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

Claim 2

A screw made of biodegradable material for bone surgery purposes, comprising: an elongate screw body which extends, in the direction of a longitudinal axis thereof, between a proximal and a distal end thereof; an outer surface of the screw body being provided with an external thread coaxial with respect to the longitudinal axis, which external thread is configured for guiding and holding the screw on bone material of a patient and defines a direction of rotation about the longitudinal axis for the screwing-in of the screw body and the advancing of the distal end into the bone material; an elongate channel coaxial with respect to the longitudinal axis and provided in the screw body, which channel is open at the proximal end for receiving a shaft of a screwdriver for turning the screw; the channel having a channel wall, the shape of which is radially symmetrical about the longitudinal axis in discrete, regular rotary steps and provides, in a cross-section of the screw body at right angles to the longitudinal axis, a trace line which is a closed contour line radially symmetrical about a trace line of the longitudinal axis in discrete, regular rotary steps; the channel wall defining an axial channel area and a plurality of lobe areas arranged uniformly about the channel area, so that the channel consists essentially of the combination of the axial channel area and the lobe areas; in each lobe area, the channel wall having a pair of flanks which extend essentially from the channel area to the vicinity of an end of the lobe area remote from the channel area, and which, with reference to the said direction of rotation, define in each case a leading flank and a trailing flank; the channel extending into the area of the distal end of the screw, and in a cross-section of the screw body at right angles to the longitudinal axis, each lobe area being formed asymmetrically in the respect of a diametrical plane passing through the longitudinal axis, a section of the contour line which corresponds to the leading flank being shorter than a section of the contour line which corresponds to the trailing flank, so that the lobe area has a sawtooth-like profile of a radial distance of the contour line from the longitudinal axis, when considered along the contour line with, on the average, a steeper raise of the leading flank and a flatter fall of the trailing flank.

Claim 3

The screw according to claim 1, wherein: in each lobe area, at least one of the said flanks has, at least in the vicinity of the said remote end of the lobe area, a form which leads to an increasing extent in the said direction of rotation as the radial distance from the longitudinal axis increases.

Claim 4

The screw according to claim 1, wherein: the flanks are twisted helically about the longitudinal axis with respect to said direction of rotation, in such a way that, in two cross-sections of the screw body which are different from one another and at right angles to the longitudinal axis, the contour lines represent congruent images of one another which can be made congruent by simple turning about the trace line of the longitudinal axis.

Claim 5

The screw according to claim 1, wherein: the flanks are tapered in the direction from the proximal end to the distal end in such a way that, in two cross-sections of the screw body which are different from one another and at right angles to the longitudinal axis, the contour lines represent images of one another which can be made congruent by homothetic transformation about the trace line of the longitudinal axis.

Claim 6

The screw according to claim 4, wherein: the flanks are both twisted and tapered in such a way that, in two cross-sections of the screw body which are different from one another and at right angles to the longitudinal axis, the contour lines represent images of one another which can be made congruent by a combination of simple turning and homothetic transformation about the trace line of the longitudinal axis.

Claim 7

The screw according to claim 4, wherein: the tapering of the flanks in the direction from the proximal end to the distal end corresponds to a semi-aperture angle of up to 10°.

Claim 8

The screw according to claim 2, wherein: in each lobe area, the two flanks extend at a distance from one another which tapers towards the remote end of the lobe area as the radial distance from the longitudinal axis increases.

Claim 9

The screw according to claim 7, wherein: the two flanks run together at the remote end of the lobe area to form an edge.

Claim 10

The screw according to claim 2, wherein: in each lobe area, the trailing flank is curved convexly counter to the said direction of rotation, at least in the vicinity of said remote end of the lobe area.

Claim 11

The screw according to claim 1, wherein: in each lobe area, the leading flank is curved convexly with respect to the said direction of rotation, or the leading flank is essentially located in a plane passing through the longitudinal axis.

Claim 12

The screw according to claim 2, wherein: in each lobe area, the leading flank is curved concavely with respect to the said direction of rotation, at least in the vicinity of said remote end of the lobe area.

Claim 13

The screw according to claim 2, wherein: in a cross-section of the screw body at right angles to the longitudinal axis, the contour line corresponds essentially to a star-shaped continuous line which is radially symmetrical about the trace line of the longitudinal axis, with 3 to 8 lobes salient with respect to said direction of rotation.

Claim 14

The screw according to claim 12, wherein: the lobes are approximately sickle-shaped.

Claim 15

The screw according to claim 2, wherein: in each lobe area, the two flanks extend at an approximately constant distance from one another.

Claim 16

The screw according to claim 14, wherein: in a cross-section of the screw body at right angles to the longitudinal axis, the contour line corresponds essentially to a bucketwheel-shaped continuous line which is radially symmetrical about the trace line of the longitudinal axis, with 3 to 8 lobes, which are salient with respect to the said direction of rotation, are approximately in the form of a ring segment, and are of approximately constant width.

