Source: http://www.google.com/patents/US20020072805?ie=ISO-8859-1&dq=6,219,045
Timestamp: 2014-04-19 23:02:24
Document Index: 231749935

Matched Legal Cases: ['art 6', 'art 7', 'art 6', 'art 7', 'art 6', 'art 6', 'art 6', 'art 4', 'art 7', 'art 7', 'art 7', 'art 6', 'art 6', 'art 6', 'art 6', 'art 7']

Patent US20020072805 - Joint replacement prosthesis - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA joint replacement prosthesis is disclosed. The prosthesis has a conical base and a hemispherical or part hemispherical top providing a hemispherical or part hemispherical replacement bearing surface. The prosthesis is shaped and sized to have a wedge fit in a conical recess formed in the head or neck...http://www.google.com/patents/US20020072805?utm_source=gb-gplus-sharePatent US20020072805 - Joint replacement prosthesisAdvanced Patent SearchPublication numberUS20020072805 A1Publication typeApplicationApplication numberUS 09/867,771Publication dateJun 13, 2002Filing dateMay 29, 2001Priority dateAug 21, 1996Also published asUS20030125810Publication number09867771, 867771, US 2002/0072805 A1, US 2002/072805 A1, US 20020072805 A1, US 20020072805A1, US 2002072805 A1, US 2002072805A1, US-A1-20020072805, US-A1-2002072805, US2002/0072805A1, US2002/072805A1, US20020072805 A1, US20020072805A1, US2002072805 A1, US2002072805A1InventorsIain Anderson, John Sullivan, Timothy WyattOriginal AssigneeSullivan John Martin Patrick, Anderson Iain Alexander, Wyatt Timothy PeterExport CitationBiBTeX, EndNote, RefManReferenced by (9), Classifications (64) External Links: USPTO, USPTO Assignment, EspacenetJoint replacement prosthesisUS 20020072805 A1Abstract A joint replacement prosthesis is disclosed. The prosthesis has a conical base and a hemispherical or part hemispherical top providing a hemispherical or part hemispherical replacement bearing surface. The prosthesis is shaped and sized to have a wedge fit in a conical recess formed in the head or neck of a human femur or humerus without removal of all of the neck of the femur or humerus. Images(7) Claims(9)
DETAILED DESCRIPTION [0037]FIG. 1 shows a typical prior art hip replacement prosthesis. On the femoral side the prosthesis consists of a metal ball 2 on a short metal neck 3, attached to a stem that is inserted into the medullary cavity in the femur 1. Installation of the device requires removal of a large part of the head and neck of the femur and reaming of cancellous bone from the femur. Where the acetabulum is also relined, an acetabular cup 4 typically fabricated from ultra high molecular weight polyethylene (UHMWPE) is fixed in position with a bone screw (see screw 9 in FIG. 2) or is bonded onto the surface of the acetabulum 5 using a methyl-methacrylate or similar cement. Alternative methods as will be known in the art may also be used. [0038]FIG. 2 shows a preferred form two part prosthesis of the invention similarly fitted to a hip joint. Referring also to FIG. 3, the preferred form two part prosthesis comprises a conical base part 6 which is fitted into a conical recess cut in the head of the femur, and a hemispherical top part 7. Where the acetabulum is also relined, the prosthesis bears against an acetabular cup component 8. [0039] The conical base of the prosthesis is a wedge fit into the conical recess cut in the head of the femur which provides maximum resistance to loosening, and the size of the prosthesis is such that only a part of bone material of the head and neck of the femur is removed, and part of the head or at least all or a substantial part of the neck of the femur remains. Because the prosthesis of the invention does not require that all of the neck of the femur be removed, the option of fitting a conventional prosthesis later in the life of the patient remains if necessary. In a two part prosthesis as shown, screws will usually be used to assist in securing the prosthesis-into the conical recess in the head of the femur in addition to the seating of the conical base into the conical recess, but in a prosthesis having a steeper conical base, the use of additional securing screws may not be required, as will be further described. [0040] Referring particularly to FIGS. 3 to 6, the two part prosthesis comprises a conical base part 6 and a hemispherical top part 7 as described. The conical base part 6 is typically formed from a metal such as titanium or titanium-alloy. Titanium and its alloys are �bone friendly� and easy to machine (but are less preferred for bearing surface applications). The conical exterior surface 6 a of the conical base part is preferably roughened to provide