In the last years, 3d printing has progressively grown and it has reached a solid role in clinical practice. The main applications brought by 3d printing in orthopedic surgery are: preoperative planning, custom-made surgical guides, custom-made im- plants, surgical simulation, and bioprinting. The replica of the patient's anatomy, starting from the elaboration of medical volumetric images (CT, MRI, etc.), allows a progressive extremization of treatment personalization that could be tailored for every single patient. In complex cases, the generation of a 3d model of the patient's anatomy allows the surgeons to better understand the case — they can almost “touch the anatomy” —, to perform a more ac- curate preoperative planning and, in some cases, to perform device positioning before going to the surgical room (i.e. joint arthroplasty). 3d printing is also commonly used to produce surgical cutting guides, these guides are positioned intraoperatively on given landmarks to guide the surgeon to perform a specific surgical act (bone osteotomy, bone resection, implant position, etc.). In total knee arthroplasty, custom-made cutting guides have been developed to help the surgeon align the femoral and tibial components to the pre-arthritic condition with- out the use of the intramedullary femoral guide. 3d printed custom-made implants represent an emerging alternative to biological reconstructions especially after oncologic resection surgery or in case of complex arthroplasty revision surgery. Custom-made implants are designed to re- place the original shape and size of the patient's bone and they allow an extreme personalization of the treatment for every single patient. Patient-specific surgical simulation is a new frontier that promises great benefits for surgical training. a solid 3d model of the patient's anatomy can faithfully reproduce the surgical complexity of the patient and it allows to generate surgical simulators with increasing difficulty to adapt the difficulties of the course with the level of the trainees performing structured training paths: from the “simple” case to the “complex” case

Paediatric musculoskeletal (MSK) disorders often produce severe limb deformities, that may require surgical correction. This may be challenging, especially in case of multiplanar, multifocal and/or multilevel deformities. The increasing implementation of novel technologies, such as virtual surgical planning (VSP), computer aided surgical simulation (CASS) and 3D-printing is rapidly gaining traction for a range of surgical applications in paediatric orthopaedics, allowing for extreme personalization and accuracy of the correction, by also reducing operative times and complications. However, prompt availability and accessible costs of this technology remain a concern. Here, we report our experience using an in-hospital low-cost desk workstation for VSP and rapid prototyping in the field of paediatric orthopaedic surgery. From April 2018 to September 2022 20 children presenting with congenital or post-traumatic deformities of the limbs requiring corrective osteotomies were included in the study. A conversion procedure was applied to transform the CT scan into a 3D model. The surgery was planned using the 3D generated model. The simulation consisted of a virtual process of correction of the alignment, rotation, lengthening of the bones and choosing the level, shape and direction of the osteotomies. We also simulated and calculated the size and position of hardware and customized massive allografts that were shaped in clean room at the hospital bone bank. Sterilizable 3D models and PSI were printed in high-temperature poly-lactic acid (HTPLA), using a low-cost 3D-printer. Twenty-three operations in twenty patients were performed by using VSP and CASS. The sites of correction were: leg (9 cases) hip (5 cases) elbow/forearm (5 cases) foot (5 cases) The 3D printed sterilizable models were used in 21 cases while HTPLA-PSI were used in five cases. customized massive bone allografts were implanted in 4 cases. No complications related to the use of 3D printed models or cutting guides within the surgical field were observed. Post-operative good or excellent radiographic correction was achieved in 21 cases. In conclusion, the application of VSP, CASS and 3D-printing technology can improve the surgical correction of complex limb deformities in children, helping the surgeon to identify the correct landmarks for the osteotomy, to achieve the desired degree of correction, accurately modelling and positioning hardware and bone grafts when required. The implementation of in-hospital low-cost desk workstations for VSP, CASS and 3D-Printing is an effective and cost-advantageous solution for facilitating the use of these technologies in daily clinical and surgical practice

