Abstract:
The implantable monopolar electrode assembly includes a base support structure including a layer made of a nickel titanium alloy having a temperature memory. The method is directed to electro-stimulation of muscles and to a method of implanting a monopolar electrode assembly. The method includes the steps of: first performing an endoscopic approach to the nerves and then selective electro stimulation by performing a neurolysis on nerve trunks until a desired target nerve fascicle and associated muscle is located, followed by insertion of the monopolar electrode assembly adjacent the target nerve fascicle for subsequent connection to a neurposthesis system.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to electro-stimulation of muscles and more specifically to a monopolar electrode for such stimulation and a method of implanting such an electrode by first performing an endoscopic approach of the nerves and then selective electro stimulation by performing a neurolysis on nerve trunks. 
         [0003]    2. Description of the Prior Art 
         [0004]    Electro stimulation has been used for many years to activate muscles artificially by controlling three parameters: 1) frequency in Herz, 2) intensity in milliampere and 3) pulse width in microsecond. The clinical applications were made principally on paralysed patients from cerebral origin like in hemiplegia or from spinal cord origin like in tetraplegia (paralysis of the four limbs by cervical spine lesion) or paraplegia (lower limbs paralysis by thoracic level lesion). The electrical stimulation can be applied by electrodes placed on the skin (cutaneous), on the surface of the muscles at the motor point (epimysial), within the muscles (intramuscular), on the nerves (neural), within the fascicules of a nerve (intrafascicular), on the spinal roots (radicular) or on the spinal cord (epidural). 
         [0005]    The technical devices used in the case of implantation are always the same: electrodes, electronic implant, antenna transferring power and signal and external programmer or controller doing what the brain is normally doing: choosing the right muscle at the right time. 
         [0006]    Many researchers in the world have been trying to restore motor functions by FES (functional electrical stimulation), first with surface electrodes and then with an implant that can be called a neuroprosthesis. The domain is very large and it is possible to identify: the motor neuroprosthesis in order to restore walking and grasping, the sensorial neuroprosthesis for blind, deaf and pain, the visceral neuroprosthesis for heart (pacemakers), bladder or colon. 
         [0007]    A few teams are very active in this field, such as: Professors Mortimer and Peckham from Cleveland who created the Neurocontrol Company producing the Free Hand System to restore grasping in tetraplegic patients and the Free Stand System to restore locomotion. But this company closed down a few years ago and the production of this system has stopped. 
         [0008]    Many companies that produce cochlear implants were using the same technology to produce motor neuroprosthesis. That is the case for Nucleus in Australia which has the largest part of the cochlear implant market and MXM from Antibes in France. 
         [0009]    At the moment, the Alfred Mann Foundation in California is producing a very interesting component called BION which was designed by G. Loeb from Toronto, Canada and Joseph Schulman from the US. Their present version is made with a 16 mm length electronic component which is a single channel microstimulator acting in monopolar mode and activated by a radiofrequency link. Another version is equipped with a battery and is called FES BION. 
         [0010]    In France, at the Faculty of Medicine in Montpellier and jointly with a Biomechanical Research Unit belonging to INSERM (French National Institute of Health and Medical Research) an implant was designed having epimysial electrodes and was used with two paraplegic patients. 
         [0011]    A method for restoring walking in paraplegic patients was initiated in 1996 and applied to two patients in 1999. It involved using implanted electro stimulation made by three components: first, an electronic implant able to distribute electric current to the different targets, nerves and muscles, at the right time, second, specific electrodes, are placed at the surface of the muscles as close as possible to the motor point (epimysial electrodes) or placed around a nerve or a fascicle of a nerve (neural electrode) with low tension from 0.8 v to 12 v using a cuff electrode having a diameter from 0.5 mm to 10 mm and third, an outside equipment made by an antenna placed on the skin in the front of the internal antenna of the implant transferring the electrical power and the signal and connected with an external programmer which is doing what the brain is normally doing: activating the right muscle at the right time. The implantation of electrodes requires an open surgery with different incisions corresponding to the muscular targets, representing a potential risk of infection as well as skin scars which can be aesthetically critical. It was observed with the two operated patients that the epimysial electrodes are relatively difficult to put in the optimal place in relation with the motor point which can be multiple in big muscles like the gluteus maximus. It was also noted that having too many wires travelling within the body is a risk to carry an infection, as observed in one of the patients who got an infection due to a small wire emerging outside of the skin a long time after the surgical procedure and collecting a germ from the urinary pubic region forcing the surgical team to remove all the implanted devices even if an antibiotic treatment was employed. 
         [0012]    Listed below are several prior art patents disclosing the use of cuff electrodes for providing electro-stimulation to nerves. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                 U.S. Pat. No. 
                 Patentee 
               
