Abstract:
A method for replacing a proximal interphalangeal joint with a modular implant assembly is provided. During a first surgical procedure, a first stem component of the implant assembly having a first articulation component removably attached thereto is implanted in a proximal phalanx bone. A second stem component of the implant assembly having a second articulation component removably attached thereto is implanted in a middle phalanx bone. During a second surgical procedure performed after the first surgical procedure, the first articulation component is removed from the first stem component and the second articulation component is removed from the second stem component. A third articulation component is attached to the first stem component and a fourth articulation component is attached to the second stem component. The second surgical procedure is performed without removing the first stem component from the first bone and without removing the second stem component from the second bone.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/695,425 filed on Jan. 28, 2010. The entire disclosure of the above application is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to anatomical implants, such as a modular proximal interphalangeal joint. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Disorders of the proximal interphalangeal (“PIP”) joint, including trauma and arthritis, can be treated non-surgically with splints, injections, and medications. In severe cases, surgery may be required. Surgical options include fusion and joint replacement. Fusion can relieve pain and restore pinch strength; however, motion in the joint is lost. PIP joint implants can be used to restore joint motion. While current PIP joint implants are suitable for their intended use, they are subject to improvement. For example, there is a need for a PIP joint implant having improved modularity, enhanced sizing options, and enhanced options with respect to degree of joint constraint. 
     SUMMARY 
     This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
     The present teachings provide for a method for replacing a proximal interphalangeal joint with a modular implant assembly. The method includes the following: during a first surgical procedure, implanting a first stem component of the implant assembly having a first articulation component removably attached thereto in a proximal phalanx bone and implanting a second stem component of the implant assembly that is substantially the same as the first stem component and has a second articulation component removably attached thereto in a middle phalanx bone, the first articulation component and the second articulation component cooperate to provide the implant assembly with a first degree of articulation constraint; during a second surgical procedure performed after the first surgical procedure, removing the first articulation component from cooperation with the first stem component and removing the second articulation component from cooperation with the second stem component; and further during the second surgical procedure attaching a third articulation component of the implant assembly to the first stem component and attaching a fourth articulation component of the implant assembly to the second stem component, the third articulation component and the fourth articulation component cooperate to provide the implant assembly with a second degree of articulation constraint that is different than the first degree of articulation constraint. The second surgical procedure is performed without removing the first stem component from the first bone and without removing the second stem component from the second bone. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1A  is a top view of a semi-constrained anatomical implant assembly according to the present teachings implanted in a finger to replace a proximal interphalangeal (“PIP”) joint; 
         FIG. 1B  is a side view of  FIG. 1A ; 
         FIG. 2A  is an exploded perspective view of the implant assembly of  FIGS. 1A and 1B ; 
         FIG. 2B  is a cross-sectional view of the implant assembly of  FIG. 1B ; 
         FIG. 3A  is a top perspective view of a distal stem and a distal articulation of the implant assembly of  FIGS. 1A and 1B ; 
         FIG. 3B  is a bottom perspective view of the distal stem and the distal articulation of the implant assembly of  FIGS. 1A and 1B ; 
         FIG. 3C  is a cross-sectional view taken along line  3 C- 3 C of  FIG. 3A ; 
         FIG. 4  is a top perspective view of a proximal stem and a proximal articulation of the implant assembly of  FIGS. 1A and 1B ; 
         FIG. 5A  is a top exploded perspective view of an additional distal stem and distal articulation in accordance with the present teachings; 
         FIG. 5B  is a cross-sectional view taken along line  5 B- 5 B of  FIG. 5A ; 
         FIG. 6A  is a top perspective view of another distal stem and distal articulation in accordance with the present teachings; 
         FIG. 6B  is a cross-sectional view taken along line  6 B- 6 B of  FIG. 6A ; 
         FIG. 7A  is a top perspective view of an additional distal stem and distal articulation in accordance with the present teachings; 
         FIG. 7B  is a cross-sectional view taken along line  7 B- 7 B of  FIG. 7A  in accordance with the present teachings; 
         FIG. 8A  is a top perspective view of yet another distal stem and distal articulation in accordance with the present teachings; 
         FIG. 8B  is a cross-sectional view taken along line  8 B- 8 B of  FIG. 8A ; 
         FIG. 9  is a top view of another embodiment of a semi-constrained anatomical implant assembly according to the present teachings implanted in a finger to replace a PIP joint; 
         FIG. 10A  is a top view of a constrained anatomical implant assembly according to the present teachings implanted in a finger to replace a PIP joint; 
         FIG. 10B  is a side view of  FIG. 10A ; 
         FIG. 11A  is an exploded perspective view of the implant assembly of  FIGS. 10A and 10B ; 
         FIG. 11B  is a cross-sectional view of  FIG. 10B ; and 
         FIG. 12  is an anatomical implant assembly kit according to the present teachings. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath”, “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     With initial reference to  FIG. 1 , a proximal interphalangeal (“PIP”) joint implant assembly according to the present teachings is illustrated at reference numeral  10 . The implant assembly  10  is shown implanted in a human finger to repair the PIP joint, which is located between the proximal phalanx bone and the middle phalanx bone. The implant assembly  10  can provide semi-constrained articulation between the proximal and middle phalanx bones. 
