Bone cement needle

A needle assembly for dispensing a bone cement mixture is provided. The needle assembly includes a cannula defining an inner lumen, the cannula having an outlet end for dispensing the bone cement mixture from the assembly. The outlet end has at least one tip moveable between an expanded position and a collapsed position. The tip is configured to cut the bone cement mixture in the collapsed position when the cannula is rotated. The needle assembly also has an inner member disposed within the inner lumen of the cannula, which is movable between an extended position and a retracted position. The inner member is operable to hold the tip in the expanded position when the inner member is in the extended position. The tip automatically collapses into the collapsed position when the inner member is in the retracted position. A method of introducing a bone cement mixture into a damaged bone of a patient is also disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to medical devices and more particularly, to needles for insertion of a bone cement mixture into a cavity of a damage bone.

There is a clinical need to fill and stabilize damaged bones of patients, such as for example, filling defects in collapsed vertebrae of patients suffering from severe back pain caused by osteoporosis, metastatic tumors or back injuries. Currently, these defects are repaired using multi-component bone cements that are injected into the damaged bone where the mixture chemically reacts or cures to form a solid support structure. The most widely used bone cements are based on polymethylmethacrylate (PMMA) and hydroxyapatite.

One procedure that is typically used to fill defects in collapsed vertebrae is known as vertebroplasty. This procedure involves injecting bone cement directly into the fracture void through a minimally invasive cannula or needle. The bone cement may be radio-opaque and monitored via fluoroscopy. The cement may be pressurized by a syringe to cause the cement to fill the void. Once cured, the cement stabilizes the vertebra and reduces pain. Kyphoplasty is another similar procedure that may be used to inject bone cement into a fracture void. Typically, thicker bone cements are used with kyphoplasty than with vertebroplasty.

Although safe and effective, one issue with vertebroplasty and kyphoplasty is containment of the bone cement within the area of the vertebra having the defect. Cement may typically flow beyond the confines of the bone into other areas of the body. Typically, the bone cement has a high level of coherence such that the cement particles tend to adhere to other surrounding cement particles. Therefore, when an application cannula is withdrawn from the body, it will carry a trail of bone cement with it, which is typically cut near the skin surface.

To address the problem of cement containment within the bone fracture or void area, some practitioners have utilized fillable mesh bags or containers inside of the vertebra. However, upon filling, the expansion of such a bag or container can cause undesirable compaction on the surrounding fractured bone. Furthermore, the bag or container may still be permeable and release some of the bone cement into the surrounding body cavity. Another drawback of using mesh bags and/or containers is that they may add an expense to the procedure.

In view of the above and other defects known in the art, there remains a need for a bone cement delivery system that more adequately effects bone cement containment within the vertebra fracture, without adding significant costs to the procedure.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an affordable, effective bone cement delivery system that cuts or shears viscous bone cement at the fracture area, thereby decreasing the likelihood of bone cement being applied in other areas of the body cavity.

In one aspect of the present invention, a needle assembly for dispensing a bone cement mixture is provided. The needle assembly includes a cannula defining an inner lumen, the cannula having an outlet end for dispensing the bone cement mixture from the assembly. The outlet end has one or more tips moveable between an expanded position and a collapsed position. The tip or tips are configured to cut the bone cement mixture in the collapsed position when the cannula is rotated. The needle assembly also has an inner member disposed within the inner lumen of the cannula. The inner member is movable between an extended position and a retracted position and is operable to hold the tip or tips in the expanded position when the inner member is in the extended position. The tip or tips automatically collapse into the collapsed position when the inner member is in the retracted position.

In another aspect, a cannula for dispensing a bone cement mixture into a damaged bone of a patient is provided. The cannula has a tubular body having an inner side defining an inner lumen. The cannula has an inner diameter and an outlet end for dispensing the bone cement mixture from the cannula. The cannula also has a plurality of tips connected to the outlet end, which are movable between an expanded position and a collapsed position. The plurality of tips extends across the inner diameter in the collapsed position and defines a plurality of openings at the outlet end. The plurality of tips is configured to cut the bone cement mixture in the collapsed position when the needle cannula is rotated.