               
                   
                   
               
             
             
               
                   
                 5,038,781 
                 Lynch 
               
               
                   
                 5,167,229 
                 Peckham et al. 
               
               
                   
                 6,163,725 
                 Peckham et al. 
               
               
                   
                 6,718,210 
                 Peckham et al. 
               
               
                   
                   
               
             
          
         
       
     
         [0013]    The main technical problem in neuromuscular stimulation is to be able to put in place the electrodes with a minimal invasive procedure. 
       SUMMARY OF THE INVENTION 
       [0014]    According to the teachings of the present invention there is provided a method for the electro-stimulation of muscles and a method for implanting a monopolar electrode. The method includes the steps of: first performing an endoscopic approach to the nerves and then selective electro stimulation by performing a neurolysis on nerve trunks until a desired target nerve fascicle and associated muscle is located, followed by insertion of a monopolar electrode adjacent the target nerve fascicle for subsequent connection with a connection wire having a steel spring and a platinum wire to a neurposthesis system. Preferably, the endoscopic approach is in the stomach and the stomach is first inflated with air. The monopolar electrode for electrostimulation of a fascicle in a nerve bundle comprises a bared end of an insulated wire which is fixed to an insulated base structure adapted to be positioned adjacent a fascicle in a nerve bundle. In one embodiment, the base support is made of insulated Nitinol which is soft below the temperature of a human body and which forms a curled spiral shape at the temperature of a human body. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0015]      FIG. 1  is perspective view with a portion broken away of a peripheral pelvic nerve and shows a plurality of fascicles of the nerve. 
           [0016]      FIG. 2  is a sectional view of one fascicle of nerves. 
           [0017]      FIG. 3  illustrates a surgical neurolysis of a nervous trunk. 
           [0018]      FIG. 4  illustrates a procedure for identifying a nerve in a fascicle of nerves by bipolar stimulation. 
           [0019]      FIG. 5  is a perspective view of a monopolar neural electrode constructed according to the teachings of the present invention. 
           [0020]      FIG. 6  is a perspective view of the monopolar neural electrode mounted to a nervous trunk and in electrical contact with a selected nerve. 
           [0021]      FIG. 7  is a plan view of a memory shape electrode assembly constructed according to the teachings of the present invention. 
           [0022]      FIG. 8  is a plan view of the memory shape electrode after it has been placed around a nerve and warmed to body temperature to cause the electrode to assume a curled spiral shape about the nerve. 
           [0023]      FIG. 9  is a cross-sectional view of the electrode shown in  FIG. 7  and is taken along line  9 - 9  in  FIG. 7 . 
           [0024]      FIG. 10  is a perspective view of another embodiment of an electrode, constructed according to the teachings of the present invention, around one fascicle and fixed by sutures to adjacent tissue. 
           [0025]      FIG. 11  is a perspective view of a nerve trunk with a portion broken away to show fascicle and showing still another embodiment of two electrodes, constructed according to the teachings of the present invention, positioned around two respective fascicle. 
           [0026]      FIG. 12  is a perspective view of one of the three layer electrodes shown in  FIG. 11 . 
           [0027]      FIG. 13  is a cross-sectional view of the electrode shown in  FIG. 12  with a fascicle show within the electrode and is taken along line  13 - 13  in  FIG. 12 . 
           [0028]      FIG. 14  is a cross-sectional view of the electrode shown in  FIG. 13  closed around the fascicle, but, for illustrative purposes, with the fascicle shown adjacent the electrode. 
