Abstract:
A segmented arm support system and method for attachment to a surgical retractor includes an arm having a plurality of segments which can be joined together in frictional, locking engagement. In an unlocked state, the flexible arm can be manually positioned and the stabilization device placed over a localized area of tissue. Upon tightening of a cable running through the segments, the segments are brought together in frictional engagement. Each segment has a convex outer wall and a concave inner surface for attachment to adjacent segments. The segments are constructed of a stainless steel substrate material and coated with a high friction plating material to permit frictional engagement of the segments, thereby allowing for adequate tightening and locking of the arm.

Description:
FIELD OF INVENTION  
         [0001]    The present invention relates to surgical retractors and devices for stabilizing a predetermined area of the body during a surgical procedure, more particularly to surgical retractors and stabilizing devices used in connection with an improved segmented arm support system that is preferably used in coronary artery bypass grafting surgical procedures, and more specifically to a segmented arm apparatus that is used with various surgical retractors and stabilization devices for use in various surgical procedures.  
         BACKGROUND OF THE INVENTION  
         [0002]    Diseases of the cardiovascular system affect millions of people each year and are a cause of death for large numbers of people in the United States and throughout the world. A particularly prevalent form of cardiovascular disease involves a reduction in the blood supply to the heart caused by atherosclerosis (coronary artery disease) or other conditions that create a restriction in blood flow at a critical point in the cardiovascular system affecting blood flow to the heart.  
           [0003]    One technique for treating such a blockage or restriction is a surgical procedure known as a coronary artery bypass graft procedure, which is more commonly known as “a heart bypass” operation. The surgical correction of occluded or stenosed coronary arteries by means of bypass grafting is among the most common procedures performed today, especially when multiple grafts are needed.  
           [0004]    In the coronary artery bypass graft procedure, the surgeon either removes a portion of a vein from another part of the body for grafting or detaches one end of an artery and connects that end past the obstruction in the coronary artery while leaving the other end attached to the arterial supply. When using a vein from another part of the body, the surgeon installs this portion at points that bypass the obstruction. In both cases, the objective is to restore normal blood flow to the heart.  
           [0005]    In addition, when using this technique the surgeon makes a long incision down the middle of the chest, saws through the sternum, spreads the two halves of the sternum apart and then performs several procedures necessary to connect the surgical patient to a cardiopulmonary bypass machine to continue the circulation of oxygenated blood to the rest of the body while the heart is stopped and the graft is being sewn in place. Although such a procedure is one common technique for treatment, the procedure is lengthy, traumatic, costly and can damage the heart, the central nervous system, and the blood supply.  
           [0006]    Interventional techniques, such as percutaneous transluminal angioplasty (PTCA), have gained popularity as the methods of choice for therapy of atherosclerosis occlusions, for several reasons. The transluminal approach is a minimally invasive technique that subjects the patient to reduced trauma and reduced recovery time, especially when compared to bypass grafts which utilize homologous tissue, such as saphenous vein grafts. Also, the patient often suffers complications at the donor site of the graft that may be worse than the sternotomy and anastomosis.  
           [0007]    Although PTCA procedures are often successful, complications can arise, such as restenosis or thrombosis and embolism. Restenosed vessels often require surgical intervention for correction. The surgical correction of restenosis, like the conventional coronary bypass surgical procedure, requires the heart to be stopped and the patient placed on a heart/lung bypass machine during the procedure.  
           [0008]    In recent years, and in an effort to reduce cost, risk, and trauma to the patient, physicians have turned to minimally or less invasive surgical approaches to the heart, such as intercostal and endoscopic access to the surgical site. With such procedures, the heart is beating during the surgical procedure. Thus, there is no need for any form of cardiopulmonary bypass, and there is no need to perform the extensive surgical procedures necessary to connect the patient to such a bypass machine.  
           [0009]    Such attempts at performing minimally invasive bypass grafting on a beating heart, however, have been characterized as tedious, dangerous and difficult because of the delicate nature of the surgical procedure, the lack of adequate access through a reduced surgical field, and the lack of an ability to adequately stabilize and reduce tissue movement at the graft site. Because these procedures are performed while the heart muscle continues to beat, the blood continues flowing and the heart continues moving in three-dimensional movement while the surgeon attempts to sew the graft in place. Also, the surgical procedure to install the graft requires placing a series of sutures through an extremely small vessel and onto tissue that continues to move during the procedure. It is necessary that these sutures be fully and securely placed so that the graft is held firmly in position and does not leak.  
