Computational Knee Ligament Modeling Using Experimentally Determined Zero-Load Lengths

This study presents a subject-specific method of determining the zero-load lengths of the cruciate and collateral ligaments in computational knee modeling. Three cadaver knees were tested in a dynamic knee simulator. The cadaver knees also underwent manual envelope of motion testing to find their passive range of motion in order to determine the zero-load lengths for each ligament bundle. Computational multibody knee models were created for each knee and model kinematics were compared to experimental kinematics for a simulated walk cycle. One-dimensional non-linear spring damper elements were used to represent cruciate and collateral ligament bundles in the knee models. This study found that knee kinematics were highly sensitive to altering of the zero-load length. The results also suggest optimal methods for defining each of the ligament bundle zero-load lengths, regardless of the subject. These results verify the importance of the zero-load length when modeling the knee joint and verify that manual envelope of motion measurements can be used to determine the passive range of motion of the knee joint. It is also believed that the method described here for determining zero-load length can be used for in vitro or in vivo subject-specific computational models

Preliminary study of a customised total knee implant with musculoskeletal and dynamic squatting simulation

Customised total knee replacement could be the future therapy for knee joint osteoarthritis. A preliminary design of a customised total knee implant based on knee anatomy was studied in this article. To evaluate its biomechanical performance, a dynamic finite element model based on the Oxford knee rig was created to simulate a squatting motion. Unlike previous research, this dynamic model was simulated with patient-specific muscle and joint loads that were calculated from an OpenSim musculoskeletal model. The dynamic response of the customised total knee implant was simulated under three cruciate ligament scenarios: both cruciate ligaments retained, only anterior cruciate ligament removed and both cruciate ligaments removed. In addition, an off-the-shelf symmetric total knee implant with retained cruciate ligaments was simulated for comparison analysis. The customised total knee implant with both cruciate ligaments retained showed larger ranges of femoral external rotation and posterior translation than the symmetric total knee implant. The motion of the customised total knee implant was also in good agreement with a healthy knee. There were no big differences in the tibiofemoral compressive forces in the customised total knee implant model under the three scenarios. These forces were generally consistent with other experimental and simulation results. However, the customised total knee implant design resulted in larger tibiofemoral compressive force than the symmetric total knee implant after 50° knee flexion, which was caused by the larger tibiofemoral relative motion

Strategies Utilized to Transfer Weight During Knee Flexion and Extension With Rotation for Individuals With a Total Knee Replacement

Functional activities in daily life can require squatting and shifting body weight during transverse plane rotations. Stability of the knee can be challenging for people with a total knee replacement (TKR) due to reduced proprioception, nonconforming articular geometry, muscle strength, and soft tissue weakness. The objective of this study was to identify strategies utilized by individuals with TKR in double-stance transferring load during rotation and flexion. Twenty-three subjects were recruited for this study: 11 TKR subjects (age: 65 6 6 years; BMI 27.4 6 4.1) and 12 healthy subjects (age: 63 6 7; BMI 24.6 6 3.8). Each subject completed a novel crossover button push task where rotation, flexion, and extension of the knee were utilized. Each subject performed two crossover reaching tasks where the subject used the opposite hand to cross over their body and press a button next to either their shoulder (high) or knee (low), then switched hands and rotated to press the opposite button, either low or high. The two tasks related to the order they pressed the buttons while crossing over, either low-to-high (L2H) or high-to-low (H2L). Force platforms measured ground reaction forces under each foot, which were then converted to lead force ratios (LFRs) based on the total force. Knee flexion angles were also measured. No statistical differences were found in the LFRs during the H2L and L2H tasks for the different groups, although differences in the variation of the loading within subjects were noted. A significant difference was found between healthy and unaffected knee angles and a strong trend between healthy and affected subject's knee angles in both H2L and L2H tasks. Large variations in the LFR at mid-task in the TKR subjects suggested possible difficulties in maintaining positional stability during these tasks. The TKR subjects maintained more of an extended knee, which is a consistent quadriceps avoidance strategy seen by other researchers in different tasks. These outcomes suggest that individuals with a TKR utilize strategies, such as keeping an extended knee, to achieve rotary tasks during knee flexion and extension. Repeated compensatory movements could result in forces that may cause difficulty over time in the hip joints or low back. Early identification of these strategies could improve TKR success and the return to activities of daily living that involve flexion and rotation

Development and research of ointment with essential oil of thyme for the treatment of the scalp and hair parts of the head

