A New Single-Use Bone Marrow Biopsy Needle with Core Retention Design

A needle for obtaining a solid core (trephine) bone marrow biopsy sample from the posterior ilium is described. The needle is comprised of a hollow stainless-steel tube whose front-end diameter is reduced in comparison with the proximal segment. At its terminus the needle is also beveled and has six circumferentially spaced facets thereby forming a sharp cutting edge. The segment of the tube between the longer wider portion of the hollow tube and its smaller reduced diameter front end portion has a series of diamond shaped serrations/flutes on its surface which offer enhanced cutting ability as with a saw to assist in easy penetration of the needle through the dense cortical bone and into the marrow cavity.


Introduction
Bone marrow (BM) biopsy plays an important role in the investigation, diagnosis and management of various haematological as well as non-haematological malignant conditions [1][2][3][4]. Since the development of an improved BM biopsy needle [5,6] and its introduction in a disposable form, there has been a considerable growth in its use. The value of BM biopsy, particularly in different haematological conditions is now well established [7,8]. However, loss of core samples during their extraction, i.e., failure to retain the complete biopsy sample within the lumen of the needle as the needle is withdrawn from the patients has been a serious continuing problem. The importance and significance of this particular problem was recognized and was successfully addressed by the development of an improved bone marrow biopsy needle with a core retention device [9]. But until the present time this needle was not available in a disposable form because of technical manufacturing limitations and the cost involved. In recent years technology has emerged which obviate these problems and as a result such a needle can be made economically and in large numbers. Taking advantage of this new technology, a new singleuse bone marrow biopsy needle that retains the original principle of core retention device has now been produced. In addition, a new feature has been added to the design. It consists of a series of surface serrations (flutes) at the tapering transitional portion which ease the boring through the dense cortical bone and entry into the spongy hematopoietic bone. Furthermore, an easy technique of removing the biopsy sample from within the lumen of the needle has also been introduced. In this technique, an insertion aid is used to remove the biopsy specimen. This insertion aid has been designed to receive the distal cutting end of the needle on one side and the front end of the pusher rod on the other side. In this way, the operator can utilize the insertion aid to expel the biopsy sample easily through the proximal end of the needle.

Materials and Methods
The steel instrument ( Figure 1) consists of five parts: The needle ( Figure 1A) which has an overall length of 125 mm, a uniform external diameter 3.25 mm, and a constant internal diameter of 2.5 mm except for the 3.5 mm distal portion where it is narrowed and has multiple surface serrations/flutes ( Figure   2C). The terminus of the needle has six sharp cutting facets ( Figure   2B). The internal diameter of the needle's distal portion is less than the overall internal diameter of the needle and begins with a short-slanted step of 0.2 mm. This specially designed distal portion ( Figure 3E) cuts all the trabecular connections of bone which might keep the biopsy specimen anchored to its base and also holds on to the biopsy sample so that it does not slip out of the needle during the process of its withdrawal. The larger internal diameter of the needle at its proximal segment provides free space ( Figure   3B) within the interior of the instrument thus avoiding crushing and compression of the tissue as well as plugging the lumen of the needle.     Once this penetration has been achieved, the stilette is withdrawn (2). The needle is then advanced with slow, steady and controlled clockwisecounterclockwise rotary motion (3). When an adequate depth is reached the needle is rotated several times along its long axis and then withdrawn with a straight pull (4). No rocking, sculling movement or change in the direction of the tip of the needle are necessary.

Figure 5:
Demonstrates the introduction of the needle. As stated in the text it is useful to put one hand over the anterior iliac crest with the middle or index finger on the anterior superior iliac spine as shown in the photograph (arrow). This approach not only helps stabilize the patient's pelvis but also helps in the guidance of the needle towards the anterior superior iliac spine.

Results
The needle has been extensively tested. An adequate sample was obtained with each attempt. Bony trabeculae were clean cut and crushing artefact was almost negligible even at the edges of the biopsy specimen. The quality of the specimen obtained with this needle has been excellent in each case (Figure 9). Although the 'sample or core losing' problem of the Jamshidi needle was soon recognized and was addressed by the development of a new bone marrow biopsy needle with a core retention design [9], this particular needle has not been available in a disposable -i.e., single-use form until the present time. To overcome the problem of losing the core biopsy specimen several different single use needles have been Introduced [11][12][13]. Each of these needles features different methods of securing a core sample during withdrawal of the needle from the patient. Unfortunately, all of these alternatives significantly complicate the procedure by introducing multiple steps and an assortment of supplementary parts and components.
Indeed, in some cases, these needles contain six or more additional parts. Furthermore, these core-capturing devices (e.g., sleeve, coil, connections at its base which might keep the biopsy specimen firmly anchored to its base but also holds the core sample with pincer-like action so that it does not slip out of the needle during its extraction ( Figure 3E).
Once the biopsy specimen has entered the needle and has passed beyond the narrower segment the sample is able to expand to some extent. Here, the internal step acts as a shoulder which prevents the slightly expanded biopsy sample from slipping out of the needle during its withdrawal. In addition, the larger internal diameter of the needle provides free space ( Figure 3C