           [0010]    There is disclosed in U.S. Pat. No. 5,730,757 an access platform for the dissection of an internal mammary artery. The described access platform has first and second blades interconnected to a spreader member that laterally drives the blades apart or together, and support pads interconnected to the first blade. A torsional member is operably interconnected to the first blade and the spreader member, and is used to vertically displace the first blade in either direction, thus increasing the surgeon&#39;s working space and visual access for dissection of the internal mammary artery. A tissue retractor interconnected to the blades is used to draw the soft tissue around the incision away from the surgeon&#39;s work area. It is further provided that the access platform can include a port that can be used to mount a heart stabilizer instrument.  
           [0011]    There also is described in U.S. Pat. No. 5,875,782 granted to Ferrari et al.; U.S. Pat. No. 6,033,362 granted to Cohn; U.S. Pat. No. 6,102,854 granted to Cartier et al.; and U.S. Pat. No. 5,894,843 granted to Benetti et al. various devices for stabilizing a predetermined area on the heart or other organ of a patient, e.g., to enable a surgical procedure on the beating heart. These devices include various stabilization members and an elongated arm. The arm segments can be movably attached to a rib retractor so that a person is not required to hold the arm segment.  
           [0012]    There also is described in U.S. Pat. No. 5,836,311 granted to Borst et al. an apparatus for stabilizing a predetermined area on the heart or other organ of a patient, e.g., to enable a surgical procedure on the beating heart. The apparatus includes a single legged or bifurcated member having a plurality of suction members thereon which are attached to the surface of the heart using suction pressure. The arm portion of this device can be movably attached to a rib retractor or other surgical device so a person is not required to hold the arm segment and the suction device may be locked into position against the surface of the heart.  
           [0013]    U.S. Pat. No. 5,947,896 granted to Sherts et al. describes an articulating arm made up of segments/link members. In one particular embodiment therein (see FIGS. 41-49), an articulated arm is disclosed having a cable passing through link members and an “over-center” locking mechanism for tightening the cable. As is known to those skilled in the art, in such an articulating arm, the proximal link members are subjected to larger torques than more distal link members, due to large forces applied at the distal end that produce moment arms at the proximal end. Because the link members have identical dimensions and there is no mechanism provided to handle the additional torque acting on the link members at the proximal end, it is apparent that the proximal link members are not capable of absorbing the full amount of torque that is present upon tightening the cable. Accordingly, the degree of tightening that can be achieved in Sherts et al. is limited, and adequate stabilization cannot be assured. Moreover, in Sherts et al., only a small number of link members are provided, limiting the range of movement of the articulated arm.  
           [0014]    U.S. Pat. No. 5,899,425 to Corey, Jr. et al. describes a stabilizer with a flexible arm having a series of elements of progressively decreasing size from the proximal end to the distal end of the arm. Because larger elements are used at the proximal end, where the elements are subjected to larger torques, the arm is able to resist articulating movement in the locked state. However, use of the larger elements reduces flexibility in the arm in the unlocked state. Therefore, the range of movement and the available locking positions are limited.  
           [0015]    It is therefore desirable to provide a new system and devices related thereto for stabilizing a predetermined area of an organ such as the heart and methods for using such devices. It is particularly desirable to provide an articulating arm with sufficient flexibility to allow a large range of motion and a wide variety of positions, but one that is capable of adequately locking to assure stabilization during surgical procedures.  
         SUMMARY OF THE INVENTION  
         [0016]    The present invention features a system for retracting, stabilizing or manipulating a predetermined area of the body. The system includes a segmented arm system or apparatus and a tissue support or stabilization device, and methods of use related thereto.  
           [0017]    The segmented arm system and related devices and apparatuses that are featured herein are particularly advantageous for use in performing off-pump coronary artery bypass grafting procedures in which the heart remains beating during the surgical procedure and/or valve surgery where the heart is stopped. One advantage of the present invention relates to the versatile use of the segmented arm system which is connected to an arm or rack section of the retractor and also retains a stabilization device or surgical implement in a desired position. The use of the external rail system on the retractor allows a segmented arm apparatus to be attached to the retractor at any desired location and does not require that the segmented arm apparatus be slid on from an end of an arm or specially attached in certain specific locations. Additionally, the segmented arm system of the present invention allows for a full range of three-dimensional motion of the stabilization device or surgical instrument which is controlled by a single knob that is spaced apart from each of the retractor and the segmented arm apparatus. The segmented arm apparatus is also easily and conveniently manipulated by the surgeon and is movable so as not to obstruct the surgeon&#39;s view of the desired target location.  
