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Biomedical subjects

M A Ritter

Publications and source records attributed to M A Ritter.

At least 91 records · Page 5Linked to original sources
PubMed1997

Total hip arthroplasty in patients with osteonecrosis. The effect of cement techniques.

One hundred fifteen patients who underwent total hip replacement for osteonecrosis between June 1972 and April 1990 were divided into 3 groups according to the cause of the disorder: (1) osteonecrosis secondary to alcoholism (21 patients), (2) osteonecrosis secondary to hypersteroidism (29 patients), and (3) idiopathic osteonecrosis (65 patients). To determine the differences in short and long term arthroplasty failure rates, these 3 patient groups were compared with a group of 202 patients who received total hip replacement for osteoarthritis. Statistical analyses were carried out on the following definitions of failure: loosening of the acetabular component, loosening of the femoral component, and revision arthroplasty. Radiolucency and postoperative pain scores also were evaluated. A significant difference in the rate of failure because of loosening of the femoral component was found among the 4 groups. Likewise, a significant difference was found among the 4 groups in all revisions or loosenings or both. However, only the comparison between the idiopathic osteonecrosis and osteoarthritic groups showed a significant difference with survival analysis. Second generation cement technique was as significant as any variable relating to failure. The authors conclude that total hip arthroplasty is an equally viable treatment for the 3 types of osteonecrosis examined in this study; however, failure might be more imminent in studies where larger numbers are needed.

Aged↗
PubMed1997

Impaction bone-grafting before insertion of a femoral stem with cement in revision total hip arthroplasty. A minimum two-year follow-up study.

Impaction bone-grafting was performed before insertion of a collarless, polished, tapered femoral stem with cement in thirty-four revision total hip arthroplasties (thirty-four patients) that were done because of aseptic loosening. The average duration of follow-up was thirty months (range, twenty-four to forty-two months). The operation was the initial revision in twenty-eight patients (82 per cent). Twenty-two patients (65 per cent) also had revision of the acetabular component. Complications included four intraoperative and two postoperative fractures of the femur as well as one dislocation (at one month). Two patients (6 per cent) needed a repeat revision of the femoral stem because of aseptic loosening at twenty-six and thirty-six months postoperatively. Both of these patients had an associated fracture of the femur (one was intraoperative, and the other was postoperative). Subsidence was common (thirteen patients; 38 per cent) and averaged 10.1 millimeters (range, four to thirty-one millimeters). Although the study group was relatively small, with the numbers available subsidence was not found to be associated with the preoperative or postoperative hip score, segmental or cavitary femoral defects, femoral ectasia, intraoperative fracture of the femur, strut-grafting, trochanteric osteotomy, or varus position of the femoral component. Incorporation of the allograft into the trabecular bone and secondary remodeling were noted radiographically in thirty-two (94 per cent) and fourteen (41 per cent) of the patients, respectively, often within one year. Although the duration of follow-up was relatively short, no localized resorption of the allograft occurred and cortical repair was noted in one patient at three years. At the most recent follow-up evaluation, the Harris hip scores had improved from a preoperative average of 51 points (range, 32 to 90 points) to an average of 87 points (range, 65 to 100 points) and twenty-eight patients (82 per cent) had no or only slight pain. Despite the satisfactory early clinical results, we remain concerned about the high rate of fracture of the femur and the rate and extent of subsidence of the femoral component. On the basis of the worrisome findings after this two-year period, we recommend that impaction bone-grafting be used only when proximal femoral osteopenia is so severe that stability cannot be obtained with insertion of a long-stemmed femoral component without cement. In that setting, impaction bone-grafting may be considered instead of implantation of a massive proximal femoral allograft in combination with insertion of a femoral component with cement.

Adult↗
PubMed1997

Radiographic analysis of a cemented titanium alloy femoral component.

Proximal femoral cortical bone remodeling was evaluated radiographically about a 1 piece cemented titanium alloy femoral prosthesis implanted with modern cement techniques and was compared with one described previously in which early cement techniques and a stainless steel stem were used. Two hundred twenty-six total hip replacements (196 patients) were observed for an average of 6.3 years (range, 5-10 years). Analysis of all hips revealed that the ratio of cortical thickness to that of the overall femoral bone diameter did not change significantly about the periprosthetic bone throughout the length of the study. Cortical hypertrophy and atrophy occurred at rates similar to those seen with the early cement techniques. Distal fusiform cortical hypertrophy and the formation of osteosclerotic (reactive) lines at the bone cement interface occurred at approximately half the rate using modern cement techniques. In addition, cortical atrophy was associated with the formation of these reactive lines, the occurrence of osteolytic lesions, and progressive bone cement interface radiolucencies. Although periprosthetic cortical atrophy occurred at rates similar to those reported previously, important differences were noted between the findings of this study and the earlier study; these differences most likely were a result of cement technique or the prosthesis.

