Patent Publication Number: US-2004049285-A1

Title: Duo-fixation prosthetic joints

Description:
[0001] This application claims the benefit of U.S. Provisional Application No. 60/409,262, filed on Sep. 9, 2002, by Brian Haas and entitled “Duo-Fixation Prosthetic Joints,” which is incorporated by reference herein in its entirety. 
    
    
     
       BACKGROUND OF THE INVENTION  
       [0002] The present invention relates generally to prosthetic joints and, more particularly, to prosthetic knee joints. The prosthetic joint components of the present invention can be fixed to the patient&#39;s bone by different methods.  
       [0003] The knee joint basically consists of the bone interface of the distal end of the femur and the proximal end of the tibia. Appearing to cover or at least partially protect this interface is the patella which is a sesamoid bone within the tendon of the long muscle (quadriceps) on the front of the thigh. This tendon inserts into the tibial tuberosity and the posterior surface of the patella is smooth and glides over the femur.  
       [0004] The femur is configured with two knob like processes (the medial condyle and the lateral condyle) which are substantially smooth and articulate with the medial plateau and the lateral plateau of the tibia, respectively. The plateaus of the tibia are substantially smooth and slightly cupped thereby providing a slight receptacle for receipt of the femoral condyles.  
       [0005] When the knee joint is injured whether as a result of an accident or illness, a prosthetic replacement of the damaged joint may be necessary to relieve pain and to restore normal use to the joint. Typically the entire knee joint is replaced by means of a surgical procedure which involves removal of the ends of the corresponding damaged bones and replacement of these ends with prosthetic implants. This replacement of a native joint with a prosthetic joint is referred to as a primary total-knee arthroplasty.  
       [0006] On occasion, the primary knee prostheses fails. Failure can result from many causes, including wear, aseptic loosening, osteolysis, ligamentous instability, arthrofibrosis and patellofemoral complications. When the failure is debilitating, revision knee surgery may be necessary. In a revision, the primary knee prosthesis is removed and replaced with components of a revision prosthetic knee system.  
       [0007] In knee surgery or arthroplasty, the prosthetic components can typically be fixed to the patient&#39;s bone in different ways. In one type of prosthetic joint system, the components may include a sleeve that initially has an interference fit with the patient&#39;s bone, and in which bony ingrowth helps to secure the implant and the bone together. Components for this type of fixation typically have a series of stepped outer surfaces, tapering from one end to an opposite end, as disclosed in U.S. Pat. Nos. 4,790,852 and 4,846,839, the complete disclosures of which are incorporated by reference herein. In these systems, the stepped outer surfaces are provided on a sleeve that fits over a stem of a separate prosthetic component. The stem of these separate components has a smooth outer surface, and the inner surface of the sleeve that slides over this outer stem surface is also smooth. Generally, the outer surface of the stem is highly polished, with a typical surface roughness of 4 Ra or better as determined by ANSI/ASME B46.1-1995. The outer surface of the sleeve is typically rough for use in both cemented fixation or to allow for bony ingrowth. This system has been used in both prosthetic hip and knee joints.  
       [0008] Another type of prosthetic system does not use such tapered, stepped sleeves. Such systems typically have components with stems that fit into a prepared cavity or the intramedullary canal of the patient&#39;s bone. The stems and other surfaces of the prosthesis that may contact bone are typically rough, either for fixation of the surfaces to bone cement that holds the implant to the bone or for bony ingrowth.  
       [0009] Due in part to the fact that the size, shape and anatomy of virtually every patient is different, an extensive number of a variety of components have been made available to the orthopedic surgeon in the typical surgical kit. For example, a typical surgical kit for knee arthroplasty will include femoral and tibial components of different configurations to accommodate variations in patient anatomy. In addition, if the surgeon desired to chose between different types of prosthetics intraoperatively, it was necessary for complete surgical sets of the different types of systems to be available to the surgeon. To provide the surgeon with these alternatives would require that a large inventory be on hand and available to the surgeon.  
