Patent Publication Number: US-2021169490-A1

Title: Medical-grade actuator having a modular structure and medical device comprising same

Description:
TECHNICAL FIELD 
     The present invention relates to the field of implantable medical devices, in particular medical devices comprising an artificial contractile structure for occluding a hollow body organ. 
     STATE OF THE ART 
     In order to treat conditions such as urinary incontinence, faecal incontinence, gastro-oesophageal reflux disease and also for the treatment of obesity by gastric banding, medical devices are often implanted into the patient which comprise an artificial contractile structure, often known as a cuff, attached around a hollow body organ such as the urethra, rectum, oesophagus or the stomach. In order to reduce the diameter of the organ in question or to occlude it, the artificial contractile structure applies pressure thereto. Particularly in the case of urinary or faecal incontinence, the contractile structure essentially creates an artificial sphincter which can be opened and closed by controlling the pressure applied by the cuff. 
     In such applications, it is extremely important to apply this pressure as gently as possible so as to avoid damaging the organ. Currently, this is usually carried out by inflating a tube or balloon-type structure arranged on the inside of the contractile element and which applies pressure on the organ. A commercially successful example of this type of device is the AUS 800 marketed by American Medical Systems, Inc. This device and its predecessors are described in U.S. Pat. Nos. 3,863,622, 4,222,377, 4,412,530, and 4,878,889. When applied for the treatment of urinary incontinence, this device has a silicone pressure regulating balloon implanted in the perivesical space, a silicone control pump implanted in the scrotum or labia and a silicone urethral occlusive cuff wrapped around the bulbous urethra in males or the bladder neck in females. Each component may be filled with saline or radiopaque contrast media, and tubing emanating from each component may be routed between incisions for appropriate connections. The patient operates the device by squeezing the control pump through the scrotal or labial skin, and this action transfers fluid from the cuff to the pressure regulating balloon in order to release pressure on the urethra and permit urination, after which the balloon forces fluid through a restrictor and back into the contractile element so as to re-establish an occlusive urethral pressure within 3 to 5 minutes. Furthermore, the device can be deactivated to allow tissue healing to proceed and urethral edema to subside or before inserting a catheter or other instrument into the urethra. 
     However, this type of device is extremely complicated to implant since three inter-operating components need to be assembled and filled with fluid in situ, and upon inflation it can fold or change its shape in a non-uniform manner, thereby creating so-called “pillows” which can cause a non-uniform pressure to be applied. Furthermore, they are prone to fluid leakage and may cause urethral atrophy and erosion. Fluid leaks may also cause complications such as post-operative infection requiring maintenance or replacement of the device. 
     Various attempts have been made in the past at designing non-hydraulic cuffs which do not suffer from the above limitations. For instance, U.S. Pat. No. 6,074,341 describes a medical device comprising a non-hydraulic cuff which is spring-biased in the occluded position. Tension applied to a wire member by the actuator counteracts the spring bias so as to open the cuff. Upon releasing the tension, the spring bias returns the cuff to its occluded position. This arrangement raises safety concerns, since in the case of a malfunction of the actuator the patient would not be able to urinate and would hence require immediate emergency surgery to prevent kidney damage. US 2012/0184980 describes a medical device comprising a different non-hydraulic cuff structure, in which the cuff is formed as a sheath arranged around the urethra, and wherein a tape arranged inside the sheath is attached to an actuator and is pulled so as to tighten the cuff and apply occlusive pressure to the urethra. However this cuff is complicated and bulky. Yet further examples include US 2012/0296157, which describes medical devices comprising extremely simple wire-actuated cuffs, WO13093074, which describes soft rubber cuffs actuated by wires, and EP 1 547 549 which describes cuffs tightened by twisting a pair of wires situated inside the cuff. A gentle, uniform application of pressure to an organ does not appear to be achievable with any of these three latter examples. 
     An object of the invention is thus to overcome at least partially some of the above-mentioned drawbacks of the prior art. 
