BODY KINEMATICS DURING SINGLE-LEG LANDING FROM VARYING HEIGHTS AND DISTANCES – IMPLICATIONS FOR NON-CONTACT ACL INJURIES: CASE REPORT

Single-leg landing is seen as one of the primary mechanisms of non-contact ACL injuries during sports. The objective of this study is to determine how body kinematics varies with changes to landing heights and distances, in order to make inferences based on body kinematics to risk of non-contact ACL injuries. Spearman’s correlation coefficient among selected body kinematics was determined. It was observed that the peak vertical ground reaction force (VGRF) decreased with increasing distance of landing for the male subject, but increased with increasing distance for the female subject. It was observed that knee flexion is highly correlated to landing height (ρ=0.78), and moderately correlated to distance (ρ=–0.65) for the female subject. Knee flexion moderately correlated to landing height and distance (ρ=0.65 and ρ=-0.58, respectively) for the male subject

Can the body slope of interference screw affect initial stability of reconstructed anterior cruciate ligament?: An in-vitro investigation

© The Author(s). 2021 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License. https://creativecommons.org/licenses/by/4.0/Background: Superior biomechanical performance of tapered interference screws, compared with non-tapered screws, with reference to the anterior cruciate ligament (ACL) reconstruction process, has been reported in the literature. However, the effect of tapered interference screw’s body slope on the initial stability of ACL is poorly understood. Thus, the main goal of this study was to investigate the effect of the interference screw's body slope on the initial stability of the reconstructed ACL. Methods: Based on the best screw-bone tunnel diameter ratios in non-tapered screws, two different tapered interference screws were designed and fabricated. The diameters of both screws were equal to bone tunnel diameter in one-third of their length from screw tip, then they were gradually increased by 1mm, in the lower slope (LSTIS), and 2 mm, in the higher slope (HSTIS) screws. To simulate the ACL reconstruction, sixteen soft tissue grafts were fixed, using HSTIS and LSTIS, in synthetic bone blocks. Through applying sub-failure cyclic incremental tensile load, graft-bone-screw construct's stiffness and graft laxity in each cycle, also through applying subsequent step of loading graft to the failure, maximum load to failure, and graft’s mode of failure were determined. Accordingly, the performance of the fabricated interference screws was compared with each other. Results: HSTIS provides a greater graft-bone-screw construct stiffness, and a lower graft laxity, compared to LSTIS. Moreover, transverse rupture of graft fibers for LSTIS, and necking of graft in the HSTIS group were the major types of grafts' failure. Conclusion: HSTIS better replicates the intact ACL's behavior, compared to LSTIS, by causing less damage in graft's fibers; reducing graft laxity; and increasing fixation stability. Nonetheless, finding the optimal slope remains as an unknown and can be the subject of future studies.Peer reviewedFinal Published versio

Impact of the components of Mediterranean nutrition regimen on long-term prognosis of diabetic patients with coronary artery disease

BACKGROUND: The impact of different nutritional regimens on long-term prognosis and outcome in diabetic patients with coronary artery disease (CAD) has been questioned. Therefore, the objective of the present study was to determine the effects of different nutritional components of Mediterranean regimen on long-term cardiovascular events in diabetic patients with CAD in the Iranian population. METHODS: In a prospective cohort study, we recruited 233 consecutive patients with the diagnosis of type 2 diabetes mellitus and with at least 6 months of documented CAD. Nutritional assessment was obtained by a validated semi-quantitative food frequency questionnaire (FFQ) and the diet score was calculated on the basis of the Mediterranean diet quality index (Med-DQI). For Assessing long-term CAD prognosis, the patients were followed by telephone for one year. The study endpoint was long-term Major Adverse Cardiac and Cerebrovascular event (MACCE). RESULTS: Death was observed in 19 patients (8.2) during the one-year follow-up. Two patients (0.9) suffered non-fatal myocardial infarction and 14 (6.0) needed revascularization within 1 year after discharge from hospital. Overall MACCE within one year in the study population was 12.4. There were significant differences between number of deaths and dietary scores of saturated fatty acid, cholesterol, meats, fish, and fruit and vegetables (P < 0.05). Moreover, significant differences were found between MACCE rate and dietary scores of saturated fatty acid, cholesterol, and fruit and vegetables (P < 0.05). Using multivariate logistic regression models, Mediterranean dietary regimen could effectively predict long-term death as well as MACCE adjusted for gender and age variables. CONCLUSION: Mediterranean dietary regimens, including low level of cholesterol and saturated fatty acid, can effectively improve long-term outcome including death and MACCE in diabetic patients with CAD