       SUMMARY OF THE INVENTION  
       [0010] The present invention addresses the need to provide the surgeon with greater options to select the optimal prosthetic joint intraoperatively.  
       [0011] In one aspect, the present invention addresses this need by providing a prosthetic implant surgical kit for use in joint arthroplasty. The kit comprises a plurality of orthopaedic implants and a plurality of sleeves. Each orthopaedic implant has a stem for receipt in a bone. All stems of all the orthropaedic implants have a rough outer surface. The sleeves each have outer surfaces and inner channels for mounting the sleeves on the stems of the implants.  
       [0012] In another aspect, the present invention addresses this need by providing an orthopaedic implant assembly comprising an orthopaedic component having a stem with a distal end, a proximal end and a rough outer surface between the distal end and the proximal end. The assembly also includes a sleeve mounted on the stem of the orthopaedic component. The sleeve has a smooth surface juxtaposed with the rough outer surface of the stem.  
       [0013] In another aspect, the present invention addresses this need by providing an orthopaedic assembly comprising a sleeve having an outer surface and an inner surface. The inner surface of the sleeve defines a smooth frusto-conical channel. The assembly also includes an orthopaedic component with a stem received in the smooth channel of the sleeve. The stem of the orthopaedic component has a rough outer surface.  
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0014] In the following drawings like reference numbers are used for like parts.  
     [0015]FIG. 1 is perspective view of a tibial component of a prosthetic knee system incorporating the principles of the present invention;  
     [0016]FIG. 2 is a front elevation of a tibial sleeve to be used with the tibial component of FIG. 1;  
     [0017]FIG. 3 is a side elevation of the tibial sleeve of FIG. 2;  
     [0018]FIG. 4 is a top plan view of the tibial sleeve of FIGS.  2 - 3 ;  
     [0019]FIG. 5 is a cross-section of the tibial sleeve of FIGS.  2 - 4 , taken along line taken along line  5 - 5  of FIG. 3;  
     [0020]FIG. 6 is a front elevation of an assembly of the tibial component of FIG. 1 with the tibial sleeve of FIGS.  2 - 5 ;  
     [0021]FIG. 7 is a cross-section of the tibial sleeve of FIG. 6, showing the tibial stem of the tibial component in full and received within the tibial sleeve;  
     [0022]FIG. 8 is a side elevation of a femoral component to be used with the tibial component of FIG. 1 or with the assembly of FIG. 6;  
     [0023]FIG. 9 is a perspective view of a femoral sleeve for optional use with the femoral component of FIG. 8 with an end cap at its proximal end;  
     [0024]FIG. 10 is a side elevation of the femoral sleeve of FIG. 9;  
     [0025]FIG. 11 is a cross-section of the femoral sleeve of FIGS.  9 - 10 , taken along line  11 - 11  of FIG. 10;  
     [0026]FIG. 12 is a side elevation of an assembly of the femoral component of FIG. 8 with the femoral sleeve of FIGS.  9 - 10  for use with the tibial component of FIG. 1 or with the tibial assembly of FIGS.  6 - 7 ; and  
     [0027]FIG. 13 is a cross-section of the femoral sleeve of FIG. 11, showing the femoral stem of the femoral component in full and received within the femoral sleeve. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0028] A prosthetic joint system  10  incorporating the principles of the present invention is illustrated in FIGS.  1 - 12 . The prosthetic joint system is a modular one, including a tibial component  12 , a femoral component  14 , a tibial bearing insert (not shown), a tibial sleeve  16  and a femoral sleeve  18 . It should be understood that a typical surgical kit for the prosthetic joint system  10  will probably include multiple sizes of each of these components so that the surgeon can select the most appropriate size components for each patient.  
