Patent Description:
Chronic joint pain, including osteoarthritis of the knee, is a major health problem resulting not only in debilitating conditions for the patient, but also in the consumption of a large proportion of funds allocated for health care, social assistance and disability programs. In joints, osteoarthritis is the most common form of arthritis pain and occurs when the protective cartilage on the ends of bones wears down over time. Currently, there are an estimated <NUM> million patients with osteoarthritis of the knee, with <NUM> million of those patients suffering from advanced symptoms of osteoarthritis.

A minimally invasive technique of delivering high-frequency electrical current has been shown to relieve localized pain in many patients. Generally, the high-frequency current used for such procedures is in the radiofrequency (RF) range, i.e. between <NUM> and <NUM> and more specifically between <NUM>-<NUM>. The RF electrical current is typically delivered from a generator via connected electrodes that are placed in a patient's body, in a region of tissue that contains a neural structure suspected of transmitting pain signals to the brain. The electrodes generally include an insulated elongate member with an exposed conductive tip to deliver the radiofrequency electrical current. Tissue resistance to the current causes heating of tissue adjacent resulting in the coagulation of cells (at a temperature of approximately <NUM> for small unmyelinated nerve structures) and the formation of a lesion that effectively denervates the neural structure in question. Denervation refers to a procedure whereby the ability of a neural structure to transmit signals is affected in some way and usually results in the complete inability of a neural structure to transmit signals, thus removing the pain sensations. This procedure may be done in a monopolar mode where a second dispersive electrode with a large surface area is placed on the surface of a patient's body to complete the circuit, or in a bipolar mode where a second radiofrequency electrode is placed at the treatment site. In a bipolar procedure, the current is preferentially concentrated between the two electrodes.

To extend the size of a lesion, radiofrequency treatment may be applied in conjunction with a cooling mechanism, whereby a cooling means is used to reduce the temperature of the electrode-tissue interface, allowing more energy or power to be applied without causing an unwanted increase in local tissue temperature that can result in tissue desiccation, charring, or steam formation. The application of more energy or power allows regions of tissue further away from the energy delivery device to reach a temperature at which a lesion can form, thus increasing the size/volume of the lesion.

The treatment of pain using high-frequency electrical current has been applied successfully to various regions of patients' bodies suspected of contributing to chronic pain sensations. For example, with respect to knee pain, which affects millions of individuals every year, high-frequency electrical treatment has been applied to several tissues, including, for example, the ligaments, muscles, tendons, and menisci. However, the existing cooled RF treatments of the knee and other regions of the body are confined to being performed in hospital-based settings due to the high cost of the probe assemblies and their associated radiofrequency generators, coolant fluid pumps, and other equipment.

Due to the large volume lesions generated by cooled radiofrequency ablation probe procedures, care must be taken when treating sensitive locations, particularly around areas that cannot sustain significant collateral ablative damage. Furthermore, existing cooled radiofrequency probes are often top-heavy and may impart a large torque about the probe insertion point due to the mass of the probe handle and the rigidity of the tubing and cable that are connected to the probe. As a result, the existing cooled RF probes are often unwieldy and difficult to manipulate, thereby increase the risk of improper insertion and tissue injury at the probe insertion site. Further, in existing treatments, each cooled radiofrequency probe must be attached to its own respective electrical and fluid supply, requiring the use of many cables and tubes in a small treatment area which may interfere with the surrounding probes.

Moreover, existing cooled radiofrequency probes are difficult to manufacture, requiring intense processes requiring long assembly cycle times including multiple long-duration curing stages. The manufacturing difficulty of the existing cooled RF probes thereby results in increased cost to manufacture. As a result of the increased cost of the probes, cooled RF treatments have been confined to hospital-based settings due to reimbursement constraints.

Consequently, there is a need for a system for treating chronic pain using cooled RF ablation techniques that is particularly optimized for treating a patient's knee, and more particularly improved cooled radiofrequency ablation probes that are particularly optimized for treating the tissue of a patient's knee joint and have a reduced manufacturing cost. Moreover, a cooled radiofrequency probe assembly that can be manufactured at a lower cost and thereby expand treatments into settings outside of hospitals, such as doctor's offices or ambulatory service centers, would be useful.

