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Aim of this study was to prove the possibility of manufacturing patient specific root analogue two-part (implant and abutment) implants by direct metal laser sintering. The two-part implant design enables covered healing of the implant. Therefore, CT-scans of three patients are used for reverse engineering of the implants, abutments and crowns. Patient specific implants are manufactured and measured concerning dimensional accuracy and surface roughness. Impacts of occlusal forces are simulated via FEA and compared to those of standard implants.

Abstract Background Conventional knee and hip implant systems have been in use for many years with good success. However, the custom design of implant components based on patient-specific anatomy has been attempted to overcome existing shortcomings of current designs. The longevity of cementless implant components is highly dependent on the initial fit between the bone surface and the implant. The bone-implant interface design has historically been limited by the surgical tools and cutting guides available; and the cost of fabricating custom-designed implant components has been prohibitive. Methods This paper describes an approach where the custom design is based on a Computed Tomography scan of the patient's joint. The proposed design will customize both the articulating surface and the bone-implant interface to address the most common problems found with conventional knee-implant components. Finite Element Analysis is used to evaluate and compare the proposed design of a custom femoral component with a conventional design. Results The proposed design shows a more even stress distribution on the bone-implant interface surface, which will reduce the uneven bone remodeling that can lead to premature loosening. Conclusion The proposed custom femoral component design has the following advantages compared with a conventional femoral component. (i) Since the articulating surface closely mimics the shape of the distal femur, there is no need for resurfacing of the patella or gait change. (ii) Owing to the resulting stress distribution, bone remodeling is even and the risk of premature loosening might be reduced. (iii) Because the bone-implant interface can accommodate anatomical abnormalities at the distal femur, the need for surgical interventions and fitting of filler components is reduced. (iv) Given that the bone-implant interface is customized, about 40% less bone must be removed. The primary disadvantages are the time and cost required for the design and the possible need for a surgical robot to perform the bone resection. Some of these disadvantages may be eliminated by the use of rapid prototyping technologies, especially the use of Electron Beam Melting technology for quick and economical fabrication of custom implant components.

Introduction: Caudal maxillectomies are challenging procedures for most veterinary surgeons. Custom guides may allow the procedure to become more accessible., Methods: A cadaveric study was performed to evaluate the accuracy and efficiency of stereolithography guided (3D-printed) caudal maxillectomy. Mean absolute linear deviation from planned to performed cuts and mean procedure duration were compared pairwise between three study groups, with 10 canine cadaver head sides per group: 3D-printed guided caudal maxillectomy performed by an experienced surgeon (ESG) and a novice surgery resident (NSG), and freehand procedure performed by an experienced surgeon (ESF)., Results: Accuracy was systematically higher for ESG versus ESF, and statistically significant for 4 of 5 osteotomies ( p < 0.05). There was no statistical difference in accuracy between ESG and NSG. The highest absolute mean linear deviation for ESG was <2 mm and >5 mm for ESF. Procedure duration was statistically significantly longer for ESG than ESF ( p < 0.001), and for NSG than ESG ( p < 0.001)., Discussion: Surgical accuracy of canine caudal maxillectomy was improved with the use of our novel custom cutting guide, despite a longer duration procedure. Improved accuracy obtained with the use of the custom cutting guide could prove beneficial in achieving complete oncologic margins. The time increase might be acceptable if hemorrhage can be adequately controlled in vivo . Further development in custom guides may improve the overall efficacy of the procedure., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Chambers, Traverson, Neal, Konala and Harrysson.)

Objective: To assess the accuracy of three-dimensionally (3-D) printed drill guides in constraining the trajectory of drill tracts for implants in canine thoracic vertebrae., Study Design: Experimental ex vivo study., Sample Population: Five canine thoracic vertebral column specimens., Methods: Guides to constrain drill trajectories were designed on the basis of computed tomographic (CT) imaging of six thoracic vertebrae (T8-T13) and were 3-D printed. The guides were used to create drill tracts in these vertebrae by both an experienced and a novice surgeon, and CT imaging was repeated. The entry point and angulation of actual and planned drill tracts were compared for both surgeons. Unintended cortical violations were also assessed by using a modified Zdichavsky classification., Results: Fifty-eight drill tracts were created in 30 vertebrae. Mean entry point deviation was 1.4 mm (range, 0.4-3.4), and mean angular deviation was 5.1° (range, 1.5°-10.8°). There were no differences between surgeons in entry point deviation (P = .07) or angular deviation (P = .22). There were no unintended cortical bone violations, and all drill tracts were classified as modified Zdichavsky grade I., Conclusion: The 3-D printed guides used in the current study yielded drill tracts with small linear and angular errors from intended paths and 100% accuracy for placement within vertebral pedicles and bodies. This technique was conveniently used by both an experienced and a novice surgeon., Clinical Significance: This technique might be immediately applicable to clinical cases requiring thoracic vertebral stabilization and may allow safe and accurate implant placement for surgeons with varying experience levels., (© 2020 The American College of Veterinary Surgeons.)

