EP0740535A1 - Tete spherique elastique pour implants d'articulation de la hanche - Google Patents

Tete spherique elastique pour implants d'articulation de la hanche

Info

Publication number
EP0740535A1
EP0740535A1 EP95937784A EP95937784A EP0740535A1 EP 0740535 A1 EP0740535 A1 EP 0740535A1 EP 95937784 A EP95937784 A EP 95937784A EP 95937784 A EP95937784 A EP 95937784A EP 0740535 A1 EP0740535 A1 EP 0740535A1
Authority
EP
European Patent Office
Prior art keywords
ball head
elastic
ball
head according
intermediate member
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95937784A
Other languages
German (de)
English (en)
Inventor
Gerd Hörmansdörfer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE4441033A external-priority patent/DE4441033A1/de
Priority claimed from DE19517843A external-priority patent/DE19517843B4/de
Application filed by Individual filed Critical Individual
Publication of EP0740535A1 publication Critical patent/EP0740535A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/32—Joints for the hip
    • A61F2/36—Femoral heads ; Femoral endoprostheses
    • A61F2/3609—Femoral heads or necks; Connections of endoprosthetic heads or necks to endoprosthetic femoral shafts
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/30767—Special external or bone-contacting surface, e.g. coating for improving bone ingrowth
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
    • A61F2002/30108—Shapes
    • A61F2002/3011—Cross-sections or two-dimensional shapes
    • A61F2002/30112—Rounded shapes, e.g. with rounded corners
    • A61F2002/30136—Rounded shapes, e.g. with rounded corners undulated or wavy, e.g. serpentine-shaped or zigzag-shaped
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
    • A61F2002/30316—The prosthesis having different structural features at different locations within the same prosthesis; Connections between prosthetic parts; Special structural features of bone or joint prostheses not otherwise provided for
    • A61F2002/30329—Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
    • A61F2002/30331—Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements made by longitudinally pushing a protrusion into a complementarily-shaped recess, e.g. held by friction fit
    • A61F2002/30332—Conically- or frustoconically-shaped protrusion and recess
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
    • A61F2002/30316—The prosthesis having different structural features at different locations within the same prosthesis; Connections between prosthetic parts; Special structural features of bone or joint prostheses not otherwise provided for
    • A61F2002/30535—Special structural features of bone or joint prostheses not otherwise provided for
    • A61F2002/30563—Special structural features of bone or joint prostheses not otherwise provided for having elastic means or damping means, different from springs, e.g. including an elastomeric core or shock absorbers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
    • A61F2002/30316—The prosthesis having different structural features at different locations within the same prosthesis; Connections between prosthetic parts; Special structural features of bone or joint prostheses not otherwise provided for
    • A61F2002/30535—Special structural features of bone or joint prostheses not otherwise provided for
    • A61F2002/30565—Special structural features of bone or joint prostheses not otherwise provided for having spring elements
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2002/30001—Additional features of subject-matter classified in A61F2/28, A61F2/30 and subgroups thereof
    • A61F2002/30316—The prosthesis having different structural features at different locations within the same prosthesis; Connections between prosthetic parts; Special structural features of bone or joint prostheses not otherwise provided for
    • A61F2002/30535—Special structural features of bone or joint prostheses not otherwise provided for
    • A61F2002/30593—Special structural features of bone or joint prostheses not otherwise provided for hollow
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2/00—Filters implantable into blood vessels; Prostheses, i.e. artificial substitutes or replacements for parts of the body; Appliances for connecting them with the body; Devices providing patency to, or preventing collapsing of, tubular structures of the body, e.g. stents
    • A61F2/02—Prostheses implantable into the body
    • A61F2/30—Joints
    • A61F2/32—Joints for the hip
    • A61F2/36—Femoral heads ; Femoral endoprostheses
    • A61F2/3609—Femoral heads or necks; Connections of endoprosthetic heads or necks to endoprosthetic femoral shafts
    • A61F2002/365—Connections of heads to necks
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2220/00—Fixations or connections for prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2220/0025—Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements
    • A61F2220/0033—Connections or couplings between prosthetic parts, e.g. between modular parts; Connecting elements made by longitudinally pushing a protrusion into a complementary-shaped recess, e.g. held by friction fit
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2230/00—Geometry of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2230/0002—Two-dimensional shapes, e.g. cross-sections
    • A61F2230/0004—Rounded shapes, e.g. with rounded corners
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2310/00—Prostheses classified in A61F2/28 or A61F2/30 - A61F2/44 being constructed from or coated with a particular material
    • A61F2310/00005—The prosthesis being constructed from a particular material
    • A61F2310/00011—Metals or alloys
    • A61F2310/00023—Titanium or titanium-based alloys, e.g. Ti-Ni alloys
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2310/00—Prostheses classified in A61F2/28 or A61F2/30 - A61F2/44 being constructed from or coated with a particular material
    • A61F2310/00005—The prosthesis being constructed from a particular material
    • A61F2310/00011—Metals or alloys
    • A61F2310/00029—Cobalt-based alloys, e.g. Co-Cr alloys or Vitallium
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2310/00—Prostheses classified in A61F2/28 or A61F2/30 - A61F2/44 being constructed from or coated with a particular material
    • A61F2310/00389—The prosthesis being coated or covered with a particular material
    • A61F2310/00395—Coating or prosthesis-covering structure made of metals or of alloys
    • A61F2310/00407—Coating made of titanium or of Ti-based alloys
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2310/00—Prostheses classified in A61F2/28 or A61F2/30 - A61F2/44 being constructed from or coated with a particular material
    • A61F2310/00389—The prosthesis being coated or covered with a particular material
    • A61F2310/00574—Coating or prosthesis-covering structure made of carbon, e.g. of pyrocarbon

