# Patent

## Title
Neurological stimulation lead anchors and associated systems and methods

## Abstract

A spinal cord lead anchor comprising a longitudinally extending sleeve having an aperture sized and positioned to receive a spinal cord lead. A retainer is disposed around the sleeve and is operative to compress at least a portion of the sleeve against a spinal cord lead extending through the sleeve. A cover extends around the retainer and includes at least one opening formed through the cover to facilitate engaging the retainer with a tool.

## Background
CROSS REFERENCE TO RELATED APPLICATION
The present application claims priority to U.S. Provisional Application No. 61/840,982, filed Jun. 28, 2013, which is incorporated herein by reference in its entirety.


TECHNICAL FIELD
The present disclosure is directed generally to lead anchors for positioning and securing neurological stimulation system leads or other signal delivery elements. More specifically, the disclosure is directed to lead anchors for positioning and securing spinal cord stimulation and modulation leads.
BACKGROUND
Neurological stimulators have been developed to treat pain, movement disorders, functional disorders, spasticity, cancer, cardiac disorders, and various other medical conditions. Implantable neurological stimulation systems generally have an implantable signal generator and one or more leads that deliver electrical pulses to neurological or muscle tissue. For example, several neurological stimulation systems have cylindrical leads that include a lead body with a circular cross-sectional shape and one or more conductive rings (i.e., contacts) spaced apart from each other at the distal end of the lead body. The conductive rings operate as individual electrodes and, in many cases, the leads are implanted percutaneously through a large needle inserted into the epidural space, with or without the assistance of a stylet.
Once implanted, the signal generator applies electrical pulses to the electrodes, which in turn modify the function of the patient's nervous system, such as by altering the patient's responsiveness to sensory stimuli and/or altering the patient's motor-circuit output. In pain treatment, the signal generator applies electrical pulses to the electrodes, which in turn can mask or otherwise alter the patient's sensation of pain.
It is important to accurately position and anchor the leads in order to provide effective therapy. For example, in both traditional low frequency spinal cord stimulation (SCS) and high frequency spinal cord modulation therapy, one or more leads are positioned along a patient's spine to provide therapy to a specific vertebral area. Existing lead anchors can negatively impact lead performance and/or reliability when they allow the lead body to slide or otherwise change position relative to a treatment area. The movement of the lead body relative to the lead anchor can reduce the accuracy with which the stimulation is provided, thus limiting the effectiveness of the therapy. In some cases, the leads must be securely fixed but still be repositionable if a practitioner determines that a different position would provide more effective therapy. As a result, there exists a need for a lead retention mechanism, such as a lead anchor, that mitigates lead movement while providing the ability to subsequently reposition the lead.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a lead anchor according to a representative embodiment.
FIG. 2 is a cross sectional view of the lead anchor shown in FIG. 1 taken along line 2-2 of FIG. 1.
FIG. 3 is a cross sectional view of the lead anchor shown in FIGS. 1 and 2, illustrating a tool engaging the retainer.
FIG. 4 is a perspective view of representative circlip pliers.
FIG. 5 is a cross sectional view similar to that of FIG. 2 illustrating a spacer installed in the retainer.
FIG. 6A is a side view from the split end of a retainer illustrating another construction of a spacer.
FIG. 6B illustrates the retainer shown in FIG. 6A in a contracted state.
FIG. 7 is a perspective view of a lead anchor according to another representative embodiment.
FIG. 8 is a cross sectional view of the lead anchor shown in FIG. 7 taken along line 8-8.
FIG. 9 is a perspective view of a tubular retainer as shown in FIG. 8.



