Screw made of biodegradable material for bone surgery purposes, and screwdriver suitable therefor

In a screw made of biodegradable material for bone surgery purposes, the outer surface of the screw body is provided with a coaxial external thread. A coaxial channel of sawtoothed star-shaped transverse cross-sectional profile is provided in the screw body, which channel is open at the proximal end in order to receive the complementarily shaped shaft of a screwdriver, and extends into the area of the distal end. The channel wall is radially symmetrical about the longitudinal axis in regular rotary steps and defines an axial channel area and a plurality of lobe areas arranged uniformly around the channel area. In each lobe area the channel wall has a pair of flanks which extend into the vicinity of an end of the lobe area remote from the channel area. In a cross-section of the screw body, each lobe area is formed asymmetrical in respect of a diametrical plane. A section of the contour line which corresponds to the leading flank is shorter than a section of the contour line which corresponds to the trailing flank. The leading flank may have a form which leads to an increasing extent as the radial distance increases in the direction of screwing-in. At the end of the lobe area the flanks can run together to form an edge and define 3 to 8, preferably 6, sickle-shaped teeth which are salient with respect to the direction of rotation.

Abstract

In a screw made of biodegradable material for bone surgery purposes, the outer surface of the screw body is provided with a coaxial external thread. A coaxial channel of sawtoothed star-shaped transverse cross-sectional profile is provided in the screw body, which channel is open at the proximal end in order to receive the complementarily shaped shaft of a screwdriver, and extends into the area of the distal end. The channel wall is radially symmetrical about the longitudinal axis in regular rotary steps and defines an axial channel area and a plurality of lobe areas arranged uniformly around the channel area. In each lobe area the channel wall has a pair of flanks which extend into the vicinity of an end of the lobe area remote from the channel area. In a cross-section of the screw body, each lobe area is formed asymmetrical in respect of a diametrical plane. A section of the contour line which corresponds to the leading flank is shorter than a section of the contour line which corresponds to the trailing flank. The leading flank may have a form which leads to an increasing extent as the radial distance increases in the direction of screwing-in. At the end of the lobe area the flanks can run together to form an edge and define 3 to 8, preferably 6, sickle-shaped teeth which are salient with respect to the direction of rotation.

1. Drawings

[0001]Sheet 1.

[0002]Sheet 2.

[0003]Sheet 3.

[0004]Sheet 4.

[0005]Sheet 5.

[0006]Sheet 6.

[0007]Sheet 7.

[0008]Sheet 8.

[0009]Sheet 9.

[0010]Sheet 10.