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L S Levin

Publications and source records attributed to L S Levin.

At least 37 records · Page 2Linked to original sources
PubMed2000

What is the potential measurement error in occupational exposure studies?

This paper demonstrates statistical methods that estimate measurement error from available industrial hygiene data. Errors in measuring a continuous exposure variable may arise when all individuals in a work area are assigned the same exposure. An example is when the mean of exposure measurements obtained on a sample of individuals is assigned to all workers with similar jobs. This may lead to inaccurate point and interval estimates in exposure-response modeling. A method of simulating the distribution of true (i.e., unobserved) individual exposures is described in order to estimate the mean and variance of measurement error. The minimum variance unbiased estimator approximates the mean of lognormally distributed exposure measurements. The distribution of true individual exposures is approximated by the distribution of simulated estimates of mean exposure. The methodology is illustrated by exposure data from work areas manufacturing refractory ceramic fiber (RCF) and RCF products. Results show that exposure is slightly underestimated in work areas with between 25 and 113 exposure measurements; measurement error variance averages about 1.3% of the total variance.

Air Pollution, Indoor↗
PubMed2000

Management of lawnmower injuries to the lower extremity in children and adolescents.

Lawnmower-associated trauma remains a substantial source of extremity injury in the pediatric and adolescent patient populations, producing complex wounds that require a combined orthopedic and plastic surgical approach. The authors review their experience with 16 patients, 2 to 17 years of age (mean age, 6.2 years), who were admitted to Duke University Medical Center for lower extremity lawnmower trauma between January 1988 and December 1999. The average hospitalization time was 13.5 days, and an average of 2.9 surgical procedures per patient were performed. Early debridement and bony fixation were carried out in all patients; 8 patients sustained traumatic amputations. Fifteen of 20 nonamputation fractures involved the foot and were managed with either closed reduction or K-wire fixation. Three of five long-bone fractures underwent external fixation. Wound closure was achieved with direct closure or skin grafting in the majority of patients. However, five microsurgical free flap transfers were required for extensive defect reconstruction of the foot (N = 4) and knee (N = 1). Adequate immediate debridement, fracture reduction, and early primary or if necessary secondary wound coverage including microsurgical free tissue transfer to prevent further damage and long-term disability in these type of devastating injuries is recommended.

Accidents, Home↗
PubMed2000

The effect of muscle flap transposition to the fracture site on TNFalpha levels during fracture healing.

The trauma and sepsis that follow open fractures and wounds may lead to the production of various cytokines. Understanding wound healing requires a direct knowledge of the specific cytokines and the respective wound fluid levels that are present at the wound site. An animal model was designed that mimics the open fracture and the clinical repair of the human, high-energy open fracture. Canine right tibiae were fractured with a penetrating, captive-bolt device, then repaired in a standard clinical fashion using an interlocking intramedullary nail. Before primary wound closure, microdialysis probes were placed at the fracture site and in a muscle located at a contralateral site. Canines received one of the following experimental protocols: (1) tibial fracture (n = 5); (2) tibial fracture plus Staphylococcus aureus inoculation at the fracture site (n = 5); and (3) tibial fracture, S. aureus inoculation, and a rotational gastrocnemius muscle flap (n = 5). Microdialysis fluid samples were collected intermittently for 7 days. Tumor necrosis factor alpha (TNFalpha) levels at the fracture site were significantly elevated 3 to 34-fold (p<0.02), as compared with respective serum levels at all time points for all treatment groups. Fracture site TNFalpha levels were elevated (p<0.02) in days 1 through 6, as compared with the baseline and contralateral in all treatment groups. At days 1 through 6, the TNFalpha levels of the muscle flap group fracture site were significantly decreased by approximately 50 percent (p<0.05), as compared with the fractures without muscle flaps and regardless of additional S. aureus inoculation. On day 7, fracture site TNFalpha levels in all animal groups were similar, yet remained well above those of baseline TNFalpha. These results demonstrate that S. aureus does not further elevate TNFalpha levels in the presence of an open fracture and that a muscle flap reduces pro-inflammatory TNFalpha levels during early wound healing. This experimental model allows for the characterization of specific biological signals and cellular pathways that are influenced by bacterial infection and surgical closure. These data provide a scientific framework on which to judge or validate therapeutic regimens for open-fracture wound healing.

