Prosthesis loosening is the leading cause of postoperative revision in unicompartmental knee arthroplasty (UKA). The deviation of medial and lateral translational installation of the prosthesis during surgery is a common clinical phenomenon and an important factor in increasing the risk of prosthesis loosening. This study established a UKA finite element model and a bone-prosthesis fixation interface micromotion prediction model. The predicted medial contact force and joint motion of the knee joint from a patient-specific lower extremity musculoskeletal multibody dynamics model of UKA were used as boundary conditions. The effects of 9 femoral component medial and lateral translational installation deviations on the Von Mises stress of the proximal tibia, the contact stress, and the micro-motion of the bone prosthesis fixation interface were quantitatively studied. It was found that compared with the neutral position (a/A of 0.492), the lateral translational deviation of the femoral component significantly increased the tibial Von Mises stress and the bone-prosthesis fixation interface contact stress. The maximum Von Mises stress and the maximum contact stress of the fixation interface increased by 14.08% and 143.15%, respectively, when a/A was 0.361. The medial translational deviation of the femoral component significantly increased the bone-prosthesis fixation interface micro-motion. The maximum value of micromotion under the conditions of femoral neutral and medial translation deviation was in the range of 20-50 μm, which is suitable for osseointegration. Therefore, based on considerations such as the micromotion range suitable for osseointegration reported in the literature, the risk of reducing prosthesis loosening, and factors that may induce pain, it is recommended that clinicians control the mounting position of the femoral component during surgery within the safe range of 0-4 mm medial translation deviation.
Humans ; Arthroplasty, Replacement, Knee/methods* ; Finite Element Analysis ; Biomechanical Phenomena ; Knee Prosthesis ; Tibia/surgery* ; Femur/surgery* ; Stress, Mechanical ; Prosthesis Failure ; Knee Joint/surgery* ; Prosthesis Design

Although metal blocks have been widely used for reconstructing uncontained tibial bone defects, the influence of their elastic modulus on the stability of tibial prosthesis fixation remains unclear. Based on this, a finite element model incorporating constrained condylar knee (CCK) prosthesis, tibia, and metal block was established. Considering the influence of the post-restraint structure of the prosthesis, the effects of variations in the elastic modulus of the block on the von Mises stress distribution in the tibia and the block, as well as on the micromotion at the bone-prosthesis fixation interface, were investigated. Results demonstrated that collision between the insert post and femoral prosthesis during tibial internal rotation increased tibial von Mises stress, significantly influencing the prediction of block elastic modulus variation. A decrease in the elastic modulus of the metal block resulted in increased von Mises stress in the proximal tibia, significantly reduced von Mises stress in the distal tibia, decreased von Mises stress of the block, and increased micromotion at the bone-prosthesis fixation interface. When the elastic modulus of the metal block fell below that of bone cement, inadequate block support substantially increased the risk of stress shielding in the distal tibia and fixation interface loosening. Therefore, this study recommends that biomechanical investigations of CCK prostheses must consider the post-constraint effect, and the elastic modulus of metal blocks for bone reconstruction should not be lower than 3 600 MPa.
Knee Prosthesis ; Humans ; Finite Element Analysis ; Tibia/surgery* ; Elastic Modulus ; Arthroplasty, Replacement, Knee/methods* ; Stress, Mechanical ; Metals ; Prosthesis Design ; Knee Joint/surgery* ; Biomechanical Phenomena

Compared with total knee arthroplasty, unicondylar knee replacement has the advantage of preserving the knee tissue structure and motor function to the greatest extent. Pre-clinical in-vitro test is an important tool to evaluate the safety and effectiveness of unicondylar knee prostheses, and it is also a key focus of the product registration process. Through collection, comparison, and analysis of current regulations, technical standards, guidelines, and related research literature, this paper expounds on the relevant research methods for the pre-clinical in-vitrotesting of unicondylar knee prostheses. At the same time, in conjunction with current evaluation requirements and experience, the study discusses the focus of pre-clinical performance research for unicondylar knee prostheses during the registration process to clarify the performance evaluation requirements of this product category. This aims to provide a reference for the pre-clinical performance research of unicondylar knee prostheses and to standardize industry testing standards.
Knee Prosthesis ; Arthroplasty, Replacement, Knee ; Humans ; Prosthesis Design ; Materials Testing

