Bone marrow biopsy needle

A needle for use in taking a bone marrow biopsy comprises a hollow tube having a front end portion formed to a reduced diameter by swaging. The front end is tapered by means of a number of circumferentially-spaced facets, forming a cutting edge. A tapering transition portion, between the main portion of the hollow tube and its reduced-diameter front end portion, is formed with a series of flutes which help in the needle cutting through the cortical bone. A spacer is provided for use in pushing the sample rearwardly out of the hollow tube, the spacer having a through-passage through which a trocar needle is passed and serving for accurate alignment of the distal ends of the hollow tube and trocar needle.

FIELD OF THE INVENTION

The present invention relates to a biopsy needle for use in taking a bone marrow biopsy sample from a posterior iliac crest of a patient.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 4,543,966 and UK patent No. 2,099,703 relate to a bone marrow biopsy needle assembly which comprises an elongate hollow needle having open front and rear ends, the front end being provided with a cutting edge: furthermore, a portion of the needle, adjacent its front end, is of a reduced internal diameter and an internal shoulder is formed between the inner end of this reduced-diameter portion and the WIDER main portion of the needle. The hollow needle is used with a trocar needle or stilette which is inserted into the hollow needle from its rear end, for a pointed front end of the trocar needle to project beyond the front end of the hollow needle.

In use, this assembly is gradually advanced, by hand, through the soft skin tissue and then through the cortical bone of the patient, by the execution of alternate clockwise and counterclockwise rotations of the assembly around its longitudinal axis. Once the assembly has advanced through the cortical bone, to reach the underlying spongy or medullary bone, the trocar needle or stilette is withdrawn from the hollow needle: then the hollow needle is advanced into the spongy bone, again by the execution of alternate clockwise and counterclockwise rotations or rotary motions of the hollow needle; it will be appreciated that a core sample of bone marrow will accordingly enter the hollow needle, from its front end. When the hollow needle has been advanced to a sufficient depth into the spongy bone, about 20 to 25 mm, the hollow needle is rotated several times about its longitudinal axis to sever all the trabecular connections at its base and break the core sample loose from the rest of the spongy bone, and is then withdrawn. The core sample of bone marrow is retained within the hollow needle and this retention is particularly facilitated by the internal step which acts as a shoulder and also because of the fact that the core sample expands in diameter in the wider portion of the needle, inwardly or to the rear of the front end portion of reduced internal diameter. The core sample is subsequently removed from the hollow needle by inserting an elongate pusher rod into the hollow needle from its front end.

The above-described biopsy needle assembly is effective in use but it is necessary to make the hollow needle by hand, in order to provide its front end portion of reduced diameter: the hollow needle is accordingly expensive to manufacture. Also, I have now devised a modification to the needle in order to improve its ability to advance through the cortical bone.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a needle for use in taking a bone marrow biopsy, the needle comprising a hollow tube having a main portion, a front end portion formed to a reduced diameter compared with said main portion, and a tapering portion disposed between said main portion and said front end portion, said tapering portion comprising a series of flutes spaced apart around its circumference.

The flutes, provided on the tapering portion of the hollow needle, serve for cutting the cortical bone, by alternate clockwise and counterclockwise rotations of the hollow needle, to allow the larger-diameter main portion of the needle to advance smoothly and without resistance through the cortical bone.

Also, in accordance with the present invention, there is provided a needle for use in taking a bone marrow biopsy, the needle comprising a hollow tube having a front end portion formed to a reduced diameter by swaging.

It will be appreciated that the above-defined hollow needle will be used with a trocar needle or stilette to form a biopsy needle assembly for use in taking a bone marrow biopsy. This biopsy needle assembly is used in the same manner as the assembly of the above-noted U.S. Pat. No. 4,543,966 and UK patent No. 2,099,703. However, the hollow needle does not have to be made by hand: the swaging process, to form the reduced-diameter front end portion of the hollow needle, may be carried out by machine and the hollow needle is therefore less expensive to manufacture.

Preferably a transverse and domed handle is mounted to the rear end of the hollow tube, a domed head or cap is mounted to the rear end of the trocar needle or stilette, and a spacer is disposed between the handle and the head of the trocar needle, the spacer being formed with a through-passage through which the trocar needle passes. The spacer is used when removing the core sample from the hollow needle: thus, the reduced diameter front end portion of the hollow needle is engaged into one end of the through-passage of the spacer; then the pointed front end of the trocar needle is inserted through the spacer passage from its opposite end, and into the end of the hollow tube. The trocar needle is advanced to push the sample out of the rear end of the hollow needle.

