Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims the benefit of priority to U.S. Provisional Patent Application No. 62/183,393 filed 23 Jun. 2015, the contents of which are incorporated herein by reference in its entirety. 
     
    
     FIELD 
       [0002]    The present document relates to the field of arthroplasty—the surgical replacement of part of all of one or more joints of the human skeleton with implanted prosthetic replacements. 
       BACKGROUND 
       [0003]    In the most common knee arthroplasty surgeries, the proximal end of the tibia and distal end of the femur are removed and replaced with metal and/or polymer prosthetics. 
         [0004]    Long bones, including both the tibia and femur, include cortical bone and trabecular or cancellous bone. Cancellous bone is spongelike as it typically has form resembling a mesh, and is found primarily near ends of the bone, where its open-celled mesh supports cortical bone of the bearing surface at each joint. The mesh of cancellous bone is not empty, it is typically filled with soft tissue such as fat and marrow. Cortical bone is denser and more solid than cancellous bone, and not only forms a surface over cancellous bone but typically forms much of the long shaft portion of each long bone, as well as tendon and ligament attachment points and the bearing surfaces (articular surfaces) of each joint; typically the cortical bone bearing surfaces of the bones at each joint are separated by articular cartilage padding and lubricated with synovial fluid. 
         [0005]    During arthroplasty of a joint involving long bones, some or all articular cartilage remaining in the joint is removed—indeed many arthroplasties are performed because of joint pain arising because the articular cartilage has been destroyed by injury or arthritis. Bone at the bearing surface of one or more bones of the joint is then trimmed back to make room for, and to fit onto, an implant that will functionally replace the bearing surface of that one or more bones. In the process of trimming back the bone, much cortical bone of the bearing surface, and some adjacent cortical bone, is removed, leaving residual bone, much residual bone at trimmed surfaces is newly exposed cancellous bone. Once bone trimming is completed, bone cement is used to attach the implant to the remaining bone, including to cancellous bone, of the long bone. The most common bone cement used in 2015 is based on polymethyl methacrylate (PMMA) with radiopaque filler and other additives. 
         [0006]    In a total knee-replacement arthroplasty, implants cemented to that part of each bone remaining after bones are trimmed replace the articular surfaces of both femur and tibia, and in many such surgeries the articular surface of the patella. 
         [0007]    A typical prior-art total knee replacement arthroplasty may use implants as illustrated schematically in  FIG. 1A  as assembled into a patient, and in  FIG. 1B  as an exploded diagram showing each individual implant. A first implant  102 , or femoral component, is formed with a socket  104  that attaches to residual bone of femur  105 . A second implant  106 , or tibial component, is formed with a stabilizing protrusion  108  that is configured to extend distally from the joint into a slot trimmed into residual tibia  110 . A plastic insert  112  disposed between the first  102  and second  104  implants serves to pad and lubricate the joint and keep the first and second implants from abrading each other. A third implant  114 , or patellar component, may in some cases be affixed to the underside of the patella (not shown), where it slides on first implant  102  as the knee bends. 
       SUMMARY 
       [0008]    In an embodiment, a method of attaching a prosthetic implant to a tibia includes trimming away an articular surface of the tibia, leaving a trimmed surface. Holes are punched into the surface by placing a punch-plate with sharpened punches on the trimmed surface, and striking the punch plate to drive the punches into the trimmed surface. The punch plate is removed and polymethyl methacrylate bone cement is used to attach the trimmed surface to a prosthetic implant. 
         [0009]    In another embodiment, a method of attaching a prosthetic implant to a tibia includes using a drilling template having a plurality of predrilled guidance holes placed on the trimmed surface of the tibia, and a hand drill to drill holes of predetermined depth through the guidance holes of the template. 
         [0010]    In another embodiment, a method of attaching a prosthetic implant to a tibia includes trimming away an articular surface of the tibia, leaving a trimmed surface; positioning a robotic drilling system over the trimmed surface of the tibia; adjusting a drilling pattern of the robotic drilling system according to the trimmed surface of the tibia; using the robotic drilling system to drill holes of predetermined depth according to the drilling pattern into the trimmed surface of the tibia; and using a polymethyl methacrylate bone cement to attach the trimmed surface to a prosthetic implant. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0011]      FIGS. 1A and 1B  illustrate a PRIOR-ART total knee replacement as known in the art. 
           [0012]      FIG. 2  illustrates an perforator tool. 
           [0013]      FIG. 3A  illustrates a side view of an improved perforator tool tailored for use in knee arthroplasty. 
           [0014]      FIG. 3B  illustrates a bottom view of a removable head of the tool of  FIG. 3A  showing the array of spikes. 
           [0015]      FIG. 3C  is a top view of the removable head of  FIG. 3B  showing the striking plate. 