Definitions

  • the invention relates to a special ball head for artificial hip joint systems for use as an implant in human medicine.
  • the femur does not, however, represent the shortest connecting line between these two points. Rather, the course of the femoral neck from the ball head to the greater trochanter and further down to the knee joint results in a deflected line, which is removed from an arch remind. This shape causes a slight rebound of the femur when vertical load is applied to the natural femoral head, because the femur is partially loaded with axial forces and partially with bending moments. This elastic structural behavior is advantageous in conjunction with the damping properties of the bone, since it leads to a weakening of the load peaks conducted into the pelvis when the bone apparatus is subjected to dynamic loads, for example when running.
  • the stiffening of the overall system associated with the insertion of an artificial joint means that the dynamic load peaks are transmitted with less damping and thereby lead to an undesirably high stress on the interfaces between the implant and bone, which can lead to premature loosening of the implant .
  • the spherical joint part has a recess into which a hat-shaped body made of an elastomer is inserted.
  • a conical sleeve is inserted into this. It is also proposed to divide the hat-shaped body into chambers and to fill it with a liquid-gas mixture.
  • Another disadvantage is the positive connection between the resilient element made of an elastomer and the spherical part or the conical sleeve, the mutual position of which is fixed only by beads and corresponding grooves, because relative movements between the individual components would be unavoidable under mechanical stress which would lead to abrasion and wear in the long run.
  • An inclusion of the spherical element itself in the spring path is not provided for in the aforementioned invention.
  • a related design of a sprung ball head is known from German published patent application DE 4204979 AI. It is proposed here to mount the solid spherical body axially displaceably by means of a cylindrical fit directly on the hip stem and to couple it elastically by means of a column made of disc springs.
  • this design requires specially adapted hip stem pins. The ball head cannot be plugged onto the standardized and widely used conical pins. For the rest, there are also the disadvantages of the extreme elastic anisotropy and of the stress direction. direction of divergent displacement, as well as wear due to metallic friction.
  • the rigid element has the shape of a conical sleeve and is used to couple the hip joint ball to the corresponding pin of the shaft.
  • the first of the two elastic elements is the actual spherical body in the form of a spherical shell, which is essentially responsible for elastic conforming to the sliding surface of the pan.
  • the second of the two elastic elements is an elastic intermediate member, which is integrated in the force transmission path between the rigid element and the elastic spherical shell and is firmly connected with its coupling points or surfaces to the two other elements mentioned . It has the task of developing a spring effect within the force transmission path.
  • the invention it is proposed to thin the spherical shell in its wall thickness so that on the one hand the required fatigue strength is given, on the other hand sufficient elasticity is achieved in relation to the desired conformity.
  • wall thicknesses of between about 0.6 and 2.0 millimeters are well suited for realizing the objective envisaged.
  • flattened portions of the spherical shell are formed on the respective load surface, which are proportional to the load size with their surface area and, with a suitable wall thickness, form a correspondingly large-area support to the friction partner.
  • the invention proposes various attachable embodiments of the elastic ball head, which can be produced entirely from a metallic material.
  • the elastic intermediate member is integrally connected to the other two elements spherical body / shell and conical sleeve.
  • Intermediate links in the form of curved surfaces which have a cross-section e.g. corrugated membrane or bellows-like, arched or the like, and are designed with relatively thin wall thicknesses.
  • ball heads of this type are generally not easily produced in one piece, depending on their shape, so that they consist of individual parts, e.g. manufactured by machining or forming and then e.g. must be connected by welding.
  • high quality welding processes are available, e.g. laser welding or electron beam welding, which are also economical for the production of larger series.
