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Biomedical subjects

H G Willert

Publications and source records attributed to H G Willert.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Exposure of surgical/orthopedic operating room personnel to monomer vapors during the use of bone cements--review of the literature and report of experiences].

PMMA bone cements are used for the fixation of artificial joint replacements. During their application in the operating theater, a small amount of the monomer evaporates. Operating room staff and surgeons are often not adequately informed about the negative properties and the effects on health of these vapours. Basic information about monomers and their toxicity, and safety regulations have been compiled. On the basis of present knowledge, the authors do not regard the repeated use of bone cement throughout the course of a day to represent a hazard to health.

Air Pollutants, Occupational↗
PubMed1992

Comparison of alumina-polyethylene and metal-polyethylene in clinical trials.

The dimensional changes of hip sockets of Müller-type total endoprostheses is the subject of this article. Regular anteroposterior roentgenographs of the pelvis were taken to determine the orientation of the center of the prosthetic head in relation to the wire marker of the polyethylene cup. Three different materials used for the femoral balls and matched with polyethylene as socket material were investigated, and the results of the displacement of the ball into the socket were compared. 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 first six months after implantation. With longer periods, the dimensional changes are predominately caused by wear. In the beginning of joint function, measurements show a high rate of the yearly dimensional changes. The head shifts up to 0.5 mm per year and diminishes after five years to rates of 0.1-0.2 mm, respectively. All dimensional changes that exceed a shift of the head of 0.2 mm per year are considered to be unfavorable and to contribute to loosening of the implants. Using metallic balls (Protasul-2), 64% had a wear rate of less than 0.2 mm; of those using Prostasul-10, 77% had lower rates than 0.2 mm. In patients where ceramic balls were implanted, the displacement rate was below 0.2 mm per year in 95%. Therefore, ceramic seems to be the most favorable material.

Aluminum Oxide↗
PubMed1990

Osteolysis in alloarthroplasty of the hip. The role of bone cement fragmentation.

Movement at the interface between bone and cement and fractures of the cement can cause fragmentation of the polymethylmethacrylate (PMMA) bone cement implant. In order to obtain further information about the effect of PMMA fragments on the surrounding tissue and the role of such particles in the development of bone resorption, the authors investigated 17 patients with cemented total hip endoprostheses showing osteolysis and implant loosening in the femoral shaft with (Group B) and without (Group A) involvement of the acetabulum. The roentgenographic follow-up examinations revealed an initially slow and later more rapid extension of the endosteal bone erosions, with a predilection for the tip of the stem, the lesser trochanter, and laterally for the middle of the stem. At revision surgery, tissue samples were taken from the joint capsule and the bone-cement interface, in particular from the osteolysis in the femoral shaft and the acetabulum. The tissue samples were processed for histology, microscopically examined, and semiquantitatively evaluated. The retrieved devices were also carefully inspected. Large foreign-body granulomas were found at the bone-cement interface and in the joint capsule. Histiocytes and foreign-body giant cells stored particles of PMMA and polyethylene, of which fragmented bone cement predominated. Granulomatous tissue invaded bone canals and marrow spaces and induced resorption of the surrounding bone. In four cases in Group A, tissue from the osteolysis contained only fragmented bone cement, demonstrating that PMMA particles alone may be responsible for triggering focal bone resorption. Osteolysis seems to begin at the site where disintegration of bone cement begins. In cases in which polyethylene particles were found in the tissue in addition to fragmented bone cement, wear from the ultrahigh molecular weight polyethylene socket has been increased by entrapment of PMMA particles between the joint surfaces. Thus, fragmentation of bone cement and abrasion of polyethylene enhance each other. Bone cement particles promote polyethylene wear, which in turn promotes granuloma formation, bone resorption, and subsequent bone cement disintegration.

Acetabulum↗
PubMed1990

Osteolysis in alloarthroplasty of the hip. The role of ultra-high molecular weight polyethylene wear particles.