In yet another aspect, a method of introducing a bone cement mixture into a damaged bone of a patient is provided. The method includes a step of piercing the damaged bone of the patient with a needle assembly to define a bone opening. The needle assembly is provided having a cannula and an inner member movable to extend from an outlet end of the cannula. The cannula has an inner side defining an inner lumen and has an inner diameter. A plurality of tips is connected to the outlet end, the tips being movable between an expanded position and a collapsed position. The inner member is operable to hold the plurality of tips in the expanded position when the inner member extends from the cannula. The method includes a step of advancing the bone cement mixture through the lumen of the cannula and dispensing the bone cement mixture into the bone opening. Another step includes filling the damaged bone of the patient with the bone cement mixture. The method includes a step of retracting the inner member into the lumen of the cannula, the plurality of tips automatically collapsing into the collapsed position when the inner member is retracted into the lumen of the cannula. In the collapsed position, the plurality of tips extends across the inner diameter and defines a plurality of openings at the outlet end. The method also includes rotating the cannula when the plurality of tips is in the collapsed position, the plurality of tips cutting the bone cement mixture upon rotation of the cannula.

Further objects, features and advantages of the invention will become apparent from consideration of the following description and the appended claims when taken in connection with the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIG. 1, a needle assembly for dispensing a bone cement mixture is illustrated and generally designated at10. The needle assembly10includes a cylindrical cannula12defining an inner lumen14through the center of the cannula12along a center longitudinal axis X of the cannula12. A cylindrical inner member16is disposed within the lumen16of the cannula12. The cannula12has an outlet end18for dispensing the bone cement mixture from the assembly10. The cannula12also has an inlet end20for receiving the bone cement mixture, which will be described in further detail below.

The inner member16may be slid or otherwise moved within the lumen16of the cannula12between an extended position and a retracted position. InFIG. 1, the inner member16is shown in the extended position, wherein the inner member16extends from the outlet end18of the cannula12. The inner member16may be a needle stylet, as shown inFIG. 1, or it may have any other suitable configuration, for example, the inner member16could be an inner cannula. The stylet16has a pointed end22for piercing through a damaged bone. The stylet16may have a handle24at a proximal end26for gripping by the user to move the stylet16within the lumen14and to remove the stylet16from the cannula12.

The inner member16may be formed of a flexible, high-tensile strength polymeric material, such as polyetheretherketone (PEEK), or any other suitable material, such as metal or other polymers.

The outlet end18of the cannula12has a pair of tips28(inFIG. 1, only one of the pair of tips28may be seen, as the other is hidden behind the inner member16). The tips28may each have a spring force such that each tip28tends to automatically collapse toward the center longitudinal axis X of the cannula12. Thus, the tips28are moveable between an expanded position and a collapsed position.

The tips28are preferably formed of a superelastic material, such as nickel titanium (Nitinol®). More preferably, the tips28are formed unitarily with the cannula12, which is also formed of nickel titanium. In the alternative, the tips28may be formed of a material different than the material of the cannula12, and the tips28may be attached to, rather than formed unitarily with, the cannula12. Furthermore, the tips28and/or the cannula12could alternatively be formed of another superelastic material, such as stainless steel, cobalt-chromium-nickel-molybdenum-iron alloy, or cobalt-chrome alloy by way of example. It should be understood that the tips28may be formed of any suitable material that will result in the tips28being self-collapsing, such as shape memory material.

Shape memory materials or alloys have the desirable property of becoming rigid, i.e., returning to a remembered state, when heated above a transition temperature. A shape memory alloy suitable for the present invention is nickel titanium. This material may be formed such that when it is heated above the transition temperature, the material undergoes a phase transformation from martensite to austenite, such that material returns to its remembered state. The transition temperature is dependent on the relative proportions of the alloying elements nickel and titanium and the optional inclusion of alloying additives.

