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M Semlitsch

Publications and source records attributed to M Semlitsch.

36 records · Page 2Linked to original sources
PubMed1982

Concept and material properties of a cementless hip prosthesis system with Al2O3 ceramic ball heads and wrought Ti-6Al-4V stems.

A cementless total hip system of modular design is presented. The design of the stem provides for a firm seating on the cortical bone over a large area. Therefore primarily stable fixation is accomplished. The stem in seven different sizes is made of hot forged Ti-6Al-4V Protasul-64 WF alloy of high corrosion fatigue strength. The Biolox ceramic ball with three different neck lengths is connected to the high strength stem by means of a special selflocking conical spigot with a structured surface. The ceramic ball is combined with a polyethylene screw socket in four different sizes, designed by Endler and anchored in the acetabulum without acrylic cement. This hip prosthesis system has proved itself in clinical application since 1979.

Alloys↗
PubMed1979

The morphology of polymethylmethacrylate (PMMA) bone cement: surface structures and causes of their origin.

This study deals with the correlation between the polymerizing bone cement and the surrounding tissue. The surface structures of bone cements, polymerized in air, in tissue medium (in vitro) and in human bone during implantation were investigated and compared with the contours of the tissue of the implant bed. Basing on the dimensional differences it was differentiated between contours of 1st order and 2nd order: contours of 1st order are within the macroscopic range, contours of 2nd order within the microscopic range. The surface of bone cement polymerized in living human tissue differed essentially from samples polymerized under laboratory conditions. The differences are to be seen macroscopically in the coarse relief as well as microscopically in the shape and the connection of the superficial methylmethacrylate beads. Bone cements, polymerized in air show an ideal, even and closed surface. Bone cements, polymerized in tissue medium exhibit macroscopically some wrinkles, in the microscopic range their contours are either closed (samples prepolymerized at 22 degrees C) or partly open and partly closed (samples prepolymerized at 24 degrees C). The surface of bone cement implants, retrieved from human bones are characterized macroscopically by a marked wrinkled and papillary relief, microscopically by flattened beads, and most often by an irregular, rough and open surface with isolated beads giving almost the impression of a porous surface structure. The character of the surface of the bone cement originates from external, mechanical influences, from changes in the volume of the bone cement and from effects of the surrounding tissues. The surface of the bone cement implanted in human bone conforms exactly with the contour of the adjacent tissue; the tissue contour is infact a negative of the cement surface. The incomplete connection between the superficial PMMA beads seems to be of some practical value: In areas, where the PMMA beads are largely isolated, the mechanical stressability of the "polymer composite" is relatively low. Under high load, beads and bead-clusters may break off the surface. Shattering of bone cement implants possibly may start from such an open, porous surface area where PMMA beads are extensive isolated.

Acrylic Resins↗
PubMed1978

Corrosion behavior of cast and forged cobalt-based alloys for double-alloy joint endoprostheses.

An ideal combination of mechanical and corrosion properties of long-term implants such as joint endoprostheses has yet to be found. Besides being resistant to pitting and crevice attack, which can lead to corrosion fatigue and stress corrosion cracking failures, the implant material must be highly resistant to wear and abrasion. Two cobalt-based alloys, wrought CoNiMoTi and air-cast CoCrMo, were subjected to a number of selected in vitro electrochemically and chemically accelerated corrosion tests in chloride-containing solutions with wrought AISI-316L used as a reference alloy. A limited number of immersion tests in FeCl3 and acidified FeCl3 solutions were also conducted. It is found that the mechanical properties of wrought CoNiCrMoTi alloy qualify it as a substitute for cast CoCrMo alloy and wrought AISI-316L in anchorage shaft production for all types of joint endoprostheses. Wrought CoNiCrMoTi has a higher resistance to fatigue cracking compared with cast CoCrMo and is as resistant to selective corrosion phenomena such as stress corrosion cracking.

Alloys↗
PubMed1977

Reactions of the articular capsule to wear products of artificial joint prostheses.

