System for informational magnetic feedback in adjustable implants

Abstract

According to some embodiments, systems and methods are provided for non-invasively detecting the force generated by a non-invasively adjustable implantable medical device and/or a change in dimension of a non-invasively adjustable implantable medical device. Some of the systems include a non-invasively adjustable implant, which includes a driven magnet, and an external adjustment device, which includes one or more driving magnets and one or more Hall effect sensors. The Hall effect sensors of the external adjustment device are configured to detect changes in the magnetic field between the driven magnet of the non-invasively adjustable implant and the driving magnet(s) of the external adjustment device. Changes in the magnetic fields may be used to calculate the force generated by and/or a change in dimension of the non-invasively adjustable implantable medical device.

What is claimed is: 
     
         1 . A medical implant, for wireless adjustment of a dimension within a body, comprising:
 a first portion, configured for coupling to a first location in the body;   a second portion, configured for coupling to a second location in the body;   a magnetic drive configured to adjust a relative distance between the first portion and the second portion, the magnetic drive including at least one driven magnet and configured to revolve about an axis in response to a magnetic field imposed by a driver magnet outside of the body;   the implant being configured to transmit a signal indicative of the responsiveness of the driven magnet to the driver magnet;   wherein a change in the responsiveness is indicative of a change in a force applied between the body and the first and second portions.   
     
     
         2 . The medical implant as claimed in  claim 1 , wherein the force is selected from the group consisting of a compression force, a distraction force, a tensile force and a rotation force. 
     
     
         3 . The medical implant as claimed in  claim 1 , wherein the force is converted into a moment. 
     
     
         4 . The medical implant as claimed in  claim 1 , wherein the force is derived at least in part from a magnetic coupling torque. 
     
     
         5 . The medical implant as claimed in  claim 1 , further comprising a radio frequency identification (RFID) chip, wherein the RFID chip is configured to be read by an antenna to indicate an antegrade or retrograde orientation of the medical implant within the body. 
     
     
         6 . The medical implant as claimed in  claim 1 , wherein the signal is configured to be received by an array of magnetic sensors. 
     
     
         7 . The medical implant as claimed in  claim 6 , wherein the signal is configured to be received in a continuous mode, or at a sampling rate of 1,000 Hz. 
     
     
         8 . The medical implant as claimed in  claim 6 , wherein the magnetic sensors are Hall effect sensors. 
     
     
         9 . The medical implant as claimed in  claim 6 , wherein the array of magnetic sensors includes eight magnetic sensors. 
     
     
         10 . The medical implant as claimed in  claim 1 , wherein the signal further comprises information about a magnetic field characteristic in a region surrounding the driver magnet and the at least one driven magnet,
 wherein the magnetic field characteristic changes as the driver magnet magnetically couples with the at least one driven magnet and turns, causing the at least one driven magnet to turn.   
     
     
         11 . The medical implant as claimed in  claim 1 , wherein the signal is indicative of a proximity of the driver magnet to the at least one driven magnet. 
     
     
         12 . The medical implant as claimed in  claim 1 , wherein the signal is indicative of a distance between the driver magnet and the at least one driven magnet. 
     
     
         13 . The medical implant as claimed in  claim 1 , wherein the signal is indicative of an estimated value for a variable dimension of the medical implant. 
     
     
         14 . The medical implant as claimed in  claim 13 , wherein the variable dimension of the medical implant is one of a length, a diameter, or a circumference of the medical implant. 
     
     
         15 . The medical implant as claimed in  claim 13 , wherein the variable dimension of the medical implant may be adjusted at a rate of about 0.5 mm to about 2.5 mm per day. 
     
     
         16 . The medical implant as claimed in  claim 1 , wherein the signal is indicative of a moment applied on a part of the body. 
     
     
         17 . The medical implant as claimed in  claim 16 , wherein the moment is an un-bending moment placed by the medical implant on the part of the body. 
     
     
         18 . The medical implant as claimed in  claim 17 , wherein the part of the body is a scoliotic curve in a spine. 
     
     
         19 . The medical implant as claimed in  claim 1 , wherein the magnetic drive further comprises variable coupling and torque characteristics between at least one driven magnet and the driver magnet. 
     
     
         20 . The medical implant as claimed in  claim 1 , wherein the medical implant further comprises an adjustable intramedullary implant, an adjustable plate implant, an adjustable suture anchor, or an adjustable restriction device.