Animals↗
PubMed2000

Transesophageal echocardiography in quantification of emboli during femoral nailing: reamed versus unreamed techniques.

We quantified the embolic load to the lungs created with two different techniques of femoral nailing. Eleven patients with 12 traumatic femur fractures were randomized to reamed (7 fractures) and unreamed (5 fractures) groups. Intramedullary nailing was with the AO/ASIF* universal reamed or unreamed nail. Transesophageal echocardiography (TEE) was used to evaluate the quantity and quality of emboli generated by nailing. Data were analyzed using software that digitized the TEE images and quantified the area of embolic particles in each frame. The duration of each level of embolic phenomena (zero, moderate, severe) was used to determine total embolic load with various steps (fracture manipulation, proximal portal opening, reaming, and nail passage). Manual grading of emboli correlated highly with software quantification. Our data confirm the presence and similarity of emboli generation with both methods of intramedullary nailing. Unreamed nails do not protect the patient from pulmonary embolization of marrow contents.

Adolescent↗
PubMed2000

Subungual melanoma. A review of 93 cases with identification of prognostic variables.

From 1970 to 1996, 93 patients received diagnoses of subungual melanoma. Followup data were complete on all patients and reviewed with a median duration of followup of 5.2 years. This study identifies significant clinicopathologic variables that affect survival and provides the orthopaedic surgeon assistance in the early diagnosis and treatment of this lesion. Eight-three percent of patients presented with Stage I disease, whereas 17% had nodal or distant disease. Fifty-three percent had locally advanced disease at presentation. Twelve percent of the patients were African-American. Fifty-five percent of the lesions arose on the hands with thumb involvement predominating in more than half of these cases. Operative therapy consisted of amputation. Elective lymph node dissection was performed in 34 patients (37%) for Stage I tumors of intermediate thickness. Therapeutic node dissection was required in 16 patients (17%) for positive nodes. Five-year survival was 74% for patients with Stage I disease and 40% for patients with Stage II disease. Statistical analysis identified stage at diagnosis, Clark and Wihm's level, the patient's race, and the presence of ulceration as prognostic variables affecting survival. The diagnosis of subungual melanoma carries a grave prognosis and often is misdiagnosed in the early stages. The treatment of choice is amputation at the appropriate level.

Adolescent↗
PubMed1999

Weight change and lung function: implications for workplace surveillance studies.

This study evaluated the relationship between weight change and longitudinal measurement of lung function among 361 men providing at least five pulmonary function tests. The men in this study were participants in a workplace pulmonary surveillance program for subjects with exposure to refractory ceramic fibers (RCFs). Occupational and environmental studies are generally designed to evaluate factors suspected of causing excess decline in lung function. Failure to adequately account for all significant factors may lead to erroneous conclusions regarding change in lung function. This study utilized two different statistical models to evaluate longitudinal changes in a cohort of RCF workers. What was unique to this study was the modeling of longitudinally measured initial weight, weight change, and longitudinal exposure before and during the period of observation. Results showed a strong relationship between weight gain and longitudinal loss in lung function that approximated forced vital capacity declines of 16 mL for every kilogram of weight gain per year in both models. This value is comparable or greater in magnitude and significance to other factors known to be inversely related to lung function, such as age and pack-years smoking to time of initial testing. In conclusion, weight gain was found to have a significant impact on longitudinal change in lung function. Therefore, weight gain becomes a very important variable that requires consideration whenever longitudinal studies of pulmonary function are conducted.

Adult↗
PubMed1999

Microsurgery costs and outcome.

