Patent Publication Number: US-2011054546-A1

Title: Polyaxial Pedicle Screw Assembly

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. Utility patent application Ser. No. 11/045,908 filed Jan. 28, 2005, which claims the benefit of U.S. Provisional Patent Application No. 60/548,543 filed on Feb. 27, 2004 and U.S. Provisional Patent Application No. 60/565,658 filed on Apr. 27, 2004, whereby the contents of all three applications, in their entireties, are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The embodiments of the invention generally relate to medical devices and assemblies, and more particularly to an orthopedic surgical implant assembly used in the field of surgical lumbar, thoracic and cervical spine treatment. 
     2. Description of the Related Art 
     Surgical procedures treating spinal injuries are one of the most complex and challenging surgeries for both the patient and the surgeon. When there are various deformities, trauma, or fractures of the vertebra, surgeons may attempt to “fuse” them together by attaching screw-like devices into the pedicles of the spine and thereby connecting several vertebrae (typically two or more) using a semi-rigid rod. However, due to the complexity of the human anatomy, most surgeons must bend the rod (causing notches thereby reducing fatigue resistance) before placing them into two or more non-aligned pedicle screws in order to properly stabilize the pedicle screw assembly within the patient&#39;s body. 
     Depending on the purpose of the spine surgery, indications, and patient size, surgeons must pre-operatively choose between different spinal systems with differing rod sizes pre-operatively sometimes causing delays in surgery while waiting for more adequate systems to be sterilized. Some surgeons prefer monoaxial screws for rigidity, while some sacrifice rigidity for surgical flexibility in screw placement. Therefore, a system is needed to accommodate both theories. For example, during scoliosis surgery conventional polyaxial systems typically cannot lock into a desired position to persuade the spinal column into desired correction before final construct assembly. 
     Most conventional top loading polyaxial spine screws do not do enough to address cantilever failure of the assembly components. Additionally, most polyaxial screws generally do not offer enough flexibility because the rod sits too closely on top of the center of rotation. Furthermore, most top loading screw systems generally do not accommodate different rod sizes. Thus, there remains a need for a new and improved pedicle screw assembly capable of overcoming the limitations of the conventional designs thereby providing the surgeon with improved intra-operative flexibility and the patient with an improved prognosis for better and complete rehabilitation. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, an embodiment of the invention provides an assembly comprising a screw head comprising a bulbous end; a fixator component configured for receiving the bulbous end of the screw head; a pin mounted in the screw head; and a blocker adapted to engage the screw head. The screw head comprises a slot configured for receiving a longitudinal member. The fixator component comprises a concave socket configured for receiving the bulbous end of the screw head. In one embodiment, the fixator component comprises a threaded end opposite the concave socket and configured for attaching to a bone. Preferably, the pin engages the fixator component and a bottom portion of the longitudinal member. Preferably, the blocker secures a top portion of the longitudinal member. 
     Preferably, the pin comprises an upper saddle portion and a lower tip portion. Additionally, according to one embodiment, the pin comprises a multi-part assembly. The pin may be made of one part that may be coated or it can be made of two parts (an upper and lower portion) comprising different materials, with the lower portion comprising a mechanically harder material than the upper portion. The screw head and the fixator component comprise a first material, and the lower tip portion of the pin comprises a material having a higher material hardness and compressive yield strength than the first material. The assembly may further comprise a wear resistant ceramic coating over the screw head and the fixator component. 
     Preferably, the screw head further comprises two opposed upright ends separated by the slot, wherein each of the opposed upright ends comprise an inner wall and an outer wall, wherein the inner wall comprises wall threads, and wherein the outer wall comprises grooves. Preferably, the blocker comprises blocker threads configured around an outer perimeter of the blocker, the blocker threads being dimensioned and configured to mate with the wall threads. The upper saddle portion of the pin may comprise a slot or slots. The bulbous end of the screw head may comprise a plurality of slots terminating at an opening at a tip of the bulbous end. Moreover, the bulbous end of the screw head preferably comprises a gap configured to receive the pin. The concave socket of the fixator component comprises an inner portion adapted to receive the bulbous end of the screw head; and preferably a dimpled outer portion or other geometries. Preferably, the fixator component comprises any of a bone screw and a hook. 
