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Simulation of Nonhomogeneous Bone
Published in Z. Yang, Finite Element Analysis for Biomedical Engineering Applications, 2019
The determination of the mechanical stresses in human bone is very important in both research and clinical practice because the understanding of the mechanical stresses in human bones benefits the design of prostheses and the evaluation of fracture risk. For example, after total hip replacement surgery, stresses in some regions of the remaining bone diminish because the implant carries a portion of the load, which is known as stress shielding. According to Wolff's law, the shielded bone remodels as a response to the changed mechanical environment, resulting in loss of bone mass through the resorption and consequent loosening of the prosthesis. To alleviate this problem, the stress distribution of the bone with the prosthesis should match that of the healthy bone as much as possible.
Biomaterials
Published in Manoj Ramachandran, Tom Nunn, Basic Orthopaedic Sciences, 2018
Subhamoy Chatterjee, John Stammers, Gordon Blunn
Bioresorbable implants reduce stress shielding, avoid the need for removal and enable postoperative imaging without metal artefact. The disadvantages are variable resorption rate, and therefore unpredictable mechanical properties, and iatrogenic non-specific foreign body reaction to the implant or degradation products. Newer bioresorbable polymers are under development to eliminate these disadvantages but there are no long-term clinical studies.
Musculoskeletal cases
Published in Lt Col Edward Sellon, David C Howlett, Nick Taylor, Radiology for Medical Finals, 2017
Stress shielding is reduction in bone density, osteopenia, as a result of the removal of normal stress on the bone owing to a prosthesis. If bone loading decreases, the bone becomes less dense and weaker as there is no longer a stimulus to normal bone remodelling. First there is osteopenia, with thinning of the cortex, and then bone resorption. This is usually seen medially, deep to the lesser trochanter (at the calcar), where it can cause limb shortening. Stress shielding and calcar resorption are normal findings on follow-up and are not associated with loosening of the prosthesis.How should this patient be managed? Surgical revision is almost always necessary.
Study and numerical analysis of Von Mises stress of a new tumor-type distal femoral prosthesis comprising a peek composite reinforced with carbon fibers: finite element analysis
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Stainless steel, medical titanium alloys (Ti6Al4V), and cobalt-chromium-molybdenum alloys (CoCrMo) have been widely used in the manufacture of orthopedic implant prostheses for some time (Guo et al. 2019a; Guo et al. 2019b). However, these metal materials have some shortcomings (Guo et al. 2020). For example, the elastic modulus of the metal material and the bone do not match. The elastic modulus of human bones ranges from 3 to 20 GPa, while those of medical titanium alloys and medical stainless steel reach as high as 110 and 200 GPa, respectively. After the insertion of metal implants, the phenomenon of stress shielding occurs, which accelerates bone loss and increases the risk of secondary fractures. In addition, metal-based materials are extremely dense, and thus, can lead to fractures or wear after implantation. Moreover, metal implants produce toxic metal wear particles during use, causing inflammation in the surrounding tissues. Compared with the wear particles of metal materials, the wear particles of polymer materials are less toxic. Notably, during radiological examinations and radiotherapy, metal prostheses produce metal artifacts and exhibit radiation scattering.
Analytical review on the biocompatibility of surface-treated Ti-alloys for joint replacement applications
Published in Expert Review of Medical Devices, 2022
Joint replacement is a surgical procedure in which an artificial joint surgically replaces arthritic or damaged joints made up of metals or plastic components. Damage to the joint may be caused due to several reasons such as aging, accident, or osteoarthritis. So, such damage causes orthopedic surgery that generally requires internal fixation of joints to provide stability during the bone healing process. Historically, cemented and cementless implant designs were used for total joint replacement (TJR) [1]. Cementless techniques are achieving more attention and popularity for TJR due to the removal of the second surgery requirement in cemented implants [2]. In cemented technique, initially, implants possess excellent mechanical strength, but later osteolysis causes loosening of implants. The biological response of cementless implants provides long-term mechanical stability. These implants’ stability depends on several parameters, such as corrosion behavior, debris created, and ions released from the implant. So, bone adaptation to implant and stress shielding is the central areas of concern [3].
Finite element study on the influence of pore size and structure on stress shielding effect of additive manufactured spinal cage
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Vijay Kumar Meena, Parveen Kalra, Ravindra Kumar Sinha
A considerable Young's modulus mismatch between the metal implant and the adjacent natural bone causes an irregular stress distribution at the bone-implant interface, resulting in a stress shielding effect (Alvarez and Nakajima 2009; Yan et al. 2015). Stress shielding increases the risk of fracture and implant loosening by causing bone tissue absorption around the metal implant (Huiskes et al. 1992). As a result, the ideal orthopedic implant material has Young's modulus that is similar to human bone tissue. The porous structures used in this study have this property similar to that of the natural human bone which is in the range of 0.5–20 GPa (Bonfield et al. 1998). Junchao et al. conducted a study on the compressive strength of titanium materials based on porosity and found that when porosity increases, the elasticity increases too (Junchao et al. 2016). The porous titanium alloy structures in this study can be identified with similar results that have the high elasticity to reduce the stress shielding effect.