Journal of orthopaedic research : official publication of the Orthopaedic Research Society
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The variation in the dimensions of the lumbar spinal canal under both flexion-extension and axial compression-distraction was studied using computerized tomography (CT) scans in human cadaver lumbar spine specimens. In 3-mm-thick CT slices through the disk at L3-L4, the cross-sectional area of the spinal canal was reduced by around 40 mm2, corresponding to a 16% reduction of the initial area when the lumbar spines were moved both from flexion to extension and from distraction to compression. ⋯ During these motions, the ligamentum flavum did not appear to be a significant factor for the dynamic changes affecting the dimensions of the canal. This held true even after the disk had been excised in order to produce a total collapse of the disk space.
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For osteochondral allograft transplantation to be successful, chondrocytes must survive preservation and retain their capacity to produce normal matrix components: proteoglycans and Type II collagen. Clinical success with osteochondral allograft transplantation has created an increased demand for supplies of suitable cartilage-bearing grafts. This demand has stimulated attempts to find successful methods for low temperature storage of cartilage for "banking" and heightened interest in cartilage cryobiology. ⋯ In all groups, typical chondroid characteristics were maintained throughout 14 days of culture. Typical cartilage phenotypic characteristics included maintenance of polygonal and rhomboidal cells, cell aggregation, proteoglycan production, and Type II collagen synthesis. This investigation strongly indicates that articular chondrocyte cryopreservation yields viable, functional cells and although these results cannot be directly extrapolated to intact adult articular cartilage, they do give further support for low temperature banking of cartilage-bearing allografts for transplantation.
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A general theory for the role of intermittently imposed stresses in the differentiation of mesenchymal tissue is presented and then applied to the process of fracture healing. Two-dimensional finite element models of a healing osteotomy in a long bone were generated and the stress distributions were calculated throughout the early callus tissue under various loading conditions. These calculations were used in formulating theoretical predictions of tissue differentiation that were consistent with the biochemical and morphological observations of previous investigators. The results suggest that intermittent hydrostatic (dilatational) stresses may play an important role in influencing revascularization and tissue differentiation and determining the morphological patterns of initial fracture healing.
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An experimental biodegradable bone cement [poly(propylene fumarate)-methylmethacrylate] (PPF-MMA) has been compared in vivo with polymethylmethacrylate (PMMA) as a carrier agent for local release of antibiotics. This approach is potentially applicable to the treatment of chronic osteomyelitis where the clinical goal is to achieve sustained high concentrations of antibiotics locally in the infected bone. In our experiments, gentamicin- and vancomycin-impregnated cylindrical PMMA and PPF-MMA cement specimens were implanted subcutaneously in rats, and blood and wound fluid samples were obtained over a 2-week period. ⋯ Mechanical testing of the PPF-MMA cement showed that admixture of 3% by weight of antibiotic did not adversely affect material properties. We conclude that this experimental biodegradable bone cement (PPF-MMA) can be used as a carrier to achieve high sustained local levels and low serum levels of antibiotics. Because it is biodegradable and thus does not require a secondary procedure for removal, it has special potential for use in treatment of chronic osteomyelitis.
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In the treatment of spine fractures and fracture-dislocations, stability of the spine is one of the major objectives. In the craniocervical joint, the alar and transverse ligaments provide much of the stability of the healthy spine. Because the anatomy appears well described, the contribution of each of these structures so far has received little attention. ⋯ Histologic analysis revealed a mainly collagenous nature of these ligaments. Clinical evidence (broken odontoid processes) suggests that the transverse ligament is strong enough to withstand physiologic loads. The alar ligament, on the other hand, due to its lower strength and its axial direction of loading, might be prone to injury and therefore require stabilization of the appropriate vertebra more often than normally is assumed.