Abstract:
Surgical introducers aid surgeons in the implantation of medical devices. The introducer provides support and an even distribution of force for ease of insertion and prevention of damage to the medical device while protecting the tissue into which the device is implanted. A representative embodiment includes or consists of a locking device, a pair of forceps, a specially configured and/or angled head with a seat for the device to be implanted, and a gripping area.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority to and the benefits of U.S. Ser. No. 61/433,832, filed on Jan. 18, 2011, the entire disclosure of which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Medical treatment often requires the administration of a therapeutic agent (e.g., medicament, drugs, etc.) to a particular part of a patient&#39;s body. As patients live longer and are diagnosed with chronic and/or debilitating ailments, the likely result will be an increased need to place even more protein therapeutics, small-molecule drugs, and other medications into targeted areas throughout the patient&#39;s body. Some maladies, however, are difficult to treat with currently available therapies and/or require administration of drugs to anatomical regions to which access is difficult to achieve. 
         [0003]    A patient&#39;s eye is a prime example of a difficult-to-reach anatomical region, and many vision-threatening diseases, including retinitis pigmentosa, age-related macular degeneration (AMD), diabetic retinopathy, and glaucoma, are difficult to treat with many of the currently available therapies. For example, oral medications can have systemic side effects; topical applications may sting and engender poor patient compliance; injections generally require a medical visit, can be painful, and risk infection; and sustained-release implants must typically be removed after their supply is exhausted (and generally offer limited ability to change the dose in response to the clinical picture). 
         [0004]    Another example is cancer, such as breast cancer or meningiomas, where large doses of highly toxic chemotherapies, such as rapamycin, bevacizumab (e.g., Avastin), or irinotecan (CPT-11), are typically administered to the patient intravenously, which may result in numerous undesired side effects outside the targeted area. Other examples of difficult-to-reach anatomical regions for drug delivery include the knee, where drugs often have difficulty penetrating the avascular cartilage tissue for diseases such as osteoarthritis, the brain, and the spine. 
         [0005]    Implantable drug delivery systems may include a refillable drug reservoir, a cannula for delivering the drug, etc., and generally allow for controlled delivery of pharmaceutical solutions to a specified target. This approach can minimize the surgical incision needed for implantation and typically avoids future or repeated invasive surgery or procedures. In a typical procedure, the pump is implanted using an instrument specifically adapted for the purpose. 
         [0006]    Instruments (“introducers”) for surgically implanting medical devices tend to have limited capabilities, however. Many implants are difficult to maneuver due to the typically smooth design necessary for implantation in the body, and some devices currently used in surgery can cause damage to the delicate external components of the implant. Surgery may be postponed if the device is damaged by the instrument or slips outside the sterile field due to lack of grip on the device. Medical devices that are inserted into the body are often saturated in sterile water before implantation, further complicating the ability to grip an already smooth (and possibly rounded or even spherical) implant. Many implants also have parylene coatings on the outside, and this layer can also be damaged by contact with the introducer. Finally, polymeric introducers may be subject to buildup of electrostatic charge, which can damage an electronic implantable device. 
       SUMMARY OF THE INVENTION 
       [0007]    Embodiments of the present invention aid surgeons in the implantation of medical devices. The introducer provides support and an even distribution of force for ease of insertion and prevention of damage to the medical device while protecting the tissue into which the device is implanted. While the introducer can be used for many types of implants (e.g., drug pumps, pacemakers, or other neural stimulators), embodiments of the invention can be particularly helpful in the insertion of implants that are delicate in nature (e.g., microelectronic devices or infusion pumps with flexible cannulas) or very small devices that are difficult to manipulate with hands or surgical tweezers (e.g., implantable periperhal nerve stimulators or intraocular drug pumps). 
         [0008]    A representative embodiment of the invention includes or consists of a locking device, a pair of forceps, a specially configured and/or angled head with a seat for the device to be implanted, and a gripping area. The device may also include application-specific markings to aid the surgeon in measurement and an illumination source. The head members, when united around an implantable device, may be shaped to follow the contours of the device and to slide easily between small spaces (e.g., the subconjunctival space) without causing damage to delicate tissue. 
