US20090112301A1 - Strain Relief System For Spinal Cord Stimulation Lead - Google Patents

Abstract

An anchor for spinal electrical stimulation leads having a first, extended portion adapted to be inserted through the spine and into the spinal column, and a second, shorter portion adapted to be sutured to the fascia on the outside of the spine. The extended portion assists with positioning of the electrode tip onto the spinal cord on provides strain relief for the electrode. The anchor further comprises an inner tube disposed inside of the housing along an intermediate portion between the extended portion and the shorted portion. When the outside portion of the tubular housing is sutured to the fascia of a patient, the inner tube is compressed against the electrical lead, thereby locking it in place and preventing migration over time.

Description

BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates to medical devices and, more particularly, to a strain relief system for implantable electrical stimulation leads.
• 2. Description of the Related Art
• Spinal cord stimulation (SCS) is frequently used to treat patients with chronic neuropathic pain in who have not found relief using other treatments. In general, neurostimulation works by applying an electrical current to the nerves located near the source of chronic pain. More particularly, a thin wire with an electrical lead at one end is implanted into a patient in the location to be treated, such as a particular portion of the spine. An electrical generator connected to the wire is used to deliver electrical current to the lead, thereby stimulating the nerves at the treatment location.
• Although spinal cord stimulation may produce dramatic results for patient pain care, the systems used to supply the electrical stimulation to the spine are subject to failure and may lead to reduced effectiveness or require additional surgery to correct or replace the defective portions of the system. The most common complications associated with spinal cord stimulation fall into two general categories. The first category of problems that affects spinal cord stimulation systems is the migration of the electrodes away from the intended targets. This complication may occur in over ten percent of patients receiving spinal cord stimulation. The second category of problems that affects spinal cord stimulation systems is the breakage of the electrical leads. This complication may occur in nearly ten percent of patients receiving spinal cord stimulation. As a result of these complications, the spinal cord stimulation system may need to be repaired or replaced, if possible, through additional patient surgical procedures. Thus, the risks to the patient of more serious complications and the overall costs associated with obtaining neurostimulation treatment are increased.
• Convention methods for affixing stimulation leads in place include suture sleeves having elastomeric gripping portions positioned therein. When the suture sleeve is sutured into position along the spinal column, the gripping sleeve is compressed around the pacing lead, thereby enhancing retention of the lead. While such systems may limit lead migration, they do not limit the stresses that cause fracturing or breaking of the lead wires. Conventional methods for reducing fracturing involve the use of strain relief members that extend from the lead anchors. Unfortunately, these strain relief members simply relocate stress points and thus fail to reduce the occurrence of fractures.
BRIEF SUMMARY OF THE INVENTION
• It is therefore a principal object and advantage of the present invention to provide a system and method for anchoring spinal cord stimulation leads that reduces lead migration.
• It is a further object and advantage of the present invention to provide a system and method for anchoring spinal cord stimulation leads that reduces lead fractures.
• It is an additional object and advantage of the present invention to provide a system for anchoring spinal cord stimulation leads that reduces the risks to patients.
• It is another object and advantage of the present invention to provide a system for anchoring spinal cord stimulation leads that reduces the risks to patients.
• In accordance with the foregoing objects and advantages, the present invention is an anchor for spinal electrical stimulation leads. The anchor comprises a flexible, tubular housing through which an electrical stimulation electrode may be passed. The housing generally comprises a central portion adapted for attachment to the fascia of the spine, a rear portion extending from the back of the central portions, and a front portion extending forwardly from the central portion. The central portion of the housing may optionally comprise a pair of flanges extending transversely outwardly, each of which includes a pair of holes formed therethrough for accepting the sutures. The central portion of the housing may further include an inner tube disposed therein. When the central portion of the tubular housing is sutured to the fascia of a patient, the inner tube is compressed against the electrical lead, thereby locking it in place and preventing migration of the lead. The front portion of the housing is dimensioned to be inserted at least partially through the ligamentum flavum (interspinal ligament) and, preferably, entirely through the ligamentum flavum into the epidural space of the spine. The anchor is preferably manufactured from a flexible polymer so that the front portion of the housing can bend flex after passing through the spine and into the spinal cavity, thereby providing strain relief for an electrical lead passing therethough and reducing fracturing of the electrical lead. The material used to form the anchor may further be impregnated with barium so that the anchor is visible when imaged using a fluoroscope.
BRIEF DESCRIPTION OF THE DRAWINGS
• The present invention will be more fully understood and appreciated by reading the following Detailed Description in conjunction with the accompanying drawings, in which:
• FIG. 1 is perspective view of an electrical stimulation lead anchor according to the present invention.
• FIG. 2 is a front end view of another embodiment of an electrical stimulation lead anchor according to the present invention.
• FIG. 3 is a rear end view of an electrical stimulation lead anchor according to the present invention.
• FIG. 4 is a longitudinal cross-section of an electrical stimulation lead anchor according to the present invention.
• FIG. 5 is a partial cross-sectional view of spinal column including an embodiment of an electrical stimulation lead anchor according to the present invention.
DETAILED DESCRIPTION OF THE INVENTION
• Referring now to the drawings, wherein like reference numerals refer to like parts throughout, there is seen inFIG. 1 ananchor10 for providing strain relief to a spinal electrical stimulation lead12 passing therethrough.Anchor10 comprising a flexible,tubular housing14 through whichelectrical stimulation electrode12 passes.Housing14 includes afront portion16 adapted to be inserted at least partially through the ligamentum flavum and, preferably, entirely through the ligamentum flavum into the epidural space of the spinal column to assist in positioning theelectrode tip18 ofelectrode12 onto the appropriate portions of the spinal cord.
• Housing14 includes acentral portion20 adapted to be sutured to the fascia on the outside of the spine.Central portion20 ofhousing14 may further optionally comprise a set offlanges22 extending from opposing sides ofhousing14 to provide additional locations for the attachment of sutures. Eachflange22 includes a pair ofapertures24 formed therethrough.Apertures24 are dimensioned to accept the sutures used to secureanchor10 to the fascia of the spine.Central portion20 ofhousing14 may also include a series ofgrooves26 formed in an outer portion thereof to provide for interlocking ofanchor10 with the sutures used to secureanchor10 to the fascia of the spine.
• Referring toFIGS. 2 through 4,central portion20 may include atube28 positioned therein for assisting in clamping againstlead12 whenanchor10 is sutured to the fascia of the spine. When outside portion ofhousing14 is sutured to the fascia of a patient,inner tube28 is compressed againstelectrical lead12, thereby lockinglead12 in place and preventing migration oflead12 after insertion into a patient. Anchor10 is preferable manufactured from a flexible polymer so that extendedportion16 ofhousing14 can flex after passing through the spine and into the spinal cavity, thereby providing strain relief forelectrical lead12 passing therethough, thereby reducing fracturing ofelectrical lead12 when in use by a patient. Preferably,anchor10 is manufactured from a polymer having a durometer of between about 50 and about 60 to provide sufficient flexibility for insertion of extendedportion16 ofhousing14 into or through the ligamentum flavum and providing strain relief for a lead passing therethough. It should be recognized that those of ordinary skill in the art in thatanchor10 should be manufactured to be slightly less or more pliable thanlead12 to provide strain relief and reduce failures, depending on theparticular lead12 being used withanchor10.Anchor10 may further be impregnated with barium so thatanchor10 is visible on x-rays.
• Referring toFIG. 5,front portion16 is dimensioned to be inserted at least partially through theligamentum flavum30 and, as preferably shown, entirely through theligamentum flavum30 into theepidural space32 ofspinal column34. The particular angle of insertion offront portion16 is not shown to scale inFIG. 5, and is preferably greater than ninety degrees with respect to the longitudinal axis ofspinal column34. Those of skill in the art will recognize that the particular dimensions offront portion16 and angle of insertion intoligamentum flavum30 will vary according to the anatomy of the particular patient. Generally, in order forfront portion16 ofanchor10 to reach intoligamentum flavum30 from the anchor point atop thespinus process36,front portion16 will need to be between about 12 and about 18 centimeters long. It should be recognized by those of skill in the art that the length offront portion16 depends on the physical structure of the patient and may be determined with relation to the size of the patient.Anchor10 may be manufactured in various lengths to be selected by the surgeon after determining the appropriatelength front portion16 for the particular patient, orfront portion16 ofanchor10 may be configured to be trimmed by the surgeon to the appropriate length.

Claims (12)

1. An apparatus for anchoring a neurostimulation lead in a patient, comprising:

a tubular housing having a first portion for anchoring the housing proximately to the spinus process of the patient and a second portion extending from the first portion for providing strain relief; and

wherein said second portion is configured to extend at least partially into the ligamentum flavum of the patient when said first portion is attached to the patient.

2. The apparatus ofclaim 1, wherein the second portion is configured to extend entirely through the ligamentum flavum into the epidural space of the patient.

3. The apparatus ofclaim 1, wherein the second portion is between 12 and 18 centimeters long.

4. The apparatus ofclaim 1, further comprising at least one flange extending outwardly from the first portion of the housing.

5. The apparatus ofclaim 4, wherein each flange includes at least two holes formed therethrough.

6. The apparatus ofclaim 1, further comprising at least one ridge extending circumferentially around the first portion of the housing.

7. The apparatus ofclaim 1, further comprising a tube positioned in the first portion of the housing.

8. The apparatus ofclaim 7, wherein the tube is compressible.

9. The apparatus ofclaim 1, wherein the anchor has a durometer between about forty and sixty.

10. A neurostimulation system kit, comprising:

an anchor comprising a tubular housing having a first portion extending longitudinally along an axis and a second portion extending from the first portion, wherein said second portion is configured to extend at least partially into the ligamentum flavum of the patient when said first portion is attached proximately to the spinus process of the patient.

a neurostimulation lead adapted to be passed through the first and second portions of the anchor into the epidural space of the spine of a patient; and

an electrical generator adapted for attachment to the lead and delivering electrical energy to the patient through the lead.

11. The anchor ofclaim 10, wherein the second portion of the housing is configured to extend entirely through the ligamentum flavum into the epidural space.

12. The anchor ofclaim 10, wherein the second portion is between 12 and 18 centimeters long.

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