     DISCLOSURE OF THE INVENTION 
     The object of the invention is attained by an artificial contractile structure comprising at least one contractile element comprising a flexible strip extending in a longitudinal direction and a closure for forming the contractile element into a closed loop around a hollow body organ, the closure being situated at a first extremity of the flexible strip, the contractile element being adapted to contract a hollow body organ, in such a way that said contractile element is adapted to be in a resting position or in an activated position, the activated position being defined with said contractile element constricting the hollow body organ and the resting position being defined with said contractile element not constricting the hollow body organ. 
     According to the present invention, said artificial contractile device further comprises:
         a flexible transmission comprising a tensioning element being anchored at a first end to a first anchoring point on the flexible strip, said flexible transmission being adapted to tighten the contractile element formed in a closed loop around said hollow body organ upon application of a traction force at and end of the tensioning element by an actuator, and   a connector adapted to connect the flexible transmission to a said actuator, a second end of said tensioning element being anchored in said connector.       

     In consequence, the medical device applies a gentle, uniform pressure to the hollow body organ, without localised pressure spikes, thereby reducing its impact on the underlying tissue, reducing damage thereto. 
     In addition, the device of the invention is extremely easy to implant in a patient and to safely or disconnect from an actuator thanks to the provision of the connector, advantageously of a push-fit, plug &amp; play type. 
     In an embodiment, the tensioning element is covered with a flexible sheath. 
     In an embodiment, the flexible strip comprises a plurality of transversal reinforcement elements extending from a surface thereof opposite a smooth surface arranged for contacting said hollow body organ. 
     In an embodiment, the flexible strip comprises a plurality of openings, each opening being situated between two adjacent transversal reinforcement elements. 
     In an embodiment, the tensioning element is a filament, a wire, a cable or a flat strip. 
     In an embodiment, the tensioning element passes through at least some of the transversal reinforcement elements. 
     In an embodiment, the sheath comprises at least one coiled wire. 
     In an embodiment, the sheath comprises an inner coiled wire coiled in a first direction, and an outer coiled wire surrounding the inner coiled wire and coiled in a second direction opposite to said first direction. 
     In an embodiment, the closure is arranged so as to form the contractile element into a closed loop having one of a plurality of predetermined circumferences. 
     In an embodiment, the closure comprises a tab at an end of the flexible strip and connected thereto by two connecting side walls integrally formed with the tab and flexible strip in order to define a pass-through hole for passing said flexible transmission and connector to form the contractile element in a closed loop around said hollow body organ. 
     In an embodiment, the connector is configured for allowing push-fit connection to an actuator. 
     In an embodiment, said push-fit connector comprises a helicoidal spring or an o-ring linking a first annular groove provided in one of said actuator and said connector and providing a kinematic link with a further annular groove provided in another of said actuator and said connector. 
     In an embodiment, the connector comprises a connecting rod longitudinally movable within a coaxial plug, said connecting rod being attached to said tensioning element ( 31 ). 
     In an embodiment, connecting rod comprises a crenelated part cooperating with releasable hooking members of said plug to allow movement of the connecting rod in said plug. 
     The object of the invention is also attained by a medical device comprising an artificial contractile structure as described above and an actuator comprising a connection socket configured for push-fit connection with said connector, said actuator comprising an actuating mechanism arranged to apply a tensile force to said tensioning element of the flexible transmission when said connector is connected into said socket. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be further described with reference to the figures, which show: 
         FIGS. 1A and 1B : a perspective view of an artificial contractile device according to the invention with an open contractile element assembled with its tensioning device and connector; 
         FIG. 2 : a perspective, close-up view of a closure end of the contractile element of the artificial contractile device of the invention; 
         FIG. 3 : a longitudinal cross-sectional view of the contractile element of the artificial contractile device of the invention; 
         FIG. 4 : a longitudinal cross-sectional view of the connector of the artificial contractile device of the invention; 
         FIG. 5 : a longitudinal cross-sectional view of the connector of the artificial contractile device of the invention connected to a screw type actuator; 
         FIG. 6 : a perspective view of a section of a wire coil element of a sheath for the tensioning device of the artificial contractile device of the invention. 