Massive localized osteolysis around artificial joints has been seen more frequently in the past few years. It is still not generally accepted that ultra-high molecular weight polyethylene (UHMWPE) wear particles can induce massive bone resorption, even distant from the joint. This article describes a series of eight soft-top prostheses with large UHMWPE ball heads that contributed to the erosion of surrounding bone. Roentgenographically, all of the cases showed a marked loss of proximal cortical bone, more or less combined with osteolysis, which was distal to the femoral shaft and deep into the acetabulum. In two cases, remodeling and resorption transformed the bone into a tumorlike appearance. Tissue samples from areas of osteolysis as well as from the joint capsule were taken at revision surgery, processed for histology, examined microscopically, and evaluated semiquantitatively. The retrieved devices were also carefully inspected. Large amounts of UHMWPE wear debris were found not only in the joint capsule but also in layers of granulomatous tissue from the acetabulum and femur, whereas metal particles and fragmented polymethylmethacrylate were either completely absent or occurred only in very small amounts. The results of this study demonstrate that UHMWPE wear products alone can cause massive osteolysis by triggering foreign-body granuloma formation at the bone-cement interface; the bone cement may remain fixed in areas beyond the osteolytic transformation.

Acetabulum↗
PubMed1989

[The significance of wear and material fatigue in loosening of hip prostheses].

Particles created by wear and disintegration of implant materials give rise to foreign body reactions in the tissue surrounding joint endoprostheses. Histiocytes and foreign body giant cells phagocytize the particles released and form granulomas, which lead in turn to remodelling and resorption of the bone at the interface between implant and bone. As a consequence of this, osteolysis develops, which may lead to loosening and complete failure of fixation of the implant. Radiographically, the areas of osteolysis appear as localized, round, oval or oblong scalloping defects or as radiolucent lines in the endosteal sections of the bone immediately adjacent to the implants. This paper reports on 21 hip joint endoprostheses in which polyethylene and bone cement particles induced large areas of osteolysis at the bone/cement interface. In 8 cases the polyethylene particles originated from the convex joint surfaces of ball heads in "soft-top" endoprostheses (with or without simultaneous replacement of the acetabulum by a metal cup), and in 5 cases they originated from the anchoring surfaces of non-cemented cone-shaped screw-in sockets (Endler type); osteolysis and loosening of these endoprostheses appeared on average 48.2 and 76.6 months after implantation, respectively. The bone cement fragments came from the bone cement mantle of the femur, which had become fractured, disrupted and crushed, in 8 cases of total hip replacement with cemented prostheses; osteolysis appeared on average 87 months after primary implantation in these cases. Tissue samples taken at revision surgery from the joint capsule, the bone/cement interface and the osteolytic areas were processed into histological sections for microscopy and examined in the usual way. The type and amount of phagocytized material were subjected to semiquantitative analysis. We were able to show that osteolysis at the bone/cement interface can be induced by foreign body reactions to abraded polyethylene particles alone as well as by reactions to fragmented bone cement. The morphology of the tissue reaction to particles of the different materials is quite similar. The effect of the foreign body granulomas depends less on the type of the polymer than on the amount of abrasion and fragmentation products released into the surrounding tissue. This again proves that the life-time of joint endoprostheses depends essentially on factors influencing the wear rate. Polymer materials, with low wear resistance, are unsuitable for convex joint surfaces and for direct fixation to bone.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetabulum↗
PubMed1987

[Morphology of the implant site in cemented and uncemented joint implants].

After the insertion of a joint endoprosthesis a healing process is initiated which is comparable to the fracture healing. Thus, a border zone is built up against the implant, being composed of lining cells, connective tissue, vessels, bone marrow and bone. The bone of the implant bed is subjected to a remodeling in order to adapt its structure to the change of the biomechanic stresses. The tissue of the implant bed may react to infection, degradation or wear of the materials and mechanical instability of the fixation as well. The characteristic feature of this reaction is cell and tissue proliferation which causes bone resorption and, possibly, loosening of the implant.

Biomechanical Phenomena↗
PubMed1986

[Cementless implantation of Zweymueller-Endler total endoprosthesis of the hip. Clinical, radiologic and scintigraphic follow-up of 2 years].

