WO2008044044A2

WO2008044044A2 - Surgical instruments

Info

Publication number: WO2008044044A2
Application number: PCT/GB2007/003890
Authority: WO
Inventors: Michael Ulrich Lamperth; Ian Robert Young; Philipp Bachtold
Original assignee: Imperial Innovations Ltd
Current assignee: Ip2ipo Innovations Ltd
Priority date: 2006-10-11
Filing date: 2007-10-11
Publication date: 2008-04-17
Anticipated expiration: 2009-04-11
Also published as: GB0620088D0; WO2008044044A3

Abstract

A surgical instrument (8) comprising an elongate part (10) and an operative part (12) supported on the elongate part and arranged to be inserted into body tissue. The instrument further comprises a sheath (14) attached to the support (10) and flexible between an exposing condition in which the operative part (12) is exposed and a covering condition in which it covers the operative part.

Description

SURGICAL INSTRUMENTS

The present invention relates to surgical instruments, such as biopsy needles, and in particular to the prevention of cross contamination of healthy tissue during the use of such devices on diseased tissue.

Various systems have been developed which are intended to overcome the problem of cross contamination, or seeding, of healthy tissue caused by the withdrawal of surgical instruments through the healthy tissue after operating on diseased tissue during surgical operations. For example US 2003/0097079 discloses a biopsy needle in which a rigid tubular sheath which surrounds the needle can be pushed over the end of the needle, so that it lines the whole length of the tract formed by the needle in the body, and left in place as the needle is withdrawn through it. The sheath therefore protects the healthy tissue surrounding the tract as the needle is withdrawn, and is itself withdrawn after the needle. US 2005/0228312 discloses a biopsy needle, which includes a heating device so that tissue that the needle passes through can be cauterized to prevent seeding of healthy tissue with contaminated tissue as the needle is withdrawn.

The present invention provides a surgical instrument comprising an elongate part, which may comprise support means, and an operative part attached to the elongate part and arranged to be inserted into body tissue, the instrument further comprising a sheath attached to the elongate part and flexible between an exposing condition in which the operative part is exposed and a covering condition in which it covers the operative part.

The operative part may be at one end of the elongate part.

The sheath may have an attachment portion attached to the elongate part and a flexible shielding portion. The shielding portion may be arranged to extend from the attachment portion along the elongate part away from the operative part in the exposing condition and from the attachment portion past the operative part in the covering condition.

The elongate part may comprise a shaft and a mounting portion and the attachment portion of the sheath be attached to the mounting portion. The mounting portion may be narrower than the shaft so that the attachment portion of the sheath is recessed into the support means. This can ensure that the sheath remains fastened to the support means in use.

The shielding portion may have a free end furthest from the attachment portion which is wider than the attachment portion so that it can pass over the attachment portion as the shielding portion flexes between the exposing and covering conditions. This allows the shielding portion to invert, or turn inside out, as it flexes between the two conditions.

Preferably the shielding portion is wider than the elongate part over substantially all of the length of the shielding portion so that it fits loosely around the elongate part when in the exposing condition. The shielding portion may be flared over at least a part of its length. Again, this helps to allow the shielding portion to move from the exposing condition to the shielding position.

The shielding portion may have engaging means which are on its outer surface when it is in the exposing condition and arranged to engage with the tissue into which the instrument has been inserted, as the instrument is withdrawn, thereby to assist in moving the shielding portion to the covering position.

The present invention further provides a flexible sheath for a surgical instrument the sheath comprising an attachment portion arranged to be attached to the instrument and a flexible shielding portion arranged to flex between an exposing condition in which it extends in one direction from the attachment portion and a covering position in which it extends in an opposite direction from the attachment portion.

The sheath may be formed from a hollow length of flexible sheet material having an opening at one end which forms part of the attachment portion and another opening at the other and which forms part of the shielding portion.

The present invention further provides a method of using a surgical instrument which includes a flexible sheath, the method comprising: inserting the instrument into body tissue with the sheath in an exposing condition in which an operative part of the instrument is exposed, and then pulling the instrument back through the sheath so that the sheath inverts and covers the operative part of the instrument, during withdrawal of the instrument from the tissue.

The present invention further provides a surgical instrument comprising an elongate portion arranged to be inserted through an aperture in the wall of a body cavity, and a flexible seal attached to, and extending around, the elongate portion and including a flat sealing portion arranged to lie against the surface of the wall to seal the aperture.