Claim 17

The screw according to claim 2, wherein: a trace line of the leading flank is inclined essentially in a straight line and with respect to the said direction of rotation in each lobe area, in a cross-section of the screw body at right angles to the longitudinal axis.

Claim 18

The screw according to claim 16, wherein: the inclination of the leading flank is up to 10° from a diametric line across the cross-section of the screw body.

Claim 19

The screw according to claim 6, wherein: said semi-aperture angle is approximately 2°.

Claim 20

The screw according to claim 17, wherein: the inclination of said leading flank is about 5°.

Claim 21

A screwdriver for driving a screw that is made of biodegradable material, for bone surgery purposes, the screw having: an elongate screw body which extends, in the direction of a longitudinal axis thereof, between a proximal and a distal end thereof; an outer surface of the screw body being provided with an external thread coaxial with respect to the longitudinal axis, which external thread is for guiding and holding the screw on bone material of a patient and defines a direction of rotation about the longitudinal axis for the screwing-in of the screw body and the advancing of the distal end into the bone material; an elongate channel coaxial with respect to the longitudinal axis and provided in the screw body, which channel is open at the proximal end for receiving a shaft of a screwdriver for turning the screw; the channel having a channel wall, the shape of which is radially symmetrical about the longitudinal axis in discrete, regular rotary steps and provides, in a cross-section of the screw body at right angles to the longitudinal axis, a trace line which is a closed contour line radially symmetrical about a trace line of the longitudinal axis in discrete, regular rotary steps; the channel wall defining an axial channel area and a plurality of lobe areas arranged uniformly about the channel area, so that the channel consists essentially of the combination of the axial channel area and the lobe areas; in each lobe area, the channel wall having a pair of flanks which extend essentially from the channel area to the vicinity of an end of the lobe area remote from the channel area, and which, with reference to the said direction of rotation, define in each case a leading flank and a trailing flank; the channel extending into the area of the distal end of the screw, and in a cross-section of the screw body at right angles to the longitudinal axis, each lobe area being formed in the respect of a diametrical plane passing through the longitudinal axis, a section of the contour line which corresponds to the leading flank being shorter than a section of the contour line which corresponds to the trailing flank, so that the lobe area has a sawtooth-like profile of a radial distance of the contour line from the longitudinal axis, when considered along the contour line with, on the average, a steeper raise of the leading flank and a flatter fall of the trailing flank, for driving the screw into bone material of a patient during bone surgery, said screwdriver comprising: a grip and an elongate shaft secured to said shaft; said shaft being configured to be introduced into the channel of the screw and removed therefrom; said shaft having a form matching the channel of the screw in a complementary manner.

Claim 22

A screwdriver for driving a screw that is made of biodegradable material, for bone surgery purposes, the screw having: an elongate screw body which extends, in the direction of a longitudinal axis thereof, between a proximal and a distal end thereof; an outer surface of the screw body being provided with an external thread coaxial with respect to the longitudinal axis, which external thread is for guiding and holding the screw on bone material of a patient and defines a direction of rotation about the longitudinal axis for the screwing-in of the screw body and the advancing of the distal end into the bone material; an elongate channel coaxial with respect to the longitudinal axis and provided in the screw body, which channel is open at the proximal end for receiving a shaft of a screwdriver for turning the screw; the channel having a channel wall, the shape of which is radially symmetrical about the longitudinal axis in discrete, regular rotary steps and provides, in a cross-section of the screw body at right angles to the longitudinal axis, a trace line which is a closed contour line radially symmetrical about a trace line of the longitudinal axis in discrete, regular rotary steps; the channel wall defining an axial channel area and a plurality of lobe areas arranged uniformly about the channel area, so that the channel consists essentially of the combination of the axial channel area and the lobe areas; in each lobe area, the channel wall having a pair of flanks which extend essentially from the channel area to the vicinity of an end of the lobe area remote from the channel area, and which, with reference to the said direction of rotation, define in each case a leading flank and a trailing flank; the channel extending into the area of the distal end of the screw, and in a cross-section of the screw body at right angles to the longitudinal axis, each lobe area being formed in the respect of a diametrical plane passing through the longitudinal axis, a section of the contour line which corresponds to the leading flank being shorter than a section of the contour line which corresponds to the trailing flank, so that the lobe area has a sawtooth-like profile of a radial distance of the contour line from the longitudinal axis, when considered along the contour line with, on the average, a steeper raise of the leading flank and a flatter fall of the trailing flank, for driving the screw into bone material of a patient during bone surgery, said screwdriver comprising: a grip and an elongate shaft secured to said shaft; said shaft being configured to be introduced into the channel of the screw and removed therefrom; said shaft having a form matching the channel of the screw in a complementary manner.