GB2460421A

GB2460421A - Surgical electrode which is deployed from a cannula at an angle

Info

Publication number: GB2460421A
Application number: GB0809658A
Authority: GB
Inventors: Nigel Huw Kellow
Original assignee: Individual
Current assignee: Individual
Priority date: 2008-05-28
Filing date: 2008-05-28
Publication date: 2009-12-02
Also published as: GB0809658D0

Abstract

An apparatus includes a hollow needle, such as a cannula 109 having proximal and distal ends and having an aperture 119 formed therein, and an elongate electrode 110 arranged for insertion into the needle to exit at the distal end, and means for deploying the electrode along a path that is at an angle to the longitudinal axis of the needle. In a first invention the electrode is made from a memory shape material and the electrode is shaped towards its distal end. Preferably the electrode is made from nitinol. In a second invention the needle includes a profiled guide member (213, 214, Figs 8-10) at the tip (219) portion of the distal end, preferably having a concave surface. A plurality of electrodes may be deployed from the needle, facilitated by guide members or lumens within the needle. The needle may be electrically insulated.

Description

I

SURGICAL APPARATUS FOR USE IN RADIOFREQUENCY ABLATION

TREATMENTS

The present invention relates to surgical apparatus for use in radiofrequency ablation or lesioning treatments, in particular, but not limited to, treatments for relieving back pain, and a method of performing radiofrequency ablation.

The spine is made up of three sections: cervical, thoracic and lumbar, and comprises 24 vertebrae. The vertebrae are mounted on top of each other to form the spinal column.

The vertebrae each include bony protrusions that meet together. Where these protrusions meet so called facet joints are formed. Facet joints allow bending of the spine in the forward and rearward directions, as well as rotation of the spine. The facet *:::* joints are connected to the spinal cord by medial branch nerves. When the facet joints are diseased or worn, these nerves carry pain signals to the spinal cord and then to the S...

brain where the pain is registered. This can cause significant discomfort to a person so : afflicted, and in some cases the pain can be debilitating. *.*

Figure 1 shows two vertebrae I and the facet joints 3 formed between them. The vertebrae 1 each have protrusions that extend substantially horizontally therefrom, these * are known as transverse processes 5. The medial branch nerves 7 run across the transverse processes 5 this is shown diagrammatically in Figures 1 and 2, wherein Figure 2 represents a cross section of one of the transverse processes 5 along line A-A.

When a person has chronic lower back pain initial exploratory procedures are undertaken such as intra-articular injections or medial branch blocks. If the person responds favourably to these procedures it is an indication that a permanent treatment such as radiofrequency ablation or radiofrequency lesioning, these terms are used interchangeably and from hereon in will be referred to as radiofrequency ablation, is suitable to treat the condition. Radiofrequency ablation is a treatment whereby the medial branch nerves that are sending pain signals to the spinal colunm are permanently destroyed by heating the nerve tissue to a temperature above 60°C, wherein proteins in the tissue denature to form a lesion. Destruction of the medial branch nerve 7 prevents the pain signals from being transmitted to the central nervous system thereby relieving pain.

Radiofrequency ablation processes are generally performed under local anaesthetic. A hollow needle, known as a cannula 9, is inserted into a patient's back onto the transverse process 5 where the damaged medial branch nerve 7 is located (see Figure 3).

To find the correct position the surgeon uses X-ray imaging equipment. The surgeon then inserts an elongate electrode into the cavity of the cannula, the remote end of which protrudes a few millimetres from an opening aligned with the axis of the cannula so that it is positioned adjacent the medial branch. The proximal end of the electrode is connected to a radiofrequency generator. The position is then checked by a series of electrical tests to ensure that the correct nerve has been located. A second electrode is *** attached to the patient's body to complete the circuit. *�.* * . S...