The present invention further provides a method of using a surgical instrument which includes an elongate portion and a flexible seal extending around the elongate portion, the method comprising inserting the elongate portion through a body tissue aperture into a body cavity such that the seal is inside the cavity, and partially retracting the elongate portion so that the seal lies against the internal surface of the cavity sealing the aperture around the elongate portion. Preferred embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a section through a surgical instrument according to a first embodiment of the invention as it is inserted into tissue;

Figure 2 is a section through the instrument of Figure 1 as it starts to be withdrawn from the tissue;

Figures 3 and 4 are sections through the instrument of Figure 1 as it is further withdrawn from the tissue;

Figure 5 is a section through a sheath forming part of a second embodiment of the invention;

Figures 6 to 8 are sections through sheaths according to three further embodiments of the invention;

Figure 9 is a side view of a cannula according to a further embodiment of the invention;

Figures 10 to 12 show insertion of the cannula of Figure 9 into a body cavity;

Figure 13 shows the cannula of Figure 9 in an operative position;

Figures 14 to 16 show extraction of the cannula of Figure 9 from the body cavity; and Figures 17 and 18 are a section and side view of a sheath forming part of a further embodiment of the invention.

Referring to Figure 1 a surgical instrument in the form of a biopsy needle 8 comprises an elongate shaft 10 with a cutting mechanism 12 attached to, and supported on, one end. Details of the cutting mechanism are not relevant to the present invention, and the cutting mechanism can take any of a number of known forms. A sheath 14 formed of flexible sheet material is attached to a mounting section 16 of the shaft just behind the cutting mechanism 12.

The sheath 14 is hollow and takes the form of a sleeve, which in this case is substantially tubular, having an attachment portion 18 at one end 19, which is the narrowest part of the sheath and of constant cross section along its length, and a shielding portion 20 which is wider than the attachment portion 18, and extends to the other end 21 of the sheath. The shielding portion 20 is wider than the attachment portion 18 and joined to it by a shoulder portion 22. The attachment portion 18 and the shoulder portion 22 are rigidly attached to the mounting section 16 of the shaft 10, for example using adhesive or binding. The whole of the shielding portion 20, from its base 20a where it joins the shoulder portion 22 to its free end 28, is free to flex and move relative to the shaft 10.

The mounting section 16 of the shaft 10 is narrower than the main part 24 of the shaft and therefore forms the bottom of a recess in the shaft the depth of which is at least equal to the thickness of the material of the attachment portion 18 of the sheath 14. Therefore the combined thickness of the attachment portion 18 of the sheath 14 and the mounting portion 16 of the shaft is no greater than, and in this case substantially equal to, the thickness of the main part 24 of the shaft. This helps to prevent the sheath 14 from being pulled away from the shaft 10 during use, as will be described in more detail below.

As shown in Figure 1 , prior to use, and as the needle 8 is being inserted into body tissue 23 of a patient, the shielding portion 20 of the sheath 14 is in an exposing condition in which it extends backwards from the attachment portion 18, i.e. away from the cutting mechanism 12 which forms the end 25 of the needle. The end 26 of the shielding portion 20 that is connected to the attachment portion 18 is closest to the cutting mechanism 12, and the free end 28 of the shielding portion 20 is furthest from the cutting mechanism. The shielding portion 20 therefore covers the front portion 30 of the shaft 10 just behind the mounting section 16. With the sheath in this condition the end 25 of the needle and the cutting mechanism 12 are exposed and the cutting mechanism can be used to cut a sample of tissue from the patient.

Referring to Figure 2, as the needle begins to be withdrawn from the tissue 23 the shielding portion 20 of the sheath 14 is held by friction against the sides of the tract 32 in the tissue through which it has been inserted. Therefore the free end 28 of the shielding portion 20 tends to remain stationary, relative to the tissue, in the tract 32, and the shaft 10, attachment portion 18 of the sheath, and the cutting mechanism 12 are pulled through the free end of the shielding portion 20. This causes the shielding portion 20 to be inverted, at first only partially as shown in Figure 2, then further as shown in Figure 3, and finally completely as shown in Figure 4.

Referring to Figure 4, when the shielding portion 20 is fully inverted, it extends forwards from the attachment portion 18 over the cutting mechanism 12, and past the very end 25 of the needle, which is formed by the end of the cutting mechanism. The shielding portion 20 is arranged to be longer, from its base 20a to its free end 28, than the distance from its base 20a to the end 25 of the needle. This means that, when in the fully inverted or covering position, it completely covers the cutting mechanism as well as completely covering the end 25 of the needle. As the needle 8 is withdrawn, the attachment portion 18, because it is recessed into the shaft 10, tends not to be pulled along the shaft, and instead remains firmly secured in place.

