The present invention relates to laparoscopic surgical scissors and a method for making a blade of the laparoscopic surgical scissors.

Laparoscopic surgical scissors generally include a handle assembly and an elongate shaft connected to the handle assembly at the proximal end of the elongate shaft. A first blade and a second blade extend from the distal end of the elongate shaft and the handle assembly is operated to open and close the blades to cut tissue.

It is known to use curved blades on laparoscopic surgical scissors. One advantage of curved blades is that they provide the surgeon with a better view of the position of the blades during use. A medio-lateral axis of laparoscopic surgical scissors may be defined as the pivot axis about which at least one of the blades of the scissors rotates during use. This then means that each blade has a medial surface which faces the medial surface of the other blade and a lateral surface opposed to the medial surface. In a curved blade of known laparoscopic surgical scissors, the blade may generally curve in a lateral direction i.e. the blade may curve in a direction away from its medial surface. This blade may be known as the inner blade. Alternatively the blade may generally curve in a medial direction i.e. the blade may curve in a direction towards its medial surface. This blade may be known as the outer blade. In known curved laparoscopic surgical scissors, a first outer blade curves in a medial direction and a second inner blade curves in a lateral direction. In this way, the first and second blades curve in the same direction and a point of contact between the first cutting edge and the second cutting edge is maintained.

The outer diameter of the elongate shaft of a laparoscopic surgical scissors can be used to classify the size of the scissors. Scissors with an elongate shaft diameter of approximately 5mm may be known as 5mm scissors and scissors with an elongate shaft diameter of approximately 3mm may be known as 3mm scissors. A smaller elongate shaft diameter results in thinner blades which can reduce the ability of the blades to remain in contact during cutting of tissue. It is desirable for the blades to remain in contact, during cutting of tissue so that a clean cut is produced. However, in a 3mm scissor, the medio-lateral width of the blades is reduced to the extent that the ability of the blades to remain in contact during the cutting of tissue may be impaired.

The present invention seeks to improve the ability of the blades of laparoscopic surgical scissors to remain in contact during cutting of tissue.

Thus viewed from one aspect the present invention provides a laparoscopic surgical scissors comprising:

a handle assembly having a handle body and an actuator which is moveable towards and away from the handle body; and

a scissor assembly which comprises:

an elongate shaft having a proximal end and a distal end and defining a longitudinal shaft axis wherein the elongate shaft is connected to the handle assembly at the proximal end of the elongate shaft;

a first blade extending from the distal end of the elongate shaft and having a first medial surface, a first lateral surface opposite the first medial surface and a first cutting edge extending between the first medial surface and the first lateral surface; and

a second blade extending from the distal end of the elongate shaft and having a second medial surface which faces the first medial surface, a second lateral surface opposite the second medial surface and a second cutting edge extending between the second medial surface and the second lateral surface,

wherein at least one of the first blade and the second blade is pivotally mounted on or near to the distal end of the elongate shaft so as to be pivotable about a pivot axis which extends along a medio-lateral axis,

wherein the first blade and the second blade open in response to movement of the actuator away from the handle body and close in response to movement of the actuator towards the handle body and a point of contact between the first cutting edge and the second cutting edge moves proximally along the first and second cutting edges as the first and second blades open and moves distally along the first and second cutting edges as the first and second blades close, wherein the point of contact in use serves to cut tissue,

wherein the first blade has a first proximal straight section and a first distal curved section, the first distal curved section defining a first curvature in the medio- lateral axis along the longitudinal shaft axis which at a first position on the first distal curved section has a centre of curvature which is nearer to the first medial surface than to the first lateral surface, and

wherein the second blade has a second proximal straight section and a second distal curved section, the second distal curved section defining a second curvature in the medio-lateral axis along the longitudinal shaft axis which at a second position on the second distal curved section has a centre of curvature which is nearer to the second medial surface than to the second lateral surface and which at a third position distal to the second position has a centre of curvature which is nearer to the second lateral surface than to the second medial surface.

In the laparoscopic surgical scissors of the present invention, the centre of curvature at the second position on the second distal curved section of the second blade is nearer to the second medial surface than to the second lateral surface. This has the effect that at the second position, the curvature of the second blade is in the medial direction which is the inverse of the lateral direction of the curvature of the second blade at the third position. This inversion may bias the second blade towards the first blade to improve the ability of the second blade to remain in contact with the first blade during cutting of tissue. This may also assist the maintenance of the point of contact between the first cutting edge and the second cutting edge during the cutting of tissue.

