograft design was based on a real case of allograft reconstruction after pelvic tumour resection and obtained with 3D Slicer and Rhinoceros software. Machining simulations were performed with RhinoCAM and graphically and mathematically analysed with CloudCompare and R, respectively. In this case, the geometrical differences of the allograft design are not clinically relevant; however, the mathematical analysis showed that the robot performed better than the four-axes machine. The proof-of-concept presented here paves the way towards massive bone allograft cleanroom machining. Nevertheless, further studies, such as the simulation of different types of allografts and real machining on massive bone allografts, are needed.

Basic Considerations and Conceptual Design of a VSTOL Vehicle for Urban Transportation

On-demand air transport is an air-taxi service concept that should ideally use small, autonomous, Vertical Short Takeoff and Landing (VSTOL), “green”, battery-powered electric aircraft (eVSTOL). In addition, these aircraft should be competitive with modern helicopters, which are exceptionally reliable machines capable of the same task. For certification and economic purposes, mobile tilting parts should be avoided. The concept introduced in this paper simplifies the aircraft and makes it economical to build, certify and maintain. Four contrarotating propellers with eight electric motors are installed. During cruise, only two of the eight rotors available are not feathered and active. In the first step, a commercial, certified, jet-fueled APU and an available back-up battery are used. A second solution uses a CNG APU and the same back-up battery. Finally, the third solution has a high-density dual battery that is currently not available. A conceptual design is shown in this paper.

How to Sterilize Polylactic Acid Based Medical Devices?

How sterilization techniques accurately affect the properties of biopolymers continues to be an issue of discussion in the field of biomedical engineering, particularly now with the development of 3D-printed devices. One of the most widely used biopolymers in the manufacture of biomedical devices is the polylactic acid (PLA). Despite the large number of studies found in the literature on PLA devices, relatively few papers focus on the effects of sterilization treatments on its properties. It is well documented in the literature that conventional sterilization techniques, such as heat, gamma irradiation and ethylene oxide, can induced damages, alterations or toxic products release, due to the thermal and hydrolytical sensitivity of PLA. The purposes of this paper are, therefore, to review the published data on the most common techniques used to sterilize PLA medical devices and to analyse how they are affecting their physicochemical and biocompatible properties. Emerging and alternative sterilization methods for sensitive biomaterials are also presented.