| 摘要 |
A bone screw comprises a threaded portion. The threaded portion has a first thread including a first front surface (11), a first back surface (12) and a crest. A second thread including a second front surface (16) and a second back surface (17) is formed on at least part of the crest of the first thread. Because of the presence of the second thread, a contact area between the screw and a bone and an axial pullout force-bearing area are both significantly increased, without significantly influencing the bending resistance, so that the mechanical property of the screw is entirely improved.
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