Abstract:
A modular part-spherical acetabular reamer including a first part-spherical element having an outer surface including a pole and a portion extending from the pole toward an equator of the reamer to a point intermediate the pole and the equator. The reamer also includes a second part-spherical element having an outer surface extending from the intermediate point towards the equator. Further, the reamer includes means for releasably coupling the first and second portions to form the modular part-spherical reamer.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to surgical instruments and, in particular to acetabular reamers.  
         [0002]     An acetabular reamer having a reamer head is used in hip replacement surgery for re-forming the hip socket, or acetabulum, in preparation for implanting a prosthetic component, such as an acetabular cup or socket. To insure a proper fit of the prosthetic device, the deteriorated or diseased bone and cartilage needs to be cut or shaved away to healthy bone tissue so that the reamed acetabulum matches the contours of the prosthetic to be fitted.  
         [0003]     In a typical hip replacement procedure, including an acetabular implant, a surgeon makes an incision in the hip area, displaces the existing hip joint, shapes the acetabulum with the reamer to receive a metallic or plastic prosthetic socket, inserts the prosthetic socket, replaces the ball of the femur with a prosthetic ball, and inserts the prosthetic ball into the prosthetic socket to complete the operation.  
         [0004]     Typically, a reamer head is comprised of a continuous exterior surface that requires a large incision in the skin of the patient in order to place the reamer head adjacent the socket to be reamed. Such a reamer is shown in U.S. Pat. Nos. 5,658,290, 6,106,536 and 6,702,819. Unfortunately, the size of the incision, effects the time that is required for recovery of the operation with a larger size incision increasing the recovery time. In addition, a larger incision also makes the patient more susceptible to infection and increases the time frame that disease may be introduced into the body via the incision.  
       SUMMARY OF THE INVENTION  
       [0005]     The present invention is directed to surgical instruments and implants. In one aspect of the present invention, a rotary surgical reamer assembly for moving bone and tissue from a bone joint include a dome and a body. The dome may include an exterior and an interior as well as a plurality of cutting sites disposed on the exterior and a plurality of apertures adjacent to the cutting sites. The body preferably includes a base, a ridge and at least one column connecting the base to the ridge. In one aspect of the present invention, the dome is attached to the ridge.  
         [0006]     The assembly also preferably includes a circumferential ridge having an exterior and interior, a first edge, a second edge and an opening extending from the first edge to the second edge. The circumferential ring includes a plurality of cutting sites disposed on the exterior and a plurality of apertures adjacent to the cutting sites. The first edge of the circumferential ring is adjacent to the dome and the second edge of the circumferential ring is adjacent to the base of the body. Preferably, the exterior of the dome and the exterior of the circumferential ring form a substantially continuous wall.  
         [0007]     In one aspect of the present invention, the dome and the circumferential ring are part-spherical and in combination form a substantially hemispherical shape. The dome may include a pole further comprising a polar axis passing through the pole. The exterior of the dome and the exterior of the circumferential ring are preferably substantially curvilinear relative to the polar axis.  
         [0008]     In one aspect, the interior of the circumferential ring may include a first portion rectilinear relative to the polar axis such that when the circumferential ring is disposed on the body, the first portion engages the at least one column to thereby prevent rotation of the circumferential ring relative to the body.  
         [0009]     The dome may be remote from the base of the body at a sufficient distance to permit the dome and the body to be placed through an incision concurrently without causing the cutting sites of the dome to engage soft tissue surrounding the incision, as compared to when the circumferential ring and the body are passed through the incision concurrently where the cutting sites would contact the soft tissue surrounding the incision.  
         [0010]     In one aspect of the present invention, a method of removing bone and soft tissue from a bone joint may include providing a first portion of a surgical reamer. The first portion having a first cutting surface for removing bone and soft tissue. The method also comprising providing a second portion of a surgical reamer that also includes cutting surfaces for removing bone and soft tissue. After making an incision at a portion of a body to allow access to a bone joint, the first portion is placed through the incision and subsequently the second portion is place through the incision and into the vicinity of the bone joint. Once the first portion and second portion are placed within the vicinity of the bone joint, they are assembled together such that the first cutting surface and the second cutting surface form a substantially single cutting surface.  