The medial opening-wedge high tibial osteotomy (OW-HTO) is an accepted option to treat the isolated medial compartment osteoarthritis (OA) in varus knee. Despite satisfactory outcomes were described in literature, consistent complication rate has been reported and the provided accuracy of coronal alignment correction using conventional HTO techniques falls short. Patient specific instrumentations has been introduced with the aim to reduce complications and to improve the intra-operative accuracy according to the pre-operative plan, which is responsible for the clinical result of the surgery. In this talk, an overview of the clinical results of HTO patient specific instrumentation available in literature will be performed. Moreover, preliminary intra-operative and clinical results of a new customised 3-D printed cutting guide and fixation plate for OW-HTO will be presented

Reconstructing mandibular and maxillary bone defects with free vascularized bone flaps requires to take into account the aesthetic and functional requirements to consider subsequent placement of dental implants. It implies a three-dimensional conformation of the bone fragment. This is usually done by making osteotomies on the bone harvested. The aim of our study was to evaluate the interest of virtual planning and 3D printing using free software and a consumer printer in this indication. Invesalius® software (Technology of Information Renato Archer Center, Campinas, Brazil) was used to build virtual models from the patients' CT scan imaging data. The surgical procedure was planned using Meshmixer® (Autodesk, San Rafael, United States). Meshlab® software (Visual Computing Lab, Pisa, Italy) was used to design cutting guides for the flap harvest and modelling. 3D printing of these guides with a consumer printer (Ultimaker 2® Ultimaker B.V., Geldermalsen, the Netherlands) allowed the transfer of the planning to the operating room. Three patients requiring mandibular reconstruction underwent an iliac crest free flap, a fibula free flap and a scapula free flap, and could benefit from this technique. In each case, the bone resection was performed virtually and the positioning of the bone available at the donor site was simulated on screen. This allowed to anticipate the position and orientation of the cutting planes on the bone flap. From the anatomy of the donor site and the cutting planes, harvest templates and cutting guides could be designed by computer. Planning the conformation of the bone flap to the recipient site has allowed an anatomical, aesthetic and functional reconstruction of the bone defect. Surgeon-made virtual planning and “low cost” 3D printing helps harvest the bone flap and position and orient the osteotomies to adapt it to the defect. They provide, both the patient and the surgeon, reduced operative time and better anticipation of the result, particularly in the context of the maxillofacial reconstruction. Compared to commercially available custom-made devices, this technique allows the manufacture of the guides without delay and at a cheap price

Objectives. Unicompartmental knee arthroplasty (UKA) is a demanding procedure, with tibial component subsidence or pain from high tibial strain being potential causes of revision. The optimal position in terms of load transfer has not been documented for lateral UKA. Our aim was to determine the effect of tibial component position on proximal tibial strain. Methods. A total of 16 composite tibias were implanted with an Oxford Domed Lateral Partial Knee implant using cutting guides to define tibial slope and resection depth. Four implant positions were assessed: standard (5° posterior slope); 10° posterior slope; 5° reverse tibial slope; and 4 mm increased tibial resection. Using an electrodynamic axial-torsional materials testing machine (Instron 5565), a compressive load of 1.5 kN was applied at 60 N/s on a meniscal bearing via a matching femoral component. Tibial strain beneath the implant was measured using a calibrated Digital Image Correlation system. Results. A 5° increase in tibial component posterior slope resulted in a 53% increase in mean major principal strain in the posterior tibial zone adjacent to the implant (p = 0.003). The highest strains for all implant positions were recorded in the anterior cortex 2 cm to 3 cm distal to the implant. Posteriorly, strain tended to decrease with increasing distance from the implant. Lateral cortical strain showed no significant relationship with implant position. Conclusion. Relatively small changes in implant position and orientation may significantly affect tibial cortical strain. Avoidance of excessive posterior tibial slope may be advisable during lateral UKA. Cite this article: A. M. Ali, S. D. S. Newman, P. A. Hooper, C. M. Davies, J. P. Cobb. The effect of implant position on bone strain following lateral unicompartmental knee arthroplasty: A Biomechanical Model Using Digital Image Correlation. Bone Joint Res 2017;6:522–529. DOI: 10.1302/2046-3758.68.BJR-2017-0067.R1