BACKGROUND:Developmental dysplasia of hip causes groin pain in patients with prolonged activity or standing due to the presence of deformities of the acetabulum and femoral head in terms of structure,size and orientation,and if not effectively treated,patients' normal activities will be severely limited.OBJECTIVE:Finite element model of the hip joint of solid-liquid biphase fiber reinforced cartilage based on FEBio was established to explore the biomechanical properties of the cartilage for patients with developmental dysplasia of hip and the normal hip joint.METHODS:A patient with developmental dysplasia of hip and a normal volunteer were chosen to build their left hip models including left pelvis,left femur,and cartilage attached thereto. The solid-liquid biphase fiber reinforced cartilage of normal hip was verified to be effective. The cartilage equal contact stress,fluid pressure,solid effective stress,and fluid support rate differences between the developmental dysplasia of hip patients hip and the normal one in the case of one leg of static load (2130 N) were compared after establishing finite element models of developmental dysplasia of hip patients.RESULTS AND CONCLUSION:(1) Compared with the finite element results of the normal hip model,the cartilage contact position of developmental hip dysplasia patient hip showed obvious edge contact,the peak contact stress (3.86 Mpa) and peak fluid pressure (3.76 Mpa) were both higher than normal hip model. (2) After 1500 s (stable load-bearing capacity),peak contact stress and peak fluid pressure in both models decreased,but the cartilage contact position of developmental hip dysplasia patient hip moved from the edge of cartilage to the center,and fluid support rate decreased from 97.41％ to 91.08％. The fluid support rate in normal hip was decreased by 0.58％ from 95.24％ to 94.66％. (3) It is indicated that under the physiological load of standing on one leg,the cartilage of developmental dysplasia of hip patients showed obvious edge load,and the decrease of peak contact stress,fluid pressure,and fluid formation rate was greater than that of normal cartilage. Considering the solid-liquid biphasic fiber reinforcement characteristics of cartilage,it is of great clinical significance to evaluate the biomechanical properties of hip cartilage in developmental dysplasia of hip patients,to understand the pathophysiological mechanism of developmental dysplasia of hip,and make preoperative plan.

Objective To observe the dynamic changes in serum levels of IL-6,IL-8,TREM-1,uPAR,and presepsin in patients with septic shock and to analyze the diagnostic significance of these biomarkers.Methods A total of 150 sepsis patients admitted to the hospital between February 2023 and February 2025 were prospectively enrolled as study subjects.According to their clinical conditions,the participants were categorized into a sepsis group(non-shock,n=44)and a septic shock group(n=106).Additionally,30 healthy individuals with normal clinical indicators during the same period were selected as the control group.The serum levels of IL-6,IL-8,TREM-1,uPAR,and presepsin were measured and compared across the different groups.Spearman correlation analysis and logistic regression analysis were conducted to assess the association between these biomarkers and the severity of sepsis.The diagnostic performance of these biomarkers for septic shock was evaluated using receiver operating characteristic(ROC)curve analysis.Results There were statistically significant differences in serum levels of IL-6,IL-8,TREM1,uPAR,and presepsin among the different groups(P<0.05),with the highest values observed in the septic shock group,followed by the sepsis group and the control group(P<0.05).The APACHE Ⅱ and SOFA scores of patients with septic shock were significantly higher than those of patients with sepsis(P<0.05).Spearman correlation analysis revealed that serum concentrations of IL-6,IL-8,TREM1,uPAR,and presepsin were positively correlated with both APACHE Ⅱ and SOFA scores,with correlation coeffi-cients(rs)of 0.758,0.880,0.837,0.832,and 0.846 for APACHE Ⅱ score,and 0.487,0.549,0.557,0.626,and 0.664 for SOFA score,respectively(P<0.05).Logistic regression analysis indicated that serum levels of IL-6(OR=1.055),IL-8(OR=1.054),TREM1(OR=1.038),uPAR(OR=1.010),and presepsin(OR=2.103)were significantly associated with the development of septic shock(P<0.05).ROC curve analysis demonstrated that the AUC values for serum IL-6,IL-8,TREM1,uPAR,and presepsin in diagnosing septic shock were 0.608,0.724,0.887,0.848,and 0.885,with corresponding sensitivities of 0.432,0.909,0.795,0.909,and 0.591,and specificities of 0.880,0.481,0.915,0.736,and 0.977,respectively.When these biomarkers were combined,the AUC increased to 0.973,with a sensitivity of 0.943 and a specificity of 0.953.Furthermore,the AUC for prese-psin alone was significantly higher than that for IL-6 and IL-8 alone(P<0.05).Additionally,the AUC for the combined biomarkers was significantly greater than that for each biomarker individually(P<0.05).Conclusions Serum levels of IL-6,IL-8,TREM1,uPAR,and presepsin are significantly elevated in patients with septic shock,which may aid in the clinical diagnosis of the condition.The combined use of these five biomarkers en-hances the accuracy of diagnosing septic shock.

