JUNE 2022 | The Surgical Technologist | 273 fracture reduction with an average residual displacement of 7 degrees versus 26 degrees in the control [232]. In the case of distal radius fractures, 3D-printed patient-specific plates have been found to have higher yield strength than traditional plates, 1043N versus 876N, respectively. The higher yield strength in the 3D-printed plates is theorized to occur due to better mechanical properties of titanium alloy powder or the 3D plate’s ability to contour better the patient’s bony anatomy allowing for better screw purchase [233]. 3D-printed models of patient-specific anatomy can be used to prebend plates. An article out of Chunbgbuk South Korea discusses a technique for using 3D-printed models of fractures to allow for prebending plates for clavicle fractures [234]. These 3D-printed clavicle plates allow for enhanced plate contouring of each patient’s unique clavicle geometry, which can have substantial variation based on gender and race. Also, this technique allows for more straightforward fracture reduction, minimizing soft tissue dissection. The application of 3D-printed patient-specific instrumentation (PSI) for total shoulder arthroplasty has been shown to improve precision and reduce the incidence of component malposition [235–237]. Although many factors influence the functional life of a prosthetic shoulder, suboptimal positioning of the glenoid component has a significant correlation with the risk of implant failure [238]. PSI and custom prosthesis facilitate a reproducible way to improve the accuracy of implant placement, particularly in the setting of severe deformity and bone loss. In a multisurgeon cadaveric study by Throckmorton et al., shoulders with radiographically confirmed osteoarthritis was randomized to PSI or standard instrumentation for anatomic and reverse TSA. Although no difference was found in reverse TSA, in anatomic TSA, PSI improved mean deviation in version from 8 to 5 degrees and inclination from 7 to 3 degrees. Additional clinical outcome studies are needed to define the cost-effectiveness of such technology [239]. 3.5.2. Lower Extremities. The role of 3DP in lower extremity orthopaedic surgery cannot be understated [240]. Within just a few decades, 3DP has come to play a substantial role in the pre-, intra-, and postoperative stages of treatment in orthopaedics (Figure 10). 3DP provides surgeons with patient-specific anatomic models, enabling extremely precise preoperative planning including optimization of the surgical approach, planning placement of reduction clamps and implants, and the need for additional resources to be used intraoperatively [241–243]. These models accentuate bone defects poorly conceptualized with 2D imaging, allowing surgeons to precisely address the damaged bone and/or cartilage defects and provide the advantage of touch which recalibrates visual perception, enabling a more comprehensive understanding of the clinical problem [242, 244–246]. These models have successfully been used in complex pelvic and acetabular trauma, distal femoral fractures, and distal femoral osteotomies, and have been found to reduce radiation exposure and the risk of iatrogenic neurovascular complications [246–249]. In addition, 3DP simulations and models assist with implant positioning in revision total hip arthroplasty (THA) with complex acetabular defect, with moderate to high accuracy, and satisfied clinical outcome [250]. A large contribution from 3DP has been personalized implants, unique not only to patient’s anatomy, but customizable in terms of microstructures (i.e., porosity) and physical properties [251]. 3DP implants are lighter and more comfortable to the patient and can also facilitate minimally invasive surgery [242, 243, 252, 253]. In addition, some implants, like precountered plates, have the added benefit of reducing surgical time and blood loss and improved fit in trauma cases [254]. One of the best-known implants in arthroplasty is the custom triflange which is a patientspecific implant for the treatment of severe bone loss in total hip revisions [246, 255–257]; however, custom knee implants are also used in primary total and partial knee arthroplasty and in patients with previous displaced tibial plateau fractures [256–258]. 3DP additionally can create high-resolution bone graft, allowing for exquisite control of porosity and bone interconnectivity, both of which are essential for regeneration and osteointegration [251]. This technology allows, for instance, in situ repair of osteochondral defects through autologous implantation of chondrocytes and bone marrow cells using scaffolds [259]. It also allowed for the incorporation of metallic particles and bone growth proteins into bone graft, which has been shown in animal studies to promote regeneration [260, 261]. Beyond bone graft and personalized implants, preoperative models themselves additionally have the potential to be sterilized and be use intraoperatively, as has been done in complex periacetabular trauma injuries [262, 263]. Other intraoperative 3DP tools have included personalized locking and cutting guides for standard total knee replacements, ACL femoral tunnel guides, and intraoperative models for tibial plateau fractures, distal tibial fractures, talar fractures, and deformity correction [241, 242]. Personalized instruments for pelvic tumor cases have also been found to improve accuracy in simulated surgeries, in addition to Figure 10: Surgical correction of valgus knees through the use of osteotomy procedure, which consist in the removal or insertion of a wedge of bone near a damaged cartilage in order to provide a well-distributed weight area over the affected knee. Four 3Dprinted Kirschner wires are inserted through the guide. Depth and orientation checked under fluoroscopy [249]. Used with permission from Elsevier. 15 BioMed Research International The practice of space medicine also relies on the Crew Health Care System, essential for ensuring crewmember health and safety, including Countermeasures System, Environmental Health System, and Health Maintenance System. Upcoming missions beyond LEO are planned based on the perceived threat level to health or life of an operation and the identified levels of care needed, on which planning of the medical support is based [286]. Surgery in space is thought possible in missions with a level of care four or higher rating, such as in crewed LEO missions and lunar/ planetary surface exploration, when lasting more than 30 days. A wide variety of surgical procedures have already been conducted during simulated zero gravity parabolic flights [286]. Nonetheless, there are challenges to performing surgery in a microgravity environment, especially in deep space missions, which includes surgical and anaesthetic procedures and techniques, and ongoing crewmember training to maintain surgical skills throughout a mission [287]. Although space surgery is a high interest area, there is a current lack of validated devices, procedures, and training. Moreover, existing levels of care are built on data from an astronaut population only, not considering potential health issues arising from commercial astronauts or space tourists. The medical history and training of these latter groups are extremely variable; meaning, an equivalent level of care for commercial activity may require surgery as a need/option for shorter missions. Simulated crewed space missions, known as analogue missions, offer a controlled environment for recreating scenarios where surgery may be fundamental, such as medical emergencies [288]. The possibility of applying space robotic surgery might be impractical, due to the size, weight, and time-sensitive 3D Printing AR VR Left Figure 11: Examples of 3D printing (top), AR (middle), and VR (bottom) technologies. Top row: Stratasys J750 Digital Anatomy Printer; 3D printed kidney tumor model with the kidney in clear, collecting system (semi-transparent), lesi (purple), re al artery (pink), renal vein (light blue), and collecting system (dark blue); 3D printed prostate cancer model with the pr state lear, lesion—blu , neu vascul r bundle (yellow), rectal wall (white), bladder neck, and ur thr (pink). Middl row: HoloLens-AR headset; AR kidney tumor model s own projected in a room with the kidney (pink), tumor (gray), artery (r d), vein (blue), and collecting system (yellow); prost te can er model shown projected in a roo with the prostate (transparent), lesions (blue), neurovascular bundles (purple), bladder neck, and collecting syste (yellow). Bottom row: person wearing HTC Vive VR headset; kidney tumor model; prostate cancer model configuration colours as at the middle row picture, also with arterial supply (red) [274]. Used with permission from Elsevier. Figure 12: 3D printed instruments for space surgery applications [290]. Used with permission from Elsevier. 17 BioMed Research International
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