Abstract:
Spinal rod reduction apparatuses, systems, and methods are provided. In various examples, a rod reduction apparatus includes a first threaded member including an engagement feature configured to selectively anchor the first threaded member to the implantable screw assembly. A second threaded member is configured to threadably engage with the first threaded member. The second threaded member is axially movable with respect to the first threaded member with rotation of the second threaded member. A spinal rod urging member is axially movable with the second threaded member. The urging member includes a bearing surface that is configured to selectively abut the spinal rod and selectively urge the spinal rod toward the implantable screw assembly with rotation of the second threaded member in a first rotational direction.

Description:
CLAIM OF PRIORITY 
     This Application is a divisional of U.S. patent application Ser. No. 13/139,373, filed Feb. 9, 2012, which is a National Stage of International Application No. PCT/US2009/006433, filed Dec. 8, 2009, which claims the benefit of U.S. Provisional Application No. 61/138,392, filed Dec. 17, 2008, the disclosures of all of which are incorporated herein by reference in their entireties for all purposes. 
    
    
     TECHNICAL FIELD 
     This patent document pertains generally to orthopedics. More particularly, but not by way of limitation, this patent document pertains to an apparatus and method for spinal deformity correction. 
     BACKGROUND 
     Several techniques exist in the field of spinal surgery for reducing a spinal rod into a posterior pedicle screw. The primary technique utilizes a separate rod reduction instrument that couples to the head of the screw after the screw is inserted and the rod is placed, such as rocker forks or ratchet style instruments, which are designed to reduce the rod one level at a time, i.e., to each pedicle screw separately. Such segmental reduction techniques may produce large axial loads on the pedicle screws. 
     Alternatively, a rod can be conformed to a specific deformity and then seated within an implanted pedicle screw. Once seated, the deformity can be corrected by bending the rod in situ. This technique may be time-consuming and places stresses and strains on the rod prior to implantation. 
     Certain rod reduction techniques utilize specialty reduction pedicle screws that include integrated upwardly extending tabs that can be used to reduce the rod gradually over the entire length of a deformity. Once the rod reduction is completed, the extended tabs are broken off. This technique, however, is typically limited to the reduction screw only and can cause the implant to be expensive. 
     Overview 
     The present inventors have recognized, among other things, that stresses and strains to pedicle screws and/or spinal rods present problems during spinal rod reduction procedures. The present inventors have further recognized that there exists an unmet need for a streamlined, externally mounted mini-reduction instrument that can be used on any hook or screw type, including monoaxial, polyaxial, and sagittal screws, and can be reused, modified, or removed as necessary at any time during the entire course of the spinal corrective procedure. 
     This patent document describes, among other things, apparatuses, systems, and methods for spinal rod reduction. In various examples, a rod reduction apparatus includes a first threaded member including an engagement feature configured to selectively anchor the first threaded member to the implantable screw assembly. A second threaded member is configured to threadably engage with the first threaded member. The second threaded member is axially movable with respect to the first threaded member with rotation of the second threaded member. A spinal rod urging member is axially movable with the second threaded member. The urging member includes a bearing surface that is configured to selectively abut the spinal rod and selectively urge the spinal rod toward the implantable screw assembly with rotation of the second threaded member in a first rotational direction. 
     In Example 1, an apparatus is configured to selectively engage with a spinal rod and an implantable screw assembly. The apparatus comprises a first threaded member including first threads around at least a portion of an outer surface of the first threaded member. The first threaded member includes an engagement feature configured to selectively anchor the first threaded member to the implantable screw assembly. A second threaded member includes second threads around at least a portion of an inner surface of the second threaded member. The second threaded member is configured to threadably engage with the first threaded member. The second threaded member is axially movable with respect to the first threaded member with rotation of the second threaded member. A spinal rod urging member is axially movable with the second threaded member. The urging member includes a bearing surface that is configured to selectively abut the spinal rod and selectively urge the spinal rod toward the implantable screw assembly with rotation of the second threaded member in a first rotational direction. 
     In Example 2, the apparatus of Example 1 optionally is configured such that the engagement feature includes at least one protrusion configured to mate with a corresponding number of receptacles of the implantable screw assembly. 
     In Example 3, the apparatus of one or more of Examples 1-2 optionally is configured such that the engagement feature includes a grasping element configured to selectively couple to a proximal end of the implantable screw assembly. 