DETAILED DESCRIPTION
The present technology is directed generally to lead anchors and methods of anchoring a lead to a patient that mitigate lead movement while providing the ability to subsequently reposition the lead. In general, the lead anchors and methods are for use with neurological stimulation systems, such as spinal cord modulation systems. In particular embodiments, the lead anchor can include a retainer, such as a snap ring or circlip that releasably attaches a lead to a lead anchor. The lead anchor can in turn be attached to a patient with sutures. Specific details of several embodiments of the technology are described below with reference to representative anchors to provide a thorough understanding of these embodiments, but other embodiments can have other arrangements. Several details describing structures or processes that are well-known and often associated with lead anchors and associated devices but that may unnecessarily obscure some significant aspects of the disclosure are not set forth in the following description for purposes of clarity. Moreover, although the following disclosure sets forth several embodiments of different aspects of the technology, several other embodiments of the technology can have different configurations or different components than those described in this section. As such, the technology may have other embodiments with additional elements and/or without several of the elements described below with reference to FIGS. 1-9.
FIG. 1 illustrates a lead anchor 100 according to a representative embodiment of the present technology. The lead anchor 100 releasably carries a lead 130 (e.g., an electrical stimulation or modulation lead) and anchors the lead 130 relative to a patient's tissue. Accordingly, the lead anchor 100 can include a longitudinally extending anchor body 102 having a longitudinally extending aperture 103 that receives the lead 130. One or more anchor tabs 108 extend laterally from the anchor body 102 e.g., on opposite sides. Each anchor tab 108 can include an aperture 110 or other feature to facilitate attaching the lead anchor 100 to a patient's tissue. The lead anchor 100 can include an associated groove 112 that is aligned with a corresponding aperture 110. The grooves 112 act to keep sutures, which are used to attach the anchor 100 to the patient, properly aligned with the anchor tabs 108 and the apertures 110. Thus, the lead anchor 100 may be attached to a patient by suturing through the apertures 110 with the suture threads captured in the grooves 112. The lead anchor 100 can further include openings 114 that allow a user to attach and release the anchor 100 and the lead 130, as described further with reference to FIG. 3.
FIG. 2 illustrates a cross-sectional view of an embodiment of the anchor 100 shown in FIG. 1. The anchor body 102 includes a sleeve 104 in which the longitudinally extending aperture 103 is positioned. The aperture 103 is sized and configured to receive the lead 130 therethrough. A retainer 120 is disposed around the sleeve 104 and is operable to compress or constrict at least a portion of the sleeve 104 against the lead 130 extending through the sleeve. The lead 130 is accordingly retained in position relative to the anchor 100 by friction developed between the sleeve 104 and lead 130 due to the compression force exerted by the retainer 120. In some embodiments, the retainer 120 can extend circumferentially around the sleeve 104 by an amount greater than 180 degrees. In other embodiments, the retainer 120 extends around the sleeve 104 by an amount that is slightly less than 360 degrees (as shown in FIG. 2) or by an amount greater than 360 degrees. In general, the circumferential extent of the retainer 120 is sufficient to capture and/or compress the lead 130 in a generally uniform manner. The sleeve 104 is sized to provide clearance between the inner surface of the aperture 103 and the outer surface of the lead 130 such that the lead 130 may be moved into position relative to the anchor 100 as long as the retainer 120 is maintained in an expanded state (described further below with reference to FIG. 5). The clearance between the sleeve 104 and lead 130 may be, for example and without limitation, in the range of from about 0.001 inch to about 0.002 inch.
In the illustrated embodiment, the retainer 120 has the general form of a circlip (sometimes referred to as a snap ring) with a pair of end portions 124 spaced apart by a gap 122. Each end portion 124 includes an aperture 126 to facilitate actuation with a suitable tool. In this embodiment, the retainer 120 is normally in a contracted state in which the sleeve 104 is compressed against the lead 130. Thus, to insert the lead 130 into the aperture 103, or move the lead 130 within the aperture 103, the retainer 120 is actuated (e.g., elastically deformed) to an expanded state to release the compressive force on the sleeve 104.
FIG. 3 illustrates a representative tool 140 having prongs 142 positioned to expand the retainer 120, as indicated by arrows E. In this embodiment, the retainer 120 is comprised of a material providing a resilient or spring-like behavior. Accordingly, the retainer 120 may be comprised of a metal, such as for example and without limitation, titanium, stainless steel, spring steel, or the like. The retainer 120 may also be formed from resilient plastics, such as, for example and without limitation, ABS, Nylon, Delrin, UHMW polyethylene, and the like.
