Abstract:
A method of implanting a revision glenoid component in one embodiment includes accessing a previously implanted glenoid component in a scapula, removing the previously implanted glenoid component, identifying an inferior glenoid circle center of the scapula, preparing a glenoid fossa of the scapula to receive a revision glenoid component, selecting a revision glenoid component, and implanting the selected revision glenoid component based upon the identified inferior glenoid circle center in the prepared glenoid fossa.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a divisional application of co-pending U.S. application Ser. No. 13/051,062, filed on Mar. 18, 2011, the entire disclosure of which is incorporated herein by reference, which references U.S. patent application Ser. No. 13/051,011, entitled “Circular Glenoid Method for Shoulder Arthroscopy”, which was filed on Mar. 18, 2011, U.S. patent application Ser. No. 13/051,026, entitled “Combination Reamer/Drill Bit for Shoulder Arthroscopy”, which was also filed on Mar. 18, 2011, and U.S. patent application Ser. No. 13/051,041, entitled “Device and Method for Retroversion Correction Cone for Shoulder Arthroscopy”, which was also filed on Mar. 18, 2011, the contents of which are each incorporated herein by reference. 
     
    
     TECHNICAL FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to the field of orthopedics, and, more particularly, to glenoid component apparatuses for shoulder arthroplasty and methods for using them. 
       BACKGROUND 
       [0003]    As depicted in  FIG. 1 , a typical shoulder or glenohumeral joint is formed in a human body where the humerus  10  movably contacts the scapula  12 . The scapula  12  includes a glenoid fossa  14  that forms a socket against which the head of the humerus  10  articulates. At this socket, the scapula  12  includes cartilage  16  that facilitates such articulation. Beneath the cartilage is subchondral bone  18  that forms a wall of a glenoid vault  20  that defines a cavity which contains cancellous bone  22 . The subchondral bone  18  that forms the glenoid vault  20  defines a glenoid rim  24  at a periphery of the glenoid vault  20  that is attached to the cartilage  16 . During the lifetime of a patient, the glenoid fossa  14  may become worn, especially at its posterior and/or superior portions thereby causing severe shoulder pain and limiting the range of motion of the patient&#39;s shoulder joint. To alleviate such pain and increase the patient&#39;s range of motion, a shoulder arthroplasty may be performed. Arthroplasty is the surgical replacement of one or more bone structures of a joint with one or more prostheses. 
         [0004]    Shoulder arthroplasty often involves replacement of the glenoid fossa of the scapula with a prosthetic glenoid component. The conventional glenoid component typically provides a generally laterally or outwardly facing generally concave bearing surface against which a prosthetic humeral head (or, alternatively, the spared natural humeral head in the case of a glenoid hemi-arthroplasty) may bear during operation of the joint. The conventional glenoid component typically also includes a generally medially or inwardly projecting stem for fixing the glenoid component in a cavity constructed by suitably resecting the glenoid fossa  14  and suitably resecting cancellous bone  22  from the glenoid vault  20 . 
         [0005]    The goal of shoulder arthroplasty is to restore normal kinematics to the shoulder. Accordingly, known systems attempt to replicate the normal kinematics by carefully controlling the geometry of the articulating surfaces in the joint as well as the positioning of the prostheses in the bones in which the prostheses are implanted. Thus, the articulating surface of a humeral component is typically spherical and positioning of the humeral component is accomplished by using the anatomical neck of the humerus as the reference plane for reconstruction of the humeral head. 