     [0029] As shown in FIG. 1, the tibial component  12  comprises a tibial tray  20  with an integral stem  22  and integral keels  24 . The tibial stem  22  in the illustrated embodiment has a rough outer surface  26  from its proximal end  28  at the juncture with the tibial tray  20  to its distal end  30 . The distal surface  32  of the tibial tray  20  fits against the proximal surface of the resected tibia or against an augment when implanted, and may also have a rough surface. The tibial stem  22  is received in the cancellous bone of the proximal tibia, and extends into the intramedullary canal of the tibia. The distal end  30  of the tibial stem may be connected to a stem extension (not shown) that is received in the tibial intramedullary canal or to an end cap  34  shown in FIG. 1. The tibial stem  22  may be hollow to receive a portion of the tibial insert bearing, and the proximal surface  36  of the tibial tray  20  supports the insert bearing. The proximal surface  36  of the tibial tray  20  is smooth.  
     [0030] The femoral component  14  includes outer condylar portions  40  that bear against the tibial insert bearing in use. As shown in FIG. 8, the femoral component  14  also includes an integral femoral stem  42  and inner surfaces  44  that will bear against a resected surface of the femur or against an augment (not shown) that is positioned between the femoral component and the resected bone surface. The femoral stem  42  is received in the cancellous bone of the distal femur, and extends into the intramedullary canal of the femur. The femoral stem  42  in the illustrated embodiment has a rough outer surface  46  from its distal end  48  at the juncture with the flat inner surfaces of the femoral component to its proximal end  50 . The proximal end  50  of the femoral stem may be connected to a stem extension (not shown) to be received in the femoral intramedullary canal.  
     [0031] The tibial bearing insert can be a standard commercially available insert, such as is available from DePuy Orthopaedics, Inc. of Warsaw, Ind.  
     [0032] The tibial sleeve  16  and femoral sleeve  18  are commercially available from DePuy Orthopaedics of Warsaw, Ind. They each have stepped or terraced outer surfaces  60  that taper from one end  62  to an opposite end  64 . Each sleeve  16 ,  18  has an inner channel  66  defined by a smooth inner surface  68 . The femoral sleeve  18  is designed to be placed over the femoral stem  42  so that the assembly of the femoral component  14  and femoral sleeve  18  can be implanted in the patient when desired. The tibial sleeve  16  is similarly designed to be placed over the tibial stem  22  so that the assembly of the tibial component  12  and tibial sleeve  16  can be implanted in the patient when desired. The femoral sleeve  18  can be used with an end cap  65 , as shown in FIG. 9.  
     [0033] The tibial component and tibial sleeve may have features as described in the following U.S. provisional patent applications filed on Sep. 9, 2002: App. No. 60/409,284, entitled “PROSTHETIC TIBIAL COMPONENT WITH MODULAR SLEEVE” filed by Deborah S. German, Todd D. Dumiak, Danny W. Rumple and Christel M. Klebba (DEP 797); and App. No. 60/409,319, entitled “UNIVERSAL TIBIAL AUGMENT” filed by Deborah S. German and Jeffery L. Koenemann (DEP 798). These applications are incorporated by reference herein in their entireties. The United States patent applications filed concurrently herewith based upon and claiming priority to these provisional patent applications (Ser Nos. ______ and ______) are also incorporated by reference herein in their entireties.  
     [0034] In the prior art, the juxtaposed outer surfaces of the stems and inner surfaces of the sleeves were both smooth to allow for easy assembly of the stems and sleeves. In contrast, in the present invention, the juxtaposed outer surfaces  26 ,  46  of the stems  22 ,  42  and inner surfaces  58  of the channels  66  of the sleeves  16 ,  18  have different finishes. In the assemblies of the present invention, the smooth inner surfaces  58  of the sleeves  16 ,  18  are juxtaposed with the rough outer surfaces  26 ,  46  of the stems  22 ,  42 . These juxtaposed surfaces  26  and  68  and  46  and  48  are illustrated in FIGS. 7 and 13. Advantageously, the surgeon can opt intraoperatively to use the femoral component  14  and tibial component  12 , or one of them, without the associated sleeve  18 ,  16 , and the same femoral component  14  and tibial component  12  can also optionally be implanted as an assembly with a sleeve  18 ,  16  if the surgeon so chooses. The surgeon has these options available in a single surgical kit, without the need to maintain multiple inventories of different types of prosthetic systems.  
