Prosthesis

Background: Prosthetic joint infections (PJI) are complex complications of arthroplasty. Detailed sequential polymicrobial infection during long clinical courses, with multiple interventions and sustained antibiotic pressure, has been described sparingly. Methods: We present a case of a 78-year-old woman with various comorbidities, including type 2 diabetes mellitus and grade I obesity (body mass index of 31.6), who developed an early PJI after total knee arthroplasty, followed by amputation. Results: Despite serial surgical procedures and antimicrobial therapies, the patient had progressive structural failure in a complex polymicrobial PJI. Therefore, above-knee amputation was required due to reconstructive failure. During the 23-month clinical course, infections caused by six distinct bacteria, some of which were resistant and associated with intramedullary osteomyelitis, were reported at different stages. Conclusions: This case illustrates the evolution and challenging complications of a rare yet dynamic process that developed under selective surgical and antimicrobial pressure. Early recognition of host, tissue, and microbial factors is crucial to achieving optimal PJI outcomes. Full article

Background/Objectives: The management of occlusion in implant-supported fixed partial restorations (ISFPRs) remains a controversial topic due to the limited availability of high-level clinical evidence and the biomechanical differences between natural teeth and dental implants. The absence of the periodontal ligament and the altered biomechanics of implants have led to the development of specific occlusal concepts. This narrative review provides an up-to-date overview of the biological basis and biomechanical principles underlying occlusal management in ISFPRs, with a particular focus on translating these into clinically applicable recommendations. Methods: A narrative review was conducted using an electronic search of PubMed/MEDLINE, covering the period from 1 March 2001, to 1 March 2026. Clinical studies and review articles were included, along with in vitro studies and finite element analyses when relevant to the biomechanical principles of implant occlusion. Additional publications were selectively included to provide biological, biomechanical, historical, and prosthetic context. Results: The available literature indicates that the evidence supporting specific occlusal protocols for ISFPRs remains limited and heterogeneous. Contemporary occlusal concepts emphasize the minimization of non-axial loads, the optimization of occlusal morphology, the control of cantilever extension, and the consideration of patient-specific factors, such as bruxism. Monolithic zirconia represents a viable restorative option due to its favorable mechanical properties and reduced technical complications. Long-term maintenance and periodic reevaluation of the occlusion remain essential, as occlusal relationships continue to change throughout a patient’s lifetime. Conclusions: Although numerous occlusal concepts have been proposed, high-level scientific evidence remains limited. Clinicians should adopt individualized occlusal strategies based on sound biological and biomechanical principles and tailored to each patient’s specific functional needs and risk factors. The dynamic nature of occlusion in ISFPRs necessitates periodic reevaluation as an integral part of long-term maintenance. Further well-designed clinical studies are needed to establish evidence-based occlusal protocols specific to ISFPRs. Full article

Background/Objectives: Severe acetabular bone loss, particularly Paprosky type IIIA and IIIB defects and pelvic discontinuity, represents a major challenge in revision total hip arthroplasty (rTHA). Custom-made acetabular implants offer a patient-specific reconstructive option when conventional techniques may not provide adequate fixation. This systematic review evaluated the clinical outcomes, implant survivorship, complication profile, and methodological quality of custom-made acetabular implants used in complex rTHA. Methods: A systematic literature search of PubMed, ScienceDirect, and Web of Science was performed to identify eligible studies published between January 2000 and December 2025 reporting outcomes of custom-made acetabular implants in rTHA. Thirty-six eligible clinical publications were included in the qualitative synthesis. Potentially overlapping or longitudinally related patient cohorts were identified and not treated as independent populations when interpreting outcomes. Data extraction included study design, patient and defect characteristics, implant type, follow-up duration, implant survivorship, functional outcomes, complications, and re-revision. Methodological quality was assessed using the Methodological Index for Non-Randomized Studies (MINORS). Results: Reported implant survivorship ranged from 72.4% to 100% across the included studies, with several series reporting survivorship above 90% at mid- to long-term follow-up. Functional outcomes generally improved following reconstruction, while aseptic loosening was relatively uncommon. Infection and instability were important causes of reoperation and implant failure. Methodological quality was variable: among the 34 non-comparative publications, MINORS scores ranged from 6 to 13 out of 16, while the two comparative publications scored 15/24 and 14/24. Considerable heterogeneity in patient populations, defect severity, implant design, follow-up duration, and outcome reporting precluded quantitative pooling. Conclusions: Custom-made acetabular implants represent a potential reconstructive option for carefully selected patients undergoing complex rTHA for severe acetabular bone loss and pelvic discontinuity. Published studies report favorable implant survivorship and improvements in functional outcomes; however, the evidence is derived predominantly from retrospective, non-comparative series and does not establish superiority over alternative reconstructive strategies. Prospective, multicenter, comparative investigations using standardized outcome definitions and longer follow-up are needed to better define long-term effectiveness. Full article