     In Example 4, the apparatus of one or more of Examples 1-3 optionally is configured such that the engagement feature is disposed at a distal end of the first threaded member. 
     In Example 5, the apparatus of one or more of Examples 1-4 optionally is configured such that the urging member is coupled to the second threaded member. 
     In Example 6, the apparatus of one or more of Examples 1-5 optionally is configured such that the first threaded member is substantially tubular and includes a first leg and a second leg, the first and second legs extending substantially axially, wherein distal ends of the first and second legs are configured to be selectively radially separable. 
     In Example 7, the apparatus of Example 6 optionally is configured such that the first and second legs are substantially semi-circular in cross section. 
     In Example 8, the apparatus of Example 7 optionally is configured such that the first and second legs of the first threaded member are held together by the second threaded member threadably engaged around the outer surface of the first threaded member. 
     In Example 9, the apparatus of Example 8 optionally is configured such that the outer surface of the first threaded member includes a portion of decreased diameter configured to allow the first and second legs to selectively radially separate with the first threaded member threadably engaged with the second threaded member. 
     In Example 10, the apparatus of one or more of Examples 6-9 optionally is configured such that the first threaded member includes a gap between the first leg and the second leg, the gap being configured to accommodate the spinal rod. 
     In Example 11, the apparatus of Example 10 optionally is configured such that the bearing surface of the urging member is disposed at least partially within the gap between the first leg and the second leg. 
     In Example 12, the apparatus of one or more of Examples 1-11 optionally is configured such that the second threaded member includes a tool engagement portion configured to engage with a tool configured to rotate the second threaded member with respect to the first thread member. 
     In Example 13, the apparatus of Example 12 optionally is configured such that the tool engagement portion includes a recess including a drive surface configured to mate with the tool. 
     In Example 14, the apparatus of one or more of Examples 12-13 optionally is configured such that the tool engagement portion includes a nut configured to mate with the tool. 
     In Example 15, the apparatus of Example 14 optionally is configured such that the nut includes a hex nut. 
     In Example 16, the apparatus of one or more of Examples 1-15 optionally is configured such that the spinal rod urging member includes a claw element including one or more arms, each arm including the bearing surface configured to selectively abut the spinal rod. 
     In Example 17, the apparatus of Example 16 optionally is configured such that the bearing surface of each arm is disposed at an end of the arm. 
     In Example 18, the apparatus of one or more of Examples 16-17 optionally is configured such that the bearing surface includes a rod recess. 
     In Example 19, the apparatus of one or more of Examples 1-18 optionally is configured such that the engagement feature of the first threaded member includes a grasping element configured to couple to an underside of a head of the implantable screw assembly. 
     In Example 20, the apparatus of one or more of Examples 1-19 optionally is configured such that the second threaded member includes a gripping surface configured to grip during manual rotation of the second threaded member with respect to the first threaded member. 
     In Example 21, an method comprises placing at least one rod reducer along a spinal rod and substantially in alignment with at least one pedicle screw. Placement of the rod reducer along the spinal rod includes substantially aligning a bearing surface of a spinal rod urging member of the rod reducer with the spinal rod. The rod reducer is engaged with the pedicle screw. The rod reducer is incrementally actuated to gradually reduce the spinal rod into engagement with the pedicle screw. Actuation of the rod reducer causes movement of the bearing surface toward the pedicle screw to urge the spinal rod toward the pedicle screw. The pedicle screw is engaged with the spinal rod. 
     In Example 22, the apparatus of Example 21 optionally is configured such that engaging the pedicle screw with the spinal rod includes attaching a locking cap to the pedicle screw to retain the spinal rod in engagement with the pedicle screw. 
     In Example 23, the apparatus of one or more of Examples 21-22 optionally comprises removing the rod reducer from the pedicle screw after engagement of the pedicle screw with the spinal rod. 
     In Example 24, the apparatus of Example 23 optionally comprises cleaning the rod reducer for reuse after removal of the rod reducer from the pedicle screw. 
     In Example 25, the apparatus of one or more of Examples 21-24 optionally is configured such that placing the at least one rod reducer along the spinal rod includes placing two or more rod reducers along the spinal rod and substantially in alignment with two or more pedicle screws. 