     With additional reference to  FIGS. 2-4 , the implant assembly  10  generally includes a distal stem  12 , a distal semi-constrained articulation  14 , a proximal stem  16 , and a proximal semi-constrained articulation  18 . 
     The distal stem  12  includes an elongated base portion, or post,  20 , a flange  22 , and an interlocking detail  24 . The elongated base portion  20  is generally conical and tapered from a first end that is proximate to the flange  22  to a second end that is distal to the flange  22  and terminates at a distal tip  25 . The elongated base portion  20  can include a porous coating  26  and/or include Regenerex® Porous Titanium Construct to promote bone in-growth, which enhances fixation to the proximal phalanx. Regenerex® is offered by Biomet of Warsaw, Ind. A longitudinal axis A of the post  20  extends through the distal tip  25 , through the flange  22 , and through the interlocking detail  24 . 
     The flange  22  includes a planar bone engagement surface  28  and a planar articulation support surface  30 , which is opposite to the bone engagement surface  28 . The planar articulation support surface  30  extends across a plane that is perpendicular to the longitudinal axis A. The elongated base portion  20  extends from the bone engagement surface  28 . The interlocking detail  24  is at the planar articulation support surface  30 . The bone engagement surface  28  can include the porous coating  26  and/or Regenerex® to enhance fixation between the flange  22  and the proximal phalanx. 
     The interlocking detail  24  includes a T-shaped rail having a base portion  32  and a connecting flange  34  that each extend across at least a portion of the support surface  30 . The connecting flange  34  is mounted to the base portion  32  and is spaced apart from the planar articulation support surface  30  to define a gap  36  there between. The connecting flange  34  defines a bore  38  configured to receive a fastener, as further described herein. 
     The distal semi-constrained articulation  14  generally includes an articulating surface  40  and a stem engaging surface  42 . The stem engaging surface  42  is opposite to the articulating surface  40 . As illustrated in  FIGS. 1-3 , the articulating surface  40  includes a raised center portion  43  that is between, and stands proud of, a pair of side surfaces  45  that generally slope away from the center portion  43  and are shaped to articulate with the proximal articulation  18 . 
     The articulation  14  defines a locking mechanism  44  with an opening  46  that extends from the stem engaging surface  42  to a side of the articulation surface  40 . The opening  46  transitions to a locking recess  48  defined within the articulation  14 . The locking recess  48  has a generally rectangular shape that is sized to receive the connecting flange  34 . A bore  50  extends from an exterior of the articulation  14  to the locking recess  48  and is configured to receive a suitable fastener  52 , such as a pin or screw for example. As illustrated in  FIG. 3C , with the interlocking detail  24  seated within the locking recess  48 , the fastener  52  is inserted through the bore  50  to engage the bore  38  of the connecting flange  34  and secure the distal stem  12  to the articulation  14 . 
     With additional reference to  FIG. 4 , the proximal stem  16  is substantially similar to the distal stem  12 , but has a slightly longer length and/or larger diameter base portion  20 ′. Therefore, similar features are designated with the same reference numbers; the reference numbers of the proximal stem  16  include the prime (′) symbol. With respect to the similar features, the description of the distal stem  12  is sufficient to describe the proximal stem  16  as well. 
