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Biomedical subjects

S H Stern

Publications and source records attributed to S H Stern.

At least 19 recordsLinked to original sources
PubMed2000

Evaluation of the safety and efficacy of enoxaparin and warfarin for prevention of deep vein thrombosis after total knee arthroplasty.

Of 263 patients who underwent total knee arthroplasty, 122 received adjusted low-dose warfarin and 141 received enoxaparin as deep vein thrombosis (DVT) prophylaxis. Three patients in the warfarin group and 3 in the enoxaparin group developed ultrasound-detectable DVT (P > .05). Although the amount of perioperative blood transfused was equivalent in both groups, the overall hemoglobin drop was greater (P < .005) in the enoxaparin group (2.9 g/dL) as compared with the warfarin group (2.3 g/dL). Five patients (4.6%) in the warfarin group and 16 (11.3%) in the enoxaparin group had bleeding complications (P < .05). Our data support earlier published reports suggesting that reductions, if any, in the incidence of DVT associated with enoxaparin are offset by a significant increase in bleeding complications as compared with adjusted-dose warfarin. We continue to use adjusted-dose warfarin as primary thromboembolic prophylaxis after total knee arthroplasty.

Aged↗
PubMed1999

Patient dosimetry activities in the United States: the nationwide evaluation of X-ray trends (NEXT) and tissue dose handbooks.

In the United States the Food and Drug Administration (FDA) in collaboration with the Conference of Radiation Control Program Directors (CRCPD) and state and local government agencies surveys clinical facilities about X-ray system air kerma and ancillary data related to patient dosimetry for a variety of diagnostic X-ray examinations. The survey program is known as the Nationwide Evaluation of X-ray Trends (NEXT). The survey utilizes reference patient-equivalent phantoms in the collection of comprehensive technical information. With knowledge of the skin-entrance air kerma, specific tissue doses can be calculated. An overview of NEXT and previously published FDA tissue dose handbooks for diagnostic X-ray examinations is presented.

Child↗
PubMed1998

Posterior tilting of the tibial component decreases femoral rollback in posterior-substituting knee replacement: a computer simulation study.

Posterior tilting of the tibial component is thought to increase the range of motion in posterior cruciate-retaining total knee replacement, but its effect on implant motion in posterior cruciate-substituting total knee replacement is unknown. This issue has become of interest recently because manufacturers have introduced instrumentation that produces a posteriorly tilted tibial cut for both implant types. The purpose of this study was to investigate how motion of posterior cruciate-substituting total knee replacement is affected when the tibial component is installed with posterior tilt. Sagittal plane implant motions were predicted from prosthesis geometry with use of a computer simulation in which the femoral condyles were assumed to sit in the bottoms of the tibial condylar wells when the knee was in extension. Rollback of the femoral component was produced by a cam-spine mechanism at higher angles of flexion. The simulations revealed that even small degrees of posterior tilt reduced rollback by limiting the interaction between the cam and spine. Tilting the component posteriorly by 5 degrees caused the cam to contact the spine at a knee flexion angle that was 18 degrees higher than with the untilted component. The results suggest that posterior tilting of the tibial component in posterior cruciate-substituting knee replacement may not produce the same beneficial effects that have been reported for the tilting of tibial components in posterior cruciate-retaining knee replacement.

Arthroplasty, Replacement, Knee↗
PubMed1998

Determinants of cognitive performance in systemic lupus erythematosus.

Patients with systemic lupus erythematosus (SLE) may have a variety of neuropsychiatric syndromes. Assessment of cognitive functioning for these patients is complicated by increased prevalence and disease severity among groups obtained lower scores on measures of cognitive functioning in normative national samples. Cognitive ability was quantified in a diverse cohort of patients with SLE and a demographically matched group of control participants. Hierarchical regression demonstrated a small increase (6%) in explained variation in cognitive functioning when presence of SLE was added to the equation derived from demographic variables. No significant interaction was found between race and disease. These results suggest that increased frequency of cognitive impairment in African Americans with SLE is due to the additive effects of psychosocial variables.

Adult↗
PubMed1997

The relationship of socioeconomic status, race, and modifiable risk factors to outcomes in patients with systemic lupus erythematosus.