Aged↗
PubMed1997

Overview: maintaining outcomes for total hip arthroplasty. The past, present, and future.

Developing and maintaining outcomes for total hip arthroplasty, resulting in meaningful and usable data, presents many challenges for today's clinician. Outcomes data collected must show patients' clinical, functional, and overall quality of life status. Data also must be appropriate to illustrate efficiency, effectiveness, and value of medical interventions provided to payers. Previous and current measures of assessing outcomes of total hip arthroplasty are presented, evaluated, and discussed. Recommended standards for the future, including the identification of specific data needed such as demographics, Short Form-36, patient satisfaction, length of stay, infection rate, return to surgery, and revision rates are introduced, leading to an outcomes based suggested standard of care for total hip arthroplasty with application to patients, providers, and payers.

Arthroplasty, Replacement, Hip↗
PubMed1996

Patellofemoral complications following total knee arthroplasty. Effect of a lateral release and sacrifice of the superior lateral geniculate artery.

Between 1987 and 1989, 1,205 Anatomic Graduated Component (AGC, Biomet, Warsaw, IN) total knee arthroplasties were performed by three surgeons using the same prosthesis and same technique. Four hundred twenty-eight total knee arthroplasties (35%) had lateral releases; in 107 (75%) of these, the superior lateral geniculate artery was saved. Lateral release had no effect on patellar subluxation, dislocation, or loosening, but was associated with significantly more patellar fractures. Conversely, patellar radiolucency was more common in knees without a lateral release. Furthermore, saving the superior lateral geniculate artery during a lateral release had no effect on patellar dislocation, radiolucency, loosening, or fracture.

Aged↗
PubMed1996

Outcome of the contralateral hip following total hip arthroplasty for osteoarthritis.

One thousand one hundred and sixteen patients who underwent unilateral total hip arthroplasty osteoarthritis between 1970 and 1980 were examined for development, progression, and total hip arthroplasty in the contralateral joint. At the time of the original surgery, 452 patients were diagnosed with bilateral osteoarthritis and 664 had a normal contralateral hip. The probability of osteoarthritis progressing in the contralateral joint is 78.6% at 10 years, with the chance of arthroplasty being 53.8%. The probability of a hip diagnosed as normal developing osteoarthritis is 36.5% at 10 years, with an 8.3% chance of requiring total hip arthroplasty.

Adult↗
PubMed1996

Tibial shaft fracture following tibial tubercle osteotomy.

Tibial tubercle osteotomy has been reported to be an excellent exposure for a very stiff primary or revision knee requiring total knee arthroplasty. In 1993, the Center for Hip and Knee Surgery performed 657 primary and 16 revision total knee arthroplasties, using tibial tubercle osteotomy in 9 cases, 2 of which sustained tibial shaft fractures, because of which the Center's experience is reviewed.

Aged↗
PubMed1996

Differential expression of gp200-MR6 molecule in benign hyperplasia and down-regulation in invasive carcinoma of the breast.

In this study, we used immunohistochemical and biochemical analysis to show that gp200-MR6, a 200 kDa molecule that is functionally associated with the human interleukin 4 (IL-4) receptor complex, is expressed at high levels on normal breast epithelial tissues, at lower levels on in situ carcinomas, and that the expression is lost in the invasive carcinoma of the breast. Furthermore, a preliminary study showed that benign epithelial hyperplasia of the breast expresses the gp200-MR6 heterogeneously. Two populations of cells have been observed: MR6 positive and MR6 negative. Interestingly, MR6-positive cells were observed to have different morphology from those that were MR6 negative; the nuclei of the former were larger and rounded in shape, whereas the nuclei of the latter were relatively small and oval in shape. In sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting, monoclonal antibody MR6 detects the same molecular weight molecule in both normal and transformed tissue, indicating that the molecule is not a product of a truncated gene. The intensity of the gp200-MR6 bands correlates with the immunohistochemical data, indicating that the molecule is expressed at high levels in normal tissue and at lower levels in malignant tissue. These results suggest that analysis of gp200-MR6 expression may be useful in tumour grading and prognostic evaluation in breast cancer. Moreover, the molecule may be involved early in the process of tumorigenesis of the breast, in which a loss or a down-regulation of gp200-MR6 could contribute towards tumour development and progression via an effect on cell growth and differentiation.

Antigens, CD↗
PubMed1996

Bladder carcinomas and normal urothelium universally express gp200-MR6, a molecule functionally associated with the interleukin 4 receptor (CD 124).

