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Biomedical subjects

C L Nelson

Publications and source records attributed to C L Nelson.

At least 55 records · Page 3Linked to original sources
PubMed1995

Minimal femoral cortical thickness necessary to prevent perforation by ultrasonic tools in joint revision surgery.

Ultrasonic tools are effective in removing cement in revision surgery and almost eliminate perforation of the femoral shaft, a dangerous complication associated with cement removal using drills, chisels, osteotomes, and other tools. Clinically, the ultrasonic tool used to remove cement could not be passed through a relatively normal femoral cortex; however, a perforation occurred in a patient with a femoral cortex less than 1 mm thick. The purpose of this study was to determine how thin the femoral cortex can be and yet allow the safe use of ultrasonic tools to remove cement without the risk of perforation. A cement mantle was constructed in the intramedullary canal of human cadaver femurs. Each specimen was mounted on a jig, which was then fastened to a Materials Testing System (Minneapolis, MN). The average load generated across the cortex by the ultrasonic tools while removing cement was measured. Loads of varying magnitudes were then applied by the ultrasonic tools to femoral cortices of varying thickness. When the cortex measured 3 mm thick, perforation did not occur. When the cortex measured 2 mm, perforation was possible but required loads three to six times greater than those normally used to remove cement.

Bone Cements↗
PubMed1995

Role of the accessory gene regulator (agr) in pathogenesis of staphylococcal osteomyelitis.

To examine the role of the accessory gene regulator (agr) in staphylococcal osteomyelitis, we compared a Staphylococcus aureus osteomyelitis isolate (UAMS-1) with a derivative of the same strain (UAMS-4) carrying an inactivated agr locus. Virulence was assessed with a rabbit model of acute, exogenous osteomyelitis. Bacteria were delivered by microinjection into the midradial region of the forelimb. After 4 weeks, UAMS-1 was identified in the bone of 12 of 13 rabbits infected with > or = 2 x 10(6) CFU and 5 of 6 infected with < or = 2 x 10(5) CFU. In contrast, UAMS-4 was found in 6 of 13 infected with the higher dose and 1 of 6 infected with the lower dose. Additionally, on the basis of a five-point scale assessing radiographic evidence of disease, rabbits infected with UAMS-1 had average scores of 2.64 +/- 0.30 (high dose) and 1.43 +/- 0.39 (low dose) while rabbits infected with UAMS-4 had average scores of 0.95 +/- 0.23 (high dose) and 0.63 +/- 0.20 (low dose). Uninfected controls had an average score of 0.53 +/- 0.08. The results obtained with UAMS-1 were significantly different from those obtained with UAMS-4 at both doses (P < or = 0.047). The results obtained with UAMS-4 were not significantly different from those obtained with the controls at either dose of UAMS-4 (P > or = 0.150). On the basis of a similar five-point scale assessing histopathological evidence of disease, rabbits infected with UAMS-1 had average scores of 2.31 +/- 0.22 (high dose) and 1.96 +/- 0.36 (low dose) while rabbits infected with UAMS-4 had average scores of 1.58 +/- 0.29 (high dose) and 0.83 +/- 0.32 (low dose). Controls had an average score of 0.33 +/- 0.05. The results obtained with UAMS-1 were significantly different from those obtained with UAMS-4 at both doses (P < or = 0.040). However, the results obtained with UAMS-4 were significantly different from the controls only at the high dose of UAMS-4 (P = 0.025). We conclude that mutation of agr reduces the incidence and severity of disease but does not eliminate the ability to colonize bone and cause histopathological evidence of osteomyelitis.

Animals↗
PubMed1994

Use of medical resources and quality of life after acute myocardial infarction in Canada and the United States.

