PubMed · 6857069
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F Bornand. 1983. [Hip prosthesis without cement].. https://pubmed.ncbi.nlm.nih.gov/6857069/
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Most of the research performed on calcium phosphate bone cements (CPBCs) has dealt with the improvement of bone cement formulations for new, demanding bone-filling applications. In particular, the development of injectable bone cements is of real interest for the biomedical community. The aim of this work was to study the effect of citric acid on the injectability and the setting properties of alpha-tricalcium phosphate-based cements. A comparative kinetic study was performed on cements with and without citric acid relating the hardening curves and the hydration rates using a mathematical approach. Citric acid behaved as a fluidificant during the first stages of the cement mixing. The dissolution-precipitation reactions of the alpha-tricalcium phosphate were retarded with the addition of citric acid and the compressive strength at saturation increased. In conclusion, citric acid can behave as a water-reducing admixture.
The long-term survival of cemented hip replacements depends on the ability of the cemented fixation to resist fatigue damage. Damage has been assumed to accumulate linearly (Miner's law) even though it is unlikely to be the case in such a porous brittle material. This study addresses the nonlinear stress-dependent nature of fatigue damage accumulation in acrylic bone cement. Specimens were subjected to a zero-to-tension fatigue load in water at 37 degrees C. A total of 15 specimens were tested, i.e., five specimens at each of three stress levels. The specimens were cyclically loaded to a certain fraction of their fatigue lives and the amount of microcracking present at that time was quantified by counting each crack and measuring its length. This procedure was repeated until the specimen failed. A total of 801 cracks formed in the 15 specimens. All cracks were found to initiate at pores. Crack propagation directions were distributed normally about the direction perpendicular to the applied load at the lower stress levels, but at higher stress, the distribution tended to be broader. At higher stresses, more cracks were produced per pore. The damage accumulation process in acrylic bone cement was found to be nonlinear with the degree of nonlinearity increasing with stress. Furthermore, great variability was found which was attributed to the differences in porosity between specimens. A power law equation is given which describes the predicted relationship between damage accumulation and number of loading cycles as a function of the stress level.
STUDY DESIGN: A human cadaveric investigation was conducted to determine the effect that a side-opening injection cannula in monopedicular percutaneous vertebroplasty had on the vertebrae filling pattern. OBJECTIVES: To assess the filling pattern in vertebroplasty using a monopedicular technique, and to compare a standard front-opening filling cannula with a side-opening cannula. SUMMARY OF BACKGROUND DATA: Vertebroplasty is an effective treatment for osteoporotic vertebral fractures. Clinical and biomechanical investigations show its efficacy even in asymmetrical filling patterns. However, the risk of cement extravasation is a major concern with this technique. METHODS: Two different bone cement-injecting cannulas were compared: a standard front-opening cannula (8 gauge, 6 inches long) and a cannula of the same dimensions with a side-opening at its distal end. Eight pairs of osteoporotic nonfractured cadaver vertebrae (T10-T11) were augmented with low-viscosity polymethylmethacrylate under axial C-arm control. The filling pattern was assessed semiquantitatively. The cross-section in its lateral extension was divided into four equal bands, and the appearance of the cement in each respective zone was assessed after cement injections of 2, 4, and 8 mL. The extravasation of bone cement also was monitored. RESULTS: With the side-opening cannula, the cement flow reached Zone 3 in six of eight cases, whereas with the front-opening cannula, the polymethylmethacrylate was observed in Zone 3 in only three cases. In no case was the cement observed in Zone 4. In five of eight cases using front-opening cannulas, extravasation into the vessels was observed after 3 to 4 mL of bone cement had been injected. No extravasation was noted with the use of the side-opening cannula unless the amount of cement exceeded 8 mL. CONCLUSIONS: A side-opening cannula can improve the cement-filling pattern in monopedicular vertebroplasty, as compared with a standard front-opening cannula. The risk of extravasation is diminished if the cement flow is directed medially.