           [0016]      FIG. 4  is a flowchart of a method for performing arthroplasty that includes using the perforator. 
           [0017]      FIG. 5  is an illustration of an alternative template for perforating trimmed bone of a tibia, utilizing a hand drill. 
           [0018]      FIG. 6  is a flowchart of a method for performing arthroplasty that utilizes a robotic drill. 
           [0019]      FIG. 7  is a sketch of an X-Y programmable robotic drilling apparatus usable in the method of  FIG. 6 . 
           [0020]      FIG. 8  is a flowchart of a knee arthroplasty that includes perforating both the tibia and patella with a punch. 
           [0021]      FIG. 9  is a flowchart of an alternative knee arthroplasty that includes perforating tibia and patella with a drill and drill guide to optimize cement attachment. 
           [0022]      FIG. 10  is a cross sectional schematic drawing showing positioning pin holes and cement-bonding holes in a patella. 
           [0023]      FIG. 11  is a frontal and cross sectional view of a dual-purpose fitting-trial piece and drill guide configured for perforating a trimmed end of a femur during a knee arthroplasty. 
           [0024]      FIG. 12A  is a top view illustration of a perforating punch or drill guide adapted for hip arthroplasty. 
           [0025]      FIG. 12B  is an illustration of a drill guide adapted for hip arthroplasty. 
           [0026]      FIG. 12C  is an illustration of a perforating punch adapted for hip arthroplasty. 
           [0027]      FIG. 13  is a cross sectional view of a hip arthroplasty performed according to the present invention. 
           [0028]      FIG. 14A  is a top view illustration of a perforating punch or drill guide adapted for shoulder arthroplasty. 
           [0029]      FIG. 14B  is an illustration of a drill guide adapted for shoulder arthroplasty. 
           [0030]      FIG. 14C  is an illustration of a perforating punch adapted for shoulder arthroplasty. 
           [0031]      FIG. 15  is a perspective view of a shoulder arthroplasty performed according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0032]    It is desirable that each implant of an arthroplasty, including a total knee arthroplasty (TKA), remain well attached to the bone whose articular surface it replaces and to which it was attached during surgery. Whenever an implant becomes loosened from the bone, remaining bone may degrade through osteolysis, and the patient may suffer pain and instability that interfere with mobility; it may become necessary to remove and replace the implant to restore patient mobility. Removal and replacement of implants is both an expensive and painful process that medical insurers, surgeons, and patients prefer to avoid. 
         [0033]    It has been proposed that forming perforations in surfaces of trimmed residual bone, including particularly dense or sclerotic bone, adjacent to the implants, such as implants  102 ,  106 ,  114 , will allow better attachment of bone cement to bone, and thereby decrease chances of implants becoming loosened from the residual bone. Some surgeons drill holes into the cut tibial surface in an effort to achieve better attachment of bone to implant, however hole patterns and spacing vary widely and effectiveness is unproven, particularly where some or all cortical bone has become extra-dense sclerotic bone. Sclerotic bone is known to interdigitate less effectively to existing bone cements than normal cortical bone, and is therefore more prone to failure with prior techniques. 
         [0034]    We have experimented with perforators that create a predetermined and repeatable array of perforations of predetermined diameter, depth, and spacing. Among these tools are the experimental perforator tool of  FIG. 2  and the improved, customized, tool of  FIG. 3 . 
         [0035]    The tool  150  of  FIG. 2  has a sliding aluminum plate  152  with an array of holes  153  forming a grid pattern. Removable steel punch pins  154 , each having a sharp point, are inserted into some or all of the holes, and sliding plate  152  is then slid into an aluminum frame  156 . Each pin has a maximum diameter of 3 mm and tapers to a point over a pin depth of 4.5 mm. 
         [0036]    A mechanical model of bone is solid rigid polyurethane foam from Sawbones (Pacific Research Laboratories, Vashon, Wash.), as per ASTM Standard F-1839-08 in 40 PCF and 50 PCF foams for properties of a dense bone, such as cortical or sclerotic bone, and 20 PCF or less for cancellous bone. 
       EXPERIMENTS 
       [0037]    Closed cell polyurethane foam of densities 10 PCF, 20 PCF, 30 PCF, and 40 PCF was obtained, and formed into blocks of the same dimensions, dimensions chosen to fit a clamp for placement into a shear-testing machine. These were tested with hole densities selected from zero holes/cm2, 1.0 holes/cm2, 1.5 holes/cm2 and 2.5 holes/cm2, the holes being punched into the foam by pressing the points of pins  154  of the tool of  FIG. 2  into the foam blocks. 
         [0038]    Titanium plates used to mimic the tibial tray of a TKA system had a 2 mm deep recessed square (33 mm×33 mm) to simulate the design of the tibial tray, with surface roughness similar to that found in clinical implants. 
         [0039]    A medium viscosity PMMA bone cement, DePuy SmartSet CMW (DePuy, Warsaw, Ind.) was used for this study in 15 gram portions placed on foam blocks 30 seconds after being mixed for 60 seconds, spread and worked into holes of foam and titanium plate over following 90-180 seconds, and clamped for 45 minutes to cure. Laboratory temperature was maintained between 20 and 22 C. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 peak shear load and failure modes versus foam and hole density 
               