     Another aspect of the invention provides a pedicle fixation assembly comprising a screw head comprising a male bulbous end; a bone fixator component comprising a female concave semi-spherical socket for receiving the screw head; a locking saddle pin for engaging the screw head and the bone fixator component; and a blocker for engaging the screw head and for securing the longitudinal member. 
     Still another aspect of the invention provides a method of assembling a pedicle fixation assembly, wherein the method comprises attaching a screw head to a bone fixator component; securing the bone fixator component in a bone; securing a locking pin in the screw head; engaging the locking pin with the bone fixator component; inserting a longitudinal member in the screw head; and inserting a blocker in the screw head, wherein the screw head comprises a male bulbous end and the bone fixator component comprises a female concave semi-spherical socket for receiving the screw head. Preferably, the method further comprises coating the screw head and the bone fixator component with a wear resistant ceramic coating. The bone fixator component may be configured as any of a bone screw and a hook. 
     The embodiments of the invention provide a pedicle screw assembly implant device, which may be used anteriorly or posteriorly, and which is capable of being utilized in surgeries to achieve anterior lumbar interbody fusion, posterior lumbar interbody fusion, transverse lumbar interbody fusion, correct degenerative disc disease, adult and pediatric scoliosis as a fixation device, and posterior cervical fusion. 
     The embodiments of the invention provide a polyaxial spinal screw that can become rigid similar to a monoaxial screw inter-operatively on demand. The embodiments of the invention also offer the surgeon more lateral range of motion than conventional products by utilizing the space under the screw head to provide a bigger arc of rotation. Moreover, the saddle pin component offers the flexibility to use a diametrical range of spinal rods instead of a fixed size rod. 
     These and other aspects of the embodiments of the invention will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating preferred embodiments of the invention and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments of the invention without departing from the spirit thereof, and the embodiments of the invention include all such modifications. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the invention will be better understood from the following detailed description with reference to the drawings, in which: 
         FIG. 1  illustrates an exploded view of the screw assembly according to an embodiment of the invention; 
         FIG. 2  illustrates an exploded view of the screw assembly during a step in the manufacturing according to an embodiment of the invention; 
         FIG. 3  illustrates an exploded view of the screw assembly during a step in the manufacturing according to an embodiment of the invention; 
         FIG. 4  illustrates an exploded view of the screw assembly during a step in the manufacturing according to an embodiment of the invention; 
         FIG. 5  illustrates a perspective view of the fully assembled screw assembly in a monoaxial position according to an embodiment of the invention; 
         FIG. 6  illustrates a perspective view of the fully assembled screw assembly in a polyaxial position according to an embodiment of the invention; 
         FIG. 7  is a partial internal view of the screw assembly in a monoaxial position according to an embodiment of the invention; 
         FIG. 8  is a partial internal view of the screw assembly in a polyaxial position according to an embodiment of the invention; 
         FIGS. 9A through 9H  are isolated views of the screw head according to an embodiment of the invention; 
         FIG. 10A  is a perspective view of a bone fixator assembly according to a second embodiment of the invention; 
         FIG. 10B  is a detailed view of the hook of the bone fixator assembly of  FIG. 10A  according to the second embodiment of the invention; 
         FIGS. 11A through 11B  are detailed views of the saddle pin according to a first embodiment of the invention; 
         FIGS. 12A through 12B  are detailed views of the saddle pin according to a second embodiment of the invention; 
         FIGS. 13 through 14   a  are detailed views of the saddle pin according to a third embodiment of the invention; 
         FIGS. 15A through 15C  are detailed views of the blocker according to an embodiment of the invention; and 
         FIG. 16  is a flow diagram illustrating a preferred method according to an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION 
     The embodiments of the invention and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments of the invention. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments of the invention may be practiced and to further enable those of skill in the art to practice the embodiments of the invention. Accordingly, the examples should not be construed as limiting the scope of the embodiments of the invention. 