         [0011]     In one aspect of the present invention, a method of removing bone and soft tissue from a bone joint includes making an incision into the skin of a patient to allow access to a desired location. The incision has dimensions that permit a first portion and a second portion of a reamer to pass through the incision and into the desired location, without a cutting surface of the first portion or second portion coming into contact with the skin surrounding the incision. The method also includes assembling the first portion of the reamer to the second portion of the reamer wherein the resulting assembly has overall dimensions larger than the dimensions of the incision such that if the resulting assembly was passed through the incision, the cutting surface of either the first portion or the second portion would come in contact with the skin surrounding the incision.  
         [0012]     In another aspect of the present invention, an orthopedic implant is provided having a core with an interior surface, an exterior surface, a first end and an apex. The core also includes an engagement element. The implant further includes a ring having an interior surface, an exterior surface, a first edge, a second edge and an opening extending from the first edge to the second edge. The ring also having an engagement element, which corresponds to the engagement element of the core. The opening of the ring being sized to receive the core such that the apex of the core may be passed through the opening until the first end of the core is adjacent to the first end of the ring. When the first end of the core is adjacent to the first end of the ring, the engagement element of the core may be mated with the engagement element of the ring to thereby lock the core to the ring. In one embodiment the orthopedic implant described above is an acetabular shell implant. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  illustrates one embodiment of an acetabular reamer assembly according to the present invention;  
         [0014]      FIG. 2  is a side view of a first component of the acetabular reamer assembly shown in  FIG. 1 ;  
         [0015]      FIG. 3  is a top view of the first component shown in  FIG. 2 ;  
         [0016]      FIG. 4  is a bottom view of the first component shown in  FIG. 2 ;  
         [0017]      FIG. 5  is a side view of second component of the acetabular reamer shown in  FIG. 1 ;  
         [0018]      FIG. 6  is a top view of the second component shown in  FIG. 5 ;  
         [0019]      FIG. 7  illustrates the second component of  FIG. 5  being inserted into a patient;  
         [0020]      FIG. 8  illustrates another aspect of the present invention relating for a two-part first component;  
         [0021]      FIG. 9  illustrates an embodiment of an acetabulum shell according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0022]     The present invention relates to a surgical reamer assembly in the form of an acetabular reamer assembly  10  as shown in  FIG. 1 . An acetabular reamer assembly  10  is generally useful for removing bone and tissue from a joint socket when performing reconstructive surgery, to facilitate the installation of a prosthetic device or to repair the damaged bone.  
         [0023]     In one aspect of the present invention, the acetabular reamer assembly  10  preferably includes a first component having a body (not shown in  FIG. 1 ), coupled to a dome  12  and a second component comprising a ring  14 . The dome  12  and the ring  14  in combination define the cutting surface of the acetabular reamer assembly  10 . A handle  16  is attached to the body and preferably extends transversely from the dome  12  as will be described below. The adjustment handle  16  may include a drive shaft  17  having a drive end  19  that is attached to a rotational driver such as a surgical drill (not shown). The surgical drill provides rotational movement to the drive shaft  17 , which in turn causes the dome  12  and the ring  14  to rotate. Such surgical drills are known to those in the art as for example surgical drills included in U.S. Patent Publication Nos. 2004/0087958, 2004/0153080, and 2005/0216022, the disclosures of which are hereby incorporated by reference herein.  
         [0024]     With reference to  FIGS. 2-4 , various aspects of the dome  12  will now be described. The dome  12  is preferably formed from stainless steel and includes an exterior surface  20  and an interior surface  22 . A plurality of cutting sites  24  is disposed along the exterior surface  20  of the dome  12 . The cutting sites  24  may comprise a plurality of cupped cutters distributed along the exterior surface  20  and oriented to face a rotational cutting direction, as known in the art. An aperture  26 , extending from the exterior surface  20  to the interior surface  22  may be positioned next to each cutting site  24 . The apertures  26  enable any material cut by the cutting sites  24  to pass from the exterior surface  20  of the dome  12  through the aperture and into a void below the dome. The cutting sites  24  preferably have sharp edges that extend beyond the exterior surface  20  of the dome  12 . The cutting sites  24  may be thought of as a plurality of grating holes, having a raised sharpened edge on one side of the hole facing the cutting direction for cutting and removal of bone in the acetabular region.  