             
          
           
               
                   
                 Foam 
                 Hole 
                 Peak at 
                   
               
               
                 Cement 
                 Density 
                 Density 
                 Failure 
               
               
                 Batch 
                 (PCF) 
                 (holes/cm 2 ) 
                 (kN) 
                 Failure Mode 
               
               
                   
               
             
          
           
               
                  7 (CMW) 
                 20 
                 1.0 
                 3.341 
                 Block fracture 
               
               
                  7 (CMW) 
                 20 
                 1.0 
                 4.067 
                 Block fracture 
               
               
                  7 (CMW) 
                 20 
                 1.0 
                 3.988 
                 Block fracture 
               
               
                  7 (CMW) 
                 20 
                 1.0 
                 3.578 
                 Block fracture 
               
               
                  8 (CMW) 
                 10 
                 0 
                 1.26 
                 Bone-cement failure 
               
               
                  8 (CMW) 
                 10 
                 0 
                 1.929 
                 Bone-cement failure 
               
               
                  8 (CMW) 
                 40 
                 0 
                 2.969 
                 Bone-cement failure 
               
               
                  8 (CMW) 
                 40 
                 0 
                 4.897 
                 Bone-cement failure 
               
               
                  9 (CMW) 
                 10 
                 1.0 
                 1.168 
                 Bone-cement failure 
               
               
                  9 (CMW) 
                 20 
                 0 
                 2.387 
                 Bone-cement failure 
               
               
                  9 (CMW) 
                 30 
                 1.0 
                 4.974 
                 Block fracture 
               
               
                  9 (CMW) 
                 40 
                 1.0 
                 3.587 
                 Plate-cement failure 
               
               
                 10 (CMW) 
                 10 
                 1.0 
                 1.507 
                 Bone-cement failure 
               
               
                 10 (CMW) 
                 20 
                 0 
                 3.851 
                 Block fracture 
               
               
                 10 (CMW) 
                 30 
                 1.0 
                 5.071 
                 Block fracture 
               
               
                 10 (CMW) 
                 30 
                 0 
                 5.895 
                 Block fracture 
               
               
                 11 (CMW) 
                 10 
                 0 
                 0.9785 
                 Bone-cement failure 
               
               
                 11 (CMW) 
                 20 
                 0 
                 3.517 
                 Block fracture 
               
               
                 11 (CMW) 
                 30 
                 0 
                 4.878 
                 Block fracture 
               
               
                 11 (CMW) 
                 40 
                 1.0 
                 4.709 
                 Bone-cement failure 
               
               
                 12 (CMW) 
                 30 
                 0 
                 4.891 
                 Block fracture 
               
