BACKGROUND:Avascular necrosis of the femoral head is a refractory orthopedic disease that seriously affects the normal life of patients.Hip preservation is recommended for young patients due to the limited prosthesis longevity and revision.Accurate prediction of the mechanical properties of the necrotic area in the early stage and then intervention is the key to hip preservation. OBJECTIVE:To establish a dynamic contact mechanics finite element model of necrotic femoral head based on human hip CT data and predict effects of both necrotic volume magnitude and its position on biomechanics of the necrotic region under walking movement. METHODS:CT data of a volunteer were collected and then geometry model of the hip was rebuilt.Finite element model of the necrotic femoral head was established using the Abaqus software.Nine different necrotic femoral models were constructed by combined both three different necrotic volume magnitudes(small,medium and big volume)and three different necrotic positions(coincided with,medium deviated with and kept away from the line of the force).The Von Mises of the necrotic region for all models were predicted under both 3 000 N static load and dynamical loads of one whole ISO walking gait cycle.The collapse risk for all models was evaluated based on collapse criterion. RESULTS AND CONCLUSION:(1)More approaching of the necrotic region to the line of force and bigger collapse volume made the maximum Von Mises increasing.This also enlarged the collapse risk of the necrotic region.(2)For different load types,walking movement increased the maximum Von Mises of the necrotic region than that of the value under static load under the same necrotic volume and location.(3)In conclusion,dynamic load would result in increasing of the maximum Von Mises of the necrotic region comparing to static load during exercise.Therefore,the risk of local collapse will increase due to greater Von Mises.However,the overall collapse risk is lower than that of static load due to the dynamic change of bearing area.This factor should be carefully considered by surgeons when they evaluate the mechanical performance of the necrotic femoral head.

Objective For patient-specific open-wedge high tibial osteotomy(OWHTO),a novel anatomical fixation plate was designed,and the effects of geometric parameters and material selection on biomechanical fixation were studied.Methods A patient-specific OWHTO anatomical fixation plate was designed and constructed,and the effects of design parameters(thickness,width,and length of the fixation plate)and four different materials(stainless steel,titanium alloy,magnesium alloy,and PEEK)on the biomechanics of the OWHTO fixation system were studied using finite element analysis.The biomechanical differences between the anatomical fixation plate and TomoFix fixation plate were also compared.Results The thickness had a greater effect on the micromotion of the osteotomy space than the length and width of the fixation plate did.Titanium alloy or magnesium alloy fixation plates were more conducive than stainless steel and PEEK materials in obtaining reasonable stability and mechanical transfer simultaneously.Compared with that of the TomoFix plate,the maximum von Mises stress of the anatomical fixation plate was reduced by 13.5%;the maximum von Mises stress of the screws and tibia was increased by 9.8%and 18.4%,respectively;and the micromotion at the maximum osteotomy space cc was increased by 49.3%.Conclusions Anatomical fixation plates have a positive effect on reducing the stress-shielding effect and improving biomechanical properties under the premise of ensuring stability.This study provides a reference for the development of OWHTO anatomical fixation plates.

Objective:To evaluate the mechanical performance of customized metal prosthesis with tibia stems of varying lengths for tibial bone defects reconstruction.Methods:Morphologically matched postoperative finite element models of bone defect revision were developed, with three gradients (15 mm, 30 mm, and 45 mm) according to the degree of bone defect and were reconstructed with 3D printed tantalum metal prosthesis using three tibial stem lengths (80 mm, 120 mm, and 150 mm), respectively. Conventional static and dynamic (walking gait) loading was performed to analyze the peak tibial stress distribution and accumulated sliding distance at the prosthetic interface, and to assess the effects of the three tibial stems of different lengths on the stability of the customized tibial defect restorations and the internal tibial stress state.Results:The peak accumulated sliding distance of the dynamically loaded morphologically matched restorations ranged from 17.94 to 21.31 mm with static loading, which were 68% to 84.3% higher than those of 10.26 to 11.69 mm with static loading. The peak tibial stresses in the dynamically loaded model were greater than those in the statically loaded model, with an increase of 28%-49.2%, including 132.94-143.88 MPa in the statically loaded model and 170.41-200.14 MPa in the dynamically loaded model. The overall accumulated sliding distance of the tibia prosthetic model gradually decreased from the tibial osteotomy surface, and the accumulated peak sliding distances ranged from 10.26 to 11.69 mm for static loading, and from 17.94 to 21.31 mm for dynamic loading. The bone tissue stresses in the anterolateral and medial-posterior tibia increased gradually from top to bottom, and the maximum stress value in each section was in the posterior medial tibia (the maximum value was 200.14 MPa). The highest bone tissue stress in the lateral tibia was affected by the tibial stem length, which resulted in a different location, and it was the area most affected by stress shielding (maximum value of 170.65 MPa).Conclusion:For stability assessment of morphologically matched tantalum customized prosthesis, physiological gait dynamic loading studies are more reliable than static loading; the choice of tibial stem length depends on a combination of accumulated peak sliding distances and tibial bone stress distribution factors.