Reliable information on cost and value in microsurgery is not readily available in the literature. Driving factors for cost, determinants of complications, and cost-reduction strategies have not been elucidated in this population, despite such progress in other areas of medicine. Clearly, the time-consuming and costly nature of this endeavor demands that appropriate indications and patient management be delineated; to operate proactively in this cost-conscious time, financial and outcome determinations are critical. One hundred seven consecutive free-tissue transfers performed from 1991 to 1994 by a single microsurgeon were studied. Retrospective chart review for clinical parameters was combined with analysis of hospital costs and professional charges. Operating room and anesthesia costs were based on a microcost analysis of actual operating room time, materials, labor, and overhead. Other patient level costs were generated by Transition 1, a hospital cost-accounting system. The following issues were addressed: (1) flap survival; (2) total costs and length of stay for all free flaps; (3) payments received from various insurers; (4) breakdown of operating room costs by labor, supplies, and overhead; (5) breakdown of inpatient costs by category; (6) additional costs of complications and takebacks; (7) factors associated with complications and flap takebacks; and (8) cost-reduction strategies. Mean free flap operating room costs (exclusive of professional fees) ranged among case types from $4439 to $6856 and were primarily a function of operating room times. Elective patient cases lasted a mean 440 minutes. There was a large disparity in reimbursement: private insurers covered hospital costs (not charges) completely, whereas Medicare paid 79 percent and Medicaid only 64 percent. Length of stay, operative procedures, and complications had the greatest influence on inpatient costs in this group of free flap patients. Potential cost savings as a result of possible practice changes (e.g., shortening intensive care unit stays and avoiding staged operations) can be predicted. This analysis has caused a revision in these institutions' practice patterns and lays the foundation for planned outcome studies in this population.

Adult↗
PubMed1999

Donor-site morbidity comparison between endoscopically assisted and traditional harvest of free latissimus dorsi muscle flap.

Endoscopically assisted harvest of free latissimus dorsi muscle flaps is being used more frequently in reconstructive microsurgery because it requires a smaller incision and leaves a more acceptable scar in the donor site. Donor-site morbidity was compared between groups of 22 latissimus dorsi muscles harvested using the endoscopically assisted technique and 26 using the traditional technique. The results revealed no statistically significant differences in the amount of intraoperative bleeding, the incidence of postoperative hematoma and seroma, and the incidence of donor-site wound infection as assessed by the surgeon. However, a patient questionnaire revealed that even though it did not reach a statistically significant difference, endoscopically assisted harvest of the latissimus dorsi muscle had less pain and allowed earlier and better movement of the upper extremity of the donor site. The patients' attitudes and feelings about the scar and overall satisfaction were also higher in the endoscopic group, which demonstrated a statistically significant difference.

Endoscopy↗
PubMed1998

An industry-wide pulmonary study of men and women manufacturing refractory ceramic fibers.

An industry-wide pulmonary morbidity study was undertaken to evaluate the respiratory health of employees manufacturing refractory ceramic fibers at five US sites between 1987 and 1989. Refractory ceramic fibers are man-made vitreous fibers used for high temperature insulation. Of the 753 eligible current employees, 742 provided occupational histories and also completed the American Thoracic Society respiratory symptom questionnaire; 736 also performed pulmonary function tests. Exposure to refractory ceramic fibers was characterized by classifying workers as production or nonproduction employees and calculating the duration of time spent in production employment. The risk of working in the production of refractory ceramic fibers and having one or more respiratory symptoms was estimated by adjusted odds ratios and found to be 2.9 (95 percent confidence interval 1.4-6.2) for men and 2.4 (95 percent confidence interval 1.1-5.3) for women. The effect of exposure to refractory ceramic fibers on forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), the ratio of the two (FEV1/FVC), and forced expiratory flow (liters/second) between 25 percent and 75 percent of the FVC curve (FEF(25-75)) was evaluated by multiple regression analysis using transformed values adjusted for height, by dividing by the square of each individual's height. For men, there was a significant decline in FVC for current and past smokers of 165.4 ml (p < 0.01) and 155.5 ml (p = 0.04), respectively, per 10 years of work in the production of refractory ceramic fibers. For FEV1, the decline was significant (p < 0.01) only for current smokers at 134.9 ml. For women, the decline was greater and significant for FVC among nonsmokers, who showed a decrease of 350.3 ml (p = 0.05) per 10 years of employment in the production of refractory ceramic fibers. These findings indicate that there may be important sex differences in response to occupational and/or environmental exposure.