               
                 12 (CMW) 
                 30 
                 1.0 
                 5.796 
                 Block fracture 
               
               
                 12 (CMW) 
                 40 
                 0 
                 5.560 
                 Bone-cement failure 
               
               
                 12 (CMW) 
                 40 
                 1.0 
                 5.138 
                 Bone-cement failure 
               
               
                 13 (CMW) 
                 30 
                 2.5 
                 5.195 
                 Block fracture 
               
               
                 13 (CMW) 
                 40 
                 1.5 
                 4.821 
                 Bone-cement failure 
               
               
                 13 (CMW) 
                 40 
                 1.5 
                 4.25 
                 Bone-cement failure 
               
               
                 14 (CMW) 
                 30 
                 2.5 
                 5.549 
                 Block fracture 
               
               
                 14 (CMW) 
                 40 
                 1.5 
                 6.11 
                 Bone-cement failure 
               
               
                 14 (CMW) 
                 40 
                 2.5 
                 6.448 
                 Bone-cement failure 
               
               
                 14 (CMW) 
                 40 
                 2.5 
                 6.556 
                 Block fracture 
               
               
                 15 (CMW) 
                 30 
                 2.5 
                 5.009 
                 Block fracture 
               
               
                 15 (CMW) 
                 40 
                 2.5 
                 5.493 
                 Block fracture 
               
               
                 15 (CMW) 
                 40 
                 2.5 
                 5.385 
                 Block fracture 
               
               
                 16 (CMW) 
                 20 
                 2.5 
                 3.915 
                 Block fracture 
               
               
                 16 (CMW) 
                 20 
                 2.5 
                 4.066 
                 Block fracture 
               
               
                 16 (CMW) 
                 10 
                 2.5 
                 1.705 
                 Bone-cement failure 
               
               
                 16 (CMW) 
                 10 
                 2.5 
                 1.765 
                 Bone-cement failure 
               
               
                 17 (CMW) 
                 20 
                 2.5 
                 2.717 
                 Bone-cement failure 
               
               
                 17 (CMW) 
                 20 
                 2.5 
                 3.009 
                 Block fracture 
               
               
                 17 (CMW) 
                 10 
                 2.5 
                 1.467 
                 Bone-cement failure 
               
               
                 17 (CMW) 
                 10 
                 2.5 
                 1.558 
                 Bone-cement failure 
               
               
                   
               
             
          
         
       
     
         [0040]    It was found that perforation of 1 hole/cm2 was sufficient for foams of less than 30 PCF, but that perforation of 2.5 holes/cm 2  was more appropriate for foams of 40 PCF simulating cortical and sclerotic bone, while not degrading fixation of bone cement to cancellous bone. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Hole Dimensions 
               
             
          
           
               
                 Hole Dimensions 
                 Density/sq cm 
                 Diameter mm 
                 Depth mm 
               
               
                   
               
               
                 A 
                 0.6-6 (&lt;50% area)     
                 1-5 
                 2-5 
               
               
                 B 
                 2-6 (&lt;50% area) 
                 1-2 
                 2-5 
               
               
                 C 
                 1-6 (&lt;50% area) 
                 1-4 
                 2-5 
               
               
                 D 
                 2.5 
                 3 
                 4.5 
               
               
                   
               
             
          
         
       
     