a surface into which bone regrowth will occur in the months after the prosthesis has been surgically fitted to a patient. The roughened surface is preferably formed by electro-discharge machining more commonly known as spark erosion, which involves the removal of material using an electrical discharge from an electrode held above the surface to be modified, in a bath that contains an electrolyte such as kerosene. The electrode is precisely supported above the surface to be eroded by electromechanical feedback control, and is the negative profile of the surface. In the spark erosion process parts of the conical exterior surface of the conical base part are removed so that the surface is eroded to a complex shape. This provides a surface comprising a multitude of small cavities into which bone regrowth will occur to enhance fixation of the prosthesis and minimise loosening. FIG. 13 shows diagrammatically a cross section through the top of a femur some months after fitting of a prosthesis component of the invention showing bone regrowth into the spark eroded lower surface of the conical base part 6. The depth of the spark eroded surface is enlarged for illustrative purposes. Spark erosion is a preferred technique for forming a roughened surface on the conical external surface 6 a of the base component 6, but other techniques for forming a roughened surface may be less preferably utilised such as chemical etching for example. [0041] The conical base 6 comprises a number of holes 10 axially through the base component to enable fastening devices such as screws to pass through the base part into bone to secure the base part to bone (see also FIG. 8c). In the preferred form the conical base part comprises six screw holes through the part whereas in general only three fixing screws will be fitted when fitting the prosthesis, to give more choices of position for screw placement by the surgeon. For example if on fitting the prosthesis part 6 in place during surgery, one of the screw holes 10 is found to be positioned in a weakened area of bone then the surgeon can use an adjacent fixation hole. However it is possible that more or less than three screws may be utilised and that more or less than six screw holes may be provided through the base part 4. [0042] A protrusion 6 b extends from the opposite side of the conical base part and into a recess 7 a in the underside of the hemispherical top part 7, to couple the hemispherical top part and the conical base part. The protrusion 6 b preferably has a slight taper to a reduced diameter at its distal end, and the recess 7 a in the hemispherical top part has a similar taper, to assist in holding the hemispherical top part on the conical base part together. Alternatively the protrusion may extend from the underside of the hemispherical top part into a recess in the conical base part. Further, instead of a single central protrusion it is possible that two or three smaller pins from the conical base part may extend into matching holes in the underside of the hemispherical top part or vice versa. [0043] Preferably the hemispherical top part 7 is formed of a ceramic such as alumina of high density, the hemispherical or part hemispherical external surface of which is highly polished, to provide a bearing surface with minimum friction and the longest possible working life. With the prosthesis of the invention the surface or part of the prosthesis which contacts bone may be formed of a �bone friendly� metal such as titanium or titanium alloy, while the bearing surface of the prosthesis which should have minimum friction and maximum resistance to wear can be formed of a very hard material such as a high density ceramic material or a CoCrMo alloy or other hard bio compatible material, polished to a smooth bearing surface. [0044] The curved external bearing surface of the hemispherical top part 7 may comprise a surface of the material from which the hemispherical top part is formed which has been machined and polished. Alternatively the external surface of the hemispherical top part may first be coated with a harder material such as titanium nitride, by a technique such as vacuum deposition or similar. [0045] The conical part 6 base may be provided with three fins 11 or more or less such fins, which during fitting of the prosthesis will engage into the bone surface to enhance rotational stability of the device. Further, the conical external surface 6 a of the base part may be provided with one or more ribs from the wider periphery of the base part towards the apex or around the external surface 6 a or in any other