         [0009]    Accordingly, in a first aspect, the invention relates to a tool or instrument facilitating surgical implantation of an implantable device. In various embodiments, the instrument comprises first and second of forceps arms each having first and second ends; the arms are joined at the first ends thereof and are arranged to oppose but permit resisted compression of the arms toward each other. A first-arm head member is located at the second end of the first arm and a second-arm head is member located at the second end of the second arm. The head members are angled away from each other relative to an axis running between and coplanar with the arms, and are shaped to releasably engage the implantable device upon compression of the arms. 
         [0010]    The instrument may further comprise a releasable catch for maintaining the arms in a compressed configuration; for example, the catch may be operable by a thumb-engageable slide disposed on the first arm. In some embodiments, the slide is slidable along an angled path relative to the first arm. In other embodiments, instead of a releasable catch, the instrument comprises a finger-operable rotation member affixed to a leadscrew along an axial length thereof; the leadscrew passes through threaded openings in the first and second arms such that rotation of the rotation member alters a distance between the arms. The finger-operable rotation member may be disposed between the arms. 
         [0011]    In some embodiments, the instrument comprises depth markings along the first arm indicating a distance from a terminus of the heads. The second-arm head may have an angled curvature that is complementary to an internal anatomical contour, e.g., an ocular orbit. The head members have opposed surfaces for releasably engaging the implantable device upon compression of the arms, and these surfaces may have a texture and/or a polymeric coating providing stiction with the implantable devices to discourage movement thereof. In some embodiments, at least the head members are coated with a biocompatible polymer (e.g., parylene). The biocompatible polymer may, in some cases, be infused with a drug. 
         [0012]    Some embodiments also feature means for reducing or preventing damage due to the buildup of electrostatic charge on the instrument; electrostatic discharge (ESD) can damage or destroy delicate electronic circuitry. In one embodiment, the introducer is made from or coated with an electrically dissipative material, e.g., a conductive polymer or a polymer loaded with a conductive pigment, such as carbon black; a suitable commercial example is the TECAFORM SD material. Although such a material is not highly conductive, charge cannot build up on its surface. Because the clinician will typically be grounded, an ESD-safe introducer is desirably retained on a grounded (e.g., through a conductive (0Ω) or dissipative (e.g., 1 MΩ) instrument tray when not in use. Alternatively, a conductive wire may connect the introducer to ground. 
         [0013]    In another aspect, an instrument according to the invention comprises, in various embodiments, first and second of forceps arms each having first and second ends, the arms being pivotable at the first ends thereof; a first-arm head member located at the second end of the first arm; a second-arm head member located at the second end of the second arm; and a finger-operable rotation member affixed to a leadscrew along an axial length thereof. The leadscrew passes through threaded openings in the first and second arms such that rotation of the rotation member alters a distance between the arms. The head members are angled away from each other relative to an axis running between and coplanar with the arms, and are shaped to releasably engage the implantable device upon compression of the arms. The rotation member may be aligned with the axis. 
         [0014]    In still another aspect, the invention pertains to a combination comprising an implantable device and, retained therein, a instrument facilitating its surgical implantation. In various embodiments, the combination comprises first and second forceps arms each having first and second ends, the arms being joined at the first ends thereof and arranged to oppose but permit resisted compression of the arms toward each other; a first-arm head member located at the second end of the first arm; a second-arm head member located at the second end of the second arm; and an implantable medical device. The head members are angled away from each other relative to an axis running between and coplanar with the arms, and releasably engage the implantable device. 