The anchor body 102 can also include a cover 106 extending around the retainer 120 to prevent or inhibit the retainer from contacting the patient's tissue. The sleeve 104 and cover 106 can be separately manufactured and then assembled together, for example. In this embodiment, the sleeve 104 and cover 106 are formed from a flexible material, such as a biocompatible material. An example of a suitable flexible biocompatible material is silicone rubber. As shown in FIG. 3, the cover 106 includes a pair of openings 114 to allow the tool 140 to be inserted therethrough to engage the apertures 126 of retainer 120. The openings 114 may be in the form of slots (as shown in FIG. 1) extending longitudinally with respect to the anchor body 102. The flexibility of the cover material allows the tool to actuate the retainer 120 without interference from the cover 106. The openings 114 may in other embodiments extend transverse to the anchor body. In still further embodiments, the cover 106 can include a single opening through which the tool 140 is inserted.
It should be appreciated that while certain embodiments disclosed herein are described in the context of a retainer having a normally contracted state, the retainers can have other configurations in other embodiments. For example, in some embodiments the retainer can have a normally expanded state and may be actively contracted to secure the lead 130 in the anchor. Such a retainer may include a latch device (e.g., interlocking teeth) capable of maintaining the retainer in the contracted state. Once the lead 130 is located in the desired position within the anchor, the normally expanded retainer can be compressed (e.g., with a suitable tool) to the contracted state in which the sleeve 104 is compressed against the lead 130. Once the normally expanded retainer is compressed to the contracted state, the latch device maintains the retainer in the contracted state.
FIG. 4 illustrates a representative embodiment of the tool 140 for actuating the retainer 120 shown in FIG. 3. In this embodiment, the tool 140 is a pair of external circlip or snap ring pliers having 90 degree prongs 142. The pliers 140 include a pair of handles 144 which are pivoted at a pivot joint 146 and maintained in a normally closed position by a spring 148. In this embodiment, the pivot joint 146 is arranged such that when the handles 144 are squeezed (moved toward each other), the prongs 142 move away from each other thereby expanding a contracted circlip. The tool 140 may also be in the form of a hemostat with the tips bent 90 degrees relative to the opening of the hemostat's jaws. In addition, the tool 140 may be locked open or locked closed.
FIG. 5 shows the cross section of a lead anchor 100 with the addition of a spacer 150 disposed in the gap 122 between the ends of the retainer 120. Accordingly, the retainer 120 is maintained in an expanded state so that the lead 130 may be inserted into the sleeve 104 without the use of a tool (e.g., the tool 140 described above). Once the lead 130 is positioned within the sleeve 104 at the desired location, a suitable tool is used to compress the retainer 120 thereby sacrificing the spacer 150 and allowing the retainer 120 to contract and compress the sleeve 104 against lead 130. The tool can have a plier arrangement similar to that shown in FIG. 4, but can be configured to compress the circlip to a contracted state when the handles are squeezed together. This type of tool is often referred to as internal circlip or snap ring pliers. In operation, the spacer 150 is broken, deformed or otherwise sacrificed in the process of contracting retainer 120. Accordingly, the spacer 150 may be a frangible material or have a frangible construction. In particular embodiments, the spacer 150 may be a brittle material and easily broken into pieces such that it is out of the way. It should be appreciated that the broken pieces of the spacer 150 are completely encased and captured by the sleeve 104 and/or the cover 106. In other embodiments, the spacer 150 can deform such as by bending. In any of these embodiments, if the lead 130 needs to be repositioned with respect to the anchor 100, a tool may be inserted into slots 114 to engage the retainer apertures 126 as described above in order to temporarily expand the retainer 120 such that the lead 130 may be repositioned.
FIGS. 6A and 6B illustrate a retainer 220 configured in accordance with another embodiment of the present technology. FIGS. 6A and 6B are views of the retainer 220 as viewed from a gap 222 between the ends of the retainer. The retainer 220 includes a latch arm 230 which keeps the retainer 220 in an expanded state, as shown in FIG. 6A. The latch arm 230 is carried by one end of the retainer 220 and includes a latch pawl 232 that engages the other end of retainer 220, thereby keeping the retainer 220 in its expanded state. In operation, a user engages the apertures 226 with a suitable tool, such as a pair of internal circlip or snap ring pliers, and urges the ends of the retainer toward each other, thereby contracting the retaining ring 220 while at the same time causing the pawl 232 to disengage from the end of the retaining ring 220, as shown in FIG. 6B. In this case, the retainer 220 is in a normally contracted state except when it is kept in an expanded state by the latch arm 230. Thus, once the pawl 232 is disengaged, the retainer 220 remains contracted in order to squeeze the lead 130 within the associated sleeve 104 (see, e.g., FIG. 5). If the lead 130 is to be repositioned with respect to the anchor 100, a pair of external circlip pliers, such as those shown in FIG. 4, can be used to expand the retainer 220 thereby allowing the pawl 232 to re-engage the end of retainer 220, again maintaining it in an expanded state.