         [0041]    We anticipate that best results may vary somewhat with types of bone found in each particular patient, and that areal hole density will be in the range of 0.5 to 6 holes per square centimeter (Table 2), with hole diameter in the range of 1 to 5 mm, with hole depth 2 to 5 mm. We also anticipate that the hole density used on any particular patient is chosen such that the area of holes drilled in the tibial or other bone surface does not exceed 50% of the tibial surface, so that for hole diameters 1 to 2 mm, hole density is in the range of 2 to 6 per square cm; for hole diameters 2 to 3 mm, hole density is in the range of 1 to 6 per square cm; for hole diameters of 3 to 4 mm, hole density is in the range of 0.5 to 4 per square cm; and for hole diameters 4 to 5 mm, the hole density is in the range of 0.5 to 2.5 per square cm. 
         [0042]    In a particular embodiment, hole density is 2.5/sq. cm, diameter is 3 mm, and depth 4.5 mm. 
       Surgical Tool and Procedure 
       [0043]    It is therefore proposed that a tool as illustrated in  FIGS. 3A, 3B, and 3C  be used during knee arthroplasty surgeries. The tool  200  has a handle  202  fitted with a clamp  204  for attaching a coupling shaft  208  of a removable punch-plate  206 . Removable punch-plate  206  is fabricated in several sizes, and provided in a kit with handle  202 , so that a punch plate of size appropriate for the tibia of a particular patient can be selected and attached to handle  202  for use in a particular arthroplasty. In typical surgeries, the punch-plate selected is just small enough that all points  210  of the tool fit on bone of the trimmed surface of the tibia (not shown). The punch-plate of the tool also has a striking surface  212  adapted to being struck by a mallet. 
         [0044]    During an arthroplasty, the patient is anaesthetized and arthroplasty surgery begins in traditional manner with trimming away  250  ( FIG. 4 ) of the tibial articular surface and any remaining articular cartilage. A punch-plate  206  of appropriate size is then selected  252  such that all punches fit on the residual tibial surface, and attached  254  to handle  202 , the punch plate is positioned on the tibial surface. The striking plate  212  of the punch plate  206  is then struck  256  with a mallet, driving the punch pins  210  into the trimmed tibial surface; punch plate  206  is then removed  258  with tool  200  from the surface. Surgery then continues with mixing and applying  260  of bone cement to both the tibial and prosthetic surfaces, being careful to work cement into holes of the tibia, and pressing the prosthetic implant onto the tibia. 
         [0045]    In an embodiment the punch-plate has a punch density of 2-½ punches per square centimeter, each punch being 3 millimeters in diameter, and length of 4-½ millimeters. 
         [0046]    In a alternative embodiment, as illustrated in  FIG. 5 , several drilling templates  302  having holes  304  are provided in a set of templates, each template being adapted attachment to the handle illustrated in  FIG. 3A , and is used with a handheld drill using a bit with a depth indicating device. In use, after trimming bone of the tibia, the surgeon selects a template of appropriate size from the set of templates, attaches the template to the handle  202 , and an assistant holds the template in position on the tibia while the surgeon uses the hand drill to drill through the template into the tibial surface. In this embodiment, a depth-gauge device may be attached to a bit rotated by the hand drill to limit hole depth to a predetermined depth. 
         [0047]      FIG. 6  is a flowchart of an alternative method for performing arthroplasty that utilizes a robotic drill, the robotic drill may be of the type illustrated in  FIG. 7  or, since polar coordinates are readily mapped to or from rectangular coordinates, may be one based on rotatable joints in articulated arms like the robotic surgical systems available from MAKO Surgical Corp, see below. In this method, after the tibia is trimmed  350 , the surgeon or his assistant positions  352  a robotic drill unit  400  over the tibia  402  and uses a projector  404  of the robotic drill unit to project light  353  indicating locations of a particular programmed hole pattern on the tibia. The surgeon may then resize and relocate  354  the hole pattern so that all programmed hole locations are on the tibial surface; the adjusted hole pattern is projected  356  onto the tibial surface. Once satisfied with the hole pattern, the surgeon activates  358  the robotic drill unit. X  406  and Y  408  positioning servos of the robotic drill unit operate under control of processor  410  positions  360  a drilling head  412  of the drill unit over each hole location of the hole pattern, and the drilling head, which includes a vertical Z-axis servo, then drills a hole of predetermined depth using a drill bit or burr  414 . When all holes are drilled, the robotic drill is shifted  362  out of the surgical field and the cement is mixed  364 . We note that a robotic drill system provides the ability to drill holes of a particular preselected pattern, the pattern having a desired hole density and depth, far more quickly and with far greater precision of hole location and depth than possible with a hand drill even with drilling template  302 . It is anticipated that the robotic drill may be equipped with a suction device to remove bone fragments severed from the tibia by a drill bit of the robotic drilling system. 