Objective:To investigate the expression of Agmatinase (AGMAT) in breast cancer and its effect on the proliferation, migration and invasion of breast cancer cell lines.Methods:The expression levels of AGMAT in cancer and adjacent tissues of 1 094 breast cancer samples in The Cancer Genome Atlas (TCGA) database were analyzed. And its expression degree was verified in breast cancer cell lines MDA-MB-231, MCF-7, HCC-1937 and T-47D. The expression of AGMAT in breast cancer cells was knocked down by shRNA, and the expression level of AGMAT mRNA was detected by real-time fluorescence quantitative polymerase chain reaction (RT-qPCR), and the protein expression level was detected by Western blotting assay. Cell count and MTT assay were used to detect cell proliferation. Cell apoptosis and cell cycle changes were detected by flow cytometry. Cell migration ability was detected by cell scratch assay, cell invasion ability was detected by Transwell assay, and the expression level of related proteins in cells was detected by Western blotting assay. Measurement data were expressed as mean ± standard deviation ( ± s), comparisons between multiple groups were performed using ANOVA, pairwise comparisons were performed using independent samples t-test, and Tukey′s post hoc multiple test was used. Results:Analyzing the data of breast cancer samples in TCGA database, it was found that the expression level of AGMAT in cancer tissues was significantly higher than that in adjacent tissues ( FC=10.537, P<0.001). Flow cytometry showed that knocking down the expression of AGMAT inhibited the proliferation of breast cancer cells, and induced cell apoptosis [(3.20±0.10)% vs (6.83±0.06)%, t=62.35, P<0.001], and caused G 1 cell cycle arrest [(49.51±2.22)% vs (31.44±1.67)%, t=42.56, P=0.001]. The results of cell scratch assay and Transwell assay showed that decreased GMAT expression could reduce the cell migration ability [(34.27±1.67) % vs (57.97±0.58) %, t=33.52, P<0.001], invasive ability (163.00±1.77 vs 61.00±0.74, t=52.50, P<0.001). The results of Western blotting assay showed that the protein expression levels of Twist, Vimentin, matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) decreased, while the protein expression level of E-cadherin increased. AGMAT was involved in the process of epithelial-mesenchymal transition in breast cancer. Conclusion:AGMAT can be used as a prospective biomarker affecting the invasion, metastasis and therapeutic targets of breast cancer.

The surgical installation accuracy of the components in unicompartmental knee arthroplasty (UKA) is an important factor affecting the joint function and the implant life. Taking the ratio of the medial-lateral position of the femoral component relative to the tibial insert (a/A) as a parameter, and considering nine installation conditions of the femoral component, this study established the musculoskeletal multibody dynamics models of UKA to simulate the patients' walking gait, and investigated the influences of the medial-lateral installation positions of the femoral component in UKA on the contact force, joint motion and ligament force of the knee joint. The results showed that, with the increase of a/A ratio, the medial contact force of the UKA implant was decreased and the lateral contact force of the cartilage was increased; the varus rotation, external rotation and posterior translation of the knee joint were increased; and the anterior cruciate ligament force, posterior cruciate ligament force and medial collateral ligament force were decreased. The medial-lateral installation positions of the femoral component in UKA had little effect on knee flexion-extension movement and lateral collateral ligament force. When the a/A ratio was less than or equalled to 0.375, the femoral component collided with the tibia. In order to prevent the overload on the medial implant and lateral cartilage, the excessive ligament force, and the collision between the femoral component and the tibia, it is suggested that the a/A ratio should be controlled within the range of 0.427-0.688 when the femoral component is installed in UKA. This study provides a reference for the accurate installation of the femoral component in UKA.
Humans ; Arthroplasty, Replacement, Knee ; Knee Joint/surgery* ; Knee Prosthesis ; Gait ; Rotation

