Design of Porous Metal Block Augmentation to Treat Tibial Bone Defects in Total Knee Arthroplasty Based on Topology Optimization.

Metal block augmentation, which is used for the treatment of tibial bone defects in total knee arthroplasty, with high stiffness will cause significant alteration in stress distribution, and its solid structure is not suitable for osseointegration. This study aimed to design a porous block to reduce weight, promote bone ingrowth, and improve its biomechanical performance. The metal block augmentation technique was applied to finite element models of tibial bone defects. Minimum compliance topology optimization subject to volume fraction combined with the porous architecture was adopted to redesign the block. Biomechanical changes compared with the original block were analyzed by finite element analysis. The stress distribution of the block and proximal tibia was recorded. The strain energy density of the proximal tibia was obtained. The newly designed block realized 40% weight reduction. The maximum stress in the optimized block decreased by 11.6% when compared with the solid one. The maximum stress of the proximal tibia in the optimized group increased by 18.6%. The stress of the anterior, medial, and posterior parts of the proximal medial tibia in the optimized group was significantly greater than that in the original group (all p < 0.05). The optimized block could effectively improve the biomechanical performance between the block and the bone. The presented method might provide a reference for the design of customized three-dimensional printed prostheses.

Metformin inhibits epithelial-mesenchymal transition of oral squamous cell carcinoma via the mTOR/HIF-1α/PKM2/STAT3 pathway.

Epithelial-mesenchymal transition (EMT) serves an important role in the formation and development of various types of cancer, including oral squamous cell carcinoma (OSCC). Metformin, used for treating type 2 diabetes, has been revealed to exert an anticancer effect in various types of cancer, including liver, breast and colorectal cancer. However, its role in the EMT of OSCC has been rarely reported. Therefore, the present study aimed to investigate the effects of metformin on EMT and to identify its underlying mechanism in OSCC. Firstly, EMT was induced in CAL-27 cells using CoCl2. Subsequently, the effects of metformin on cell viability, migration and xenograft growth were evaluated in vitro and in vivo. Reverse transcription-quantitative PCR was performed to detect the expression levels of E-cadherin, vimentin, snail family transcriptional repressor 1, mTOR, hypoxia inducible factor 1α, pyruvate kinase M2 and STAT3. The results demonstrated that metformin abolished CoCl2-induced cell proliferation, migration, invasion and EMT. Moreover, metformin reversed EMT in OSCC by inhibiting the mTOR-associated HIF-1α/PKM2/STAT3 signaling pathway. Overall, the present findings characterized a novel mechanism via which metformin modulated EMT in OSCC.

Biomechanical comparison between metal block and cement-screw techniques for the treatment of tibial bone defects in total knee arthroplasty based on finite element analysis.

BACKGROUND: Managing bone defects is a critical aspect of total knee arthroplasty. In this study, we compared the metal block and cement-screw techniques for the treatment of Anderson Orthopaedic Research Institute type 2A tibial bone defects from the biomechanical standpoint. METHOD: The metal block and cement-screw techniques were applied to finite element models of 5- and 10-mm tibial bone defects. Biomechanical compatibility was evaluated based on the stress distributions of the proximal tibia and tibial tray. The displacement of the tibial tray and maximum relative micromotion between the tibial stem and tibia were analyzed to assess the stability of the implant. RESULTS: The maximum stress in both the proximal tibia and tibial tray was greater with the cement-screw technique than with the metal block technique. The stress of the proximal lateral tibia with the cement-screw technique was significantly larger than with the metal block technique (p < 0.05). For the 5-mm bone defect, the maximum relative micromotion was lower than the critical value of 150 µm. For the 10-mm defect, the maximum relative micromotion was 128 µm with the metal block technique and 155 µm with the cement-screw technique, with the latter exceeding the critical value. CONCLUSIONS: The cement-screw technique showed superior biomechanical compatibility to the metal block technique and is more suitable for 5-mm bone defects. However, as it may reduce the fixation strength in 10-mm bone defects, the metal block technique is more appropriate in this case.

Sex determination from talus in Chinese population by three-dimensional measurement approach.

OBJECTIVE: The determination of sex is an essential part of building the biological profile for unknown human remains. Sex determination from talus in Chinese population has been rarely reported. The aim of this study was to determine sex by discriminant function analysis through talus measurement in Chinese population. METHODS: 48 male and 47 female Chinese northeast subjects were taken in this research. The ankle joints of these subjects were scanned by CT. In total, thirteen indexes were measured through Mimics and Magics software. Length and breadth indexes of total talus, trochlea, talar head, medial and lateral malleolus articular surface were mainly selected. Nine of them were measured through Mimics software. The other four indexes were measured through Magics software. All data were analyzed by independent-samples t-test in SPSS and Stata software. Discriminant function equations were generated for sex determination. RESULTS: All the indexes were normally distributed. No significant difference between left and right talus in either males or females was identified (P > 0.05). All results showed significant sexual difference (P < 0.05) except posterior breadth of trochlea. The average accuracy of sex determination ranged from 95.85% to 98.45% in the direct method and 98.95% in the stepwise method. CONCLUSIONS: Length indexes showed higher accuracy rate than breadth ones. Length of lateral malleolus articular surface was the best discriminator of sexual dimorphism. Talus was proved effective for sex determination in Chinese population. This study provided a remarkable reference for sex determination in forensic science.