         [0025]     The dome  12  preferably has an arcuate shape similar to a portion of a sphere that includes an apex of the sphere. Thus, as shown in  FIG. 2 , the dome  12  has an apex  21  and a bottom ridge  23  opposite the apex. A polar axis  30  passes through the apex of the dome  12  and a center of the dome. The arcuate dome  12  extends outwardly in a direction towards the equator of the sphere from the apex  21 . The dome has a maximum diameter L extending from a first point along the bottom ridge  23  to a second point along the ridge, the first point being 180° away from the second point along the bottom ridge but on the opposite side (180° along the circumference). In the preferred embodiment the spherical dome extends about 30° latitude with respect to an equator at approximately 90° from the apex  21 .  
         [0026]     The dome  12  may be permanently or temporarily affixed to the main frame body  13 . In one aspect of the present invention, the main frame body  13  includes a base  42 , a ridge  44 , remote from the base, and a plurality of connecting walls such as columns  46  extending from the base to the ridge. As shown in  FIG. 3 , the preferred base  42  is generally circular and similarly, as shown in  FIGS. 3 and 4 , the ridge  44  is also circular. Both the base  42  and the ridge  44 , preferably extend about axis  30 , which also passes through a center of body  13 , such that base  42  and ridge  44  are concentric with one another. The ridge  44  preferably has a maximum diameter that is substantially equal to the maximum diameter L of the dome  12 . However, the base  42  has a maximum diameter L′ that is greater than the maximum diameter L of the dome  12 . The lengths all being measured from a first point along a circumference of the particular element to a second point along the circumference but 180° away from the first point.  
         [0027]     Also as shown in  FIG. 4 , a cross-bar system  45  is provided within an internal void  47  of the body  13 . The cross-bar system  45  includes a first bar  50  and a second bar  52 , which enable the handle  16  to be attached to the body  13 . As shown in the figure, the first bar  50  extends from a point along the edge of the ridge  44  through the center of the device, as defined by axis  30  to an opposite edge of the ridge. The second bar  52 , similarly extends from one edge of the ridge  44  to an opposite edge of the ridge and also passes through the center. Thus, the first bar  50  and the second bar  52  are preferably perpendicular to one another.  
         [0028]     Another aspect of the present invention is ring  14 , shown in  FIGS. 5 and 6 . Similar to dome  12 , ring  14  includes an interior surface  60 , exterior surface  62  and is formed from stainless steel. Also similar to dome surface  12 , ring  14  includes a plurality of cutting sites  24 A disposed along its exterior surface  62  and a plurality of apertures  26 A positioned adjacent the cutting sites. The apertures  26 A extend from the exterior surface  62  to the interior surface  60  of the ring and allow material cut by the cutting sites  26 A to pass from the exterior surface  62  of the ring to a void within the center of the ring. The ring  14  is preferably arcuate and concaved relative to axis  30  at least along its exterior surface  62 . The ring  14  also includes a first circular edge  64  having a first diameter D and a second circular edge  66  having a second diameter D′ remote from the first circular edge. The edges  64  and  66  define the boundaries of ring  14 . In a preferred embodiment, the maximum diameter L of the ridge  44  of the body has a dimension that is slightly less the dimension of the first diameter D of the first circular edge  64 . And the maximum diameter of the base  42  has a dimension that is slightly larger than the dimension of the second diameter D′ of the second circular edge  66 . The first circular edge  64  and the second circular edge  66  are preferably parallel to one another with the outer surface of the ring being part-spherical.  
         [0029]     The ring  14  is situated about axis  30  and includes an opening  70  extending from the first edge  64  to the second circular edge  66 . In one preferred embodiment, the opening  70  has a larger diameter adjacent to second circular edge  66  than its diameter adjacent to first circular edge  64 .  
         [0030]     As shown in  FIG. 5  in shadow, the interior surface  60  of the ring  14  preferably includes at least one wall  71  that is perpendicular to first circular edge  64  or at least rectilinear to the edge. When the dome  12  and particularly the body  13  are assembled to the ring  14 , the wall  71  interacts with at least one column  46  to thereby prevent the ring  14  from rotating about the body, as will be described below.  