Background: Transmetatarsal amputation (TMA) alters foot biomechanics and is associated with abnormal plantar loading that may contribute to plantar tissue breakdown. Although plantar pressure abnormalities following TMA have been reported, the potential role of contralateral limb status in regional plantar loading patterns remains incompletely understood. This exploratory case-comparison study examined plantar loading under two different contralateral limb conditions. Methods: This exploratory case-comparison evaluated in-shoe plantar pressure in two individuals with unilateral TMA: one with an intact contralateral limb and one with a contralateral transtibial prosthesis. Plantar pressure data were collected using a Pedar-X system during overground walking at a self-selected speed. Regionally resolved outcome measures, including peak plantar pressure (PPP), pressure–time integral (PTI), and maximum force (MF), were calculated for the TMA limb. Interlimb asymmetry was assessed in the unilateral TMA participant using normalized asymmetry indices (AIs). Results: The participant with a contralateral transtibial prosthesis exhibited substantially higher PPP and MF across all TMA regions (increases of approximately 40–99%) compared with the participant with an intact contralateral limb. In contrast, PTI values were lower under the prosthetic condition. Within-subject analysis revealed pronounced interlimb asymmetry, with increased midfoot loading in the TMA limb (PPP AI: +38–44%; MF AI: >100%) and greater rearfoot loading in the intact limb (PPP AI: −25% to −35%). Conclusions: In this exploratory case-comparison, the participant with a contralateral transtibial prosthesis exhibited higher regional peak plantar pressures and maximum forces, together with lower pressure–time integrals, than the participant with an intact contralateral limb. Regional asymmetry was also observed in the unilateral TMA participant. These descriptive findings suggest that contralateral limb condition may be associated with differences in plantar loading patterns; however, the observations should be interpreted cautiously because of the exploratory nature of this two-participant case-comparison. Future studies involving larger cohorts are needed to determine whether these observations are generalizable. Full article

Background/ Objectives: Selecting an intraoral scanner (IOS) has evolved into a complex clinical decision that extends beyond technical performance alone. This study aimed to investigate the clinical, technical, educational, and organizational factors influencing intraoral scanner selection among dentists, evaluate awareness of ISO specifications and evidence-based criteria, and propose a conceptual framework to support evidence-based technology selection. Methods: A cross-sectional questionnaire-based study was conducted among dentists practicing in Greece. A total of 86 questionnaires were returned from 271 invited participants (response rate: 31.73%). Valid sample sizes varied across analyses according to item applicability and analyzable responses. The questionnaire assessed demographic and professional characteristics, intraoral scanner use, selection criteria, awareness of ISO specifications, educational background, and evidence-related factors. Composite indices were developed to evaluate the principal decision-making dimensions. Results: Technical and clinical performance-related criteria received the highest importance ratings in intraoral scanner selection. Although participants generally reported good perceived knowledge of intraoral scanners, only 35.7% reported awareness of ISO specifications. Dentists familiar with ISO standards assigned significantly greater importance to specification-related and safety-related criteria, suggesting an association between reported ISO awareness and greater emphasis on specification- and safety-related selection criteria. Continuing professional education represented the predominant source of knowledge acquisition. Based on the integration of these findings, the EBIOS Pilot Framework (Evidence-Based Intraoral Scanner Selection Framework) is proposed as a preliminary conceptual synthesis of factors potentially relevant to evidence-informed intraoral scanner selection. Conclusions: The findings suggest that intraoral scanner selection may be understood as a multidimensional decision-making process involving technical performance, scientific evidence, professional education, and standardized quality criteria. The proposed EBIOS Pilot Framework provides a preliminary conceptual basis for future validation and refinement in larger, independent populations. Full article