Posterior-stabilized total knee prostheses have been widely used in orthopedic clinical treatment of knee osteoarthritis, but the patients and surgeons are still troubled by the complications, for example severe wear and fracture of the post, as well as prosthetic loosening. Understanding the in vivo biomechanics of knee prostheses will aid in the decrease of postoperative prosthetic revision and patient dissatisfaction. Therefore, six different designs of posterior-stabilized total knee prostheses were used to establish the musculoskeletal multibody dynamics models of total knee arthroplasty respectively, and the biomechanical differences of six posterior-stabilized total knee prostheses were investigated under three simulated physiological activities: walking, right turn and squatting. The results showed that the post contact forces of PFC Sigma and Scorpio NGR prostheses were larger during walking, turning right, and squatting, which may increase the risk of the fracture and wear as well as the early loosening. The post design of Gemini SL prosthesis was more conductive to the knee internal-external rotation and avoided the edge contact and wear. The lower conformity design in sagittal plane and the later post-cam engagement resulted in the larger anterior-posterior translation. This study provides a theoretical support for guiding surgeon selection, improving posterior-stabilized prosthetic design and reducing the prosthetic failure.
Arthroplasty, Replacement, Knee/methods* ; Biomechanical Phenomena ; Humans ; Knee Joint/surgery* ; Knee Prosthesis ; Prosthesis Design ; Range of Motion, Articular/physiology* ; Tibia/surgery*

Objective To investigate the biomechanical effects of femoral offset (FO) on total hip arthroplasty (THA) patients with developmental dysplasia of the hip (DDH). Methods Based on the musculoskeletal dynamic software AnyBody and the related data from a female patient with Crowe Ⅳ DDH, the corresponding patient-specific lower extremity musculoskeletal multi-body dynamic model was constructed to analyze both hip joint forces and abductor forces within ±20 mm variation of FOs. The dynamic finite element (FE) model of S-ROM stem with varying offsets was also established. The dynamic load during a whole walking gait cycle calculated by the multi-body musculoskeletal model was applied to this FE models, and the Von Mises stress, contact stress, and stem-sleeve micromotion were then analyzed. Results A variation of ±20 mm offset had small influences on peak forces of hip joints. However, the decrease in FO could lead to an obvious increase in peak abductor force, while the increase in FO could lead to an obvious increase in the maximum Von Mises stress, contact stress, and micromotion of S-ROM prosthesis stem. Conclusions The change in FO had an obvious influence on the abductor forces, the maximum Von Mises stress, the contact pressure and the consequent fretting wear of THA patients with DDH, which should be carefully considered by surgeons.

Osteoarthritis are usual disease in middle aged and elderly people. High tibial osteotomy is a common method which performed to treat medial compartment osteoarthritis in varus knees. Unicondylar knee arthroplasty is an established treatment option for symptomatic osteoarthritis isolated to one compartment, and received remarkably effect. Total knee arthroplasty is the standard treatment of serious knee disease. The knee kinematics have changed after the knee was diseased, and the kinematics after surgery are different from the natural joint. The flexion-extension rotation, anterior-posterior translation and interior-exterior rotation are most important kinematics of tibia-femur joint. The anterior-posterior translation and interior-exterior rotation, which as the secondary kinematics, even are paradoxical after total knee arthroplasty. Secondary kinematics studies played an important role in prosthesis design and postoperative functional assessment. Measurement and description methods of knee joint secondary kinematics were reviewed in this article. The factors influencing secondary kinematics were investigated for natural knee joint, osteoarthritis knee joint and knee joint after total knee replacement separately, and the influence of total knee replacement design was emphasized. At last, the impact of knee secondary kinematics to biomechanics, friction and wear were also introduced. After comparison of multi-research results, the measurement precision was found to need further improvement due to the restrict of measuring technology and description methods. Many factors influence knee secondary kinematics, including activities, measurement environment and individual difference. The anterior-posterior translation was found complex after total knee replacement, and the prosthesis design played an important role. Posterior cruciate ligament-retaining knee replacement lead forward slide of the femoral component during flexion, which paradoxical from natural knee. The anatomical design prosthesis were hopeful to realize more natural kinematics. The component malalignment and soft tissue balance during surgey also have significant role in knee secondary kinematics. The knee secondary kinematics study is of great significance to biomechanics and wear.

