Trabecular bone composition

Somervaille JL, Chettle DR, Scott, MC, et al. 1987. X-ray fluorescence of lead in vivo Simultaneous measurement of a cortical and a trabecular bone in a pilot study. In Ellis, Yasumuru, Morgan, eds. In vivo bodv composition studies. New York, NY Brookhaven National Laboratory, The Institute of Physical Sciences in Medicine. 

Use of 3D foams is also a popular method for bone regeneration applications, although they are most often employed for trabecular bone regeneration [152,154]. There are a few methods utilized to create foams for this application, one of the most popular being a polymer foam replication technique, in which a polymer foam is either electrosprayed or immersed into a HAp/bioactive glass particle slurry in order to fully coat the foam and create a trabecular bone-like aichitecture. However, other methods are also utilized, including creating composite foam solutions that are injectable and form once inside the body [153]. Results of Fu et al. [152] have indicated mechanical properties similar to those of natural trabecular bone. 

In contrast to trabecular bone, in the cortical bone of ovx monkeys the mineral content was significantly increased in endosteal regions, while the crystallinity and collagen crosslink ratio remained constant in both periosteal and endosteal tissue [66]. Because these parameters displayed different trends in cortical and trabecular bone, the compositional adaptations may be site-specific. 

The anabolic agents parathyroid hormone (PTH) [66, 71] and nandrolone dec-anoate (ND) [72, 73] have both been shown to stimulate bone formation. PTH caused bone to exhibit compositional characteristics typically associated with younger bone, including a lower mineral matrix ratio, crystallinity and crosslink ratio. In contrast, ND treatment restored those parameters affected by ovariectomy to the level of sham controls in cortical bone, but not in trabecular bone. 

Trabecular bone is formed through a different arrangement of lamellae. An individual trabeculum is a tube of wrapped lamellae on the order of 150 to 300 pm in diameter. Trabeculae can also form in the shape of plates, which have a slightly larger dimension but are again composed of parallel layers of the collagen-mineral composite. The trabecular plates, beams, and struts are arranged into... 

In an in vivo study that lasted 5-7 years, Hasegawa et al. [16] investigated the biocompatibility and biodegradation of HA/PLLA composite bone rods using non-calcined HA (n-HA) and calcined HA (c-HA) that were implanted into the distal femurs of 25 rabbits. The n-H A/PLLA composites showed excellent biodegradabUity and osteoconductivity. Newly formed bone surrounded the residual material and trabecular bone, bonded to the rod, was observed toward the center of the implant. 

Yaszemski, M.J., Mikos, A.G., Payne, R.G. and Hayes, W.C. (1994) Biodegradable Polymer Composites for Temporary Replacement of Trabecular Bone The Effect of Polymer Molecular Weight on Composite Strength and Modulus, In Biomatetials for Drug and Cell Delivery, Mikos. A.G., Murphy R., Bernstein H., Peppas N..V., eds., 331, Pittsburgh Materials Research Society) 251-256. 

Opencell composite foams comprising PLA and ceramic fillers, HAp or P-TCP were obtained by Mathieu and coworkers using supercritical CO2 [148]. All the foaming conditions tested led to foams with structural parameters in the range of those of cancellous bone. This similarity is shown in Fig. 15, which compares three polymer foams and three different types of trabecular bones. 

The foamlike scaffold has a similar microstructure as trabecular bone, with nanometer-sized and micron-sized pores. The apatitic phase of the scaffold also exhibited similar chemical composition, crystalline phase, and grain size, thus exhibiting excellent bioactivity for promoting cell attachment and proliferation. These bionanocomposites were osteoconductive in that they successfully healed a nonunion fracture in rat femur, as well as a critical-sized defect in pig tibia, therefore showing their potential in bone reconstitution. 

Gong JK, Arnold JS, Cohn SH. 1964. Composition of trabecular and cortical bone. AnatRec 149 325-331. 

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