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Biomedical subjects

M A Ritter

Publications and source records attributed to M A Ritter.

At least 127 records · Page 7Linked to original sources
PubMed1995

The effect of heterotopic bone formation on prosthetic loosening after total hip replacement.

Seven hundred thirty-two total hip replacements performed from 1970 to 1980 were evaluated for the degree of heterotopic bone formation postoperatively and its effect on long-term mechanical loosening. There were 231 Charnley total hip replacements, of which 152 had no heterotopic bone formation, 58 had Grade 1 formation, and 21 had Grade 2 or 3 formation. Among the 123 Mueller total hip replacements, 98 had no heterotopic bone formation, 19 had Grade 1 formation, and 6 had Grade 2 or 3 formation. For the 378 T-28 total hip replacements, there were 305 with no heterotopic bone formation, 59 with Grade 1 formation, and 14 with Grade 2 or 3 formation. Survival analyses using the definition of failure as loosening, fracture, or revision of the acetabulum or femoral components were constructed. There was no correlation between mechanical loosening, fracture, or revision of the total hip replacement and any degree of heterotopic bone formation.

Arthritis, Rheumatoid↗
PubMed1995

Comparison of polyethylene wear in machined versus molded polyethylene.

Polyethylene wear debris has been identified as a cause of osteolysis, granuloma formation, and loosening in total hip arthroplasty. This study was designed to evaluate differences in polyethylene wear rates between acetabular cups machined from extruded bar stock and those direct compression molded. Two hundred thirty-six hip prostheses underwent radiographic evaluation using the technique of Livermore et al. Seventy-four were all-polyethylene cups machined from extruded bar stock, and 162 were all-polyethylene cups direct compression molded. Both groups were similar in that the acetabular and femoral components were all cemented, the acetabular components were all polyethylene, nonmetal backed, and bearing surfaces of both groups were polished, cobalt chrome. The femoral components were TRIAD in the machined group and TR28 in the molded group. Patient matching was performed, assigning 54 patients in each group, whose average age was 66 years old, average followup 6.7 years, and average weight 161 pounds. Rates of polyethylene wear then were compared. Results showed a linear wear rate of 0.05 mm per year for compression-molded polyethylene and 0.11 mm per year for machined polyethylene. Results of this study raise questions regarding the types of polyethylene fabrication and its ultimate molecular weight, and wear resistance.

Acetabulum↗
PubMed1995

Polyethylene wear in total hip arthroplasty.

Polyethylene wear increasingly has been blamed for osteolysis and granuloma formation after total joint arthroplasty. The authors evaluated the wear difference between bearing surfaces of stainless steel, cobalt chrome, and titanium alloy. They also compared cemented all-polyethylene molded cups with cemented metal-backed molded acetabular cups. These were compared with molded and machined polyethylene cups. Two patient groups were matched individually for gender, age, weight, and length of followup. Analyses were done using the technique of Livermore et al. The bearing surface evaluation consisted of 3 groups after matching, leaving 77 patients per group. Results showed linear wear rates of 0.06 mm per year, 0.05 mm per year, and 0.08 mm per year for stainless steel, cobalt chrome, and titanium alloy, respectively. The comparison between cemented molded metal-backed and nonmetal-backed acetabular components was not matched, with 134 metal-backed and 99 nonmetal-backed components. Results showed linear wear rates of 0.011 mm per year in the metal-backed group and 0.08 mm per year in the nonmetal-backed group. Results were statistically significant. These results indicate that the metal composition of the femoral bearing surface has minimal, if any, effect on the linear polyethylene wear rate. The method of polyethylene fabrication and the use of metal backing had a significant effect on the polyethylene wear rate in these patient groups. These results suggest that the compression-molded all-polyethylene acetabular component may be optimal for reducing polyethylene wear in total hip arthroplasty.

Aged↗
PubMed1994

Tumor cell kinetics in mixed populations.