     
    
    
     EMBODIMENT OF THE INVENTION 
       FIGS. 1A and 1B  illustrates part of an artificial contractile device according to the invention, in particular a contractile element  1 , otherwise known as a cuff, assembled together with a tensioning device  2 . In the view of  FIG. 1 , contractile element  1  is illustrated in its open position, i.e. its position before being applied around a hollow body organ. Contractile element  1  comprises a flexible strip or ribbon  4  extending in a longitudinal direction, and constructed e.g. from implant grade silicone elastomer of sufficient Shore hardness, e.g. of between 40 and 80 Shore A, preferably between 50 and 43 Shore A. As non-limiting examples, liquid silicone elastomers from the company Nusil can be used, for instance MED-4843 with shore A hardness 43, MED-4860 with shore A hardness 60, or MED-4850 with shore A hardness 50. Alternatively, polyurethane or other flexible, biocompatible thermoplastic materials may be used instead of, or additionally to, silicone elastomer. 
     A plurality of transversal reinforcement elements  42  are arranged along flexible strip  4 , evenly spaced and numbering in the present example, however the number and the spacing can be chosen according to the needs of the skilled person. Transversal reinforcement elements  42  are aligned substantially perpendicular to the above-mentioned longitudinal direction and show a substantially curved shape, although other forms are also possible. Advantageously, openings  4343  are provided between pairs of adjacent transversal reinforcement elements  42 . In the present example, these openings  43  are formed as slots between some of the transversal reinforcing elements  42 .  4343 . These openings  43  of generally rectangular form are disposed on the centreline of the contractile element  1  and extend towards its edges. Other forms of openings  43  are of course possible. The openings  43  serve to reduce the tensile force required to apply force to the hollow body organ, since less contractile element material needs to be compressed when the contractile element  1  is actuated. 
     At the distal end of flexible strip  4  is provided a closure  6 , shown in more details in  FIGS. 2 and 3 . Said closure  6  comprises a tab  61  extending at a free end of the flexible strip  4  and connected thereto by means of two connecting side walls  62  integrally formed with the tab  61  and an end flap  41  of the strip  4 . The tab  61 , walls  62  and flap  41  define a pass-through hole  63 . The closure  6  is thus arranged so as to be able to form the contractile element  1  into a closed, substantially circular cuff around a hollow body organ by rolling the flexible strip  4  about a said hollow body organ and passing the opposite free end of the artificial contractile device comprising a connector  5  through the pass-through hole  63  in order to tighten the contractile element  1  to a desired diameter around it. 
     Advantageously, the tab  61  comprises on an inner surface facing the flap  41  slots  64  adapted for cooperating in a snap-fit fashion with the reinforcement elements  42  on the flexible strip  4  to lock the strip in place at a desired constricting diameter when rolled about the hollow body organ. 
     When in place about a hollow body organ in its closed position the maximum circumference of contractile element  1  may be for instance 6 cm for implanting around a male urethra, or 11 cm for implanting around the bladder neck in females. However, other minimum and maximum circumferences are of course possible. As an example, the width of the flexible strip  4  may be between 7 and 10 mm, however naturally larger and smaller widths are likewise possible. As previously described, the closure  6  is arranged so as to be closed at a number of discrete closing positions, or alternatively may be arranged so that it can be closed at any convenient point along the flexible strip  4 . 
     The artificial contractile device of the invention further comprises a tensioning device  2  comprising a flexible transmission  3  extending between said contractile element  1  and said connector  5  to apply a tensile force to the contractile element  1  through an actuator to which connector  5  is attached. 