           [0018]    The stabilization device preferably includes devices of the type commonly known as the Cohn Cardiac Stabilizer or the Immobilizer marketed by the Genzyme Corporation of Cambridge, Mass., although horseshoe or suction type devices may also be used. The preferred form of the stabilization device is a generally square, rectangular, or teardrop shaped member having a planar surface with centrally located opening therein. This opening is the area through which the surgeon performs the anastomosis or other procedure on the tissue of the beating heart. The stabilization device is preferably a multiple piece member so that once the anastomosis is completed, the pieces or an end portion thereof may be separated to remove the device from around the anastomosis. Flexible tapes can be sutured through the tissue and then threaded through the stabilizing device to provide temporary vessel occlusion. Once the stabilization device is positioned in the desired orientation and location in contact with the tissue, the flexible tapes are then pulled snug through the opening of the stabilization device to provide a system that captures the predetermined area of the tissue.  
           [0019]    The segmented arm system preferably includes an elongated articulating arm having a proximal mounting assembly for attachment to the retractor and a distal connector thereon for releasably connecting the stabilization device or surgical instrument to the articulating arm. The distal connector allows the stabilization device to be pivotally and slidably moved to a desired position into contact with the predetermined area of the tissue of the patient. The segmented arm system of this embodiment preferably includes a plurality of segments positioned along the length of the arm. The segments provide a plurality of locations for relative movement of the stabilization device as well as providing locations for fixing the desired position of the stabilization arm system along the retractor and relative to the stabilization device.  
           [0020]    Additionally, the movable segments allow the user to position at least a portion of the plurality of arm segments away from the desired surgical site so that the articulating arm does not obstruct the view of the surgeon or the assistant while providing sufficient leverage to provide a stable surgical site and to allow access to various locations on the heart of the patient. The segments each have approximately the same size and shape, are of low profile, and are capable of a large range of movement, allowing the articulating arm to be manually arranged in a desired position. Each segment preferably is made of a material with high stiffness (e.g., stainless steel) coated with a high friction material (e.g., nickel, gold, silver, tin, copper, or an elastomer).  
           [0021]    Other aspects and embodiments of the invention are more fully discussed below. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0022]    For a fuller understanding of the nature and desired objects of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawing figures wherein like reference character denote corresponding parts throughout the several views and wherein:  
         [0023]    [0023]FIG. 1 is a perspective view showing a segmented arm apparatus of the present invention;  
         [0024]    [0024]FIG. 2 is a partial exploded parts view of the segmented arm apparatus of FIG. 1, including the tightening assembly, mounting assembly, and one segment;  
         [0025]    [0025]FIG. 3 is a sectional view showing details of the tightening assembly and mounting assembly of the segmented arm apparatus;  
         [0026]    [0026]FIG. 4 is a partial exploded parts view of the distal assembly of the segmented arm apparatus;  
         [0027]    [0027]FIG. 5 is a sectional view showing details of the attachment of the stabilization device at the distal end of the segmented arm apparatus;  
         [0028]    [0028]FIG. 6 is an enlarged sectional view showing details of a plurality of segments of the segmented arm apparatus;  
         [0029]    [0029]FIG. 7 is a perspective view of the segments depicted in FIG. 6; and  
         [0030]    [0030]FIG. 8 is a cross-sectional view of one of the segments depicted in FIGS. 6 and 7. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0031]    [0031]FIG. 1 illustrates an example of a segmented arm apparatus  10  of the present invention. The segmented arm apparatus  10  includes a proximal mounting assembly  12  for attaching the apparatus to a surgical retractor (see FIG. 3). An elongated articulating arm  14  made up of a plurality of segments  16  is connected to the mounting assembly  12  at a distal end thereof, the articulating arm having a cable  18  (see, e.g., FIG. 2) received in a passage extending through approximately the middle of each segment. A tightening assembly  20  is attached to the proximal end of the mounting assembly  12  and connected to the cable  18  for tightening the cable and thus forcing the segments  16  of the articulating arm  14  into locking, frictional engagement.  
         [0032]    Attached to the distal end of the articulating arm  14  is a distal connector  21  for receiving a stabilization device  22 , e.g., a tissue stabilizer or other surgical instrument. The stabilization device  22  can fix or immobilize a section of tissue of an organ, such as the heart wall, when the articulating arm  14  is in a locked condition, for use in performing surgical operations.  
