Biomedical subjects
C L Nelson
Publications and source records attributed to C L Nelson.
Effect of an ultrasonic device on temperatures generated in bone and on bone-cement structure.
Cement removal during revision arthroplasty can be a tedious, time-consuming process. The usual methods of removing cement include high-speed drills, chisels, saws and reamers, which are often associated with fracture and/or perforation of the femoral shaft. Ultrasound has been used in dentistry to remove plaque and in ophthalmology to remove cataracts and is now applied to cement removal in orthopaedic surgery. There is little data available on the effect of ultrasound on temperatures generated in bone and on its effects on the structure of bone-cement. A cement mantle was constructed in the intramedullary canal in each of six 10 cm lengths of human cadaver femora. A temperature probe was then inserted into predrilled holes and temperatures generated by the ultrasonic device were recorded under a variety of conditions. In addition, a cement cylinder was microscopically evaluated after an ultrasonic tool had been inserted. Temperatures generated by the ultrasonic tool in cadaver bone were no higher than previously reported temperatures of 140 degrees C generated by high-speed drills. Furthermore, temperatures at the bone-cement interface never exceeded 60 degrees C when saline irrigation was used in conjunction with the ultrasonic tools, and were below 40 degrees C 1 minute after deactivation of the device. Microscopic examination shows that ultrasound produced local changes in the structure of bone-cement converting it from a microscopically spherical interlocked material to one that appears homogeneous and granular.
A biomechanical evaluation of an intramedullary fixation device for intertrochanteric fractures.
The strength and stability of an intramedullary device when used to fix intertrochanteric fractures were determined and compared with the dynamic hip screw (DHS). A standard four-part osteotomy was created in eight paired fresh frozen human cadaver femurs. The intramedullary fixation device and a DHS were implanted in each pair member, and mechanical testing was performed. Micromotion was measured during cyclic loading to determine implant stability, and then the specimens were loaded to failure. The intramedullary fixation device had significantly greater stability in cyclic loading than the DHS and required more than twice the force for failure. For patients with osteoporosis, this device may be a useful alternative to standard sliding nail systems.
Retention and strength of silicone-rubber catheters. A report of five cases of retention and analysis of catheter strength.
Five patients had a silicone-rubber catheter that broke during attempted removal. Mechanical testing was performed to determine the tensile strength of silicone-rubber as well as of polyvinyl chloride catheters. Silicone-rubber catheters were found to have a low tensile strength. The pull-out force of ten indwelling silicone-rubber catheters was also measured. The pullout force measured from a patient who had a cast was close to 40 per cent of the strength of the silicone-rubber catheters.
Gentamicin-impregnated polymethylmethacrylate beads compared with systemic antibiotic therapy in the treatment of chronic osteomyelitis.
A model of chronic osteomyelitis was used to evaluate the efficacy of treatment with debridement alone; debridement plus gentamicin-polymethylmethacrylate (PMMA) bead implantation; debridement plus systemic antibiotic therapy; and debridement plus systemic antibiotics and bead implantation. Debridement with the implantation of gentamicin-PMMA beads and debridement followed by systemic antibiotics were significantly more successful forms of treatment for chronic osteomyelitis than debridement alone or debridement with the implantation of PMMA beads not impregnated with antibiotics. Debridement followed by the implantation of PMMA-gentamicin beads and the use of systemic antibiotics produced the greatest success rate. Treatment with a combination of gentamicin-PMMA beads and systemic antibiotics resulted in a 100% success rate, which, although not statistically better than either treatment alone, suggests a trend.
Comparison of the clinical efficacy and tolerance of gentamicin PMMA beads on surgical wire versus combined and systemic therapy for osteomyelitis.
These data do not prove a statistical superiority of conventional antibiotics or Septopal in the treatment of chronic osteomyelitis. This result, however, is complicated by the biased data set represented by the combined treatment. The data do suggest that cost of treatment is considerably less in patients who are treated with local antibiotics (i.e., Septopal) alone. The rate of adverse experiences was directly related to the use of parenteral antibiotics, with higher rates of adverse experiences in the conventional and combined treatment groups. Furthermore, the Cierny-Mader Physiologic Class had the best correlation with outcome, suggesting that host factors are probably of critical importance in inducing remission of chronic osteomyelitis. This protocol was not designed to test the role of debridement in the treatment of osteomyelitis: it was assumed that debridement would be the same in both groups. It is the investigators' strong opinion, however, that adequacy of debridement was an important determinant in quiescence or recurrence in the study patients. Similarly, there was no strict control for adequacy of soft-tissue coverage provided by local or distant tissue transfer. Again, the investigators believe that adequacy, including viability and durability, of soft-tissue covering was an important determinant for the end result in these patients. Other covariants such as smoking, history, nutritional status, and other measures of general health will be added to this model when data are available. This analysis will allow definition of the appropriate clinical situations in which use of Septopal alone or combined with parenteral antibiotic is indicated.