The delayed biopsy, relative movement method provides a rapid estimate of in situ potential doubling times in human tumors. The accuracy of the estimate, however, can be adversely influenced by normal diploid cells that are present in tumor biopsy specimens and have DNA profiles that overlap their tumor cell counterparts. Interference with the measurement of tumor cell kinetic parameters can result, the magnitude of which depends upon the DNA index and the proportion and labeling index of these normal cells. Two approaches that address this problem were explored in vitro: (1) A normal cell subtraction method was developed in which adjacent normal tissue and tumor are biopsied concurrently and are separately processed for flow cytometric analysis. Results are integrated to allow an approximate correction for the normal, diploid population's perturbation of the measurement of tumor labeling index and relative movement. This approach was examined in this present study through extensive testing in mixtures of various proportions of two in vitro cell lines. (2) The percent S phase method, developed by Durand, was examined in these same population mixtures, as well as separately in each population. Both methods provide reliable estimates of kinetics in mixed in vitro populations. The relative advantages and disadvantages of each, as well as the potential limitations if extended to in vivo measurements, are discussed.

Aneuploidy↗
PubMed1994

Tumor cell kinetics using two labels and flow cytometry.

A flow cytometry based, single sampling method employing sequential bromodeoxyuridine (BrdUrd) and iododeoxyuridine (IdUrd) labeling with an intervening interval is examined. BrdUrd-specific and nonspecific monoclonal antibodies and flow cytometry are used to estimate the duration of DNA synthesis and the potential doubling time in tumor cell populations using a single sampling or biopsy. A correction for labeled, divided cells allows postlabel incubation intervals to exceed the length of the G2/M phase of the cell cycle. The method yields reliable results when tested in experimental tumor systems in vitro and in situ, as well as in nine human tumors labeled in situ. It uses a somewhat simpler analysis than the alternative relative movement method, requiring only labeling indices, rather than both a labeling index and relative movement, but doses require the administration of two, rather than one, label. It provides an independent verification of and a useful single sampling alternative to the relative movement method for the estimation of the length of S phase and, from this, the potential doubling time in experimental or clinical human tumors.

Animals↗
PubMed1994

Kinetics of cell labeling and thymidine replacement after continuous infusion of halogenated pyrimidines in vivo.

PURPOSE: Iododeoxyuridine (IdUrd) is a halogenated pyrimidine which has been recognized as a clinical radiosensitizer. It is generally agreed that the extent of radiosensitization correlates with the degree of thymidine substitution in DNA. Controversy exists regarding the optimal administration schedule to achieve maximum radiosensitization. To obtain more information relating to this problem, we present experiments on an in vivo human tumor xenograft continuously exposed to a fixed serum concentration of halogenated pyrimidines so as to study the kinetics of cell labeling and thymidine replacement. METHODS AND MATERIALS: Human colon tumor (HCT-116) cells were injected subcutaneously into nude mice. After 10 days, most animals (> 90%) developed measurable tumor nodules with a volume doubling time of 5 +/- 1 days. Once the tumors reached a cross-sectional area of 0.25-0.30 cm2, miniosmotic pumps were implanted to deliver a dose of 100 mg/kg/day of IdUrd by continuous infusion. After an IdUrd exposure time of 1-7 days, blood and tumor tissue were collected. RESULTS: The steady state serum IdUrd concentration was 0.95 +/- 0.1 microM, which is a clinically relevant concentration for a prolonged continuous intravenous infusion. The tumor cell potential doubling time (Tpot) was 25 +/- 2 h. The percent IdUrd thymidine replacement and the fraction of cells labeled, followed exponential saturation kinetics with a halflife of 33 +/- 9 and 27 +/- 2 h, respectively. After 5 days of exposure (congruent to 5 x Tpot), the thymidine replacement in tumor cells was 2.0 +/- 0.2% and the fraction of tumor cells labeled was 94 +/- 1%. Immunohistochemical staining of IdUrd labeled tumor tissues showed an exposure dependent gradient of cellular labeling that was initially highest in regions close to blood vessels. After 4 days of exposure at 100 mg/kg/day, there was an increase in the fraction of cells in G(0) + G1 and a decrease in the S phase population, suggesting a block between G1 and S phase. CONCLUSION: We conclude that the in vivo kinetics of IdUrd thymidine replacement and fraction of cells labeled after continuous exposure followed exponential saturation kinetics with a halflife of approximately the potential doubling time of the tumor cell population. Simple modeling suggests that some form of prolonged, or briefly interrupted, continuous infusion should be considered for clinical administration because such schedules would leave fewer cells unsensitized than shorter infusions would. Even 10% of unlabeled clonogenic cells could explain the lack of dramatic clinical successes with IdUrd or BrdUrd sensitization.