<CIT> discloses a system for high-frequency ablation of body tissue. The system includes a cooled high-frequency electrode that is connected to a high frequency generator including a computer graphic control system and an automatic controller for controlling the signal output from the generator.

According to the present invention, there is provided a cooled radiofrequency ablation probe assembly according to claim <NUM>. Embodiments of the ablation probe assembly are defined in the dependent claims.

Reference will now be made in detail to one or more embodiments of the invention, examples of the invention, examples of which are illustrated in the drawings. Each example and embodiment is provided by way of explanation of the invention, and is not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment may be used with another embodiment to yield still a further embodiment.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings, but is defined in the claims.

The invention is capable of other embodiments or of being practiced or carried out in various ways in accordance with the claims.

For the purposes of this invention, a lesion refers to the region of tissue that has been irreversibly damaged as a result of the application of thermal energy. Furthermore, for the purposes of this description, proximal generally indicates that portion of a device or system next to or nearer to a handle of the probe (when the device is in use), while the term distal generally indicates a portion further away from the handle of the probe (when the device is in use).

As used herein, the terms "about," "approximately," or "generally," when used to modify a value, indicates that the value can be raised or lowered by <NUM>% and remain within the disclosed embodiment.

Referring now to the drawings, <FIG> illustrates a cooled radiofrequency ablation probe assembly <NUM> of the present invention. As shown, the probe assembly <NUM> includes a first probe <NUM> and a second probe <NUM> which are arranged in series, with the second probe <NUM> being positioned downstream of the first probe <NUM>. In an alternate embodiment, the probe assembly can include more than two probes. The probe assembly <NUM> further includes an electrical cable <NUM> for supplying energy to the probes <NUM> and <NUM>, and cooling fluid tubing <NUM> for carrying cooling fluid to and from the probes <NUM> and <NUM>. The electrical cable <NUM> and the cooling fluid tubing <NUM> communicate with each of the probes <NUM>, <NUM> at a probe handle <NUM> of each probe.

The electrical cable <NUM> may be formed as a Y-shaped electrical cable. Alternately, the electrical cable <NUM> may be T-shaped. The electrical cable <NUM> includes an electrical connector <NUM> located at an end of the cable <NUM> opposite from the probes <NUM>, <NUM>. The electrical connector <NUM> may be a <NUM>-pin circular connector. The connector <NUM> is connected to a single electrical cable <NUM>. The single electrical cable <NUM> splits at a grommet <NUM> into two discrete cables with three conductors each, forming a first probe electrical cable <NUM> which connects to the first probe <NUM> and a second probe electrical cable <NUM> which connects to the second probe <NUM>. As shown in <FIG>, the probes <NUM>, <NUM> can be connected to the electrical cable <NUM> in parallel via the first probe electrical cable <NUM> and the second probe electrical cable <NUM>.

Still referring to <FIG>, the cooling fluid tubing <NUM> can include an inlet connector <NUM>, for example a female Luer connector, for connecting to a cooling fluid source (not shown). The cooling fluid tubing <NUM> inlet portion <NUM> may extend from the inlet connector <NUM> to the first probe <NUM>. A connecting tubing portion <NUM> of cooling fluid tubing <NUM> extends between the first probe <NUM> and the second probe <NUM>, which is downstream of the first probe <NUM> along the fluid tubing <NUM>. An outlet tubing portion <NUM> can extend from the second probe <NUM> to an outlet connector <NUM>, for example a male Luer connector. In one embodiment, the outlet connector <NUM> may connect to the cooling fluid source (not shown) to form a closed-loop cooling fluid system. In an alternative embodiment, the outlet connector <NUM> may connect to a waste bag (not shown) for disposal of the cooling fluid.

The connecting tubing portion <NUM> connects between the first probe <NUM> and the second probe <NUM> so that cooling fluid flows from the first probe <NUM> to the second probe <NUM> before flowing through outlet tubing portion <NUM> to the fluid source or waste bag (not shown). The connecting tubing portion <NUM> may cool the cooling fluid based on the temperature of ambient air. For example, if cooling fluid is heated as it flows through the first probe <NUM>, the heat captured by the cooling fluid can be dissipated into the atmosphere by the ambient air temperature as the cooling fluid flows through connecting tubing portion <NUM> before reaching the second probe <NUM>. The connecting tubing portion <NUM> has a length sufficient to dissipate any heat captured by cooling fluid in the first probe into the atmosphere prior to the cooling fluid flowing into the second probe <NUM>.