A lesion 11 is then formed by heating the active electrode to around 80°C for a period * : . . of between 60 and 120 seconds (see Figure 4). This destroys the medial branch nerve 7 * 15 in the process thereby preventing the transmission of pain signals to the rest of the *: : nervous system. If several nerves have to be treated, the process is repeated for each nerve. *.... S *

A similar process is used to treat medial branch nerves in the cervical spine, which lie across articular pillars.

A drawback with the current treatment is that the lesion 11 formed by the active electrode is created about the tip 13 of the cannula and therefore extends a significant way into the muscle that surrounds the transverse process 5 or articular pillar. This can cause significant post operation pain to the patient, which may last for several weeks.

Also, the lesion 11 that is produced is not optimally shaped for coagulating the medial branch nerve 7, thus there is a possibility that the process will have to be repeated.

Furthermore, it is very difficult to position the cannula such that when the active electrode is deployed it is in the correct place to coagulate the medial branch nerve 7.

This is because of the difficulties in using X-ray location equipment and also because the position of the medial nerve may not be located exactly at the nominal medial branch position, for example it is not uncommon for the medial branch nerves to be displaced from the nominal position by around 5mm. Thus positioning the cannula 9 correctly can be very time consuming.

Accordingly the invention seeks to mitigate at least one of the above-mentioned problems by providing an alternative surgical apparatus for performing radiofrequency ablation treatments and a method of performing radiofrequency ablation.

According to one aspect of the invention there is provided surgical apparatus for use in radiofrequency ablation treatments, including a hollow needle-like device having a proximal end and a distal end, said distal end being arranged for insertion into a patient's back and having an aperture formed therein, an elongate electrode arranged for * * insertion into the hollow needle-like device at the proximal end such that it can be moved there through to exit at the distal end via the aperture, and means for deploying S...

the electrode from the needle-like device along a path that is directed away from the longitudinal axis of the needle-like device. ***

* * 15 In conventional devices the electrode protrudes out of the needle-like device by a few millimetres and lies along the longitudinal axis of the device. The invention ensures that **ö * the electrode is positioned such that it lies along the transverse process in the lumbar spine (articular pillar in the cervical spine) on which the medial branch to be treated is situated in a manner that it extends substantially transversely across the medial branch.

When the lesion is formed by exciting the electrode with a radiofrequency generator it extends along the electrode and hence across the transverse process (articular pillar) and not into the muscle surrounding the transverse process (articular pillar). Also, the shape and position of the lesion is such that there is a much improved chance of successfully coagulating the medial branch thereby reducing the possibility of needing to repeat the process. Movement away from the longitudinal axis results in there being a greater extent of electrode deployed from the needle-like device. This makes it easier to position the needle-like device initially since the initial position is not as critical when compared with the prior art devices which only deploy a few millimetres of electrode in the longitudinal direction. This significantly speeds up the positioning process.

Advantageously the means for deploying the electrode device causes the electrode to be deployed along a curved path that flares outwards from the distal end of the needle-like device. This provides the most satisfactory deployment.

Advantageously the means for deploying the electrode device is arranged to deploy at least a portion of the electrode at an angle of greater than 30 degrees to the longitudinal axis of the needle-like device, preferably at an angle in the range 50 to 90 degrees to the longitudinal axis of the needle-like device, more preferably within the range 70 to 90 degrees and more preferably still in the range 80 to 90 degrees. Advantageously the arrangement can be such that at least a portion of the electrode is deployed substantially perpendicular to the longitudinal axis of the needle-like device.

Advantageously the electrode can be made from a material having a shape memory property and the electrode is shaped towards the distal end such that when it exits the aperture it deploys from the needle-like device along the path that is directed away from the longitudinal axis of the needle-like device, for example the electrode can be made from nitinol, which has a shape memory property and is also a conductor of electrical * signals. Advantageously the shape memory property can enable the electrode to deploy along the paths described above. The shape memory property enables the electrode to *.*..