FIG. 7 illustrates a lead anchor 300 according to another representative embodiment of the present technology. The lead anchor 300 releasably carries a lead 330 and anchors the lead 330 relative to a patient's tissue. Accordingly, the lead anchor 300 can include a longitudinally extending anchor body 302 having a longitudinally extending aperture 303 that receives the lead 330. Similar to the lead anchor 100 described above, one or more anchor tabs 308 can extend laterally from the anchor body 302 to facilitate attaching the lead anchor 300 to a patient. The lead anchor 300 can further include flat sides 314 that allow a user to attach and release the anchor 300 to the lead 330, as described further with reference to FIGS. 8 and 9.
FIG. 8 illustrates a cross-sectional view of the embodiment of the lead anchor 300 shown in FIG. 7. The anchor body 302 includes a sleeve 304 in which the longitudinally extending aperture 303 is positioned. The aperture 303 is sized and configured to receive the lead 330 therethrough. A retainer 320 is disposed around sleeve 304 and is operable to compress or constrict at least a portion of the sleeve 304 against the lead 330 extending through the sleeve. The lead 330 is accordingly retained in position relative to the anchor 300 by friction developed between the sleeve 304 and lead 330 due to the compression force exerted by the retainer 320. The sleeve 304 is sized to provide clearance between the inner surface of the aperture 303 and the outer surface of the lead 330 such that the lead 330 may be moved into position relative to the anchor 300 as long as the retainer 320 is maintained in an expanded state indicated in dashed lines in FIG. 8 by reference number 320′.
As illustrated in FIGS. 8 and 9, the retainer 320 has the general form of an elongate tube having an oval or elliptical cross-section. In this embodiment, the retainer 320 is normally in a contracted state (e.g., with an elliptical cross-section) in which the sleeve 304 is compressed against the lead 330 across the minor axis b of the retainer 320. Thus, to insert the lead 330 into the aperture 303, or move the lead 330 within the aperture 303, the retainer 320 is actuated (e.g., elastically deformed) to an expanded state as indicated in dashed lines by reference number 320′ (e.g., to a circular cross-sectional shape) to release the compressive force on the sleeve 304.
The retainer 320 is actuated by squeezing the major axis a of the retainer 320 with a suitable tool, such as a hemostat, as indicated by arrows S. Squeezing the major axis a of the retainer 320 causes the cross-section of the retainer 320 to deform and move toward a more circular shape as indicated by reference number 320′. The flat sides 314 are formed in the anchor body 302 at the location of the retainer's major axis a in order to indicate where to squeeze the anchor body 302 to actuate the retainer 320. In other embodiments, the anchor body 302 can include grooves or color markings to indicated the proper location to squeeze the anchor body 302 to actuate the retainer 320.
In another embodiment, the retainer can include a material (e.g., nickel-titanium alloy) that has a circular cross-section at room temperature but changes to an oval or elliptical cross-section at a temperature between room temperature and body temperature (e.g., 98.6° F.). Accordingly, the lead anchor can be freely repositioned with respect to the lead prior to implanting the lead into a patient. Once the lead and lead anchor are implanted, the patient's body temperature causes the retainer to move to a contracted state, thereby retaining the lead in position with respect to the lead anchor. The lead anchor can be repositioned while implanted in the patient's body by actuating the retainer as explained above with respect to FIGS. 8 and 9.
The present technology also includes methods of anchoring a lead to a patient using a lead anchor. A representative method comprises inserting a lead into a sleeve; maintaining a retainer disposed around the sleeve in an expanded state; manually moving the retainer to a contracted state; and maintaining the retainer in the contracted state around the sleeve, thereby squeezing the sleeve against the lead. The method can further comprise moving the retainer to the expanded state and repositioning the lead with respect to the sleeve. The method can still further comprise attaching the sleeve to a patient with sutures.
Several embodiments described herein offer advantages over traditional lead anchors. For example, certain embodiments include a retainer that retains the lead in position with fewer parts than traditional lead anchors have. Accordingly, the disclosed lead anchors can be smaller than traditional lead anchors which results in a device that is more comfortable for the patient. With fewer parts, the lead anchor can be more economical to produce when compared to traditional lead anchors having additional parts. The disclosed lead anchors are also easy to use. With one movement of a suitable tool, the retainer may be contracted or expanded in order to position, reposition, or secure a lead within the lead anchor sleeve. Certain embodiments of the lead anchor include a cover. The cover provides an advantage over traditional lead anchors in that the cover encloses the retainer and protects the patient's tissue from contacting the retainer. Other lead anchors have exposed components that can irritate tissue.