Animals↗
PubMed1994

Long-term outcomes of contralateral knees after unilateral total knee arthroplasty for osteoarthritis.

One hundred fifty-six patients who underwent unilateral total knee arthroplasty (TKA) between 1970 and 1985 were evaluated for the development, progression, and eventual TKA in the contralateral knee. At the time of TKA, 113 patients were diagnosed with osteoarthritis in the opposite knee, while in the remaining patients, the opposite knee was normal. The probability of the normal knee developing osteoarthritis and requiring a TKA at 7 years is 21 and 5%, respectively. The chance of a knee diagnosed as osteoarthritic at the time of surgery needing a TKA at 10 years is 37%.

Aged↗
PubMed1994

Clinical and radiographic evaluation of long-stem femoral components following revision total hip arthroplasty.

Fifty-four consecutive, long-stem revision hip arthroplasties were performed in 53 patients. In order to evaluate periprosthetic femoral changes, all cases utilizing cement, requiring bone-grafts for prosthetic stability, or with a follow-up period of less than 2 years were omitted. Thus, 32 long-stem revision hip arthroplasties in 32 patients were reviewed. Twenty-three Porous Coated Anatomic (Howmedica, Rutherford, NJ) and nine Bi-Metric (Biomet, Warsaw, IN) stems were implanted, with an average follow-up period of 3.6 years (range, 2-6 years). Prosthetic canal fill averaged 94% proximally and 80% distally. Intraoperative complications included three femoral shaft fractures. Harris hip scores averaged 47.8 points, before surgery and 87.6 points at the final follow-up evaluation, with 81% of patients the pain-free. Only three cases of subsidence and one case of osteolysis were noted. By 1 year, proximal osteopenia (off-load) (P = .005), bony condensation about the porous surface (spot weld) (P = .01), and pedestal formation (P = .004) were observed. The presence of distal cortical hypertrophy, (P = .02) spot weld (P = .001), and pedestal formation (P = .05) correlated significantly with off-load. Pedestal formation and distal cortical hypertrophy were commonly found together (P = .001). Despite significant periprosthetic remodeling, adequate fixation and satisfactory early clinical scores were achieved in this setting. Contrary to similar reviews using extensive bone-grafts, acceptable pain-free clinical results were obtained with these components.

Female↗
PubMed1994

Measurement of polyethylene thickness in total hip arthroplasty. A technique analysis.

Accurate radiographic measurement techniques are necessary to evaluate wear characteristics of different metals, ceramics, and plastics. This study evaluated a standard technique for radiographic measurement of acetabular component thickness. Twenty-one acetabular components retrieved after revision surgery were studied. Radiographic measurement of polyethylene thickness was performed at two points on radiographs taken within 2 months of the revision surgery. Measurements were made at the area of greatest polyethylene wear and at the center of the component, and these measurements were compared to direct measurement of the retrieved component. The 42 data points obtained revealed an average difference between the radiographic and direct measurements of 0.18 mm. A regression model demonstrated no significant difference (P = .85) between these measurements. Additionally, when comparing the central-point measurement to the thinnest wear-point measurement, no difference was noted, indicating that wear in the sagittal plane did not affect radiographic measurement accuracy. Radiographic measurement of acetabular component thickness is accurate to within 0.18 mm. This degree of accuracy allows for radiographic wear analysis, as long as the standard measurement technique is utilized.

Hip Prosthesis↗
PubMed1994

Sequelae of definitive radiation therapy for prostate cancer localized to the pelvis.