The top view of the probe assembly <NUM> illustrated in <FIG> shows lengths of the electrical cable <NUM> and cooling fluid tubing <NUM> of the probe assembly <NUM>. The length of the connecting tubing portion <NUM> and/or the first probe electrical cable <NUM> and second probe electrical cable <NUM> may dictate the farthest straight-line distance L<NUM> between the probes <NUM> and <NUM>. The distance L<NUM> is from about <NUM> inches (<NUM>) to about <NUM> inches (<NUM>), such as from about <NUM> inches (<NUM>) to about <NUM> inches (<NUM>). In one embodiment, the straight-line distance L<NUM> between probes <NUM> and <NUM> is about <NUM> inches (<NUM>). The single electrical cable <NUM> extending from the grommet <NUM> to the electrical connector <NUM> has a length L<NUM> which may be from about <NUM> inches (<NUM>) to about <NUM> inches (<NUM>), such as from about <NUM> inches (<NUM>) to about <NUM> inches (<NUM>). In one embodiment, the length L<NUM> of the single electrical cable <NUM> may be about <NUM> inches (<NUM>). The inlet tubing <NUM> and outlet tubing <NUM> may each have a length L<NUM> which may be from about <NUM> inches (<NUM>) to about <NUM> inches (<NUM>), such as from about <NUM> inches (<NUM>) to about <NUM> inches (<NUM>). In one embodiment, the distance L<NUM> of the inlet tubing <NUM> and outlet tubing <NUM> is about <NUM> inches (<NUM>).

The length of the single electrical cable L<NUM>, the distance L<NUM> between the probes, and the length L<NUM> of the tubing limits the cooled RF probe assembly <NUM> to be used for patient treatment sites that may be positioned close to a radiofrequency generation source and pump for the cooling fluid. For example, a patient's knee may be positioned on an outer edge of a bed, chair, or other surface and directly adjacent to the RF source and pump. In contrast, this embodiment may not be able to be used for treating a patient's spine because the relatively shorter lengths of the electrical cable <NUM> and the cooling fluid tubing <NUM> would not reach from the RF source and pump all the way to the center of a patient's back when the patient is laying face-down on a treatment bed or table.

Referring back to <FIG>, extending from the handle <NUM> of each of the probes <NUM>, <NUM> is an elongate member <NUM> forming a radiofrequency treatment assembly. In one embodiment, the first probe <NUM> may have a longer elongate member <NUM> than the elongate member <NUM> of the second probe <NUM>. For example, the first probe <NUM> may have an elongate member length L<NUM> of about <NUM> (<NUM> inches) or about <NUM> (<NUM> inches), and the second probe <NUM> may have an elongate member length L<NUM> of about <NUM> (<NUM> inches) or about <NUM> (<NUM> inches). In another embodiment, the first probe <NUM> and the second probe <NUM> may have equal elongate member lengths of about <NUM> (<NUM> inches) or about <NUM> (<NUM> inches). In yet another embodiment, the elongate member <NUM> of the first probe <NUM> may be shorter than the elongate member <NUM> of the second probe <NUM>.

Referring now to <FIG>, the elongate member <NUM> of each probe <NUM>, <NUM> forms an electrocap assembly that is thermally and electrically conductive for delivering electrical or radiofrequency energy to the patient's tissue. A distal end <NUM> of the elongate member <NUM> opposite the probe handle <NUM> forms an active tip <NUM> for delivering the cooled radiofrequency treatment to the patient's tissue. The electrocap assembly may include at least one fluid conduit <NUM> within the elongate member <NUM>, such as an inlet fluid conduit 116a and an outlet fluid conduit 116b, for delivering cooling fluid to and from the active tip <NUM>. The electrocap assembly may additionally include a thermocouple hypotube <NUM> extending the length of the elongated member <NUM> and protruding from the distal end of the elongated member. The thermocouple hypotube <NUM> may include a wire <NUM> made from an electrically conductive material such as constantan. The wire <NUM> can be insulated along the entire length of the elongated member <NUM> and welded to the hypotube <NUM> at a distal end <NUM> of the electrocap assembly to form a thermocouple <NUM>. The cooling fluid may be circulated in a volume <NUM> within the distal end <NUM> of the electrocap assembly adjacent the thermocouple <NUM> to control the temperature of the active tip <NUM>. <FIG> illustrates a cross-sectional view of the distal end <NUM> of the elongated member <NUM>.