     In Example 26, the apparatus of one or more of Examples 21-25 optionally comprises placing the spinal rod along a plurality of pedicle screws. Without using a rod reducer, the spinal rod is engaged to one or more pedicle screws for which no spinal rod reduction is necessary. Using one or more rod reducers, the spinal rod is engaged to one or more pedicle screws for which spinal rod reduction is necessary. 
     In Example 27, the apparatus of one or more of Examples 21-26 optionally is configured such that engaging the rod reducer with the pedicle screw includes manually engaging the rod reducer with the pedicle screw. 
     In Example 28, the apparatus of one or more of Examples 21-27 optionally is configured such that engaging the rod reducer with the pedicle screw includes engaging the rod reducer with the pedicle screw using a tool configured to mate with a tool engagement portion of the rod reducer. 
     In Example 29, a spinal rod reduction system comprises a spinal rod. A plurality of pedicle screws is configured to engage with the spinal rod. A plurality of rod reducers each includes a first threaded member including first threads around at least a portion of an outer surface of the first threaded member. The first threaded member includes an engagement feature configured to selectively anchor the first threaded member to the pedicle screw. A second threaded member includes second threads around at least a portion of an inner surface of the second threaded member. The second threaded member is configured to threadably engage with the first threaded member. The second threaded member is axially movable with respect to the first threaded member with rotation of the second threaded member. A spinal rod urging member is axially movable with the second threaded member. The urging member includes a bearing surface that is configured to selectively abut the spinal rod and selectively urge the spinal rod toward the pedicle screw with rotation of the second threaded member in a first rotational direction. 
     In Example 30, the system of Example 29 optionally is configured such that the rod reducers are configured to engage with the pedicle screws and the spinal rod at locations where the spinal rod is spaced from the pedicle screws. 
     In Example 31, the system of one or more of Examples 29-30 optionally is configured such that the plurality of rod reducers are configured to incrementally urge the spinal rod toward the plurality of pedicle screws. 
     In Example 32, the system of one or more of Examples 29-31 optionally comprises a locking cap configured to engage with the pedicle screw and retain the spinal rod in engagement with the pedicle screw. 
     In Example 33, the system of one or more of Examples 29-32 optionally comprises a tool configured to mate with a tool engagement portion of each of the rod reducers, the tool being configured to rotate the second threaded member with respect to the first thread member. 
     In Example 34, the system of Example 33 optionally is configured such that the tool engagement portion includes a recess including a drive surface configured to mate with the tool. 
     In Example 35, the system of one or more of Examples 33-34 optionally is configured such that the tool engagement portion includes a nut configured to mate with the tool. 
     In Example 36, a spinal rod reduction assembly comprises one or more pedicle screws engaged with one or more vertebrae. A spinal rod is substantially aligned with the one or more pedicle screws. At least one rod reducer is removably engaged with at least one pedicle screw at a location where the spinal rod is spaced by a distance from the pedicle screw. The rod reducer includes a spinal rod urging member axially movable with respect to the rod reducer. The urging member includes a bearing surface that is configured to selectively abut the spinal rod and selectively urge, with actuation of the rod reducer, the spinal rod toward the pedicle screw to decrease the distance between the spinal rod and the pedicle screw. 