* be straightened such that it can move through the needle-like device, however it retains its formation, for example a curvature, such that when deployed it reverts back to its curved shape. Preferably the electrode is shaped such that it curves through an angle of around 70 to 90 degrees. The electrode can have resiliency which causes it to deploy away from the longitudinal axis of the needle-like device when exiting the needle-like device.

Advantageously the needle-like device can include means for deploying the electrode from the aperture along a path that is directed away from the longitudinal axis of the needle-like device. Advantageously the needle-like device includes a profiled guide member adjacent the aperture arranged to direct the electrode along a path that is inclined to the longitudinal axis of the needle-like, device by at least 30 degrees. The profiled guide member can include a concave surface. The profiled guide member can comprise a tip portion of the distal end of the needle-like device.

Advantageously the surgical apparatus can include a plurality of electrodes for deployment via the needle-like device. The plurality of electrodes are arranged to deploy in different directions. For embodiments including two electrodes, preferably the electrodes are arranged to deploy in substantially opposite diametric directions. For embodiments wherein the electrodes are made from a shape memory material the electrodes are positioned in the hollow needle-like device with their orientations properly aligned in order to achieve the desired deployment. Advantageously the needle-like device can include guide members to help achieve this.

**** * The needle-like device can include a first guide member for guiding the deployment of a first electrode and second guide member for guiding the deployment of a second **.* electrode. Preferably the first and second guide members include concave surfaces that * ,,* are arranged in substantially diametrically opposite directions. Advantageously the * : 15 guide surfaces are arranged to deploy the electrodes substantially radially. Preferably * the guide surfaces form part of the needle-like device tip.

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* Advantageously the hollow needle-like device can include a plurality of lumens.

Preferably each lumen is arranged to receive an electrode.

Advantageously the hollow needle-like device can be electrically insulated along substantially its entire length. This prevents the lesion from forming in the longitudinal direction of the needle-like device and thereby extending into the surrounding muscle tissue.

Typically the needle-like device includes a substantially cylindrical portion having a diameter in the range of less than 2mm, and preferably in the range 0.5mm to 1.5mm.

Usually the diameter is around 1mm.

According to another aspect of the invention there is provided a method for treating a human or animal body by radiofrequency ablation, including inserting a hollow needle-like device into the body and guiding a distal end of the hollow needle-like device to a position adjacent a nerve to be coagulated, feeding an electrode through the hollow needle-like device and deploying the electrode into the body via an aperture in the distal end of the needle-like device such that it is deploys along a path that deviates away from the longitudinal axis of the cannula, and heating the nerve to be treated by exciting the electrode with signals from a radiofrequency generator until a lesion is formed.

Advantageously the method may include deploying the electrode along a curved path that flares outwards from the distal end of the needle-like device.

Advantageously the method may include deploying the electrode such that at least a portion of the electrode is deployed at an angle of greater than 30 degrees to the *:*: longitudinal axis of the needle-like device, preferably is deployed at an angle in the *. . range 60 to 90 degrees to the longitudinal axis of the needle-like device, more preferably within the range 70 to 90 degrees and more preferably still in the range 80 to degrees.

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Advantageously the method may include deploying the electrode substantially S perpendicularly to the longitudinal axis of the needle-like device. * I

Advantageously the method may include rotating the needle like device about its longitudinal axis in order to select the most appropriate direction for deployment of the electrode. This ensures that as the electrode is deployed it moves towards the nerve being treated rather than in some other direction.

Advantageously the method may include treating a spinal area of the body, in particular treating tissue associated with a facet joint.

Advantageously the method may include targeting a medial branch nerve for treatment.

Advantageously the method may include deploying the electrode such that it lies across a portion of a transverse process or articular pillar.

Advantageously the method may include deploying the electrode such that it extends from the needle-like device by at least 10mm, and preferably extends from the needle-like device in the range 15 to 40nim. This ensures that there is sufficient electrode deployed to lie across the medial nerve substantially transversely.

Advantageously the method may include deploying the electrode such that it lies substantially transversely to the nerve being treated.