Examination of a great number of tissue samples taken from the newly formed capsules surrounding artificial joints reveals small particles of prosthetic material. Abraded from the joint by wear and tear, these particles of plastic, metal, and acrylic cement initiate a foreign-body reaction and result in the formation of granulation tissue, including macrophages and foreign-body giant cells. Typical features of tissue reactions exist for each of the materials from which prostheses are made. The consequent formation of scar tissue produces a thickening of the capsule, which, in turn, may cause a reduction in the mobility of the joint. In small amounts, the foreign-body particles are eliminated via the perivascular lymph spaces. Where this transport system is insufficient to handle the volume, however, the foreign-body response may extend to the whole environment surrounding the joint. In such cases, there may be loosening of the cemented prosthetic parts because of deterioration of contiguous bone anchors by the tissue membrane lining the bone cement.

Foreign-Body Reaction↗
PubMed1977

New prospects for a prolonged functional life-span of artificial hip joints by using the material combination polyethylene/aluminium oxide ceramin/metal.

Investigations over the years have shown that the mirror-finished Al2O3 ceramic is a much more suitable frictional counterpart to ultrahigh molecular weight (UHMW) polyethylene than metal. Despite the extremely gread hardness difference between polyethylene and Al2O3 ceramic, a considerable lower wear rate is obtained for the polyethylene socked with this new low-friction material combination. The unexpectedly favorable tribological behavior of this ceramic material in contact with polyethylene may be attributed to the following factors: better values for corrosion resistance characteristics, wettability with liquids, surfact gloss, hardness, and scratch resistance of the ceramic material in comparison with those of the hitherto used metallic implant materials (AISI-316L steel or cast Co-Cr-Mo alloy). It appears that, by using this new combination of materials for the socket and the ball, it will be possible to prolong the service life of artificial hip joints considerably without having effecy any fundamental changes in the present design and implantation principle retaining the hitherto used anchorage shaft made of wrought Co-Ni-Cr-Mo-Ti alloy Protasul-10 of extremely high corrosion fatigue strength.

Alloys↗
PubMed1977

[Assorted aluminium-oxide ceramic heads for prostheses of the hip-joint. A preliminary communication (author's transl)].

In the search for even more hard-wearing prostheses of the hip, a rotating total- and femoral head prosthesis and a total- and femoral head prosthesis with fixed detachable heads are described, the head of which is made from highly polished aluminium oxide ceramic, Biolox. For total prostheses the excellent gliding features between ceramic head and polyethylen acetabulum are being used. They will also permit return to proved metal-polyethylen prostheses, should the ceramic head fracture. The fracture prosthesis provides both such an exchange and conversion into a total prosthesis. Extending the present programme of rotation-prostheses to ceramic heads will require a wide assortment of heads. This will mean not only wide adaptability but also the need for detailed knowledge of this assortment, the use of which demand thorough preparation of the surgeon. In order to collect material of the use of these prostheses, the authors are very keen to hear of drawbacks- and without reticence-as soon as possible. Publication of our own experience will follow this preliminary communication in due course.

Aluminum↗
PubMedDate not supplied

[Dimensional changes of polyethylene acetabuli in Müller's hip endoprosthesis. Report on measurement methods and their clinical significance].

The dimensional changes of hip sockets of total endoprosthesis of the Müller Type are subject of this article. Regular-anterior/posterior radiographs of the pelvis were taken to determine the orientation of the center of the prosthetic head in relation to the wire marker of the poly(ethylene) cup. Further measurements were done using casts of worn acetabular cups gained at revisional surgery. The possible errors of measurements of both methods are discussed. Both, creep and wear contribute to the dimensional changes of the hip sockets, the proportional amount of each mechanism is not known. Data from laboratory examinations suggest a relatively high rate of creep in the early time of function. With longer periods the dimensional changes are predominantly caused by wear. In the beginning of joint function our measurements show a high rate of the yearly dimensional change. The shift of the head amounted 0.5 mm per year and diminished after five years to rates of 0.15 to 0.2 mm. All dimensional changes that exceed a shift to the head of 0.2 mm per year are considered to be unfavourable and to contribute to loosening.

Hip Joint↗