In this embodiment the cutting mechanism 12 is arranged both to cut a sample of tissue from inside the patient's body, and to carry the sample of tissue out of the body as the needle is withdrawn. It will be appreciated that, when the needle is fully inserted and in the position shown in Figure 1, the cutting mechanism 12 may be embedded in diseased tissue, such as cancerous tissue, while the shaft 10 may be extending through healthy tissue. This is because the tract 32 is generally formed through healthy tissue to enable the cutting mechanism 12 to reach the diseased tissue. Provided the free end 28 of the shielding portion does not reach the diseased tissue as the needle is inserted, then cross contamination of healthy tissue can be largely avoided. Any diseased tissue that comes into contact with, and is carried on, the outer surface 34 of the shielding portion 20 as the needle is inserted, will be kept away from the healthy tissue. This is because that outer surface 34 becomes the inner surface, facing away from the sides of the tract 32, when the shielding portion is inverted, and so will not contact any healthy tissue that the needle is extracted through. Similarly, because the cutting mechanism 12 is completely covered by the shielding portion 20 of the sheath 14 as it is withdrawn, any diseased tissue that is carried on the cutting mechanism, either accidentally, or because it forms part of the sample of tissue that is being extracted, cannot come into contact with the sides of the tract 32 through which it is withdrawn. The surface 37 of the shielding portion 20 that is on the outside when the sheath is in the covering condition, was on the inside as the needle was being inserted into the diseased tissue. It therefore will not generally come into contact with the diseased tissue, and will not have any diseased tissue on it.

A further benefit of this embodiment is that, because the sheath 14 is securely attached to the needle 8, it is removed from the tissue entirely as the needle is withdrawn, and no separate step is required to remove the sheath from the body after the needle has been used.

It will be appreciated that the shape of the sheath can be varied in a number of ways. Referring to Figure 5, in a second embodiment of the invention, the sheath is very similar to that of Figures 1 to 4 except that the shielding portion 120 of the sheath 114 is of a wider diameter, with its internal diameter being greater than the external diameter of the shaft 110. This makes the shielding portion 120 a loose fit around the shaft 110 which can ensure that it inverts more easily than if it is a tight fit around the shaft. In this case the shoulder portion 122 is wider, being in the form of a distinct annulus, but still extending radially outwards when the sheath is in a free, relaxed, unused condition. This means that most of the shoulder portion 122 is not rigidly fixed to the shaft 110 and is therefore free to flex, forming in effect part of the shielding portion of the sheath.

Referring to Figure 6, in a third embodiment of the invention, the sheath 214 is similar to the second embodiment except that the shoulder portion 222 is flared rather than being annular. Also in this embodiment tissue engaging ribs 240 are provided on the outer surface 234 of the shielding portion 220, i.e. the surface which faces outwards when the shielding portion is in the exposing condition as shown. These tissue-engaging ribs 240 are arranged to become engaged with, or anchored in, the tissue forming the walls of the tract, and therefore help to prevent the shielding portion 220 from sliding out of the tissue, and encourage inversion of the sheath.

Referring to Figure 7, in a fourth embodiment the shielding portion 320 is flared over the majority of its length. In this case it is flared from its base 320a where it is joined to the constant diameter attachment portion 318 to a point close to its free end 328. Although the flare could continue all the way to its free end 328, in this case there is a small section of constant diameter at the free end 328.

Referring to Figure 8 in a fifth embodiment of the invention, the shape of the sheath 414 is the same as in the fourth embodiment, but engaging ribs 440 similar to those of Figure 6 are provided on the outer surface 434 of the constant diameter section close to the free end 428 of the shielding portion 420. In this case the ribs 440 add stiffness to the part of the shielding portion 420 on which they are formed. This helps to ensure that that part of the shielding portion does not invert until at least most of the rest of the shielding portion 420 has inverted. This allows the ribs to remain engaged in the tissue until the inversion of the shielding portion 420 is substantially complete. This effect can be further enhanced by adding further stiffening of the sheath 414 in the region of the ribs 440, for example by making the sheath thicker in that region.