Also in accordance with the present invention, there is provided a method of forming a needle for use in taking a bone marrow biopsy, the method comprising providing a hollow tube and swaging a front end portion of the tube to a reduced diameter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring toFIG. 1of the drawings, there is shown a disposable needle assembly for taking a bone marrow biopsy sample. The assembly comprises a hollow needle10, fitted, at its rear end, with a transverse handle20having a domed end21: the assembly further comprises a trocar needle or stilette22having a pointed front end23and a domed head24at its rear end, the trocar needle22being shown inserted through a spacer30and through the hollow needle10for its pointed end23to project from the front end of the hollow needle10. The spacer30has a concave-profiled lower end31to seat on the domed end21of the handle20of the hollow needle10, and a convex-profiled upper end32for the underside of the head24of the trocar needle22to seat upon.

Referring toFIGS. 2 and 3of the drawings, the hollow needle10comprises a stainless steel tube of circular cross-section and uniform diameter, a front end portion12of which has been formed to a reduced diameter by swaging. The front end of the tube10is tapered by means of six equi-angularly spaced facets11, thus forming a cutting edge14. The swaging process, for forming the front end portion to its reduced diameter, results in the formation of a generally frustoconical transition portion16between the main portion of the tube10and the front end portion12: the outer surface of this transition portion is formed with twelve equi-angularly spaced flutes18. Typically, the tube10may have a uniform external diameter of 3.25 mm and a uniform internal diameter of 2.5 mm, except for the front end portion12which is typically 3.5 mm in length and has an internal diameter (e.g. of 2.1 mm) less than the internal diameter of the main portion of the tube.

The biopsy needle assembly of the present invention is used in the same manner as the assembly of the above-noted U.S. Pat. No. 4,543,966 and UK patent No. 2,09,703. When the assembly reaches the spongy bone (FIG.3), the trocar needle22is withdrawn. The hollow needle10is then advanced further, the flutes18on the transitional portion16serving to cut through the cortical bone as the needle is turned alternatively clock-wise and anti-clockwise, to allow the larger-diameter main portion of the hollow needle10to pass through the cortical bone. When the hollow needle10has been advanced a sufficient depth into the spongy bone, the hollow needle10is rotated several times to cut all the trabecular connections and break the core sample loose from its base, and is then withdrawn. Using this device, the core sample is retained within the hollow needle10, being embraced at its trailing end by the reduced-diameter front end portion of the hollow needle10the main portion of the hollow needle is of larger diameter, beyond the tapering transition between the main portion and front end portion, so that impaction, crushing and compres-sion of the core sample are prevented. As the core sample enters the wider main portion of the hollow tube10, it expands slightly in diameter, helping to prevent it slipping out of the needle as the latter is withdrawn: the core sample remains free, however, to slide rearwardly along the main portion of the hollow tube when pushed out by the trocar needle, as described below.

Referring toFIG. 5, the core sample is removed from the hollow needle in the following manner. The spacer30is applied to the forward end of the hollow needle10, this end of the hollow needle10engaging into the lower end of a central bore34through the spacer. The pointed front end of the trocar needle or stilette22is then inserted through the spacer30from its upper end, and into the end of the hollow needle10: the trocar needle22is advanced to push the sample out of the rear end of the hollow needle10. It will be noted that the central bore34of the spacer is funnel-shaped at both its ends35,36, to facilitate introduction of the ends of the hollow needle10and trocar needle22. The spacer30accordingly forms an effective aid for alignment of the trocar needle22with, and its insertion into, the hollow needle10.

In contrast to the biopsy needle of U.S. Pat. No. 4,543,966 and UK patent No. 2,099,703, the hollow needle10is not required to be made by hand: in particular, the swaging process, to form the reduced-diameter front end portion12, may be carried out by machine; also, the tapering facets11, to form the cutting edge14, and the flutes18may all be formed by machine. The biopsy needle10is accordingly relatively easy to manufacture, less expensive and more importantly enabling a large number of such needles to be produced in a short time span, which is essential where the needles are intended for single-use.