Evaluation of the appropriate reaming diameter during initial fixation of a cementless hip prosthesis

　Background: Press-fit fixation is important technical factor to achieve initial stability of a cementless acetabular cup for good clinical results of total hip arthroplasty. However, appropriate reaming diameter during initial fixation is unclear. Therefore, this study aimed to evaluate the optimal reaming diameter using simulated bones and cementless cups.　Methods: Three types of simulated bones with different degrees of hardness were used (10 pcf, 20 pcf, 30 pcf, pcf = 16.02 kg/㎥). Acetabular models were created by reaming the simulated bone into a hemisphere, and the reaming diameters were 48 mm, 49 mm, and 50 mm.The 50 mm diameter acetabular cup was fixed to simulated bones with a compressive load of 16,000 N at a rate of 12 mm/min. The testing machine was attached to a cup fixed to the simulated bone, and a pull-out test, rotation test, and lever-out test were performed. To evaluate the initial gap, ink was applied to the cup surface during the pull-out test, and the contact between the bone and cup was visually evaluated after pull-out.　Results: The pull-out load of the 20 and 30 pcf simulated bones was significantly lower at a reaming diameter of 50 mm that those at reaming diameters of both 48 and 49 mm (P < 0.05). The rotational torque of the 20 and 30 pcf simulated bones was significantly lower at a reaming diameter of 50 mm that those at reaming diameters of both 48 mm and 49 mm (P < 0.05). The lever-out moment of the 20 and 30 pcf simulated bones was significantly lower at a reaming diameter of 50 mm than those at reaming diameters of both 48 mm and 49 mm (P < 0.05).Contact between the 30 pcf simulated bone and the cup at a reaming diameter of 48 mm was mainly at the edge of the cup; contact at the center of the cup was poor.　Conclusions: We performed mechanical tests using simulated bones and evaluated the initial fixation of the cup according to the bone reaming diameter. We recommend under-reaming by 1 mm in all cases to optimize both initial fixation capacity and contact between acetabular cup and bone

Evaluation of the appropriate reaming diameter during initial fixation of a cementless hip prosthesis

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Evidence that factors other than particular thyrotropin receptor T cell epitopes contribute to the development of hyperthyroidism in murine Graves' disease

Immunization with thyrotropin receptor (TSHR)-adenovirus is an effective approach for inducing thyroid stimulating antibodies and Graves’ hyperthyroidism in BALB/c mice. In contrast, mice of the same strain vaccinated with TSHR-DNA have low or absent TSHR antibodies and their T cells recognize restricted epitopes on the TSHR. In the present study, we tested the hypothesis that immunization with TSHR-adenovirus induces a wider, or different, spectrum of TSHR T cell epitopes in BALB/c mice. Because TSHR antibody levels rose progressively from one to three TSHR-adenovirus injections, we compared T cell responses from mice immunized once or three times. Mice in the latter group were subdivided into animals that developed hyperthyroidism and those that remained euthyroid. Unexpectedly, splenocytes from mice immunized once, as well as splenocytes from hyperthyroid and euthyroid mice (three injections), all produced interferon-γ in response to the same three synthetic peptides (amino acid residues 52–71, 67–86 and 157–176). These peptides were also the major epitopes recognized by TSHR-DNA plasmid vaccinated mice. We observed lesser responses to a wide range of additional peptides in mice injected three times with TSHR-adenovirus, but the pattern was more consistent with increased background ‘noise’ than with spreading from primary epitopes to dominant secondary epitopes. In conclusion, these data suggest that factors other than particular TSHR T cell epitopes (such as adenovirus-induced expression of conformationally intact TSHR protein), contribute to the generation of thyroid stimulating antibodies with consequent hyperthyroidism in TSHR-adenovirus immunized mice