Bone is made up of a hard outer core, known as cortical bone or cortical plate, and a soft spongy interior known as cancellous bone or trabecular bone, which includes a marrow filling in the porous space within the spongy bone (commonly referred to as bone marrow). The cortical plate is very hard and provides the rigid structure to the skeleton, which allows the skeleton to bear weight. Bone marrow is rich in capillary beds.
Marrow aspiration is usually obtained from the hip bone. Currently, to draw larger volumes of marrow, clinicians usually go into the hip bone through the iliac crest. The goal is to penetrate deep into the spongy bone and then to withdraw small aliquots of marrow as the needle is withdrawn. Traditionally, marrow aspiration is performed with an aspiration needle 100 (FIG. 1). This needle has two basic components: a component comprising a handle 104 with a luer connector 110 for attaching a syringe 106 on one end, and a hollow metal tube or cannula 102 (also referred to as a cannulated trocar) on the other end; and a component (not shown in FIG. 1) comprising a second handle attached to a solid metal rod or stylet with a sharp pointed tip. The stylet of the marrow aspiration needle is removable. When assembled, the second handle fits over the first handle and the stylet fits through the cannula 102, including the luer connector 110 and handle 104, such that the pointed tip of the stylet extends past the distal end of the cannula 102. This entire needle assembly is often referred to as a JAMSHIDI® aspiration needle.
To perform a marrow aspiration, a clinical practitioner uses the fully assembled needle to penetrate cortical bone 112 using the point of the stylet. The clinician uses hand pressure or a mallet to tap the assembled aspiration needle through the bone. The cannula and stylet are usually made of stainless steel or titanium. The assembled aspiration needle is very hard and stiff so that the needle will not bend or buckle when longitudinal force is applied against the proximal handle to allow it to penetrate the cortical bone. Once the hard cortical bone 112 is penetrated, the assembled needle easily advances through the trabecular bone, including spongy marrow, 114. During insertion, the stylet is left in place to prevent the hollow cannula from becoming clogged with debris as the needle is pushed through the spongy marrow. Once the needle assembly is advanced sufficiently into the trabecular bone 114, the stylet, including the stylet handle, is removed to expose the luer connector 110. Luer connector 108 of syringe 106 is attached to the luer connector 110 of the needle and a vacuum created by pulling the syringe plunger will remove the marrow (FIG. 1). Marrow aspirate is pulled through the distal end of the cannula 102 and into the syringe 106 as the needle 100 is slowly removed from the marrow space 114.
A traditional bone marrow aspiration needle is typically used to access marrow from the hip or iliac bone. Because the traditional aspiration needle is stiff, the needle can only advance linearly within the marrow space. Once the needle is through the cortical plate, the cannula only has access to whatever marrow is directly ahead of the cannula tip, but cannot bend or access marrow to the sides of the cannula. Thus, clinicians often need to perform multiple punctures in order to gain larger volumes of aspirate from a more diverse cross section of the marrow space. Since the hip bone is long and thin, once the traditional aspiration needle has penetrated cortical bone, the sharp and stiff instrument has the potential to penetrate through the other side of the cortical bone, resulting in significant trauma. Consequently, it is important for the surgeon to have a proper angle and skilled technique to ensure a safe aspiration. Since the iliac crest curves from the front to the back of the patient, the best angle of entry is from the back. Since the stylet is made of a stiff material, once inside the spongy bone, the needle assembly can only go straight, thus requiring multiple punctures to obtain the required volume of aspirate.
A traditional marrow aspiration needle is meant to access bone marrow from larger cavities and is not ideally suited to drawing marrow from the smaller confines such as the vertebral body of the spine. Because of the sharpness and stiffness of a traditional aspiration needle, using such an instrument in the small curved marrow space of a vertebral body would greatly increase the likelihood of introducing trauma. Less invasive and safer methods to access the marrow tissue of the vertebral body are needed in an effort to support the emerging field of orthobiologics. One fast growing area of this field combines marrow aspirate with synthetic matrix material in order to facilitate instrumented assisted spinal fusion.
Therefore, a need exists for a bone marrow aspiration device that can reduce or minimize the aforementioned problems.