The present technology includes lead anchors for use with neurological stimulation systems, such as spinal cord modulation systems. In a representative embodiment, the lead anchor comprises a longitudinally extending sleeve having an aperture sized and positioned to receive a lead. A retainer is disposed around the sleeve and is operative to compress at least a portion of the sleeve against a portion of the lead that extends through the sleeve. The lead anchor may further comprise a cover extending around the retainer.
In another representative embodiment, a spinal cord lead anchor comprises a longitudinally extending sleeve having an aperture sized and positioned to receive a spinal cord lead. A retainer is disposed around the sleeve and is operative to compress at least a portion of the sleeve against a spinal cord lead extending through the aperture. A cover extends over the retainer and includes at least one opening formed through the cover to facilitate engaging the retainer with a tool. The lead anchor also includes a pair of anchor tabs to facilitate attaching the lead anchor to a patient.
In one aspect of the technology disclosed herein, the cover can include a pair of longitudinally extending slots, to facilitate engaging the retainer with a tool. In another aspect of the disclosed technology, the retainer is a circlip having a pair of apertures engageable with a tool. In yet another aspect of the disclosed technology, the anchor can further comprise a spacer disposed between ends of the circlip and operative to maintain the circlip in an expanded state until the spacer is compressed. The spacer can be, for example, frangible or deformable.
In further aspects of the disclosed technology, the anchor tabs extend from the cover and each includes an anchor aperture. The cover can also include two grooves, each aligned with one of the anchor tabs. In some embodiments, the retainer is a normally contracted circlip having a pair of apertures engageable with a tool. In other embodiments, the retainer is normally expanded and includes a latch device capable of maintaining the retainer in a contracted state.
In a further representative embodiment, a method of anchoring a lead comprises inserting a lead into a sleeve while a retainer disposed around the sleeve is in an expanded state; contracting the retainer to a contracted state; and compressing the sleeve against the lead with the retainer while the retainer is in the contracted state. The method can further comprise placing the retainer in the expanded state and repositioning the lead with respect to the sleeve. The method can further comprise attaching the sleeve to a patient.
From the foregoing, it will be appreciated that specific embodiments of the disclosed technology have been described herein for purposes of illustration, but that various modifications may be made without deviating from the technology. For example, in a particular embodiment the cover may be provided with a single opening to provide access to the retainer. In some embodiments, the opening may extend transverse to the longitudinally extending sleeve. In other embodiments, the opening comprises a slit formed in the flexible material of the cover. In still other embodiments, the ends of the retainer can include other features besides apertures that a suitable tool can engage in order to actuate the retainer. For example, the ends of the retainer can include flats or hook features. In certain embodiments, the anchor tabs can extend from one side or both sides. In yet further particular embodiments, representative anchors in accordance with the present technology can be used to secure medical devices other than neural stimulation leads. Representative stimulation systems and associated therapies are disclosed in the following references, all of which are incorporated herein by reference: U.S. application Ser. Nos. 12/264,836; 13/607,617; and U.S. Pat. No. 8,712,533. To the extent that the foregoing references and/or any other material incorporated herein by reference conflict with the present disclosure, the present disclosure controls.
Certain aspects of the disclosure described in the context of particular embodiments may be combined or eliminated in other embodiments. For example, in some embodiments the anchor tabs can be eliminated. In other embodiments, the grooves associated with the anchor tabs can be eliminated. In certain embodiments in which the retainer is formed from a biocompatible material, the cover can be eliminated. Any of the elements of the technology disclosed herein can be combined in any suitable combination. For example, the retainer 220 described with respect to FIGS. 6A and 6B can be combined with the lead anchor 100.
Further, while advantages associated with certain embodiments have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the present disclosure. Accordingly, the present disclosure and associated technology can encompass other embodiments not expressly shown or described herein.