         [0006]    In known systems, the glenoid component is positioned in the geometric center of the glenoid fossa. The geometric center is established by generating a line from the most superior point of the glenoid rim to the most inferior point of the glenoid rim (“Saller&#39;s line”). A second line is generated between the most posterior point of the glenoid rim and the most anterior point of the glenoid rim. The intersection of the two generated lines is considered to be the geometric center of the area circumscribed by the glenoid rim. By way of example,  FIG. 2  depicts a sagittal view of the scapula  12 . In  FIG. 2 , Saller&#39;s line  30  extends between the most superior point  32  of the glenoid rim  24  and the most inferior point  34  of the glenoid rim  24 . A second line  36  extends from the most posterior point  38  of the glenoid rim  24  and the most anterior point  40  of the glenoid rim. The geometric center  42  of the glenoid fossa  14  is located at the intersection of the line  36  and Saller&#39;s line  30 . As used herein, the terms anterior, posterior, superior, and inferior, unless otherwise specifically described, are used with respect to the orientation of the scapula  12  as depicted in  FIG. 2 . 
         [0007]    Over time, implanted glenoid components can become loosened. Loosened components can result in increased pain for an individual. Correction of the problem, however, may be problematic. For example, replacement of components which are loosened may be complicated by a number of different glenoid deficiencies. Glenoid deficiencies may be classified as central (a void area in the central region of the glenoid fossa), peripheral (a void area in the glenoid rim area), or combined (a void area extending from the central region of the glenoid fossa to the glenoid rim area). Replacement of components in the presence of mild or moderate deficiencies, particularly when limited to the central region, may be accomplished using known components with or without bone grafting to fill remaining void areas. In cases involving large central deficiencies and combined deficiencies, however, other procedures such as allografting are required. Once the grafted material has been incorporated into the glenoid, a second surgery is performed to implant a replacement component into the allograft. 
         [0008]    An alternative to grafting procedures is customization of components for the particular patient deficiency. Of course, customization increases the costs for a given procedure. Moreover, obtaining reproducible results is difficult when each procedure is unique. 
         [0009]    There remains a need for a glenoid component that allows for establishing normal kinematics in revision procedures. There is a further need for a technique, instrumentation, and implant that facilitates positioning of such a component even when the glenoid has a variety of deficiencies. A glenoid component that can be positioned in a manner that reduces the amount of bone that is required to be removed without overly complicating the implant procedure is also needed. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention in one embodiment provides a method of implanting a revision glenoid component including accessing a previously implanted glenoid component in a scapula, removing the previously implanted glenoid component, identifying an inferior glenoid circle center of the scapula, preparing a glenoid fossa of the scapula to receive a revision glenoid component, selecting a revision glenoid component, and implanting the selected revision glenoid component based upon the identified inferior glenoid circle center in the prepared glenoid fossa. 
         [0011]    In another embodiment, a method of implanting a revision glenoid component includes obtaining an image of a scapula, identifying an inferior glenoid circle center of the scapula based upon the image, selecting a revision glenoid component, removing a previously implanted glenoid component from the scapula, preparing a glenoid fossa of the scapula to receive a prosthesis, and implanting the selected revision glenoid component in the prepared glenoid fossa based upon the identified inferior glenoid circle center. 
         [0012]    The above-noted features and advantages of the present invention, as well as additional features and advantages, will be readily apparent to those skilled in the art upon reference to the following detailed description and the accompanying drawings, which include a disclosure of the best mode of making and using the invention presently contemplated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  depicts a coronal view of an anatomically normal shoulder joint. 
