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Applications of Biomaterials in Hard Tissue Replacement
Published in Yaser Dahman, Biomaterials Science and Technology, 2019
Bones in the body are found in two basic forms, long bones and plates. Long bones are hollow inside. The inner space is called the medullary cavity; two membranes surround the outside of the bone, which is the periosteum. The inside of the bone lining the medullary cavity is the endosteum.
Osseointegrated prostheses for the rehabilitation of amputees (OPRA): results and clinical perspective
Published in Expert Review of Medical Devices, 2020
Benjamin W. Hoyt, Sarah A. Walsh, Jonathan A. Forsberg
The Osseointegrated Prostheses for the Rehabilitation of Amputees uses osseointegration, or ingrowth directly into bone, to achieve rigid fixation to the endosteum of residual bone in an amputation. The device is comprised of three components: the fixator, the abutment, and the abutment screw (Figure 2). Ingrowth of the device is achieved through the cylindrical threaded fixture component that is screwed longitudinally into the prepared canal of the bone. The threaded fixture offers improved initial fixation compared to press-fit designs, limiting micromotion and risk of ingrowth failure during early load bearing. However, it does contribute to greater stress-shielding effects and theoretical risk of late periprosthetic fracture [14]. To further enhance initial fixation and ingrowth, the surface of the medical grade titanium stem incorporates a fluted design and is treated with laser-induced nanopore modification called BioHelix™, which demonstrates considerable increases in resistance to torque after healing compared to untreated fixtures [15,16]. After osseointegration has been achieved, typically a period of 3 months, an abutment is press-fit to the ingrowth fixture and an abutment screw is used to lock this in place. The abutment is the transcutaneous component and acts as the interface with prosthetic options, transferring loads from the prosthetic to the fixture and bone. This abutment is designed to break when exposed to extreme loads in order to protect the bone and fixture from fracture or unbonding, and the interface with the prosthetic is designed to release at excessive loads to protect the entire system from breakage [9]. Other features specific to the OPRA abutment include a polished abutment surface to decrease skin irritation at the dermal interface.
Finite element analysis of bone mechanical properties using MRI-derived bound and pore water concentration maps
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Thammathida Ketsiri, Sasidhar Uppuganti, Kevin D. Harkins, Daniel F. Gochberg, Jeffry S. Nyman, Mark D. Does
The contribution of pore water concentration to E and Y was low despite the range in Cpw being greater in the present set of cadaveric radii than in our previous study (Manhard et al. 2016). There are several possible explanations for this weak contribution of Cpw to the material properties of cortical bone. Firstly, our previous study in which both Cpw and Cbw significantly contributed to the prediction of bending strength of the radial diaphysis did not use FEA to account for role of bone structure in strength. By accounting for size and shape of each bone in the FE simulations, the importance of Cpw was perhaps diminished. Secondly, although cortical porosity is a known determinant of bone strength (Currey 1990; McCalden et al. 1993; Wachter et al. 2002), its negative correlation with yield stress has been shown to be rather weak (e.g. R2 = 0.22, p = 0.004) (Mirzaali et al. 2016). Lastly, higher pore water concentration (higher cortical porosity) does not necessarily translate to weaker bone if the Cpw is dictated by signal from the endosteum. Bone loss in the diaphysis of long bones occurs near the endosteum causing a ‘transition’ zone in which cortical bone appears to be trabecular bone (Zebaze et al. 2010). Loading cadaveric radii in four-point bending to failure and imaging the micro-structure of the diaphysis by high-resolution μCT, Bigelow et al. observed a stronger correlation between pores distributed away from the neutral axis and bending strength than between overall porosity and bending strength (Bigelow et al. 2019). Since the imaging resolution of this study is 1 mm, high Cpw values could also be influenced by bone marrow signal in the endosteum region, especially for bones with a thin cortical shell. The literature values of mean cortical thickness of radius bones (2.51 0.58 mm (Louis et al. 1995) and 5.75 1.07 mm (Webber et al. 2015) also shown that cortical thickness for some bone samples could be relatively close to the imaging resolution. This effect would be smaller in Cbw measurements since bone marrow signals are suppressed in the AIR pulse sequence.
Fluoride and human health: Systematic appraisal of sources, exposures, metabolism, and toxicity
Published in Critical Reviews in Environmental Science and Technology, 2020
Humayun Kabir, Ashok Kumar Gupta, Subhasish Tripathy
Fluoride is an avid seeker of calcified tissue, and almost 99% of the body F− is bound to mineralized tissue such as the teeth and bone (Whitford, 1994b). Fluoride strongly, but reversibly, binds to apatite and other calcium phosphate compounds present in calcified tissue (O’Mullane et al., 2016; Waterhouse, Taves, & Munzer, 1980). The F− ions, present in the extracellular fluid, diffuse into hydration cells and form mixed fluorohydroxyapatite by replacing the OH− group present in the bone crystal. This process is rapid and reversible (Florkin & Stotz, 1970; Ranjan & Ranjan, 2015). In the next stage, the F− accumulates in the deeper and denser part of the calcified tissue through a slow and irreversible process. The steady state relationship between extracellular fluid and hydration sites of bone makes it a terminal biomarker (Hodge & Smith, 1970). The deposition rate, both at the surface and deeper, is maximal during the growth phase as small crystallites, and higher hydration facilitates diffusion of F− (Hodge & Smith, 1970; Kanduti et al., 2016; Martínez-Mier, 2012; Ullah, Zafar, & Shahani, 2017). The distribution of F− in bone is not uniform. It is higher in cancellous and lower in compact bone. In addition, in the cortical bone, a higher level of F− has been observed in the periosteum and endosteum regions. A lower level has been observed in the haversian and interstitial lamellae (Narita et al., 1990; Riedel et al., 2017; Weidmann & Weatherell, 1959). Uptake of F− by bone is an age-dependent phenomenon. Approximately 36% of absorbed F− accumulates in the bone in healthy adults, whereas this value can reach 55% in children below the age of seven (Whitford, 1994b). According to the F− concentration, Swarup and Dwivedi (2002) have classified animal bone in five classes: normal (300–400 ppm), innocuous (˂4500 ppm), marginal osteofluorosis (4500–5500 ppm), toxicosis (˂7000 ppm), and saturated (15,000–20,000 ppm). Fish grown in F− contaminated water exhibit bone F− concentrations up to 1000 mg kg−1 of dry calcified tissue (Pinskwar, Jezierska-Madziar, & Golski, 2003). Acute F− toxicity results in saturation followed by the flooding of soft tissue, which may instigate metabolic failure and lead to dysfunction of the animal skeletal system (Underwood & Suttle, 1999). Fluoride present in bone may be removed by an anion exchange process in hydration cells and through osteoclastic respiration of bone. The former process is rapid and may take several weeks, whereas the latter process is prolonged, with average half-life periods of 8 years (Underwood & Suttle, 1999; WHO, 1984).