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
  • A61F2/38—Joints for elbows or knees

Definitions

• the invention relates to an artificial prosthesis part intended for the construction of an endoprosthesis for the human knee joint and which functions as a kinematic function, illustrated in the front view (FIGS. 1 a, 1 b) in the view from the side (Fig. 2) and in a three-dimensional view (Fig. 3a, 3b).
• This prosthesis part is a composite joint and consists of two rigidly connected rod ends (3 and 6) and two rigidly interconnected joint cups (4 and 7).
• the articular surface of the first condyle (3) is like the articular surface of the second condyle (6) in the front view (Fig. 1 a, Fig.
• the joint has a first, by a first condyle (3) and a first socket (4) formed Gelenkkompartiment (2) and a second Gelenkkompar-- (5) formed by a second condyle (6 ) and a second socket (7).
• the joint function is established and the first joint head (3) and the first joint socket (4) contact K m in the first joint compartment (2) and the second joint socket (6) and the second joint socket in the second joint compartment (5) (7) at the contact point K
• the flexion / extension of the composite joint Fig.
• the contact point K m moves in the functional plane FE Km of the first joint compartment (2) on the first condyle (3) along the plane contact line c FM and simultaneously in the first socket (4) along the plane contact line C T M and the contact point K
• the articular surface of the first condyle (3) is rotationally symmetrical with the axis of rotation M F M which is perpendicular to the functional plane FE Km and thus passes through the center of curvature of the contact line C F M.
• the joint surface of the second condyle (6) is also rotationally symmetrical and accordingly has the axis of rotation M FI _, which is perpendicular to the functional plane FE K i and thus passes through the center of curvature of the contact line c F i_.
• the axes of rotation M FM and M FI _ are parallel to each other and have an offset f, which is designed so that the rotational axis M FL with respect to the rotation axis M FM is always moved to the rear (med.: To posterior) and in special versions additionally upwards (Fig. 2, Fig. 1 b) or downwards (med. after cranial or cadaver).
• the joint surface of the first joint socket (4) is rotationally symmetrical with the rotation axis MTM, which is perpendicular to the functional plane FE Km and thus extends through the center of curvature of the contact line C T M.
• the joint surface of the second joint socket (7) is also rotationally symmetrical and accordingly has the rotation axis MTL, which is perpendicular to the functional plane FE K i and thus passes through the center of curvature of the convex contact line c T i_.
• the rotation axes M T M and MTL are parallel to each other and have the distance t from each other.
• the position of the femur is clearly given by the angle of flexion ⁇ , by which the femur (f) from the initial angular position ⁇ 0 has turned (Fig. 2).
• the position of the instantaneous axis of rotation (MDA) is uniquely defined by the angle of rotation ⁇ of the femur (f) because the instantaneous axis of rotation (MDA) passes through the intersection point (P) of the two wings r m and ⁇ (Fig.
• the distances f, t, r m and ⁇ dependent on the angle of flexion ⁇ . It is particularly advantageous to design essentially only the distance f from the angle of flexion ⁇ .
• the distance f should be chosen so that in the flexion 0 ° ⁇ ⁇ 30 ° optimal rolling of the articular surfaces prevails, then the distance f as a function of the rotation angle ⁇ decreases monotonically and completely disappears at large flexion angles, so then the two femoral axes M F M and M F i_ coincide.
• artificial joint represents the parallel connection of two planar cam gears, which are characterized by the plane contact line pairs C F M; C T M and c F i_; C T L are given, which causes the forced run in flexion / extension in the artificial joint.
• the four parallel axes have a common point of intersection at infinity and therefore produce even movements of the joint section. Without loss of generality, the above and other descriptions apply, even in cases where the four axes have a common point of intersection.
• the prosthesis then inevitably performs spherical movements.
• the "function levels" become concentric spherical surfaces around the common point of intersection of the axes.
• the joint force m is mated, whose line of action coincides with the common normal n m at the contact point K m of the two joint surfaces (contact surface C m ), and in the second joint compartment (5) the joint force F l , whose line of action with the common normal ni at the contact point K