Monoclonal antibody MR6 detects gp200-MR6, a molecule functionally associated with the interleukin 4 (IL- 4) receptor. Positive immunolabeling with MAb MR6 was obtained in 28/28 transitional cell carcinomas of the bladder, representing a range of different grades and stages of disease, as well as in all control non-neoplastic urothelia. The expression of mutant p53 protein and epidermal growth factor receptor was detected in 14/28 and 20/28 cases respectively. Proliferation indices, determined by Ki67 labeling, ranged from 5% to 95% among these tumours. The universal expression of gp200-MR6 in neoplastic and non-neoplastic urothelium has important implications for the possible use of IL-4 in tumour therapy and suggests that IL- 4 may play a role in differentiation and homeostasis of urothelium and other mucosal epithelia.

Antibodies, Monoclonal↗
PubMed1996

Enhanced in vivo immunogenicity induced by an antibody to the IL-4 receptor-associated gp200-MR6 molecule.

Four murine IgG1 monoclonal antibodies, each with specificity for a human tumour-associated antigen, have been tested for their in vivo immunogenicity using a rabbit model. Surprisingly, one of these antibodies, MR6, was significantly more immunogenic than the remaining three reagents. This enhanced MR6 immunogenicity was not restricted to the immunoglobulin molecule itself, but also applied to a hapten (fluorescein isothiocyanate, FITC) when conjugated to the monoclonal antibody. In addition, the secondary immune response to an independent antigen, human haemoglobin, was higher when the antigen was administered simultaneously with MR6 than when co-injected with an isotype-matched control monoclonal antibody. The presence of the target antigen, gp200-MR6, on both rabbit and human leucocytes and epithelium, and its known association with human IL-4 function, raises the possibility that antibody MR6 may not only target immunogens to antigen-presenting cells, but may also enhance the ability of these cells to present antigen to the immune system. Antibodies to the gp200-MR6 may therefore find important clinical application as in vivo adjuvants.

Animals↗
PubMed1996

Direct visualization of thymocyte apoptosis in neglect, acute and steady-state negative selection.

During thymocyte differentiation, the majority of the developing cells die in situ by apoptosis and are subsequently removed by macrophages. DNA fragmentation is one of the hallmarks of apoptosis and can be detected in situ by TdT-mediated dUTP-biotin nick end labeling (TUNEL). We used TUNEL combined with immunohistology to determine the sites of thymocyte apoptosis in mice transgenic for a TCR (F5) which recognizes a peptide (NP68) of the influenza virus nucleoprotein (NP) presented on the MHC class I H-2Db molecule. Apoptosis due to neglect was studied in F5 mice expressing a neutral MHC haplotype (F5/H-2q) and in beta 2-microglobulin-deficient F5 mice (F5/ beta 2m+). In both cases, the frequency of apoptotic cells was similar to that seen in F5/H-2b mice and non-transgenic C57BI/10 mice. Antigen-induced apoptosis was studied in F5 mice after i.p. Injection of the cognate NP68 peptide and in F5/NP double-transgenic mice. Three hours after peptide injection, apoptosis was high throughout the thymus cortex and clusters of apoptotic cells formed due to tissue macrophage uptake, whereas the thymic medulla remained unaffected. Massive recruitment of inflammatory cells into the thymus was seen as early as 1 h after peptide injection. Nine hours after peptide injection changes were apparent in the cortical epithelium and, by 4 days, the cortical network had collapsed to give scattered, compacted epithelial cells. In contrast, in F5/NP double-transgenic mice, thymocyte apoptosis induced by cognate self-peptide was localized at the cortico-medullary junction with little change seen in the epithelium of the cortex.

Animals↗
PubMed1996

Adjuvant radiation versus observation: a cost analysis of alternate management schemes in early-stage testicular seminoma.

PURPOSE: This study was designed to compare costs of adjuvant radiation versus observation in the management of early-stage testicular seminoma after inguinal orchiectomy. MATERIALS AND METHODS: A line-by-line inspection of the charges generated during a course of adjuvant pelvic and paraaortic radiotherapy and of three cycles of bleomycin, etoposide, and platinum salvage chemotherapy was performed for five patients who received irradiation and five patients who received salvage chemotherapy. The average charge for either treatment was then calculated. Only those charges directly associated with the diagnosis of seminoma were included in the analysis. Follow-up charges were also generated from the patients' billing records. The optimum follow-up regimen for either management option was derived from a synthesis of the international literature. A 5% rate of failure was assumed if adjuvant irradiation was administered, and a 15% rate of failure was assumed if observation was the option chosen. Charges were truncated at 5 years. RESULTS: The total charge generated over 5 years based on following a policy of observation is $27,223 per patient versus $19,557 if the option of adjuvant irradiation in chosen. Using University of Wisconsin institutional reimbursement rates, the estimated costs were $20,487 and $14,722 for the option of observation and adjuvant radiation, respectively. The cost equivalence point between the two options occurs at 2.5 years, when the initial cost of adjuvant radiotherapy is matched by the cost generated during the period of observation. The maximum cost difference is achieved by 5 years. CONCLUSION: Following a policy of observation postorchiectomy for early-stage testicular seminoma generates 39% more medical costs per patient over a 5-year follow-up period than does following the standard policy of adjuvant irradiation to the pelvic and paraaortic regions, with no reported difference in outcome.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