BACKGROUND: Much attention has been directed to the use of medical resources and to patients' outcomes in Canada as compared with the United States. We compared U.S. and Canadian patients with respect to their use of medical resources and their quality of life during the year after acute myocardial infarction. METHODS: A total of 2600 U.S. and 400 Canadian patients were randomly selected from the Global Utilization of Streptokinase and t-PA for Occluded Coronary Arteries (GUSTO) trial. Base-line data from their initial hospitalizations were analyzed, and the patients were then interviewed by telephone 30 days, 6 months, and 1 year after myocardial infarction to determine their use of medical care and quality of life. RESULTS: The Canadian patients typically stayed in the hospital one day longer (P = 0.009) than the U.S. patients but had a much lower rate of cardiac catheterization (25 percent vs. 72 percent, P < 0.001), coronary angioplasty (11 percent vs. 29 percent, P < 0.001), and coronary bypass surgery (3 percent vs. 14 percent, P < 0.001). At one year 24 percent of the Canadian and 53 percent of the U.S. patients had undergone angioplasty or bypass surgery at least once (P < 0.001). The Canadian had more visits to physicians during the follow-up year (P < 0.001), but fewer visits to specialists (P < 0.001). At 30 days, functional status was equivalent in the patients from the two countries. However, after one year the U.S. patients had substantially more improvement than the Canadian patients (P < 0.001). The prevalence of chest pain and dyspnea at one year was higher among the Canadian patients (34 percent vs. 21 percent and 45 percent vs. 29 percent, respectively; P < 0.001). CONCLUSIONS: The Canadian patients had more cardiac symptoms and worse functional status one year after acute myocardial infarction than the U.S. patients. The Canadian patients also underwent fewer invasive cardiac procedures and had fewer visits to specialist physicians. These results suggest, but do not prove, that the more aggressive pattern of care in the United States may have been responsible for the better quality of life.

Aged↗
PubMed1994

Predicting the risk of abrupt vessel closure after angioplasty in an individual patient.

OBJECTIVES: We proposed to examine the relation between angiographic morphologic characteristics and abrupt closure after coronary angioplasty and to develop an empirically based risk stratification system. BACKGROUND: Certain lesion morphologic characteristics are associated with higher rates of abrupt closure after coronary angioplasty. Previous approaches have been limited by relatively small sample sizes and an inability to combine multiple characteristics to predict risk in an individual patient. METHODS: Lesion morphology was determined for 779 lesions in 658 patients undergoing an elective first angioplasty. Abrupt closure occurred in 63 lesions (8.1%). Variables associated with abrupt closure were identified by univariate and stepwise multiple logistic regression analysis, and internal validity was assessed by use of bootstrapping. An empirically based scoring system was developed by assigning different weights to each predictive characteristic and was then validated. RESULTS: Almost all lesion characteristics previously labeled "adverse" were associated with an increased risk of abrupt closure, but only total occlusion, location at a branch point, increasing lesion length, evidence for thrombus and right coronary artery location were statistically significant independent predictors. Despite the large sample size, the study was underpowered to detect even a 50% increase in risk with many characteristics. Using a scoring system, we assigned each lesion a specific risk of abrupt closure. The distribution of risk was broad, with 20% of patients having < or = 2.5% risk and 25% having > 10% risk. Internal validation techniques revealed that when 10% of patients were randomly eliminated from the sample in multiple iterations, the risk estimates varied, again pointing to the need for a larger sample. CONCLUSIONS: Empirically based weighting of lesion characteristics could quantify the risk of abrupt closure for individual patients, but a very large sample will be required to understand the interplay of complex lesion characteristics in altering expected outcomes.

Aged↗
PubMed1994

Does body fat distribution promote familial aggregation of adult onset diabetes mellitus and postmenopausal breast cancer?