         [0048]    Another alternative embodiment utilizes a robotic surgical system such as that offered by MAKO Surgical Corp., a division of Stryker Corporation. With this embodiment, prior to surgery, an X-ray computed tomography (CT) scan is performed to image the tibia. Cuts as necessary for trimming the tibial surface are planned using existing software, and an appropriate pattern of drill holes determined and incorporated into the planned cuts to the tibial surface. The resulting pattern of holes and trimming cuts is incorporated into a three dimensional computer model of the tibia. 
         [0049]    In an embodiment, the Mako robotic surgical system supports its own weight, and the weight of a cutting tool, but the cutting tool is driven into the surface of the tibia by the surgeon. The surgical robotic system, however, resists the surgeon&#39;s movements whenever the surgeon attempts to cut bone beyond the planned cuts, serving effectively as an invisible drilling template. 
         [0050]    In yet another alternative embodiment, the robotic surgical system actively moves the cutting tool to trim the surface of the tibia and drill the planned pattern of drill holes. 
         [0051]    In addition to improving cementation of tibia to a prosthesis, we expect the method of trimming bone, perforating the trimmed surface of bone, and cementing prosthesis to bone will improve cementation of an articular surface prosthesis to a trimmed surface of patella in a total knee arthroplasty. 
         [0052]    In the method  500  of performing an arthroplasty with both patella and tibial implants attached using perforations to improve adhesion of the cement ( FIG. 8 ), the patient is anaesthetized and arthroplasty surgery begins in traditional manner with trimming away  502  ( FIG. 4 ) of the tibial articular surface and any remaining articular cartilage. A punch-plate  206  of appropriate size is then selected  504  such that all punches fit on the residual tibial surface, and locked  506  to handle  202 , the punch plate is positioned on the tibial surface. The striking plate  212  of the punch plate  206  is then struck  508  with a mallet, driving the punch pins  210  into the trimmed tibial surface; punch plate  206  is then removed with tool  200  from the surface. 
         [0053]    The patella is then trimmed  510 , typically leaving a flat trimmed surface and an appropriate-sized punch plate (not shown) is selected  514  and mated  512  with the trimmed surface of the patella. It is then struck  516  with the mallet to perforate the patellar surface. 
         [0054]    Patellar prosthetics typically have a trio of pegs preventing their sliding on the patellar surface, so a drill guide is selected  518 , positioned in a clamping device on the trimmed surface of the patella, and appropriate-sized holes drilled  520  to fit these pegs. 
         [0055]    Surgery then continues with mixing and applying  522  of bone cement to both the tibial and prosthetic surfaces, being careful to work cement into holes of the tibia, and pressing the prosthetic implant onto the tibia; cement is also applied to the patellar and patellar prosthetic surfaces, worked into the holes, and the prosthetic patellar implant is pressed onto the patella such that its pegs fit into the peg holes. 
         [0056]    In an alternative embodiment  550 , as illustrated in  FIG. 9 , using perforations to improve adhesion of the cement, the patient is anaesthetized and arthroplasty surgery begins in traditional manner with trimming away  502  of the tibial articular surface and any remaining articular cartilage. A drill-guide  302  of appropriate size is then selected  554  such that all holes fit on the residual tibial surface, and locked to handle  202 , the drill guide is then positioned on the tibial surface. A portable electric drill equipped with a bit and a depth-limiting device on the bit is then used to drill  556  an array of holes on the tibial surface; the drill guide is then removed  558  from the surface. 
         [0057]    The patella is trimmed  560 , typically leaving a flat trimmed surface and an appropriate-sized drill-guide (not shown) selected  562 , seated in a clamping device  564 , and positioned on the trimmed surface of the patella. This drill guide may have holes of a first diameter to guide drilling perforation holes, and holes of a larger size to guide drilling of peg holes. A portable electric drill equipped with a bit and a depth-limiting device on the bit is then used to drill  566  an array of perforation holes, and another bit and depth-limiting device is used to drill peg holes, on the patellar surface; the drill guide is then removed from the surface. 
