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Adapting Injection Techniques to Special Indications
Published in Yates Yen-Yu Chao, Sebastian Cotofana, Anand V Chytra, Nicholas Moellhoff, Zeenit Sheikh, Adapting Dermal Fillers in Clinical Practice, 2022
Depressed scars are often corrected with hyaluronic acid (HA) fillers when an injection is the planned treatment (Figure 7.2). However, volume loss of scars and scarring fibrosis usually occur together. That could make filler correction of the volume deficits imprecise. HA fillers are gel-like substances. When gels are inserted into dense fibrotic tissue, they tend to be expelled out. The filler filled below or next to the scar could further deepen the contrast and aggravate the situation. Filler filled above the fibrotic aggregate could camouflage the contour defect but the tissue above it has to be thick enough (Figure 7.3a and b). Poly-L-lactic acid (PLLA) is a rather stable choice for correcting the scarring depression. Needle injection works similarly to the treatment of subcision and creates some specific spaces to accommodate PLLA substance. The increased volume several months after injection is continuous with self-tissue and the scar will not raise the concern of dislocation or deformity if the initial placement of PLLA is precisely in the scar tissue (see Section 4.7). Some permanent fillers such as polymethyl-methacrylate (PMMA) have been approved by the Food and Drug Administration (FDA) for the correction of acne scars; however, permanent fillers bring permanent worries about contamination when further injections and wounding procedures are to be performed there.
Using Fillers in the Abdomen and Buttocks
Published in Neil S. Sadick, Illustrated Manual of Injectable Fillers, 2020
Rosemarie Mazzuco, Taciana Dal’Forno Dini
Polymethyl methacrylate (PMMA) is a permanent filling material that can provide immediate and long-term results. As indicated by its classification, this product will persist indefinitely in the tissue, a characteristic that may raise concerns about its safety and potential long-term side effects. The product is commercially available in Brazil in concentrations of 2, 5, 10, 15, and 30% (25). It is especially used in patients with HIV-associated gluteal lipoatrophy (26). Nevertheless, the risk of complications such as pulmonary embolism, infection, and late granulomas has resulted in a significant decrease in its use for body indications.
Principles of Joint Prostheses
Published in Verna Wright, Eric L. Radin, Mechanics of Human Joints, 2020
Charnley’s prosthesis was anchored to the bone by polymethyl methacrylate bone cement. In the 1970s, after large numbers of joint replacement operations had been done, a significant number of patients experienced pain associated with loosening of the components from the skeleton (59–65). Histological study of tissue at the interface between the cement and bone showed sheets of macrophages in a fibrous stroma with evidence of active bone resorption (14). Macrophages had inclusions in the cytoplasm, many of which proved to be methyl methacrylate particles. The deduction was made that the cement was responsible for the loosening process (37,56), and many investigators began to implant prostheses without bone cement.
Novel Histopathologic and Immunohistochemical Observations in Explanted Orbital Peri-implant Capsules
Published in Current Eye Research, 2021
Tarjani Vivek Dave, Dilip Kumar Mishra, Vivek Singh, Sonali Kumar, Noopur Mitragotri, B Sridhar Rao
Evisceration involves removal of the eye contents with preservation of the sclera, optic nerve, and the extra-ocular muscles. Following evisceration either primarily or as a secondary procedure, an orbital implant is placed to maintain the orbital volume.1–2,3 A commonly used implant is the one made of polymethyl methacrylate. The formation of a peri-implant capsule has been reported with glaucoma valve implants placed in the eye and also with implants placed elsewhere in the body for volume augmentation such as the silicone breast implants.4–7 Whenever an implant is placed, the body reacts by forming a protective lining around it. This protective lining is the peri-implant capsule. Capsule formation is heralded by a characteristic cellular reaction to the implants, also known as the foreign body response.8 This response is initiated at the time of implant placement with spontaneous absorption of host proteins, cellular debris, and platelets on the implant surface. Platelet-derived factors stimulate neutrophil and macrophage infiltration. The macrophages attract fibroblasts and myofibroblasts which in turn produce excessive collagen around the implant. Finally, a formed capsule of collagen surrounds the implant and walls it off structurally and functionally from the host tissues.8
Tibial implant fixation in TKA worth a revision?—how to avoid stress-shielding even for stiff metallic implants
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
B. Eidel, A. Gote, C.-P. Fritzen, A. Ohrndorf, H.-J. Christ
For the material behavior of tibial bone, an isotropic linear elasticity law is assumed to hold. The assumption of linear elasticity is corroborated by recent experimental findings by Juszczyk et al. (2011) and Grassi et al. (2016) (for femoral bone), the validity of isotropic elasticity in simulations is underpinned by Schileo et al. (2014). Cowin presents orthotropic elasticity parameters for the tibia, which are, however, throughout constant and thus do not account for the pronounced non-homogeneity of real bone (Cowin 2009). The figures of the strongly heterogeneous Young’s modulus distribution follow from bone reconstruction as described in Section 2.1. The Poisson’s ratio is assumed to be constant, 1998) as well as for the cobalt-chrome alloy (CoCr) version. The very standard of bone cement is polymethyl methacrylate (PMMA). Polyethylene (PE) is used for the tibial tray; moreover, we consider for its low stiffness a fictitious implant fully made of PE (all-PE). The material parameters of linear elasticity are listed in Table 1.
Release behavior, mechanical properties, and antibacterial activity of ciprofloxacin-loaded acrylic bone cement: a mechanistic study
Published in Drug Development and Industrial Pharmacy, 2020
Marzieh Gandomkarzadeh, Arash Mahboubi, Hamid Reza Moghimi
Nowadays the use of ultraclean air theaters, perioperative antibiotics and antibiotic-loaded bone cement (ALBC) leads to a significant reduction in risk of infections [4]. Addition of antibiotics in poly(methyl methacrylate) (PMMA) bone cements is appropriate to treat and prevent orthopedics infections, for decades. In fact, acrylic bone cement, in addition to its role as a biomaterial used in total hip and knee arthroplasty surgeries, could act as a drug carrier to decrease the rate of infections at the site of action. The United States Food and Drug Administration (FDA) has approved ALBC products for second-stage of two-stage total joint replacement surgery due to infection. This drug delivery system is an alternative for systemic drug delivery systems with low efficacy in bone infections. The antibiotic impregnated bone cement provides higher concentration of drug at the infection site and effectively inhibits infections with much less side effects in comparison to systemic administration [5–7]. Novel antimicrobial agents like silver and gold nanoparticles have also been developed for the improvement of bone cement antibacterial features against resistant strains [8–10]. PMMA bone cement, are also designed as beads or spacers for treatment of musculoskeletal infections in the revision surgery [11].