     These and other examples, advantages, and features of the present rod reduction apparatuses and methods will be set forth in part in the following Detailed Description. As such, this Overview is intended to provide an overview of subject matter of the present patent document. It is not intended to provide an exclusive or exhaustive explanation of the invention. The Detailed Description is included to provide further information about the present patent document. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, like numerals describe similar components throughout the several views. Like numerals having different letter suffixes represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
         FIGS. 1A and 1B  illustrate a front perspective view and a front elevational view, respectively, of a miniature rod reducer instrument in accordance with an embodiment of the present document; 
         FIGS. 2A, 2B, and 2C  illustrate a side elevational view, a cross-sectional view taken along line  2 B- 2 B of  FIG. 2A , and a top plan view, respectively, of an outer drive sleeve element of the miniature rod reducer instrument of  FIG. 1 ; 
         FIGS. 3A, 3B, and 3C  illustrate a front elevational view, a left side elevational view, and a top plan view, respectively, of a retaining guide ring element of the miniature rod reducer instrument of  FIG. 1 ; 
         FIGS. 4A, 4B, and 4C  illustrate a front elevational view, a cross-sectional view taken directly into the page of  FIG. 4A , and a cross-sectional view taken along line  4 C- 4 C of  FIG. 4A , respectively, of a threaded tube element of the miniature rod reducer instrument of  FIG. 1 ; 
         FIGS. 5A and 5B  illustrate front perspective views of the miniature rod reducer instrument of  FIG. 1  coupled to a spinal rod and a pedicle screw assembly in an unreduced and reduced rod configuration, respectively; 
         FIGS. 6A and 6B  illustrate perspective, cross-sectional views taken along lines  6 A- 6 A and  6 B- 6 B of  FIG. 5B  of the rod reducer instrument of  FIG. 1 ; 
         FIG. 7  illustrates a front perspective view of the rod reducer instrument of  FIG. 1  coupled to a locking cap ratcheting T-handle driver instrument with a hex drive coupler, a spinal rod, and a pedicle screw assembly; 
         FIGS. 8A-8D  illustrate various perspective views of a miniature rod reducer instrument in accordance with an embodiment of the present document; and 
         FIGS. 9A-9F  illustrate various perspective views of a miniature rod reducer instrument in accordance with an embodiment of the present document. 
     
    
    
     DETAILED DESCRIPTION 
     The present inventors have recognized, among other things, that it is desirable to construct a streamlined, externally mounted mini-reduction instrument that can be used on any hook or screw type, including monoaxial, polyaxial, and sagittal screws, and can be reused, modified, or removed as necessary at any time during the entire course of the spinal corrective procedure. 
     Certain terminology is used in the following description for convenience only and is not limiting. The words “right”, “left”, “lower” and “upper” designate directions in the drawings to which reference is made. The words “inwardly” or “distally” and “outwardly” or “proximally” refer to directions toward and away from, respectively, the geometric center or orientation of the instrument assembly and related parts thereof. The words, “anterior”, “posterior”, “superior,” “inferior”, “lateral” and related words and/or phrases designate preferred positions and orientations in the human body to which reference is made and are not meant to be limiting. The terminology includes the above-listed words, derivatives thereof and words of similar import. 
     In reference to  FIGS. 1-7 , a miniature rod reducer instrument  100  in accordance with an embodiment of the present invention includes an outer drive sleeve  110 , a retaining guide ring  120 , and a threaded tube  130 . The rod reducer  100  is selectively engageable with a spinal rod  140  and a pedicle screw assembly  150 , which can assume the form of a monoaxial pedicle screw, a sagittal screw, a polyaxial pedicle screw, a hook or nearly any type of screw that includes a head or anchor seat constructed to engage a distal end of the threaded tube  130 . The outer drive sleeve  110 , in an example, includes a proximal end, a distal end, a longitudinal axis between the proximal and distal ends, a cannulated interior, a gripping surface  112  disposed on a proximal exterior surface that may include a knurled or other traction grip surface, a visibility window  114  that enables viewing and weight reduction, a drive surface  116  such as a hex drive disposed interior to the proximal end and a series of interior threading  118  disposed on an interior surface at the distal end. The drive surface  116 , in an example, is engageable with a ratcheting T-handle driver instrument ( FIG. 7 ) with a hex drive coupler  160  to impart additional mechanical rotational force to the outer drive sleeve  110  to assist in rod reduction. 