Adult↗
PubMed1998

Suture anchor repair of chronic radial ligament injuries of the metacarpophalangeal joint of the thumb.

Five cases of chronic instability of the radial collateral ligament of the thumb metacarpophalangeal joint are presented. All patients were treated using the Mitek suture anchor to reattach the avulsed ligament to bone in its anatomical position. Tendon advancement or graft reinforcement was not used in conjunction with the repair. A stable thumb metacarpophalangeal joint was achieved in each case with no recurrent instability or pain found within 9 months of follow-up. Postoperatively, each patient exhibited a full return to activities of daily living within 2 to 3.5 months. Grip and pinch strength and range of motion were nearly the same as in the uninjured hand. We recommend the Mitek suture anchor as a simple and effective method of repairing the chronic radial collateral ligament injury. The importance of correct anatomical placement of the anchor is stressed, and guidelines for this are discussed.

Adolescent↗
PubMed1998

Use of the balloon dissector in minimally invasive aesthetic and reconstructive surgery.

The use of minimally invasive surgery continues to evolve in all fields of surgery with new developments in techniques and instrumentation. One instrument that has evolved and become useful in the field of plastic surgery is the balloon dissector. The purpose of this paper is to examine the role of the balloon dissector in minimally invasive aesthetic and reconstructive plastic surgery. We define the concept of the fascial cleft-the loose areolar space between fascial linings. In addition, the balloon dissector and its use is described. The optical cavity created by the balloon dissector device is discussed, along with the two techniques used to maintain the optical cavity, and manual retraction and carbon dioxide insufflation. The application of the balloon dissector in various regions of the body is discussed along with its use in free tissue transfers. Three patients are presented to illustrate the application of the balloon dissector.

Adult↗
PubMed1998

Longitudinal estimates of pulmonary function in refractory ceramic fiber manufacturing workers.

Refractory ceramic fibers (RCF) are man-made vitreous fibers (MMVF) used in high-temperature industrial applications. Between 1987 and 1994, a prospective study evaluated pulmonary function of 361 male workers currently employed in RCF manufacturing and related operations for plausibility of a causal relationship between RCF exposure and pulmonary function changes. Workers included in the analysis provided at least five pulmonary function tests. The exposure-response relationship was modeled with two exposure variables: years in a production job, and cumulative fiber exposure (fiber-mo/cc). Comparison groups were nonproduction workers and workers with up to 15 fiber-mo/cc cumulative exposure. A statistically significant decrease in FVC was demonstrated among workers employed in production jobs more than 7 yr prior to initial test. A similar but nonstatistically significant result was demonstrated for FVC in workers with greater than 60 fiber-mo/cc cumulative exposure prior to initial pulmonary function test. Similar but nonstatistically significant results were obtained for FEV1. These findings, which primarily reflect workers employed before 1980, did not persist with analysis of follow-up production years and accumulated RCF exposure from initial pulmonary function test. Since longitudinal analyses are sensitive to influences that continue to affect annual decline during the study period, lower RCF exposure levels since the 1980s may be responsible for eliminating any further effect on pulmonary function.

Adult↗
PubMed1998

Chronic osteomyelitis of the tibia: treatment with hyperbaric oxygen and autogenous microsurgical muscle transplantation.

To establish the success rate of combined therapy for tibial osteomyelitis, we reviewed all cases of this infection treated with surgery, antibiotics, and hyperbaric oxygen (HBO) between 1974 and 1991 at Duke University Medical Center. The median delay from diagnosis of osteomyelitis to initiation of HBO was 12.5 months (range, 1 month to 684 months). Of 34 patients in whom follow-up data were complete, 27 (79%) were male and 7 (21%) female, with a mean age of 37.9 years (range, 20 years to 77 years). Patients received an average of 8.3 surgical procedures (range, 2 to 19) and 35 HBO treatments (range, 6 to 99). Twenty patients (59%) received free vascularized muscle flaps as part of therapy. Actuarial analysis was used to examine the effect of free vascularized flap procedures. Of 26 patients with 24 months of follow-up after treatment, 21 (81%) remained drainage free. At 60 months and 84 months after treatment, 12 of 15 (80%) and 5 of 8 (63%), respectively, were drainage free. After more than 84 months, patients who had received muscle flaps were more likely to be drainage free than patients who had received only debridement, and this difference approached statistical significance.