Noninsulin-dependent diabetes mellitus and postmenopausal breast cancer share a number of risk factors, including obesity, increased waist-to-hip ratio, and a positive family history. If risk for these diseases is mediated through a familial tendency for abdominal obesity, then one might expect to see familial clustering of both diseases. We analyzed data from a prospective cohort study of 41,837 Iowa women age 55-69 years. Diabetes was not associated with incidence of breast cancer [relative risk (RR) = 0.97]. The association between family history of breast cancer and breast cancer incidence, however, was slightly modified by individual history of diabetes: a positive family history of breast cancer in the absence of baseline diabetes was associated with a relative risk of 1.36 [95% confidence interval (CI) = 1.08-1.70], whereas the presence of both factors was associated with a RR of 1.87 (95% CI = 0.93-3.76). Adjustment for waist-to-hip ratio greatly diminished this difference. Conversely, a family history of breast cancer was associated with a RR of 5-year diabetes mortality of 1.94 (95% CI = 1.17-3.24) that persisted after stratification by tertile of waist-to-hip ratio. No clear association of family history of breast cancer and waist-to-hip ratio for self-reported diabetes incidence was evident. These data are indicative of a complex interrelation between waist-to-hip ratio, familial predisposition, diabetes, and breast cancer.

Adipose Tissue↗
PubMed1994

Continuing evolution of therapy for coronary artery disease. Initial results from the era of coronary angioplasty.

BACKGROUND: Survival after coronary artery bypass graft surgery (CABG) and medical therapy in patients with coronary artery disease (CAD) has been studied in both randomized trials and observational treatment comparisons. Over the past decade, the use of coronary angioplasty (PTCA) has increased dramatically, without guidance from either randomized trials or prospective observational comparisons. The purpose of this study was to describe the survival experience of a large prospective cohort of CAD patients treated with medicine, PTCA, or CABG. METHODS AND RESULTS: The study was designed as a prospective nonrandomized treatment comparison in the setting of an academic medical center (tertiary care). Subjects were 9263 patients with symptomatic CAD referred for cardiac catheterization (1984 through 1990). Patients with prior PTCA or CABG, valvular or congenital disease, nonischemic cardiomyopathy, or significant (> or = 75%) left main disease were excluded. Baseline clinical, laboratory, and catheterization data were collected prospectively in the Duke Cardiovascular Disease Databank. All patients were contacted at 6 months, 1 year, and annually thereafter (follow-up 97% complete). Cardiovascular death was the primary end point. Of this cohort, 2788 patients were treated with PTCA (2626 within 60 days) and 3422 with CABG (3080 within 60 days). Repeat or crossover revascularization procedures were counted as part of the initial treatment strategy. Kaplan-Meier survival curves (both unadjusted and adjusted for all known imbalances in baseline prognostic factors) were used to examine absolute survival differences, and treatment pair hazard ratios from the Cox model were used to summarize average relative survival benefits. For the latter, a 13-level CAD prognostic index was used to examine the relation between survival and revascularization as a function of CAD severity. The effects of revascularization on survival depended on the extent of CAD. For the least severe forms of CAD (ie, one-vessel disease), there were no survival advantages out to 5 years for revascularization over medical therapy. For intermediate levels of CAD (ie, two-vessel disease), revascularization was associated with higher survival rates than medical therapy. For less severe forms of two-vessel disease, PTCA had a small advantage over CABG, whereas for the most severe form of two-vessel disease (with a critical lesion of the proximal left anterior descending artery), CABG was superior. For the most severe forms of CAD (ie, three-vessel disease), CABG provided a consistent survival advantage over medicine. PTCA appeared prognostically equivalent to medicine in these patients, but the number of PTCA patients in this subgroup was low. CONCLUSIONS: In this first large-scale, prospective observational treatment comparison of PTCA, CABG, and medicine, we confirmed the previously reported survival advantages for CABG over medical therapy for three-vessel disease and severe two-vessel disease. For less severe CAD, the primary treatment choices are between medicine and PTCA. In these patients, there is a trend for a relative survival advantage with PTCA, although absolute survival differences were modest. In this setting, treatment decisions should be based not only on survival differences but also on symptom relief, quality of life outcomes, and patient preferences.

Angioplasty, Balloon, Coronary↗
PubMed1994

Prophylaxis against infection in total joint arthroplasty. One day of cefuroxime compared with three days of cefazolin.