In one embodiment, the tips28are made from Nitinol with a transition temperature that is slightly below normal body temperature of humans, which is about 98.6° F. Thus, when the tips28are inserted into a bone opening and exposed to normal body temperature, the alloy of the tips28will transform to austenite, that is, the remembered state, which for one embodiment of the present invention is the collapsed state.

In another embodiment, the tips28are made from Nitinol with a transition temperature that is above normal body temperature of humans, which is about 98.6° F. Thus, when the tips28are inserted into a bone opening and exposed to normal body temperature, the tips28are in the martensitic state so that the tips28are sufficiently ductile to bend or form into a desired shape, which for the present invention is the expanded state. The tips28may then be heated to transform the alloy to austenite so that it becomes rigid and returns to a remembered state, which for the tips28is the collapsed state.

In the expanded position, the tips28extend from the cannula12in a substantially straight line along the exterior of the cannula12. In the alternative, the tips28could extend slightly inward toward the center longitudinal axis X in the expanded position. The inner member16is operable to hold each tip28in the expanded position when the inner member16is in the extended position, as shown inFIG. 1. In other words, the inner member16is operable to straighten the tips28.

With reference toFIGS. 2-4, the stylet16is shown removed from the cannula12. After the stylet16is moved completely into the cannula12in the retracted position, the tips28will automatically collapse inward toward the center longitudinal axis X, by virtue of the spring force contained in the tips28, or by virtue of heating or cooling of the shape memory material, as described above. In other words, the tips28return to their preset shape.FIG. 2shows the stylet immediately after being pulled into the retracted position, and for clarity the tips28are shown in the expanded position, although in reality, they will automatically collapse immediately after the stylet16is retracted into the lumen14of the cannula12. With reference toFIGS. 3 and 4, the tips28are shown in a side view (FIG. 3) and a front view (FIG. 4), wherein the tips28have collapsed into the collapsed position, toward the center longitudinal axis of the cannula12.

InFIG. 3, it may be seen that the tips28collapse inward at approximately a 45-degree angle A with respect to a tangent line T extending from the main body of the cannula12in the collapsed position. In the alternative, the tips28could collapse inward at any other suitable angle, for example, forming a 60-degree angle (not shown) with the tangent line T extending from the main body of the cannula in the collapsed position. As another example, with reference toFIG. 5, the tips128may collapse inward to form a 90-degree angle B with respect to a tangent line T of the cannula12in the collapsed position.

With reference toFIGS. 6A-6D, end views are illustrated of various embodiments for tips28,228,328,428of the cannula12,212,312,412. For example,FIG. 6Ashows a pair of tips28in the collapsed position as hereinbefore discussed with reference toFIGS. 1-4. Each tip28of the pair of tips28has a pointed end30that extends across a portion of the diameter of the lumen14of the cannula12to contact the pointed end30of each other tip28of the pair of tips28. Thus, in the collapsed position, the tips28contact each other to define a plurality of openings32at the outlet end18of the cannula12in the collapsed position. In this embodiment, each tip28has a triangular shape, wherein one side of each tip28is connected to the main body portion of the cannula12.

With reference toFIG. 6B, a single tip228is connected to the outlet end218of a cannula212. In all other respects, the cannula212and inner member (not shown inFIG. 6B) may be similar to those hereinbefore or hereinafter described. Like the tips28ofFIGS. 1-4and6A, the tip228ofFIG. 6Bis also configured to move between an expanded position and a collapsed position, the tip228having a spring force such that the tip228automatically collapses into the collapsed position shown upon removal of the inner member (not shown). In the alternative, the tip228may automatically collapse upon heating or cooling the shape memory material, as described above. The single tip228may have a triangular shape as shown. One opening232surrounds the tip228.

With reference toFIG. 6C, a triad of tips328is connected to the outlet end318of the cannula312. In all other respects, the cannula312and the inner member (not shown inFIG. 6C) may be similar to those hereinbefore or hereinafter described. Like the tips28,128,228of the previousFIGS. 1-6B, the tips328ofFIG. 6Care also configured to move between an expanded position and a collapsed position. The tips328have a spring force such that the tips328automatically collapse into the collapsed position shown upon removal of the inner member (not shown). In the alternative, the tips328may automatically collapse upon heating or cooling the shape memory material as described above. The tips328may have a triangular shape as shown. The tips328each extend partially across the diameter of the lumen314of the cannula312to contact each other and define a plurality of openings332through which bone cement may be dispensed.