OBJECTIVES: To evaluate sequelae and estimate quality of life utilizing a survey instrument in 133 consecutive patients who have undergone definitive radiation therapy for localized prostate cancer. METHODS: All patients reported on have been followed for 14 to 60 months (median, 31 months) after radiation therapy and only patients with definitive prostate radiation therapy are included. Of the patients still alive at time of follow-up, 115 were mailed the questionnaire. Data regarding tumor grade and stage as well as treatment were extracted from patient files. RESULTS: Of the 91% of patients who returned the questionnaire, 11% used a pad and 13% leaked more than a few drops of urine daily. Of all the respondents, 9% stated that incontinence was a problem, and 31% found urinary leaking significantly worsened after radiation therapy compared with before their diagnosis of prostate cancer. With respect to sexual function, 77% recalled being able to have full or partial erections prior to radiation therapy. At some time after radiation therapy, 22% of previously potent respondents were able to have a full erection and 41% were able to have a partial erection. Twenty-nine percent of all patients who were able to establish an erection prior to radiation therapy reported that impotence was a problem at the time of follow-up. Forty-nine percent of patients had abdominal pain, diarrhea, or abdominal cramping during or after radiation therapy and 31% of all patients still had some intestinal symptoms at the time of follow-up. Eighteen percent of all patients were significantly bothered by one or more of these bowel problems. Overall, 31% of all patients reported a persistent degree of physical discomfort that they believed was secondary to their prostate cancer or the effect of treatment. Eighty-one percent were satisfied with radiation therapy and 97% of the patients said they would have radiation therapy again if faced with the decision. CONCLUSIONS: Utilizing a sensitive questionnaire on patients who had definitive radiation therapy for prostate cancer, we found the incidence of patients bothered by incontinence to be surprisingly frequent and higher than previously reported. The frequency of impotence is similar to previous studies. However, when our incontinence and impotence data were compared to Medicare patients who had undergone radical prostatectomy, the frequencies after radiation therapy were significantly lower. Despite the rates of sequelae, the patients were generally satisfied with the decision to undergo radiation therapy and with the medical treatment received.

Aged↗
PubMed1994

Identification of glioma-associated antigen MUC 2-63 as CD44.

Monoclonal antibody MUC 2-63 recognises neurogenic tumours and has been used successfully for radioimaging human malignant gliomas. We now show that the MUC 2-63 antigen has the same tissue distribution and molecular weight range as the CD44 antigen and confirm the identity of these two molecules in blocking studies using MUC 2-63 and the CD44 anti-framework antibody F10-44-2. Thus not only MUC 2-63 but also other anti-CD44 monoclonal antibodies should prove useful in imaging and, perhaps, therapy of brain tumours.

Antibodies↗
PubMed1994

Inhibition of alloreactivity by mAb MR6: differential effects on IL-2- and IL-4- producing human T cells.

mAb MR6 has previously been shown to block both IL-4-induced T cell proliferation and IL-4-dependent IgE production, suggesting a functional association between the antigen detected by MR6 (gp200-MR6) and the human IL-4 receptor. In this study the potential modulatory effects of mAb MR6 on IL-4 function have been further analysed in alloantigen-specific assays for cytotoxic and Th cell maturation, mature cytotoxic T cell killing, helper cell proliferation, and generation of IL-2- and IL-4-producing Th cells in a mixed lymphocyte reaction (MLR). Our data show that mAb MR6 has an inhibitory effect on both clonal expansion and maturation of cytotoxic T lymphocyte precursors within the alloreactive T cell population. mAb MR6 had no effect on the maturation of Th lymphocyte precursors (assayed by IL-2 production). However, this mAb had striking differential effects on cytokine production in MLR cultures, showing total ablation of IL-4 but no alteration of IL-2 levels in the supernatant medium. The absence of IL-4 from culture supernatants could be due to the fact that mAb MR6 is blocking cytokine production, that it is speeding up IL-4 internalization and utilization or that it inhibits the expansion of the T cell subset(s) that secretes IL-4. The data demonstrate that the action of mAb MR6 is focused on the IL-4-producing population and raise the possibility that gp200-MR6 may play an important role in this aspect of IL-4 function.

Antibodies, Monoclonal↗
PubMed1994

Differential expression of adhesion molecules within the human thymus.