OBJECTIVE: To study the relationship of race, socioeconomic status (SES), clinical factors, and psychosocial factors to outcomes in patients with systemic lupus erythematosus (SLE). METHODS: A retrospective cohort was assembled, comprising 200 patients with SLE from 5 centers. This cohort was balanced in terms of race and SES. Patients provided information on socioeconomic factors, access to health care, nutrition, self-efficacy for disease management, health locus of control, social support, compliance, knowledge about SLE, and satisfaction with medical care. Outcome measures included disease activity (measured by the Systemic Lupus Activity Measure), damage (measured by the SLICC/ACR damage index), and health status (measured by the SF-36). RESULTS: In multivariate models that were controlled for race, SES, center, psychosocial factors, and clinical factors, lower self-efficacy for disease management (P < or = 0.0001), less social support (P < 0.005), and younger age at diagnosis (P < 0.007) were associated with greater disease activity. Older age at diagnosis (P < or = 0.0001), longer duration of SLE (P < or = 0.0001), poor nutrition (P < 0.002), and higher disease activity at diagnosis (P < 0.007) were associated with more damage. Lower self-efficacy for disease management was associated with worse physical function (P < or = 0.0001) and worse mental health status (P < or = 0.0001). CONCLUSION: Disease activity and health status were most strongly associated with potentially modifiable psychosocial factors such as self-efficacy for disease management. Cumulative organ damage was most highly associated with clinical factors such as age and duration of disease. None of the outcomes measured were associated with race. These results suggest that education and counseling, coordinated with medical care, might improve outcomes in patients with SLE.

Adult↗
PubMed1997

Risk factors for early work disability in systemic lupus erythematosus: results from a multicenter study.

OBJECTIVE: To study the risk factors for early work disability in systemic lupus erythematosus (SLE). METHODS: A sample of 159 SLE patients who had been employed at some time since diagnosis was drawn from a multicenter study of outcome in SLE. Disease activity, organ damage, education, income, source of health insurance, and work-related factors were measured in a standardized interview. Work disability was defined by patient self-report of not working because of SLE. The outcome measure was current work status. Seven patients were excluded from the analysis because their choice not to work was unrelated to SLE. RESULTS: An average of 3.4 years after diagnosis, 40% had quit work completely, and job modification was substantial. Univariate analysis (chi-square and t-test) showed that significant predictors of early work disability included having a high school education or less, receiving Medicaid or having no health insurance, having a job which required more physical strength, having an income below poverty level, and having greater disease activity at diagnosis. In multivariate models, significant predictors were education level (P = 0.0004), higher physical demands of the job (P = 0.0028), and higher disease activity at diagnosis (P = 0.0078). Race, sex, cumulative organ damage at diagnosis, and disease duration were not significant. CONCLUSION: Early work disability in SLE is strongly associated with some sociodemographic factors that might be amenable to intervention.

Adult↗
PubMed1997

The effect of tibial stem design on component micromotion in knee arthroplasty.

Rigid body mechanics with computer data acquisition and analysis techniques were used to determine the three-dimensional motions of any point on the tibial component of a total knee arthroplasty. Three stem configurations were compared: (1) no stem; (2) short stem (40 mm); and (3) long stem (75 mm). In addition, three loading conditions were analyzed for each stem configuration: (1) central loading; (2) posterior loading; and (3) medial loading. The longer stem implants were associated with increased micromotion, especially under eccentric loading. Cemented implants seemed to have more stable fixation, compared with noncemented implants. It was thought that the increased motion was secondary to a toggling of the implant under load, secondary to uneven medullary cortical contact. Overall, the results indicated that short and long stems do not enhance initial fixation with cemented or cementless implantation in routine knee arthroplasty.

Arthroplasty, Replacement, Knee↗
PubMed1996

Diagnosis and management of the infected total knee arthroplasty.

While infection in TKA is a relatively infrequent complication, it can be devastating in terms of morbidity and cost. Prevention of infection begins with patient selection. Prior knee sepsis surgery, rheumatoid arthritis, and poor general health may lead to an increased rate of infection. Prophylactic antibiotics, meticulous surgical technique, and control of the intraoperative environment have been shown to be beneficial in prevention of infection after TKA. Diagnosis can be difficult and often is heralded by the onset of pain in a previously pain-free knee. Aspiration is an excellent screening tool and is also beneficial in determining management of potentially infected TKAs. In cases posing a diagnostic dilemma, radiographs and nuclear medicine studies also may prove beneficial as well as intraoperative frozen section. Management is based on chronicity of the infection and fixation of the components. Antibiotic suppression is unlikely to yield a cure but may be indicated in the medically infirm. Debridement with component retention may be used with varying degrees of success, especially in the acute postoperative period. The current treatment of choice for chronic infections in this country is a two-stage revision with interim intravenous antibiotics. This would be expected to yield a cure in approximately 80% of patients. Arthrodesis may be necessary in the patient who is status post-multiple revisions with particular virulent organisms. Resection arthroplasty should be reserved for the older rheumatoid patient with limited functional demands. Finally, amputation should be considered in the patient with life-threatening sepsis or the patient who is status post-multiple revisions with intractable pain and poor bone stock.

