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Biomedical subjects

R Poss

Publications and source records attributed to R Poss.

83 records · Page 5Linked to original sources
PubMed1979

Methylmethacrylate is a mutagen for Salmonella typhimurium.

The long-term effects of exposure to monomeric methylmethacrylate have yet to be established. We have measured the toxicity and mutagenicity of methylmethacrylate for Salmonella typhimurium. At levels of thirty-four millimolar, methylmethacrylate exhibited 28 per cent of the mutagenic activity of an equimolar dose of dimethylnitrosamine. Methylmethacrylate alone exhibited toxicity to the bacteria, but when the methylmethacrylate was incubated with a rat-liver enzyme metabolizing system, mutagenesis was induced. These findings suggest that an intermediate metabolite of methylmethacrylate is mutagenic to Salmonella typhimurium.

Adhesives↗
PubMed1976

Complications of total hip-replacement arthorplasty in patients with rheumatoid arthritis.

During the period 1969 through 1974, 716 total hip-replacement arthorplasties were performed. The results of the surgery in 275 cases of rheumatoid arthritis as regards complications were compared with those in 382 procedures in cases of osteoarthritis. In contrast to the reports of others,the incidence of deep would infection in the two groups was found to be equal. Patients undergoing total hip-replacement arthroplasty as a revision of a previous operation had a substantially increased risk of infection. Patients with rheumatoid arthritis, however, were more subject to certain other complication (intraoperative fracture, difficulties with anesthesia, and malposition of prosthetic components), in addition to the complications that were predictable because of the involvement of multiple joints and the systemic disease process.

Adult↗
PubMedDate not supplied

Red cell transfusions in total knee and total hip replacement surgery.

To explore how red cell transfusions were used to support patients who underwent primary and revision hip and knee replacements classified within diagnosis-related group (DRG) 209 (major joint and limb reattachment procedures), we studied abstracted patient discharge records from 151 United States hospitals in 1986. A total of 9684 units of whole blood and/or separated red cells was used to support 6472 patients. The transfusion use varied by surgical procedure, with patient gender as an influencing factor. Large proportions of patients underwent surgery without requiring transfusion. Among transfused patients, the majority received 1 to 3 units of red cells; however, a minority of patients required multiple transfusions, thereby utilizing a disproportionate share of the blood resource. Comparison of transfusion practice within the seven most active hospitals revealed significant differences (p less than or equal to 0.01) in the percentage of patients actually transfused, but not in the mean number of units of red cell components transfused per transfused patient. Similar findings emerged from comparison of transfusion practice when all hospitals were segregated into five hospital classes on the basis of orthopedic surgical service activity. These effects were seen for both total knee and total hip replacement procedures. It can be concluded that the lack of clearly defined criteria for transfusion contributed to the variations observed.

Blood Transfusion↗
PubMedDate not supplied

Six- to 11-year results of total hip arthroplasty in rheumatoid arthritis.

The results of 138 total hip arthroplasties in 98 rheumatoid arthritic patients were reviewed six to 11 years (mean, 7.0 years) after operation. While 96% of the patients were clinically improved as a result of surgery, radiographic analysis suggests that, despite their low functional requirements, this group of patients experiences mechanical loosening and failure with time. Improvements in prosthetic design and cementing technique should contribute to a lowered incidence of mechanical failure in the future. In addition to improvements in technology, the failure rate can be further diminished by recognition of the systemic problems associated with rheumatoid arthritis, e.g., high incidence of infection, osteopenia, and sequelae of multiple joint involvement. In reconstruction of the acetabulum, especially in the presence of protrusio, failure to restore the anatomic position and orientation of the acetabulum predisposes to loosening and migration.

Arthritis, Rheumatoid↗
PubMedDate not supplied

Factors influencing the incidence and outcome of infection following total joint arthroplasty.