Background/Objectives: Raghib syndrome is a rare congenital heart disease where the left superior vena cava (LSVC) drains into the left atrium in addition to an absent coronary sinus and an atrial septal defect. This condition can lead to hemodynamic impairment and ultimately put the patient at a high risk of stroke. While computational flow modeling enables predictive understanding of the heart hemodynamic, augmented reality (AR) provides a deeper understanding of complex anatomic geometries. This study shows the case of a 53-year-old woman with Raghib syndrome in whom preoperative planning was supported by the integration of computational fluid dynamics (CFD) and AR. Methods: Three-dimensional (3D) anatomical models were segmented from CT imaging and used to perform CFD simulations of pre- and post-operative hemodynamics, quantifying the left-to-right shunt and confirming restoration of normal intracardiac flow after surgical repair. Results: The AR application developed allowed surgeons to visualize and manipulate holographic cardiac models, enabling accurate assessment of LSVC length, vessels distances and septal defect geometry using HoloLens 2 headsets. Conclusions: This work demonstrates the feasibility and adds value of the immersive approach coupled with quantitative in silico flow analysis for preoperative planning of complex congenital heart disease. Full article

Background: Lower limb exoprostheses often lead to stump dermatological pathologies. The mechanisms by which mechanical microtraumas progress to non-healing ulcerative defects due to dysbiosis remain poorly understood. The objective of this study was to analyze mechanical, inflammatory, and infectious stump skin complications and justify the role of bacterial and mycological dysbiosis in blocking tissue regeneration. Methods: A critical narrative review guided by SANRA principles was conducted (PubMed/Scopus, 1980–2026). Data were extracted with a structured query focusing on amputation stumps, prosthetic interfaces, and skin/microbiological complications (dysbiosis, biofilms, and inflammatory markers). Evidence was graded using predefined clinical matrices and integrated through structured evidence collations to synthesize stump–prosthesis pathogenesis. The PRISMA method was not applied due to study heterogeneity. Results: Skin damage dynamics were categorized into three stages: adaptation (up to 12 months), chronic reactive changes (12–24 months), and late proliferative-infectious destruction (>24 months). The sealed liner space creates 100% humidity and alkalization (pH > 6.5). This causes a mycological shift, where resident Malassezia spp. lose dominance to invasive Candida albicans and non-dermatophyte molds (Aspergillus spp., Fusarium spp.). These pathogens form polymicrobial biofilms with Staphylococcus aureus. At the molecular level, delayed regeneration is driven by “frustrated phagocytosis”: macrophages, unable to engulf large fungal hyphae, continuously release reactive oxygen species and enzymes, trapping the wound in the inflammatory phase. Excessive matrix degradation and suppressed angiogenic factors further block epithelialization. Conclusions: The skin under a prosthesis socket forms a unique pathological biotope. Successful regeneration requires preventive mycobiota correction and targeted management of biophysical parameters (pH, humidity) within the “skin–liner” interface. Full article

Background/Objectives: Studies consistently demonstrate that microprocessor-controlled prosthetic knees (MPKs) improve mobility and quality of life for people with lower limb loss or absence by enhancing balance and reducing falls. However, the extent to which these benefits apply across demographic groups remains unclear. Therefore, we conducted a literature review to evaluate how representative and transferable research on MPKs is across different populations, and which factors influence this. Methods: Using systematic review principles and PRISMA guidelines, 27 studies were analysed from databases including Cochrane, CINAHL, MEDLINE, and PubMed, as of 20th September 2025. The included studies primarily focused on young-to-middle-aged adults, men, individuals with trauma-related amputation, and higher mobility levels. Results: We found that older adults, women, and individuals with amputation caused by vascular disease or diabetes were under-represented in MPK research. Moreover, variability in time since amputation complicates the generalisability of findings, as this factor significantly influences adaptation and functional outcomes. Conclusions: While evidence supports MPKs’ effectiveness in enhancing mobility and reducing the risk of falls, their benefits may not fully apply to under-represented groups, such as older adults, women, or low-activity users. Future research should prioritise more diverse participant samples to improve the generalisation of MPK outcomes across different demographics and functional levels. Full article

