Abstract:
Disclosed herein are patient-specific cutting guides for guiding a surgical instrument for resecting a portion of a glenoid of a patient. The cutting guides include a base portion having a contact surface shaped to substantially match at least a portion of a cavity of the glenoid. The base portion has a guide hole extending therethrough in which the guide hole has an axis coaxial with an axis of rotation. The cutting guides include one or more stabilization members extending outwardly from the base portion and having a contact surface shaped to substantially match an outer surface of a portion of a scapula of the patient. The stabilization members are oriented to take into account the patient&#39;s anatomy in orienting and stabilizing the guide with respect to the glenoid. The guide hole of the base portion is for guiding the surgical instrument to create a guide hole in the glenoid.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. application Ser. No. 14/124,422, filed on Jan. 29, 2014, which claims the benefit of national phase entry under 35 U.S.C. §371 of International Application No. PCT/US2012/040831 filed Jun. 5, 2012, published in English, which claims the benefit of the filing date of U.S. Provisional Application No. 61/494,579, filed Jun. 8, 2011, entitled, “Patient-Specific Cutting Guide For The Shoulder,” the disclosures of which are hereby incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to patient-specific cutting guides for the shoulder, and in particular it relates to such cutting guides having a patient-specific contact surface shaped to rest on bone in a predetermined manner, the guides having at least one guide hole or slot used to resect bone as preoperatively planned such that a corresponding implant can be located and oriented on the resected bone in a predefined manner 
       BACKGROUND OF THE INVENTION 
       [0003]    Over time and through repeated use, bones and joints can become damaged or worn. For example, repetitive strain on bones and joints (e.g., through athletic activity), traumatic events, and certain diseases (e.g., arthritis) can cause cartilage in joint areas, for example, which normally provides a cushioning effect, to wear down. When the cartilage wears down, fluid can accumulate in the joint areas, resulting in pain, stiffness, and decreased mobility. The same can happen in the case where tendons in a joint become lax or soft tissues in or adjacent the joint tear become damaged or worn. 
         [0004]    Arthroplasty procedures can be used to repair damaged joints. During a typical arthroplasty procedure, an arthritic or otherwise dysfunctional joint can be remodeled or realigned, or an implant or implants can be implanted into the damaged region. Arthroplasty procedures may take place in any of a number of different regions of the body, such as a knee, a hip, a shoulder, or an elbow. 
         [0005]    One type of arthroplasty procedure is a shoulder arthroplasty, in which a damaged shoulder joint is replaced with prosthetic implants. The shoulder joint may have been damaged by, for example, arthritis (e.g., severe osteoarthritis or degenerative arthritis), trauma, or a rare destructive joint disease. 
         [0006]    Implants that are implanted into a damaged region may provide support and structure to the damaged region, and may help to restore the damaged region, thereby enhancing its functionality. Prior to implantation of an implant in a damaged region, the damaged region may be prepared to receive the implant. In the case of a shoulder arthroplasty procedure, one or more of the bones in the shoulder area, such as the humerus and/or glenoid, may be treated (e.g., cut, drilled, reamed, and/or resurfaced) to provide one or more surfaces that can align with the implant and thereby accommodate the implant. Standard alignment instrumentation may be used for locating a position and orientation to resect the humeral head for proper humeral stem placement in the humerus. 
         [0007]    Accuracy in implant alignment is an important factor to the success of the procedure. A one to two millimeter translational misalignment, or a one to two degree rotational misalignment, may result in imbalanced ligaments, and may thereby significantly affect the outcome of the procedure. For example, implant misalignment may result in intolerable post-surgery pain, and also may prevent the patient from having proper deltoid tension or range of motion. 
         [0008]    To achieve accurate implant alignment, prior to treating (e.g., cutting, drilling, reaming, and/or resurfacing) any regions of a bone, it is important to correctly determine the location at which the treatment will take place and how the treatment will be oriented. Currently available instrument and tools do not always enable the surgeon to make the most accurate cuts on the bone surface in preparing the target joint for implantation. Thus, there remains a need for tools that improve the accuracy of the joint resurfacing process. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    Patient-specific cutting guides for resecting the humerus and glenoid in a preoperatively planned manner are described herein. These patient-specific guides are configured to allow a surgeon to accurately and quickly perform a shoulder arthroplasty procedure that substantially restores the natural alignment of the joint. Specifically, the patient-specific guides are shaped such that they matingly receive the regions of the bone to be subjected to a treatment (e.g., cutting, drilling, reaming, and/or resurfacing). The patient-specific guides are also shaped to provide the proper location and orientation of the treatment relative to the regions of the bone. The shaped aspect of the patient-specific guides allows the treatment of the bone regions to be done quickly and with a high degree of accuracy that will allow the implants to restore the patient&#39;s joint to a generally pre-deteriorated state. 