At each point on a curve there is circle which has an arc which fits best to the curve at that point. The radius of the circle is known as the radius of curvature of the curve at that point and the centre of the circle is known as the centre of curvature. For a C-type curve, it can be seen that the centre of curvature remains generally on one side of the C. For example, the centre of curvature is to the right of a C as written on a page. For an S-type curve, it can be seen that the centre of curvature is on one side of the S in a first section and on the other side of the S in a second section. For example, the centre of curvature is to the right of the upper section of an S as written on a page and the centre of curvature is to the left of the lower section.

The first curvature of the first blade may be in the medial direction. The first curvature of the first blade may be approximately C-shaped. The first blade may be an outer blade.

Preferably the first distal curved section is defined by a single radius of curvature.

The second curvature of the second blade may be in the medial direction at the second position and may be in the lateral direction at the third position. The second curvature of the second blade may be approximately S-shaped. The second blade may be an inner blade.

The first position may be located approximately halfway between the distal end of the elongate shaft and a distal tip of the first blade.

The second position may be located less than a third of the distance along the second blade from the distal end of the elongate shaft to a distal tip of the second blade. The second position may be located less than a quarter of the distance along the second blade from the distal end of the elongate shaft to the distal tip of the second blade.

The third position may be located approximately halfway between the distal end of the elongate shaft and the distal tip of the second blade. The radius of curvature at the second position may be less than the radius of curvature at the third position. The radius of curvature at the second position may be less than the radius of curvature at the first position. The radius of curvature at the third position may be less than the radius of curvature at the first position when the blades are closed. The radius of curvature at the second position may be less than half of the radius of curvature at the third position. The radius of curvature at the second position may be less than a quarter of the radius of curvature at the third position. The centre of curvature at the second position may be between the first blade and the second blade. The centre of curvature at the second position may be between the first lateral surface and the second lateral surface. The centre of curvature at the second position may be within the diameter of the elongate shaft projected to the second position.

The first blade and the second blade may be moveable between a fully open position and a fully closed position. When the first blade and the second blade are in the fully open position, the point of contact between the first cutting edge and the second cutting edge may be at its most proximal position. When the first blade and the second blade are in the fully closed position, the point of contact may be at its most distal position.

When the first blade and the second blade are in the fully closed position, the first medial surface and the second medial surface may overlap. The second blade may be biased against the first blade. The cause of the biasing may be the curvature of the second blade at the second position.

The centre of curvature at the second position may move when the blades are moved between the fully open position and the fully closed position. This movement of the centre of curvature at the second position may be due to the bias created by the curvature at the second position.

The first blade and/or the second blade may be overbent. When the blades are in the fully open position, an overbent blade extends in the medial direction to a greater extent than when the blades are in the fully closed position. Therefore when the blades are moved from the fully open position to the fully closed position, the medial surfaces of the blades push against each other and the curvature of one or more of the blades changes from the fully open position to the fully closed position. The curvature of the second blade at the second position may have a spring effect. The curvature of the second blade at the second position may act as a flat spring. The spring effect may improve the ability of the second blade to remain in contact with the first blade during cutting of tissue.

The first blade and the second blade may be made of stainless steel. The material of the second blade may be selected to be suitable for use as a flat spring.

The elongate shaft may include an inner shaft and an outer shaft. The inner shaft may be moveable proximally or distally with respect to the outer shaft. An actuation mechanism for closing and opening the blades may be connected at or near to a distal end of the inner shaft. The movement of the inner shaft may operate the actuation mechanism which may cause the first blade and/or the second blade to pivot about the pivot axis and close or open. The inner shaft may be made of stainless steel. The outer shaft may be made of aluminium or stainless steel. Preferably the outer shaft is made of stainless steel. The outer shaft may be covered in a polymer tube to create an electrical insulation layer over the outer shaft. The polymer tube may be attached to the outer shaft by a heat-shrink process.

The outer diameter of the elongate shaft may be approximately 5mm. The outer diameter of the elongate shaft may be approximately 3mm. The laparoscopic surgical scissors may be 5mm scissors. The laparoscopic surgical scissors may be 3mm scissors.

At least one of the first blade and the second blade is pivotally mounted on or near the distal end of the elongate shaft. Laparoscopic surgical scissors with one blade pivotally mounted and the other blade fixed may be known as single action scissors. Preferably the first blade and the second blade are pivotally mounted on or near to the distal end of the elongate shaft. Laparoscopic surgical scissors with both blades pivotally mounted may be known as double action scissors. Suitable actuation mechanisms for single action laparoscopic surgical scissors and double action laparoscopic surgical scissors are known in the art and can be readily selected by a skilled person.