Background: Accurate reproduction of subgingival finish lines remains a major challenge in fixed prosthodontics. This scoping review aimed to map and synthesize current evidence comparing digital and conventional impression techniques for tooth-supported restorations with subgingival margins. Methods: The review followed the Arksey and O’Malley framework and was reported in accordance with PRISMA-ScR guidelines. Four electronic databases (PubMed, Scopus, Web of Science, and Google Scholar) were searched for English-language studies published between 2005 and 2025. Eligible studies included both in vitro and in vivo investigations evaluating impression techniques in subgingival conditions. Results: A total of 51 studies were included, of which 66.6% were in vitro. Digital scanning accuracy decreased consistently as subgingival depth increased, particularly beyond approximately 1 mm below the gingival margin. Conventional elastomeric impressions generally demonstrated more consistent reproduction of deeper subgingival margins. Conclusions: Impression accuracy in subgingival conditions appears to depend primarily on finish line depth and clinical conditions rather than on impression modality alone. Digital workflows appear reliable for equigingival and shallow subgingival margins, whereas conventional or hybrid approaches may remain advantageous in deeper subgingival scenarios. Further well-designed in vivo studies using standardized measurement protocols are needed to support evidence-based clinical recommendations. Full article

Background/Objectives: Injection moulding has become a predictable technique for transferring a diagnostic wax-up to direct composite restorations. However, conventional workflows that rely exclusively on injectable flowable composites may have limitations in material handling, mechanical performance, and the dimensional stability of the transparent silicone index. The purpose of this technical note was to describe a silicone-guided modification of the injection moulding workflow, referred to as the compression moulding technique, and to illustrate its clinical application in three representative cases. Methods: The proposed workflow combines a dual-layer silicone index consisting of a transparent polyvinyl siloxane material supported by a high-hardness bite-registration silicone with a preheated medium-viscosity resin composite. Following digital planning and diagnostic wax-up, the composite is positioned within the silicone index and adapted to the prepared tooth surfaces by controlled compression. Three clinical cases with different restorative indications were included to demonstrate the technique’s versatility. Results: In all three cases, the proposed workflow enabled accurate transfer of the diagnostic wax-up while providing improved stabilization of the transparent silicone index during composite placement. The combination of controlled compression, a rigid supporting silicone, and preheated paste composite facilitated material adaptation, minimized manual sculpting, and produced predictable esthetic outcomes in a minimally invasive chairside procedure. Conclusions: The compression moulding technique represents a practical modification of the conventional injection moulding workflow for direct composite restorations. The proposed protocol may improve index stability, material handling, and clinical versatility while maintaining the advantages of silicone-guided restorative procedures. Because the present article is intended to describe a technical workflow supported by representative clinical cases, further prospective clinical studies with long-term follow-up are required before conclusions regarding clinical superiority or long-term performance can be drawn. Full article

Background/Objectives: To compare the effects of different surface treatments on the color and translucency of three types of zirconia ceramics. Methods: Ninety CAD/CAM-milled zirconia disks (10 mm diameter, 1 mm thickness) were fabricated from Cercon HT (3-YTZP), IPS e.max ZirCAD MT (4-YTZP), and Cercon XT (5-YTZP). Baseline CIE Lab* coordinates were measured using a digital spectrophotometer. The disks underwent one of three surface treatments: 50 µm alumina air-particle abrasion (AAA), Zircos-E etching (ZE), or 100 µm glass bead air-particle abrasion (GBA). Post-treatment CIE Lab* measurements were obtained, and color change (ΔE₀₀, CIEDE2000) and translucency change (ΔTP₀₀) were calculated. Results: Regarding color change (ΔE₀₀), 50 µm AAA produced the greatest change, followed by ZE, while GBA caused the smallest change. Surface treatment and its interaction with material type were found to exert a significant effect, whereas material type alone was not significant. Cercon XT showed the highest numerical ΔE₀₀ value among the materials, although the difference was not statistically significant. All ΔE₀₀ values were below the clinical acceptability threshold (<1.8). No significant effects of surface treatment, material type, or their interaction were observed for translucency change (ΔTP₀₀) after surface treatment. Baseline translucency values (TP₀₀) differed significantly, with Cercon XT being the most translucent, followed by ZirCAD MT and Cercon HT, but these differences did not result in significant ΔTP₀₀ changes post treatment. Conclusions: Surface treatments and their interaction with material type significantly affected zirconia color change, with 50 µm alumina air-particle abrasion producing the most pronounced effect. Material type alone did not significantly influence ΔE₀₀, though Cercon XT showed the highest numerical value. Translucency change (ΔTP₀₀) after treatment was unaffected by surface treatment or material–treatment interaction. Full article