           [0029]      FIG. 15  is a perspective back view of the electrode shown in  FIG. 13 , is taken along line  15 - 15  of  FIG. 13  and shows an opening in the back of the electrode for a wire conductor to extend into the three layer electrode. 
           [0030]      FIG. 16  is a perspective view of an open cuff electrode assembly. 
           [0031]      FIG. 17  is a perspective view of a semi-open cuff electrode assembly. 
           [0032]      FIG. 18  is perspective plan view of a platinum strip for use in a lasso electrode assembly. 
           [0033]      FIG. 19  is a perspective view of the lasso electrode assembly folded over for capturing a nerve. 
           [0034]      FIG. 20  is a perspective view of the lasso electrode assembly around a nerve. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0035]    Referring now to the drawings in greater detail, a peripheral pelvic nerve bindle  10  is shown in  FIG. 1  cut away to show a plurality of fascicles  12  of the nerve  10 . A cross section of one fascicle  12  is shown in  FIG. 2 . 
         [0036]    According to the teachings of the present invention individual fascicles  12  are selected from the nerve bundle  10  with a tool  14  as shown in  FIG. 3  or a tool  15  as shown in  FIG. 4  and supplied with a stimulus to determine which muscle it controls, i.e., the target. This process is repeated until a desired fascicle  12  is located. 
         [0037]    Once the desired fascicle  12  is found, a monopolar electrode  16  including a bare wire conductor end  18  of an insulated wire conductor  20  fixed to a U-shaped and winged insulating base support  22  (like a BX or conduit strap in shape), as shown in  FIG. 5 , is positioned around the desired fascicle  12  as shown in  FIG. 6 . The base support  22  has the general shape of a conduit strap or clamp. A fixation clamp  24  is mounted on the wire  20  for use in securing the electrode  16  to surrounding tissue. This clamp is secured to adjacent tissue by sutures  25  that extend through an opening  23  in the clamp  24 , as shown in  FIG. 10 . 
         [0038]    An alternative form of monopolar electrode  26  is shown in  FIG. 7 . the electrode  26  comprises a bare wire end  27  at the inner end of an insulated wire conductor  28 . The wire conductor  28  has a male prong connector  29  at it&#39;s outer end. The bare wire end  27  is mounted on a curved strip  30  of memory material forming a base support structure  30  and being insulated on the back side as shown in  FIG. 7 . The memory material is preferably a nickel titanium alloy known as Nitinol. Nitinol has a temperature shape memory where, at a lower temperature, the strip  30  is soft with a flat shape and easily formed and where, at a higher temperature which is at or below the normal temperature of a human body, the strip  30  assumes a harder, curled shape, embracing a fascicle  12  adjacent which the strip  30  is positioned, as shown in  FIG. 8 . 
         [0039]      FIG. 9  shows a cross section of the strip  30  with two wings  31  and  32  and a coating of insulation  33  on the backside of the strip  30 . 
         [0040]      FIG. 10  shows another embodiment of a metal electrode  34  including a straight electrode portion  35  and an arcuate electrode portion  36  which is held around a fascicle  12  by a double layer, pipe hanger shaped, clamp  38 . The clamp  38  includes an outer layer of flexible insulating material  40  which is adhered to an inner metal layer  42  which defines a base support, which can be made of Nitinol, which initially can have an open shape for being inserted around the fascicle  12  or which can be made of insulating material. The arcuate electrode portion  36  can be fixed to the layer  42 , can be made of Nitinol or can be flexible for being conformed by a Nitinol layer  42  around and in contact with the fascicle  12 . The clamp has a generally pipe hanger shape with a generally cylindrical portion which is received around a fascicle  12  and two, parallel, leg portions which extend radially outwardly from the cylindrical portion for attaching the clamp  38  to adjacent tissue. 
         [0041]    The flat electrode portion  35  is connected to the insulated wire conductor  28  which has a clamp  24  thereon for being sutured to adjacent tissue by sutures  25  extending through opening  23  in the clamp  24 . 