           [0014]      FIG. 2  depicts a sagittal view of the shoulder joint of  FIG. 1 ; 
           [0015]      FIG. 3  depicts a front perspective view of a retroversion glenoid component that may be implanted in a scapula in accordance with principles of the invention; 
           [0016]      FIG. 4  depicts a front perspective view of the base of the retroversion glenoid component of  FIG. 3  that may be implanted in a scapula in accordance with principles of the invention; 
           [0017]      FIG. 5  depicts a top plan view of the base of the retroversion glenoid component of  FIG. 3 ; 
           [0018]      FIG. 6  depicts a side cross-sectional view of the base of the retroversion glenoid component of  FIG. 3 ; 
           [0019]      FIG. 7  depicts a front perspective view of the articulating component of the retroversion glenoid component of  FIG. 3 ; 
           [0020]      FIG. 8  depicts a side cross-sectional view of the articulation component of the retroversion glenoid component of  FIG. 3 ; 
           [0021]      FIG. 9  depicts a side cross-sectional view of the retroversion glenoid component of  FIG. 3 ; 
           [0022]      FIG. 10  depicts a medical procedure that may be used to implant the retroversion glenoid component base of  FIG. 3  into a scapula using a kit that includes a guide pin and a combined reaming/planing tool; 
           [0023]      FIG. 11  depicts a sagittal view of a scapula with an implanted glenoid component which exhibits severe central bone loss resulting in undesired movement of the implanted glenoid component and which has been accessed in accordance with the procedure of  FIG. 10 ; 
           [0024]      FIG. 12  depicts a sagittal view of the scapula of  FIG. 11  after the previously implanted glenoid component has been removed; 
           [0025]      FIG. 13  depicts a front perspective view of the scapula of  FIG. 11  with a guide pin placement guide positioned to guide placement of the guide pin such that the guide pin is aligned with the glenoid axis of the scapula; 
           [0026]      FIG. 14  depicts a side perspective view of the guide pin of  FIG. 13  used to guide a combined reaming/planning device that may be included in a kit; 
           [0027]      FIG. 15  depicts a partial bottom perspective view of the combined reaming/planning device of  FIG. 14  showing a planning portion and a reaming portion; 
           [0028]      FIG. 16  depicts a side perspective view of the scapula of  FIG. 14  after a cavity has been reamed and after the glenoid has been repaired by using bone graft and a compactor to replace bone loss areas about the cavity; 
           [0029]      FIG. 17  depicts the side perspective view of the scapula of  FIG. 16  with the guide hole of a base component aligned with the guide pin such that the base component will be positioned in alignment with the glenoid axis of the scapula; 
           [0030]      FIG. 18  depicts a sagittal plan view of the scapula of  FIG. 17  with the base component rotated such that fasteners inserted into two of the fastener holes of the base can access a lateral pillar and a spina pillar of the scapula; 
           [0031]      FIG. 19  depicts a cross-sectional view of the scapula of  FIG. 18  with the coupling portion of the selected articulation component aligned with the receptacle of the base component; and 
           [0032]      FIG. 20  depicts a cross-sectional view of the scapula of  FIG. 19  with the articulation component coupled with the base component such that the nadir of the articulation component is positioned at the glenoid axis of the scapula. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    Like reference numerals refer to like parts throughout the following description and the accompanying drawings. 
         [0034]      FIG. 3  depicts a retroversion glenoid component  100 . The glenoid component  100  includes a base component  102  and an articulation component  104 . With further reference to  FIGS. 4-6 , the base component  102  includes a wall  106  which extends between a lip  108  and a bottom surface  110 . At the lip  108 , the wall  106  defines a circular outer periphery that is slightly larger than the circular outer periphery of the wall  106  at the bottom surface  110 . 
         [0035]    The lip  108  defines a receptacle  112  which is substantially cylindrical. The receptacle  112  extends from the lip  108  to a lower surface  114 . Three fastener holes  116 ,  118 , and  120  extend through the lower surface  114  and the bottom surface  110 . A guide hole  122  also extends through the lower surface  114  and the bottom surface  110 . The guide hole  122  and the receptacle  112  are centrally located. Accordingly, the guide hole  122 , the receptacle  112 , and the outer wall  106  define a unitary axis  124 . 
         [0036]    The articulating component  104 , depicted in  FIGS. 6 and 7 , includes a spherical articulating surface  134  and a coupling portion  136 . The coupling portion  136  is substantially cylindrical in shape and sized with a diameter slightly larger than the diameter of the receptacle  112 . The articulating surface is positioned with a nadir  138  located on a central axis  140  of the articulating component  104 . Accordingly, when the articulation component  104  is coupled with the base component  102  as depicted in  FIG. 9 , the nadir  138  is located on the axis  124  of the base component. 