As shown in <FIG>, in an alternative embodiment, the assembly <NUM> may include an alternative probe handle <NUM> for the dual cooled radiofrequency probe assembly. The probe handle <NUM> can be generally cylindrical shaped and can communicate with an electrical cable <NUM> and cooling fluid tubing <NUM> at one end and an elongated radiofrequency treatment probe <NUM> at an opposite end. The cylindrical shape of the probe handle <NUM> extends in a longitudinal direction that is in parallel with the electrical cable <NUM>, cooling fluid tubing <NUM>, and elongated radiofrequency treatment probe <NUM>, as shown in <FIG>.

Turning back to <FIG>, probes <NUM> and <NUM> having unequal elongate member lengths are shown. Providing probes <NUM> and <NUM> with staggered probe elongate member lengths L<NUM> and L<NUM>, for example about <NUM> and about <NUM>, respectively, further conforms the treatment to the knee anatomy by enabling one deeper and one more superficial treatment simultaneously at different sites within one knee joint. Additionally, the relatively short (less than about <NUM>, and in some embodiments less than or equal to about <NUM>) elongate member lengths L<NUM> and L<NUM> of the probes <NUM> and <NUM> can be optimized for treatment of the knee because treatment sites in the knee joint are superficially located just under the skin. In comparison, cooled RF probes for treatment of the spine or hip may require have longer elongate member lengths to penetrate deep into the patient's tissue to reach the target nerves. Furthermore, having shorter elongate member lengths of the probes reduces the length of the probes extending outside the patient's tissue, which thereby can increase the stability of the placement of the cooled RF probes. When the length of the probe extending outside the patient's tissue is reduced, the moment arm of the probe and thereby possible torque applied to the treatment site by rotation or instability of the probes decreases.

In yet another embodiment, non-cooled radiofrequency ablation probes may be tethered for treatment of the knee. Such an embodiment can include an identical system as the cooled RF probe assembly <NUM> but does not include the cooling fluid tubing <NUM>. This embodiment can include a Y- or T-shaped electrical cable <NUM> for connecting two radiofrequency ablation probes to a single electrical source through a circular connector <NUM>.

Claim 1:
A cooled radiofrequency ablation probe assembly (<NUM>) comprising:
at least
a first cooled radiofrequency ablation probe (<NUM>) comprising an electrically and thermally-conductive energy delivery device (<NUM>), and a second cooled radiofrequency ablation probe (<NUM>) comprising a second electrically and thermally-conductive energy delivery device (<NUM>);
cooling fluid tubing (<NUM>, <NUM>, <NUM>) for supplying the at least two cooled radiofrequency ablation probes (<NUM>, <NUM>) with cooling fluid, the cooling fluid tubing comprising a connecting tubing portion (<NUM>) extending between the first cooled radiofrequency ablation probe (<NUM>) and the second cooled radiofrequency ablation probe (<NUM>) such that the first cooled radiofrequency ablation probe and the second cooled radiofrequency ablation probe are spaced apart by the connecting tubing portion, the connecting tubing portion (<NUM>) ranging from <NUM> to <NUM> in length to allow heat captured by the cooling fluid in the first radiofrequency ablation probe to dissipate into the atmosphere prior to the cooling fluid entering the second radiofrequency ablation probe; and
an electrical cable (<NUM>, <NUM>, <NUM>, <NUM>) for supplying the first cooled radiofrequency ablation probe (<NUM>) and the second cooled radiofrequency ablation probe (<NUM>) with electrical energy,
wherein the first cooled radiofrequency ablation probe and the second cooled radiofrequency ablation probe are connected to the cooling fluid tubing in series.