With reference toFIG. 6D, a pair of tips428is connected to the outlet end418of the cannula412. In all other respects, the cannula412and the inner member (not shown inFIG. 6D) may be similar to those hereinbefore or hereinafter described. Like the tips28,128,228,328of the previousFIGS. 1-6C, the tips428ofFIG. 6Dare also configured to move between an expanded position and a collapsed position. The tips428may have a spring force such that the tips428automatically collapse into the collapsed position shown upon removal of the inner member (not shown). In the alternative, the tips428may automatically collapse upon heating or cooling the shape memory material, as described above. The tips428differ from the tips28,228,328hereinbefore described as they do not have a triangular shape; the tips428have a rectangular shape with one side of the rectangle being connected to the main body of the cannula412. It is preferable, but not mandatory, that the tips428each extend partially across the diameter of the lumen414of the cannula412to contact each other and define a plurality of openings432through which bone cement may extend.

In any of the embodiments of tips28,128,228,328,428described herein, each of the tips28,128,228,328,428have side edges that are configured to shear or cut the bone cement mixture being dispensed therefrom, which be described in further detail below, when the tips28,128,228,328,428are in the collapsed position.

With reference toFIGS. 7-11, after the needle assembly10has been inserted into a bone cavity, the stylet16may be removed, while the cannula12is left within the bone cavity. Although the bone cavity is not illustrated herein, it should be understood that in each ofFIGS. 2-11, the cannula12is left in the bone cavity. A syringe34having a pusher rod36is filled with a bone cement mixture, which may be mixed in the syringe34itself or separately from the syringe34. A tip38of the syringe is matingly connected to the lumen14of the cannula12. The pusher rod36is used to push the bone cement mixture into the lumen14of the cannula12, and further, to dispense the bone cement mixture from the outlet end18of the cannula12and into the bone cavity (or other suitable delivery site).

The bone cement mixture may be radio-opaque such that the filling of the bone cavity may be monitored via fluoroscopy, and/or the bone cement mixture may be made of any suitable material, as is known to those having ordinary skill in the art. It is contemplated that the present invention will be particularly useful with bone cements having at least a moderate level of viscosity that would be dragged by the application cannula absent some shearing force cutting the bone cement.

When the practitioner desires to stop the filling process and remove the cannula12from the bone cavity, the practitioner may first remove the syringe34from the cannula12as shown inFIG. 9. Thereafter, the cannula12may be rotated. The edges of the tips28are provided with sufficient sharpness to cut the bone cement mixture upon rotation of the cannula12when the tips28are in the collapsed state. A suction force may then be used, if desired, to extract excess bone cement from the cannula to avoid further application of the bone cement within the body. With the bone cement being severed at the bone cavity area, or other delivery site, the bone cement may be applied in only the desired areas, without dragging bone cement through the body to the surface of the skin to be cut.

With reference toFIGS. 12A-12C, another needle assembly510is illustrated. The needle assembly510ofFIG. 12A-12Chas an outer cannula512, which is substantially similar to one of the cannulas12,112,212,312,412of the previous figures. As such, the outer cannula512defines an inner lumen514and has an inlet end520, an outlet end518, at least one tip528, and an inner member516disposed within the lumen514of the outer cannula512. InFIGS. 12A-12C, the inner member

The inner cannula516may be positioned in the extended position to deliver an unimpeded flow of bone cement mixture into the bone opening. Thus, the inner cannula516defines a lumen550therein through which the bone cement mixture is advanced. A stylet552may be inserted through the lumen550of the inner cannula516to pierce the damaged bone. Before delivering the bone cement mixture, the stylet552is then removed from the inner cannula516. In the alternative, the inner cannula516could have a sharp distal end540to pierce through the damage bone.