         [0037]    The glenoid component  100  in this embodiment is modular, but in other embodiments may be integrally formed. Integrally formed units may be made from a durable biocompatible plastic or any other suitable durable biocompatible material. For example, the glenoid component  100  may be made from a polyethylene. One particular polyethylene that is well suited for glenoid component  100  is a high molecular weight polyethylene, for example ultra-high molecular weight polyethylene (“UHMWPE”). One such UHMWPE is sold as by Johnson &amp; Johnson of New Brunswick, N.J. as MARATHON™ UHMWPE and is more fully described in U.S. Pat. Nos. 6,228,900 and 6,281,264 to McKellop, which are incorporated herein by reference. 
         [0038]    In the embodiment of  FIG. 3  wherein the articulation component  104  and the base component  102  are separately formed, the various components may be made from different materials. Thus, the articulating surface  134  may be made from UHMWPE, while the coupling portion  136  and the base component  102  may be made from a suitable biocompatible metal such as, for example, a cobalt chromium alloy, a stainless steel alloy, a titanium alloy, or any other suitable durable material. In this embodiment, the articulating surface  134  is secured to the coupling portion  136  in any suitable manner. For example, articulating surface  134  may be bonded to coupling portion  136 , or articulating surface  134  could be made from polyethylene and compression molded to coupling portion  136 . Alternately, the articulating surface  134  may be glued to the coupling portion  136 , for example, an adhesive. Alternatively, articulating surface  134  may be mechanically interlocked to the coupling portion  136  by taper locking or otherwise press-fitting the articulating surface  134  into the coupling portion  136  and the coupling portion  136  may include any other suitable interlocking features, for example, rib(s), lip(s), detent(s), and/or other protrusion(s) and mating groove(s), channel(s), or indent(s) (not shown). 
         [0039]    In alternative embodiments, one or more of the outer wall  106  and the bottom surface  110  may include a porous coating to facilitate bone in-growth into the glenoid component  100 . The porous coating may be any suitable porous coating and may for example be POROCOAT®, a product of Johnson &amp; Johnson of New Brunswick, N.J. and more fully described in U.S. Pat. No. 3,855,638 to Pilliar, which is incorporated herein by reference. 
         [0040]    The glenoid component  100  may be included in a kit incorporating instrumentation that may be used to facilitate implantation of the glenoid component  100 . Such instrumentation may include reamers and guide pins, as discussed more fully below. Additionally, the kit may include base components having different heights and widths. Typical heights may range between  10  and  30  millimeters (mm). The kit may further include articulation components having different diameters. In one embodiment, a kit includes articulation components having a variety of diameters ranging from about 23 mm to about 30 mm. 
         [0041]    Preferably, each of the base components in a kit has a receptacle  112  that is shaped and dimensioned the same as the receptacle  112  of each of the other base components  102  while each of the articulation components  104  has a coupling portion  136  that is shaped and dimensioned the same as the coupling portion  136  of each of the other articulation components  104 . Accordingly, any of the articulation components  104  may be coupled with any of the base components  102  in the kit. 
         [0042]    A kit including the glenoid component  100  may be used to implant the glenoid component  100  into a scapula that has previously received a glenoid component in accordance with a procedure  150  depicted in  FIG. 10 . In accordance with the procedure  150 , a scapula is accessed at block  152  in accordance with a desired surgical approach. The previously implanted glenoid component is then removed at block  154 . At block  156 , the center of an inferior glenoid circle, further described in co-pending U.S. patent application Ser. No. 13/051,011, is identified for the scapula. While visual identification of the inferior glenoid circle and hence the center of the inferior glenoid circle is possible once the scapula is accessed at block  152 , the center of the inferior glenoid circle may alternatively be identified prior to or after incising a patient with the aid of imaging or other techniques. 
         [0043]    Once the center of the inferior glenoid circle is identified at block  156 , a glenoid axis which extends through the center of the inferior glenoid circle and is perpendicular to the articulating surface of the glenoid is identified (block  158 ). In alternative approaches, the glenoid axis may extend through the scapula at locations other than the center of the inferior glenoid circle. The glenoid axis may be identified prior to or after incising a patient with the aid of imaging or other techniques. 