configuration, to further assist in locating the conical base part against rotation. The ribs may be present on the external surface of the conical base part before spark erosion so that the conical, ribbed surface is roughened by spark erosion as previously described. The ribs or fins may be replaced by other protruding features as will be known in the art. Features as pins for example could also be used although this should not be seen to be limiting. The essential effect is to prevent rotation of the prosthesis when in place. [0046] In the preferred form the conical base part also comprises a pin portion 6 c extending from the apex of the conical base part which when the prosthesis is installed according to the method of the invention will further assist in locating the prosthesis. [0047]FIG. 7 shows a preferred form one part prosthesis of the invention fitted to the head of a femur. The one part prosthesis comprises a conical base 6 which is similarly fitted into a conical recess cut in the head of the femur, and a part spherical top surface 7. The one part prosthesis is typically formed from a metal such as titanium or titanium-alloy. The conical exterior surface of the conical base is preferably roughened to provide a surface into which bone regrowth will occur as referred to previously, and is again preferably formed by spark erosion. The top surface 7 a of the prosthesis is preferably coated with a harder material such as titanium nitride, by a technique such as vacuum deposition or similar, and is machined and polished. [0048] The angle of the walls of the conical base of the one part prosthesis shown is steeper so that the prosthesis is a wedge fit into the conical recess in the head of the femur, and additional screw fixing or similar may not be required. However, in another form of a one part prosthesis of the invention a screw may pass through an access hole through the centre of the prosthesis for example and into bone below the prosthesis. The head of the screw is recessed below the top surface 7 of the-prosthesis. Such an additional fixing screw may not be required however. The one part prosthesis may be provided with fins 11 or similar, as described above for the two part prosthesis of the invention, and comprises a pin portion 6 c extending from the apex of the conical base of the prosthesis which assists in locating the prosthesis. [0049]FIGS. 8a to 8 d show fitting of a prosthesis of the invention to a femur utilising the method of the invention. First, a pilot or guide hole 12 is drilled into the femur coincident with the axis on which the prosthesis is to be fixed. This guide hole 12 is drilled through the centre of curvature of the superior surface of the femoral head as shown. [0050] To ensure correct alignment of the guide hole a tool such as that shown in FIGS. 9 and 12 may be used. In FIG. 12 the tool is shown for illustrative purposes fitted to a cadaveric femur bone. The tool comprises a contact surface, suitably formed by a flexible cup 13 or similar at one end, and a movable arm 14 at the other end. The movable arm 14 is slidably coupled to the shank 15 of the tool and may be fixed in position by a screw coupling 16 which may be tightened or clamped by other suitable means which will hold the arm 14 in position when locked. During a surgical procedure the patient's knee is bent and the cup 13 is fitted to bear against the knee. The arm 14 is moved along shank 15 until metal locating cone 17 is fitted against the femoral head, and then the arm 14 is locked in position. The guide hole 12 into the femoral head is drilled through a correctly angled hole in the end of the movable arm to guide drilling of the hole 12 into the femoral head at the correct angle. In FIG. 12 a drill bit 18 indicates the angle of the drilling guide hole through the end of the movable arm 14 and locating cone 17. The angle of the locating cone 17 can be adjusted by the surgeon prior to beginning drilling of the guide hole 12. [0051] Referring again to FIGS. 8a to 8 d, after the guide hole 12 has been drilled the tool is then removed, and a conical recess 19 is then drilled into the femoral head, coaxially with the guide hole 12 previously formed, using a suitable cutting bit. One form of cutting bit which is fitted to a surgical drill (similar to a drill bit) is shown in FIG. 10. The cutting bit comprises teeth 20 shaped similar to a countersink, so that the cutting bit will form a conical recess as shown in FIG. 8b, the angle of the side walls of which matches the angle of the conical exterior surface 6 a of the conical base part 6 of the