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

The morphometry of soft tissue insertions on the tibial plateau: Data acquisition and statistical shape analysis

This study characterized the soft tissue insertion morphometrics on the tibial plateau and their inter-relationships as well as variabilities. The outlines of the cruciate ligament and meniscal root insertions along with the medial and lateral cartilage on 20 cadaveric tibias (10 left and 10 right knees) were digitized and co-registered with corresponding CT-based 3D bone models. Generalized Procrustes Analysis was employed in conjunction with Principal Components Analysis to first create a geometric consensus based on tibial cartilage and then determine the means and variations of insertion morphometrics including shape, size, location, and inter-relationship measures. Step-wise regression analysis was conducted in search of parsimonious models relating the morphometric measures to the tibial plateau width and depth, and basic anthropometric and gender factors. The analyses resulted in statistical morphometric representations for Procrustes-superimposed cruciate ligament and meniscus insertions, and identified only a few moderate correlations (R 2: 0.37-0.49). The study provided evidence challenging the isometric scaling based on a single dimension frequently employed in related morphometric studies, and data for evaluating cruciate ligament reconstruction strategies in terms of re-creating the native anatomy and minimizing the risk of iatrogenic injury. It paved the way for future development of computer-aided personalized orthopaedic surgery applications improving the quality of care and patient safety, and biomechanical models with a better population or average representation

Predicting youth participation in urban agriculture in Malaysia: insights from the theory of planned behavior and the functional approach to volunteer motivation

This study examines factors associated with the decision of Malaysian youth to participate in a voluntary urban agriculture program. Urban agriculture has generated significant interest in developing countries to address concerns over food security, growing urbanization and employment. While an abundance of data shows attracting the participation of young people in traditional agriculture has become a challenge for many countries, few empirical studies have been conducted on youth motivation to participate in urban agriculture programs, particularly in non-Western settings. Drawing on the theories of planned behavior and the functional approach to volunteer motivation, we surveyed 890 students from a public university in Malaysia about their intention to join a new urban agriculture program. Hierarchical regression findings indicated that the strongest predictor of participation was students’ attitude toward urban agriculture, followed by subjective norms, career motives and perceived barriers to participation. The findings from this study may provide useful information to the university program planners in Malaysia in identifying mechanisms for future students’ involvement in the program

Current opinion on the role of testosterone in the development of prostate cancer: a dynamic model

Background: Since the landmark study conducted by Huggins and Hodges in 1941, a failure to distinguish between the role of testosterone in prostate cancer development and progression has led to the prevailing opinion that high levels of testosterone increase the risk of prostate cancer. To date, this claim remains unproven. Presentation of the Hypothesis: We present a novel dynamic mode of the relationship between testosterone and prostate cancer by hypothesizing that the magnitude of age-related declines in testosterone, rather than a static level of testosterone measured at a single point, may trigger and promote the development of prostate cancer. Testing of the Hypothesis: Although not easily testable currently, prospective cohort studies with population-representative samples and repeated measurements of testosterone or retrospective cohorts with stored blood samples from different ages are warranted in future to test the hypothesis. Implications of the Hypothesis: Our dynamic model can satisfactorily explain the observed age patterns of prostate cancer incidence, the apparent conflicts in epidemiological findings on testosterone and risk of prostate cancer, racial disparities in prostate cancer incidence, risk factors associated with prostate cancer, and the role of testosterone in prostate cancer progression. Our dynamic model may also have implications for testosterone replacement therapy

COMPARATIVE ACCURACY OF A NOVEL APPROACH TO AUTOMATIC TEMPORAL EVENT DETECTION DURING DROP VERTICAL JUMP

Jacob M. Thomas1, Jamie B. Hall1, Rebecca A. Bliss1, Trent M. Guess1 1University of Missouri, Columbia, Missouri Motion capture technology can add meaningful insight to the drop vertical jump (DVJ); however, these systems are quite expensive. PURPOSE: Therefore, the purpose of this study was to compare a low-cost depth-sensing camera (DSC) with body tracking software to the gold standard optical retroreflective motion capture system (OMC) in detecting the timing of initial ground contact (IGC) and maximum knee flexion (MKF) using a novel approach to automatic IGC detection without a force plate. This approach was also validated with force plate IGC detection. METHODS: This pilot study included 19 individuals (24.16±2.39 yrs, 174.66±9.42 cm, 72.79±10.13 kg). Participants were fitted with retroreflective markers and completed 5 DVJ repetitions from a 31 cm box onto 2 force plates (right foot, left foot) sampling at 1000 Hz. Each trial was simultaneously recorded using a 12-camera OMC sampling at 100 Hz, and a DSC sampling at 30 Hz placed 2.7 m from the capture space, and 1.0 m above the ground in the frontal plane. A custom MATLAB (version 2019b) algorithm detected the moment left and right ankle joint centers crossed below 180 mm (relative to ground) in the vertical plane for both devices. Right and left times were averaged to determine IGC. Maximum right and left knee flexion values within 1 second following IGC were averaged to determine MKF for both devices. Force plate IGC was defined as the moment vertical ground reaction force exceeded 10% of participant body mass. Because the DSC and OMC could not be synchronized, time difference between MKF and IGC was analyzed as a measure of accuracy between the two. For this study, results of 1 trial were analyzed. ICC values measured agreement in time differences for all systems. Statistical analysis was performed in RStudio (version 4.1.1). RESULTS: ICC values indicated perfect agreement between kinematic calculation of IGC using the OMC and force plate calculation of IGC (ICC(3,k) = .99, p\u3c.001). Average difference between MKF and IGC for the OMC was 0.29±0.12 seconds. For the DSC, average difference was 0.28±0.12 seconds. ICC values were very high between the DSC and OMC (ICC(3,k) = 0.99, p\u3c.001) when comparing time between MKF and IGC. CONCLUSION: As this was a pilot study, findings are limited in their generalizability due to a reduced sample size. However, this work demonstrates that a single DSC can detect IGC and MKF events during DVJ, which could be useful for event detection in clinics where force plates are not available. Future studies should evaluate the usefulness of this technique using a greater and more diverse sample population, in order to further assess its accuracy. ACKNOWLEDGEMENTS: This study was funded in part by the University of Missouri Coulter Biomedical Accelerator