Objective To investigate the effects of patient bone mass differences on the stability of unicondylar knee arthroplasty(UKA)prostheses.Methods A UKA finite element model was established to quantify the effects of five different bone quality conditions on the proximal tibial von Mises stress,bone-prosthesis fixation interface contact stress,and bone-prosthesis fixation interface micromotion,using the medial knee force and joint motion predicted by the individualized UKA musculoskeletal multibody dynamics model as boundary conditions.Results The influences of bone strength on the proximal tibia von Mises stress and bone-prosthesis fixation interface contact stress were not obvious,and the difference in peak values of the proximal tibia von Mises stress between two groups of models with the largest difference in bone strength was not more than 5％,and the difference in peak values of the bone-prosthesis fixation interface contact stress was only 2.37 MPa.However,the influence of bone strength on the bone-prosthesis fixation interface micromotion was significant,and the weaker bones were more prone to cause the bone-prosthesis fixation interface micromotion.However,bone strength had a significant effect on the bone-prosthesis fixation interface micromotion,and weak bone was more likely to cause changes in the bone-prosthesis fixation interface micromotion.Compared to patients with the neutral bone quality,the prosthesis fixation interface micromotion increased by 84.67％at 20％gait cycles for patients with the weakest bone quality.Conclusions UKA patients with a weaker bone quality have a higher risk of prosthesis loosening.It is recommended that surgeons should carefully choose their surgical strategy in order to reduce the rate of postoperative revision in UKA.

Objective To investigate the effects of patient bone mass differences on the stability of unicondylar knee arthroplasty(UKA)prostheses.Methods A UKA finite element model was established to quantify the effects of five different bone quality conditions on the proximal tibial von Mises stress,bone-prosthesis fixation interface contact stress,and bone-prosthesis fixation interface micromotion,using the medial knee force and joint motion predicted by the individualized UKA musculoskeletal multibody dynamics model as boundary conditions.Results The influences of bone strength on the proximal tibia von Mises stress and bone-prosthesis fixation interface contact stress were not obvious,and the difference in peak values of the proximal tibia von Mises stress between two groups of models with the largest difference in bone strength was not more than 5％,and the difference in peak values of the bone-prosthesis fixation interface contact stress was only 2.37 MPa.However,the influence of bone strength on the bone-prosthesis fixation interface micromotion was significant,and the weaker bones were more prone to cause the bone-prosthesis fixation interface micromotion.However,bone strength had a significant effect on the bone-prosthesis fixation interface micromotion,and weak bone was more likely to cause changes in the bone-prosthesis fixation interface micromotion.Compared to patients with the neutral bone quality,the prosthesis fixation interface micromotion increased by 84.67％at 20％gait cycles for patients with the weakest bone quality.Conclusions UKA patients with a weaker bone quality have a higher risk of prosthesis loosening.It is recommended that surgeons should carefully choose their surgical strategy in order to reduce the rate of postoperative revision in UKA.