Advantageously the method may include deploying a plurality of electrodes from the needle-like device. Advantageously the method may include deploying a first electrode in a first direction and deploying a second electrode in a direction that is substantially diametrically opposite to the first direction. * *a * 0 *

Advantageously the method may include delivering a fluid to the area being treated via S...

the hollow needle-like device. For example, the fluid may include a treatment for * * * .: . numbing the area or for applying a medic ament such as a steroid.

IS

Advantageously the method may include pre-loading the electrode into the hollow * 15 needle-like device prior to inserting it into the patient's body. S.SSS * *

Advantageously the method may include using apparatus according to any of the configurations described herein.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a diagrammatic view of two lumbar spine vertebrae; Figure 2 is a cross-sectional diagrammatic view of a transverse processes from one of the vertebrae shown in Figure 1 with a medial branch nerve located thereon; Figures 3 and 4 are diagrammatic views of prior art radiofrequency ablation surgical apparatus for forming lesions at the medial branch nerve; Figure 5 is a diagrammatic view of part of a cannula and an electrode according to a first embodiment of the invention; Figure 6 is a diagrammatic view of the equipment shown in Figure 5 with a representation of a lesion formed across the medial branch nerve; Figure 7 shows a diagrammatic front plan view of a cannula, an electrode and a radiofrequency generator according to a second embodiment of the invention; * ** Figure 8 is a plan view of part of the cannula shown in Figure 7; * * S * .s *5** Figure 9 is a side view of the part of the cannula shown in Figure 8; b * S * ** p. Figure 10 is a sectional side view of the part of the caimula shown in figure 9 together with an electrode located therein, said electrode being deployed across a * medial branch nerve located on a transverse process at a distal end and connected * : * to the radiofrequency generator at a proximal end; and Figure 11 shows a side view of the part of the cannula shown in Figure 10 with a representation of a lesion formed across the medial branch nerve; and Figure 12 is a flow diagram of a surgical procedure for a radiofrequency ablation treatment of a medial branch nerve using surgical apparatus according to the invention.

Figures 5 and 6 show parts of a first embodiment of the invention, which includes a cannula 109, an electrode 110 for delivering radiofrequency energy to bodily tissue and a radiofrequency generator 115.

The cannula 109 is a hollow needle-like device having a substantially cylindrical portion 119 that has a diameter in the range of 0.5mm to 2mm and is typically around 1mm in diameter. The cannula 109 is electrically insulated along the full length of the part of the cannula 109 that is inserted into a patient's body. The cannula 109 can be made of a non-conducting material or alternatively can be made from a conducting material such as stainless steel and can have a non-conductive coating 117 such as a plastics material or Teflon applied to its outer surface. The cannula 109 includes an aperture 119 located at its distal end that is substantially aligned with the longitudinal axis B' of the cannula.

At its proximal end, the cannula 109 includes a formation (not shown) for receiving a standard size syringe so that fluids, such as liquid medicaments can be administered to the treatment area via the cannula 109, for example compositions that have a numbing S. effect or steroids.

:.. The electrode 110 is an elongate wire like member that is arranged to pass through the cannula 109 and to be deployed into the patient's body via the aperture 119. The * electrode is made from an electrically conducting material that has a shape memory property such as nitinol. The distal end of the electrode 1 lOa is shaped into a curve. The S.....

arrangement is such that the electrode 110 can be straightened to enable it to be fed through the cannula 109 into the patient's body thereby preloading the curved part. As the distal end exits the aperture 117 the shape memory property causes it to return to its curved form, which causes the distal end 1 lOa to deploy along a curved path that deviates away from the longitudinal axis B' of the cannula such that it moves across the transverse process 5 and the medial branch 7 transversely. Effectively the distal end 11 Oa of the electrode is deployed substantially perpendicularly to the longitudinal axis B', however as can be seen in Figure 5, close to the aperture 119 there is a curved part of the electrode 121 wherein the angle a of the inclination of the distal end of the electrode to the longitudinal axis gradually increases as it curves away therefrom, from around 30 degrees to around 90 degrees. Thus the distal end I lOa effectively flares outwards from the cannula 109.

