Toshihide Nakashima

Augmentation of cancellous screw fixation with hydroxyapatite composite resin (CAP) in vivo

The fixation of fractured bone with screws is important for orthopedic surgery, however, rigid fixation often cannot be attained in elderly patients with osteoporosis. Recently, we developed a new injectable, nonresorbable bone cement (CAP) that possesses mechanical and biological properties superior to those of polymethylmethacrylate (PMMA) cement. CAP can directly bond with bone without intervening fibrous tissue, and the peak curing temperature is 46 degrees C. In this study, we assessed the effects of CAP and PMMA cement on the augmentation of screw fixation in vivo. A cancellous screw was placed in the proximal metaphysis of rabbit tibiae. One side of each tibia was randomly selected to be augmented with CAP or PMMA. The contralateral side received a screw without cement (control). Of the 36 rabbits included in this study, 9 rabbits from each group were sacrificed and the tibial constructs retrieved 1 or 3 months after the initial operation. The screws were then pulled out to failure. The values of the pullout force of the screws augmented with CAP and PMMA were higher than those of the control specimens at both 1 month (319 +/- 58 N for CAP vs. 105 +/- 41 N for control; p < 0.05, 284 +/- 100 N for PMMA vs. 132 +/- 71 N for control; p < 0.05) and 3 months (387 +/- 109 N for CAP vs. 196 +/- 107 N for control; p < 0.05, 372 +/- 145 N for PMMA vs. 242 +/- 100 N for control; p > 0.05) after the operation. However, the average increase in the pullout force between CAP and PMMA augmentation was not statistically significant at either time. The values of energy absorption augmented with CAP and PMMA were also higher than those of the control specimens at both 1 month (129 +/- 54 N*mm for CAP vs. 19 +/- 10 N*mm for control; p < 0.05, 145 +/- 95 N*mm for PMMA vs. 28 +/- 21 N*mm for control; p < 0.05) and 3 months (172 +/- 58 N*mm for CAP vs. 44 +/- 41N*mm for control; p < 0.05, 185 +/- 198 N*mm for PMMA vs. 67 +/- 49N*mm for control; p > 0.05) after the operation. However, there were also no significant differences in energy absorption between the two types of cement augmentation. On the other hand, a significant increase was not observed in stiffness among the CAP, PMMA, and respective control groups at either 1 month (626 +/- 133 N/mm for CAP vs. 441 +/- 180 N/mm for control; p < 0.05, 577 +/- 87 N/mm for PMMA vs. 450 +/- 121 N/mm for control; p > 0.05) or 3 months (622 +/- 144 N/mm for CAP vs. 600 +/- 204 N/mm for control; p > 0.05, 633 +/- 175 N/mm for PMMA vs. 630 +/- 168 N/mm for control; p > 0.05) after the operation, except in the average increase between CAP augmentation and its control 1 month after the operation. These results suggested that a cancellous screw fixation augmented with CAP, as well as PMMA, was effective compared with the unaugmented control in vivo. Because of its biocompatibility and low curing temperature, CAP can be used clinically to augment cancellous screw fixation.

Adsorption of glycated proteins by boronic copolymer-coated adsorbents

The presence of glycated proteins in the plasma of diabetic patients may play a role in serious complications such as nephritis, retinosis, and nerve disorders. We evaluated the adsorption properties of copolymers of styreneboronic acid and styrenesulfonic acid for glycated protein and glycated lipoprotein. Porous glass with pore sizes of 50 and 100nm and cellulose gel were coated with or bound to the copolymer of styreneboronic acid, styrenesulfonic acid, and glycidyl methacrylate. These adsorbents showed selective adsorptivity for glycated albumin and glycated lipoprotein, depending on their boronic acid content. Copolymer composition affects the adsorption properties in a different manner for glycated albumin and glycated lipoprotein, suggesting that not only boronic acid but also sulfonic acid moieties play an important role in adsorption. The copolymer of styreneboronic acid and hydroxyethyl methacrylate had a smaller adsorption capacity than the copolymer of styreneboronic acid and styrenesulfonic acid without positive participation of the hydroxyethyl methacrylate moiety, which also showed the need for sulfonic acid in selective adsorption. Furthermore, these adsorbents had less capacity to activate the intrinsic blood coagulation cascade. Therefore, it may be possible to use these adsorbents to prevent the complications of diabetes by plasmapheresis.The presence of glycated proteins in the plasma of diabetic patients may play a role in serious complications such as nephritis, retinosis, and nerve disorders. We evaluated the adsorption properties of copolymers of styreneboronic acid and styrenesulfonic acid for glycated protein and glycated lipoprotein. Porous glass with pore sizes of 50 and 100nm and cellulose gel were coated with or bound to the copolymer of styreneboronic acid, styrenesulfonic acid, and glycidyl methacrylate. These adsorbents showed selective adsorptivity for glycated albumin and glycated lipoprotein, depending on their boronic acid content. Copolymer composition affects the adsorption properties in a different manner for glycated albumin and glycated lipoprotein, suggesting that not only boronic acid but also sulfonic acid moieties play an important role in adsorption. The copolymer of styreneboronic acid and hydroxyethyl methacrylate had a smaller adsorption capacity than the copolymer of styreneboronic acid and styrenesulfonic acid without positive participation of the hydroxyethyl methacrylate moiety, which also showed the need for sulfonic acid in selective adsorption. Furthermore, these adsorbents had less capacity to activate the intrinsic blood coagulation cascade. Therefore, it may be possible to use these adsorbents to prevent the complications of diabetes by plasmapheresis.