Abstract: A femoral head prosthesis is provided with a slot which extends from ventral to dorsal within the distal zone of the stem to separate a tongue-like core from a resilient peripheral portion. The tongue-like core is able to move in the slot in response to bending and twisting stresses. The shear forces which these stresses produce in a transition zone between the bone and the stem are thus, at least, reduced. The slot may be of U-shape with arms parallel to the sides of the stem or with arms parallel to the axis of the stem. One arm of the slot may also be shorter than the other and one arm may be of widening shape relative to the other.

Abstract: A bone implant is provided with undercut anchoring areas for bone tissue which extend from the surface of the implant into the interior. Geometrically shaped cavities are generated through the openings in an interconnected manner to provide for the ingrowth of bone tissue. A high pressure liquid jet is used to form the cone-shaped cavities in the implant on spacings to provide for intercommunication between the respective cavities.

Abstract: A plastic acetabulum is provided with a plurality of cavities in the outer surface. Each cavity opens conically to the exterior of the acetabulum and the cavities are disposed in concentric rows about the axis of the acetabulum. The cavities are provided with a roughly fixed ratio of depth (t) to width (w) with the volume (v), depth (t) and width (w) decreasing from an edge of the acetabulum to a peak of the acetabulum. The depth and width of the cavities each decrease exponentially in proportion to the ratio of the diametric spacings of the cavity rows. Likewise, the volume of the cavities decrease exponentially from row-to-row in the direction of the peak of the acetabulum.

Abstract: The acetabular prosthesis includes a metal supporting shell having collar-shaped projections which have tapered cutting edges for penetrating into the osseous tissue of a pelvic bone. The distal portions of the projections are tapered so that plugs of bone can be formed upon penetration of the projections into the osseous tissue. The projections may be filled with bone chips prior to fitting in of a plastic shell within the metal supporting shell. A multi layer metal mesh is provided on the outer surface of the metal shell for promoting fusion. If the overall attachment is not adequate, the projections can be used for insertion and centering of bone screws.

Abstract: An implant for ingrowth of osseous tissue is constructed of a hollow skeletal three-dimensional support member having a plurality of openings for the ingrowth of osseous tissue into an interior cavity. The surfaces of the beams defining the openings may also be roughened to promote the fusion of tissue.

Abstract: The wire mesh is welded to the metal substrate via step-like protuberances formed on the outer surface of the substrate. The wire mesh is permanently deformed in the regions over the protuberances to facilitate forming of spot welds while the remainder of the mesh outside the zones of the protuberances remains porous for the intake of bone cement or the ingrowth of bone tissue.

Abstract: A hip joint prosthesis in the form of a femur head prosthesis or acetabulum has a mesh secured over at least part of the implant surface to define a cavity between the mesh and the supporting member of the prosthesis. The mesh is made of elastically deformable material to permit inward deformation during implantation. In addition, bone cement can be injected into the cavities so that the mesh then follows the individual shape of the cavity in the bone to mesh into the internal structure of the bone with hardened bone cement.

Abstract: A shaft for a hip joint prosthesis is provided with a square cross-section in the distal region of the shaft. In addition, teeth are provided along each corner of the shaft to provide support on a cortical bone. At least some of other teeth are directed in the proximal direction to displace the osseous tissue rather thanto exert a cutting force on the osseous tissue. The angular stresses occurring when the shaft is inserted in a bone are reduced without the loss of the spaces between the sides of the shaft and bone for the growth of osseous tissue and a revascularization of the bone.

Abstract: The pull-through appliance is made of a mesh structure formed of at least one continuous thread and a pullout thread disposed at one end of the mesh structure to prevent unraveling of the mesh structure. A hollow tube is used to facilitate drawing in of the synthetic strand and autologous strand of the prosthesis. After removal of the hollow member, the resulting package can be readily threaded through a bore in a bone. After implantation, the pull-out thread is removed and the mesh structure unraveled so as to remove the mesh structure from within the bone.

Abstract: A femur head prosthesis consists of a shaft having several plate springs fixed unilaterally, which are enclosed by a thin-walled and deformable shell body. The shell body is connected to the shaft edge and seals the enclosed volume so as to be impermeable to air. The plate springs are laminated springs, which are separated by slits. The depth of the slits towards the proximal end leaves a narrow unslit yoke part. When an intermittent load occurs, a slight bending of the yoke part results and, within the yoke part, a slight displacement of the plate springs with respect to one another to result in a damping and a non-linear increase in the compressive force.