         [0044]    Next, a guide pin is positioned in the scapula such that the longitudinal axis of the guide pin is coextensive with the glenoid axis (block  160 ). A circular cavity is then reamed in the glenoid (block  162 ) and the glenoid surface is planed (block  164 ). The circular cavity is preferably slightly larger than the diameter of the revision glenoid base component  102 . This allows for positioning of the base component  102  without placing stress on the glenoid which may be significantly compromised as discussed more fully below. At block  166 , a bone graft compactor is used over the guide pin, if needed, to fill in void areas of the glenoid which are not needed for receiving the revision glenoid component. The guide hole  122  of the base component  102  is then aligned with and inserted onto the guide pin (block  168 ). 
         [0045]    Using the guide pin as a guide, the base component  102  is then implanted in the prepared glenoid (block  170 ). Because the guide pin is positioned on the glenoid axis and because the guide pin is positioned within the guide hole  122 , using the guide pin ensures that the central axis  124  of the base component (see  FIG. 6 ) is aligned with the glenoid axis. At block  172 , the base component  122  may further be rotated about the guide pin to align one or more of the fastener holes  116 ,  118 , and  120  with a respective one of the pillars of the scapula as described by A. Karellse, et al., “Pillars of the Scapula”, Clinical Anatomy, vol. 20, pp. 392-399 (2007). Typically, at least two of the fastener holes  116 ,  118 , and  120  may be positioned so as to access the lateral and spina pillars. Rotation of the base component  102  is facilitated since the cavity in the glenoid is slightly larger than the base component  102  as discussed above. 
         [0046]    The guide pin may then be removed (block  174 ) and one or more fasteners may be inserted through fastener holes  116 ,  118 , and  120  to affix the base component  102  to the scapula (block  176 ). To ensure firm fixation of the base component  102 , it is preferred that one or even two fasteners extend into solid bone material within one or more of the pillars of the scapula. The fastener holes  116 ,  118 , and  120  may be configured to allow for variable angle fastener placement to assist in achieving a firm fixation. A desired articulation component is then obtained (block  178 ) and the coupling portion  136  is aligned with the receptacle  112  (block  180 ). The coupling portion  136  is then moved into the receptacle  112  and the articulation component  104  is coupled to the base component  102  (block  182 ). Coupling may be facilitated by forming the coupling portion  136  and he receptacle  112  to form a friction fit, Morse taper, etc. Once the articulation component  104  is coupled to the base component  102 , the nadir  138  will be aligned with the glenoid axis since the articulation component  104  is configured to couple with the base component  102  such that the nadir  138  is on the axis  140  as discussed above. 
         [0047]      FIGS. 11-20  depict a scapula  50  at various points of the procedure  220 . In  FIG. 11 , the scapula  12  is depicted after block  152  with a previously implanted glenoid component  52 .  FIG. 12  depicts the scapula  50  after the component  52  has been removed. The scapula  50  in  FIG. 12  exhibits severe central bone loss which has resulted in instability of the glenoid component  52 . The methods and devices disclosed herein may be used in performing a retroversion glenoid implantation in the presence of a variety of glenoid deficiencies including central, peripheral, and combined deficiencies ranging from mild to severe. Because the base component  102  is not press fit in to the scapula as discussed above, the potential of fracturing a portion of the scapula even in the presence of severe deficiencies is reduced. 
         [0048]      FIG. 13  depicts a guide pin  190  and a guide pin placement guide  192  that may be included in a kit used to perform a revision glenoid component implantation procedure. The guide pin placement guide  192  is positioned on the scapula  50  substantially centered upon the inferior glenoid circle. The guide pin  190  is thus positioned in the scapula  50  with the longitudinal axis of the guide pin  190  aligned with the glenoid axis. 