The proximal end 11 Ob is connected to the radiofrequency generator 115. This device is well known in the art and therefore will not be further described herein.

During a radiofrequency ablation treatment the surgeon inserts the cannula 109 into the patient's body and guides it to the medial branch 7 to be treated, typically using an X-ray imaging machine. The distal end 110 of the electrode typically deploys around 15 to 40mm from the cannula 109. Since the electrode 110 deploys significantly further than the electrode used in the prior art, it is able to lie across the transverse process 5 in the lumbar spine (and alongside the articular pillar in the cervical spine) and also to lie transversely across the medial branch 7. This has the effect that the shape of the lesion 111 formed extends across the transverse process 5 instead of into the muscle tissue surrounding the transverse process and more reliably denervates the medial branch 7.

This significantly reduces the post operation pain experienced by the patient and *::: reduces the time it takes to make a full recovery. It also allows for greater anatomical : * variation in the actual position of the medial branch 7 when compared with a nominal expected location, since the larger extent of deployment ensures that the electrode *I* overlies many of the actual positions that the medial branch 7 can be located. Thus : denervation can take place regardless of the actual position of the nerve 7.

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* A summary of the steps in a radiofrequency ablation treatment according to the invention is shown in Figure 12, which includes: inserting the cannula into the patient's back 123, guiding the cannula towards the target nerve using imaging equipment 125, connecting the electrode to the radiofrequency generator 127, inserting the electrode into the cannula 129, adjusting the rotational orientation of the cannula to ensure the cannula deploys in the correct direction 131, deploying the electrode from the cannula such that it lies transversely across the medial branch to be treated 133, and delivering energy to the electrode from the radio frequency generator to denervate the medial branch 7 and thereby form a lesion 135.

As an alternative, the electrode can be previously loaded into the cannula 109 and can be withdrawn into the cannula 109 just before use. For example, it can be of the Stimject type to avoid having to remove the electrode.

A second embodiment of the invention is shown in Figures 7 to 11. The second embodiment includes a cannula 209, an electrode 210 for delivering radiofrequency energy to bodily tissue and a radiofrequency generator 215.

The caimula 209 is similar to the caunula 109 of the first embodiment except that it includes a blunt tip 213. The cannula 209 is not insulated around the tip 213. The tip is located adjacent aperture 219 and includes a profiled, such as inclined or curved, surface 214 that is arranged to deflect the electrode 210 as it is deployed such that it moves away from the longitudinal axis B' of the cannula and lies transversely across the medial branch 7. Preferably the profiled surface is concave and is arranged to deploy the electrode 210 in a direction that is substantially perpendicular to the longitudinal axis B' of the cannula. However, as can be seen in Figure 10, close to the aperture 219 there is a curved part of the electrode 221 wherein the angle a of the inclination of the * ** distal end of the electrode to the longitudinal axis gradually increases as it curves away therefrom, from around 30 degrees to around 90 degrees. Thus the distal end 21 Oa S...

effectively flares outwards from the cannula 209. * S. * . S S...

*.* The electrode 210 can be similar to that in the first embodiment. Alternatively, the electrode can be made from a material that does not have a shape memory property but rather any suitable flexible electrical conducting material that can be guided by the *: curved surface 14 to lie across the medial branch 7.

The lesion 211 is formed across the transverse process 5 (or articular pillar) in a similar manner to the first embodiment described above.

It will be appreciated by the skilled person that the above embodiments can be modified in ways that are still intended to fall within the scope of the invention, for example in a variation to the first embodiment described above, the cannula 109 can be arranged to accommodate two or more electrodes 110 that can be arranged to deploy in different directions, for example so that they fan outwards. For embodiments having two electrodes 110, the electrodes 110 can be arranged to deploy in opposite directions.