Sixty-four patients with cementless Zweymueller-Endler total endoprostheses of the hip underwent follow-up postoperatively for 2 years. In 3 patients loosening or infection occurred. In 61 patients no complications were observed. However, in 74% of these patients increasing activity uptake at the tip of the shaft was found by scintigraphy. This was associated with hypertrophy of the corticalis and/or with a marrow cavity reaction, observed radiologically. The results show that scintigraphic evaluation of cementlessly implanted Zweymueller-Endler endoprostheses of the hip must be interpreted differently compared to isoelastic or to cemented prostheses.

Adult↗
PubMed1985

Local therapy of rhabdomyosarcoma, osteosarcoma and Ewing's sarcoma of children and adolescents.

Local control of the primary tumour is a fundamental requirement for clinical cure. Towards this aim, the primary tumour must be diagnosed early and identified histologically. The size, extension, and spread within the patient must be defined precisely. In planning effective local therapy, additional questions must be answered including resectability, mutilation, sensitivity to radio- and chemotherapy, anticipated morbidity from therapeutic measures, etc. For osteosarcoma there is no reasonable alternative to radical surgery. Because of the 20% local recurrence rate of Ewing's sarcoma following radiotherapy, radical surgical removal of the primary tumour should be attempted whenever possible. For rhabdomyosarcoma, particularly for its embryonal histology, non-radical removal of the primary sarcoma is still compatible with a cure, provided adequate radio- and chemotherapy is also administered. Primary irradiation is indicated in radiosensitive unresectable primary tumours and may convert these into an operable state. Chemotherapy is the domain of prevention and treatment of metastatic disease. It has, however, also a proved effect on primary tumours and, in several recent protocols, precedes local therapy.

Adolescent↗
PubMed1983

Orthopaedic surgery in hemophilic patients.

Since 1970 we performed 18 operations in hemophilic patients: 7 synovectomies, 2 elongations of the achilles-tendon, 1 hip arthrodesis, 2 endoprosthetic replacements of the hip, 2 intertrochanteric flexion- and varus-osteotomies, 1 excision of a pseudo-tumor and 2 removals of hematomas of the knee joint. The synovectomies were done only in joints affected by frequent hemorrhages. The bleeding frequency could be reduced considerably and the range of motion could be improved. The indication for several other orthopaedic procedures depended on the orthopaedic symptoms. The results were satisfactory without major complications during the healing period. During surgery and the following postoperative care the antihemophilic factor was substituted up to levels between 60 and 120%. The factor VIII or IX was controlled daily and Hb, GOT, GPT and the Australia antigen-antibody on a weekly base. The length of the substitution regimen was dependent on the individual wound healing and the postoperative treatment.

Adolescent↗
PubMed1980

Clinical experience with Mueller total hip endoprostheses of different design and material.

Patients of the Orthopaedic University Hospital in Frankfurt operated between 1970 and 1977 were examined to control the success of implantations of total hip endoprostheses. Ninety-three percent of totally 1497 implanted hip prostheses are Müller standard type, additionally there have been implanted 44 Weber-Huggler prostheses and 54 special long stem prostheses. During the follow-up period of 10 years 7.4% of the primarily implanted prostheses had to be revised. The reasons for revision were loosening of the stem and/or socket in 56% of the cases, 20% infections, 14% technical errors and in 11% of the cases fractures of the stem occured. Fifty-two percent of the implanted Weber-Huggler prostheses with rotational ball heads made of polyester had to be revised in the meantime, 78% of the cases because of loosening of the prosthetic components. It could be shown that the number of infected cases could be diminished after introduction of an ultraclean air operating box. The change of the cross section of the Müller-type-stem from a round medial wedge to a flat one and the introduction of CoNiCrMo wrought alloy Protasul-10 instead of CoCrMo cast alloy Protasul-2 as stem material in 1973 resulted in a much smaller rate of loosened prostheses without fractures of the forged Protasul-10 stems. During the 6 examined years there has been no fracture of a prosthetic stem made of Protasul-10.

Alloys↗