• the normals n m and ni generally do not intersect. They have a shortest distance d, which is both perpendicular to the normal n m and perpendicular to the
• the artificial joint described above has four kinematic degrees of freedom, one "big” and three “small” ones.
• the great degree of freedom (which describes the knee function of flexion / extension) is actively used by the muscles: in the reference system of the tibia (t) the femur is flexed - at small angles of flexion guided by the wings r m and ⁇ of the quadrilateral and in large guided by the hinge axis, given by the coincident femoral axes M F M and M F T, where the position of the femur clearly given is by the flexion angle.
• the three "small” degrees of freedom are a rotation around the axis given by the surface normals n m and b rotation about the axis given by the surface normal r i and c rotation about the axis given by the distance line d the latter represents ab-adduction in the knee joint.
• These three "small degrees of freedom” are not actively served by the musculature, but they are stabilized by it.
• the greater the amount of resultant joint force F R the more stable is the balance between femur and tibia.
• this mechanism has already been described in EP 1 382 314 A2.
• (Contact surface Ci) and the common tangent surface of the articular surfaces in the contact point K m (contact surface C m ) is to be arranged inclined so that it rises in the respective contact point to the inner joint.
• and A m are uniquely defined in the sectional planes M F LM T L (distance ⁇ ) and MFM-MTM (distance r m ) (FIGS. 3 a, 3 b). From these inclination angles ⁇
• FIG. 1 a an inventive joint in an extended position in one
• Figure 1 b shows the joint shown in Figure 1 with marked axes of rotation.
• Fig. 2 is a schematic representation of a joint according to the invention in one
• Front view; 3a shows an artificial joint in the extended position in a three-dimensional view from the front side;
• Fig. 3b shows another view of the artificial joint in the extended position in
• FIG. 1 a shows an artificial joint 1 in the extended position in the front view with a first joint compartment 2 comprising a first joint head 3 and a first joint socket 4.
• a functional plane of a first joint contact K m is designated FE Km . Due to the Hertzian surface pressure under adhesion, there is a small contact area C m . Furthermore, a second joint compartment 5 with a second joint head 6 and a second joint socket 7 can be seen.
• is denoted by FE K i. Due to the Hertzian surface pressure under frictional connection, a small contact surface C
• FIG. 2 shows an artificial joint according to the invention in an extended position in a side view, which illustrates the four-joint networking of the four morphologically given axes in the functional plane of the flexion / extension by the axial distances t, r m , f, ⁇ .
• the axis M F M is determined by the center of curvature of the femoral contact line C F M at the contact point K m .
• the axis M FL is defined by the center of curvature of the femoral contact line c FL at the contact point K
• the axis M TM is determined by the center of curvature of the tibial contact line C T M at the contact point K m .
• the axis M TI _ is through the center of curvature of the tibial contact line c T i_ in the contact point K
• R T M radius of curvature of the contact track C T M on the medial tibial articular surface, given by the distance K m M TM , and
• R FM radius of curvature of the contact track c FM on the medial femoral articular surface, given by the distance K m M TM .
• cpo initial position of the angle of rotation of f in relation to t.
• RTL radius of curvature of the contact track c T i_ on the medial tibial articular surface, given by the distance K
• RFL radius of curvature of the contact track c F i_ on the medial femoral articular surface given by the distance K
• FIGS. 3a and 3b an artificial joint in the extended position can be seen laterally in the three-dimensional view from the front.
• the current axis of rotation of the four-bar linkage is designated MDA.
• the sectional contours (first joint head 3, first joint socket 4) are obtained by the section of the first joint compartment 2 with the plane M TM -M FM .
• the sectional contours (second condyle 6, second acetabulum 7) result from the section of the second articulated compartment 2 with the plane M FI _-M TI _.

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• Health & Medical Sciences (AREA)
• Orthopedic Medicine & Surgery (AREA)
• Physical Education & Sports Medicine (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)

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Citations (4)

• 2013
  • 2013-01-23 WO PCT/DE2013/100023 patent/WO2013110269A1/fr not_active Ceased

Patent Citations (4)

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