The present invention relates to implantable medical devices, and specifically, to removable magnetic elements in such devices.
Some hearing implants such as Middle Ear Implants (MEI's) and Cochlear Implants (CI's) employ cooperating attachment magnets located in the implant and the external part to magnetically hold the external part in place over the implant. For example, as shown in
One problem arises when the patient undergoes Magnetic Resonance Imaging (MRI) examination. Interactions occur between the implant magnet and the applied external magnetic field for the MRI. As shown in
Thus, for existing implant systems with magnet arrangements, it is common to either not permit MRI or at most limit use of MRI to lower field strengths. Other existing solutions include use of a surgically removable magnets (e.g. U.S. Pat. No. 8,255,058, incorporated herein by reference in its entirety), spherical implant magnets (e.g. U.S. Pat. No. 7,566,296, incorporated herein by reference in its entirety), and various ring magnet designs (e.g., U.S. Patent Publication 20120238799, incorporated herein by reference in its entirety). U.S. Pat. No. 8,634,909 (incorporated herein by reference in its entirety) describes an implant magnet having a magnetic dipole with a magnetic axis that is parallel to the end surfaces of a disc shaped implant magnet—that is, perpendicular to the conventional magnetic axis of a disc-shaped implant magnet. The magnet is then held in a magnet receptacle that allows the magnet to rotate in response to an external magnetic field such as from an MRI.
Some devices also add a stiffening ring around the magnet to resist torques and help hold the magnet in place.
Embodiments of the present invention are directed to an implantable medical device that includes an implantable coil case, the coil case having a lateral surface, a medial surface, a radial center, and an outer circumference and containing a communications coil for transcutaneous communication of an implant communication signal. A magnet receptacle is located within the coil case at the radial center and has a magnet opening in one of the lateral surface or the medial surface of the coil case. A magnet fitting groove is recessed into one of the lateral or medial surface of the coil case and extends from the magnet opening to the outer circumference of the coil case. A u-shaped implant magnet clip has parallel clip legs that are connected at a closed end of the u-shape, and an implant magnet is attached to one of the clip legs. The coil case and the magnet clip are configured to cooperate for a portion of the coil case to fit between the clip legs and the implant magnet to slide through the magnet fitting groove and fit through the magnet opening into the magnet receptacle.
In further specific embodiments, the magnet receptacle has an angled side wall adjacent to the magnet fitting groove. The implant magnet clip may also include a clip handling projection configured for surgical grasping to manipulate the implant magnet clip. The coil case may be made of silicone material. The magnet clip may be made of biocompatible polymer material such as PEEK, PTFE or FEP. The implant magnet may have a magnetic field direction within the implant magnet that is parallel to the lateral surface. The implant magnet may be rotatably attached to one of clip legs.
In any of the above, the implantable medical device may be a hearing implant system such as a cochlear implant system, a middle ear implant system, or a vestibular implant system, or the implantable medical device may be a laryngeal pacemaker implant system.
In existing implantable medical devices such as hearing implants which use implant magnets, even though considerable progress has been made, compatibility with MRI systems remains challenging. For example, removable implant magnets require a relatively large surgical incision over the implant position in order to remove the magnet, and the silicone pouch that holds the magnet loses its shape after just a couple of magnet removals. Embodiments of the present avoid these problems by using a magnet clip that slides over the surface of the implant coil case.
A u-shaped implant magnet clip 404 has parallel clip legs 405 that are connected at a closed end 406 of the u-shape. One of the clips legs 405 has an implant magnet 407 attached to it. In some specific embodiments, the implant magnet 407 may be rotatably attached to one of clip legs 405. The coil case 401 and the magnet clip 404 are configured to cooperate for a portion of the coil case 401 to fit between the clip legs 405 and the implant magnet 407 to slide through the magnet fitting groove 403 and fit through the magnet opening into the magnet receptacle 402. Thus, there is some flexibility and spring at the closed end 406 of the magnet clip 404 so that the opposing legs 405 may spread apart to fit over the coil case 401.
In some specific embodiments, the implant magnet 407 may have a magnetic field direction within the implant magnet that is parallel to the lateral surface of the coil case 401 as described in U.S. Pat. No. 8,634,909. The coil case 401 also may be slightly recessed at the outer circumference and on the bottom medial side so that the outer surface of the magnet clip 404 lies flush against the outer surface of the coil case 401 as shown in
A clippable implant magnet as described above is better suited than prior existing implant magnet arrangements to allow for easy removal of the implant magnet prior to undergoing an MRI simply by means of a minor surgical procedure using a small incision in the skin over the closed end of the magnet clip. The same small incision can then be used after the MRI to replace the magnet clip.
Although various exemplary embodiments of the invention have been disclosed, it should be apparent to those skilled in the art that various changes and modifications can be made which will achieve some of the advantages of the invention without departing from the true scope of the invention.
This application claims priority from U.S. Provisional Patent Application 62/314,430, filed Mar. 29, 2016, which is incorporated herein by reference in its entirety.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/US2017/024228 | 3/27/2017 | WO |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2017/172566 | 5/10/2017 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
8340774 | Hochmair et al. | Dec 2012 | B2 |
9210521 | Kasic et al. | Dec 2015 | B2 |
20080009920 | Gibson et al. | Jan 2008 | A1 |
20080221641 | Hochmair | Sep 2008 | A1 |
20110284014 | Cadeddu et al. | Nov 2011 | A1 |
20150087892 | Tourrel et al. | Mar 2015 | A1 |
20150359553 | Harnisch | Dec 2015 | A1 |
Entry |
---|
International Searching Authority/US, International Search Report and the Written Opinion of the International Searching Authority, Application No. PCT/US2017/024228, dated May 25, 2017, 10 pages. |
IP Australia, Australian Government, Examination Report No. 1, Application No. 2017241456, dated Dec. 8, 2018, 2 pages. |
Number | Date | Country | |
---|---|---|---|
20190076661 A1 | Mar 2019 | US |
Number | Date | Country | |
---|---|---|---|
62314430 | Mar 2016 | US |