     Flexible transmission  3  comprises a core of a wire  31  surrounded by a sheath. The sheath comprises an outer sheath  32 , e.g. of silicone elastomer, covering a wire coil  18  ( FIG. 6 ), which covers the wire  31 , broadly following the construction of a Bowden cable. In consequence, pulling or pushing on wire  31  will cause it to move with respect to the sheath. The wire  31  may be e.g. of stainless steel or other metal alloys (e.g. SS 304V, 316L, MP35N, MP35NLT), and may be housed in or coated with an ePTFE or PTFE tube or coating to reduce friction. Additionally, the number and diameter of the strands composing the wire  31  should be chosen to minimise friction, and the wire may also be redrawn so as to make its surface smooth and coated with PTFE or similar lubricant materials. Alternatively, the wire  31  may be made of titanium, Nitinol, or any other convenient biocompatible metal, or a polymer such as PTFE, Aramid, ultrahigh molecular weight polyethylene (e.g. as sold by Dyneema), or similar. Wire  31  may also be flat or oval in cross-section, and may even be of variable cross-section, e.g. circular within the wire coil  18 , and flat within the contractile element  1 . Alternatively, a cable, of either circular or flat cross-section, could be used instead of the wire. 
     Outer sheath  32  comprises a thicker proximal part  32   a  (with respect to connector  5 ) covering flexible transmission  3  from the connector  5  to a more rigid, proximal end of flexible strip  4  connecting it to flexible transmission  3  and a thinner, flexier, distal part  32   b  (with respect to connector  5 ) extending until closure  6  as described herein after. Both proximal and distal parts  32   a,    32   b  are attached to the contractile element  1  by push-fitting it into the openings  43  between reinforcement elements  42 . The wire  31  projects from the outer sheath  32  and wire coil  18  at a distal first end where an anchoring knot  311  is formed, which knot  311  is securely fitted into an anchoring slot  44  of the flexible strip  4 , located close to the closure  6 . The knot  311  may be glued into the corresponding anchoring slot  44  or preferably associated with a first retaining plate  45 , forming a first anchoring point A. Sheath  16  is further secured at a second anchoring point B, located at the interface between proximal and distal parts  32   a,    32   b  of sheath  32 . Said second anchoring point B may be formed by a second retaining plate received in a second anchoring slot arranged in reinforcement elements  42 . Second retaining plate and second anchoring slot are not shown in the figures. First and second retaining plates may be of metallic biocompatible material soldered to the wire coil  18 , and the wire  20  remains free to slide through the coil  18  as described hereinafter. 
     Still preferably, the outer sheath  32  is fully secured to the flexible strip  4  by gluing it or overmoulding it in the constituting material of the strip  4  after positioning of the sheath  32  as explained above, said gluing, overmoulding further allowing formation of a reinforcing end cap  46  for the strip  4  from which the proximal part  32   a  of sheath  32  further extends over the wire coil  18  until connector  5  as described hereinafter. 
     The opposite end of tensioning device  2 , which comprises connector  5 , represented in  FIG. 4 , is arranged to be attached through that connector  5  to an appropriate actuator  7 , partly visible in  FIG. 5 , such as that described in WO13091730, WO13093074 or WO12000681, herein incorporated by reference in their entirety. A force applied by the actuator  7  to wire  31  through connector  5  causes it to slide within wire coil  18  of the flexible transmission  3 , inducing a longitudinal contraction of the flexible strip  4  of the contractile element  1 , which provides the contractile effect on a hollow body organ when said contractile element  1  is looped around such. 
       FIGS. 4 and 5  illustrate a push-fit connector  5  for attaching the flexible transmission  3  comprising wire  313  of tensioning device  2  to an actuator  7 . 
     The illustrated actuator  7  comprises a housing  7   a  inside which a screw-type mechanism  7   b  is mounted. Naturally, other types of mechanism  7   b  are possible. 
     In order to simplify assembly of the entire system in situ, i.e. inside a body cavity of the patient, the attachment of the connector  5  to the actuator  7  is carried out by means of push-fit joints, as will be explained in more detail below. 