     The semi-constrained proximal articulation  18  generally includes an articulating surface  60  and a stem engaging surface  62  that is opposite to the articulating surface  60 . The articulating surface  60  includes a pair of spaced apart lobes  63  that are each generally hemispherical and concave with respect to the stem engaging surface  62  and shaped to articulate with one of the side surfaces  45  of the distal articulation  14 . Between the lobes  63  is a recessed surface  65  that is sized and shaped to articulate with the center portion  43  of the distal articulation  14 . 
     The proximal articulation  18  further includes a locking mechanism  64  that is substantially similar to the locking mechanism  44  of the distal articulation  14 . To attach the proximal articulation  18  to the proximal stem  16  the interlocking detail  24 ′ is mated with the locking mechanism  64  and a fastener  66  is inserted through a bore  68  of the articulation  18  and secured in the bore  38 ′ of the interlocking detail  24 ′. 
     The distal semi-constrained articulation  14  and the proximal semi-constrained articulation  18  can each be made of any suitable material. The articulations  14  and  18  can include similar or different materials in similar or different compositions. For example, each articulation can include a metal, a polymer, or combinations thereof. 
     Suitable metals include, for example, CoCr, titanium, and combinations thereof. Suitable polymers include one or more of ultra-high molecular weight polyethylene, pyrocarbon, silicone, polyether ether ketone (“PEEK”), carbon fiber reinforced PEEK (such as PEEK-OPTIMA® from Invibio, Ltd. of the United Kingdom), and/or vitamin E stabilized highly crosslinked polyethylene (HXLPE), such as is disclosed in U.S. patent application Ser. No. 10/757,551 by Muratoglu et al., which was filed on Jan. 15, 2004 and issued as U.S. Pat. No. 7,431,874 on Oct. 7, 2008. U.S. Pat. No. 7,431,874 and application Ser. No. 10/757,551 are incorporated by reference herein, as well as are all patent applications and issued patents that rely thereon for priority including the following U.S. patent application Ser. No. 11/104,580 filed on Apr. 13, 2005; Ser. No. 11/104,582 filed on Apr. 13, 2005; Ser. No. 11/564,594 filed on Nov. 29, 2006; Ser. No. 11/948,393 filed on Nov. 30, 2007; and Ser. No. 12/464,235 filed on May 12, 2009. An exemplary vitamin E stabilized HXLPE that may be used includes E-Poly™ offered by Biomet Orthopedics, Inc. of Warsaw, Ind. 
     Any suitable manner of interconnecting the stems  12  and  16  with the respective articulations  14  and  18  can be used. For example and with reference to  FIGS. 5A and 5B , the distal stem  12  can include an interlocking flange  100  extending from a side of the flange  22  opposite to the elongated base portion  20 . The flange  100  defines an annular recess  102  in which an annular ring  104  is seated. The annular ring  104  can be made out of any suitable material, such as a metal or a polymer. The articulation  14  defines a cavity  106  that is shaped and sized to receive the flange  100 . The cavity  106  defines an annular seat  108 . As illustrated in  FIG. 5B , to lock the distal articulation  14  to the distal stem  12 , the distal articulation  14  is pressed onto the distal stem  12  so that the flange  100  is seated within the annular seat  108  and the annular ring  104  compresses and then snaps into the annular seat  108 . This same interlocking arrangement can also be used to attach the proximal semi-constrained articulation  18  to the proximal stem  16 . 
     With additional reference to  FIGS. 6A and 6B , the distal stem  12  can define a locking receptacle  110  within the flange  22  and a locking flange  112 . The distal semi-constrained articulation  14  can include flexible locking tabs  114  extending from the stem engaging surface  42 . The locking tabs  114  are snapped into the locking receptacle  110  to secure the distal semi-constrained articulation  14  to the distal stem  12 . This same interlocking arrangement can also be used to attach the proximal semi-constrained articulation  18  to the proximal stem  16 . 
     With additional reference to  FIGS. 7A and 7B , the distal stem  12  can include a truncated conical locking protrusion  120  extending from the articulation support surface  30  of the flange  22 . The distal semi-constrained articulation  14  can define a conical recess  122  within the stem engaging surface  42  that is sized and shaped to receive the truncated conical locking protrusion  120 . The surfaces of the locking protrusion  120  and the conical recess  122  are angled to provide a Morse taper lock there between. Thus, to secure the distal semi-constrained articulation  14  to the distal stem  12 , the articulation  14  is seated on the flange  22  so that protrusion  120  mates with the conical recess  122  to form a Morse taper lock. This same interlocking arrangement can also be used to attach the proximal semi-constrained articulation  18  to the proximal stem  16 . 