         [0049]      FIG. 14  depicts the scapula  50  with the guide pin  190  used to guide a combination reaming device  194  that may also be included in a kit in accordance with the present disclosure. The combination reaming device  194  includes a shaft  196  and a working portion  198 . The shaft  196  and the working portion  198  are cannulated to allow the guide pin  190  to be used to precisely position the combination device  194 . The working portion  198  includes an outer planing portion  202  and a central reaming portion  204 . The planing portion  202  and the central reaming portion  204  allow for simultaneous reaming and planing of the glenoid surface. Alternatively, two separate devices may be used sequentially. 
         [0050]    Once the scapula  50  has been reamed and planed, some areas of deficiency may be present. Accordingly, bone grafting material may be used to fill the void areas. In one embodiment, a kit includes a cannulated compactor which is shaped like the reaming portion  204 . The cannulated compactor may be guided by the guide pin  190  to compact bone graft material  210  (see  FIG. 16 ) while maintaining or finally forming a cavity  212  that is shaped slightly larger than the outer wall  106  of the base component  102 . 
         [0051]    The guide hole  202  is then aligned with the guide pin  190  as depicted in  FIG. 17  and the base component  102  is guided by the pin  190  into the cavity  212 . The base component  102  is then rotated within the cavity  212  as desired to position the fastener holes  116 ,  118 , or  120  to allow a fastener passed therethrough to be fixed into solid bone. By way of example,  FIG. 18  depicts the base component  102  positioned such that a fastener passing through the fastener hole  116  may be fixed in the lateral pillar while a fastener passing through the fastener hole  118  may be fixed in the spina pillar. Thus, even though some or all of the base component  102  may be positioned on bone graft  210  (see, e.g.,  FIG. 19 ), the base component may be solidly fixed to the scapula  50 . Thus, even when bone graft material  210  is used to fill in deficient areas of the scapula  50 , a second surgery is not required. 
         [0052]    Once the base  102  is fixed to the scapula  50  and the guide pin  190  is removed, in any desired sequence, the coupling portion  136  of the selected articulation component  104  is aligned with the receptacle  112  of the base component  102  as depicted in  FIG. 19 . The coupling portion  136  is then moved into the receptacle  112  and the articulation component  104  is coupled to the base component  102  in any desired manner, such as by a Morse taper fit between the coupling portion  136  and the receptacle  112 , resulting in the configuration of  FIG. 20 . In  FIG. 20 , the nadir  138  is located on the glenoid axis since the base component  102  was fixed with the axis  124  of the guide hole  122  aligned with the glenoid axis as discussed above. 
         [0053]    While the foregoing examples detailed only a single glenoid component  100 , a kit may incorporate a number of different glenoid components. Each glenoid component in the kit may be of a different diameter. Additionally, the procedure  150  may be modified in a number of ways in addition to those discussed above. By way of example, while in the above example the glenoid component  100  was implanted with the nadir  138  aligned with the inferior glenoid circle center at block  182 , the nadir  138  may alternatively be offset from the inferior glenoid circle center. For example, the nadir  138  may be offset from the inferior glenoid circle center by about 1.1 mm in a direction superiorly and posteriorly from the inferior glenoid circle center by positioning the guide pin  190  at the offset location at block  160 . Imaging and computer based systems may be used to assist in the positioning of the glenoid component at this location. 
         [0054]    Moreover, while a specific sequence was described in the procedure  150 , many of the steps may be performed in a different order and/or simultaneously with other of the steps. 
         [0055]    In accordance with the methods described above, a glenoid component with a spherical articulating surface is implanted at or very near to the spinning point of a shoulder in a revision procedure. Because of the location of the glenoid component, a humeral component with a radius of curvature matched to the radius of curvature of the articulating surface may be used to provide a constrained fit. As used herein, the term “matched” means a difference in the radii of curvature of the articulating surfaces of less than 2 mm. 
         [0056]    The foregoing description of the invention is illustrative only, and is not intended to limit the scope of the invention to the precise terms set forth. Further, although the invention has been described in detail with reference to certain illustrative embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.