  • the ball heads according to the invention could be produced in one piece much more easily using the precision casting process. At the moment, however, it is not possible to make a reliable statement as to whether the strength values reduced in investment casting materials would surely be able to withstand permanent stress.
  • Chromium-cobalt-molybdenum alloys or titanium alloys can be used as materials for the hip joint head according to the invention. Both material groups are suitable as forged alloys in terms of their strength. Titanium alloys (eg titanium-aluminum-vanadium or titanium-aluminum-niobium) have an approximately half the value of the modulus of elasticity reduced compared to the chromium-cobalt-molybdenum alloys, which is approximately one for the application at hand Doubling the travel means. The use of a titanium alloy also appears to be advantageous because of its good tolerance to the body, or because of the material equality in the case of combination with a titanium shaft, which is one Prevents galvanic element formation. However, titanium alloys are known to be poor friction partners, so that a suitable coating appears indispensable for the polished spherical surface.
  • titanium alloys are known to be poor friction partners, so that a suitable coating appears indispensable for the polished spherical surface.
  • the surface of the ball head be coated with one of the coatings available today using e.g. the PVD or CVD process in order to reduce the coefficient of friction.
  • the surface of the ball head be coated with one of the coatings available today using e.g. the PVD or CVD process in order to reduce the coefficient of friction.
  • seizure of the attachable ball head on the journal of the shaft can also be reliably prevented.
  • a coating of the spherical head with a doped superhard carbon by means of the PCVD method is particularly advantageous, whereby diamond-like properties of the surface can be achieved.
  • Such a layer which is known under the brand name DYNAMANT from IKOS GmbH, Hoesbach, not only has the lowest dry friction values, but also a very high elastic resilience, so that it is almost ideal for the present application.
  • the above-mentioned layer of diamond-like carbon still offers a certain potential for further improvement for the present application, for example by varying the deposition parameters. ter or suitable doping. If this layer is particularly recommended here in connection with the invention, however, it should not be concluded from this that this type of coating alone would be suitable for the ball head according to the invention. Extensive research and development takes place in this area, which results in a constantly increasing level of knowledge. For tribological reasons, the wettability of the layer surface by creating a hydrophilic characteristic appears to be of particular importance in order to ensure the maintenance of a liquid film for lubricating the sliding surfaces.
  • the mixed friction behavior aimed at for the articulation system with a separating lubricating film in the form of the synovial fluid is supported when using the spherical head according to the invention in that on the one hand a complete displacement of the lubricating film is avoided on the one hand due to the greatly reduced specific surface load and on the other hand by the periodic deformation the spherical shell, for example A pumping effect occurs when walking, as a result of which synolval fluid is constantly moved in the articulation gap.
  • FIG. 5 shows a finite element discretization of the spherical shell and the elastic intermediate member that is plotted slightly enlarged compared to the first four figures, which corresponds to the design concept proposed with FIG.
  • FIG. 6 shows an excessive deformation of the system under a typical force.
  • Fig.l shows a version in which the spherical shell 1 with the conical sleeve 3 is cohesively connected via an elastic intermediate member 2 in an arch shape.
  • This intermediate member can be modified in the direction of a more corrugated membrane-like shape.
  • the overall elasticity of the example shown is not very high and also somewhat more anisotropic, on the other hand this embodiment can be manufactured quite easily, for example by so-called superplastic deep drawing or forming.
  • the spherical shell 4 merges into an elastic intermediate member 5 by means of a hairpin-like arch 8 in cross section, which in turn opens out into the inner sleeve 6 with a corrugated edge 7.
  • a further variant of the spherical head according to the invention is presented in the drawing figure 3, which although it performs less favorably with regard to the desired homogeneous deformation of the spherical shell under load, but is intended here to serve as an example for the scope of the invention.