     With additional reference to  FIGS. 8A and 8B , the distal stem  12  can include a dovetail locking taper  130  extending from the articulation support surface  30  of the flange  22 . The taper  130  can include a pair of stem protuberances  134   a  and  134   b  that extend respectively from tapered surfaces  136   a  and  136   b  of the dovetail locking taper  130 . The stem protuberances  134   a  and  134   b  each span a distance of approximately one-half a length of the tapered surfaces  136   a  and  136   b  respectively. The stem protuberances  134   a  and  134   b  are rigid. 
     The distal semi-constrained articulation  14  can define a dovetail shaped recess  132  sized and shaped to securely receive the dovetail locking taper  130 . The recess  132  can include a pair of recess protuberances  138   a  and  138   b . The recess protuberances  138   a  and  138   b  include a compressible material such that they can pass by the stem protuberances  134   a  and  134   b  as part of a locking mechanism. The recess protuberances  138   a  and  138   b  span about one-half a length of the recess  132 . The other half of the recess  132  defines concavities  140   a  and  140   b  that are sized and shaped to receive the stem protuberances  134   a  and  134   b.    
     To mount the articulation  14  to the distal stem  12 , the articulation  14  is slid over the dovetail locking taper  130  such that the stem protuberances  134   a  and  134   b  pass over the compressible recess protuberances  138   a  and  138   b . After the stem protuberances  134   a  and  134   b  completely pass over the recess protuberances  138   a  and  138   b , the stem protuberances  134   a  and  134   b  can lock into the pair of concavities  140   a  and  140   b  respectively. The concavities  140   a  and  140   b  are configured in dimension to inversely match the stem protuberances  134   a  and  134   b  such that locking occurs. This same interlocking arrangement can also be used to attach the proximal semi-constrained articulation  18  to the proximal stem  16 . 
     The various features described above for coupling the stems  12  and  16  to their respective articulations  14  and  18  include the interlocking details  24  and  24 ′ as part of the stems  12  and  16  and various different interlocking features provided on and defined by the articulations  14  and  18 . However, this arrangement can be reversed such that the interlocking details  24  and  24 ′ are at the articulations  14  and  18  and the various other interlocking features of the articulations  14  and  18  are provided on the stems  12  and  16 . Furthermore, the interlocking details  24  and  24 ′ are generally described as male members protruding from the respective flanges  22  and  22 ′ and the various interlocking features of the articulations  14  and  18  are generally described as female members recessed within and defined by the articulations  14  and  18 . However, this arrangement can be reversed such that the interlocking details  24  and  24 ′ are formed as female members recessed within and defined by the flanges  22  and  22 ′ and the various interlocking features of the articulations  14  and  18  are male members extending from the stem engaging surfaces  42  and  62  and configured to mate with the female interlocking details  24  and  24 ′. 
     With additional reference to  FIG. 9 , the implant assembly  10  can be reversed such that the distal semi-constrained articulation  14  is mounted to the proximal stem  16  and the proximal semi-constrained articulation  18  is mounted to the distal stem  12 . 
     With additional reference to  FIGS. 10A and 10B , an additional PIP joint implant assembly according to the present teachings is illustrated at reference numeral  200 . The implant assembly  200  can provide constrained articulation between the proximal and middle phalanx bones. 
     With additional reference to  FIGS. 11A and 11B , the implant assembly  200  generally includes the same distal stem  12  and the same proximal stem  16  described herein in the context of the implant assembly  10 . However, in place of the semi-constrained articulations  14  and  18 , a distal constrained articulation  202  and a proximal constrained articulation  204  are provided and mounted to the distal stem  12  and the proximal stem  16  respectively. 
     The distal constrained articulation  202  includes an articulation base  206  having a stem engaging surface  208  and an articulation flange or hinge  210 . The stem engaging surface  208  is generally planar and is on a first side of the articulation base  206 . The articulation flange  210  extends from a second side of the articulation base  206  that is opposite to the stem engaging surface  208 . The articulation flange  210  is offset from a center of the articulation base  206 . The articulation flange  210  defines a through bore  212  having a longitudinal axis that is 90° degrees relative to an axis extending through the center of the articulation base  206 . 
