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BACKGROUND:Anterior cruciate ligament injury tends to lead to secondary meniscus injury and osteoarthritis.At present,there are few studies on the mechanics of meniscus and articular cartilage injury caused by anterior cruciate ligament injury. OBJECTIVE:To study the effect of partial rupture of the anterior cruciate ligament on the stress of medial and lateral meniscus and articular cartilage of knee joint by finite element analysis. METHODS:The CT and MRI images of the knee joint of a healthy volunteer were selected,and the scan data were imported into Mimics,Geomagic and SolidWorks software.After registration and fusion,four kinds of three-dimensional knee joint models were established:models of intact anterior cruciate ligament,rupture of the posterior external tract of anterior cruciate ligament,rupture of the anterior internal tract of anterior cruciate ligament,and absence of anterior cruciate ligament.Finally,data were imported into Ansys software to apply four different modes of loads to the knee joint:Longitudinal loads of 750 N were applied to the top of the femur;longitudinal load of 750 N to the top of the femur and forward thrust of 134 N behind tibia;a longitudinal load of 750 N and a varus moment of 10 Nm were applied to the top of the femur to simulate genu varus;750 N longitudinal load and 4 Nm internal rotation moment were applied to the proximal end of the femur to simulate knee internal rotation.The finite element analysis of biomechanical stress changes of the meniscus and articular cartilage of the knee joint was carried out. RESULTS AND CONCLUSION:(1)In the straight position of the knee joint,when the anterior medial tract of the anterior cruciate ligament was broken and the anterior cruciate ligament was missing under longitudinal loads of 750 N at the top of the femur,the total stress and peak value of meniscus increased significantly,but the stress distribution of the meniscus and the stress of articular cartilage did not change significantly.In longitudinal load of 750 N to the top of the femur and forward thrust of 134 N behind tibia,the fracture of the anterior internal tract of the anterior cruciate ligament increased the tibia forward,the compressive stress of posterior angle of the meniscus increased,and the stress of the articular cartilage did not change significantly.During simulating genu varus,the posterior angular stress of the lateral meniscus decreased,the stress of the medial meniscus increased,and the stress of articular cartilage slightly decreased when anterior cruciate ligament injuries were complete.When the anterior internal tract of the anterior cruciate ligament was broken or absent under knee internal rotation,the equivalent stress peak value of femoral cartilage and tibia cartilage shifted from medial cartilage to lateral cartilage,and the stress peak value of meniscus increased significantly.At this time,the anterior internal tract of the anterior cruciate ligament played a leading role in the rotational stability of the knee joint.(2)These results indicate that the risk of secondary meniscus injury in patients with anterior and medial anterior cruciate ligament band rupture was much higher than that in patients with posterior and external anterior cruciate ligament band rupture when the knee was in the upright standing position,varus and pronation,and there was no significant difference in the impact on articular cartilage.
ABSTRACT
Introduction: With the enhancement of people's health awareness and the impact of the coronavirus pandemic in recent years, people's demand for online health information continues to expand, and online health communities (OHCs) have developed rapidly. However, the service quality of OHCs is uneven, and problems such as content quality, privacy disclosure are increasingly prominent. It's of great significance to establish normalized OHC service quality evaluation standards and develop effective evaluation tools and methods for the improvement of OHC service quality. Material and Methods: Based on the grounded theory, the raw materials obtained from semi-structured interviews were coded in three stages to construct a service quality evaluation system for OHC. Through empirical analysis, the rationality and effectiveness of the evaluation system were verified. Then six representative Chinese OHCs were selected and their service quality was evaluated by the entropy weight TOPSIS method. Results: The service quality evaluation system of OHC was constructed which includes 4 first-level indicators and 16 second-level indicators. The weights of the first-level indicators from large to small are content quality, emotional experience quality, interaction quality and function quality. Among the second-level indicator weights, the top three are perceived cost reasonableness, content professionalism and effectiveness of interactive content. Conclusions: The indicator system is reasonable and effective and the evaluation method has strong applicability and operability. This study will provide theoretical guidance for community platform operators and relevant departments to design effective evaluation mechanism of OHC service quality, offering a reference for decisions and policymakers.
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AIM To analyze the dynamic changes of five constituents in Ligustri lucidi Fructus at five picking time (August,September,October,November,December).METHODS The HPLC analysis of Ligustri lucidi Fructus ethanol extract was performed on a 25 ℃ thermostatic Aglient Zorbax SB-C1s column (4.6 mm ×250 mm,5 μm),with the mobile phase comprising of acetonitrile-0.1％ phosphoric acid flowing at 1 mL/min in a gradient elution manner,and the detection wavelength was set at 224 nm.RESULTS Salidroside,tyrosol,luteolin-7-O-glucoside,ligustroflavone and specnuezhenide showed good linear relationships within their own ranges (r ＞0.999 0),whose average recoveries were 99.56％-100.30％ with the RSDs of 0.89％-1.23％.The contents of various constituents (except for tyrosol) were the highest in samples picked up in September,followed by those picked up in October.CONCLUSION The suitable picking time of Ligustri lucidi Fructus is September and October.