         [0015]    The terms “substantially” and “approximately” mean±10% (e.g., by weight or by volume), and in some embodiments, ±5%. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0016]    The foregoing will be more readily understood from the following detailed description, in particular, when taken in conjunction with the drawings, in which: 
           [0017]      FIG. 1  is a perspective view of an introducer in accordance with an embodiment of the present invention; 
           [0018]      FIG. 2  is an exploded view of the embodiment shown in  FIG. 1 ; 
           [0019]      FIG. 3  is a close-up elevation showing an angled travel path for the thumb-engageable slide shown in  FIG. 2 ; 
           [0020]      FIG. 4  is another perspective view of the introducer shown in  FIG. 1 , here in a partially closed position; 
           [0021]      FIGS. 5A and 5B  illustrate a gear wheel with a threaded rod for precisely opening or compressing the forceps arms; and 
           [0022]      FIG. 6  is a close-up view from the bottom showing an implantable device grasped by the introducer. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Refer first to  FIG. 1 , which illustrates an introducer  100  in accordance with an embodiment of the invention. The introducer  100  includes two forceps arms  105   a ,  105   b  joined at one end thereof. The arms may be made of a metal (such as steel or titanium) or a disposable plastic (such as polyethylene or polystyrene), and are angled away from the joined ends so that they naturally assume an open position and, due to the joined ends, yieldingly resist compression in the manner of tweezers—i.e., the arms  105   a ,  105   b  exhibit a preloaded amount of resilient force that permits controlled compression by the user without excessive effort, but also with sufficient resistance to avoid unintended collapse. In some embodiments, this resilient force is provided or enhanced by a spring (not shown) between the arms  105   a ,  105   b.    
         [0024]    The unjoined ends of the arms  105   a ,  105   b  terminate in complementary head members  110   a ,  110   b . These head members  110  typically flare outwardly and are configured to engage the device to be implanted, as described below. The introducer  100  may include a locking mechanism that retains the arms  105   a ,  105   b  in the compressed configuration. With reference to  FIGS. 1 and 2 , the locking mechanism may be a releasable catch operable by means of a thumb-engageable slide  115 . The slide  115  includes a depression  117  shaped to receive the user&#39;s thumb and is slidably mounted for travel along, and parallel to, arm  105   a . The forward end  119  of the slide may be knurled or ribbed for further engagement with the user&#39;s thumb. As shown in  FIG. 2 , slide mounting may achieved using an inverted T member  122  depending from the underside of the slide  115 , and which engages a slot  125  in arm  105   a . The shank of T member  122  extending from slide  115  travels within slot  125 , and the crosspiece of the T member travels along the underside of arm  105   a  and prevents disengagement of slide  115  therefrom. Extending from the forward end  119  of the slide  115  are a pair of rails  128 . As slide  115  travels forward, rails  128  pass over an aperture  130  through arm  105   a . A post  135  is mounted on, and projects upwardly from, arm  105   b  below aperture  130 . The post  135  includes a narrow (smaller-diameter) neck segment  137  and a wider cap or flange  140  thereabove. When the arms  105   a ,  105   b  are compressed, a portion of post  135  including the neck  137  and cap  140  passes through the aperture  132  through arm  105   a . The rails  122  are spaced apart by a distance greater than the diameter of neck segment  137  of post  135  but less than the diameter of the cap  140 , so that the rails slide along the neck segment  137  and engage the underside of cap  140  when the arms  105   a ,  105   b  are released. 
         [0025]    As shown in  FIG. 3 , the slide  115  can, if desired, be configured for slow release by traveling at an angle to arm  105   a  rather than directly parallel thereto—for example, along a wedge  145  mounted on arm  105   a . In this way, the rails  122  rise relative to the flat surface of arm  105  as the slide  115  is pushed forward, thereby squeezing the arms  105   a ,  105   b  together as the rails engage the post  135 ; as the slide  115  is retracted, the arms are allowed to gradually open. Expansion of the arms is thereby limited by the position and travel of slide  115 , even if the user suddenly releases the arms. 
         [0026]    As shown in  FIGS. 4 and 5 , the head members  110   a ,  110   b  have shapes complementary to the implantable device D that the instrument will handle. For example, the device may be an implantable drug pump as described, e.g., in U.S. Patent Publ. No. 2006/0258994, entitled “Implantable delivery device for administering pharmacological agents to an internal portion of a body,” the entire disclosure of which is hereby incorporated by reference. Ideally there will be one or more convex elements along the contour of the device D—such as the refill port  160 —that mates with a complementary recession  162  in one of the head members  110 , thereby preventing the device D from slipping out of the instrument  100  without excessive clamping force being applied to the device D. As further described below, the instrument  100  may include features that restrict the closure of arms  105 , thereby limiting the clamping force. When united, the head members  110  should slide easily between small spaces (e.g., the subconjunctival space) without causing damage to delicate tissue. Furthermore, head members  110   a ,  110   b  can be fashioned in different configurations, e.g., formatted to allow opening and closing in a longitudinal or axial orientation to improve ease of use. Optionally, markings at specific distances (e.g., in millimeter increments indicative of the distance to the distal edge of the heads  110 ) can be applied to one or both of the arms  110  to guide the surgeon in determining when the device D has reached its optimum or required depth. With a slight movement of the thumb, the surgeon may readily release the locking mechanism as described above, allowing the introduced device D to stay in place while the introducer  100  is removed. 