Background: The management of complete mandibular edentulism in frail patients with severe bone atrophy is a clinical challenge. Ultrashort implants (≤4 mm) have been proposed as a minimally invasive alternative to bone augmentation procedures; however, long-term evidence in full-arch rehabilitations remains limited. Methods: This retrospective single-center cohort study presents the 10-year follow-up of patients treated with full-arch mandibular rehabilitation under immediate loading supported by 4 mm ultrashort implants. Patients were originally treated between 2015 and 2017. The primary outcome was prosthetic success at 10 years, defined as a stable and functional prosthesis supported by four implants. Secondary outcomes included implant survival, timing of implant loss, and biological and prosthetic complications. Results: Fourteen patients were available for evaluation at the 10-year follow-up. The success of the prosthetic structure was 100%, with all patients maintaining stable and functional rehabilitation. As regards the implants, a total of 82 implants had been placed, with 14 implant losses, resulting in a cumulative implant survival rate of 82.9%. Implant losses occurred mainly in early (1 week, 4 months) and late phases (between 3 and 10 years), while no losses were observed between 1 and 3 years. Overall, 71.43% of patients experienced at least one implant loss; however, this did not compromise prosthetic function. Conclusions: In this retrospective cohort, all full-arch prostheses remained functional at 10 years, although cumulative implant survival was 82.9%. These findings suggest that rehabilitation supported by 4 mm ultrashort implants may represent a treatment option for carefully selected frail patients with severe mandibular atrophy. Prospective controlled studies are needed to confirm these findings and compare this approach with standard-length implants and bone augmentation procedures. Full article

Background/Objectives: Lower-limb amputation significantly impacts autonomy and daily functioning. Microprocessor-controlled prosthetic knees (MPKs) improve mobility, safety, and quality of life compared with non-microprocessor prosthetic knees (nMPKs). Despite general benefits, differences among MPK models remain unclear. The goal of this investigation was to evaluate functional mobility and patient-reported outcomes in active transfemoral amputees using a new MPK (PROTEOR QUATTRO) compared with existing MPKs. Methods: In this multicenter cross-over clinical trial, active transfemoral amputees were assessed using patient-specific functional scales (PSFS), standardized locomotor capacity tests (6MWT, 10mWT, HAI, SAI) and satisfaction and quality-of-life questionnaires (PEQ-A, SF-36, ESAT). Biomechanical data collection was performed during walking test, to examine gait symmetry indices. Results: The QUATTRO MPK was associated with significantly higher PSFS scores, reflecting higher self-rated ability in performing chosen daily life activities compared with patient’s current prosthesis. Standardized locomotor tests revealed comparable performance between devices. Biomechanical analyses showed similar symmetry indices for QUATTRO and other MPKs. Patient-reported outcomes showed an improvement in physical health with QUATTRO, while overall satisfaction remained similar. Conclusions: QUATTRO improved patient-perceived ability to perform meaningful daily-life activities while maintaining comparable performance on standardized locomotor tests. These results highlight the importance of patient-centered assessments in identifying functional benefits that may guide individualized prosthetic prescriptions for active transfemoral amputees. Full article