It will be appreciated that features of the various embodiments described above can be combined in different ways to make instruments suitable for different applications. Further modifications are also possible. For example the engaging formations on the shielding portion of the sheath can take the form of a roughened surface area, and the engaging formations can extend over areas at both ends of the shielding portion, or over the whole of its outer surface. Referring to Figure 9, a surgical instrument according to a further embodiment of the invention comprises a cannula 500 for use in laparoscopic surgery. The cannula 500 comprises a hollow tube 502 with a tip 504 at one end arranged to be inserted through body tissue 506 into a body cavity 508. When inserted the cannula acts as a port through which other surgical instruments can be inserted and withdrawn to perform the required surgery. A sheath 510 is attached to the cannula near its tip 504 and comprises a mounting portion 518 and a resilient flexible annular portion 520 extending around the cannula and extending outwards from the mounting portion 518 in a plane perpendicular to the cannula tube 502.

Referring to Figure 10, as the cannula is inserted through an aperture in the body tissue 506, in this case the abdominal wall, the sheath 510 is pushed back towards the tube 502. Referring to Figure 11 , as the sheath 510 passes through the tissue 506 of the abdominal wall into the abdominal cavity 508 it is compressed against the tube 502. Referring to Figure 12, when the whole of the sheath 510 has passed through the tissue into the cavity 508, its resilience causes it to open out at least partially to its original annular shape. Referring to Figure 13, the cannula 500 is then pulled partly back out of the tissue 506 until the sheath 510 rests against the internal side of the tissue wall. Because the annular portion 520 of the sheath is flat and of a resilient material it tends to spread out into plane perpendicular to the cannula tube 502. This in turn is approximately parallel to the cavity wall assuming that the cannula 500 is inserted normal to the wall. The annular portion 520 of the sheath, or at least the outer part thererof, can therefore easily rest against the internal side of the tissue wall. In this position the sheath acts as a seal to seal the aperture in the tissue 506 around the cannula 500. Whenever the pressure inside the cavity 508 is higher than the pressure outside, which will often be the case, the pressure inside will tend to push the sheath 510 against the inside of the cavity wall to seal it against the cavity wall. Since the sheath is sealed against the cannula by virtue of its own elasticity, it seals the hole around the cannula 500. This therefore tends to prevent the escape of fluid from the cavity 508 which can otherwise tend to carry diseased tissue with it.

Referring to Figures 14 to 16, as the cannula 500 is withdrawn from the tissue 506 the sheath 510 is urged back over the tip 504 of the cannula, covering it and preventing it from coming into contact with the tissue 506 as it is extracted. This ensures that any diseased tissue, that may have collected on the tip 504 either as it was inserted or while the cannula was in the inserted position being used, will not come into contact with the tissue on extraction.

Referring back to Figure 9, the annular sealing portion 520 of the sheath, while at least substantially flat, can be slightly dished away from the operative part, in this case the tip 504 of the cannula 500. This means that its outer edge is slightly further from the tip 504 than its inner edge. This ensures that the outer edge 520a contacts the inner surface of the cavity wall 506 first when the cannula is partially retracted as shown in Figure 13, which in turn helps to ensure that the whole area of the sealing portion is held against the cavity wall by the pressure within the cavity. The dishing is only slight, preferably less than 20° out of the plane perpendicular to the tube 502, and in this case less than 10° .

While in this embodiment the sheath 510 is arranged to serve two purposes, both sealing the port wound around the cannula 500 and shielding the end of the cannula to prevent spread of diseased tissue during extraction of the cannula, it will be appreciated that it can be used for either one of these functions without the other. For example, the sheath may be located further from the tip 504 of the cannula 500 so that it does not shield the tip during extraction, but in this case it can still be used to seal the port wound.

It will also be appreciated that the sheath can be formed of a tapered portion with an annular or other shaped flat portion at its free end. The tapered portion can then help the sheath to lie along the instrument to enclose the operative portion of the instrument, and the flat portion can still easily rest flat against the internal side of the cavity wall to perform the sealing function.

Referring to Figures 16 and 17, a moulding 600 for a sheath according to a further embodiment is formed of elastomeric material such as Latex, polyurethane or silicone... The, moulding . includes an attachment, portion. 618 and a sheath portion 620. The attachment portion 618 has a constant internal diameter and is arranged to fit around a surgical instrument as in previous embodiments. The sheath portion 620 is flared in a similar manner to the sheaths of Figures 7 and 8, but its outer surface 621 has a series of circumferential ridges 622 and grooves 623 which help to ensure that the sheath is inverted during use. The moulding includes unwanted end portions 624, 625, which are cut off along lines A to form the final sheath.

