| 摘要 |
A medical device comprising first and second ball sections, an intermediate section having a peripheral surface and opposite ends, and first and second generally cylindrical sections for coupling the first and second ball sections to the opposite ends of the intermediate section. The first and second generally cylindrical sections project from the intermediate section in generally opposite directions. Each of the first and second generally cylindrical sections has a smooth cylindrical surface, and the diameter of the first ball section is greater than the diameter of the second ball section. The diameter of each of the first and second ball sections is greater than the diameter of each of the first and second cylindrical sections.
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