A comparison of gentamicin-impregnated polymethylmethacrylate bead implantation to conventional parenteral antibiotic therapy in infected total hip and knee arthroplasty.
A multicenter study of infected total knee and total hip arthroplasties was conducted from 1985 until 1990. Twenty-eight patients (22 total hip arthroplasties and six total knee arthroplasties) who had periprosthetic infections were treated according to a prospective, randomized protocol. After initial debridement for their infections, patients were randomized into one of the two following groups: Group I, debridement and the implantation of gentamicin-polymethylmethacrylate (PMMA) beads; and Group 2, debridement and conventional parenteral systemic antibiotic therapy. After initial treatment, the patients were then scheduled for a delayed reconstruction total joint arthroplasty. Of the 28 patients, 25 subsequently had delayed total arthroplasty, and if acrylic bone cement was used for fixation at the time of reimplantation, antibiotics were not added to the cement. The average follow-up period was three years (range, six months to 5.6 years). Infection recurred in two patients treated by debridement and the implantation of gentamicin-PMMA beads (15%) and in four patients treated with debridement and conventional systemic antibiotic therapy (30%). All recurrences occurred in patients who had infected total hip arthroplasties; none occurred in patients with total knee arthroplasties. The conditions that were common in patients with recurrent infection were (1) multiple previous surgeries, (2) host compromise and malnutrition, (3) extensive infection, and (4) inadequate debridement. The recurrence of infection was not statistically significantly more common in either treatment group. The outcome of treatment in patients with infected total joint arthroplasties using debridement, gentamicin-PMMA bead implantation,and a two-stage delayed reconstruction was similar to that of patients treated with debridement combined with conventional parenteral systemic arthroplasty and two-stage reconstruction.
The effect of wound environment on the incidence of acute osteomyelitis.
A model was developed to identify and compare the local wound factors that induce acute osteomyelitis in a prospective, controlled investigation. When compared with wounds containing either virulent bacteria or dead bone, statistical analysis disclosed a significant increase in the incidence of osteomyelitis when virulent bacteria and dead bone were combined. The incidence of osteomyelitis in wounds containing an inoculated, hematoma-filled dead space was significantly less when compared with wounds containing dead bone and virulent bacteria. The incidence of osteomyelitis is significantly less when a nonvirulent strain of bacteria is substituted for a virulent strain. Although rigid internal fixation increased the incidence of osteomyelitis to 100% and long-term antibiotic therapy decreased the incidence, these changes were not statistically significant. These data allow the authors to predict the relative risk of osteomyelitis when these wound factors are present. The prevention of osteomyelitis depends on the clinical identification and modification of these local wound factors.
Dietary fat and postmenopausal breast cancer.
BACKGROUND: Although the results of animal studies and cross-cultural comparisons generally support a role for dietary fat in the etiology of breast cancer, results of analytic epidemiology studies are equivocal. PURPOSE: The association between dietary fat and subsequent breast cancer was examined in a cohort of 34,388 postmenopausal women from Iowa. METHODS: Dietary habits were assessed by a food-frequency questionnaire mailed in January 1986. Through December 31, 1989, 459 incident cases of breast cancer occurred in this cohort. Proportional hazards regression was used to examine the dietary fat-breast cancer association while adjusting for potential confounders. The effects on this association of four analytic approaches to adjustment for energy intake were also considered. RESULTS: After adjustment for known determinants of breast cancer, a modest positive association of total fat intake with risk of breast cancer was seen. Polyunsaturated fat intake was also positively associated with breast cancer (relative risk from lowest to highest intake, 1.0, 1.25, 1.31, and 1.49; P for trend = .052). Different approaches to adjustment for energy intake, however, provided different impressions of the dietary fat-breast cancer association. One method, involving categorization of crude fat intake and inclusion of total energy intake in regression analysis, gave relative risk estimates from low to high fat intake of 1.0, 1.17, 1.25, and 1.38 (P for trend = .18). Another method, based on categorization of fat intake residuals in which the variation in fat due to total energy intake was removed, gave corresponding estimates of 1.0, 1.24, 1.30, and 1.16 (P for trend = .29). The former suggests increasing breast cancer risk with increasing fat intake; the latter suggests no association. CONCLUSIONS: These results are consistent with other cohort studies that have shown a weak association or no association between dietary fat and breast cancer. They are also consistent with studies suggesting that fat intake is a determinant of breast cancer, particularly after accounting for inaccuracies in dietary assessment. The effects of different energy-adjustment methods may account in part for the varying interpretations of four previous cohort studies of dietary fat and breast cancer. IMPLICATIONS: Further work is needed to clarify not only the nature of the dietary fat-breast cancer association, but also the impact of different analytic methods used in the investigation of diet-disease associations.