Objective To investigate the feasibility and primary clinical outcomes of a kind of independent research and development customized 3D printed external fixator in the treatment of tibial fracture.Methods Data of 7 tibial fracture patients who were treated using computer-assisted reduction and 3D printing technique including a new kind of customized external fixator with automatical reduction function from December 2013 to November 2015 were retrospectively analyzed.There were 5 males and 2 females in this cohort.The age of the patients ranged from 25 to 49 years old,with an average age of 38.1 years old.The procedure was as follows.At first,two or three pins were placed separately into the distal and proximal tibia away from fracture site.Then,the CT scanning was performed on the fractured tibia.According to the CT scanning data,the external fixator was designed by computer software and manufactured by the 3D printing technique.The reduction of tibial fracture was achieved automatically after the 3D printed external fixator was connected to the inserted pins.Finally,the accuracy of reduction was assessed by postoperative X-ray image.During the different fracture healing course,the stress environment could be dynamically adjusted by screwing or unscrewing the nuts to fulfill rigid fixation,compression fixation or elastic fixation for the bone healing.Results All the 7 cases had obtained successful reduction by only one time operation with the 3D printed external fixators.The average lateral angulation was 1.42°± 1.13°,and the average anteroposterior angulation was 1.65°± 1.36°,while the average lateral displacement was 1.38± 1.44 mm,and the average anteroposterior displacement was 1.83± 1.30 mm,which were measured from postoperative X-ray image.The individual durations of the operation were 9 min,8 min,9 min,1.5 min,1.4 min,1.4 min and 2.4 min,respectively.All fractures had achieved bony union in 19-25 weeks after operation,with an average time of 21.4±1.6 weeks.All patients were followed up for 6 months when removal of the external fixator,and no refracture occurred.Conclusion The customized 3D printed external fixator has the function of automatical reduction.In addition,it can provide three kinds of fixation modes,which are rigid fixation,compression fixation and elastic fixation.It has the advantages of simple operation,accurate reduction,reasonable fixation,etc.

Objective To explore the influence of cucurbitacin E (CuE) on autophagy in human bladder cancer cell line T24 and further study its impacts on cell proliferation. Methods MTT assay was used to determine the proliferation inhibition capacity of CuE on T24 and western blot to check the impacts of CuE treatment on the expression of classic autophagy markers LC3A/B and p62. LC3 turnover assay and GFP-RFP-LC3 fluorescent assay were performed to determine autophagy flux. Western-blot was used to check the autophagy inhibition ability of 3-MA on CuE treatment and MTT assay and cell counting assay were used to check the influence of CuE-induced autophagy on cell proliferation with/without autophagy inhibition. Results CuE inhibited the proliferation of T24 and the IC50 in 24 h was about 0.75 μmol/L. CuE treatment increased the expression of LC3A/B Ⅱ and LC3A/B Ⅱ/Ⅰ ratio (P < 0.05) , but decreased the expression of p62 (P < 0.05) , indicating the induction of autophagy. Autophagy flux was induced because of positive LC3 turnover assay and the increase of yellow and red dots in GFP-RFP-LC3 fluorescent assay (P < 0.05). CuE-induced autophagy was inhibited by 3-MA (P < 0.05). With autophagy inhibition, CuE's proliferation suppression ability on T24 was attenuated (P <0.05). Conclusion CuE induces autophagy in bladder cancer cell line T24 and the induced autophagy positively contributes to the inhibitation of cell proliferation.