Abstract:
Hip replacement surgery (hip arthroplasty) includes implantation of a distal stem into a femur of a patient, and implantation of a proximal body to connect to the distal stem. A practitioner uses a “trial” or “provisional” to determine a suitable size and configuration for the implantable proximal body, then selects a suitable proximal body from a set of differently sized and shaped proximal bodies. The trial adjusts discretely, as opposed to continuously, and has discrete settings that correspond to the sizes and configurations available in the set of implantable proximal bodies. In some examples, the trials are provided as a kit of parts, where each part in the kit is adjustable for height (i.e., the length of the femur). The parts in the kit can have different, fixed, values for offset (i.e., the lateral distance of the femur to the center of the femoral head in the acetabulum).

Description:
CLAIM OF PRIORITY 
       [0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/846,273, filed on Jul. 15, 2013, the benefit of priority of which is claimed hereby, and which is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND 
       [0002]    A human hip joint connects a femur (sometimes referred to as a thigh bone) to an acetabulum (sometimes referred to as a hip socket) of the pelvis. Hip joints support the weight of a human body, and are important for retaining balance. 
         [0003]    Some types of injury, disease, or degeneration can produce pain and/or restricted motion in a hip joint. One treatment for certain types of damage to a hip joint is surgery. For severe damage, the hip can be surgically replaced. 
       OVERVIEW 
       [0004]    Hip replacement surgery (hip arthroplasty) can include implantation of a distal stem into a femur of a patient, and implantation of a proximal body to connect to the distal stem. Implantable proximal bodies can be presented to a practitioner in the form of a set. The implantable proximal bodies in the set can include discrete combinations of the parameters of height (i.e., the length of the femur) and offset (i.e., the lateral distance from the central axis of the femur to the center of the femoral head in the acetabulum). Height and offset are established quantities in the field of hip replacement surgery. 
         [0005]      FIG. 1  shows an exemplary set  1  of implantable proximal bodies. The set  1  includes twelve parts, each part being a different combination of height and offset. 
         [0006]    In general, the values of height and offset in the set  1  are selected to accommodate the anatomy of most patients, so that at least one of the twelve permutations ensures a suitable fit for the implantable proximal body. In the example of  FIG. 1 , there are four values of height, including 60 mm, 70 mm, 80 mm, and 90 mm. In the example of  FIG. 1 , there are three values of offset, including 35 mm, 40 mm, and 45 mm. The values of height and offset in  FIG. 1  are but one example, and that other suitable values may also be used. 
         [0007]    In order to determine the most appropriate height and offset for a particular patient, a practitioner uses a “trial” or “provisional”, which is shaped and sized similar to the implantable parts, but is removable and can be reused or disposed of. In conventional practice, a practitioner tries on various sizes by temporarily attaching the trial to a stem, and noting the fit of the trial with the anatomy of the patient. Once a best fit is found, the practitioner notes the values of height and offset of the trial that provides the best fit. The practitioner removes the trial, selects an implantable proximal body from the set  1 , the selected body having height and offset values that are closest to the noted values, and implants the selected implantable proximal body. 
         [0008]      FIG. 2  is a schematic drawing of an exemplary kit  10  of adjustable trials. A practitioner can use the trial kit  10  for determining a suitable height and offset of an implantable proximal body for hip replacement surgery. The trial kit  10  includes a fixed portion  20 , and several adjustable portions  30  that can releasably lock to the fixed portion  20  at discrete locations. A practitioner selects one of the adjustable portions  30 , which has a particular, fixed, value of offset associated with it, and slides it from discrete location to discrete location along the fixed portion  20  to determine a fit of the trial at various heights. 
         [0009]    The fixed portion  20  can removably attach to an upper end of a stem  40 . The stem  40  can be implanted at an upper end of a femur of a patient, or can be a trial part that is removably disposed at the upper end of the femur. The stem  40  is not part of the trial kit  10 . The fixed portion  20  has a longitudinal axis (A) extending in a vertical direction. 
         [0010]    The fixed portion  20  has a plurality of indentations  25 A,  25 B,  25 C,  25 D on its exterior surface at specified locations along the longitudinal axis. In the example of  FIG. 1 , there are four indentations, corresponding to the height values of implants in the set  1 ; in other examples, there may be two, three, five, six, or more than six indentations. 