Outcome of patients sustaining acute ischemic mitral regurgitation during myocardial infarction.
OBJECTIVE: To describe outcomes of patients sustaining an acute myocardial infarction complicated by mitral regurgitation managed with contemporary reperfusion therapies. DESIGN: Inception cohort case study. Long-term follow-up was obtained in 99% of all patients. SETTING: University referral center. PATIENTS: A series of 1,480 consecutive patients presenting between April 1986 and March 1989 who had emergency cardiac catheterization within 6 hours of infarction. Fifty patients were found to have moderately severe or severe mitral regurgitation. OUTCOME MEASURES: Mortality; follow-up cardiac catheterization in patients with regurgitation. RESULTS: Acute ischemic moderately severe to severe (3+ or 4+) mitral regurgitation was associated with a mortality of 24% at 30 days (95% CI, 12% to 36%), 42% at 6 months (CI, 28% to 56%), and 52% at 1 year (CI, 38% to 66%); multivariable analysis identified 3+ or 4+ mitral regurgitation as a possible independent predictor of mortality (P = 0.06). Patients with mitral regurgitation tended to be female, older, and to have cerebrovascular disease, diabetes, and preexisting symptomatic coronary artery disease. A physical examination did not identify 50% of patients with moderately severe to severe regurgitation. Acute reperfusion with thrombolysis or angioplasty did not reliably reverse valvular incompetence. In this observational study, the greatest in-hospital and 1-year mortalities were seen in patients reperfused with emergency balloon angioplasty, whereas patients managed medically or with coronary bypass surgery had lower mortalities. CONCLUSIONS: Moderately severe to severe (3+ or 4+) mitral regurgitation complicating acute myocardial infarction portends a grave prognosis. Acute reperfusion does not reduce mortality to levels experienced by patients with lesser degrees of mitral regurgitation nor does it reliably restore valvular competence.
Effect of family history, body-fat distribution, and reproductive factors on the risk of postmenopausal breast cancer.
BACKGROUND: A family history of breast cancer reflects shared cultural factors, genetic predisposition, or both. There is evidence that the estimated risk associated with a family history of breast cancer increases multiplicatively in combination with other risk factors. We examined the combined effect of family history and anthropometric and reproductive factors on the risk of breast cancer in postmenopausal women. METHODS: Using data from a prospective cohort study, we studied 37,105 women 55 to 69 years of age to determine whether known risk factors for breast cancer are modified by a reported family history at the time of entry into the study. RESULTS: During the first 4 years of follow-up, 493 new breast cancers were diagnosed. The association of the waist-to-hip ratio (the circumference of the waist divided by that of the hips) with the risk of breast cancer was limited predominantly to women with a family history of breast cancer; the age-adjusted relative risk of breast cancer for the women above the fourth quintile for waist-to-hip ratio as compared with those below the first quintile was 3.2 in women with a family history of breast cancer and 1.2 for women without such a family history. An interaction was observed between a family history of breast cancer and the number of live-born children; the protective effect of higher parity was observed primarily among women with a family history of breast cancer. Similarly, the age-adjusted relative risk of breast cancer associated with a late age at first pregnancy (i.e., greater than or equal to 30 years) was 5.8 for women with a family history of breast cancer and 2.0 for women without such a family history. CONCLUSIONS: The increase in the risk of breast cancer associated with a high waist-to-hip ratio, low parity, or greater age at first pregnancy is more pronounced among women with a family history of breast cancer. These findings suggest etiologic differences between familial breast cancer and the sporadic form.
Ergonovine maleate testing during cardiac catheterization: a 10-year perspective in 3,447 patients without significant coronary artery disease or Prinzmetal's variant angina.
The utility of ergonovine testing for coronary artery spasm was assessed in 3,447 patients with angiographically insignificant (less than 50% diameter stenosis) or no coronary artery disease. No patients clinically had Prinzmetal's variant angina. Overall, 4% had a positive ergonovine test result, defined by spasm causing greater than or equal to 75% focal stenosis. Complications related to ergonovine use occurred in 11 patients (0.03%). In a training sample of 1,136 patients (studied between 1980 and 1984), two independent predictors of spasm were found by using multivariate analysis: the amount of visible coronary artery disease on the coronary angiogram (p less than 0.0001) and a smoking history (p = 0.001). A model to predict spasm based on these variables was validated in a test group of 2,311 patients who received ergonovine from 1985 to 1989. This model allowed the identification of a subset of 400 patients in the validation sample who had a 10% positive test rate compared with a 2% positive test rate in the remaining patients. These results should permit clinicians who use provocative testing in the catheterization laboratory to reserve testing for the subset of this group of patients most likely to have abnormal findings.