Barriers to Predicting the Mechanisms and Risk Factors of Non-Contact Anterior Cruciate Ligament Injury

High incidences of non-contact anterior cruciate ligament (ACL) injury, frequent requirements for ACL reconstruction, and limited understanding of ACL mechanics have engendered considerable interest in quantifying the ACL loading mechanisms. Although some progress has been made to better understand non-contact ACL injuries, information on how and why non-contact ACL injuries occur is still largely unavailable. In other words, research is yet to yield consensus on injury mechanisms and risk factors. Biomechanics, video analysis, and related study approaches have elucidated to some extent how ACL injuries occur. However, these approaches are limited because they provide estimates, rather than precise measurements of knee - and more specifically ACL - kinematics at the time of injury. These study approaches are also limited in their inability to simultaneously capture many of the contributing factors to injury

Theoretical aspects of bone remodeling and resorption processes

Bibliography: p. 198-221The ability of living bone to adapt its material structure and form to its mechanical loading is very well-known. Resorption of extra-cellular matrices by osteoclasts is followed by osteoblastic invasion of the cavity, and subsequent secretion of extra-cellular matrix. These sequential processes continuously occur in healthy bone in a balanced manner, and these are called bone remodeling. Optimal remodeling of bone is responsible for bone health and strength throughout life. Bone resorption and apposition are caused by chemical reactions that occur between bone matrix and bone cells. There is a need to develop a theory (or theories) that can help elucidate features of this complex process. Adaptive elasticity theory is one of the most rigorous and well-known mathematical models of bone remodeling. The theory of adaptive elasticity was developed as a model for the mechanical load induced adaptation of bone. It describes an elastic material that adapts its structure to applied loading. The strain adapting properties of living bone are represented by a strain-controlled chemical reaction that transfers mass, momentum, entropy and energy to and from the porous elastic solid. In the constitutive equations, volume fraction of the solid phase is used as one of the independent variables. But, knowing that all of the resorption and deposition of bone occur on the bone free surfaces, we propose free surface density instead of volume fraction in the constitutive equations. On the basis of this assumption, a new set of remodeling equations is derived. In this model, one can observe the effect of bone internal geometry and mass distribution on the rate of remodeling. Surface remodeling equation can be extracted from this model, also the effects of mechanical stimuli and bone internal geometry can be studied simultaneously. In the second phase of our research, a microcrack factor is introduced in the governing equations, and a new model is developed. This model agrees with experimental evidence and suggests that mechanical stimuli, their rates, and also their cumulative effects regulate the process. Considering the new remodeling equation, one can conclude that the rate of remodeling is not a function of the rate of damage production but rather a function of the damage factor. In the third step of this research, a mixture theory approach with chemical reactions is used to model the bone resorption process. Mechanical and chemical factors are considered, simultaneously, in this model. Rates of mass transferred by the chemical reactions between the solid and fluid phases are assumed from an empirical relation. Degree of saturation is assumed to be a function of the chemical affinity. The analysis is consistent with experimental observations that strain energy density and hydrostatic pressure are two mechanical stimuli which effect the rate of resorption. With increasing microcracks the rates of bone resorption and remodeling are expected to increase. Our model suggests that by increasing the concentration of calcium ions rate of resorption decreases