| 摘要 |
A bone plate ( 15 ) is provided with a keyhole shaped aperture ( 10 ) having a first wide portion ( 20 ) leading into a second narrow portion ( 22 ) by way of a discontinuous narrowing ( 24 ). The narrow portion ( 22 ) has a concave recess ( 26 ) in the upper surface ( 11 ) of the plate and a bevel ( 28 ) in the bone contacting surface ( 13 ) at its end remote from the wide portion. In use, a screw ( 30 ) can be inserted obliquely across a fracture ( 40 ) and does not need to be countersunk in the bone, nor removed and replaced to allow fitting of the plate ( 15 ). The wide portion ( 20 ) of the hole ( 10 ) passes over the head ( 32 ) of the screw ( 30 ), the plate is then slid (arrow a) so that the head ( 34 ) lies in the narrow portion ( 22 ). Once the screw is fully tightened its head sits in the concave recess ( 26 ) and because of the narrowing ( 24 ), it prevents the plate sliding back. The screw shank ( 34 ) adjacent the head is accommodated in the bevel ( 28 ). Further bone screws can then be secured via other apertures ( 12, 14, 16, 18 ) in the plate ( 15 ).
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