WO2005009246A1

WO2005009246A1 - Needle instrument for transcutaneous biopsy of bone marrow tissues

Info

Publication number: WO2005009246A1
Application number: PCT/IB2004/002377
Authority: WO
Inventors: Enrico Malagoli
Original assignee: Enrico Malagoli
Priority date: 2003-07-28
Filing date: 2004-07-26
Publication date: 2005-02-03
Also published as: ITMI20031540A1; EP1653862A1

Abstract

The present invention relates to a needle instrument (1) for transcutaneous biopsy of bone marrow tissues, comprising a hollow cannula (2) having a proximal end (3), with a handle (4) for manipulating the cannula (2), and a distal end (5), having a substantially constant section all along its length, with a coring edge (6), a stylet (10) being adapted to be introduced in the cannula (2) of said needle instrument (1), which has a proximal end (11) fitted with a handle (12) and a sharp distal end (13), the length of said stylet (10) being such that the distal end of the stylet (13) extends beyond the distal end (5) of the cannula (2), characterized in that said coring edge (6) has a non circular inner cross section.

Description

NEEDLE INSTRUMENT FOR TRANSCUTANEOUS BIOPSY OF BONE MARROW TISSUES

This invention relates to a needle instrument for transcutaneous biopsy of bone marrow tissues. Various instruments are currently known for collection of bone marrow tissues. Needle instruments are particularly known, which comprise a hollow metal cannula with one end, the so-called proximal end, having a handle for manipulating the instrument and the other end, the so-called distal end, having a coring edge for cutting out a cylindrical tissue portion to be collected. A stylet may be introduced in the cannula, and be manipulated by a handle fitted at the proximal end of the stylet, which has such a length that the stylet tip extends beyond the distal end of the cannula. The stylet tip is used to pierce the skin, the adipose tissues and bundles of muscles interposed between the skin and the bone tissue, and the bone tissue itself. The stylet further prevents tissues other than the sample to be collected from being introduced in the cannula during the piercing step. Once the stylet has penetrated to the area of interest, the stylet is removed and the cannula is further advanced, to isolate and enclose therein a substantially cylindrical portion of tissue (the so- called "core") which forms the biopsy sample to be collected. The biopsy sample is still joined at its bottom to the underlying tissue, i.e. outside the needle. Once the cannula has been inserted in the tissue to be collected, the portion of tissue enclosed within the cannula must be detached from or torn off the underlying tissue. Only when the tissue in the cannula has been severed from the underlying tissue, the cannula may be extracted from the patient's body. The biopsy sample in the caimula is finally ejected by an ejector. The resection of the portion of tissue enclosed in the cannula is a particularly critical step in the above described biopsy process. According to a first known approach, resection of the tissue in the cannula is obtained by imparting repeated rotary and oscillatory motions to the cannula. Nevertheless, the oscillatory motions imparted to the cannula for detaching the biopsy sample cause bone injuries and microfractures, increased pain to the patient and longer healing times. Also, this approach does not ensure a total detachment of the biopsy sample from the underlying tissue. If any portion of the biopsy sample falls out of the cannula while the latter is being extracted, the biopsy procedure must be repeated, thereby aggravating injury and pain to the patient. In order that the biopsy sample can be retained within the cannula, the hollow distal portion of the cannula may have a tapered shape converging toward its end. In order that the biopsy sample may be retained even better within the cannula, appropriate members may be used for securing the tissue sample, which are inserted between the inner wall of the cannula and the tissue sample, and which radially deflect, due to the taper of the end portion of the cannula, thereby fπctionally securing the biopsy sample within the cannula. Typically, the tissue sample securing members may include a pair of opposed curved blades, which are deformed due to the taper or an elastic blade having a cylindrical profile with a longitudinal slot. Thanks to these sample securing members, the sample may be removed from the underlying tissue by simply rotating the cannula, without having to impart any oscillatory motion thereto. The biopsy sample is thus more reliably removed. Such arrangements are disclosed, for example, in patent US-A-5,333,619 and in patent application WO 02/053035. However, a cannula that has an interiorly tapered distal end reduces the available volume for collection of the biopsy sample, whereby an increased diameter of the cannula is required, which causes higher injury to the patient. Moreover, the need of providing a cannula with an interiorly tapered distal end involves higher needle fabrication costs. Also, the need of providing tissue sample securing means further complicates the fabrication of the instrument and increases fabrication costs. Furthermore, the step of inserting the securing means is a further complication for the operator. The object of this invention is to obviate at least some of the drawbacks of prior art needle instruments, and particularly the above mentioned drawbacks. This object is fulfilled by providing a needle instrument for transcutaneous biopsy of bone marrow tissues according to claim 1. Further advantages may be