         [0027]    The head members  110   a ,  110   b  may have textured or tacky interior surfaces (i.e., the surfaces that make contact with the device D). Most simply, a suitable polymeric coating such as silicone may be applied to the head members  110   a ,  110   b  (or just the interior surfaces thereof) and cured (or merely allowed to dry) to form a coating with the desired stiction to discourage movement of the device D. Alternatively, the heads  110  and, indeed, the entire introducer  100  can be coated with a biocompatible material (e.g., parylene) for an optimized smooth interface, since many implants are difficult to maneuver due to the typical smooth design necessary for implantation. Further, these coatings may be infused with application-specific drugs (e.g. anti-inflammatory, anti-infective drugs). A coating may be applied to the head  110  and/or the arms  105  by dip coating, spray coating, manual painting, or any other suitable application technique. 
         [0028]    Once the medical device is in place, the introducer can easily be released and removed (either before or after suturing). The introducer may provide means for the surgeon to precisely place sutures in optimal places along the implant. Furthermore, the introducer may be angled as necessary to accommodate the implant and the surgeon&#39;s needs simultaneously. For example, in the case of an implantable drug pump, the introducer may be configured to hold the pump in aseptic conditions, facilitating filling in the operating room and allowing the surgeon to hold the pump steady during the initial fill process. Moreover, the instrument may be prepackaged with the implant, which allows the operator to fill the device in the operating room. A dilator may be used in combination with the introducer. 
         [0029]    As described above, the introducer  100  may operate by compression and release, or may have a restriction mechanism—such as an angled travel path for the slide—that allows movement of the slide rather than squeezing or release of the arms to dictate the rate of compression or release. To provide further precision in controlling the spread of arms  105   a ,  105   b , the locking mechanism described above may be replaced with a finger-operated leadscrew  175 , as illustrated in  FIGS. 5A ,  5 B. Located, for example, where post  135  would otherwise be placed, the leadscrew  175  threadably engages opposed bores through the arms  105   a ,  105   b . A thumbwheel, gear or polygonal nut  180  allows the user to rotate the leadscrew  175  with her thumb or other finger, thereby expanding or reducing the distance between the arms  105   a ,  105   b  depending on the direction and extent of rotation. The threading pitch can be selected to facilitate a desired rate of opening and closing (relative to rotation of the leadscrew), and the threading on the leadscrew  175  can terminate at desired locations proximal and distal to the thumbwheel  180  in order to limit the degree of allowed closing and opening of the arms  105   a ,  105   b , preventing damage to the implant and tissue surrounding the implant, respectively. With this mechanism, the arms  105  need not be joined in a manner that produces resistance to compression; the arms  105  may, instead, simply be hinged. As shown in  FIG. 6 , the head members  110   a ,  110   b  should unite snugly around the device D but must not apply a damaging force thereto. Other mechanisms to control the opening and closing of the arms  105  include a button, clip, or other comparable mechanism. 
         [0030]    Good manufacturing procedures, particularly those relating to the head members  110 , are critical. The head members must precisely conform to the medical device they are designed for and avoid damage to surrounding tissue during implantation. Accordingly, burrs or sharp edges should be minimized or eliminated during the manufacturing process. In one representative procedure, a flat piece is stamped out of a thin sheet of stainless steel. Next, a series of tools is used to shape the head members  110  in an incremental fashion, and if desired, the head members are coated as described above. 
         [0031]    Although the present invention has been described with reference to specific details, it is not intended that such details should be regarded as limitations upon the scope of the invention, except as and to the extent that they are included in the accompanying claims.