Control of contamination of the operative team in total joint arthroplasty.
Reports of percutaneous transmission of blood-borne disease emphasize the need for control of intraoperative contamination. In a randomized prospective study, surgeons and surgical assistants involved in total hip and total knee arthroplasty adopted the following protocol: total body exhaust with hood, aspirator, knee-length impermeable gowns, foot covers, including knee-high covers and waterproof covers, and one of three combinations of gloving protocols: latex/latex changed hourly, latex/cloth, or latex/cloth/latex. All inner gloves were tested by a leak test. All needles and sharp instruments were passed on trays, and all contaminations and perforations were recorded. Each surgeon and assistant was inspected twice for contamination. There were no needle sticks, and only one of 267 personnel had head, neck, body, leg, or foot contamination. Perforation rates of inner gloves were 9.2% for latex/latex, 7.9% for latex/cloth, and 4.3% for latex/cloth/latex.
Vena caval filter use in orthopaedic trauma patients with recognized preoperative venous thromboembolic disease.
This study comprises a series of 35 patients with pelvic or lower extremity fractures requiring surgery who also had a documented significant acute deep venous thrombosis (DVT). The authors treated these with low-dose Coumadin and 36 vena caval filters, which were used prophylactically prior to surgery. The patients received low-dose warfarin after placement of the vena caval filters and were maintained at 1.3-1.5 times the prothrombin control value for 6 weeks to 3 months. In this group of patients, there were no fatal pulmonary emboli and no clinically significant complications from filter placement. There were nine asymptomatic filter complications demonstrated radiographically in eight patients. Additionally, one patient with a tilted vena caval filter required placement of another filter. The combination of vena caval filters and low-dose warfarin appears to be a successful and relatively safe method of managing those patients who have acute DVT and require surgery for their pelvic or lower extremity fractures.
In vitro elution characteristics of commercially and noncommercially prepared antibiotic PMMA beads.
The successful treatment of osteomyelitis with commercially prepared gentamicin-polymethylmethacrylate (PMMA) (Septopal) beads and surgical debridement has led to the use of this technique in the United States. However, commercially prepared gentamicin-PMMA beads are not currently available to orthopedic surgeons in the United States. Therefore, these surgeons commonly manufacture their own antibiotic-containing cement beads in the operating room at the time of surgery. There is little data that compare the antibiotic elution characteristics of such preparations to commercially prepared gentamicin-PMMA beads. This study compares the measured amount of antibiotic elution of either gentamicin or tobramycin from laboratory manufactured Zimmer, Simplex, or Palacos beads to commercially prepared gentamicin-PMMA (Septopal) beads. During a 30-day study period, commercially prepared gentamicin-PMMA beads eluted more total antibiotic and maintain higher concentrations than did antibiotic acrylic composites manufactured in the authors' laboratory.
Is anticoagulation indicated for asymptomatic postoperative calf vein thrombosis?
The purpose of this study was to determine the effect of anticoagulation on the incidence of thrombotic propagation and pulmonary embolism in patients with calf vein thrombosis after total hip or total knee arthroplasty. Patients undergoing arthroplasties had prospective surveillance for postoperative deep vein thrombosis by both bilateral contrast venography and venous duplex scanning. Calf vein thrombosis was documented by venography in 42 patients (50 limbs), including 29 of 253 patients undergoing total hip arthroplasty (11.4%) and 13 of 99 patients undergoing total knee arthroplasty (13%). Of patients on whom follow-up duplex scans were performed, heparin followed by warfarin anticoagulation was used in 11 (13 limbs) and withheld in 21 (25 limbs). Propagation of thrombosis to the popliteal or superficial femoral vein or both was detected by serial duplex scanning in 3 of 13 treated limbs (23%) and 2 of 25 untreated limbs (8%), (p = 0.43). All thrombus propagations were detected within 2 weeks of the operative procedure. There were no pulmonary emboli or deaths. Propagation of asymptomatic calf vein thrombosis after arthroplasty was not influenced by anticoagulation, suggesting that postoperative calf vein thrombosis need not be routinely treated. Serial venous duplex scanning is useful to identify the occasional patient in whom thrombotic propagation requiring anticoagulation develops.
Relation of clinical and angiographic factors to functional capacity as measured by the Duke Activity Status Index.
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Percutaneous transluminal coronary angioplasty in octogenarians as an effective therapy for angina pectoris.
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