         [0010]    The disclosed guides relate to a prosthetic device system for repairing ball-and-socket type joints in a human body, particular shoulder joints. Applicants incorporate by reference in its entirety herein the disclosure of U.S. Pat. No. 7,537,618 (“the &#39;618 Patent”), which relates to a modular anatomic adjustable prosthetic device system for the shoulder and hip joints. U.S. Pat. Nos. 7,785,370 and 7,785,371 which claim priority to the &#39;618 Patent, the disclosures of which are also incorporated by reference in their entirety herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows the general shoulder joint anatomy of a patient. 
           [0012]      FIG. 2  is a view of a glenoid cavity of the shoulder joint. 
           [0013]      FIG. 3  is a posterior view of a proximal portion of a humerus of the shoulder joint showing a resection line adjacent the anatomical neck of a humerus, the resection line corresponding to the preoperatively planned location and orientation of a humeral stem component that will be implanted in a shoulder arthroplasty procedure. 
           [0014]      FIG. 4  is a view of an embodiment of a patient-specific cutting guide of the present invention for resecting the humerus. 
           [0015]      FIG. 5  is a top view of a humerus stem and glenoid. 
           [0016]      FIG. 6  is a view of an embodiment of a patient-specific cutting guide of the present invention for resecting the glenoid. 
           [0017]      FIG. 7  is a view of the glenoid patient-specific cutting guide shown in  FIG. 6  received in a glenoid cavity of a patient. 
           [0018]      FIG. 8  is an alternate view of the cutting guide shown in  FIG. 6  received in the glenoid cavity of a patient. 
           [0019]      FIG. 9  is a view of a total shoulder arthroplasty prosthesis implant after a humerus and a glenoid of a patient has been resected to receive a humeral stem component and glenoid component, respectively. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  shows the general anatomy of shoulder joint  10  of a patient. Humerus  12  of joint  10  includes a neck portion  13 , a head portion  14  and a shaft portion  17  having a greater tuberosity  16  and a lesser tuberosity  18 . Between greater and lesser tuberosities  16 ,  18  is bicipital groove  15 . As shown in  FIGS. 1-2 , scapula  22  terminates at glenoid  20  having a cavity  21  in which an outer surface  11  of head portion  14  rotates within Along with humerus  12  and scapula  22 , the acromion  24 , rotator cuff  26  and clavicle  28  all provide support to the range of motion of the shoulder joint  10  of the patient. 
         [0021]      FIG. 3  is a posterior view of a proximal portion of humerus  12  of shoulder joint  10 . Head portion  14  includes outer surface  11 . Also shown is bicipital groove  15 , a substantially straight surcical neck line  25  and a curvy anatomical neck line  27 . Outer surface  11 , biciptal groove  15 , substantially straight surcical neck line  25  and curvy anatomical neck line  27  are all anatomical features of humerus  12  that can be used to aid in the designing of one or more patient-specific contact surfaces that may be located a guide  50 , for example, as shown in  FIG. 4 , and thereafter accurately locate guide  50  on humerus  12 . 
         [0022]    Prior to a total shoulder arthroplasty procedure being conducted, shoulder joint  10  is generally compromised through injury or general wear and tear. A compromised joint generally leads to range of motion difficulty and pain for the patient. In a joint  10  that is compromised, head portion  14  and/or glenoid cavity  21  may be degenerated such that the axis of rotation of the shoulder joint is not in the same location as it was prior to joint  10  being compromised. 
         [0023]    The axis of rotation of the shoulder joint varies based upon the type of motion. For flexion and extension, the axis of rotation is a transverse axis though the center of the humeral head. For abduction and adduction, the axis of rotation is a sagittal axis thought the center of the humeral head. For internal and external rotation, the axis of rotation is a vertical axis though the center of the humeral head. 
         [0024]    During a total shoulder arthroplasty procedure, the humerus is resected in order to receive a humeral stem component. In such a procedure, the humeral head is generally resected and the shaft of the humerus is reamed to receive the humeral stem component prosthesis. It is important that the humeral stem component be positioned in the correct location and orientation in order to restore the axis of rotation of joint  10 . Some humeral stem components may include a flange that is adapted to contact a flat portion of resected bone of the humerus in order to correctly position and stabilize the humeral stem component within shaft  17  of humerus  12  such that the axis of rotation of joint  10  may be restored. 