During a ten-year period, 4240 total hip, knee, and elbow arthroplasties were performed. The overall infection rate was 1.25%. Certain groups were identified as being at higher risk of infection following total joint arthroplasty: rheumatoid arthritics were at 2.6 times greater risk than osteoarthritics; patients undergoing total hip arthroplasty as a revision of a previous operation were eight times more likely to have infection than those undergoing a primary operation; and patients with metal-to-metal hinged knee prostheses, when compared with patients with metal-to-plastic knee prostheses, were 20 times more likely to have infection. The majority of infections could be attributed either to perioperative problems or late bacterial seeding from a distant site. Although most infections occurred by two years after operation, late infections, particularly in rheumatoid patients via the hematogenous route, occurred as long as nine years after operation. There was no correlation between the Gram's-staining characteristics of the pathogen and the outcome of the infected joint. Gram-negative organisms were frequent in the perioperative period and reflected either nosocomial infection or the ineffectiveness of the prophylactic antibiotic regimen used in inhibiting gram-negative pathogens. The major factors that influenced the outcome of the infected joint included the interval from the initial surgery to recognition of infection, the delay in institution of appropriate treatment, the particular joint that was infected, the integrity of the bone-cement interface, the type of prosthesis used, and the host susceptibility. Identification of high-risk groups and the recognition that patients with joint implants are at risk of infection at any time in the postoperative period may lead to a lowered infection rate in the future.

Aged↗
PubMedDate not supplied

Mechanics of the normal and osteoarthritic hip. A new perspective.

The mechanism of force transmission in normal and osteoarthritic human hips is interpreted with the aid of the following hypothesis: the essential anatomic requisite for the maintenance of mechanical equilibrium about the hip is a horizontal acetabular weight-bearing surface. Anatomic deviations from this norm result in a disequilibrium of opposing vector forces and may be contributory to the eventual onset of osteoarthritis (OA). The radiographic anatomy of the hip is the temporal record of the biologic response of bone to load transmission. From the analysis of radiographs the magnitude and direction of mechanical forces about the hip can be inferred. Deviations from normal, as in OA, can be understood by such radiographic analyses.

Adult↗
PubMedDate not supplied

Hip cartilage supported by methacrylate in canine arthroplasty.

A theoretically attractive approach to femoral head arthroplasty would be the preservation of a"biologic" bearing surface composed of autogenous articular cartilage and subchondral bone, supported by a prosthetic material with mechanical properties similar to those of trabecular bone. The substitution of such a material for bone would preclude incomplete revascularization of the femoral head and eventual bony collapse. The advantages of preserving the patient's hip joint, even in the face of a fracture that has caused the loss of vascular supply to the femoral head, are self-evident. To test this hypothesis, seven dogs underwent hip arthroplasty, whereby the trabecular bone of the femoral head was replaced with polymethylmethacrylate. When killed 2 1/2 years after operation all of the dogs demonstrated injury or loss of articular cartilage in the superior aspect of the femoral head. The lesions are consistent with advanced osteoarthritis by gross and histologic examination. These lesions apparently were produced by changing either the geometry or stiffness, or both, of the material supporting the articular cartilage. Supporting human articular cartilage with methacrylate for joint arthroplasty is not recommended.

Animals↗
PubMedDate not supplied

Bilateral total hip and knee replacement in adults with rheumatoid arthritis: an evaluation of function.

Sixteen patients with advanced rheumatoid arthritis who underwent total joint replacements of both hips and both knees were followed for an average of 22.8 months postoperatively. Their functional status before and after surgery was assessed by use of a special rating system for function. Fourteen of the 16 patients demonstrated higher total function scores at follow-up. Improvement was most marked in walking endurance, need for walking aids, and ability to climb stairs. Factors which were believed to predispose to less functional improvement included older age at initial surgery, longer duration of disease, more severe upper extremity involvement, and more frequent medical illnesses. There were 8 patients in whom combined hip and knee flexion in one or both lower extremities did not exceed 190 degrees after surgery. When this deficiency was combined with severe involvement of the upper extremities, difficulty with activities such as climbing stairs and arising from a chair was more common. Therefore, the goal of surgical treatment is to provide combined hip and knee flexion in excess of 190 degrees in these patients. Total joint arthroplasty has increased the likelihood of functional improvement in patients with severe rheumatoid arthritis involving the hips and knees, and encouraged the surgeon to operate earlier in the course of the disease as well as on patients with severely deformed joints.

Adult↗