         [0058]    Surgery then continues with mixing and applying  570  of bone cement to both the tibial and prosthetic surfaces, being careful to work cement into holes of the tibia, and pressing the prosthetic implant onto the tibia; cement is also applied to the patellar and patellar prosthetic surfaces, worked into the holes, and the prosthetic patellar implant is pressed onto the patella such that its pegs fit into the peg holes. The resulting knee patellar arthroplasty resembles that illustrated in cross section in  FIG. 10 , where patella  600  is located in the patellar tendon  602  between quadriceps group muscles  604  and tibial insertion  606 . Pegs  608  extend from prosthetic substrate  610  into holes in the patella  600 . Cement  612  fills a narrow gap from patella to substrate  610 , with cement extending into perforations  614 , and a plastic bearing surface  616  is provided to interact with femoral and tibial surfaces of the joint. 
         [0059]    The femur at the knee joint is typically not flat. In embodiments, the knee arthroplasty may use a conventional femoral prosthetic, or, for additional security of bonding the prosthetic to the femur, perforations may be drilled with a combination fitting-trial piece/drill guide  650  as illustrated in  FIG. 11  with frontal view on the left and cross sectional view on the right, with some corresponding holes illustrated. With this embodiment, after trimming the femur, and verification that the fitting-trial piece properly mates to the trimmed femoral surface, the fitting-trial piece/drill guide  650  is positioned on the trimmed femur and a portable drill, with appropriately-sized drill bit and depth control device, is used to drill through holes  652 ,  654  of the fitting-trial piece/drill guide  650  to prepare holes at the same depth, diameter, and areal density as previously discussed with reference to the tibia. The fitting-trial piece/drill guide  650  is then removed, cement is mixed and spread on both the trimmed surface of the femur and the prosthetic, and the prosthetic is pressed onto the prepared end of the femur (not shown). 
         [0060]    It is anticipated that, while doing arthroplasty on knees that require implanted portions be cemented to more than one bone, a punch plate may be used to prepare one of the bones for the cement while the drill guide and hand drill may be used to prepare another bone of the same joint for the cement. It is also anticipated that some steps, such as drilling peg holes in the patella and punching perforation holes in the patella, can be done in reverse order to that described above. Similarly, cement may be mixed and applied separately to each bone-prosthetic seam, instead of with multiple seams at once as described with reference to patella and tibia ( 522 ,  FIG. 8 ) above. 
         [0061]    The method of improving cement-to-bone adhesion heretofore described with reference to knee arthroplasty is also applicable to hip and shoulder arthroplasty. 
         [0062]    A hip arthroplasty is performed by first trimming the acetabulum  702  ( FIG. 13 ) to create a cavity into which an acetabular cup prosthetic socket  704  with polymer lining  706  will fit. In embodiments a drill guide  707  ( FIG. 12B ) or perforating punch  709  ( FIG. 12A ) adapted to fit in the cavity has holes  708  ( FIG. 12B ) or spikes  710  ( FIG. 12C ). In embodiments using the drill guide ( 707 ) the drill guide is placed in the cavity and a portable drill is used to prepare the cement holes having similar dimensions and spacing to those previously discussed with reference to the tibia. In embodiments using the perforating punch ( 709 ) the punch is placed in the cavity and whacked with a mallet to prepare the cement holes having similar dimensions and spacing to those previously discussed with reference to the tibia. Cement  712  ( FIG. 13 ) is then applied between prosthetic socket  704  and acetabulum, entering into cement holes  714 . 
         [0063]    The femoral head is removed and femoral shaft is hollowed to fit a shaft of the femoral portion of the prosthetic. Once the shaft is in place, the ball portion of the prosthetic is manipulated into the acetabular cup prosthetic. 
         [0064]    A shoulder arthroplasty is performed by first trimming the glenoid fossa  752  of the scapula  754  ( FIG. 15 ) to create a cavity into which a glenoid prosthetic  755  will fit. In embodiments a drill guide  757  or perforating punch  759  ( FIG. 14A, 14B, 14C ) adapted to fit in the cavity has holes  758  ( FIG. 14B ) or spikes  760  ( FIG. 14C ). In embodiments using the drill guide ( 757 ) the drill guide is placed in the cavity and a portable drill is used to prepare the cement holes having similar dimensions and spacing to those previously discussed with reference to the tibia. In embodiments using the perforating punch ( 759 ) the punch is placed in the cavity and whacked with a mallet to prepare the cement holes having similar dimensions and spacing to those previously discussed with reference to the tibia. Cement is then applied between prosthetic  755  and scapula, entering into cement holes  766 . 
         [0065]    Changes may be made in the above methods and systems without departing from the scope hereof. It should thus be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall therebetween.

Technology Category: a