         [0025]    Also during a total shoulder arthroplasty procedure, the glenoid is resected in order to receive a glenoid component. In a shoulder arthroplasty procedure for implanting a reverse shoulder prosthesis, a cavity of the glenoid may be reamed and a guide hole may be drilled in order to receive a central screw extending outwardly from an outer contact surface of the glenoid component. The location and orientation of the guide hole may be based on the shape of the glenoid component, for example, such that the glenoid component can be implanted in the resected glenoid cavity and the axis of rotation of the joint may be restored. It is important that the glenoid component be positioned in the correct location and orientation in order to restore the axis of rotation of joint  10 . The glenoid component preferably has an articular surface corresponding to an outer surface of a humeral head component which is engaged to the humeral stem component implanted at least partially within the shaft of the humerus. Generally, the glenoid component has a diameter that is approximately  6 mm in diameter larger than the humeral stem component. 
         [0026]    As discussed above, humerus  12  must be resected at the correct location and orientation in order for a corresponding humeral stem prosthesis to be accurately implanted in shaft  17  of humerus  12  such that the axis of rotation of the shoulder joint may be restored. Thus, the location and orientation of resection line  30 , as shown in  FIG. 3 , is preoperatively planned according to one aspect of the present invention. Resection line  30  corresponds to the location and orientation of resection slot  68  of guide  50 , as shown in  FIG. 4 , once located and oriented on neck portion  11  and head portion  14  of humerus  12 . 
         [0027]    In order to preoperatively plan the location and orientation of slot  68  of guide  50 , joint  12  first has to be scanned. After joint  10  is scanned using CT or MRI, for example, the images obtained from the scan are used to create a 3D model (not shown) of the shoulder joint. A technician preferably then selects certain points on the 3D model that the patient-specific cutting guide will contact with contact surfaces that match at least a portion of the area of the humerus surrounding the selected points. For instance, the technician may select points located on neck portion  13  of humerus and attach the points with splines. Once a line is created on neck portion  13 , a patient-specific contact surface (not shown) on guide  50  is preferably created to substantially match the contour of the line such that guide  50 , once manufactured, will contact the actual outer surface of humerus  12  in a predetermined location and orientation while being substantially stabilized thereto. Patient-specific cutting guide  50 , as shown in  FIG. 4 , can be manufactured via SLA, milled from a jig blank, or molded, for example. 
         [0028]      FIG. 4  shows patient-specific cutting guide  50  for guiding a surgical instrument, such as a saw blade (not shown) for resecting a portion of humerus  12 . Guide  50  includes a base portion  52  having a contact surface shaped to substantially match an outer surface of a neck portion  13  of humerus  12 . Guide  50  further includes at least one proximal stabilization member  54  extending medially from base portion  52  and having a contact surface  56  shaped to substantially match an outer surface  11  of a head portion  14  of humerus  12 . Preferably, guide  50  also includes at least one distal stabilization member  53  extending distally from base portion  52  and having a contact surface shaped to substantially match an outer surface of a shaft portion  17  of humerus  12 . 
         [0029]    A generally reproducible feature on the humerus is bicipital groove  15 , which contains the long head of the biceps tendon. The contact surface of the distal stabilization member  53  is shaped to match a location on the bicipital groove  15  of humerus  12 . Another generally reproducible feature on the humerus is anatomic neck  27 . The contact surface of base portion  52  of guide  50  is shaped to match a location either on or adjacent to anatomic neck line  27  of humerus  12 . Preferably, guide  50  contacts bone on humerus  12  in at least three locations in order to substantially stabilize guide  50  when it is being used to resect humerus  12 . Proximal stabilization member  54  as well as proximal stabilization member  58  having patient-specific contact surface  59  are preferably used in conjunction with distal stabilization member  53  in order to stabilize guide  50  sufficiently on humerus  12 . 
         [0030]    Guide  50  may also be pinned in place by placing pins through pin holes (not shown) in guide  50  preferably at some point along base portion  52 . Preferably, base portion  52  of guide  50  includes two guide holes adapted to receive a stabilization pin therein for securing guide  50  to humerus  12 . In one embodiment, guide  50  includes a first guide hole located on base portion  52  superior to guide slot  68  and a second guide hole located on base portion  52  anterior to guide slot  68 . 
         [0031]    Base portion  52  of guide  50  includes guide slot  68  for guiding the surgical instrument. Guide slot  68  is preferably located approximately 135° from a line perpendicular to a longitudinal axis of the humeral stem, also referred to as the neck-shaft angle that will be resected. The resected neck-shaft angle preferably matches the neck-shaft angle of the humeral stem component. The neck shaft angle may be greater or less than 135°, but preferably lies between a range of 110° and 160°. Guide slot  68  preferably produces a flat resection cut  32  as shown in  FIG. 9  so that the version is dedicated. Humeral stem version is the positioning of the humeral stem in the correct position in the humeral canal when viewing from the top of humeral head  29  as shown in  FIG. 5 . Lateral side  23  of humeral head  29  is also shown in  FIG. 5 . If a stem is positioned with a trunion of the stem in the A-B direction, this would be 0° retroversion. A stem positioned in the A-C direction is at 30° of retroversion. Another way to find 30° of retroversion is to have the most lateral point on the stem position in line with point D which is 8-10 mm retroversion from the bicipital groove. Also, a recess is preferably reamed into shaft  17  of humerus  12  such that a humeral stem component can be implanted therein. 