         [0031]     In a method of assembling the acetabular reamer assembly  10 , the dome  12  is attached to the body  13 , either integrally or modularly such as being held on by screws or a taper lock. The dome  12  may also be snap-fitted to the body  13  or each element may have a structure that corresponds to the other structure, which permits engagement between the two elements but does not permit rotation between the two. The ring  14  is placed over the dome  12  with the apex  21  of the dome being received within the opening  70  of the ring adjacent to second circular edge  66 . The dome  12  and body  13  are continually translated through the opening  70  until the entire dome  12  extends outwardly past opening  70  adjacent first circular edge  64 . With the dome  12  positioned atop of the first circular edge  64  of the ring  14 , most of the body  13  is retained within opening  70  of ring  14 . But the ridge  44  of the body  13  is adjacent the first circular edge  64  of the ring  14  and the second circular edge  66  of the ring  14  is adjacent base  42  of the body. Since the base  42  has a larger maximum diameter L′ than the length of the second diameter D′, the body  13  can not pass entirely though the opening  70 . When assembled together, the dome  12  and ring  14  form a hemispherical body having a plurality of cutting sites  24  and  24 A and a plurality of apertures  26  and  26 A extending about their respective exterior surfaces, as shown in  FIG. 1 . The second circular edge  66  is approximately equivalent to an equator of a sphere.  
         [0032]     In this configuration, the acetabular reamer assembly  10  is ready to be employed to ream out an acetabulum such that an acetabular shell may be positioned correctly during reconstructive surgery.  
         [0033]     In order to prevent the ring  14  from being able to rotate about the body  13  when the acetabular reamer assembly is employed and more specifically when a force causes the ring  14  and the dome  12  to rotate about axis  30 , an engaging mechanism may be provided as alluded to before. For instance, when assembling the ring  14  and the dome  12  together, the wall  71  of the ring  14  may be aligned with one of the columns  46  such that these two linear elements confront each other. Since the wall  71  and the column  46  are parallel or at least rectilinear to axis  30 , and are proximate one another when the acetabular reamer assembly is assembled, once coupled together, they do not permit the ring  14  to rotate about the body  13  of the acetabular reamer assembly  10 . Therefore, when the acetabular reamer assembly  10  is employed and a rotational force is applied to the body  13  via a surgical rotary hand piece, the ring  14 , and dome  12  also rotate simultaneously. The engagement mechanism prevents unwanted motion of the ring  14  relative to the body  13 .  
         [0034]     In a method of use, the ring  14  and dome  12  are placed through an incision in the skin of a patient separately. After a surgeon determines an incision location on the patient, he next slices the skin to create the incision I, as shown in  FIG. 7 . The ring  14  is then placed sideways through the incision. A sideways orientation of the ring  14  refers to an orientation wherein the plane of the first edge  64  and the plane of the second edge  66  are more parallel to the longitudinal direction of the incision I, than they are perpendicular, as shown in  FIG. 7 . Once the ring  14  has been positioned in-situ, the ring is rotated such that the opening  70  and more specifically the second circular edge  66  of the ring faces the incision opening. Since the ring  14 , when orientated sideways, has a relatively narrow width, the size of the incision may be smaller than usually required to insert an integral cutting surface of a conventional acetabular reamer.  
         [0035]     Next, the dome  12  and body  13 , which are already assembled together, are translated through the incision I. As with the ring  14 , during introduction through the incision I the plane of the base of the dome/body are oriented sideways with a plane that is tangential to the apex  21  of the dome and the base  42  of the body being more parallel to the longitudinal direction of the incision I, than they are perpendicular. When translating the dome/body  12 , 13  through the incision the base  42  may be used to pry the walls of the incision I apart in order to enlarge the incision opening. Since the skin is generally flexible, this can be accomplished without any further tearing of the skin. Once again, because the dome/body  12 ,  13  only has cutting sites  24  along one portion of the combination component, i.e., dome  12  and body  13 , and more specifically does not have cutting sites proximate the base  42  of the body, the size of the incision required to place the dome/body component in-situ is smaller than the size of an incision required to place a reamer having a continuous hemispherical cutting surface. This prevents the cutters from damaging the soft tissue.  
         [0036]     Thus, since the acetabular reamer assembly  10  is positioned within the body in two stages, and specifically the cutting sites  24 ,  24 A are separately inserted, the incision I may by smaller than required for conventional hemispherical reamers. This is because conventional hemispherical reamers include a continuous exterior surface with cutting sites. As the conventional reamer is inserted through an incision, the incision must be sufficiently wide to prevent the skin from being cut by the cutting sites. This is particularly problematic where a cross section of the reamer is at its largest diameter such as at a position nearest the base of the reamer. This is because as the reamer is inserted sideways, the incision must be long enough to receive the maximum diameter of the reamer but also wide enough to receive the width of the reamer. Thereby requiring a relatively large incision.  