     As mentioned, there remains a need for a new and improved pedicle screw assembly capable of overcoming the limitations of the conventional designs thereby providing the surgeon with improved intra-operative flexibility and the patient with an improved prognosis for better and complete rehabilitation. The embodiments of the invention address this need by providing an improved polyaxial pedicle screw device and method of assembly capable of accommodating multiple rod diameters and withstanding higher failure strengths. Referring now to the drawings and more particularly to  FIGS. 1 through 16  where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred embodiments of the invention. 
       FIGS. 1 through 6  provide an exploded view of the pedicle screw assembly  1  according to a first embodiment of the invention. The screw assembly  1  comprises a bone screw (fixator component)  10  having a threaded end  11  for engaging a bone (not shown) and a concave female socket end  12  for engaging and receiving the screw head  20 . 
     As implemented, the screw head  20  is first snapped into place in the bone screw  10  as shown in  FIG. 2 . Then, as shown in  FIGS. 3 and 9B , the saddle pin  30  snaps into place in the lower base portion  25  of the screw head  20 , which includes a groove  26  (best seen in  FIG. 7 ) for receiving the saddle pin  30 . In the manufacturing process, once the saddle pin  30  snaps into place, the screw assembly  1  is prepared for ultra sonic cleaning to remove any impurities and subsequently may be shipped in this manufactured format (with the saddle pin  30  connected to the screw head  20 , which is connected to the bone screw  10 ). 
       FIG. 7  shows that the female spherical socket  12  of the bone screw  10  has an undercut  7  to allow the screw head  20  to pivot freely but not to disassemble once the saddle pin  30  is inserted. The thread  11  of the bone screw  10  may be a multiple lead thread to allow faster insertion into a bone. This thread  11  may be tapered on the minor diameter while cylindrical on the major diameter to allow a new “bite” with every turn and to accommodate more thread depth towards the bottom of the bone screw  10  for the cancellous bone. 
     Once the bone screw  10  is inserted into the bone, a longitudinal member  50 , which may be embodied as a rod, bar, etc. and blocker  40  are inserted into the screw assembly  1 , as illustrated in  FIG. 4 . The screw head  20  can accommodate 5.5 mm as well as 6.0 mm rods, which is advantageous over conventional screw assemblies that are limited to accepting only rods of a uniform dimension.  FIG. 5  illustrates the assembled view of the screw assembly  1  in the straight monoaxial direction. The threads  11  of the bone screw  10  are double lead, which provides greater surface contact with the bone, but drives at 4 mm/revolution.  FIG. 6  illustrates the screw assembly  1  in a rotationally articulated position. The maximum angulation is 25 degrees/side, but the medial correction/travel of the longitudinal member  50  is 3.8 mm/side, which is nearly twice of what most conventional screws offer. 
     In  FIG. 7 , the locking mechanism of the screw assembly  1  is illustrated. Here, a two step locking process is shown. The first position expands the screw head  20  into the bone screw  10 , and the second position permanently turns the polyaxial screw assembly  1  into a monoaxial screw assembly  1  by using the saddle pin  30  to lock the assembly  1 . As  FIG. 8  demonstrates, the screw assembly  1  can be permanently locked in any desired position (within the 25 degree guideline) simply by sending the longitudinal member  50  “home” or by using a tool (not shown) to lock the assembly  1  at the desired angle. 