     As illustrated in  FIGS. 4 and 5 , a second end of wire  31 , i.e. the end opposite to that forming knot  311  hold in anchoring slot  44  of strip  4 , also comprises an anchoring knot  312  which is secured to a plug  51 . Plug  51  comprises a substantially cylindrical body  51   a,  extending longitudinally within a cavity of a protective shell  34  made of same biocompatible flexible material as sheath  32  and flexible strip  4  preferably, in particular a silicon-based material for example, which can be overmoulded on the plug  51  and integral or glued to the sheath  32 . The protective shell  34  may be retained on plug  51  by material insertion into recesses (not shown) arranged on the outer surface of the plug body  51   a.  A plug head  51   b  extends outwardly from said body  51   a  outside the protective shell  34 . The plug  51  has an open inner channel or tube  51   c  extending over the full length thereof, wherein a connecting rod  52  is fitted, said connecting rod comprising a crenelated part  52   a  housed in the plug&#39;s body  51   a  and a connecting head  52   b  extending through the plug&#39;s head  51   b.  Wire  31  is passed in a lumen or capillary in the connecting rod  52  and its knot  312 , is received in an end recess  52   c  in the connecting head  52   b.  Wire  31  are thus fastened to the connecting rod  52 , which will mechanically link the transmission  3  to the actuator  7  as will be described herein after, 
     Advantageously, the connecting rod  52  can translate within the plug  51  so as to allow tensile strength applied on the connecting rod  52  by the actuator  7  to contract, respectively release, wire  31  in the flexible transmission  3  and thereby the contractile element  11 . That displacement capability can however be limited by the toothed configuration of the crenelated part, which engages with inner hooking members radially extending internally from the plug&#39;s body  51   a  upon application of a pressure as shown by arrows F in  FIG. 5 . Activation of the hooking members allows to lock the connecting rod  52  in position to allow manual disconnection of the connector  5  from the actuator  7  without over-constricting the contractile element around the urethra. This locking mechanism of the connecting rod  52  allows to transfer any pulling/pushing action on the connector  5  only to the plug  51  and not to the wire  31  in the flexible transmission, thereby permitting safe connection and disconnection of the actuator for the constricted organ. 
     The head  51   b  of the plug  51  is cylindrical and is a sliding fit within a tube socket  7   c  extending from the housing of the control system. Upon insertion of the plug head  51   b  into the socket  7   c  the connecting head  52   b  attaches to a distal extremity  7   d  of the screw-type actuator  7   b  by any convenient attachment. In the illustrated embodiment, a first coil spring  71  held within a corresponding first annular groove  71   g  in the distal extremity  7   d  of the screw-type actuator  7   b  cooperates in a corresponding groove  52   d  arranged on the outer surface of the connecting head  52   b . As an alternative, an O-ring may be used instead of a coil spring. Upon insertion of the connecting head  52   b  in the distal extremity  7   d  of the screw-type actuator  7   b,  the coil spring  71  clips into the annular groove  52   d  so as to retain the connecting head  52   b  and plug  51  upon the distal extremity of the screw-type actuator  7  and to transmit force and movement thereto. In this sense, the toroidal spring provides a kinematic link between the connecting rod  52  and the distal extremity of the actuator  7 . As a variation, the position of the two annular grooves  71   g,    52   d  can be inverted if desired, the coil spring  71  thereby being supported in the connecting head  52   b  and clipping into the groove in the distal extremity  7   d  of the actuator  7 . 
     In order to support the outer sheath  32  of the flexible transmission  3 , a distal end of the protective shell  31  of the connector forms a hollow end cap fixed upon the outside of sheath  32  by means of a further toroidal spring  54  provided in between the wire  31  and the sheath  32  on the one end and a seat  55  arranged between a distal end of the crenelated part  52   a  of the connecting rod  52  and the distal end of the cavity  51   c.  The wire  31  pass through an axial passage in the seat  55 . The seat  55  is preferably made of a polymer with low friction and a smaller lumen diameter than the toroidal spring it is guiding to prevent the wire  31  for wearing-off. This is particularly advantageous as the toroidal spring  54  may present sharp edges. The seat  55  is also designed and press-fit or screwed-in to  51   a  so as to resist the push force generated when connecting the plug&#39;s head  52   d  into the screw-type actuator  7   b.    
     In order to minimise ingress of fluid between connector  5  and the socket tube  7   c  and to securely maintain the plug  51  into the socket  7   c  one or more (in the present one of each) coil spring(s)  72  and sealing ring(s)  76  are provided in corresponding grooves in an inner wall of the socket tube  7   c,  in contact with the outer part of the plug head  51   b.    