     [0035] The femoral and tibial components  14 ,  12  of the prosthetic joints may be made of standard materials for such implants, such as a cast cobalt-chrome or titanium alloy, and can be made in the standard way. The rough surfaces  26 ,  46  on the components  12 ,  14  can be created by blasting the cast surface with a glass bead blast to roughen these surfaces. For example, the surfaces may be blasted with glass beads to produce a roughened surface with an average roughness of at least about 20 Ra microns as determined by ANSI/ASME B46.1-1995. To reduce the possibility of fretting of the rough surface when a sleeve is mounted on the stem, it may be desirable to maintain the surface roughness of the sleeve below 45 Ra microns. Those in the art will appreciate that manufacturing parameters such as glass bead or grit size and the pressure of the blast can be varied to achieve the desired roughness. It should be understood that the roughness of 20-45 Ra microns is provided as an example only; the present invention is not limited to a particular numerical range of roughness unless expressly called for in the claims. Generally, the surface texture of the stem should allow for successful use of the implant with bone cement and should not fret when a sleeve is mounted on the stem. In addition, the invention is not limited to use of glass bead blasting to achieve this roughness. Unless expressly excluded by the claims, the term “rough” should be construed to encompass any treatment of the surface that is appropriate for cemented implantation or for bony ingrowth. The roughening technique should be one that allows the tapered stems to be received in the tapered inner channels  66  of the sleeves  16 ,  18 .  
     [0036] Generally, the inner surfaces  68  of the sleeves  16 ,  18  defining the inner channels  66  are smooth rather than rough, and have surface roughnesses less than that of the outer surfaces  26 ,  46  of the stems. For example, it may be desirable that the inner surfaces  68  be highly polished ( 2 - 4  Ra, for example) to reduce or eliminate fretting when the sleeve is used with the roughened stem.  
     [0037] In use, the surgeon can prepare the proximal end of the tibia and distal end of the femur in the standard manner, and resect these bones in the standard manner to receive the prosthetic components. If the surgeon determines that the patient&#39;s bone, such as the proximal tibia, is sufficiently healthy to receive and hold the implant in a stable position, the surgeon can implant the tibial component  12  alone without a sleeve  16 , and the rough surface  26  of the stem  22  of the tibial component  12  will provide a surface suitable for either bonding with bone cement or for bony ingrowth to occur. If the surgeon determines that the patient&#39;s bone has deteriorated to the point that use of a tibial sleeve  16  is desirable, the surgeon can use the same tibial component  12  and place a tibial sleeve  16  on the stem  22  of the tibial component  12  and implant the assembly of modular components  12 ,  16 . Although the rough surface  26  of the tibial stem  22  would be effective in providing a bond to the surrounding bone or to cement, by providing the system of the present invention, the surgeon&#39;s options are increased without adding to the inventory of prosthetic devices that must be maintained. The surgeon can make the same choices on the femoral side, and can opt to use either the femoral component  14  alone or as an assembly with the femoral sleeve  18 , depending on the surgeon&#39;s assessment during surgery of the optimum system for that patient.  
     [0038] It should be understood that although the invention has been described with regard to the illustrated femoral and tibial components, the principles of the present invention can be applied to other prosthetic joint components as well, such as those used for hip arthroplasty.  
     [0039] Although specific features have been described for the illustrated embodiment of the invention, it should be understood that the invention is not limited to the features or properties described above unless expressly called for in the claims.  
     [0040] In addition, while only a specific embodiment of the invention has been described and shown, it is apparent that various alternatives and modifications can be made thereto. Moreover, those skilled in the art will also recognize that certain additions can be made to these embodiments. It is, therefore, the intention in the appended claims to cover all such alternatives, modifications and additions as may fall within the true scope of the invention.