Dermatological diseases are the most widespread in the whole world. According to WHO, 20–30% of the world's population suffers from fungal skin diseases and 25–35% from pustular diseases. Pustular diseases (pyoderma) are the result of pathogenic staphylococci and streptococci, and fungal diseases (dermatomycoses) are caused by various types of fungi. Today, these diseases are treated with various types of drugs, but the active ingredient in almost all of them is synthetic compounds (antibiotics, sulfonamides, imidazole derivatives, etc.). Medicines of natural origin are scarce. In order to increase the number of phytoremedies for external use (ointments), which have medicinal plant active components, a study was conducted using standardized essential oil of common thyme. The aim of the work was to study the effect of excipients on the ointment base by the method of mathematical planning of the experiment for the development of the optimal composition of the dermatological ointment with the essential oil of common thyme. Excipiennts for ointment bases of hydrophobic and emulsion composition were used to develop the optimal composition of the ointment. The concentration of thyme essential oil was 5% in all samples. The degree of thymol release in an in vitro study using the equilibrium dialysis method was chosen as the criterion for choosing the optimal composition. Excipiennts allowed in pharmacy, with known characteristics, safety profile, and application experience were used as auxiliary substances. Using Duncan's multiple criterion, a number of advantages were created: а7 > а8 > а9 > а10 > а6 >а2 > а5 > а3 > а1 > а4. On the basis of the conducted studies, the optimal composition of the ointment was chosen for the treatment of lesions of the scalp and hair. The studied organoleptic and technological properties and quality indicators (homogeneity, colloidal stability, thermal stability, microbiological purity) of ointment with thyme essential oil during long-term storage at a temperature of +2–+8 °C established the stability of the developed composition of the ointment during two years of observation. The creation of a new local remedy for the treatment of lesions of the scalp and its hair part will allow to expand the arsenal of safe and effective remedies

A novel device to measure power grip forces in squirrel monkeys

Understanding the neural bases for grip force behaviors in both normal and neurologically impaired animals is imperative prior to improving treatments and therapeutic approaches. The present paper describes a novel device for the assessment of power grip forces in squirrel monkeys. The control of grasping and object manipulation represents a vital aspect of daily living by allowing the performance of a wide variety of complex hand movements. However, following neurological injury such as stroke, these grasping behaviors are often severely affected, resulting in persistent impairments in strength, grip force modulation and kinematic hand control. While there is a significant clinical focus on rehabilitative strategies to address these issues, there exists the need for translational animal models. In the study presented here, we describe a simple grip force device designed for use in nonhuman primates, which provides detailed quantitative information regarding distal grip force dynamics. Adult squirrel monkeys were trained to exceed a specific grip force threshold, which was rewarded with a food pellet. One of these subjects then received an infarct of the M1 hand representation area. Results suggest that the device provides detailed and reliable information on grip behaviors in healthy monkeys and can detect deficits in grip dynamics in monkeys with cortical lesions (significantly longer release times). Understanding the physiological and neuroanatomical aspects of grasping function following neurological injury may lead to more effective rehabilitative interventions

Development of an in vitro three dimensional loading-measurement system for long bone fixation under multiple loading conditions: a technical description

The purpose of this investigation was to design and verify the capabilities of an in vitro loading-measurement system that mimics in vivo unconstrained three dimensional (3D) relative motion between long bone ends, applies uniform load components over the entire length of a test specimen, and measures 3D relative motion between test segment ends to directly determine test segment construct stiffness free of errors due to potting-fixture-test machine finite stiffness

Computational Modelling of Patella Femoral Kinematics During Gait Cycle and Experimental Validation

The effect of loading and boundary conditions on patellar mechanics is significant due to the complications arising in patella femoral joints during total knee replacements. To understand the patellar mechanics with respect to loading and motion, a computational model representing the patella femoral joint was developed and validated against experimental results. The computational model was created in IDEAS NX and simulated in MSC ADAMS/VIEW software. The results obtained in the form of internal external rotations and anterior posterior displacements for a new and experimentally simulated specimen for patella femoral joint under standard gait condition were compared with experimental measurements performed on the Leeds ProSim knee simulator. A good overall agreement between the computational prediction and the experimental data was obtained for patella femoral kinematics. Good agreement between the model and the past studies was observed when the ligament load was removed and the medial lateral displacement was constrained. The model is sensitive to ±5 % change in kinematics, frictional, force and stiffness coefficients and insensitive to time step

Verification of a dynamic knee simulator computational model

Dynamic knee simulators aim to reproduce prescribed physiological loading and motions of the knee. The natural knee achieves stability through a complex interaction of the neuro-musculoskeletal system; thus, a knee simulator also requires a sophisticated control system to replicate human motion. Guess and Maletsky [1] developed a computational model to predict the required simulator inputs to produce the desired knee loading for dynamic activities on the Kansas Knee Simulator (KKS). The model built demonstrated conceptually that multi-body dynamics models could be used to simulate the KKS. However, as desired loading profiles became more complex, key limitations were discovered in the model; such as the model controller limited to a single axis under feedback control, no out-of-plane loading, not accounting for dynamic joint friction or damping of the actuators, and an inability of the model to flex pass 80° degrees of knee flexion. Thus, there was a need for a new computational model to overcome the limitations and to provide a more robust and complete comparison to the KKS. The new computational model will allow better utilization of the KKS capabilities for future cadaveric and prosthetic testing. This work outlines the sagittal-plane validation of the new computational model

Mengajar matematika : sebuah buku sumber alat peraga, aktivitas, dan strategi untuk guru matematika SD, SMP, SMA

Judul asli : Teaching mathematics: a soucebook of aids, activities, and strategies 3rd ed.x, 270 p. : il.; 24 c