Introduction/Objectives: The mechanical reliability of prosthetic finger connectors is critical for daily prosthesis use, as these small load-bearing elements transmit forces between finger segments and are prone to localized stress concentration at hinge transitions. The objective of this study was to quantitatively evaluate the mechanical performance of prosthetic finger connectors and determine how material selection influences stress distribution and deformation behavior when connector geometry is maintained constant. Methods: A controlled comparative finite element analysis was performed using COMSOL Multiphysics 6.2 on a single prosthetic finger connector geometry manufactured from four candidate materials: titanium alloy Ti-6Al-4V (E = 110 GPa), polyetheretherketone (PEEK, E = 4.0 GPa), AvaSpire AV-621 NT (E = 3.0 GPa), and KetaSpire KT-820 FP (E = 4.1 GPa). Three representative loading scenarios were simulated using an axial grip force of 50 N and a bending moment of 0.5 N·m: (1) axial loading, (2) combined axial and forward bending, and (3) combined axial and reverse bending. Results: Across all loading conditions, peak von Mises stresses consistently localized at the hinge-transition region of the connector. Ti-6Al-4V demonstrated the lowest peak stress (approximately 2.2 MPa under combined forward bending) and the smallest maximum displacement (approximately 0.0005 mm). In contrast, the PEEK-family polymers showed greater deformation (0.0125–0.0167 mm) due to their lower elastic modulus, while maintaining comparable peak stresses of approximately 2.5–2.6 MPa. The stress profiles along the connector arc length were nearly identical among all materials, indicating that connector geometry primarily governs stress localization, whereas material stiffness mainly determines deformation magnitude. Conclusions: This study demonstrates that material selection strongly affects prosthetic finger connector compliance, while stress concentration behavior is mainly controlled by geometry. The obtained quantitative comparison provides design-oriented guidance for selecting between Ti-6Al-4V and PEEK-based polymers for the development of lightweight and mechanically reliable prosthetic finger connectors. Full article

Objective: The aim of this study was to assess the predictability of a digital workflow for manufacturing provisional maxillary removable dentures and immediately loaded implant-supported mandibular prostheses. Materials and Methods: Eighteen completely edentulous patients were enrolled. Complete dentures, when present, were adapted; when they were absent, records with a denture base and wax rim were fabricated. The adjusted prostheses were scanned, generating STL files; photographs with the prostheses in occlusion were used to generate a virtual patient; and lateral cephalometric radiographs were obtained. Virtual tooth arrangement was performed, and, after approval, a maxillary denture and a mandibular prosthesis in multifunctional guide format were printed and evaluated intraorally. Four implants (Nuvo, Brazil) were installed using a guide (which was also used as a tray and for registration). In the laboratory, the guide was converted into an interim fixed prosthesis. After installation, the prostheses were evaluated independently by three examiners. A new lateral cephalometric radiograph was obtained in occlusion. Descriptive analysis of the data obtained from the professional evaluation was carried out, and the Shapiro–Wilk test was used to test the adherence of the data to a normal distribution for quantitative variables. Results: The professional satisfaction rate for the clinical evaluation and installation of the prostheses was >9. The different factors were always favorably appraised, with strong agreement between examiners. The cephalometric analysis of OVD showed reproducibility with respect to the initial clinical determination. Conclusions: Although the study included a small number of patients, based on the results obtained, it seems reasonable to conclude that this digital workflow exhibits predictability for rehabilitation with 3D-printed provisional maxillary dentures and immediately loaded implant-supported provisional prostheses. Full article

Background: Finite element analysis (FEA) has become a cornerstone of dental biomechanics, supporting the simulation of stress, strain, and displacement in biological structures and biomaterials. Methods: This combined bibliometric and narrative review examines the development, geographic and disciplinary distribution, and methodological state of FEA-based dental research by analysing 3379 publications indexed in Scopus between 1969 and 2024. Results: The dataset shows continued exponential growth in annual output, particularly after 2000, with China, the United States, and India as the leading contributors. Journal articles account for the bulk of the literature, and implant dentistry remains the most prominent focus area. The 100 most-cited works concentrate on implant biomechanics, prosthodontics, and scaffold design, while interdisciplinary contributions linking FEA to regenerative biomaterials, orthodontics, and endodontics are increasing. Conclusions: FEA in dentistry is a mature but still rapidly expanding field. Persistent methodological gaps remain, including the routine use of isotropic and linear-elastic bone, idealised osseointegration, static loading, limited patient-specific variability, and scarce in vivo validation. Future work should converge on patient-specific multiscale models, fatigue and contact-aware formulations, standardised validation pipelines, and the integration of artificial intelligence into both pre-processing (mesh generation, parameter identification) and post-processing (surrogate models, outcome prediction). The wider relevance of FEA across orthopaedic, thoracic, and reconstructive biomechanics confirms its role as a unifying computational tool for clinical translation. Full article