After the bone opening is filled with bone cement mixture, the inner cannula516may be retracted into the outer cannula512, allowing the tips528to automatically collapse in the collapsed position. The outer cannula512may then be rotated to cut the bone cement mixture. Thus, in the embodiment ofFIGS. 12A-12C, the bone cement mixture is delivered into the bone opening while the tips528are held in the open position, which may be ideal for very viscous bone cement mixtures in which the tips528may impede the flow of the bone mixture to an undesirable level.

With reference toFIG. 12A, the inner cannula516extends from the outlet end518of the outer cannula512, thereby straightening the tips528in the expanded position. The stylet552extends from the distal end540of the inner cannula516to pierce the damaged bone. With reference toFIG. 12B, the stylet552has been removed from the needle assembly510. To apply the bone cement mixture, the tip538of a syringe534having a plunger536is placed in fluid communication with the lumen550of the inner cannula516. The plunger536of the syringe534is operable to advance bone cement into the inner cannula516and further into a bone opening, provided that the needle assembly510is located in the bone opening when the bone cement mixture is being advanced out of distal end540of the inner catheter516.

After applying the bone cement mixture, the inner cannula516may be retracted into the outer cannula512in the retracted position, as shown inFIG. 12C. When the inner cannula516is retracted into the lumen514of the cannula512, the tips428automatically collapse into the collapsed position, such that the bone cement mixture may be cut by rotating the outer cannula512. For a representative end view of the tips528in the collapsed position, seeFIGS. 6A-6D, as any one of these configurations or others could be used.

In the alternative, the inner cannula516may be removed from the outer cannula512before the bone cement mixture is applied, and the bone cement mixture may be applied directly into the lumen514of the outer cannula512, similarly to the embodiments ofFIGS. 7-11.

With reference to the block diagram ofFIG. 13, a method of introducing a bone cement mixture into a damaged bone of a patient is illustrated and generally designated at600. For illustration of the devices used for the method600, reference may be made toFIGS. 7-12C. The method600includes a step602of piercing the damaged bone of the patient with a needle assembly to define a bone opening. The needle assembly is preferably one of the types hereinbefore described. As such, the needle assembly has a cannula and an inner member movable to extend therefrom. The cannula has an inner side defining an inner lumen and has an inner diameter and an outlet end. A plurality of tips is connected to the outlet end. The tips are movable between an expanded position and a collapsed position. The inner member is operable to hold the plurality of tips in the expanded position when the inner member extends from the cannula in an extended position.

The inner member could be, for example, a stylet or an inner cannula, as hereinbefore described. If the inner member is a stylet, it is retracted into the cannula and removed from the cannula. If the inner member is an inner cannula, the inner member may extend from the outlet end of the cannula to deliver bone cement mixture, and then be retracted into the lumen of the cannula. When the inner member is retracted into the cannula, the plurality of tips automatically collapses into the collapsed position, as hereinbefore described. In the collapsed position, the plurality of tips extends across the inner diameter to define a plurality of openings at the outlet end of the cannula.

To apply bone cement mixture, fluid communication between the lumen of the cannula and an injection device comprising the bone cement mixture is provided. If the inner member is an inner cannula, the fluid communication is provided between the lumen of the inner cannula and the injection device. The bone cement mixture is dispensed into the lumen of the cannula, and the method600includes a step604of advancing the bone cement mixture through the lumen of the cannula and dispensing the bone cement mixture into the bone opening. The method600further includes a step606of filling the bone opening with the bone cement mixture.

Thereafter, the practitioner should cease advancing the bone cement mixture through the lumen of the cannula. The method600then includes a step608of rotating the cannula when the plurality of tips are in the collapsed position, the plurality of tips cutting the bone cement mixture upon rotation of the cannula. This step608may also include completely separating the bone mixture into a first portion of the bone cement mixture located in the cannula and a second portion of the bone cement mixture located in the damaged bone, which allows removal of the cannula without dragging the bone cement mixture through the body cavity to the skin level. The cannula may then be retracted from the damaged bone.