         [0032]    One method of making patient-specific cutting guide  50  for guiding a surgical instrument for resecting a portion of humerus  12 , includes first obtaining image data associated with at least a portion of humerus  12  and generating a model of humerus  12  from the image data. Guide  50  preferably includes a base portion  52  including a contact surface shaped to substantially match an outer surface of a neck portion  13  of humerus  12 , at least one proximal stabilization member  54  extending medially from base portion  52  and having a contact surface  56  shaped to substantially match an outer surface  11  of a head portion  14  of humerus  12 , and at least one distal stabilization member  53  includes a contact surface shaped to substantially match an outer surface of a shaft portion  17  of humerus  12 . The method further includes providing the guide  50  with a guide slot  68  for directing movement of the surgical instrument, wherein creating the contact surfaces of base portion  52 , at least one proximal stabilization member  54 , and at least one distal stabilization member  53  includes shaping the contact surfaces based on the model of the humerus  12  generated from the image data. 
         [0033]      FIGS. 6-8  show patient-specific cutting guide  60  for guiding a surgical instrument  80  for resecting a portion of glenoid  20  of a patient. Guide  60  includes a base portion  61  having a contact surface  78  shaped to substantially match at least a portion of a cavity  21  of glenoid  20 . Base portion  61  includes a guide hole  70  extending therethrough. Guide hole  70  has an axis  90  coaxial with an axis of rotation. Guide pin  80  engages bone of cavity  21  after passing through guide hole  70  of base portion  61 . Placement of guide pin  80  may be aided by surgical instrument  82  having a cannula  84 . Guide hole  70  is preferably aligned with the centerline of the spine of the scapula such that guide pin  80  has the correct location and orientation once engaged to bone in cavity  21 . Once guide pin  80  is correctly positioned, surgical instrument  82  and guide  60  are removed and guide pin  80  can be used to guide drilling of a guide recess (not shown) in cavity  21  used to accept a central screw or peg  48  protruding outwardly from a glenoid component  46  as shown in  FIG. 9 . 
         [0034]    Guide  60  preferably includes stabilization members  62 ,  64 ,  66  extending outwardly from base portion  61  and having a contact surface shaped to substantially match an outer surface of a portion of a scapula  22  of the patient. Stabilization member  62  is preferably located right of the acromial process  74  and left of the coracoid process  72  and stabilization member  64  is preferably located right of the coracoid process  72  when guide  60  is correctly positioned in the cavity of the glenoid. 
         [0035]    Contact surface  78  of base portion  61  preferably includes at least one shaped protrusion (not shown) configured to contact a unique anatomical feature in cavity  21  of glenoid  20  of the patient. In use, guide  60  can be rotated within cavity  21  of glenoid  20  until the at least one shaped protrusion on contact surface  78  of base portion  61  keys into the unique anatomical feature in cavity  21  of glenoid  20 . 
         [0036]    One method of making patient-specific cutting guide  60  for guiding pin  80  used in guiding the resection of a portion of glenoid  20  includes obtaining image data associated with at least a portion of glenoid  20  and generating a model of glenoid  20  from the image data. Guide  60  preferably includes a base portion  61  with a contact surface  78  shaped to substantially match at least a portion of the glenoid cavity  21 , the base portion  61  having a guide hole  70  extending therethrough, the guide hole  70  having an axis  90  coaxial with an axis of rotation. Guide  60  preferably further includes stabilization members  62 ,  64 ,  66  extending outwardly from base portion  61  each having a contact surface shaped to substantially match an outer surface of a portion of scapula  22 . Contact surface  78  of base portion  61  and the contact surfaces of stabilization members  62 ,  64 ,  66  are created by shaping the contact surfaces based on the model of glenoid  20  generated from the image data. 
         [0037]    After humerus  12  and glenoid  20  are resected, an example of a total shoulder arthroplasty prosthesis  100 , as shown in  FIG. 9 , may be implanted. Humeral stem component  40  is preferably implanted into shaft  17  of humerus  12  with a bottom surface of flange  42  thereof lying adjacent flat resected surface  32  substantially co-axial with resection line  30 . Glenoid component  46  is implanted into cavity  21  of glenoid  20  with central screw or peg  48  passing through an aperture in component  46  and into a guide recess created by the surgical instrument  80  being guided through guide hole  70  of guide  60 . 
         [0038]    Although the invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.