     In an example, the threaded tube  130  includes a proximal end, a distal end, a longitudinal axis extending between the proximal and distal ends, a cannulated interior, a first leg  132  and a second leg  134 . The first and second legs  132 ,  134 , in an example, are held together by the interior confines of the outer drive sleeve  110  and the retaining guide ring  120 . In some examples, the first leg  132  includes an exterior threading  136 A and the second leg  134  includes an exterior threading  136 B. The exterior threading  136 A,  136 B can be a single or multi-lead thread to provide for faster reduction speed. In an example, the exterior threading  136 A,  136 B is a two start M18×1.5 with an effective pitch of 3 mm. In some examples, the first leg  132  includes an engagement feature  138 A interior to its distal end and the second leg  134  includes an engagement feature  138 B interior to its distal end. The engagement features  138 A,  138 B selectively engage and couple to the exterior surface of a pedicle screw assembly  150 . In an example, the engagement features  138 A,  138 B are comprised of male protrusions that mate with female receptacles inherent on the exterior surface of the pedicle screw assembly  150 . The engagement features  138 A,  138 B and their corresponding receptacles, in an example, provide stabilization in all three axes, as is best shown in  FIG. 6A . In an example, the first leg  132  includes an exteriorly disposed feature  139 A near the proximal end and the second leg  134  includes an exteriorly disposed feature  139 B near the proximal end. The exteriorly disposed features  139 A,  139 B, in an example, are comprised of regions in which the outer diameter of the threaded tube  130  and the pitch diameter of the exterior threading  136 A,  136 B decrease to allow the first and second arms  132 ,  134  to splay open slightly at the distal end to enable easy introduction of the rod reducer  100  over the pedicle screw assembly  150  and corresponding engagement of the engagement features  138 A,  138 B with the receptacles of the pedicle screw assembly  150 . The first and second arms  132 ,  134  are configured to splay open at the distal end approximately 2.5 degrees in an example. 
     In an example, the retaining guide ring  120  is disposed around the threaded tube  130  at the distal end of the outer drive sleeve  110  and includes first and second upwardly extending arms  122 A,  122 B, first and second outwardly extending tabs  124 A,  124 B disposed on ends of the upwardly extending arms  122 A,  122 B, respectively, and a rod recess  126  disposed at the distal end of the retaining guide ring  120  that selectively interfaces with the spinal rod  140 . 
     In an example, the outer drive sleeve  110  is constructed of stainless steel, titanium, or other biocompatible surgical grade metal, while the retaining guide ring  120  and threaded tube  130  are constructed of a biocompatible polymer material such as polyetheretherketone (PEEK). However, the drive sleeve  110  is not limited to metallic constructions and the retaining guide ring  120  and the threaded tube  130  are not limited to polymeric constructions and each may be constructed of any biocompatible material that is able to take on the general shape and withstand the normal operating conditions of the components. For example, the retaining guide ring  120  and threaded tube  130  may be constructed of titanium and the drive sleeve  110  may be constructed of PEEK. 
     In operation, and in continuing reference to  FIGS. 1-7 , a pedicle screw or several pedicle screw assemblies  150  are implanted into the vertebrae of a patient and the rod  140  may be pre-bent for potential deformity correction. The spinal rod  140  is loosely placed above the construct of pedicle screws  150  and attached to the pedicle screws  150  in which no reduction is necessary. The gripping surface  112  of the outer drive sleeve  110  is engaged and rotated with respect to the threaded tube  130  using manual rotation and/or the outer drive sleeve  110  may be rotated using the ratcheting T-handle driver instrument with a hex drive coupler  160  via the drive surface  116 . The retaining guide ring  120  surrounds the features  139 A,  139 B such that the distal ends of the first and second legs  132 ,  134  splay open. The distal end of the rod reducer  100  is placed over the spinal rod  140  and above a pedicle screw assembly  150  such that the first and second legs  132 ,  134  straddle the rod  140  and the engagement features  138 A,  138 B surround the corresponding receptacles on the pedicle screw assembly  150 . The outer drive sleeve  110  is then rotated manually with respect to the threaded tube  130  via the gripping surface  112  and/or rotating the ratcheting T-handle driver instrument with a hex drive coupler  160  with such that the retaining guide ring  120  and the outer drive sleeve  110  travel distally with respect to the threaded tube  130  via the engagement of the interior threading  118  and the first and second exterior threading  136 A,  136 B, thereby causing the unsplaying of the distal ends of the first and second arms  132 ,  134 , engagement of the first and second engagement features  138 A,  138 B with the receptacles on the pedicle screw  150 , engagement of the rod recess  126  to the spinal rod  140 , and downward translation of the spinal rod  140  with respect to the first and second legs  132 ,  134 . A plurality of rod reducer instruments  100  can be utilized in this manner to gradually reduce the spinal rod  140  into a plurality of pedicle screw assemblies  150  over a plurality of spinal levels. The rod reducers  100 , in an example, are slowly and systematically actuated to avoid overstressing the pedicle screw assemblies  150  and the interface with their corresponding vertebral bodies, which further allows for gradual stressing and stretching of soft tissue of the patient&#39;s spine while potentially correcting a deformity. The ratcheting T-handle driver instrument with a hex drive coupler  160  is then uncoupled from the outer drive sleeve  110  and locking caps, elements which serve to finally secure the spinal rod  140  with respect to the pedicle screw assemblies  150 , are introduced through the rod reducers  100  via a locking cap channel provided by the interior geometry of the threaded tube  130 . The locking caps can be coupled to the pedicle screw assemblies  150  using a cap driver instrument (not shown), which can be inserted through the rod reducer  100 . The locking cap driver  160  has an engagement feature for coupling to the locking caps and actuating their coupling to the pedicle screw assemblies  150 , such as a threaded, star drive, or hex drive engagement feature. The locking cap driver  160  may be a ratcheting driver, but is not so limited. In an example, the locking caps are coupled to the pedicle screw assemblies  150  and the locking cap driver  160  is uncoupled from the rod reducers  100 . The rod reducer(s)  100  are uncoupled from the pedicle screw assemblies  150  by disposing the retaining guide ring  120  over the features  139 A,  139 B such that the distal ends of the arms  132 ,  134  are splayed open and the engagement features  138 A,  138 B are disengaged from their corresponding receptacles on the pedicle screw assembly(s)  150 . The rod reducer  100  can be cleaned and sterilized for reuse. 