         [0011]    The trial kit  10  includes a plurality of adjustable portions  30 A,  30 B,  30 C, each with a different value of offset. In the example of  FIG. 1 , there are three adjustable portions, corresponding to the offset values of implants in the set  1 ; in other examples, there may be two, four, five, six, or more than six adjustable portions. The adjustable portions  30 A,  30 B,  30 C are intended to be used one at a time, in combination with the fixed portion  20 . Each adjustable portion  30 A,  30 B,  30 C slides vertically along the fixed portion  20 . 
         [0012]    Each adjustable portion  30 A,  30 B,  30 C includes a movable element  35 A,  35 B,  35 C that is biased to contact the exterior surface of the fixed portion  20 , such as by spring loading. As the adjustable portion  30 A,  30 B,  30 C slides along the fixed portion  20 , the movable element  35 A,  35 B,  35 C snaps into one of the indentations  25 A,  25 B,  25 C,  25 D. The snapping releasably locks the adjustable portion  30 A,  30 B,  30 C to the fixed portion  20 . 
         [0013]    Each adjustable portion  30 A,  30 B,  30 C can have a hand-deployed release mechanism, which can retract the movable element  35 A,  35 B,  35 C from one of the indentations  25 A,  25 B,  25 C,  25 D and unlock the adjustable portion  30 A,  30 B,  30 C from the fixed portion  20 . 
         [0014]      FIG. 3  is a schematic drawing of an adjustable trial  50 , as used during a surgical procedure. The adjustable trial  50  can be part of the trial kit  10  of  FIG. 1 . Prior to surgery, a practitioner can examine one or more X-rays or other images of the anatomy of the patient. The anatomy images can provide the practitioner with a good estimate of the offset value, and, optionally, a rough estimate of the height value. During surgery, the practitioner selects an adjustable portion  30  that has an offset value that best corresponds to the estimate. The practitioner slides the selected adjustable portion  30  vertically along the fixed portion  20  from indentation to indentation, checking a fit of the trial at each height value, in order to determine a best height value. The adjustable portion  30  locks at each indentation, so that the practitioner can determine how well the particular offset and height values fit the patient while the adjustable trial  50  is in the locked position. 
         [0015]    In some examples, if the practitioner wishes to determine a fit with more than one offset value, the practitioner can remove one adjustable portion from the fixed portion  20  and use another adjustable portion from the trial kit  10 . Once the practitioner has determined the offset and height values that provide the best fit for the patient, the practitioner notes the best fit offset and height values, removes the adjustable portion  30  from the fixed portion  20 , removes the fixed portion  20  from the stem  40 , selects an implantable proximal body having the noted best fit offset and height values, and surgically implants the selected implantable proximal body onto the stem  40 . Following the surgery, the adjustable trial  50 , as well as other adjustable trials in the trial  10 , can be cleaned, sterilized, and reused for subsequent surgical procedures. Alternatively, the adjustable trial  50  can be designed for a single use, and can be disposed of following a procedure. 
         [0016]    There are several advantages to using the trials discussed herein. For instance, a kit of the adjustable trials can include fewer parts than a comparable kit of non-adjustable trials. For example, in the trial kit  10  in  FIG. 2 , the kit includes three parts, plus a fixed portion, compared with the twelve parts that would be required from the comparable kit of non-adjustable trials. In addition, adjusting the trial during surgery can be significantly quicker than removing one non-adjustable trial from the distal stem and attaching another non-adjustable trial to the distal stem. This can save time and effort for a practitioner. 
         [0017]    It will be understood that the adjustable portions and fixed portions shown in  FIGS. 2 and 3  are but high-level schematic representations of these parts. In practice, the actual parts can include multiple elements and features that are not shown in  FIGS. 2 and 3 .  FIGS. 4-7  show an exemplary full mechanical configuration for an adjustable trial  100 . 
         [0018]    This Overview is intended to provide examples of the present patent document. It is not intended to provide an exclusive or exhaustive explanation of the invention. The Detailed Description below is included to provide further information about the present adjustable trial, kit of adjustable trials, and the corresponding methods. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    In the drawings, which are not necessarily drawn to scale, like numerals describe similar components in different views. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present patent document. 
           [0020]      FIG. 1  is a schematic drawing of an exemplary set of implantable proximal bodies. 
           [0021]      FIG. 2  is a schematic drawing of an exemplary system of adjustable trials. 
           [0022]      FIG. 3  is a schematic drawing of an adjustable trial, as used during a surgical procedure. 
           [0023]      FIG. 4  is an exploded view of an exemplary adjustable proximal trial. 
           [0024]      FIG. 5  is an exploded view of the adjustable portion from the adjustable proximal trial of  FIG. 3 . 
           [0025]      FIG. 6  is a partial cross-section view of the adjustable portion of  FIG. 5 . 
