Life expectancy is on the rise and, concurrently, the demand for total knee arthroplasty (TKA), which lasts a lifetime, is increasing. To meet this demand, improved TKA designs have been introduced. Recent advances in radiography and manufacturing techniques have enabled the production of patient-specific TKA. Nevertheless, concerns regarding the wear performance, which limit the lifespan of TKA, remain to be addressed. This study aims at reducing the wear in patient-specific TKA using design optimization and parametric three-dimensional (3D) finite-element (FE) modelling. The femoral component design was implemented in a patient-specific manner, whereas the tibial insert conformity remained to be determined by design variables. The gait cycle loading condition was applied, and the optimized model was validated by the results obtained from the experimental wear tests. The wear predictions were iterated for five million gait cycles using the computational model with force-controlled input. Similar patterns for internal/external rotation and anterior/posterior translation were observed in both initial and optimal models. The wear rates for initial and optimal models were recorded as 23.2 mm³/million cycles and 16.7 mm³/million cycles, respectively. Moreover, the experimental wear rate in the optimal design was 17.8 mm³/million cycles, which validated our optimization procedure. This study suggests that tibial insert conformity is an important factor in influencing the wear performance of patient-specific TKA, and it is capable of providing improved clinical results through enhanced design selections. This finding can boost the future development of patient-specific TKA, and it can be extended to other joint-replacement designs. However, further research is required to explore the potential clinical benefits of the improved wear performance demonstrated in this study.

The stability of the tibial component in Total Knee Arthroplasty (TKA) is critical to preventing aseptic loosening, a major cause of implant failure. However, existing tibial stem designs often lead to stress shielding and bone resorption, highlighting the need for further optimization. This study addresses these challenges by employing the Design of Experiments (DOE) methodology, specifically utilizing a full factorial design approach combined with finite element analysis (FEA), to optimize the geometry of the tibial stem. The material properties of the cortical and cancellous bone, as well as the tibial tray, were assigned based on values from the literature, representing their elastic moduli and Poisson’s ratios. For boundary conditions, the distal end of the tibia was fully constrained to simulate realistic load transfer, while compressive loads representative of walking and daily activities were applied to the tibial base. Key design parameters, including stem diameter, length, mediolateral ratio (M/L ratio), and wing angle, were systematically analyzed. The results identified stem diameter and length as the most influential factors in improving biomechanical performance, while the wing angle showed minimal impact. The optimized design, featuring a stem diameter of 12 mm, length of 40 mm, M/L ratio of 0.61, and a wing angle of 60°, demonstrated significant reductions in stress shielding and aseptic loosening compared to conventional models. These findings provide valuable insights into enhancing the long-term success of TKA implants by balancing implant stability and minimizing bone resection.

The current study aims to analyze the biomechanical effects of ultra-high molecular weight polyethylene (UHMWPE) and carbon-fiber-reinforced polyetheretherketone (CFR-PEEK) inserts, in varus/valgus alignment, for a tibial component, from 9° varus to 9° valgus, in unicompartmental knee replacement (UKR). The effects on bone stress, collateral ligament force, and contact stress on other compartments were evaluated under gait cycle conditions, by using a validated finite element model. In the UHMWPE model, the von Mises’ stress on the cortical bone region significantly increased as the tibial tray was in valgus >6°, which might increase the risk of residual pain, and when in valgus >3° for CFR-PEEK. The contact stress on other UHMWPE compartments decreased in valgus and increased in varus, as compared to the neutral position. In CFR-PEEK, it increased in valgus and decreased in varus. The forces on medial collateral ligaments increased in valgus, when compared to the neutral position in UHMWPE and CFR-PEEK. The results indicate that UKR with UHMWPE showed positive biomechanical outputs under neutral and 3° varus conditions. UKR with CFR-PEEK showed positive biomechanical outputs for up to 6° varus alignments. The valgus alignment should be avoided.

The various factors related to the morphometric characteristics of patella make it difficult to produce a standard interpretation of their respective values. A total of 1423 patients participated in this work. The distribution of Insall–Salvati ratios was investigated, and the upper and lower limits of two standard deviations were used to define the patellar alta and baja. An additional method was used, where 2.5% at each end of the distribution was defined as patellar alta and baja. Ratios in the females and males were 0.92 ± 0.14 and 0.87 ± 0.14, respectively. The ratios were considerably higher in females than in males (p < 0.05). Ratios defined for patellar alta and baja were 1.19 and 0.68 for females and 1.13 and 0.58 for males, respectively, when two standard deviations were used. Ratios defined for patellar alta and baja were 1.22 and 0.66 for females and 1.15 and 0.59 for males, respectively, when the extreme 2.5% method was used. No considerable differences in the patellar alta and baja were observed between the two methods. Patellar alta and baja were determined in ratios of more than 1.20 and less than 0.64, respectively. No significant differences in the patellar alta and baja were observed between the genders in the Korean population. Additionally, two standard deviations of the Insall–Salvati index are recommended for defining patellar alta and baja for the Korean population. However, we recommended analyzing the histogram distribution for the population, followed by an analysis of the patellar alta and baja.

To compare the angle between the external rotation references of the femoral components in the axial plane by gender and lower limb alignment in Korean patients with osteoarthritis (OA). Magnetic resonance (MR) images of 1273 patients were imported into a modeling software and segmented to develop three-dimensional femoral bony and cartilaginous models. The surgical transepicondylar axis (sTEA), posterior condylar axis (PCA), the kinematically aligned axis (KAA), and anteroposterior axis were used as rotational references in the axial plane for mechanically aligned (MA) TKA. The relationship among axes were investigated. Among 1273 patients, 942 were female and 331 were male. According to lower limb alignment, the varus and valgus knee groups comprised 848 and 425 patients, respectively. All measurements, except PCA-sTEA, differed significantly between men and women; all measurements, except PCA-sTEA, did not differ significantly between the varus and valgus knee groups. In elderly Korean patients with OA, rotational alignment of the distal femur showed gender differences, but no differences were seen according to lower limb alignment. The concern for malrotation of femoral components during kinematically aligned TKA is less in Koreans than in Caucasians and relatively less in women than in men. In MA TKA, malrotation of the femoral components can be avoided by setting different rotational alignments for the genders.

Introduction: Kartogenin, a potent inducer of chondrogenic differentiation in mesenchymal stem cells and a key agent in cartilage regeneration, presents a viable therapeutic strategy for osteoarthritis management. Despite the abundance of literature on therapeutic potential of kartogenin, there is a paucity of studies characterizing the formulation specifics in microsphere fabrication. This exploration is pivotal to advances in regenerative medicine, particularly in the domain of cartilage regeneration, to assure clinical efficacy and safety.Methods: In this work, we fabricated kartogenin-loaded PLGA microspheres with diverse formulations and their particle size, size distribution, encapsulation efficiency, drug loading and release profiles were characterized. Ratio of polymer, drug, and solvent and the use of surfactant was used as variables, and in particular, the effect of surfactant on particles was investigated.Results: The average diameter of the spheres was 16.0–31.7 μm. Morphological variations from solid to porous surface structures depending on surfactant incorporation during the emulsification process was observed. Cumulative kartogenin release from microspheres ranged from 53.8% to 80.9% on day 28, and release profiles conform predominantly to the Korsmeyer-Peppas kinetics model.Discussion: This study provides a foundational framework for modulating kartogenin release dynamics, a critical consideration for optimizing therapeutic efficacy and minimizing adverse effects in cartilage tissue engineering applications.