ABSTRACT
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
BACKGROUND:The incidence of medial collateral ligament injuries in the knee joint is easy to lead to secondary meniscus and cartilage damage,and long-term chronic damage can lead to the occurrence of osteoarthritis.At present,there are few studies on the mechanics of meniscus and articular cartilage injury caused by medial collateral ligament rupture. OBJECTIVE:To investigate the effect of different degrees of medial collateral ligament injury on the biomechanics of meniscus and cartilage of knee joint. METHODS:The CT and MRI examinations of the knee joint of a healthy volunteer were performed to obtain the image data.The scanning data were imported into Mimics,Geomagic,and Solidworks software in turn.After registration and fusion,a 3D model of normal knee joint was established.On this basis,models of medial collateral ligament injury in different degrees of knee joint were simulated,which were divided into four groups,including:(1)medial collateral ligament was intact;(2)deep medial collateral ligament fracture;(3)superficial medial collateral ligament fracture;(4)complete rupture of medial collateral ligament.Finally,Ansys software was introduced to apply three modes of loads to the knee joint:(1)10 N·m valvaration torque was applied to the top of the femur.(2)A 4 N·m internal torque was applied to the top of the femur.(3)A 4 N·m external torque was applied to the top of the femur.The effects of four groups of models on knee biomechanics under different loads were analyzed. RESULTS AND CONCLUSION:(1)In the extension position of the knee joint,when a 10 N·m valgus torque was applied to the knee joint,the overall stress of the posterolateral meniscus increased with different degrees of medial collateral ligament injuries,while the stress of the articular cartilage did not change significantly.The peak stress of the posterolateral meniscus increased significantly with superficial medial collateral ligament rupture.(2)In the knee extension position,when a 4 N·m internal rotation torque was applied to the knee joint,the overall stress of the medial and lateral meniscus increased after different degrees of medial collateral ligament injury.When superficial medial collateral ligament rupture occurred,the peak stress of the meniscus shifted from the anterior horn of the medial meniscus to the anterior horn of the lateral meniscus.(3)In the knee extension position,applying a 4 N·m external rotation torque to the knee joint,the peak stress of the posterolateral meniscus increased more significantly than that of the medial meniscus,and the stress of the articular cartilage changed less.(4)These results show that the risk of meniscus injury secondary to superficial medial collateral ligament rupture is much higher than that of deep medial collateral ligament rupture when the knee is in extension,and the lateral meniscus is more vulnerable to injury than the medial meniscus.Both superficial medial collateral ligament and deep medial collateral ligament play an important role in the rotational stability of the knee joint.
ABSTRACT
Objective To study comparatively the clinical anaesthetic potency and adverse effects to children of 0.375% ropivacaine used for brachial plexus block in upper-limb paediatric surgery.Methods After undergoing basal anesthesia with ketamine,36 children scheduled for hand and forearm surgery were randomly allocated to receive brachial plexus block with 0.375% ropivacaine(group A) and to receive intravenous anesthesia with ketamine(group B).The effect of sensor block and motor block,the changes of vital sings,the occurrence of side effect(nausea and vomiting) and palinesthesia of children were observed.Results The patients in group A kept a steady vital signs,their blood pressure,cardiac and respiration rate were similar to the backgroud level before anesthesia,whereas in group B the blood pressure,cardiac and respiration rate of patients were increased and kept a rather higer level,fluctuated with the depth of anesthesia.Conclusion Ropivacaine used for brachial plexus block in upper-limb paediatric surgery is a simple,feasible,and safe method with anesthetized perfectly and less complication.
ABSTRACT
Fourly adult healthy patients were separately anesthetlzed with (1 )0. 95% isoflurane; (2) fentanyl 5g/kg and thiopentone 4 mg/kg; (3) upper thoracic epidural blockage and (4 ) lumbar epidural blockage,Continuous 5 min ECG were recorded before and a fier anesthesia with spectral analysis of heart rate varlability (HRV) performed by computer program. For power spectral measurement,three frequency band of HRV were evaluated and the effects of each anesthesia were compared. HRV reduced markedly in patients using 0. 95 % isoflurane. with decreases of frequency by 91. 7% (low frequency ), 84. 4% (mid frequency ). and 82% (high-frequency) respectively. In patients after administration of fentanyl 5g/kg, mid and high-frequency components declined 63. 4 % and 65. 4 %. Upper thoracic epidural block restrained the mid and low frequency components by 66 % and 65 % respectively, Following lumbar epidural block the pattern of HRV components did not change. It is concluded that different anesthesia techniques may have significant different effects on autonomic reflexes as presented by HRV.
ABSTRACT
Objective Using accurate monitoring,and high precision anesthetic machine and vapourizer,and guided with a simple mathematics formula to implement low-flow inhaled anesthetic techniques.Methods Ten healthy patients under going craniotomy,thoracotomy or laparotomy were assigned to receive isoflurane by low-flor of fresh gas and high vapourizer output.After intubation,the vapourizer dial was set at 5% and the patients were delivered with 1L/min total fresh gas flow of oxygen.The expiratory(F E) and inspired(F 1) concentration of isoflurane were monitored continuously.The data were recorded with computer once every 10. The concentrations were plotted against the time and the predicted regression equation were calculated.Results The F E reached 1.05% 10 min after inhalation of isoflurane ,which could be predicted by curvilinear(y=0 4092(1nx)+0 0172) and lineal (y=0 083x+0 1385) regression equations from 1 to 10 min,The predicted concentration by curvilinear regression equation appeared to estimate the measured value more accurately than linear regression equation.However segmental lineal regression equation cluld predict the measured value as accurately as curvilinear regression equation.Conclusions The inhalation anesthetic induction can be completed within 10 min with low-flow of fresh gas flow and high output of vapourizer dial setting.The measured value of anesthetic can be predicted accurately.