Background: Accurate acetabular component positioning is critical to the success of total hip arthroplasty (THA). Mixed reality (MR)-based simulation offers a novel approach to surgical training by providing real-time feedback within immersive learning environments. This study evaluated the impact of an MR-based simulation on technical performance, as well as its usability and user experience. Methods: A prospective pre–post pilot educational study was conducted in a controlled simulation laboratory using a physical anatomical model. Forty-six final-year medical students with no prior experience in MR technology participated. Participants performed acetabular component positioning tasks before and after MR-assisted training. Technical accuracy was assessed by measuring deviations in inclination and anteversion. Usability, workload, presence, and cybersickness were evaluated using validated questionnaires. Results: MR-assisted training significantly improved technical accuracy. Median absolute deviation in inclination decreased from 1.0° (interquartile range [IQR], 1.0–3.5) to 0.5° (IQR, 0.0–2.0) (p = 0.0008, r = 0.56), while anteversion deviation decreased from 4.5° (IQR, 2.0–7.0) to 2.0° (IQR, 1.0–4.0) (p < 0.0001, r = 0.66). User experience scores ranked the application among top-performing systems in benchmark comparisons. Participants reported high levels of presence and usability, low workload (all NASA-TLX domains <36/100), and minimal cybersickness (mean Simulator Sickness Questionnaire score = 0.26). Conclusions: MR-assisted simulation significantly improved short-term technical performance in novice trainees and was associated with high user acceptance and minimal adverse effects. These findings support the use of MR as a promising adjunct in early surgical training, enabling integration of cognitive and psychomotor skills through real-time feedback. Further studies are warranted to evaluate skill retention and transfer to clinical practice. Full article

Background: The natural motion of the human knee involves a combination of rotation and translation, resulting in a variable Instantaneous Center of Rotation (ICR) throughout the gait cycle. Traditional prosthetic knee designs often fail to reproduce this complex kinematic behavior. Objectives: This study aims to propose a customized, biomimetic knee mechanism through the synthesis of a four-bar linkage capable of approximating the physiological ICR trajectory with high precision. Methods: A Genetic Algorithm (GA) was implemented to optimize the geometric parameters of the four-bar mechanism, specifically its link lengths and inter-link angles. The optimization process is based on Freudenstein’s equation, which analytically relates the input and output angles of the linkage to the lengths of its links. The desired ICR trajectory was derived from experimental data, and the objective function minimized the Euclidean error between the generated and target trajectories. Results: The proposed method yielded customized mechanisms that closely approximate the target ICR curves, achieving an overall mean Euclidean tracking error of 1.95% (±1.68%) across diverse patient profiles, with a best-case optimization error as low as 0.355%. Furthermore, the GA demonstrated high computational efficiency, converging on optimal geometric configurations in an average execution time of just 3.98 min. Conclusions: These numerical results validate the robustness of the GA in navigating the design space while strictly adhering to kinematic constraints, Grashof’s condition, and anatomical motion limits. The integration of Freudenstein’s equation with GA-based optimization techniques enables the customized synthesis of four-bar linkages with a high capacity to reproduce the physiological kinematics of the knee. This computational approach could be highly beneficial for the design of polycentric knee prostheses, as it reduces design and manufacturing time by providing the initial parameters for the development of the four-bar mechanism, ultimately ensuring a better biomechanical fit between prosthetic and natural human movement. Full article

Background/Objectives: Asymmetric acetabular liners used in Total Hip Arthroplasty (THA) are clinically successful in reducing revision associated with dislocation. The performance of an asymmetric liner is dependent on its positioning, although few studies have directly investigated the effects of variables such as cup orientation or extended rim position on outcomes such as impingement. Therefore, the aim of this study was to compare the incidence of impingement in THA with a standard and lipped liner. Methods: A THA was virtually implanted into a previously developed geometric model. Acetabular cups were placed in a range of clinically relevant orientations, and the model was moved through seven joint motions associated with dislocation-prone Activities of Daily Living (ADLs). The occurrence of implant–implant, implant–bone, and bone–bone impingement was assessed for the standard and lipped constructs across a total of 6,237 unique combinations of cup orientation and lipped liner apex rotations. Results/Conclusions: The model predicted that with both standard and lipped constructs, there were no component placement positions which avoided impingement for all ADLs. The number of impingement incidents was minimised when components were positioned at the higher end of the manufacturer’s recommendations for cup inclination and anteversion. The use of a lipped liner increased the frequency of impingement events compared with the standard construct. However, for anterior impingement leading to posterior dislocation, this increase may be minimised by rotating the lip apex to a posterior-inferior position. Anterior lip apex placement tended to minimise the increase in the less critical posterior impingement. Full article