         [0033]    As shown in FIGS. 2 and 3, the mounting assembly  12  includes a mounting block  24  having a lip  26  and a mounting extension  28  to permit mounting of the segmented arm apparatus  10  on a retractor  30 . Details of the retractor and attachment of the segmented arm apparatus to the retractor is provided in U.S. Ser. No. 09/746,310, filed on Dec. 20, 2000, which application is incorporated by reference herein.  
         [0034]    The mounting assembly  12  of the present invention includes a cam  32  attached to the mounting block  24  by a threaded fastener or screw  34 . The screw  34  preferably receives a washer  36  to connect with a surface of the cam  32 , and the screw is threaded into a lever  38 , with the mounting extension  28  being sandwiched between the cam  32  and lever  38 . Because the lever is in contact with the cam  32  by an eccentric boss of the lever (not shown), rotation of the lever causes the cam  32  to move within mounting extension  28 . By rotating the lever between first and second positions, the cam can be adjusted laterally on a plane parallel to the mounting extension  28 , such that the cam moves toward or away from the retractor  30 . Thus, the mounting assembly of the present invention provides a simple arrangement for attaching the segmented arm apparatus to a retractor, allowing a surgeon to position and reposition the segmented arm apparatus as desired.  
         [0035]    The tightening assembly  20  is received in a bore  40  formed in the proximal end of the mounting block  24 . The bore  40  extends distally to form a narrow slot  42  for receiving therein a shaft portion  46  of an adjustment element  44 . The shaft portion  46  can be formed in a shape corresponding to the shape of the slot  42 . For example, the shaft can have a hexagonal shape to fit within a hexagonally-shaped slot  42 . Extending in a proximal direction from the bore  40 , the adjustment element  44  includes a threaded portion  48  that is generally of larger diameter than the shaft portion  46 , so that when the shaft portion  46  is engaged in the slot  42 , the threaded portion  48  remains positioned outside of the slot. The cable  18  extends through the adjustment element  44  and terminates beyond the proximal end of the adjustment element  44  with a crimp  50  preferably made of stainless steel or similar material. The adjustment element  44  and crimp  50  can be received within the adjustment knob  54 . The knob  54  contains a threaded fastener portion  52  adapted to engage the threaded portion  48  of the adjustment element  44 . Therefore, the adjustment element  44  and crimp  50  are received within the opening of the knob, and upon rotation of the knob, the crimp  50  and the cable can be tightened or released. The mechanism for tightening the cable and thereby forcing the segments of the articulating arm into locking, frictional engagement is discussed further below.  
         [0036]    With reference to FIG. 2, a mounting socket  60  is secured to the distal end of the mounting block  24  by threaded or non-threaded engagement with the mounting block  24 . The mounting socket  60  includes a lower (distal) surface  62  formed in a convex, generally spherical/cylindrical or crowned shape. The convex surface of the mounting socket is adapted to be received in a concave surface of a first segment  64  of the articulating arm  14 . The first segment  64  also is referred to herein as the most proximal segment of the arm  14 . Other segments  16  of the articulating arm  14  are connected in a similar ball-and-socket manner.  
         [0037]    As seen in FIG. 1, the articulating arm  14  includes a plurality of segments  16  each having approximately the same size and shape, adjacent segments being joined together in a ball-and-socket type configuration. Selected segments  16  of the articulating arm  14  are shown in greater detail in FIGS. 6 and 7. Each segment  16  includes a convex outer surface located at one end of the segment, shown herein as the distal end  72 , and a concave inner surface oriented in the opposite direction, i.e. opening toward the proximal end  70 . Thus, an outer surface (ball shape) of each segment  14  is configured and arranged in a mating relationship with an inner surface (socket shape) of an adjacent segment. Each segment  16  further includes an internal passage  74  for accommodating the cable  18 .  
         [0038]    The articulating arm  14  preferably includes approximately 20 to 40 segments, though more or fewer segments are also within the scope of the invention. In the example shown in FIG. 1, the arm includes 28 segments. Each segment preferably constitutes a substrate made of a material of high stiffness, preferably stainless steel, that is covered with a high friction plating material. For example, as seen in FIGS.  6  to  8 , segment  80  has a substrate  82  made of stainless steel and an outer plating material  84  covering the substrate A preferred plating material is nickel, although other metals can also be used in accordance with the invention, including but not limited to: gold, silver, tin, and copper. The plating material also can be formed of non-metal elastomers.  