       FIG. 9A  illustrates the overall configuration of the screw head  20 .  FIG. 9B  illustrates a front view of the screw head  20 .  FIG. 9C  is a cross-sectional view from cut-line “CC” of  FIG. 9D .  FIG. 9E  is a cross-sectional view from cut-line “BB” of  FIG. 9F  and FIG.  9 G is a cross-sectional view from cut-line “AA” of  FIG. 9F . Additionally,  FIG. 9H  is an enlarged detailed view of the encircled area “A” of  FIG. 9G  illustrating the threaded inner portion  23  in more detail. As shown in  FIGS. 9A through 9H , the screw head  20  includes a bulbous (spherical) male end  21  for engaging the concave female socket  12  of the bone screw  10 . The screw head  20  also includes a pair of upright ends  22  opposite the bulbous male end  21 , wherein the upright ends  22  comprise a threaded inner portion  23  for engaging the blocker  40 . Furthermore, the screw head  20  includes a generally open U-shaped inner portion  24  for receiving the saddle pin  30  and the longitudinal member  50 . The male end  21  of the screw head  20  includes a plurality (for example, four or more) slots  6  that allow the male end  21  to expand into the female spherical socket  12  of the bone screw  10  at any allowable angle once the saddle pin  30  is forced through. 
     Since the screw head  20  is pivoting inside the female socket end  12  of the bone screw  10 , the assembly  1  is allowed to be inserted deeper into the bone without having the bone or anatomy prematurely limit the range of angulations of the screw head  20 . The screw head  20  further includes external features or cuts  29  that assist in accommodating surgical instrumentation during manipulation and assembly during the surgical procedure. These cuts  29  allow various instruments (not shown) to firmly and positively hold and manipulate the screw head  20  on one side or both sides of screw head  20 . 
       FIG. 10A  is a perspective view of a bone fixator assembly according to a second embodiment of the invention, wherein the bone fixator component is configured as a hook  60 . The hook  60  is further illustrated in  FIG. 10B . The hook  60  includes a concave socket  12  having an inner portion  9  adapted to receive the bulbous end  21  of the screw head  20 ; and a dimpled outer portion  8 . The hook  60  further includes a pair of arms  61 ,  62  connected by a connection arm  64 . A space  63  separates the arms  61 ,  62  from one another. The arms  61 ,  62  are configured to receive an additional member (not shown) for subsequent attachment to the bone. 
     The several embodiments of the saddle pin  30  are shown in  FIGS. 11A through 14 . The saddle pin  30  provides a proper seat for the longitudinal member  50  and avoids notching a typical titanium longitudinal member  50  (titanium is very notch sensitive). Furthermore, the saddle pin  30  allows one to accommodate multiple sizes of longitudinal members  50  in the same screw assembly system  1  which is a first for a titanium system because of the above-mentioned notching factors. The saddle pin  30  is configured with a slot  32  through the center to allow expansion of the upper portion (head)  131  of the saddle pin  30 . The bottom  35  of the saddle pin head  131  is angled to allow the saddle pin  30  to accept a larger-sized longitudinal member  50 . The saddle pin  30  initially expands the male sphere  21  of the screw head  20  into the female spherical socket  12  in the bone screw  10  causing the screw assembly system  1  to lock or start locking (i.e., causing the male sphere  21  of the screw head  20  to lock in the female spherical socket  12  of the bone screw  10 ). The saddle pin  30  then “digs” into the female spherical socket  12  of the bone screw  10  to provide a secondary locking force to avoid bending failure of the assembly  1 . 
       FIGS. 11A through 11B  illustrate a first embodiment of the saddle pin  30 . The saddle pin  30  generally includes an upper portion  131  and a lower portion  132 . The upper portion includes a slot  32 , which is configured from the lowest area  33  of the upper portion  131  into the upper area  34  of the lower portion  132  of the saddle pin  30 . A secondary locking mechanism  36  may be configured on the lower portion  132  of the saddle pin to further achieve locking of the saddle pin  30  once it is inserted in the screw head  20 . The lower portion  132  of the saddle pin  30  terminates with a pointed end  37  to allow for digging into the female socket  12  of the bone screw  10 .  FIGS. 12A through 12B  illustrate a second embodiment of the saddle pin  30 . The difference between the first and second embodiments of the saddle pin  30  is that the upper portion of the saddle pin  131  in the second embodiment includes two generally flat upper opposed ends  38  to more matingly configure with the geometry of the screw head  20  and the longitudinal member  50 . 