The embodiments described above can be used on a range of surgical instruments, including for example core needles, aspirated fine needles and vacuum assisted biopsy systems, as well as cannulae, endoscopes and instruments used for minimally invasive surgery.

Claims

1. A surgical instrument comprising an elongate part and an operative part attached to the elongate part and arranged to be inserted into body tissue, the instrument further comprising a sheath attached to the elongate part and flexible between an exposing condition in which the operative part is exposed and a covering condition in which it covers the operative part.

2. An instrument according to claim 1 wherein the sheath has an attachment portion attached to the elongate part and a flexible shielding portion.

3. An instrument according to claim 2 wherein the shielding portion is arranged to extend from the attachment portion along the elongate part away from the operative part in the exposing condition and from the attachment portion past the operative part in the covering condition.

4. An instrument according to claim 2 or claim 3 wherein the elongate part comprises a shaft and a mounting portion and the attachment portion of the sheath is attached to the mounting portion.

5. An instrument according to claim 4 wherein the mounting portion is narrower than the shaft so that the attachment portion of the sheath is recessed into the elongate part.

6. An instrument according to any of claims 2 to 4 wherein the shielding portion has a free end furthest from the attachment portion which is wider than the attachment portion so that it can pass over the attachment portion as the shielding portion flexes between the exposing and covering conditions.

7. An instrument according to claim 6 wherein the shielding portion is wider than the elongate part over substantially all of the length of the shielding portion so that it fits loosely around the elongate part when in the exposing condition.

8. An instrument according to any of claims 2 to 7 wherein the shielding portion is flared over at least a part of its length.

9. An instrument according to any foregoing claim wherein the sheath includes a sealing portion extending around the elongate part.

10. An instrument according to claim 9 wherein the sealing portion is flexible.

11. An instrument according to claim 9 or claim 10 wherein the sealing portion is connected to the support means by a flexible portion.

12. An instrument according to any of claims 9 to 11 wherein the sealing portion is substantially flat.

13. An instrument according to any of claims 9 to 12 wherein the sealing portion is dished.

14. An instrument according to any of claims 2 to 8 wherein the shielding portion has engaging means which are on its outer surface when it is in the exposing condition and arranged to engage with the tissue into which the instrument has been inserted, as the instrument is withdrawn, thereby to assist in moving the shielding portion to the covering position.

15. An instrument according to any foregoing claim wherein the operative part forms an end of the instrument.

16. An instrument according to any foregoing claim which is a biopsy needle, wherein the operative part is arranged to remove a sample of the tissue.

17. A surgical instrument comprising an elongate portion arranged to be inserted through an aperture in the wall of a body cavity, and a flexible seal attached to, and extending around, the elongate portion and including a sealing portion arranged to lie against the surface of the wall to seal the aperture.

18. An instrument according to claim 17 wherein the sealing portion is resilient so that it tends to lie substantially flat.

19. An instrument according to claim 17 or claim 18 wherein the sealing portion is connected to the elongate portion so that it tends to lie substantially normal to the elongate portion.

20. A flexible sheath for a surgical instrument the sheath comprising an attachment portion arranged to be attached to the instrument and a flexible shielding portion arranged to flex between an exposing condition in which it extends in one direction from the attachment portion and a covering position in which it extends in an opposite direction from the attachment portion.

21. A sheath according to claim 20 which is formed from a hollow length of flexible sheet material having an opening at one end which forms part of the attachment portion and another opening at the other and which forms part of the shielding portion.

22. A method of using a surgical instrument which includes a flexible sheath, the method comprising: inserting the instrument into body tissue with the sheath in an exposing condition in which an operative part of the instrument is exposed, and then pulling the instrument back through the sheath so that the sheath inverts and covers the operative part of the instrument, during withdrawal of the instrument from the tissue.

23. A method of using a surgical instrument which includes an elongate portion and a flexible seal extending around the elongate portion, the method comprising inserting the elongate portion through a body tissue aperture into a body cavity such that the seal is inside the cavity, and partially retracting the elongate portion so that the seal lies against the internal surface of the cavity sealing the aperture around the elongate portion.

24. A surgical instrument substantially as hereinbefore described with reference to any one or more of the accompanying drawings.

25. A sheath for a surgical instrument substantially as hereinbefore described with reference to any one or more of the accompanying drawings .

26. A method of using a surgical instrument substantially as hereinbefore described with reference to any one or more of the accompanying drawings.