         [0039]    By manually rotating the adjustment knob  54  in a clockwise direction (looking distally from the knob toward the stabilization device), a pulling force is exerted on the cable  18 , causing the cable to be placed under tension and thereby tightened. By tightening the cable, the segments  16  of the articulating arm  14  become locked together as a result of frictional forces exerted between connected segments. Segments closer to the proximal end of the articulating arm experience larger torques due to the larger forces applied to the distal end of the segmented arm apparatus  10 .  
         [0040]    In prior art segmented arm devices, in order to assure proper engagement of the segments, segments at the proximal end were sized larger than segments at the distal end. Such an arrangement is effective for producing locking engagement of the segments, but is undesirable for use in the present invention due to the large profile of segments located near the proximal end and the reduced flexibility of the articulating arm due to the larger segments.  
         [0041]    Therefore, in accordance with the present invention, and in order to prevent slippage and assure adequate locking engagement of the segments upon tightening of the cable, the segments are coated with a high friction plating material so that the segments frictionally engage each other upon tightening of the cable. An example of a hard, high friction plating material is nickel. An example of a soft, high friction plating material is an elastomer. When the segments are coated with a soft plating material, there is a prescribed amount of “bite” exhibited in adjacent segments upon tightening of the cable and engagement of the segments. This bite results from impact of the softer coating of adjacent segments, whereby the coatings of adjacent segments engage and become compressed against the harder underlying stainless steel substrates, allowing the plating material of adjacent segments to “bite” or be compressed together, and thereby leading to a tighter frictional engagement for obtaining sufficient locking of the segments at both the distal and proximal ends of the articulating arm. The segments still maintain an overall rigidity and stability due to the strength of the substrate stainless steel material present in each segment.  
         [0042]    By including a plurality of segments coated with a high friction material, the segments can be manufactured of approximately equal size. It is not necessary to include larger proximal segments, since the larger torques experienced at the proximal end of the segmented arm apparatus are counteracted by frictional, locking engagement of the segments. In the case of segments coated with a soft, high friction plating material, the plating material tends to compress against the harder stainless steel substrate. Therefore, the articulating arm  14  can be comprised of smaller, lower profile segments, as compared with prior art devices.  
         [0043]    [0043]FIGS. 4 and 5 illustrate a distal end of the segmented arm apparatus including the most distal segment  90  and the cable  18  extending through a passage in the segment  90 . The most distal segment  90  is received in a basin  95  formed in a proximal portion of a plunger  96 , the basin  95  having a generally concave surface to compliment the convex surface on the outside of the segment  90 . The distal end of the cable  18  terminates with a crimp  94  preferably made of stainless steel or similar material. The crimp  94  is received in a cable receptacle  92  which is accommodated within the plunger  96 .  
         [0044]    The plunger  96  is slidably disposed in a socket  102 , whereby a portion of the plunger  96  extending distally from the basin  95  is biased against a proximal portion of the socket  102  by a spring  98 , allowing the socket  102  to be compressed toward the basin  95 . A pin  106  extends through a slot  97  in the plunger  96  and a hole  93  in the cable receptacle  92 , and attaches to either side of the socket via hole  105 , thereby connecting the plunger  96 , cable  18 , and socket  102 . This type of attachment allows for longitudinal movement of the plunger within the socket.  
         [0045]    The distal connector  21  is formed at a distal end of the socket  102  and plunger  96 , the plunger  96  including a socket portion  104  preferably configured and arranged to receive a post  108  attached to the stabilization device  22 . The post  108  and distal connector  21  form a ball-and-socket connection, such that upon loosening of the adjustment knob  54 , the post  108  and thus the stabilization device  22  can be released from the segmented arm assembly through an opening  110  in a section of the socket  102 . Accordingly, the stabilization device  22  can be replaced easily and substituted for on the segmented arm apparatus.  
         [0046]    Various modifications and additions can be made to the herein described invention. For example, the articulating arm  14  preferably is covered with an outer sleeve made of a thermoelastomer or other biocompatible material, thereby protecting the patient from exposure to the plating material.  
         [0047]    Further modifications can include a force-releasing mechanism or mechanical stop positioned inside the knob to measure the force applied to the cable and prevent further rotation of the knob if the applied force exceeds a prescribed threshold.  
         [0048]    A low-pitch knob thread design (e.g., a turnbuckle-type mechanism with left- and right-handed concentric threads) can be implemented to provide a larger axial movement of the cable in response to each turn. Additional modifications to the knob design can include a drum with pawl and lever, a cam with a spring-loaded cable, or a three-bar linkage arrangement.  
         [0049]    Although a preferred embodiment of the invention has been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the spirit or scope of the following claims.