           [0026]      FIG. 7  is a cross-section side view of the assembled adjustable proximal trial of  FIGS. 4-6 . 
           [0027]      FIG. 8  is a flow chart of a method of using the adjustable proximal trial of  FIGS. 4-7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0028]      FIG. 4  is an exploded view of the elements in an exemplary adjustable trial. The example adjustable proximal trial  100  includes a fixed portion  102 , which removably attaches to a stem, and an adjustable portion  104 , which releasably attaches at discrete locations to the fixed portion  102 . 
         [0029]    The fixed portion  102  includes four elements  170 ,  160 ,  150 ,  140 , all of which are coaxial with a longitudinal axis (A) of the fixed portion  102 . A lower body  170  attaches to an upper end of the distal stem, a lower bolt  160  attaches the lower body  170  to the distal stem  40  ( FIG. 1 ), an optional upper extension  150  upwardly extends the length of the lower body  170 , and an optional upper bolt  140  attaches upper extension  150  to the lower body  170 . Breaking the longitudinal length of the fixed portion  102  into two portions, namely the lower body  170  and the upper extension  150 , allows the lower bolt  160  to be tightened and loosened using a common tool, such as a standard hex key, rather than an elongated, customized tool. 
         [0030]      FIG. 4  shows the lower body  170  being generally cylindrical in shape, with the longitudinal axis (A) extending vertically from the proximal (upper) direction to the distal (lower) direction. The lower body  170  has a cylindrical volume  178  in its interior. The cylindrical volume  178  can be accessed from a lower end of the lower body  170 . During operation, the upper end of the distal stem extends into the cylindrical volume  178  of the lower body  170 , as shown in  FIGS. 2 and 3 . The wall of the cylindrical volume  178  is sized and shaped to match an exterior surface of the distal stem, so that the lower body  170  can fit snugly, but removably, over the upper end of the distal stem. 
         [0031]    An upper end of the lower body  170  can include one or more notches  172  around its circumference. The notches  172  can seat the upper extension  150  thereon during assembly of the device. In some examples, the upper end of the lower body  170  can be crenellated instead. The purpose is to prevent rotational misalignment between the upper and lower bodies. The lower body  170  includes female threads  176  at its upper end, which can couple with corresponding male threads  142  on the upper bolt  140 . 
         [0032]    The lower body  170  can include an optional keying feature, which can prevent or reduce angular misalignment about the longitudinal axis (A) between the adjustable portion  104  and the fixed portion  102  while still allowing these two pieces to slide vertically along axis A. Such a keying feature can be an elongation or irregularity on an outer profile of the fixed portion  102 , which mates with a complementary elongation or irregularity on an inner bore  122  within the adjustable portion  104 . For instance, the fixed portion  102  of  FIG. 4  includes a spine  174 , which extends longitudinally along an outer edge of the lower body  170 . The spine  174  can extend into a corresponding groove  132  in the adjustable portion  104 . Other suitable keying features may also be used. 
         [0033]    An exterior surface  179  of the lower body  170  includes one or more indentations  182 ,  184 . In some examples, the indentations  182 ,  184  are disposed along a line parallel to the longitudinal axis (A). In some examples, one or more of the indentations  182 ,  184  extend partially or fully through a wall of the lower body  170 . In some examples, the indentations  182 ,  184  and the spine  174  are on opposite sides of the lower body  170 . In the example of  FIG. 4 , there are two indentations  182 ,  184  on the lower body  170 ; in other examples there can be zero, one, three, four, or more than four indentations on the lower body  170 . 
         [0034]    The lower bolt  160  attaches the lower body  170  to the distal stem. When a practitioner installs an adjustable trial, the practitioner places the lower body  170  over the upper end of the distal stem, then installs the lower bolt  160  to secure the lower body  170  to the distal stem. The lower bolt  160  includes male threads  162  at or near its lower end. When installed, the male threads  162  engage corresponding female threads on the upper end of the distal stem. The lower bolt  160  can be tightened and loosened by inserting a suitable key into one or more sockets  164  at its upper end. In the specific example of  FIG. 4 , the socket  164  is sized and shaped to accommodate a 3.5 mm hex key; other suitable socket sizes and shapes can also be used. 