  • An elastic intermediate member 10 with a S-shaped cross section is used, which is connected to the outside in the equatorial region 12 of the spherical shell 9 and inwards in the coupling zone 13 of the conical sleeve 11.
  • the design concept according to FIG. 4 proved to be particularly advantageous.
  • the spherical shell 14 merges softly at its lower edge 17 into the elastic intermediate member 15, which in turn opens into the conical sleeve 16 in the region 18.
  • the intermediate member had a quite isotropic suspension behavior with spring travel up to to 0.1 millimeters.
  • the maximum stresses were at values of up to around 330 N / mm 2 and thus in a clear safety distance from those for fatigue stress of 10 million cycles allowable stresses of about 500 N / mm 2 .
  • the FE analyzes also provided indications that, depending on the ball diameter, wall thicknesses for the spherical shell between approximately 0.8 and 1.8 millimeters result in low stresses without problems and at the same time ensure the elasticity also sought for the spherical shell itself.
  • the desired conforming behavior of the spherical shell it is proposed to define its wall thickness so that the reference stresses in the material when subjected to a force of 3000 N by means of a spherical cap with a maximum diameter of 0.5 millimeters from the usual stress directions (e.g. between about 30 and 50 ° to the axis of symmetry of the spherical head) at no point exceed the permissible value of the continuous load for ten million load cycles for the material of the shell casing.
  • the deformation of the spherical shell towards a flattening under the same load introduction must be at least large enough to reduce the specific surface load of the counterpart (e.g.
  • the shell casing which is associated with the flattening and is equivalent to the load axis must not be greater than the difference between the diameter of the ball and that of the friction partner calotte in order to reliably rule out clamping effects.
  • the displacements of the structure were calculated using a finite element analysis.
  • 5 shows the unloaded initial configuration
  • FIG. 6 shows the structure deformed under load.
  • the acting force F was set at 3000 N and its direction of action was assumed according to the arrow.
  • the wall thicknesses used for the model of 1.25 mm for the elastic intermediate member and 1.75 mm for the spherical shell cannot be seen.
  • the internal conical sleeve omitted, since it is not part of the elastic system.
  • the plots each show the same spherical head in a spatial position which corresponds approximately to the installation situation in the human body, that is to say with the axis of symmetry inclined approximately 45 ° with respect to the vertical.
  • the ball head according to the invention can also be produced without problems as a so-called large head or as an inner part of a duo head. Special ball heads of this type are required if a patient receives an artificial hip shaft, for example after a femoral neck fracture, but it is not necessary to replace his own acetabular cup. In these applications, too, the parts of the design according to the invention fully to bear.
  • the invention provides a ball head which can be plugged onto common hip joint shafts with standardized connecting pins and which can be expected to have favorable effects on the service life of such artificial joints in that its spring action dampens the dynamic stress on the bone apparatus involved, in particular on the Contact points to the implant causes.
  • the annoying wear of the articulating friction partner made of polyethylene is significantly reduced by a multiplicative effect of the various elastic properties of the spherical head according to the invention, on the one hand by reducing the amplitude of the acting load peaks by means of the elastic intermediate member and on the other hand by elastic nestling of the spherical shell can be spread over a larger area.
  • the invention can also be put into practice with justifiable effort, it being possible in large part to use proven materials and processes.
  • the ball head according to the invention can be produced in a wide variety of sizes up to the large head ball, and in a wide variety of designs up to integration in a duo head.
  • the advantageous effects of the invention such as extensive elimination of the wear on the articular surface or protection of the contact surfaces between the implant and the bony bearing, make it possible that revision operations on such artificial joints will only be necessary at larger time intervals or else become completely superfluous.