At least a part of the laparoscopic surgical scissors may be intended for a single use or disposable. For example, the scissor assembly may be intended for a single use or disposable. The scissor assembly may be detachably fastenable to the handle assembly. The scissor assembly may include a fastener for fastening to the handle assembly. The fastener may be a cone nut. The cone nut may be slidably mounted on the elongate shaft. The handle assembly may be re-usable.

The laparoscopic surgical scissors may be re-useable. The laparoscopic surgical scissors may be intended for a single use or disposable.

Viewed from a further aspect, the present invention provides a scissor assembly as defined herein.

Viewed from a yet further aspect the present invention provides a method for making a second blade for a laparoscopic surgical scissors as defined herein comprising forming the curvature at the second position of the second blade in a forming tool which has a first shape and forming the curvature at the third position of the second blade in a forming tool which has a second shape.

The first shape may have a first shaping curvature in a first shaping direction. The second shape may have a second shaping curvature in a second shaping direction. The first shaping direction may be a medial direction and the second shaping direction may be a lateral direction.

A single forming tool may include the first shape and the second shape. Alternatively, a first forming tool may have the first shape and a second forming tool may have the second shape.

The second shape may be configured to leave the curvature at the second position of the second blade unaltered. The forming tool may be a stamping tool. The forming tool may be a metal injection moulding tool. Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which like reference numerals indicate like parts and in which: Figure 1 depicts a view of a first embodiment of the laparoscopic surgical scissors of the present invention;

Figure 2 depicts a perspective view of the scissor assembly of the embodiment of Figure 1 with the blades in an open position;

Figure 3 depicts a side view of the scissor assembly of the embodiment of Figure 1 with the blades in a closed position;

Figure 4 depicts a side view of the scissor assembly of the embodiment of Figure 1 with the blades in an open position;

Figure 5 depicts a top view of the scissor assembly of the embodiment of Figure 1 with the blades in an open position and without the outer shaft or cone nut;

Figure 6 depicts a similar view to Figure 5 with the outer shaft shown in dashed lines; Figure 7 depicts a magnified view of the blades of Figure 6 showing the radii of curvature of the second blade;

Figure 8 depicts a magnified view of the blades of a second embodiment of the invention showing the radii of curvature of the second blade;

Figure 9 depicts a magnified view of the blades of a third embodiment of the invention showing the radii of curvature of the second blade;

Figure 10 depicts a first forming tool used in an embodiment of the method of the invention; and

Figure 11 depicts a second forming tool used in the method of the invention.

In the first embodiment shown in Figure 1, the laparoscopic surgical scissors 2 comprises a handle assembly 4 having a handle body 6 and an actuator 8 in the form of a pivoted lever. The actuator 8 is moveable towards and away from the handle body 6 to operate the laparoscopic surgical scissors 2. When the actuator 8 is moved toward the handle body 6, a first blade 20 and a second blade 30 close to cut tissue during use. When the actuator 8 is moved away from the handle body 6, the first blade 20 and the second blade 30 open. The laparoscopic surgical scissors 2 further comprises a scissor assembly 10 which includes an elongate shaft 12 having a proximal end 14 and a distal end 16 and a longitudinal shaft axis 13. The elongate shaft 12 is detachably fastenable to the handle assembly 4 by means of a cone nut 11 which is slidably mounted on the elongate shaft 12.

As shown in Figure 2 the scissor assembly 10 includes the first blade 20 and the second blade 30 which extend from the distal end 16 of the elongate shaft 12. The first blade 20 and the second blade 30 are pi vo tally connected to the elongate shaft 12 via a pivot which defines a pivot axis 40. The pivot axis 40 extends in a medio-lateral axis. The first blade 20 has a first cutting edge 26 and the second blade 30 has a second cutting edge 36.

The first blade 20 and the second blade 30 are movable between a fully closed position shown in Figure 3 in which a point of contact 44 between the first blade 20 and the second blade 30 is at its most distal location and a fully open position shown in Figure 4 in which the point of contact 44 is at its most proximal position.