       FIG. 6  illustrates an embodiment of a wire coil  18  formed of double wire coils  18   a,    18   b  around wire  31 . It can clearly be seen on that figure that inner wire coil  18   a  is wound in a first direction around wire  31 , and outer wire coil  18   b  surrounding the inner wire coil  18   a,  is wound in a second direction opposite to the first direction. Such a double-coil arrangement helps to prevent kinking of the transmission portion of the tensioning device  2  and helps reduce the risk of rupture. It also prevents coil pinching each other when bending the transmission. Outer wire coil  18   b  and optionally also inner wire coil  18   a  may be attached at a first end to anchoring plate  45  and at a second end form or attach to toroidal spring  54  in the seat  55  of the connector  5 . 
     Furthermore, as a simpler alternative, wire coil  18  may be formed as a single coil or further alternatively, a multi-layer coil comprising more than two coils can be used. 
     An alternate arrangement of tensioning device  2 , not illustrated, incorporates a pair of wires  31  arranged so as to operate in opposite directions, such that pulling on a first wire tightens the contractile element  1 , whereas pulling on the second wire loosens the contractile element  1 . 
     In contrast to the prior art cuffs referenced above, the contractile element  1  is not merely tightened by reducing its circumference in the manner of a slipknot or by twisting wires together. When a tensile force is applied by tensioning device  2 , second anchor point B is pulled towards first anchor point A, tightening the wire  31  down on the flexible strip  4 . This causes the contractile element  1  to flex, the transversal reinforcement elements  42  resisting this flexion and causing the contractile element  1  to curve gently in its cross-section broadly into a U-shape or U-like-shape rather than the aggressive V-shape that would be taken by the cross-section of the contractile element  1  in the case in which the transversal reinforcement elements were not present. In consequence, a gentle pressure is applied to the hollow body organ over as large an area as possible, reducing tissue damage. 
     As a result, the contractile element  1  cannot pinch underlying tissue, and applies a pressure of at most 8N/cm2, preferably at most 5N/cm2, further preferably at most 2N/cm2. Furthermore, due to the way in which the flexible strip  4  deforms to apply pressure, this pressure is particularly uniform around the circumference of the flexible strip, and varies by at most 15%, preferably by at most 10%, preferably by at most 5% along the flexible strip  4  where it is in contact with the hollow body organ when the contractile element  1  is activated. 
       FIGS. 1A-1B  illustrate a contractile element  1  assembled with a tensioning device  2  with its flexible transmission  3  attached to connector  5 , ready for implantation. In use the artificial contractile device of the invention can be implanted in a patient by laparoscopy surgery, the contractile element  1 , its tensioning device  2  and connector  5  being manipulated with a trocar. The contractile element  1  is formed in a loop about a hollow body organ such as a urethra by inserting connector  5  in the pass-through opening  63  of closure  6  and pulling on said connector until the proximal part  32   a  of the outer sheath at the flexible strip enters said closure  6 . This proximal part  32   a  corresponds advantageously to a setting section for adjusting the diameter of the contractile element about the urethra, and also to that of so-called dead-zone of the contractile element  1 , i.e. a zone that hardly contracts upon application of tensile force tension on wire  31  by an actuator. To set the diameter of contractile element  1  one simply needs to press tab  61  onto the proximal part  32   a  at the desired position so as to plug reinforcement elements  42  into locking slots  62  of closure tab  61 . This can be done easily with a trocar. 
     To help manipulation and hygiene during this operation the connector may advantageously be fitted with a screwable cap  56  having a tapered, corrugated, end for easing insertion in closure  6  and pulling with a trocar. When the diameter of contractile element  1  is set about the hollow body organ the surgeon pulls the connector  5  and transmission to a subcutaneous connection site where an actuator  7  is implanted and then said screwable cap  56  is manually unscrewed and connector  5  connected by push fitting it in actuator  7  as previously described. 
     A suitable actuator  7  (see  FIG. 5 ) with which the contractile element  1  is used may be an actuator corresponding to those disclosed in any of the documents WO13091730, WO13093074 or WO12000681, or any other convenient actuator.