The effects of recombinant human erythropoietin on perioperative transfusion requirements in patients having a major orthopaedic operation. The American Erythropoietin Study Group.

Two hundred patients who were scheduled for a major elective orthopaedic operation were enrolled in a prospective study and were randomly assigned to one of three treatment groups. Group 1 consisted of sixty patients who received recombinant human erythropoietin, 300 international units per kilogram of body weight per day; Group 2, seventy-one patients who received recombinant human erythropoietin, 100 international units per kilogram of body weight per day; and Group 3, sixty-nine patients who received a placebo. A total of fifteen doses was given subcutaneously, beginning ten days before the operation and extending through the fourth postoperative day. Patients who declined or were unable to donate autologous blood preoperatively were included in the study and were maintained on iron supplementation orally. The decision to transfuse red blood cells depended on the physician, however, physicians were encouraged not to do so if the hematocrit was more than 0.27 (27 per cent), unless the clinical symptoms warranted it. Of the 185 patients who were evaluable with regard to efficacy, significantly fewer patients received homologous red-blood-cell transfusions in Groups 1 and 2 (17 per cent [nine] and 25 per cent [sixteen], respectively) than in Group 3 (54 per cent [thirty-six]) (p < 0.001). When the patients were stratified into two groups on the basis of the pre-treatment hemoglobin level (more than 100 to 130 grams per liter or more than 130 grams per liter), we found that patients who had received a placebo and had a baseline hemoglobin level of more than 100 to 130 grams per liter were at significantly higher risk for transfusion (78 per cent [twenty-one]) than those who had received a placebo and had a baseline level of more than 130 grams per liter (36 per cent [fourteen]). For patients who had a baseline hemoglobin level of more than 100 to 130 grams per liter, the higher dose of recombinant human erythropoietin appeared somewhat more effective than the lower dose, with 14 per cent (three) of the patients in Group 1 and 39 per cent (nine) in Group 2 needing a transfusion; however, the difference was not significant (p = 0.09). For patients who had a baseline hemoglobin level of more than 130 grams per liter, the two doses of recombinant human erythropoietin produced similar results, with 14 per cent (four) of the patients in Group 1 and 11 per cent (four) in Group 2 needing a transfusion; this was in contrast to a rate of transfusion of 36 per cent (fourteen) in Group 3 (the patients who received the placebo) (p = 0.03). The recombinant human erythropoietin was generally well tolerated, although one patient, who did not have a history of hypertension, had an increase in blood pressure, from a baseline level of 142/78 millimeters of mercury (18.93/10.40 kilopascals) to a level of 220/100 millimeters of mercury (29.33/13.33 kilopascals), after ten days of treatment with the higher dose. These data suggest that recombinant human erythropoietin, administered before and after major orthopaedic operations, can minimize the need for homologous red-blood-cell transfusion.

Aged↗
PubMed1996

Revision total joint arthroplasty: does medicare reimbursement justify time spent?

In 1991, five different total joint replacement surgeons performed 337 primary total knee replacements and 250 primary total hip replacements. They revised 25 total knee replacements and 73 total hip replacements. The average length of stay was 6.6 days for the primary total knee arthroplasty and 7.5 days for knee revisions. For total hip replacement, average stay was 5.9 days for primary surgery and 6 days for revisions. The operative time required for each of the five surgeons to complete a total knee replacement increased 55%, 3%, 38%, 72% and 38%; whereas for the total hip replacement, time increased 87%, 77%, 84% and 58%. Overall, there was a 41% increase in operating time for revision total knee replacements and a 77% increase for revision total hip replacement. Allowable charges by Medicare in 1993 for a primary knee and hip replacement were $1,298 and $1,363, respectively. Revision total knee replacement increased 24.3% ($1,613) and revision total hip replacement increased 30.8% ($1,782) in the state of Indiana. These figures do not encourage those surgeons who are capable of doing total joint replacements to revise other surgeons' problems.

Cost Savings↗