Objectives: Osseointegrated prostheses are increasingly used for amputees, however, the lengthy rehabilitation time of these prostheses remains a challenge to their implementation. The aim of this study was to investigate the ability of locally applied vibration or low-intensity pulsed ultrasound (LIPUS) to accelerate osseointegration and increase peri-implant bone volume., Methods: A 4-week and 8-week rodent study were conducted in a femoral intramedullary implant model (control, vibration, LIPUS, and combined treatment) to determine effects on healing. Osseointegration was evaluated quantitatively through mechanical, µCT and histological evaluations., Results: Maximum pushout load at 4 weeks increased with LIPUS relative to control (37.7%, P=0.002). Histologically, LIPUS and vibration separately increased peri-implant bone formation after 4 weeks relative to control. Vibration resulted in greater peri-implant bone after 8 weeks than all other groups (25.7%, P<0.001). However, no significant group differences in pushout load were noted at 8 weeks., Conclusions: Although vibration increased bone around implants, LIPUS was superior to vibration for accelerating osseointegration and increasing bone-implant failure loads at 4 weeks. However, the LIPUS benefits on osseointegration at 4 weeks were not sustained at 8 weeks.

Objective: This study assessed femur properties in 80 adult female rats exposed to a range of whole body vibration amplitudes at 45 Hz over five weeks. Our hypothesis was that an optimal amplitude for whole body vibration would be apparent and would result in increased bone strength., Methods: Animals were treated in five amplitude groups (0 g, 0.15 g, 0.3 g, 0.6 g, and 1.2 g peak), for 15 minutes per day, five days per week, for five weeks. Femur strength was assessed via: (1) three-point bending of the shaft, (2) cantilever bending of the neck, and (3) indentation of distal cancellous bone. Femoral bone mineral density, plasma prostaglandin E2 (PGE 2 ) concentrations, cartilage thickness, and histopathologic properties were measured., Results: Vibration doubled (P=0.039) cancellous bone stiffness in the 0.6 g and 1.2 g groups and induced a 74% increase in PGE2 concentrations (P=0.007). However, femoral densitometry and strength of the neck and shaft were unchanged and the cancellous bone indentation strength did not differ statistically (P=0.084). Cartilage thickness of vibrated groups at the medial condyle did not increase significantly (P=0.142) and the histopathologic grade did not change. There was no definitive optimal vibration amplitude., Conclusion: The benefits of vibration therapy over five weeks were confined to cancellous bone.

Two major problems are associated with total hip replacement: 1) stress shielding and 2) the adverse tissue reaction to certain elements of the implant material. In this regard, a porous implant provides lower stiffness and vacancies for bone ingrowth, making it more suitable for the human bone compared with a solid stem. Moreover, second-generation titanium biomedical alloys, such as TNZT (Ti35Nb7Zr5Ta) and TMZF (Ti12Mo6Zr2Fe), have been introduced to prevent the adverse tissue reactions related to aluminum and vanadium elements of the popular Ti6Al4V alloy. In the current work, an analysis was performed based on uniaxial compression testing of cubic Ti6Al4V structures of different porosities to predict the governing equations that relate the relative density of the structure to the mechanical properties of the structure according to the Gibson-Ashby model. A numerical study was conducted to evaluate the change in stress distribution obtained by incorporating the new titanium alloys in porous hip stem implants. Implants modeled with the mechanical properties of TNZT and TMZF showed a minimum safety factor of 1.69 and 3.02, respectively, with respect to the yield strength. The results demonstrated an increase in the equivalent von Mises stresses and maximum principal elastic strain up to 7% and 15%, respectively, compared with the porous Ti6Al4V implant and up to 108% and 156%, respectively, compared with the solid Ti6Al4V implant.

In total hip arthroplasty (THA), the femoral stem can be fixed with or without bone cement. Cementless stem fixation is recommended for young and active patients as it eliminates the risk of loss of fixation at the bone-cement and cement-implant interfaces. Cementless fixation, however, suffers from a relatively high early revision rate. In the current research, a novel low-stiffness hip stem was designed, fabricated and tested. The stem design provided the option to inject biodegradable bone cement that could enhance initial stem stability. The stem was made of Ti6Al4V alloy. The proximal portion of the stem was porous, with cubic cells. The stem was fabricated using electron beam melting (EBM) technology and tested in compression and bending. Finite-element analysis was used to evaluate stem performance under a dynamic load representing a stair descending cycle and compare it to the performance of a solid stem with similar geometry. The von Mises stresses and maximum principal strains generated within the bone increased after porous stem insertion compared to solid stem insertion. The low-modulus stem tested in this study has acceptable mechanical properties and generates strain patterns in bone that appear compatible with clinical use.

The Regenerative Medicine Foundation Annual Conference held on May 6 and 7, 2014, had a vision of assisting with translating tissue engineering and regenerative medicine (TERM)-based technologies closer to the clinic. This vision was achieved by assembling leaders in the field to cover critical areas. Some of these critical areas included regulatory pathways for regenerative medicine therapies, strategic partnerships, coordination of resources, developing standards for the field, government support, priorities for industry, biobanking, and new technologies. The final day of this conference featured focused sessions on manufacturing, during which expert speakers were invited from industry, government, and academia. The speakers identified and accessed roadblocks plaguing the field where improvements in advanced manufacturing offered many solutions. The manufacturing sessions included (a) product development toward commercialization in regenerative medicine, (b) process challenges to scale up manufacturing in regenerative medicine, and (c) infrastructure needs for manufacturing in regenerative medicine. Subsequent to this, industry was invited to participate in a survey to further elucidate the challenges to translation and scale-up. This perspective article will cover the lessons learned from these manufacturing sessions and early results from the survey. We also outline a road map for developing the manufacturing infrastructure, resources, standards, capabilities, education, training, and workforce development to realize the promise of TERM., (©AlphaMed Press.)