## Claims

1. A lead anchor, comprising:
a longitudinally extending sleeve having an aperture sized and positioned to receive a lead therethrough;
a retainer disposed around the sleeve and operative to compress at least a portion of the sleeve against a lead extending through the aperture; and
a cover extending around the retainer.

2. The lead anchor of claim 1, wherein the retainer is a tube elastically deformable from a contracted state to an expanded state.

3. The lead anchor of claim 2, wherein the tube has an oval cross section in the contracted state and a circular cross-section in the expanded state.

4. The lead anchor of claim 1, wherein the cover includes a pair of openings aligned with the retainer to provide access to the retainer from outside the cover.

5. The lead anchor of claim 4, wherein the openings are longitudinally extending slots.

6. The lead anchor of claim 1, wherein the retainer is a circlip having a pair of apertures engageable with a tool.

7. The lead anchor of claim 6, further comprising a spacer disposed between the pair of apertures to maintain the circlip in an expanded state.

8. The lead anchor of claim 7, wherein the spacer is frangible.

9. The lead anchor of claim 7, wherein the spacer is deformable.

10. A spinal cord lead anchor, comprising:
a longitudinally extending sleeve having an aperture sized and positioned to receive a spinal cord lead therethrough;
a retainer disposed around the sleeve and operative to compress at least a portion of the sleeve against a spinal cord lead extending through the aperture;
a cover extending over the retainer including at least one opening formed through the cover to facilitate engaging the retainer with a tool; and
a pair of anchor tabs positioned to facilitate attaching the lead anchor to a patient.

11. The spinal cord lead anchor of claim 10, wherein the anchor tabs extend from the cover.

12. The spinal cord lead anchor of claim 11, wherein the anchor tabs each include an anchor aperture.

13. The spinal cord lead anchor of claim 12, wherein the cover includes two grooves, each one aligned with a corresponding one of the anchor tabs.

14. The spinal cord lead anchor of claim 10, wherein the retainer is normally contracted.

15. The spinal cord lead anchor of claim 14, wherein the retainer is a circlip having a pair of apertures engageable with a tool.

16. The spinal cord lead anchor of claim 10, wherein the retainer is normally expanded.

17. The spinal cord lead anchor of claim 16, wherein the retainer includes a latch device positioned to maintain the retainer in a contracted state.

18. A method of anchoring a lead, comprising:
inserting a lead into a sleeve;
maintaining a retainer disposed around the sleeve in an expanded state with a spacer;
removing the spacer, thereby changing the retainer to a contracted state; and
compressing the sleeve against the lead with the retainer while the retainer is in the contracted state.

19. The method of claim 18, further comprising placing the retainer in the expanded state and repositioning the lead with respect to the sleeve.

20. The method of claim 18, further comprising attaching the sleeve to a patient.

21. A lead anchor, comprising:
a longitudinally extending sleeve having an aperture sized and positioned to receive a lead therethrough;
a retainer disposed around the sleeve and operative to compress at least a portion of the sleeve against a lead extending through the aperture, wherein the retainer is a normally contracted circlip having a pair of apertures engageable with a tool; and
a cover extending over the sleeve and the retainer, the cover including:
a pair of longitudinally extending slots, each slot aligned with one of the apertures to provide access to the pair of apertures from outside the cover;
at least one anchor tab positioned to facilitate attaching the lead anchor to a patient; and
an associated groove aligned with the at least one anchor tab.

22. A lead anchor, comprising:
a longitudinally extending sleeve having an aperture sized and positioned to receive a lead therethrough;
a retainer disposed around the sleeve and operative to compress at least a portion of the sleeve against a lead extending through the aperture, wherein the retainer is a circlip having a pair of apertures engageable with a tool; and
a spacer disposed between the pair of apertures to maintain the circlip in an expanded state.