Patent Publication Number: US-2018042633-A1

Title: Endoscopic Surgical Devices and Other Surgical Devices

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to surgical instruments, especially endoscopic surgical instruments, and is particularly related to surgical tools and procedures which can be used for the release of the transverse carpal ligament, as well as in other applications. 
     BACKGROUND OF THE INVENTION 
     Examples of surgical tools which are useful for inspecting and manipulating tissues (e.g., cutting of the transverse carpal ligament) in a body cavity are described in U.S. Pat. No. 4,962,770 to Agee; U.S. Pat. No. 4,963,147 to Agee; U.S. Pat. No. 5,089,000 to Agee, U.S. Pat. No. 5,306,284 to Agee, and U.S. Pat. No. 7,918,784 to Wellborn et al. (Microaire Surgical Instruments, Inc.). Endoscopic instruments are used in well-established surgical procedures, such as for the release of the transverse carpal ligament. The devices include a cutting assembly for the dissection of the ligament and an endoscope with a camera system for visualization. 
     However, the endoscopic instrumentation currently in commercial usage is not completely free of any disadvantage or shortcoming and seemingly certain disadvantageous aspects are inherent to usage of endoscopic instrumentation. For example, the reason that patients undergo carpal and cubital tunnel releases is because the tissue in these regions is compressing the median and ulnar nerves, causing pain and numbness and loss of function. An endoscopic surgical device is used to cut ligaments and tissues to relieve that pressure. But, by inserting the device to perform the surgery, the device increases the pressure on the nerve, even for just the 5 minutes needed to perform the procedure, which can bring about potential additional pain and other temporary complications. 
     Another aspect of endoscopic instrumentation currently in widespread use is that the visualization aspect does have limitations that would seem to be unavoidable or not readily addressed practically. For example, when working with light from an endoscope and the endoscope&#39;s lens within a body cavity, moisture and light reflection on metal surfaces seemingly inevitably will complicate visibility. Some in the industry have taken a direction of trying to reduce unwanted light reflection and glare off of the metal surfaces of the instrumentation by rough-blasting the metal surfaces so that they are less like mirrors. But roughened surfaces in medical instrumentation that is to be sterilized for reuse may not be well-received, in that a non-smooth surface may be considered more uncertain to fully clean compared to a smooth surface. 
     Another aspect of visualization with existing endoscopic instruments is that movement (especially rotational movement) of the blade case within the patient has been needed to orient the endoscope&#39;s lens to achieve the desired image. While a user might, in the abstract, theoretically want to be able to achieve a desired visual image without moving the blade case inside the patient, with the current instrumentation, without rotation and movement of the blade case within the patient, no useable visual view is captured. 
     Also, a blade case of current endoscopic instrumentation occupies a certain space within the patient and when that space is needed for another surgical tool that needs that space to perform its respective function, the blade case must be removed and reinserted. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to address the above-mentioned disadvantages and shortcomings of existing endoscopic surgical tools. 
     It further is an object of the invention to provide an endoscopic surgical tool relatively unsusceptible to difficulties with glare and reflected light. 
     It is another object of the invention to provide an endoscopic surgical tool with minimized needs to be rotated inside a patient to achieve visualization. 
     Also it is an object of the invention to provide an endoscopic surgical tool that can remain inside a patient in contexts where previous endoscopic surgical tools would need to be removed to make way for another surgical instrument and then reinserted when the space was again made available by removal of that other instrument. 
     The invention in a preferred embodiment provides a surgical device, comprising a blade case, wherein an interior surface of the blade case is light-absorbing, such as, e.g., inventive surgical devices in which the interior surface of the blade case has a black color; inventive surgical devices wherein the interior surface of the blade case has a dark color; inventive surgical devices wherein the blade case comprises a black plastic solid shape; inventive surgical devices wherein the interior surface comprises a black plastic; and other inventive surgical devices. 
     In another preferred embodiment, the invention provides a surgical device comprising an interior surface on which light will be shined during surgery, wherein the interior surface belongs to a component selected from the group consisting of a cannula and a blade case; and wherein the interior surface is light-absorbing (such as, e.g., an interior surface that comprises a light-absorbing material). 