         [0035]    The upper extension  150  upwardly lengthens the lower body  170 . The upper extension  150  is cylindrical in shape, with an open upper end and an open lower end. The upper extension  150  is sized to match the size and shape of the upper end of the lower body  170 . The upper extension  150  can include one or more teeth  152  at its lower end, to couple with corresponding notches  172  at the upper end of the lower body  170 . In some examples, the lower end of the upper extension  150  is crenellated, with a complementary crenellation to that of the upper end of the lower body  170 . In other examples, one or more teeth can be disposed on the upper end of the lower body  170 , and one or more notches can be disposed on the lower end of the upper extension  150 . The upper extension  150  can include a spine  154  that aligns with the spine  174  on the lower body  170 . The spines  154 ,  174  can extend into a corresponding groove  132  in the adjustable portion, and can be a keying feature of the fixed portion  102 . An exterior surface  156  of the upper extension  150  includes one or more indentations  186 ,  188 . In some examples, the indentations  186 ,  188  align with the indentations  182 ,  184  on the lower body  170 . In the example of  FIG. 4 , there are two indentations  186 ,  188  on the upper extension  150 ; in other examples there can be zero, one, three, four, or more than four indentations on the upper extension  150 . 
         [0036]    The upper bolt  140  attaches the upper extension  150  to the lower body  170 . The upper bolt  140  is generally cylindrical in shape, and can have a hollow interior that extends longitudinally through the upper bolt  140 . Such a hollow interior can be useful for accessing the lower bolt  160  while the fixed portion  102  is assembled. The upper bolt  140  is inserted into the upper end of the upper extension  150 , and extends distally past the lower end of the upper extension  150  into the lower body  170 . The upper bolt  140  has male threads  142  that engage the corresponding female threads  176  in the lower body  170 . A practitioner can tighten and loosen the upper bolt  140  by inserting a suitable key into a socket  144  at the upper end of the upper bolt  140 . In the example of  FIG. 4 , the socket  144  is sized and shaped to accommodate an  8  mm hex key; other suitable socket sizes and shapes can also be used. 
         [0037]      FIG. 5  shows adjustable portion  104 , which includes a housing  110  and three smaller elements  114 ,  116 ,  118 . 
         [0038]    The adjustable portion  104  includes a movable element  130  that is biased to contact the exterior surface  156 ,  179  of the fixed portion  102 . When the adjustable portion  104  slides to one of the indentations  182 ,  184 ,  186 ,  188 , the movable element  130  snaps into the respective indentation to lock the adjustable portion  104  to the fixed portion  102 . 
         [0039]    The housing  110  has a bore  122  therethrough, which can accommodate the fixed portion  102  during operation. The bore  122  is coaxial with the longitudinal axis (A) of the fixed portion  102 . The bore  122  is sized and shaped to accommodate the exterior surface  156 ,  179  of the fixed portion  102  with a clearance sufficient to allow the adjustable portion  104  to slide vertically along the fixed portion  102 . The bore  122  can include a groove or ridge  132  that can mate with the spines  154 ,  174  on the fixed portion  102 . 
         [0040]    The housing  110  can extend laterally away from the bore  122  to a mounting ridge  112 . A generally spherical head (not shown) can be attached to the mounting ridge  112 . 
         [0041]    A spring-loaded element  116  is attached to the housing  110 . A pivot pin  114  extends through a hole  126  in the spring-loaded element  116 , and allows the spring-loaded element  116  to pivot around the pivot pin  114 . The pivot pin  114  attaches the spring-loaded element  116  to the housing  110 , through hole  124  in the housing. The movable element  130  can be disposed at one end of the spring-loaded element  116 . 
         [0042]    The adjustable portion  104  optionally includes a hand-deployed release mechanism that retracts the movable element  130  from the indentation to unlock the adjustable portion  104  from the fixed portion  102  in order to move it to a different indentation if desired. An example of a release mechanism is a depressable portion, such as a push button, that is pivotally arranged to counteract the biasing effect. For instance, if the biasing element is a spring, and expansion of the spring forces the movable element against the exterior surface of the fixed portion, then the push button can be arranged to compress the spring when pushed, so as to counteract the bias of the spring. 
         [0043]    The hand-deployed release mechanism can include one or more of a depressable portion  120 , the pivot pin  114 , a spring  118 , and the movable element  130 . Other suitable hand-deployed release mechanisms may also be used. The depressable portion  120  can be disposed at an opposite end of the spring-loaded element  116 . The spring  118  biases the spring-loaded element  116  against the housing  110 , so that the movable element  130  is biased to contact the exterior surface  156 ,  179  of the fixed portion  102 . During use, a practitioner can use a single hand to release the adjustable portion  104  from the fixed portion  102 , for instance, by depressing the depressable portion  120  with a thumb to release the movable element  130  from an indentation in the fixed portion  102 . 