         [0042]    The layer  40  and the layer  42  of the clamp  38 , in the portions thereof extending from the fascicle  12 , have mating openings  44 ,  48  and  46 ,  50  on either side of the straight electrode portion  35  for receiving sutures  52  for securing the clamp  38  and electrode  36  to adjacent tissue. 
         [0043]    A perspective view of a nerve trunk  60  of fascicle  12  is shown in  FIG. 11  and two electrode assemblies  62 , constructed according to the teachings of the present invention are shown positioned, respectively, around two of the fascicle  12 . 
         [0044]    Each electrode assembly  62  is connected by an insulated wire conductor  28  to a connector  64  for connection to a source of electrical stimulation voltage as shown in  FIGS. 11-13  and  15 . 
         [0045]    As shown in  FIGS. 13-15 , each electrode assembly  62  is C-shaped and includes three sem-cylindical layers comprises an inner electrode layer  66  having a large surface area in contact with the fascicle  12 , a silicon insulating layer  68  and an outer layer  70 . The inner electrode layer  68  can be made of platinum or Nitinol or of another flexible metal. The outer layer can be made of Nitinol which, at a temperature lower than body temperature, is partially open, as shown in  FIGS. 12 ,  13  and  15 , and, when received around a fascicle  12 , assumes the shape shown in  FIG. 12 . The layers  68  and  70  form a base support structure for the inner layer electrode  66 . 
         [0046]      FIG. 15  shows a back side  72  of the electrode assembly  62  with an opening  74  for receiving the bare end of the wire conductor into the electrode assembly  62  for connection to the inner electrode layer  66 . 
         [0047]    In  FIG. 16  there is illustrated an open cuff monopolar electrode assembly  80  in the shape of a pipe clamp or BX cable clamp. The assembly  80  includes a insulating base support portion  82  made of an insulating material, e.g., plastic, and comprises a partially cylindrical portion  84  with a longitudinal slot  86  therein and opposed wing portions  88  and  90  which extend laterally outwardly from the slot  86  and from the cylindrical portion  84 . A flat curved platinum electrode  92  is mounted on an inner cylindrical surface  94  of the partially cylindrical portion  84  positioned to make electrical contact with a nerve inserted into the partially cylindrical portion  84 . A wire conductor  96  extends through the partially cylindrical portion near one wing portion  88  and is electrically connected to the flat platinum electrode  92 . A removable rod or skirt  98 ,  100  is fixed to each wing  88  and  90  for being gripped to pull the wings away from the slot  86  to expand the slot  86  to enable a nerve to be inserted through the expanded slot  86  into the partially cylindrical portion  84 , When the rods or skirts  98 , 100  are released the cylindrical portion gripps the nerve inserted therein and presses the platinum electrode against the nerve. 
         [0048]    In  FIG. 17  there is illustrated a semi-cuff monopolar electrode assembly  110  which includes an insulating base support portion  112  that is made of an insulating material, e.g., plastic and includes a partially cylindrical portion  114  with a longitudinal slot  116  therein. One wing  118  extends from a side of the partially cylindrical portion near the slot  116 . A rod or skirt  120  is removably mounted to the wing  114  and a second rod or skirt  122  is removably mounted to the cylindrical portion near the slot  116  on a side of the partially cylindrical portion  114  which is on the other side of the slot  116  from where the wing  114  is fixed to the partially cylindrical portion  114 . A flat curved platinum electrode  124  is mounted on an inner surface  126  of the partially cylindrical portion and a wire conductor  128  extends through the partially cylindrical portion adjacent the wing  118  for electrical connection to the flat platinum electrode. It will be understood that the rods or skirts  120 , 122  are gripped and pulled to open or expand the slot  116  to enable a nerve to be inserted through the expanded slot  116  into the partially cylindrical portion  114 . Then the partially cylindrical portion is allowed to grip the nerve and urge the curved flat platinum electrode against the nerve. 