     The invention in another preferred embodiment provides a surgical device (such as, e.g., an endoscopic device) comprising an interior surface on which light will be shined during surgery, wherein the interior surface belongs to a component selected from the group consisting of a cannula and a blade case; and wherein the interior surface is not light-reflecting. 
     Referring to another preferred embodiment, the invention provides a method of constructing a surgical device (such as, e.g., an endoscopic surgical device), comprising: for a surface of the surgical device on which light will be shined during surgery, constructing the surface as a light-absorbing surface, such as, e.g., inventive methods wherein the light-absorbing surface is constructed without performing a step of rough polishing or grit-blasting metal; inventive methods wherein the constructing step comprises applying a black or dark surface layer; inventive methods wherein the light-absorbing surface is integral with a component formed from a black material or a dark material; inventive methods wherein the constructing step comprises applying a black material or dark material as a thin layer onto a material which is not light-absorbing; inventive methods wherein the constructing comprises forming a non-layered integral part from a black material or a dark material, wherein the light-absorbing surface is a top surface of the black material or dark material; inventive methods wherein the constructing comprises forming a starting material into a shape that when cooled and hardened is a black plastic solid; inventive methods wherein the surface comprises a surface of a blade case. 
     The invention in another preferred embodiment provides a surgical device (such as, e.g., an endoscopic surgical device), comprising: a windowed blade case comprising at least one window, the blade case having a size that accommodates passage therein of an endoscope, such as, e.g., inventive surgical devices wherein the blade case is opaque; inventive surgical devices wherein the at least one window is positioned at a tip of the endoscope; inventive surgical devices wherein the endoscope is rotatable; inventive surgical devices wherein the at least one window comprises exactly one window; inventive surgical devices wherein the at least one window comprises two windows; inventive surgical devices wherein the at least one window comprises three windows; inventive surgical devices wherein the at least one window comprises a first window and a second window, wherein the first window and the second window differ as to one or both of size and shape; inventive surgical devices wherein the at least one window is defined by a clear solid section; inventive surgical devices comprising a first window disposed on a first side of the blade case, a second window disposed on a second side of the blade case, and a third window disposed on a bottom surface of the blade case; and other inventive surgical devices. 
     In another preferred invention, the invention provides a method of operating an endoscope, comprising steps of: during surgery on a patient, positioning a windowed blade case inside the patient, wherein the windowed blade case comprises at least a first window (such as, e.g., a first window that comprises open space; a first window that comprises clear plastic); through the first window, performing a certain step. 
     The invention in another preferred embodiment provides a surgical device (such as, e.g., an endoscopic device), comprising: a blade case comprising a clear first section (such as, e.g., a clear first section having a length dimension in a range of about 2.0-3.5 inches; a width dimension in a range of about 0.15-0.25 inches; and a thickness dimension in a range of about 0.010-0.025 inches) and a light-absorbing second section; such as, e.g., inventive surgical devices wherein the clear first section is a top section of the blade case and the light-absorbing second section is a bottom section of the blade case. 
     In another preferred embodiment, the invention provides a method of previewing tissue to be cut during surgery (such as, e.g., carpal tunnel release surgery; cubital tunnel release surgery; endoscopic surgery; arthroscopic surgery; minimally invasive surgery (e.g., minimally invasive surgery where no dermal incision exceeds about 3 cm; minimally invasive surgery where dermal incisions are in a range of about 1-1.5 cm; etc.), the method comprising: previewing the tissue to be cut through a window of a blade case or a cannula; such as, e.g., inventive methods wherein the previewing step is performed without inserting and removing the blade case or cannula multiple times; inventive methods wherein the blade case or cannula is opaque; inventive methods wherein the window is located at a top of the blade case or cannula; inventive methods further comprising, when previewing is performed, moving the endoscope up and down a length of the tissue to be cut; and other inventive methods. 
     The invention in another preferred embodiment provides a surgical device (such as, e.g., an endoscopic device) comprising: a blade case comprising at least one concavity on an exterior surface thereon, such as, e.g., inventive surgical devices wherein the at least one concavity extends lengthwise along the exterior surface of the blade case; inventive surgical devices wherein the blade case is a flanged blade case, comprising at least one external wall that is concave; inventive surgical devices comprising a set of external walls that are concave; inventive surgical devices comprising an external sidewall that is concave; inventive surgical devices comprising at least two external sidewalls that are concave; inventive surgical devices wherein exactly two concave external sidewalls are included (such as, e.g., inventive surgical devices further comprising a non-concave top wall and a non-concave bottom wall); inventive surgical devices comprising an external bottom wall that is concave (such as, e.g., inventive surgical devices wherein the non-concave top wall has a flat surface); etc. 