The efficacy of cefuroxime was compared with the efficacy of cefazolin for prophylaxis against postoperative wound infection in a prospective, double-blind, multicenter study of 1354 patients who had had elective primary or revision total hip or knee arthroplasty. The patients were randomly assigned to receive either 1.5 grams of cefuroxime followed by 750 milligrams eight and sixteen hours later (for a total of one day of antibiotic treatment), or one gram of cefazolin every eight hours for nine doses (for a total of three days of antibiotic treatment). The first dose of each drug was administered fifteen to sixty minutes before the operative incision was made (for a primary operation) or after tissue samples had been obtained for culture (for a revision procedure). After the operation, the patients were assessed daily while hospitalized and then at two to three months and one year after the operation. Demographic characteristics and risk factors were similar in the two groups. For the patients who had had a primary hip arthroplasty, the rate of deep wound infection was 0.5 per cent (one of 187) for those who had received cefuroxime and 1.2 per cent (two of 168) for those who had received cefazolin. For the patients who had had a primary knee arthroplasty, the rate of deep wound infection was 0.6 per cent (one of 178) for those who had received cefuroxime and 1.4 per cent (three of 207) for those who had received cefazolin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Elution characteristics of gentamicin-PMMA beads after implantation in humans.

Seventeen patients had gentamicin-PMMA beads implanted for treatment of orthopedic infections. The authors found that beads implanted in patients for 3 to 36 weeks were capable of eluting high levels of antibiotic after retrieval. Beads that were implanted in patients for less than 10 weeks eluted significantly higher antibiotic levels than beads were implanted for more than 14 weeks. This study supports the local use of these beads in the treatment of musculoskeletal infections.

Drug Implants↗
PubMed1994

Initial stability of porous coated acetabular implants. The effect of screw placement, screw tightness, defect type, and oversize implants.

The effects of screw location, screw tightness, acetabular bony defects, and implant size on the initial stability of porous coated acetabular implants was studied in vitro using 12 fresh frozen cadaver pelves. The fixation of porous coated acetabular implants was compared following fixation with either rim or center screws. Implants were tested first under axial and torsional stress. Then, either a peripheral or central bony defect was created in the acetabulum and testing was repeated in a similar fashion. Rim screws were noted to significantly improve the initial fixation of implants in intact acetabula and in acetabula with central bony defects. It was also shown that the tightness of the screws is an important factor affecting the strength of fixation. Although bony defects compromise the fixation of implants, specimens with central defects were very stable, particularly when tested with axial load. Acetabula with peripheral defects lost significant stability. The use of larger implants in acetabula with bony defects was shown to increase bony coverage and the overall implant stability.

Acetabulum↗
PubMed1993

Long-term outcome following successful reopening of abrupt closure after coronary angioplasty.

Abrupt closure after coronary angioplasty is often successfully treated by repeat dilation. Long-term follow-up, including 6-month repeat catheterization and 12-month clinical evaluation, was obtained in 1,056 patients treated with acute (n = 335) or elective (n = 721) coronary angioplasty to evaluate the long-term impact of successful reopening of abrupt closure. Abrupt closure occurred in 13.5% of patients and was successfully reopened in 58%. Adverse outcomes including restenosis, death, bypass surgery, myocardial infarction and repeat angioplasty were compared between patients with successfully treated abrupt closure and those with successful procedures (residual diameter stenosis < or = 50%) without abrupt closure. For patients with acute angioplasty, the restenosis rates (> 50% diameter stenosis at follow-up) were 64% for those with successfully treated abrupt closure versus 36% for those with successful procedures without abrupt closure (p < 0.01). In addition, subsequent myocardial infarction (12 vs 3%; p = 0.01) and repeat angioplasty (21 vs 10%; p = 0.03) were more frequent in the group with abrupt closure. For patients with elective angioplasty, restenosis was 43% in those with successfully treated abrupt closure versus 45% in those without abrupt closure (p = NS). Subsequent death and myocardial infarction were more frequent in patients with abrupt closure (death: 12 vs 3% [p < 0.01]; myocardial infarction: 13 vs 3% [p < 0.01]). Long-term adverse events are increased in patients with successfully treated abrupt closure compared to those with successful procedures without abrupt closure.