obtained thanks to the additional characteristics of the dependent claims. A possible embodiment of the instrument, as claimed in the claims of this patent, is described hereafter with reference to the accompanying drawings, in which: - Figure 1 is a front view which shows the step of inserting the stylet in the cannula; - Figure 2 is a front view which shows the assembled needle and stylet combination; - Figures 3-5 show an operational sequence of a biopsy procedure by the instrument of Figures 1 and 2; - Figure 6 is a cross sectional view of Figure 5; and - Figure 7 is an enlarged view of the tip of the needle instrument. Referring to the drawings, the reference numeral 1 denotes a needle instrument for transcutaneous biopsy of bone marrow tissues. This instrument comprises a hollow cannula 2, having a substantially constant cross section all along its length, with a proximal end 3, having a handle 4 for manipulating the instrument 1, and a distal end 5 having a coring edge 6 which is adapted to penetrate bone marrow tissues in such a manner as to enclose a generally cylindrical biopsy sample 20. Typically, the cannula 2 is made of metal, e.g. stainless steel. Preferably the coring edge 6 has a plurality of teeth 6a, 6b, 6c, to facilitate the penetration of bone tissues. A stylet 10 may be inserted in the cannula 2 of the needle instrument 1, and has a proximal end 11, fitted with a handle 12, and a sharp distal end 13. The length of the stylet 10 is such that the distal end 13 of the stylet extends beyond the distal end 5 of the cannula 2. The stylet 10 to be used may be a conventional stylet, therefore it will not be further described. Suitably, the handles 4, 12 are shaped in such a manner as to match complementarily and means 14, 15 may be provided for removably fastening the handle 12 of the stylet to the handle 5 of the cannula 2, thereby providing an easier penetration to the relevant tissues. These fastening means 14, 15 are also known, therefore they will not be further described. It will be appreciated that the distal end 5 of the cannula 2 has a constant cross section, apart from any unavoidable processing and measurement tolerances. It will be further noted that the lack of tapered or narrowed profiles in the distal end 5 allows to optimize the volume of the collected biopsy sample 20, which makes the biopsy procedure less invasive. One feature of the needle instrument 1 is that the inner section of the coring edge 6 has not a circular shape. Thanks to this non-circular cross section of the coring edge 6, by rotating the cannula 2, the base 21 of the biopsy sample 20 is subjected to a twisting action, which causes the biopsy sample to be severed from the underlying tissue. Thanks to this characteristic, a highly reliable needle instrument may be obtained in a simple manner and at a low cost. Preferably, the inner cross section of the coring edge 6 is substantially or generally a polygon, e.g. a square or a triangle. This design is particularly effective and is also easily achievable. Those skilled in the art may obviously provide other cross sectional shapes for the coring edge 6. For instance, in lieu of a substantially and/or generally polygonal cross section, a substantially and/or generally elliptical cross section may be used. The non circular design of the coring edge 6 may be obtained, for instance, by using a cannula 2 having a circular coring edge 6 and by deforming the coring edge 6 with a substantially pyramidal tool. The operation of the instrument is as follows. When performing a biopsy procedure, the operator holds the instrument 1 with the stylet 10 in the operating position and introduces the instrument 1 through adipose and muscular tissues into the bone tissue until he/she feels a reduced resistance, i.e. until the needle has penetrated the bone marrow. Then, the operator extracts the stylet from the cannula, and pushes the latter further into the bone marrow tissue, until it encloses a tissue portion, which forms the biopsy sample 20. Then the operator rotates the cannula 2, whereby the coring edge 6, due to its non circular cross section, imparts a twisting motion to the base 21 of the sample within the cannula 2, thereby detaching the sample from the underlying tissue. Finally, the cannula 2 is extracted and the collected biopsy sample 20 is extracted from the cannula by an ejector.

Claims

CLAIMS 1. A needle instrument (1) for transcutaneous biopsy of bone marrow tissues, comprising a hollow cannula (2) having - a proximal end (3), with a handle (4) for manipulating the cannula (2), - and a distal end (5), having a substantially constant section all along its length, with a coring edge (6), a stylet (10) being adapted to be introduced in the cannula (2) of said needle instrument (1), which has a proximal end (11) fitted with a handle (12) and a sharp distal end (13), the length of said stylet (10) being such that the distal end of the stylet (13) extends beyond the distal end (5) of the cannula (2) characterized in that said coring edge (6) has a non circular inner cross section. 2. A needle instrument as claimed in claim 1, wherein said coring edge 6 has a substantially and/or generally polygonal inner cross section. 3. A needle instrument as claimed in claim 2, wherein said coring edge 6 has a substantially and/or generally square inner cross section. 4. A needle instrument as claimed in claim 2, wherein said coring edge 6 has a substantially and/or generally triangular inner cross section. 5. A needle instrument as claimed in claim 1, wherein said coring edge 6 has a substantially and/or generally elliptical inner cross section.