     In another preferred embodiment the invention provides a surgical device (such as, e.g., an endoscopic device) comprising a blade case ending in an edged tip, wherein the edged tip comprises a scraper that extends along a longitudinal axis of the blade case, the scraper being integrally a part of the blade case; such as, e.g., inventive surgical devices in which the scraper is defined by a shape selected from the group consisting of a flared shape; a protrusion; and a swept ridge; inventive surgical devices wherein no blade is included in the edged tip; inventive surgical devices wherein the edged tip is rounded; etc. 
     The invention in another preferred embodiment provides a method of using a surgical device, comprising the step of: scraping synovium during endoscopic carpal tunnel surgery, wherein the scraping is performed by the surgical device, and the surgical device is also useable for splitting muscle near fascia present during endoscopic cubital tunnel surgery; such as inventive methods further comprising splitting muscle near fascia present during endoscopic cubital tunnel surgery, wherein the muscle-splitting is performed by the same surgical device that performs the synovium-scraping; etc. 
     In another preferred embodiment, the invention provides a method of clearing tissue in endoscopic carpal tunnel surgery, comprising: scraping synovium away by bringing an edged tip of a blade case in contact with the synovium, while an endoscope is in place illuminating the synovium during the scraping step; and/or splitting muscle for cubital procedures by contacting the edged tip of the blade case with the muscle. 
     Referring to another preferred embodiment, the invention provides an endoscopic surgical device, comprising: a blade; a blade case that in an unused condition is attachable to a first handpiece; and a releasable blocking tab that moves between two positions (such as, e.g., a releasable blocking tab that is located on the blade case; a releasable blocking tab that is released by ejection of the blade case from the handpiece, wherein the released tab forms a physical block sized to prevent the blade case from being reattached to the first handpiece or attached to a second handpiece; etc.). 
     The invention in another preferred embodiment provides an endoscopic surgical device, comprising: a blade; and a usage indicator, wherein before the blade is used for a first time, the usage indicator occupies an internal position unseen by one viewing the surgical device, and upon the blade being used for the first time, the usage indicator moves to an external position that can be seen by one viewing the surgical device. 
     In another preferred embodiment, the invention provides an endoscopic surgical device, comprising a blade case, wherein the blade case is selected from the group consisting of: (1) a blade case that occupies a volume less than 4 cm 3 , and/or has a cross-section not more than 0.36 cm 2  and/or has a height not more than 0.54 cm; (2) a blade case, wherein the blade case occupies a volume less than 4 cm 3 ; (3) a blade case, wherein the blade case has a cross-section not more than 0.36 cm 2 ; (4) a blade case, wherein the blade case has a height not more than 0.54 cm, (5) a blade case, wherein the blade case occupies a maximum external volume per unit length less than 0.055 in 2 , with a height to width ratio less than 80%, such as, e.g., inventive endoscopic surgical devices in which the blade case occupies a volume of not more than 3.41 cm 3 ; inventive endoscopic surgical devices in which the blade case has a height not more than 0.54 cm; inventive surgical devices comprising a flange; inventive surgical devices comprising a blade case having a length of at least about 9 cm; etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be appreciated by reference to the figures, which are not necessarily drawn to scale: 
         FIGS. 1-1A  are perspective views of an exemplary surgical device  1  according to the invention, comprising blade  100  in, respectively, retracted position ( FIG. 1A ) and raised position ( FIG. 1B ). 
         FIGS. 2-2A  are cross-sectional views of blade case  2  according to the invention useable in surgical device  1  of  FIG. 1 , depicting a hollow interior circular section defined by interior surface  3  of blade case  2 . 
         FIG. 3  is a lengthwise cross-sectional view of a blade case  12  according to the invention, useable in surgical device  1  of  FIG. 1 . Blade case  12  has length  12 L. 
         FIG. 3A  is lengthwise cross-sectional view of blade case  12  of  FIG. 3  rotated 90 degrees about the lengthwise  12 L axis, showing window  11 . 
         FIG. 3B  is a close-up perspective view of windows  7 ,  9 ,  11  ( FIGS. 3-3A ) in blade case  12  as a top view. Light cone  10  emanates from the endoscope in a straight up, standard position. 
