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Respiratory, endocrine, cardiac, and renal topics
Published in Evelyne Jacqz-Aigrain, Imti Choonara, Paediatric Clinical Pharmacology, 2021
Evelyne Jacqz-Aigrain, Imti Choonara
The numerous short and long-term side-effects of steroids are well known and discussed in detail elsewhere in this textbook (see chapter on rheumatic disorders). Studies performed in children with nephrotic syndrome have shown the prevalence of these side-effects to be similar to those reported in children receiving steroids for other indications. Posterior subcapsular cataract occurs in 10–38% of children, though one large well conducted study failed to show any association between cataract development and the cumulative dose of predniso-lone administered [8]. Data on growth on long-term alternate day steroid therapy in this condition are somewhat conflicting, and depend to some extent on the amount of steroid administered. Normal growth has been reported in pre-pubertal children [9, 10], though appears to fall off after 10 years of age, particularly in boys, in whom there is also some evidence of pubertal delay [11]. The small number of studies reporting final adult height data suggest only a minor reduction in this [12, 13]. Studies investigating bone mineral density have also reported conflicting results, partly due to variation in the methods and sites of measurement, though both reductions in both trabecular and cortical bone mineral density have been reported [14, 15].
Miscellaneous
Published in Bobby Krishnachetty, Abdul Syed, Harriet Scott, Applied Anatomy for the FRCA, 2020
Bobby Krishnachetty, Abdul Syed, Harriet Scott
The epiphysis of long bones is the typical insertion site for IO access. The three main layers are Periosteum – the outermost layer that surrounds the bone.Cortical bone – the middle layer, which is heavily mineralised and contains a network of blood vessels. The Haversian canals are vertical channels for blood vessels and nerves found on the outermost region of cortical bone and are connected by horizontal Volkmann canals. Concentric layers (lamellae) containing osteophytes surround the Haversian canals and interconnections between the channels and osteophytes are called canaliculi.Cancellous bone – the innermost layer and consists of multiple trabeculae in a lattice-like structure. The space between the trabeculae contains blood vessels and bone marrow. With correct placement, the tip of the IO needle lies within the cancellous bone.
Animal Models of Osteopenia or Osteoporosis
Published in Yuehuei H. An, Richard J. Friedman, Animal Models in Orthopaedic Research, 2020
Donald B. Kimmel, Erica L. Moran, Earl R. Bogoch
A further series of experiments focused on the mechanism of increased fracture risk in cortical bone. Inflammatory arthritis-induced loss of strength was demonstrated in rabbit femoral diaphyses from the limb affected by experimental tibiofemoral arthritis, showed a loss of ultimate strength of ~39%.304 Kang et al. documented osteopenia and decreased mechanical strength of the entire ipsilateral femur and tibia.305 Strips of femoral cortex from the carrageenan injection arthritis model, tested within the elastic range, demonstrated no significant alteration in the elastic and flexural modulus.306 Large defects in the femoral cortex were described307 and defined as disordered, giant resorption sites crossing osteonal borders and up to 1.2 mm in cross-sectional diameter.308 Cooke and Takashima identified an analogous porous lesion in the femoral neck of RA patients who underwent total hip replacement. Enlarged Haversian systems contained osteoclasts and vascular changes with tall endothelial cells.309 A simplified femoral shaft mathematical model predicted the loss of strength in the femoral cortex that would result from defects of the size observed in the carrageenan model. The calculated result, ~29% was reasonably concordant with the observed loss of strength (~39%).304,307
Gaps in evidence on treatment of male osteoporosis: a Research Agenda
Published in The Aging Male, 2023
Adam J. Rose, Susan L. Greenspan, Guneet K. Jasuja
Studies have shown that while osteoporosis is characterized by disordered bone among both men and women, it is disordered in different ways [12]. Further, the pace of bone loss and the sites of loss is different in men versus women [13]. Specifically, women tend to lose bone at a younger age and at a more rapid pace and more often have fractures at vertebral sites compared to men [14]. In addition, the skeletal integrity of male cortical bone is different, and the cross-sectional area appears to be greater among males; these differences, and changes in these parameters over time, seem to mediate the risk of osteoporotic fractures in men [15]. Given these facts, we cannot necessarily expect that what we know about osteoporosis from our studies of women will be directly applicable to men. This means that we need dedicated studies to understand how best to treat osteoporosis in men, but we have only limited data from such studies to inform our practice.
Damage analysis of human cortical bone under compressive and tensile loadings
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Ebrahim Maghami, Jason P. Moore, Timothy O. Josephson, Ahmad R. Najafi
Although there is a wide variety of research on bone fracture, there are limited in-depth studies on the influence of initial microdamage accumulation in bone on its fracture behavior. In this study, we would like to determine the impact of initial microcracking accumulation on the fracture trajectory of human microstructural cortical bone samples. Our goal is to create microdamage of varying severity to analyze how the presence of initial microcracks and how their quantity affect damage evolution and fracture trajectory. We also discuss the differences in the fracture response of cortical bone under compression and tension. We further identify to what extent that microcracking enables toughening and what role the morphology of cortical bone might play in determining the initiation sites of microcracks.
Concurrent consideration of cortical and cancellous bone within continuum bone remodelling
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Ina Schmidt, Areti Papastavrou, Paul Steinmann
This work aims to simulate bone density changes of cancellous and cortical bone as well as their interplay based on a continuum bone remodelling approach. Unlike spongy bone, the bone fibrils of cortical bone are densely packed, which is why this lamellar structure is also called compact bone. Remodelling of cortical bone can occur along the endosteal and periosteal surface as well as within the channels. The surface area per unit volume is considerably reduced compared to cancellous bone and therefore remodelling requires more time with less change in density. In order to adapt to the load case, the main mechanism considered here is the adjustment of the microstructural density. Whereas a change in bone geometry will not be considered, the simulation of bone adjustments in the endosteal area such as trabecularisation and thinning of the inner compact bone in old age is made possible.