Abstract: An artificial acetabulum has a thin metallic outer shell and a relatively thick metallic inner shell which is secured to the outer shell via a damping ring located at the peripheral edges of the shells. The outer shell has a thickness of less than one-fifth of the thickness of the inner shell to compensate for stresses in the direction of the osseous tissue during the transfer of force peaks. A centering pin is provided on the inner shell and an annular shoulder is provided on the outer shell about the centering pin to provide further elastic damping of forces transmitted between the shells.

Abstract: A centering element for a shank of a femur bone prosthesis is of three-sided pyramidal shape with an equilateral triangular-shaped base. The apex of the centering element is also rounded while a stud is provided at the base for interfitting in a recess in the prosthesis shank. The shape of the centering element enables insertion of the element together with a shank in a cavity in a bone already filled with bone cement.

Abstract: A femur head prosthesis is provided with a shank body for implanting in a femur and a pair of removeably fastened cheeks which are secured to opposite sides at a proximal end of the shank body. The cheeks can be selected from a kit of different sized cheeks. Also, each cheek has a bulge extending laterally from the shank body. Also, each cheek tapers in conically from lateral to medial and from proximal to distal.

Abstract: The vertebrae implant has a stabilizing element which is articulated to a pair of bone screws so as to accommodate skew positions of the bone screws relative to each other. A slotted clamp is provided to secure the stabilizing element to each bone screw. In addition, each clamp is disposed between a shoulder having a spherical surface and a clamping nut. A washer is also disposed between the clamping nut and the clamp. The clamping nut and/or washer is provided with a spherical surface to provide for pivoting of the clamp relative to the bone screw prior to tightening of the clamping nut.

Abstract: An artificial acetabulum is made with a metal inner shell, a thin outer shell which defines a cavity with the inner shell and an elastic force-transmitting member between the two shells to damp forces imposed on the shells. In addition, a metal gauze layer is disposed about the outer shell for the ingrowth of osseous tissue. The inner and outer shells are connected at the edges so as to impermeable to air so that no particles from the cavity between the shells can reach the surrounding environment. A beading is also provided on the outer shell and/or gauze so as to snap into an appropriate undercut in the osseous tissue during primary implantation.

Abstract: A switched-capacitor sigma-delta modulator includes at least one memory element, at least one comparator connected to the at least one memory element, and at least one integrator connected to the at least one comparator. The at least one integrator has a first input stage including a series circuit of a first switch, a first capacitor with two terminals and a second switch, a third switch for connecting one of the two terminals of the first capacitor to ground potential, and a fourth switch for connecting the other of the two terminals of the first capacitor to ground potential. The at least one integrator also has a second input stage connected parallel ot the first input stage including a series circuit of a fifth switch, a second capacitor having two terminals and a sixth switch, a seventh switch for connecting one of the two terminals of the second capacitor to ground potential, and an eighth switch for connecting the other of the two terminals of the second capacitor to ground potential.

Abstract: The reinforcement for the proximal region of a bone cement bed for a femoral head prosthesis includes a grid of crossing members at least some of which are wavy. The wavy members have a high wavy shape lengthwise and spring in as the gap between a bone cavity and a prosthesis stem narrows. The prosthesis is fixed by averaging out of the restoring forces and the gap size mechanically until the bone cement has cured.

Abstract: An integratable amplifier circuit includes a preamplifier stage, a drive stage, a push-pull end stage, and a regulating stage forming a differential value from a reference current and from a measurement current proportional to the static current flowing through the push-pull end stage. The regulating stage stores the diferential value or a value proportional thereto upon the occurrence of a control signal at a control input indicating the non-level control of the preamplifier stage and sets the static current of the push-pull end stage by varying the operating point of the push-pull end stage as a function of the stored value.

Abstract: The rasp-like reaming instrument is constructed as a hollow body with exterior teeth and openings adjacent the teeth. During use, bone material which is peeled off by the teeth is directed through the openings into the interior of the body to avoid accumulation of the material under the teeth. The cutting edges of the teeth remain unencumbered during a reaming operation.

Abstract: An integratable amplitude-regulated oscillator circuit includes a resonator element, a control element having a control input, an inverter having an output and an input coupled to one another through the resonator element and having a quadrature-axis current component being variable by the control element, an amplitude regulating circuit having an input connected to the input of the inverter and an output connected to the control input of the control element, and an output stage having an input connected to the input of the inverter. The amplitude regulating circuit includes a differential amplifier having an inverting input and a non-inverting input, a first peak value rectifier connected upstream of the inverting input, and a second peak value rectifier connected upstream of the non-inverting input.