         FIG. 3C  is a close-up perspective view corresponding to  FIG. 3B , as a side view. Light cone  10 ′ emanates from the endoscope rotated 45 degrees to one side, to view side tissue. 
         FIG. 3D  is a close-up perspective view corresponding to  FIGS. 3B-3C , as a bottom view. Light cone  10 ″ emanates from the endoscope rotated 180 degrees to view tissue beneath the blade case  12 . 
         FIG. 4  is a cross-sectional view of a clear-topped blade case  22  according to the invention, useable in surgical device  1  ( FIG. 1 ) and having blade case length  22 L. 
         FIG. 4A  is a width-wise cross-sectional view of the blade case  22  of  FIG. 4 . 
         FIG. 5  is a lengthwise cross-sectional view of a clear-bottomed blade case  23  according to the invention, useable in surgical device  1  ( FIG. 1 ) and having blade case length  23 L. 
         FIG. 5A  is a width-wise cross-sectional view of the blade case  23  of  FIG. 5 . 
         FIG. 6  is a lengthwise cross-sectional view of a flanged blade case  32  useable in surgical device  1  ( FIG. 1 ) and having blade case length  32 L. 
         FIG. 6A  is an enlarged width-wise cross-sectional view of flanged blade case  32  ( FIG. 6 ). 
         FIG. 6B  corresponds to  FIG. 6A , and depicts concavity depth  16 D. 
         FIG. 7  is a cross-sectional view of ridges  21  formed into a concavity on an exterior surface of a blade case in an embodiment of the invention. 
         FIG. 8  is a cross-sectional view of a hooked edge  24  formed into a concavity on an exterior surface of a blade case in an embodiment of the invention. 
         FIG. 9  is a top view of a scraper-tipped blade case  42  useable in surgical device  1  ( FIG. 1 ) and having blade case length  42 L. 
         FIG. 10  is a side view of blade case  42  ( FIG. 9 ) comprising scraper tip  40  according to the invention. 
         FIG. 10A  is an enlarged view including scraper tip  40  from  FIG. 10 . 
         FIG. 11  is an exploded perspective view in an inventive embodiment of parts comprising main blade case body  50 , windows  7 ,  9 ,  11  ( FIGS. 3-3A ), a clear top  4  of the blade case, a clear bottom  4 A of the blade case, a concave exterior surface  16  of the blade case, and a scraper tip  40 . 
         FIG. 11A  is an assembled perspective view corresponding to  FIG. 11 , depicting a surgical device according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
     The invention provides for certain advances and improvements in surgical tools, surgical devices, and methods of using such surgical tools and devices. In the invention, a preferred example of a surgical device is a surgical device (such as surgical device  1  in  FIG. 1 ) comprising an endoscopic device, also referred to as “an endoscopic surgical device”. The invention particularly improves upon surgical devices comprising a blade case (such as blade case  2  in  FIG. 2 ), such as endoscopic devices comprising a blade case. Using combinations of the innovations provided herein is preferred but not mandatory. 
     For the interior surface  3  of the blade case  2 , a light-absorbing interior surface is particularly preferred. Examples of a “light absorbing” surface are, e.g., a surface having low reflectance; a surface having low reflectivity; a surface having low albedo; a non-reflective surface; a surface having a measured light reflectance value≦20% when visible light is shined thereon; etc. By a measured light reflectance value when visible light is shined thereon, we are referring to the light reflectance that is measured upon shining visible light in a range of 400-700 nm by an endoscopic instrument set to full intensity. The most preferred examples of a light absorbing surface for use in the invention are a black surface or a dark surface. 
     For the blade case  2 , a windowed blade case (such as windowed blade case  12  in  FIGS. 3-3D  comprising windows  7 ,  9 ,  11 ) is particularly preferred, with a set of three windows being a most preferred configuration. 
     For the set of three windows  7 ,  9 ,  11 , a preferred example of the first window  11 &#39;s dimensions is about 0.1-0.3 inches long by 0.05-0.1 inches wide, with the second and third windows  7 ,  9  each respectively being about 0.2-0.5 inches long by 0.05-0.1 inches tall. In another example, the first window has a length dimension about 7 mm and a width dimension in a range of about 1.5-2 mm, and the second window and third window have a length dimension about 7 mm and a width dimension in a range of about 1.5-2 mm. 
     Referring to  FIGS. 3A-3D , light cones  10 ,  10 ′,  10 ″ are depicted in a context of window  11  and windows  7 ,  9 . Light cones  10 ,  10 ′,  10 ″ indicate the visual cone of the endoscope in three different positions. 
     Windows  7 ,  9 ,  11  are easily constructed such as by cutting holes through blade case  12  on the sides and bottom. 
     Through windows  7 ,  9 ,  11 , soft tissue anatomy is viewable during surgery (with a rotating endoscope). 
     For blade case  2 , a clear-topped blade case such as blade case  22  ( FIGS. 4-4A ) is preferred. Clear top  4  in blade case  22  allows visualization via endoscope along an entire length  22 L of blade case  22 . 
     For blade case  2 , a clear-bottomed blade case such as blade case  23  ( FIGS. 5-5A ) is preferred. Clear bottom  4 A allows visualization via endoscope along the entire length  23 L of blade case  23 . 