In a variation to the second embodiment described above, the cannula 209 can be arranged to accommodate two or more electrodes 210, which can be arranged to deploy in different directions, for example so that they fan outwards by providing additional profiled guide surfaces 214. For embodiments having two electrodes 210, the electrodes 210 can be arranged to deploy in opposite directions by arranging the guide surfaces 214 in opposite directions.

The cannula 109,209 can include a sharp tip. * .* * * * * ** S... * S S... * ** * . S *... * 5. * S. * * S* * *5

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Claims

CLAIMS1. Surgical apparatus for use in radiofrequency ablation treatments, including a hollow needle-like device having a proximal end and a distal end, said distal end being arranged for insertion into a patient's back and having an aperture formed therein, an elongate electrode arranged for insertion into the hollow needle-like device at the proximal end such that it can be moved there through to exit at the distal end via the aperture, and means for deploying the electrode from the needle-like device along a path that is directed away from the longitudinal axis of the needle-like device.
2. Surgical apparatus according to claim 1, wherein the means for deploying the electrode device is arranged to deploy the electrode along a curved path that *: flares outwards from the distal end of the needle-like device. S...
3. Surgical apparatus according to claim 1 or 2, wherein the means for deploying : *"* the electrode device is arranged to deploy at least a portion of the electrode at an :. angle of greater than 30 degrees to the longitudinal axis of the needle-like device, preferably at an angle in the range 50 to 90 degrees to the longitudinal axis of the needle-like device, more preferably within the range 70 to 90 degrees * : * and more preferably still in the range 80 to 90 degrees.
4. Surgical apparatus according to any one of the preceding claims, wherein the electrode is made from a material having a shape memory property and the electrode is shaped towards the distal end such that when it exits the aperture it deploys from the needle-like device along the path that is directed away from the longitudinal axis of the needle-like device.
5. Surgical apparatus according to the preceding claims, wherein the electrode is treated at the distal end such that it is pre-loaded to move along the path that is directed away from the longitudinal axis of the needle-like device.
6. Surgical apparatus according to claim 4 or 5, wherein the electrode is made from nitinol.
7. Surgical apparatus according to any one of the preceding claims, wherein the needle-like device includes means for deploying the electrode from the aperture along a path that is directed away from the longitudinal axis of the needle-like device.
8. Surgical apparatus according to claim 7, wherein the means for deploying the electrode from the aperture includes a profiled guide member adjacent the aperture arranged to direct the electrode along a path that is inclined to the longitudinal axis of the needle-like device by at least 30 degrees.
9. Surgical apparatus according to claim 8, wherein the profiled guide member * includes a concave surface. S... * . S...: **
10. Surgical apparatus according to any one of claims 7 to 9, wherein the profiled S...

* guide member comprises a tip portion of the distal end of the needle-like device.

*
11. Surgical apparatus according to any one of the preceding claims, including a * : * plurality of electrodes for deployment from the needle-like device.
12. Surgical apparatus according to claim 11, wherein the plurality of electrodes are arranged to deploy in different directions.
13. Surgical apparatus according to claim 11 or 12, including a first guide member for guiding the deployment of a first electrode and second guide member for guiding the deployment of a second electrode.
14. Surgical apparatus according to claim 13, wherein the first and second guide members include concave surfaces that are arranged in substantially diametrically opposite directions.
15. Surgical apparatus according to any one of the preceding claims, wherein the hollow needle-like device includes a plurality of lumens.
16. Surgical apparatus according to any one of the preceding claims, wherein the hollow needle-like device is electrically insulated along substantially its entire length.
17. Surgical apparatus according to any one of the proceeding claims, wherein the needle-like device includes a substantially cylindrical portion having a diameter in the range of less than 2mm, and preferably in the range 0.5mm tol.5mm.Typically the diameter is around 1mm. * ** *. * * ** **** * . S... * *. * . S *... * *S S. * * S* * S.S..... S *