Development of a diverse, MHC-restricted yet self-tolerant T-cell repertoire occurs within the thymus, and requires contact between developing T cells and their stromal microenvironment. Such interactions are likely to depend on the combinatorial effect of specific adhesion molecules. As a preliminary step to determining their role in T-cell development, we have studied the distribution of LFA-1/ICAM-1, CD2/LFA-3, VLA-4/VCAM-1, and HECA 452-antigen/E-Selectin ligand pairs on frozen sections of human thymus. Using two color-immunohistochemistry, and a variety of cell-lineage markers that reveal the nature of the cells on which these adhesion molecules are located, we find a differential distribution of adhesion molecules, with some being shared by both endothelial and epithelial cells. We also identify the VCAM-1-positive subpopulation as cortical macrophages. The relevance of these findings to thymopoiesis is discussed.

Cell Adhesion Molecules↗
PubMed1994

Closed wound drainage in total hip or total knee replacement. A prospective, randomized study.

We prospectively randomized 415 total joint replacements for either a closed wound-drainage system or no postoperative drainage. Drainage was not used in 200 total joint replacements, of which 138 were total knee replacements and sixty-two, total hip replacements. Drainage was used in 215 total joint replacements, of which 137 were total knee replacements and seventy-eight, total hip replacements. All patients were evaluated for the presence of excessive postoperative drainage that necessitated cessation of the range-of-motion exercises, the amount of transfused blood (homologous and autologous), and the preoperative and postoperative hemoglobin levels. The range of motion was assessed daily in the patients who had a total knee replacement. No statistical difference was found in the number of patients who had excessive postoperative drainage from a drained or non-drained wound. There was also no statistical difference with respect to the amount of transfused blood and the preoperative and postoperative hemoglobin levels. Furthermore, in the patients who had a total knee replacement, there were no statistical differences between drained and non-drained wounds with respect to the daily range of motion during the first seven days postoperatively. The mean amount of blood transfused was 157 milliliters in the total knee replacements with drains, 160 milliliters in the total knee replacements without drains, 188 milliliters in the total hip replacements with drains, and ninety-three milliliters in the total hip replacements without drains.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Transfusion↗
PubMed1994

Radiolucency at the bone-cement interface in total knee replacement. The effects of bone-surface preparation and cement technique.

Three hundred and sixty-three knees (221 patients) that had been treated with total arthroplasty between 1975 and 1985 were divided into three groups on the basis of the preparation of the surface of the bone and the technique of the cement application. Group 1 (155 knees) was treated with irrigation of the bone surfaces with a syringe and manual packing of the bone cement. Group 2 (sixty-one knees) had high-volume, high-pressure lavage of the bone surfaces and manual packing of the cement. Group 3 (147 knees) had high-volume, high-pressure lavage and pressure injection of low-viscosity methylmethacrylate cement. Radiolucency was evaluated at each follow-up interval, and the findings were subjected to chi-square analysis and Kaplan-Meier survival analysis. Chi-square analysis of the data at one and three years indicated a significantly higher frequency of lines at the bone-cement interface in the femur and tibia in Group-1 knees compared with those in Groups 2 and 3. The survival curves showed increasing rates of radiolucency adjacent to the tibial components of the knees that had been prepared with lavage that was not high-volume and high-pressure and that had been prepared with finger-packing of cement (Group 1). This may partially explain the clinical problem of loosening of tibial components despite acceptable alignment. This study demonstrates that proper preparation of the cancellous bone and pressurization of the cement reduce the initial occurrence of a radiolucent line, which may have a positive effect on the ultimate failure of at least the tibial component.

Aged↗
PubMed1994

A new radiographic evaluation of primary osteoarthritis.

Two thousand five hip radiographs, both AP and lateral, were evaluated for osteoarthritis. We excluded all cases of traumatic osteoarthritis, rheumatoid arthritis, avascular necrosis, and congenital deformities. This left 1578 hips in 1309 patients, which were sub-divided into three categories: medial osteoarthritis (405 hips, 20% of which were bilateral, 68% women, 32% men); superior lateral osteoarthritis (934 hips, 19% of which were bilateral, 49% men, 51% women); and global osteoarthritis (239 hips, 23% bilateral, 53% men, 47% women). These categories may have significance in operative technique and survival of acetabular cups after total hip arthroplasty.

Adult↗