     Preferably blade case  2  is both clear-bottomed and clear-topped. 
     For constructing body  5  of blade case  22  and body  5 A of blade case  23 , preferably a relatively stronger opaque material is used. Top  4  and bottom  4 A are constructed from clear material that allows visualization via an endoscope as the endoscope is moved along lengths  22 L,  23 L of blade case  22 ,  23 . The combination of materials used for top  4  and body  5  (and bottom  4 A and body  5 A) is selected to maintain stiffness of the opaque design while allowing greater visualization than if top  4  (and bottom  4 A) were not clear. An example of a range of thickness for clear top  4  or bottom  4 A is about 0.020-0.040 inches thick. 
     For blade case  2 , a flanged blade case such as blade case  32  ( FIGS. 6-6B ) is preferred. In  FIG. 6A , the linear profile  6  of blade cases of currently-sold endoscopic instrumentation is shown as dotted lines. The invention provides for AVOIDING the linear profile  6  and instead constructing concave surfaces  16  ( FIG. 6A ). By forming concave surfaces  16 , the cross-sectional profile in the invention approximates an hourglass shape. Concave surfaces  16  run axially along exterior of blade case  32 . A concavity is defined by a concave surface  16  between non-concave surface sections  17 ,  18 . The concavities create pockets for soft tissue to rest and hurdles for the same tissue to overcome to slide over the top  19  of blade case  32 . 
     In  FIGS. 6-6B , construction of a concavity into both side surfaces of a blade case is illustrative; in other embodiments, a concavity is constructed into only one side surface of a blade case. 
     Concavity depth  16 D ( FIG. 6B ) is the distance between, on the one hand, a line  17 ′ fl defined by the non-concave section  17 , and, on the other hand, a line  20 ′ including the most concave point  20  of the concave surface  16  and drawn parallel to line  17 ′. For a blade case having length  32 L of about 3.75-3.8 inches, a preferred range for concavity depth  16 D is about 0.025-0.050 inches. 
     Examples of a length of a concavity are, e.g., a length equal to a full length of a blade case; a length less than a full length of a blade case. When the concavity extends less than a full length of the blade case, for the concavity length to begin at tip  33  ( FIG. 6 ) of blade case  32  and extend backwards from the tip  33  at least about a length equal to half the blade case  32 &#39;s length is preferred. 
     In  FIGS. 6-6B , construction of a concavity into a side surface of a blade case is illustrative; in other embodiments, a concavity is constructed into a bottom surface of a blade case. For example, a concave bottom surface of a blade case is considered useful particularly for working with the ulnar nerve in cubital tunnel release surgeries. 
     In  FIG. 6A , the concave surface  16  is illustrated as smooth but it will be appreciated that the concave surface is not required to be smooth in all embodiments. For example, in some embodiments ridges  21  ( FIG. 7 ) are formed as part of concave surface  16 ′. As another example, in other embodiments, surface  16 ″ is generally-concave without being fully symmetrical, such as a concavity defined by a hooked edge  24  ( FIG. 8 ). 
     As a consequence of the concave surfaces  16 , flanges  25  ( FIG. 6A ) are formed. 
     An example of a shape of a tip of the blade case is a rounded edged tip, such as, e.g., a filleted, rounded-edge shape that forms a 90-180° total arc around the distal tip of the cannula, with a fillet radius of 0.001-0.010 inch. 
     Preferably a scraper tip such as scraper tip  40  ( FIGS. 10-10A ) is included in the blade case. Preferably scraper tip  40  is distally-flared with a sharpened edge for scraping synovium and other tissue present along the top plane of the blade case  42  during carpal tunnel surgery. As to degree of sharpness of scraper tip  40 , preferably scraper tip  40  is not sharp enough to cut synovium and other biological tissue, but is sharp enough to scrape biological tissue away form the transverse ligament. 
     Advantageously a flared scraper tip such as scraper tip  40  also can be used to split muscle without cutting, during cubital tunnel surgery. 
     An endoscopic surgical instrument comprising a distally-flared scraper tip such as scraper tip  40  advantageously can remain in place within a patient when certain scraping is needed, without needing to be retracted to make room for a separate scraper to be used. 
     The invention may be further appreciated with reference to the following examples, without the invention being limited thereto. 
     Example 1 
     In this example, an inventive endoscopic surgical device according to the figures herein comprises a blade case that occupies a maximum external volume per unit length (V/L) less than 0.055 in 2 , with a height to width (FI/W) ratio less than 80%. V/L will be appreciated to essentially reflect cross-sectional area. We refer herein to “maximum” because, for injection molded plastic parts, some amount of draft is always to be expected along the sidewalls, corresponding to reduced part size moving from the hub to the tip. 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                   
                 COMPARISON  
                 INVENTIVE  
               