     In some examples, the rod reducer  100  does not introduce notches or mar the exterior of the spinal rod  140  during its reduction. In addition, the rod reducer  100  of some examples prevents splaying of the upwardly extending arms that form the rod-receiving channel of the pedicle screw assembly  150 . The rod reducer  100  can be coupled to a pedicle screw assembly  150  prior to or subsequent to the implantation of the pedicle screw  150 , according to surgeon preference. The rod reducer  100  can further be utilized to aid in de-rotation maneuvers of the spine during surgery. 
     In an example, and in reference to  FIGS. 8A-8D , a rod reducer  200  is provided that is configured especially for coupling to a monoaxial pedicle screw  250  and reducing a spinal rod  140  thereto. In an example, the rod reducer  200  includes a threaded shaft  210  terminating distally in a grasping element  220  for coupling to the underside of the distal end of a monoaxial pedicle screw assembly  250 . The rod reducer  200  further includes a nut  230  configured to interface with the exterior threading of the shaft  210  and threadedly translate with respect thereto. A claw element  240  having one or more arms, in an example, is coupled to the shaft  210  below the nut  230  and the one or more arms, in a further example, have a rod recess  242  for engaging the spinal rod  140 . 
     In operation, and in continuing reference to  FIGS. 8A-8D , the grasping element  220  is placed under a monoaxial pedicle screw  250 . The claw element  240  engages the proximal side of the spinal rod and the nut  230  is rotated to force the claw element  240  to reduce the rod  140  via the rod recess  242  into the monoaxial pedicle screw assembly  250 . A locking cap is coupled to the monoaxial pedicle screw assembly  250  and the rod reducer  200  is decoupled from the monoaxial pedicle screw assembly  250  by loosening the nut  230  and disengaging the claw  240  from the spinal rod  140 . 
     In an example, and in reference to  FIGS. 9A-9F , a rod reducer  300  is provided that includes a hex nut  310 , a threaded tube  330  having a first leg  332  and a second leg  334 , and a retaining guide ring  320 . In an example, the rod reducer  300  is similar in function and operation to the rod reducer  100  with the exception that instead of the outer drive sleeve  110 , the hex nut  310  is included and functions in conjunction with a hex socket type instrument (not shown) to actuate the rod reducer  300 . The threaded tube  330  is similar in function and operation to the threaded tube  130  but incorporates a hinge design at the proximal end to control the splaying of the first and second legs  332 ,  334 . 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the present description. 
     The above Detailed Description includes references to the accompanying drawings, which form a part of the Detailed Description. The drawings show, by way of illustration, specific embodiments in which the invention can be practiced. These embodiments are also referred to herein as “examples.” All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference. In the event of inconsistent usages between this document and those documents so incorporated by reference, the usage in the incorporated reference(s) should be considered supplementary to that of this document; for irreconcilable inconsistencies, the usage in this document controls. 
     In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. 
     The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more features thereof) may be used in combination with each other. Other embodiments can be used, such as by one of ordinary skill in the art upon reviewing the above description. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. 
     The Abstract is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.