         [0049]    In  FIGS. 18 ,  19  and  20  there is illustrated a lasso monopolar electrode assembly  130 . In  FIG. 18  a flat but bendable platinum electrode  132  electrically connected to a wire conductor  134 . an approximately 0.05 mm wire  136  extends from the approximately 50 micron thick flat platinum electrode  132  into the coiled wire conductor  134 . 
         [0050]    As shown in  FIG. 19  the flat platinum electrode  132  is curled inside an insulating base support portion  137  comprising an insulating silicon flap  138 . The silicon flap  138  has a narrowed end portion  140  which has serrations  142  on opposite side edges thereof and is adapted to be pulled through a silicon collar  144  which extends around a narrowed portion  146  of the silicon flap  138  and the platinum wire  136 . Preferably the sides  146 ,  148  of the collar  144  has slits  150  therein for being engaged by the serrations  142  to lock the narrowed end portion  140  in the collar  144 . As shown in  FIG. 20 , the narrowed end portion  140  is pulled through the collar  144  to lasso a nerve  152  that has been inserted in a loop created by the flat electrode  132  and the silicon flap  138  and press the flat curled electode  132  against the nerve  152 . 
         [0051]    The testing of fascicles  12  is preferably with an endoscopic approach which allows a very small incision and a very precise work by being close to the nerve with an excellent vision. In this procedure we go into the retroperitoneal space to find the appropriate nerves for the lower limb muscles as well as for the visceral organs placed in the pelvis: bladder, colon and rectum as well as the penis origin. With a team of gynaecologic surgeons, we can approach all those nerves within their pelvic journey. The monopolar electrode  16 ,  26 ,  36 ,  66 ,  80 ,  110  or  130  is used in order to be sure that the electrode  16 ,  26 ,  36 ,  66 ,  80 ,  110  or  130  will be applied directly and closely to the surface of the nerve without using a bipolar cuff which has many disadvantages particularly in relation with its size: too small with the risk of compression of the nerve or too large with the risk of loosing the contact with the nerve. 
         [0052]    A hyper selective nerve stimulation is performed by doing a neurolysis at the level of the trunk of the nerve in order to isolate the right fascicle  12  corresponding to the expected target. In fact in the peripheral nerves, three types of nervous fibres can be found: the motor fibres alpha and gamma, the sensitive fibres and the vegetative fibres (sympathetic and parasympathetic). The organization of the distribution of the fibres, around 110000 for the upper limb, is made with the progressive inclusion of those fibres within a fascicle  12  (or bundle) surrounded by a very strong fibrous sheath called the perineurium. All those fascicles  12  are surrounded by a more lax fibrous sheath called epineurium. The closer one is to the distal part of a nerve, the more precise is the destination of the fascicle  12 . Therefore it is easy and not risky in the hands of a good surgeon to separate by opening the epineurium the fascicles  12  and to identify by stimulation during surgery the right one corresponding to the right target. If no muscular activation occurs, that means that the fascicle  12  is a sensitive one. In addition as demonstrated by an anatomical research, it is always within the fascicle  12  a small artery feeding the nervous fibres and avoiding anoxia during the procedure of isolation of a fascicle  12 . The fibrosis normally occurring after any surgical action was not excessive and not risky for the nerve conduction. The great advantage of this technique is for example in the case of the lower limb to be able to put an electrode for the quadriceps muscle within the trunk of the femoral nerve in the pelvis without opening the skin of the thigh or for the tibialis anterior muscle which is located in the leg to put the electrode on the trunk of the sciatic nerve in the pelvic gluteal area after neurolysis. All the precise surgical protocol for all the important lower limb muscles to be stimulated in order to restore standing and walking as well as the sympathetic and parasympathetic pelvic nerves for bladder, rectum and erection control exits and can be controlled with the implanted electrodes  16 ,  26 ,  36 ,  66 ,  80 ,  110  or  130 . 