         [0037]     The present invention avoids this by dissecting the cutting sites  24 ,  24 A into two distinct halves, the dome  12  and the ring  14 . When oriented sideways, the ring  14  may have a maximum diameter that is equal to the diameter of a conventional hemispherical reamer also oriented sideways but the width of the ring is less. The combination of the dome  12  and body  13 , when oriented sideways, has a width equal to the width of a conventional reamer but a maximum diameter that is less. And since the combination of the dome  12  and body  13  does not include cutting sites positioned proximate the end of the body that is remote from the dome, to insert the dome/body  12 , 13 , the base  42  of the body maybe placed against the skin positioned adjacent a longitudinal side of the incision I. The body may then be used to pry open the flexible skin such that the dome/body  12 , 13  may be inserted therethrough. Because all of the cutting sites  24  are proximate only the ends of only one side of the incision, the likelihood that the cutting sites may contact the skin is reduced. Plus the requirement of greatly stretching the skin or having a larger incision is eliminated, as compared to an incision required for conventional hemispherical reamers. This configuration enables the dome/body  12 ,  13  to be received through an incision while minimizing the risk that a cutting site will tear the skin around an incision.  
         [0038]     Once the dome/body  12 ,  13  are placed in-situ, they are rotated such that the apex  21  of the dome is aligned with the opening  70  of the ring  14 . Also, if an engagement member is provided such as discussed above, it may be correctly aligned. For instance, a column  46  of the body may be aligned with the wall  71  of the ring  14 . The dome/body  12 ,  13  is translated through the opening  70  until the entire dome  12  extends outwardly from the opening with the bottom ridge  23  of the dome positioned adjacent the first circular edge  64  of the ring. The wall  71  and column  46  may not only prevent unwanted movement between the ring  14  and body  12  but may also provide a key-way system, that only permits the components to be coupled together in a specific spatial relationship. In other words, the ring  14  and body  13  can not be coupled together unless the wall  71  and a column  46  are aligned.  
         [0039]     Once the elements are assembled together and the handle  16  is coupled to the cross-bar system (the handle is preferably coupled to the body during insertion of the dome and the body), a rotary power device may be connected to the handle so as to provide rotational movement to the handle  16  and subsequently to the dome  12  and ring  14 .  
         [0040]     As the dome  12  and ring  14  rotate about axis  30 , the cutting sites  24 ,  24 A are brought into proximity of the bone and soft tissue to be reamed to thereby begin the process of creating a cavity in the bone.  
         [0041]     In another aspect of the present invention, as already alluded to, the dome  12  may be coupled to the body  13  in a removable manner. Thus, as shown in  FIG. 8 , the dome  12  is shown disassembled from the body  13 . To fit the two elements together, the bottom ridge  23  of the dome may be removably attached or permanently attached to ridge  44  of the body  13  such as by snap fitting, welding, using various catch-mechanisms known to those in the art or the like.  
         [0042]     Although the present invention has been described in conjunction with an acetubular reamer assembly, the concept of the invention may also be adapted for other purposes. For instance, an acetabulum implant shell  110  may be dissected in half to form a core  112  and a ring  114 , as shown in  FIG. 9 . The core includes an interior surface  116 , an exterior surface  118 , an apex  117  and a circular edge  119 . Similarly, the ring  114  includes an interior surface  120 , an exterior surface  122  and an opening  124  extending from a first circular edge  126  of the ring to a second circular edge  128 . As with the acetabular reamer assembly  10 , the components of the acetabulum shell implant  110  may be inserted in a two-step process. This reduces the size of the incision required for inserting the shell, as compared to unitary shells.  
         [0043]     In one method, after the acetabulum has been reamed, the ring  114  is inserted through an incision and placed adjacent the acetabulum. Next, the core  12  is inserted through the incision and subsequently through the opening  124  of the ring  114 . The core  112  is translated entirely through the opening  124  until the circular edge  119  of the core  112  is adjacent the first circular edge  126  of the ring  114 . In addition, the exterior surface  118  of the core  112  is positioned adjacent the acetabulum. Preferably, the interior surfaces,  116 ,  124  of the core  112  and ring  114  form a substantially smooth and continuous surface such that a prosthesis placed adjacent the interior surfaces can angulate and rotate smoothly against the surfaces.  
         [0044]     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.