       FIGS. 13 through 14  illustrate a third embodiment of the saddle pin  30 . In particular, in the third embodiment, the saddle pin  30  comprises two parts: an upper portion  131  preferably comprising titanium and a lower portion  132  which is preferably ceramic. According to the third embodiment, the material of the lower portion  132  of the saddle pin  30  is preferably ceramic and has a higher hardness and compressive yield strength than the comparative hardness and compressive yield strength of Ti 6 Al 4 V, which is the material which may be used in constructing the screw head  20  and bone screw  10 . 
     As shown in  FIG. 13 , the upper portion  131  of the saddle pin  30  includes a slot  32  in the seat portion  133  and tapered angled ends  134 . Preferably, the saddle pin  30 ; i.e., the upper portion  131  and the ceramic tip  132  are assembled last in the overall process. Specifically, the screw head  20  snaps into the bone screw  10 . Then, the ceramic tip  132  slides into the screw head  20 , and finally the titanium saddle (upper portion)  131  is press fitted into the screw head  20  keeping everything in place and oriented in a relaxed state. 
     As best seen in  FIG. 14 , the lower portion  132  of the saddle pin terminates with a series of cascading walls  137 ,  138  having sloped angles, terminating with the pointed end  37  for attachment into the screw head  20 /bone screw  10  assembly. The material properties of the saddle pin tip  132  are such that it prevents the deformation on the saddle pin  30  before the saddle pin  30  gives the proper bending and penetrating effects onto the screw head  20 /bone screw  10  assembly. Examples of the types of materials used for the saddle pin pointed end  37  include Zyranox™ and HIP Vitox™, both of which are available from Morgan Advanced Ceramics, United Kingdom. 
     The blocker  40 , which is further illustrated in  FIGS. 15A through 15C , includes a standard buttress thread  41  configured along an outer perimeter of the blocker  40 . The blocker  40  helps to secure the longitudinal member  50  inside the screw head  40 . The threads  41  of the blocker  40  are configured to engage the threads  23  of the screw head  20 . Additionally, the blocker  40  aids in preventing the expansion of the screw head  20  when torqued on the longitudinal member  50 , directing the counterforce more vertically than horizontally. The top  42  of the blocker  40  has a fastening feature  43  such as a hex or square lock feature to allow high torque to be applied in locking the assembly  1 . Furthermore, the blocker  40  may be configured with a free rotating saddle (not shown) to accommodate, via tangential contact, the longitudinal member  50  and help to further prevent notching of the titanium alloy used to construct the longitudinal member  50 . Moreover, the blocker  40  may have a “timed” thread  41  that is consistently and precisely related to the blocker driving tool (not shown) to help calculate the torsional and vertical position of the blocker  40  thereby assisting the torque measurement applied to the blocker  40 . 
     Another aspect of the invention is illustrated in the flowchart of  FIG. 16 , which includes descriptions which refer to components provided in  FIGS. 1 through 15C .  FIG. 16  illustrates a method of assembling a pedicle screw assembly  1 , wherein the method comprises attaching ( 200 ) a screw head  20  to a bone fixator component  10 ; securing ( 210 ) the bone fixator component  10  in the bone (not shown); securing ( 220 ) a saddle pin  30  in the screw head  20 ; engaging ( 230 ) the saddle pin  30  with the bone fixator component  10 ; inserting ( 240 ) a longitudinal member  50  in the screw head  20 ; and inserting ( 250 ) a blocker  40  in the screw head  20 . As mentioned, the embodiments of the invention provide an axial movement of the screw head up to 25 degrees in any plane. Moreover, the embodiments of the invention allow for greater medial translation of the longitudinal member  50  (nearly 4 mm compared to the conventional devices which are generally limited to 2 mm). 
     Moreover, according to an aspect of the invention, the inventive assembly  1  can be used as a dynamic rod system to complement artificial discs. According to this embodiment, the outside of the spherical joint part  21  of the screw head  20  and the inner spherical surface  9  of the bone screw cup  12  are coated with a wear resistant ceramic coating. In this scenario, the saddle pin  30  is not digging into the bone screw  10  and in fact is configured at a shorter length than some of the other embodiments. This system allows some motion instead of rigid fixation and shares the load with the artificial disc disallowing excessive forces being applied to the artificial disc and increasing its functional life. For example, this occurs as a result of the ceramic coating, which may be used in the embodiments of the invention. As such, the spherical joint  21  of the screw head  20  and the inner spherical surface  12  of the bone screw  10  have lower friction and higher wear resistance characteristics, thus improving the overall characteristics of the screw assembly  1 . 