Figures 3 and 4 also show that the elongate shaft 12 of the scissor assembly 10 comprises an inner shaft 15 made of stainless steel and an outer shaft 17 made of stainless steel. The outer shaft 17 is covered by a fluoropolymer tube 19 to create an electrical insulation layer over the outer shaft 17. The fluoropolymer tube is attached to the outer shaft 17 by a heat- shrink process. The electrical insulation layer allows an electrical current to be passed to the first blade 20 and the second blade 30 along the inner shaft 15 from an electrosurgical generator (not shown) attached to an electrocautery pin 5 on the handle assembly 4 without electrical current passing through the electrical insulation layer. In this way the electrical current can be directed to the first blade 20 and the second blade 30 for electrocautery without damaging tissue in contact with the elongate shaft 12.

The inner shaft 15 is moveable proximally or distally with respect to the outer shaft 17 to operate an actuation mechanism 18 (shown in Figure 5) which causes the first blade 20 and the second blade 30 to pivot about the pivot axis 40 and close or open. Figure 5 shows the inner shaft 15 attached to the first blade 20 and the second blade 30 via an actuation mechanism 18. The outer shaft 17 is not shown in Figure 5. Figure 6 shows the outer shaft 17 in a dashed line and also shows the pivot axis 40 on which the first blade 20 and the second blade 30 pivot when actuated by the actuation mechanism 18 in response to proximal or distal movement of the inner shaft 15 with respect to the outer shaft 17.

Figure 7 is a magnified illustration of the first blade 20 and the second blade 30 in the fully closed position. The first blade 20 extends from the distal end 16 of the elongate shaft 12. The first blade 20 has a first proximal straight section 50 and a first distal curved section 52 which defines a first curvature 54. The first blade 20 has a first medial surface 22 and a first lateral surface 24. The first cutting edge 26 extends between the first medial surface 22 and the first lateral surface 24. In Figures 7, 8 and 9 the medial and lateral surfaces extend into and away from the plane of the paper.

At a position anywhere along the first distal curved section 52 of the first blade 20 (for example, at position 56), the first curvature 54 has a centre of curvature which is closer to the first medial surface 22 than to the first lateral surface 24. For example, it can be seen from the radius of curvature 57 at position 56 that the centre of curvature is positioned outside the drawing.

The second blade 30 has a second proximal straight section 60 extending from the distal end 16 of the elongate shaft 12. The second blade 30 has a second medial surface 32 and a second lateral surface 34. The second cutting edge 36 extends between the second medial surface 32 and the second lateral surface 34.

The second blade 30 has a second distal curved section 62 which defines a second curvature 64. At a second position 66 the second curvature 64 has a centre of curvature 68 which is closer to the second medial surface 32 than the second lateral surface 34. At the second position 66 the second distal curved section 62 has radii of curvature 67. At a third position 70 which is distal of the second position 66 on the second distal curved section 62 the second curvature 64 has a centre of curvature (not shown) which is closer to the second lateral surface 34 than to the second medial surface 32. This is shown by the radii of curvature 71 which extend outside the drawing. The second curvature 64 of the second blade 30 at the second position 66 biases the second blade 30 towards the first blade 20. Figure 8 shows a second embodiment of the laparoscopic surgical scissors 2. Features which are not shown are similar to the laparoscopic surgical scissors of the first embodiment. In the second embodiment the radii of curvature 67 at the second position 66 are longer than in the first embodiment. However the second centre of curvature 68 is still within the limits of a projected outer diameter of the elongate shaft 12 as shown by the diameter of the distal end 16 of the elongate shaft 12.

Figure 9 shows a third embodiment of the laparoscopic surgical scissors 2. Features which are not shown are similar to the laparoscopic surgical scissors of the first embodiment. In the third embodiment the second position 66 has a centre of curvature 68 between the first lateral surface 24 and the second lateral surface 34.

Figures 10 and 11 show a first forming tool 112 and a second forming tool 114 for use in a method according to an embodiment of the invention. In this method, the first forming tool 112 has a first shape 102 comprising a first shaping curve 106. The first tool 112 is used to stamp a second blade 30 of a laparoscopic surgical scissors 2. The first shaping curve 106 provides a curvature at the second position 66 of the second blade 30 of the laparoscopic surgical scissors 2.

The second forming tool 114 shown in Figure 11 is then used to stamp the curvature at the third position 70 on the second blade 30 using the second shaping curve 108. It can be seen that the second shape 104 has a configuration including a cut-out portion 110 which is configured so as not to alter the shape of the second blade 30 at the second position 66 when the second blade 30 is stamped by the second forming tool 114.