BACKGROUND:Developmental dysplasia of hip causes groin pain in patients with prolonged activity or standing due to the presence of deformities of the acetabulum and femoral head in terms of structure,size and orientation,and if not effectively treated,patients' normal activities will be severely limited.OBJECTIVE:Finite element model of the hip joint of solid-liquid biphase fiber reinforced cartilage based on FEBio was established to explore the biomechanical properties of the cartilage for patients with developmental dysplasia of hip and the normal hip joint.METHODS:A patient with developmental dysplasia of hip and a normal volunteer were chosen to build their left hip models including left pelvis,left femur,and cartilage attached thereto. The solid-liquid biphase fiber reinforced cartilage of normal hip was verified to be effective. The cartilage equal contact stress,fluid pressure,solid effective stress,and fluid support rate differences between the developmental dysplasia of hip patients hip and the normal one in the case of one leg of static load (2130 N) were compared after establishing finite element models of developmental dysplasia of hip patients.RESULTS AND CONCLUSION:(1) Compared with the finite element results of the normal hip model,the cartilage contact position of developmental hip dysplasia patient hip showed obvious edge contact,the peak contact stress (3.86 Mpa) and peak fluid pressure (3.76 Mpa) were both higher than normal hip model. (2) After 1500 s (stable load-bearing capacity),peak contact stress and peak fluid pressure in both models decreased,but the cartilage contact position of developmental hip dysplasia patient hip moved from the edge of cartilage to the center,and fluid support rate decreased from 97.41％ to 91.08％. The fluid support rate in normal hip was decreased by 0.58％ from 95.24％ to 94.66％. (3) It is indicated that under the physiological load of standing on one leg,the cartilage of developmental dysplasia of hip patients showed obvious edge load,and the decrease of peak contact stress,fluid pressure,and fluid formation rate was greater than that of normal cartilage. Considering the solid-liquid biphasic fiber reinforcement characteristics of cartilage,it is of great clinical significance to evaluate the biomechanical properties of hip cartilage in developmental dysplasia of hip patients,to understand the pathophysiological mechanism of developmental dysplasia of hip,and make preoperative plan.

Objective To observe the dynamic changes in serum levels of IL-6,IL-8,TREM-1,uPAR,and presepsin in patients with septic shock and to analyze the diagnostic significance of these biomarkers.Methods A total of 150 sepsis patients admitted to the hospital between February 2023 and February 2025 were prospectively enrolled as study subjects.According to their clinical conditions,the participants were categorized into a sepsis group(non-shock,n=44)and a septic shock group(n=106).Additionally,30 healthy individuals with normal clinical indicators during the same period were selected as the control group.The serum levels of IL-6,IL-8,TREM-1,uPAR,and presepsin were measured and compared across the different groups.Spearman correlation analysis and logistic regression analysis were conducted to assess the association between these biomarkers and the severity of sepsis.The diagnostic performance of these biomarkers for septic shock was evaluated using receiver operating characteristic(ROC)curve analysis.Results There were statistically significant differences in serum levels of IL-6,IL-8,TREM1,uPAR,and presepsin among the different groups(P<0.05),with the highest values observed in the septic shock group,followed by the sepsis group and the control group(P<0.05).The APACHE Ⅱ and SOFA scores of patients with septic shock were significantly higher than those of patients with sepsis(P<0.05).Spearman correlation analysis revealed that serum concentrations of IL-6,IL-8,TREM1,uPAR,and presepsin were positively correlated with both APACHE Ⅱ and SOFA scores,with correlation coeffi-cients(rs)of 0.758,0.880,0.837,0.832,and 0.846 for APACHE Ⅱ score,and 0.487,0.549,0.557,0.626,and 0.664 for SOFA score,respectively(P<0.05).Logistic regression analysis indicated that serum levels of IL-6(OR=1.055),IL-8(OR=1.054),TREM1(OR=1.038),uPAR(OR=1.010),and presepsin(OR=2.103)were significantly associated with the development of septic shock(P<0.05).ROC curve analysis demonstrated that the AUC values for serum IL-6,IL-8,TREM1,uPAR,and presepsin in diagnosing septic shock were 0.608,0.724,0.887,0.848,and 0.885,with corresponding sensitivities of 0.432,0.909,0.795,0.909,and 0.591,and specificities of 0.880,0.481,0.915,0.736,and 0.977,respectively.When these biomarkers were combined,the AUC increased to 0.973,with a sensitivity of 0.943 and a specificity of 0.953.Furthermore,the AUC for prese-psin alone was significantly higher than that for IL-6 and IL-8 alone(P<0.05).Additionally,the AUC for the combined biomarkers was significantly greater than that for each biomarker individually(P<0.05).Conclusions Serum levels of IL-6,IL-8,TREM1,uPAR,and presepsin are significantly elevated in patients with septic shock,which may aid in the clinical diagnosis of the condition.The combined use of these five biomarkers en-hances the accuracy of diagnosing septic shock.