     Generally, as shown in  FIG. 1 through 15C , the embodiments of the invention provide an assembly  1  comprising a screw head  20  comprising a bulbous end  21 ; a fixator component  10  configured for receiving the bulbous end  21  of the screw head  20 ; a pin  30  mounted in the screw head  20 ; and a blocker  40  adapted to engage the screw head  20 . The screw head  20  comprises a slot  24  configured for receiving a longitudinal member  50 . The fixator component  10  comprises a concave socket  12  configured for receiving the bulbous end  21  of the screw head  20 . In a first embodiment, the fixator component  10  also comprises a threaded end  11  opposite the concave socket  12  and configured for attaching to a bone. The pin  30  engages the fixator component  10  and a bottom portion  51  of the longitudinal member  50 . The blocker  40  secures a top portion  52  of the longitudinal member  50 . The pin  30  comprises an upper saddle portion  131  and a lower tip portion  132 . 
     Additionally, the pin  30  may comprise a multi-part assembly. The upper saddle portion  131  of the pin  30  comprises titanium and the lower tip portion  132  of the pin  30  comprises a ceramic material. Moreover, the lower tip portion  132  comprises a mechanically harder material than the upper saddle portion  131 . The screw head  20  and the fixator component  10  comprise a first material, and the lower tip portion  132  of the pin  30  comprises a material having a higher material hardness and compressive yield strength than the first material. The assembly  1  further comprises a wear resistant ceramic coating (not shown) over the screw head  20  and the fixator component  10 . 
     The screw head  20  further comprises two opposed upright ends  22  separated by the slot  24 , wherein each of the opposed upright ends  22  comprise an inner wall  27  and an outer wall  28 , wherein the inner wall  27  comprises wall threads  23 , and wherein the outer wall  28  comprises grooves (cuts)  29 . The blocker  40  comprises blocker threads  41  configured around an outer perimeter  42  of the blocker  40 , the blocker threads  41  being dimensioned and configured to mate with the wall threads  23 . The upper saddle portion  131  of the pin  30  comprises a slot  32 . The bulbous end  21  of the screw head  20  comprises a plurality of slots  6  terminating at an opening  4  at a tip  3  of the bulbous end  21 . Moreover, the bulbous end  21  of the screw head  20  comprises a gap  19  configured to receive the pin  30 . The concave socket  12  of the fixator component  10  comprises an inner portion  9  adapted to receive the bulbous end  21  of the screw head  20 ; and a dimpled outer portion  8 . The fixator component  10  is configured as any of a threaded bone screw  10  (as shown in  FIGS. 1 through 8 ) and a hook  60  (as shown in  FIGS. 10A and 10B ) according to the several embodiments of the invention. 
     The embodiments of the invention provide a pedicle screw assembly implant device  1 , which may be used anteriorly or posteriorly, and which is capable of being utilized in surgeries to achieve anterior lumbar interbody fusion, posterior lumbar interbody fusion, transverse lumbar interbody fusion, correct degenerative disc disease, adult and pediatric scoliosis as a fixation device, and posterior cervical fusion. 
     Moreover, the embodiments of the invention provide a polyaxial spinal screw assembly  1  that can become rigid similar to a monoaxial screw inter-operatively on demand. The embodiments of the invention also offer the surgeon more lateral range of motion than conventional products by utilizing the space under the screw head  20  to provide a bigger arc of rotation. Moreover, the saddle pin  30  component offers the flexibility to use a diametrical range of spinal longitudinal members  50  instead of a fixed size longitudinal member. 
     The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments of the invention have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments of the invention can be practiced with modification within the spirit and scope of the appended claims.