prosthesis. The cutting bit comprises a centre pin 20 a which extends beyond the teeth 20 of the bit. In use the central pin is initially inserted into the axial guide hole 12 before cutting of the conical recess 19 begins, to ensure correct location and orientation of the conical recess. A collar 21 around the exterior does not rotate with the bit and can be held by the surgeon. [0052] After the conical recess as shown in FIG. 8b has been formed as described, the prosthesis is fitted in place. In the case of a one part prosthesis the prosthesis may be tapped into place using a small rubber hammer for example. In the case of a two part prosthesis as shown, the conical base part 6 of the prosthesis is first fitted in place. When the conical base part is fitted the pin 6 c on the apex end thereof will engage into the remaining part of the guide hole 12, to further assist in correctly locating the prosthesis. A slide hammer may be used to knock the base part into position, for example. FIG. 11 shows a suitable form of slide hammer, comprising a shaft 22 with a sliding weight 23. In FIG. 11 a conical base part 6 of a prosthesis of the invention is shown on the end of the slide hammer. Such a slide hammer may be used to tap the conical base part of the two part prosthesis into position as shown in FIG. 8c, to engage the radially extending fins 11 and ribs if provided on the external conical surface of the conical base into the femoral bone. After the conical base part has been fitted into the conical cavity in the femoral head as shown in FIG. 8c, bone screws 24 are fitted and screwed securely home to further fix the prosthesis part to the femoral head. The hemispherical top part 7 may then be fitted over the protrusion 6 b of the conical base part, to complete fitting of the prosthesis, as shown in FIG. 8d. [0053]FIG. 13 shows enlarged and diagrammatically bone regrowth into the spark eroded roughened surface of the conical base part at the interface between the prosthesis and femoral bone. Such regrowth will occur over a period of months following fitting of the prosthesis, and further locks the prosthesis in place to inhibit subsequent loosening. As stated spark erosion is one preferred means for roughening the external surface of the conical base part of the prosthesis but the bone contact surface of the prosthesis may be roughened by other means, and/or may incorporate hydroxyapatite, calcium, phosphate, or some other bone enhancing material. [0054] The foregoing describes the invention including a preferred form thereof. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated within the spirit and scope of the invention disclosed and as defined in the appended claims. Referenced byCiting PatentFiling datePublication dateApplicantTitleUS7879106Mar 25, 2003Feb 1, 2011Smith & Nephew, Inc.Hip joint prosthesisUS8152855Sep 17, 2010Apr 10, 2012Howmedica Osteonics Corp.Method and apparatus for hip femoral resurfacing toolingUS8177852Sep 24, 2010May 15, 2012Smith & Nephew, Inc.Hip joint prosthesisUS8231682Jun 2, 2006Jul 31, 2012Depuy Ireland LimitedInstrument for use in a joint replacement procedureUS8273088Jul 8, 2005Sep 25, 2012Depuy Spine, Inc.Bone removal toolUS8585706Jun 2, 2006Nov 19, 2013Depuy (Ireland)Instrument for use in a joint replacement procedureEP1588668A1 *Apr 20, 2005Oct 26, 2005Finsbury (Development) LimitedAlignment guide for use in femoral head surgeryEP1872745A2 *Jun 26, 2007Jan 2, 2008Howmedica Osteonics Corp.Femoral head resurfacingEP2108338A2 *Sep 15, 2006Oct 14, 2009Corin LimitedResurfacing femoral head component* Cited by examinerClassifications U.S. Classification623/23.42, 606/96International ClassificationA61B17/86, A61F2/00, A61F2/40, A61F2/34, A61F2/32, A61B17/17, A61F2/36, A61B17/16, A61F2/30, A61F2/46Cooperative ClassificationA61F2002/30604, A61F2/34, A61B17/86, A61B17/1684, A61F2002/30785, A61F2/3601, A61F2310/00203, A61F2/32, A61F2310/00604, A61B17/1668, A61F2002/4018, A61F2310/00592, A61F2002/30934, A61F2/4607, A61F2310/00023, A61F2220/0033, A61F2002/4037, A61F2002/4681, A61F2002/30332, A61F2310/00796, A61B17/175, A61F2002/3631, A61F2/4081, A61F2002/30884, A61F2/4003, A61F2002/4029, A61F2002/3649, A61F2002/30879, A61F2002/404, A61F2002/3625, A61F2002/365, A61F2310/00029, A61F2/30771, A61F2/4612, A61F2002/30878, A61F2/3603, A61F2/30767, A61F2002/3611, A61F2002/4007, A61B2017/1778, A61F2/40, A61F2002/30205, A61F2002/4631, A61F2230/0067, A61F2310/0088European ClassificationA61B17/16S2F, A61F2/36A, A61F2/36A1, A61F2/40A, A61F2/46B4, A61F2/40, A61B17/17S2FRotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google