Landscapes

  • Health & Medical Sciences (AREA)
  • Orthopedic Medicine & Surgery (AREA)
  • Cardiology (AREA)
  • Oral & Maxillofacial Surgery (AREA)
  • Transplantation (AREA)
  • Engineering & Computer Science (AREA)
  • Biomedical Technology (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Vascular Medicine (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Prostheses (AREA)

Abstract

L'invention concerne une tête sphérique spéciale pour articulations artificielles de la hanche. Les têtes sphériques de la technique antérieure sont soit reliées de façon fixe à la "tige" de la hanche, soit emboîtables sur son col conique. Elles sont massives et réalisées par exemple dans des matériaux métalliques ou céramiques. De par leur conception, elles ne présentent pas de propriétés élastiques et ne peuvent donc pas avoir un effet amortisseur ni s'adapter aux surfaces de glissement dans le cotyle. Le fémur perdant une grande partie de son élasticité naturelle en raison de la pose de la tige de hanche artificielle, le système global, constitué par le fémur, la tige et la tête, présente alors une rigidité mécanique défavorable. En outre, il apparaît une abrasion du polyéthylène au niveau des surfaces de contact pratiquement ponctuelles entre la tête sphérique et la surface de glissement du cotyle. La tête sphérique selon l'invention non seulement améliore la flexibilité du système global, mais réduit en outre l'abrasion, car elle possède elle-même des propriétés élastiques, liées au fait que son enveloppe (1, 4, 9, 14) présente des parois de faible épaisseur et est raccordée par liaison de matière à la douille conique intérieure (3, 6, 11) au moyen d'un élément élastique (2, 5, 10, 15). Cette tête sphérique réalisée dans un matériau métallique est de préférence revêtue en surface.
EP95937784A 1994-11-17 1995-11-16 Tete spherique elastique pour implants d'articulation de la hanche Withdrawn EP0740535A1 (fr)

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
DE4441033A DE4441033A1 (de) 1994-11-17 1994-11-17 Elastischer Kugelkopf für Hüftgelenkimplantate
DE4441033 1994-11-17
DE19517843 1995-05-18
DE19517843A DE19517843B4 (de) 1995-05-18 1995-05-18 Elastischer Kugelkopf für Hüftgelenkimplantate
PCT/DE1995/001620 WO1996015735A1 (fr) 1994-11-17 1995-11-16 Tete spherique elastique pour implants d'articulation de la hanche

Publications (1)

Publication Number Publication Date
EP0740535A1 true EP0740535A1 (fr) 1996-11-06

Family

ID=25942072

Family Applications (1)

Application Number Title Priority Date Filing Date
EP95937784A Withdrawn EP0740535A1 (fr) 1994-11-17 1995-11-16 Tete spherique elastique pour implants d'articulation de la hanche

Country Status (3)

Country Link
EP (1) EP0740535A1 (fr)
AU (1) AU3867095A (fr)
WO (1) WO1996015735A1 (fr)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9023112B2 (en) 2011-02-24 2015-05-05 Depuy (Ireland) Maintaining proper mechanics THA
US9668745B2 (en) 2011-12-19 2017-06-06 Depuy Ireland Unlimited Company Anatomical concentric spheres THA
US20130304225A1 (en) * 2012-05-08 2013-11-14 Richard D. Komistek Optimal contact mechanics for a tha
US8858645B2 (en) 2012-06-21 2014-10-14 DePuy Synthes Products, LLC Constrained mobile bearing hip assembly

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2545351B3 (fr) * 1983-05-02 1986-07-11 Gabard Jean Jacques Prothese femorale de la hanche
EP0220803A3 (fr) * 1985-09-16 1987-10-21 Dow Corning Corporation Prothèse fémorale de la hanche en plusieurs parties
FR2621814B1 (fr) * 1987-08-19 1993-06-25 Benoist Girard Cie Sa Prothese orthopedique, en particulier pour la tete du femur
HU204427B (en) * 1989-01-12 1992-01-28 Metrimed Orvosi Mueszergyarto Round head for hip-joint endrorotheses and method for producing the round head
DE4204979C2 (de) * 1992-02-19 1995-06-22 Koehler Gerd Prof Dr Gelenkprothese

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9615735A1 *

Also Published As

Publication number Publication date
WO1996015735A1 (fr) 1996-05-30
AU3867095A (en) 1996-06-17

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