Acute Disease↗
PubMed1993

Familial clustering of colon, breast, uterine, and ovarian cancers as assessed by family history.

The aggregation of colon, endometrial, ovarian, and possibly breast cancers in families has been described as a "cancer family syndrome" (now called Lynch syndrome II). To determine if the familial clustering of these malignancies was more common in women with cancer than without, we analyzed data from the Iowa Women's Health Study (IWHS), a population-based sample of 41,837 women aged 55-69 years. Self-reported information was collected on history of colon, uterine, ovarian, and breast cancers in female first-degree relatives. A family history of cancer of the breast (odds ratio [OR] = 1.4), colon (OR = 1.3), and uterus (OR = 1.3), but not ovary (OR = 1.2), was significantly more common among women with a personal history of any of these four cancers (all P < 0.05); the pattern of the ORs suggested strongly that the clustering tended to be site-specific. Age-adjusted relative risks (RR) of incident colon cancer over 5 years of follow-up (N = 237) were calculated with regard to family history. Colon cancer incidence was increased among women with a family history of breast (RR = 1.3), uterine (RR = 1.4), colon (RR = 1.5), and ovarian (RR = 1.3) cancers, although none of the risk estimates achieved statistical significance. RR was, however, significantly related to the number of different cancer sites reported among family members (Ptrend = 0.008). These data on a representative sample of postmenopausal women suggest that family histories of colon, breast, uterine, and ovarian cancers are associated with an increased risk of cancer at the same site, but provide little support for the hypothesis that Lynch syndrome II is a non-random occurrence.

Aged↗
PubMed1993

Difficulty becoming pregnant and family history as interactive risk factors for postmenopausal breast cancer: the Iowa Women's Health Study.

We recently provided data from a prospective cohort study of postmenopausal women which suggested that a first livebirth at age 30 or older (cf before age 20) was associated with a twofold increased risk of breast cancer in women without a family history, but a 5.8-fold higher risk in women with a positive family history. To address the question of whether these observations reflect difficulty becoming pregnant or maintaining a pregnancy, we performed additional analyses in which the outcome of each pregnancy was considered. During five years of follow-up, 620 incident cases of breast cancer were identified in the 37,105 women at risk. There was little evidence for an increased risk associated with a history of spontaneous abortion (relative risk [RR] = 1.1; 95 percent confidence interval [CI] = 0.9-1.4), nor was the risk higher among women who reported two or more spontaneous abortions in consecutive pregnancies (RR = 1.0, CI = 0.7-1.4). Although women who reported that they had tried unsuccessfully to become pregnant had only slightly and nonsignificantly elevated risks of breast cancer (RR = 1.1, CI = 0.9-1.3), a more pronounced and statistically significant association was noted in women with a positive family history (RR = 2.1, CI = 1.4-3.2). There was a strong inverse association between failure to become pregnant and parity (P < 0.0001); nearly 50 percent of the nulliparous married women reported having tried and failed to become pregnant, whereas the frequency was only 6.8 percent among married women with five or more livebirths.(ABSTRACT TRUNCATED AT 250 WORDS)

Abortion, Spontaneous↗
PubMed1993

Fine-needle aspiration biopsy in oral and maxillofacial surgery.

Fine-needle aspiration biopsy is a technique that is gaining great popularity in both surgical and nonsurgical specialties. Its accuracy, safety, and usefulness have been demonstrated repeatedly; however, its usefulness seems to have been overlooked by oral and maxillofacial surgeons. This technique has many advantages in the diagnosis of mass lesions, including ease of use, cost effectiveness, convenience, and accuracy. It lends itself well to oral and maxillofacial surgery.

Adolescent↗