         [0053]    The method of the present invention differs from the one used on the two patient in 1999 by the use of an endoscopic approach which is an invasive technique for the implantation of the electrodes. In fact, all the nerves for the innervation of the visceral organs located in the pelvis: bladder, colon and rectum and genital organs as well as all the nerves devoted to the lower limb like gluteal, femoral and ischiatic nerves are reachable by an endoscopic approach. This method comprises first inflating the abdominal cavity with air and second inserting through the abdominal wall by an opening of one to two centimetres an endoscope and the working channels to operate in perfect technical conditions. Therefore it is not possible by an open laparotomy to have the same quality of direct vision of the deep structures than with the endoscope equipped with optic zoom and different vision angles. In addition, the positive pressure within the cavity due to the air inflation is a positive factor reducing substantially the bleeding. 
         [0054]    The first electrode implantation is devoted to the main nervous trunk like femoral nerve or ischiatic nerve in which it is possible without any risk if done properly to isolate by dissecting gently the epineurium surrounding the nerve the right neural fascicle  12  corresponding to the right muscular target to activate in the programme. Using an electro stimulation of the fascicle  12  in a bipolar mode during surgery can easily allow one to identify the nature of the fascicle  12  or muscular made by motor and proprioceptive fibres or sensitive. It is also needed to check carefully the effect of the fascicular stimulation in order to be sure that it corresponds to the muscle that is provided to activate. When the fascicle  12  is identified, the original procedure comprises using an open cuff electrode which electrically isolates the fascicle  12  among the other fascicles  12  of the nerve and has the great advantage not to do any compression of the nerve able to produce by anoxia a conduction trouble. 
         [0055]    The use of a monopolar electrode  16 ,  26 ,  36 ,  66 ,  80 ,  110  or  130  is more simple to put in place and has the great advantage to assure a perfect contact with the nerve which is not the case for the bipolar cuff electrode for which it is needed to find the right shape otherwise if it is too small, it generates a compression of the fascicle  12  or, if it is too large, the contact of the two plots on the nerve can be wrong observed during experimental investigation on animals. 
         [0056]    The second mode is for the muscular or visceral nerves which is possible to isolate by endoscopic dissection. The electrode  16 ,  26 ,  36 ,  66 ,  80 ,  110  or  130  can be made in Nickel Titanium (Nitinol) which is a memory alloy. This material has the property to conserve the shape memory depending of the temperature. At a low temperature in the order of 4 to 5 degrees C., it becomes soft and deformable and at the body temperature it returns to its initial shape. That is of great advantage to put in place the electrode  16 ,  26 ,  36 ,  66 ,  80 ,  110  or  130  and in addition this material is super elastic which guarantee an excellent contact with the nerve. 
         [0057]    From the foregoing description it will be apparent, that the electrodes  16 ,  26 ,  36 ,  66 ,  80 ,  110  or  130  of the present invention and the endoscopic method of implantation of the monopolar electrode  16 ,  26 ,  36 ,  66 ,  80 ,  110  or  130  has a number of advantages, some of which have been described above and others of which are inherent in the method and monopolar electrodes of the present invention. 
         [0058]    Also, it will be understood that modifications can be made to the method and monopolar electrodes of the present invention without departing from the teachings of the present invention. Accordingly, the scope of the present invention is only to be limited as necessitated by the accompanying claims.