     The articulation base  206  further defines a locking mechanism  214  that is similar to the locking mechanism  44  of the distal articulation  14 . The locking mechanism  214  defines a cavity  216  that is shaped and sized to securely receive the interlocking detail  24 . With the interlocking detail  24  seated within the cavity  216 , a suitable fastener  218 , such as a pin or screw, can be inserted through a bore  220  of the articulation base  206  and into engagement with the bore  38  of the interlocking detail  24  to secure the distal articulation  202  to the distal stem  12 . 
     The proximal constrained articulation  204  is substantially similar to the distal constrained articulation  202 . Therefore, similar features are designated with the same reference numbers; the reference numbers of the proximal stem  16  and the proximal articulation  204  include the prime (′) symbol. With respect to the similar features, the description of the distal articulation  202  is sufficient to describe the proximal articulation  204  as well. As illustrated in FIG.  10 , a difference between the distal articulation  202  and the proximal articulation  204  is that the flange  210  of the distal articulation  202  is offset from the flange  210 ′ of the proximal articulation  204  so that the axes of the through bores  212  and  212 ′ align and permit the insertion of a suitable connection device  222 , such as a pin, through the bores  212  and  212 ′ to connect the distal articulation  202  to the proximal articulation  204  and allow the articulations  202  and  204  to pivot in a hinge-like manner about the connection device  222 . 
     In place of the locking mechanisms  214  and  214 ′, the distal and proximal articulations  202  and  204 , along with the corresponding stems  12  and  16 , can include any suitable coupling features, such as those described herein and illustrated in  FIGS. 5-8 . 
     The articulations  202  and  204 , as well as the connection device  222 , can include any suitable biocompatible materials, such as the metal and polymeric materials set forth above in the description of the articulations  14  and  18 . The articulations  202  and  204  and the connection device  222  can include the same composition or different compositions. For example, either of the articulations  202  and  204 , as well as the connection device  222 , can be a metal, a polymer, or combinations thereof. 
     With additional reference to  FIG. 12 , the distal stems  12 , the proximal stems  16 , the distal semi-constrained articulations  14 , the proximal semi-constrained articulations  18 , the distal constrained articulations  202 , and the proximal constrained articulations  204  can each be provided in various different sizes and configurations, and grouped together in a kit  300 . The various features of the distal stems  12  and the proximal stems  16  can vary in size and shape in any suitable manner. For example, the elongated base portions  20  and  20 ′ can vary in length and diameter, the flanges  22  and  22 ′ can vary in surface area and thickness, and the interlocking details  24  and  24 ′ can have varying dimensions. The distal articulations  14  and  202  and the proximal articulations  18  and  204  can also vary in size and shape in any suitable manner to accommodate the stems  12  and  14  that the articulations  14 ,  18 ,  202 ,  204  are connected to and to accommodate various PIP joints of different sizes. The kit  300  can also include the fastener  52  and the connection device  222 . 
     Thus, the present teachings provide for stems  12  and  16  to which either semi-constrained articulations  14  and  18  or constrained articulations  202  and  204  can be mounted to. This allows for conversion between a semi-constrained PIP implant and a constrained PIP implant, such as during a revision procedure or trialing, without having to replace the stems  12  and  16 , which are secured within bone in any suitable manner, such as by using bone cement or a press-fit. The implant assemblies  10  and  200  can also be provided with different sized articulations  14 ,  18 ,  202 , and  204  without having to replace the stems  12  and  16  after they are implanted in bone. Further, the connection device  222  can be replaced without having to replace portions of the remainder of the implant assembly  200 . 
     The present teachings are not limited to application in a PIP implant. The present teachings also apply to a variety of other types of joint replacement implants to provide modular implants having stems that can interchangeably connect to a variety of articulations having different sizes and that provide for varying degrees of constraint. For example, the present teachings also apply to metacarpophalangeal (MCP) joint implants, distal interphalangeal joint (DIP) implants, carpometacarpal (CMC) joints, and other small joints, such as finger or toe joints. The present teachings apply to both total joint replacement and hemi joint replacement as well. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.