The aim of this project is to test the parameters of Patient Specific Instruments (PSIs) and measuring accuracy of surgical cuts using sawblades with different depths of PSI cutting guide slot. Clear operative oncological margins are the main target in malignant bone tumour resections. Novel techniques like patient specific instruments (PSIs) are becoming more popular in orthopaedic oncology surgeries and arthroplasty in general with studies suggesting improved accuracy and reduced operating time using PSIs compared to conventional techniques and computer assisted surgery. Improved accuracy would allow preservation of more natural bone of patients with smaller tumour margin. Novel low-cost technology improving accuracy of surgical cuts, would facilitate highly delicate surgeries such as Joint Preserving Surgery (JPS) that improves quality of life for patients by preserving the tibial plateau and muscle attachments around the knee whilst removing bone tumours with adequate tumour margins. There are no universal guidelines on PSI designs and there are no studies showing how specific design of PSIs would affect accuracy of the surgical cuts. We hypothesised if an increased depth of the cutting slot guide for sawblades on the PSI would improve accuracy of cuts. A pilot drybone experiment was set up, testing 3 different designs of a PSI with changing cutting slot depth, simulating removal of a tumour on the proximal tibia. A handheld 3D scanner (Artec Spider, Luxembourg) was used to scan tibia drybones and Computer Aided Design (CAD) software was used to simulate osteosarcoma position and plan intentioned cuts. PSI were designed accordingly to allow sufficient tumour. The only change for the 3 designs is the cutting slot depth (10mm, 15mm & 20mm). 7 orthopaedic surgeons were recruited to participate and perform JPS on the drybones using each design 2 times. Each fragment was then scanned with the 3D scanner and were then matched onto the reference tibia with customized software to calculate how each cut (inferior-superior-vertical) deviated from plan in millimetres and degrees. In order to tackle PSI placement error, a dedicated 3D-printed mould was used. Comparing actual cuts to planned cuts, changing the height of the cutting slot guide on the designed PSI did not deviate accuracy enough to interfere with a tumour resection margin set to maximum 10mm. We have obtained very accurate cuts with the mean deviations(error) for the 3 different designs were: [10mm slot: 0.76 ± 0.52mm, 2.37 ± 1.26°], [15 mm slot: 0.43 ± 0.40 mm, 1.89 ± 1.04°] and [20 mm: 0.74 ± 0.65 mm, 2.40 ± 1.78°] respectively, with no significant difference between mean error for each design overall, but the inferior cuts deviation in mm did show to be more precise with 15 mm cutting slot (p<0.05). Simulating a cut to resect an osteosarcoma, none of the proposed designs introduced error that would interfere with the tumour margin set. Though 15mm showed increased precision on only one parameter, we concluded that 10mm cutting slot would be sufficient for the accuracy needed for this specific surgical intervention. Future work would include comparing PSI slot depth with position of knee implants after arthroplasty, and how optimisation of other design parameters of PSIs can continue to improve accuracy of orthopaedic surgery and allow increase of bone and joint preservation

After the first big hype on additive manufacturing in medical industry the technology of 3D printing is now reaching a productive stage for some selected applications. These applications range from surgical models for visualisation to patient-specific cutting guides and 3D printed orthopaedic implants. This presentation will guide through current 3D printing applications in medical devices. We will show success stories for products in some of these fields and try to point out to a potential future of fully personalized orthopaedics in polymer and metals. A regulatory view on all aspects of 3D printing will be presented and potential hurdles to expand the full potential of medical device 3D printing

Objectives

This study reports on a secondary exploratory analysis of the early clinical outcomes of a randomised clinical trial comparing robotic arm-assisted unicompartmental knee arthroplasty (UKA) for medial compartment osteoarthritis of the knee with manual UKA performed using traditional surgical jigs. This follows reporting of the primary outcomes of implant accuracy and gait analysis that showed significant advantages in the robotic arm-assisted group.