               
                   
                   
                 EX.* 
                 EX. 
               
               
                   
                   
               
             
            
               
                   
                 W 
                 0.25 in 
                 0.26 in 
               
               
                   
                 H 
                 0.29 in 
                 0.21 in 
               
               
                   
                 L 
                 2.75 in 
                 at least 3.75 in 
               
               
                   
                 H/W 
                 112% 
                 less than 80% 
               
               
                   
                 Max. V/L 
                 0.075 in 2   
                 0.055 in 2   
               
               
                   
                   
               
               
                   
                 *Commercially sold endoscopic surgical device 
               
            
           
         
       
     
     By contrast to the inventive example with H/W 80% or less (i.e., wider than tall), blade cases of endoscopic surgical devices currently sold have H/W 112% (i.e., taller than wide). Because this inventive example has H/W below 100%, the stiffness and strength of the blade case is reduced compared to the case with H/W 112%, To bring the stiffness and strength of the blade case to the requisite level, use of the further features of the figures herein is strongly preferred. 
     A reduction of 10% of the maximum V/L of commercially available endoscopic surgical devices would be considered a significant improvement by those in the industry. The context in which V/L is contemplated by those in the industry is as follows. The reason that patients undergo carpal and cubital tunnel releases is because the tissue in these regions is compressing the median and ulnar nerves, causing pain and numbness and loss of function. An endoscopic surgical device is used to cut ligaments and tissues to relieve that pressure. But, by inserting the device to perform the surgery, the device increases the pressure on the nerve, even for just the 5 minutes needed to perform the procedure, which can bring about potential additional pain and other temporary complications. The present invention&#39;s reduction of the device&#39;s V/L is highly advantageous, in that reduced V/L has an immediate and direct reduction in the pressure exerted by the device on the nerve during surgery. 
     Example 2 
     In this example is used a main blade case body  50  having integrally formed therein scraper tip  40  and comprising windows  7 ,  9  and concave walls  16 . The main case body  50  in this example is opaque black, formed from a relatively-stronger material than used for clear sections  4 ,  4 A. 
     The main case body  50 , clear top section  4 , clear bottom section  4 A (comprising window  11 ) are assembled into the surgical device of  FIG. 11A . 
     While the invention has been described in terms of its preferred embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims.