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Epidural Needle for Spinal Cord Stimulation Electrode Disclosure Number: IPCOM000011384D
Publication Date: 2003-Feb-14
Document File: 4 page(s) / 25K

Publishing Venue

The Prior Art Database


The mechanical and thermal shape memory properties of Nitinol, in addition to its biocompatibility, provide significant advantages for its use in the cannula and/or stylet of a Spinal Cord Stimulation (SCS) needle. The use of Nitinol or the like will provide the physician with a needle that will not be permanently kinked or permanently bent as a result of the strain and flexing of manipulation during insertion. Once the needle is in place, it will return to its original shape, allowing passage of an SCS electrode(s) through the cannula and into the target tissue.

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Epidural Needle for Spinal Cord Stimulation Electrode


During implantation of an electrode(s) for use in Spinal Cord Stimulation (SCS), a specially designed epidural needle is used.� The needle has a hollow cannula and a stylet that fills the lumen of the cannula.� The lumen of the cannula allows the insertion of the electrode(s) through the needle.� The stylet prevents coring of flesh and occlusion of the cannula during needle insertion, and may also advantageously increase the strength of the needle.

According to a typical procedure, the stylet is first inserted into the cannula.� To facilitate insertion, the distal end of the stylet and/or cannula may be somewhat pointed/sharp.� The needle (cannula with stylet in place) is inserted through the skin and tunneled through tissue until the distal end reaches the epidural space.� Then, the stylet is removed from the cannula, leaving a path for the epidural electrode(s) to pass into the epidural space.

During the typical insertion process, the physician twists and maneuvers the epidural needle in various directions to guide it to the target area.� These motions are at times severe enough to create a kink in the cannula, or even permanently bend the body of the needle, rendering it useless for introducing the epidural electrode(s).� This failure of the epidural needle to maintain its shape forces the physician to discard the bent needle and start all over again with a new needle.� This adversely affects the patient due to increased trauma and increased procedure time.

What is needed is a needle that can be manipulated easily into position, without becoming permanently bent or kinked, and therefore unusable.

Detailed Description

This invention comprises an epidural needle whose cannula is made of super elastic metal, such as Nitinol, an alloy of nickel and titanium.� In addition, a stylet for the epidural needle, which is also made of super elastic metal such as Nitinol, is included in a preferred embodiment.

Nitinol has three significant properties that lead to its ability to perform well as an epidural needle.� These effects – thermal shape memory, superelasticity, and biocompatibility – are based on microscopic-scale metallurgical fundamentals that lead to different macroscopic behaviors, as described below.

Thermal shape memory alloys contract when heated, rather than expanding, which is the reaction of most metals.� In addition, shape memory alloys have the ability to return, via a phase-change (a change in the arrangement of atoms), to a predetermined shape upon heating.� When Nitinol is in the martensitic (i.e., low-temperature) form, it is easily deformable.� The phase transformation takes place as the alloy is heated, which causes the transition into the stronger, austenitic (i.e., high-temperature) phase.� The alloy “remembers” its high temperature austenite form, and recovers its previous shape...