         [0044]      FIG. 6  shows a partial cross-section of the adjustable portion  104  of  FIG. 5 , in an assembled state. 
         [0045]      FIG. 7  is a side cross-section of an assembled trial implant, to illustrate how the components of  FIGS. 4-6  fit together.  FIG. 7  also shows an optional feature that can ease adjustments of height during use. 
         [0046]    The shapes of the movable element  130  and the indentations  182 - 188  can influence the locking behavior of the adjustable trial  100 . For instance, an upper edge of the movable element  130  and an upper edge of at least one of the indentations  182 ,  184 ,  186 ,  188  can be gently sloped away from the longitudinal axis. For these gentle slopes, when the adjustable portion  104  is locked to the fixed portion  102 , applying an upward translational force to the adjustable portion  104  forces the movable element  130  radially outward from the respective indentation  182 ,  184 ,  186 ,  188 , and unlocks the adjustable portion  104  from the fixed portion  102 . In contrast, a lower edge of the movable element  130  and a lower edge of at least one of the indentations  182 ,  184 ,  186 ,  188  can be more steeply sloped away from the longitudinal axis. For these steep slopes, the movable element  130  remains extended into the respective indentation  182 ,  184 ,  186 ,  188  in the presence of an upward or downward force on the adjustable portion  104 . For these cases, the movable element  130  can be refracted by use of the hand-deployed release mechanism. In the example of  FIGS. 4-7 , the hand-deployed release mechanism includes the depressable portion  120  and the movable element  130 . In other examples, the lower edges are gently sloped, while the upper edges are steeply sloped. In still other examples, both the lower and upper edges are gently sloped; for these cases, the adjustable portion  104  can be unlocked from the fixed portion  102  by forcing the adjustable portion  104  upward or downward, which can eliminate the need for a mechanism such as depressable portion  120  in  FIGS. 4-6 . In still other examples, both the lower and upper edges are steeply sloped. 
         [0047]      FIG. 7  also shows an exemplary set of definitions for offset and height. Offset can be defined as a lateral distance between a longitudinal axis (A) of the proximal body and a junction feature found on the adjustable portion  104 , such as the mounting ridge  112 . Height can be defined as a longitudinal distance between an upper end of the distal stem at the junction feature, such as the mounting ridge  112 , found on the adjustable portion  104 . In some examples, the height values are equally spaced apart; in other examples, the height values are unequally spaced. 
         [0048]    In the configurations of  FIGS. 2-7 , the adjustable portions have a fixed value of offset. In other configurations, the adjustable portions can have adjustable values of offset (not shown). In some of these configurations, the offset is adjustable in discrete increments that can correspond to offset values available in a set of implantable proximal bodies. 
         [0049]      FIG. 8  is a flow chart of an example method  800  for selecting a suitable height and offset of an implantable proximal body from a set of implantable proximal bodies for hip replacement surgery. Each implantable proximal body in the set has a different combination of offset value, included in a discrete plurality of offset values, and height value, included in a discrete plurality of height values. The selection method  800  can be executed using the generic trial kit  10  and adjustable trial  50 , shown in  FIGS. 2 and 3 , or using the specific exemplary configurations of  FIGS. 4-7 . 
         [0050]    Step  802  attaches a fixed portion of an adjustable trial to an upper end of a stem. The fixed portion can include a plurality of indentations. Each indentation can correspond to a height value in the discrete plurality of height values. Step  804  slides a first adjustable portion along the fixed portion to engage a first indentation in the plurality. The first adjustable portion can have a first height value when the first indentation is engaged. Step  806  compares the first adjustable portion at the first height value to an anatomy of a patient to determine a first fit. Step  808  slides the first adjustable portion along the fixed portion to engage a second indentation in the plurality. The first adjustable portion can have a second height value when the second indentation is engaged. Step  810  compares the first adjustable portion at the second height value to the anatomy of a patient to determine a second fit. Step  812  selects the best fit for the patient from the first and second fits. Step  814  selects an implantable proximal body from the set. The selected implantable proximal body can have the offset value of the first adjustable portion and can have the height value of the first adjustable portion at the best fit. Step  816  removes the fixed portion of the adjustable trial from the upper end of the stem, and implants the selected implantable proximal body onto the upper end of the stem. 
         [0051]    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.” Such examples can include elements in addition to those shown or described. However, the inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein. 
         [0052]    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 this document, 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, kit, article, composition, formulation, 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. 
         [0053]    The above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) can 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. The Abstract is provided to comply with 37 C.F.R. §1.72(b), 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. Also, in the above Detailed Description, various features can 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 can lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. 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.