Adult↗
PubMed1997

Development and implementation of an extremity free-tissue-transfer database.

Rigorous clinical outcomes research requires accurate, complete, and standardized data. No such system is currently being used by reconstructive microsurgeons to evaluate free-tissue-transfer procedures. To facilitate collection of relevant and complete data, the authors propose a standardized format for data collection regarding these procedures. Data are collected via computer entry or scannable forms. The database includes sociodemographic, clinical, health/functional status, patient satisfaction, and resource utilization variables--the necessary components of a well-constructed clinical outcome study. Such studies will give rise to meaningful treatment algorithms for managing reconstructive problems. In addition, widespread use of a standardized databse will facilitate comparisons between practices and allow for meta-analyses. Resultant practice guidelines and microsurgery care maps will ultimately improve patient care and minimize unnecessary costs.

Databases, Factual↗
PubMed1997

The functional outcome of lower-extremity fractures with vascular injury.

Salvage of lower-extremity Gustilo type IIIC fractures is difficult, time-consuming for the patients and physicians, and not universally successful because of poor functional outcomes. Even if successful with limb salvage, the functional result may be unsatisfactory because of mutilating injuries to muscle and nerve, bone loss, and the presence of chronic infection. From July 1991 until July 1994, revascularizations of open IIIC fractures were attempted for wounds with Mangled Extremity Severity Score (MESS) < or = 10. The functional results were evaluated at 2 years after injury. Thirty-six lower-extremity revascularizations were performed on 34 patients, including 1 patient with bilateral distal tibial IIIC fractures and a child with IIIC femoral fracture accompanied by ipsilateral distal tibial amputation. Excluded were patients with below-ankle IIIC fractures as well as patients who underwent immediate amputation at admission. After the revascularization, seven patients with IIIC fractures (7 of 36, 19.4%) underwent secondary amputation within 1 week. At the 2-year follow-up, the overall secondary amputation rate was 25% (9 of 36) and the salvage rate was 75% (27 of 36). Those were no deaths. Of the 29 salvaged limbs among these 27 patients, 23 limbs (23 of 29, 79.3%) required secondary coverage procedures that included 12 free flap transfers (12 of 29, 41.4%). Every patient needed subsequent reconstructive surgery to achieve an acceptable functional result. In this series, MESS was able to predict the secondary amputation rate and the functional result. Sixteen of the 17 limb-salvaged patients with MESS < or = 7 were able to achieve minimal functional requirements, whereas 3 of the 10 patients with MESS = 8 to 10 failed to achieve minimal functional requirements at the 2-year follow-up. Using statistical analysis, we found that the salvaged limbs with MESS < or = 9 exhibited a significant difference in achieving adequate function compared with limbs with MESS > 9. Using our protocol for treatment for IIIC fractures, the threshold for immediate amputation can be raised from MESS = 7 to MESS = 9. Our conclusions are (1) more severely injured limbs have poor functional results, (2) every patient needs subsequent reconstructive surgery, and (3) the MESS may be helpful in decision-making.

Adolescent↗
PubMed1997

Complications concerning free rectus abdominis muscle flaps in patients with portal hypertension.

A high level of suspicion is required when treating patients with a history of esophageal bleeding and portal hypertension. The preoperative workup must be extensive; if the reconstructive surgeon is considering the use of a rectus abdominis muscle transfer, noninvasive studies and an exhaustive physical examination are required. Factors affecting the microcirculation might also influence the patency rates of the venous anastomosis and require further study. When treating these patients, the surgeon must be aware that portal hypertension can exist without clinical evidence.

Abdominal Muscles↗