Anti-Bacterial Agents↗
PubMed1996

Proprioception after arthroplasty: role of the posterior cruciate ligament.

To test the hypothesis that retaining the posterior cruciate ligament during total knee arthroplasty helps preserve the threshold of proprioceptive sensation, a machine was designed that permitted direct measurement of passive angular deflection from a resting point to the threshold of patient perception. Sixty patients with unilateral primary total knee arthroplasties were evaluated; 30 with posterior cruciate ligament retaining prostheses and 30 with posterior cruciate ligament substituting prostheses. All patients had a minimum postoperative followup of 1 year, a good or excellent result as defined by the Hospital for Special Surgery Knee Score, and no evidence of peripheral neuropathy. The gender and age distributions were equivalent between groups. The average threshold of perception for the posterior cruciate ligament retention group was 2.4 degrees. The average threshold of perception for the posterior cruciate ligament substitution group was also 2.4 degrees. Substitution or retention of the posterior cruciate ligament makes no clinical difference in proprioception as measured by threshold testing. This study provides new information for surgeons performing total knee arthroplasty to aid in the decision to retain or substitute the posterior cruciate ligament. Previous proprioception evaluation in patients with posterior cruciate ligament retaining versus posterior cruciate ligament substituting arthroplasties, using different testing methods, has revealed different results.

Adult↗
PubMed1995

The independence and stability of socioeconomic predictors of morbidity in systemic lupus erythematosus.

OBJECTIVE: We studied the relationship between systemic lupus erythematosus (SLE) morbidity and socioeconomic status (SES) at 5 centers. METHODS: Ninety-nine patients who met American College of Rheumatology criteria for SLE were randomly sampled at each center, balancing by race and insurance status. Subjects were interviewed for current and past SES factors, such as insurance, occupation, employment, education, and income. SLE disease activity was measured by the SLE Activity Measure (SLAM). RESULT: Higher education, private insurance/Medicare, and higher income were associated with less disease activity at diagnosis. Controlling for SES, race, and center, the best predictors of less active disease at diagnosis were private insurance/Medicare (P = 0.002) and higher education (P = 0.007). From the time of diagnosis to the study visit (mean 3.5 years), insurance, income, and employment status changed for a significant number of subjects (37%, 16%, and 21%, respectively). CONCLUSION: Private insurance or Medicare and higher education are associated with less active disease at diagnosis of SLE. Health insurance, income, and employment status are unstable measures of socioeconomic status and may explain the variability in conclusions of previous studies on the role of SES in SLE.

Adult↗
PubMed1995

Tradeoffs between motion and stability in posterior substituting knee arthroplasty design.

The purpose of this study was to examine how changes in component geometry of posterior substituting knees affect tibiofemoral kinematics and prosthesis stability. Most posterior cruciate ligament substituting prostheses rely on an articulation between a femoral cam and tibial spine to provide anterior-posterior stability of the knee. Failure of this ligament substitution mechanism has resulted in knee dislocations with several different posterior substituting designs. A computer model of a generic posterior substituting prosthesis was altered to analyze the effects of five design parameters (tibial spine height, spine anterior-posterior position, femoral component posterior radius, and femoral cam anterior-posterior and distal-proximal position) on prosthesis stability, tibiofemoral kinematics, and maximum obtainable knee flexion. Prosthesis stability was characterized by a 'dislocation safety factor', defined as the vertical distance from the bottom of the femoral cam to the top of the tibial spine. Computer simulations revealed that posterior substituting knees are most likely to dislocate at maximum knee flexion. Prosthesis stability can be improved by increasing the tibial spine height and moving the femoral cam posteriorly. Our results suggest there is a tradeoff between maximum knee flexion and prosthesis stability. We found that relatively small gains in maximum knee flexion, made through design changes, may cause substantial decreases in prosthesis stability.

Arthrography↗
PubMed1995

Stability and range of motion of Insall-Burstein condylar prostheses. A computer simulation study.

The Insall-Burstein Posterior Stabilized Prosthesis (Zimmer, Warsaw, IN) uses an articulation between a femoral cam and tibial spine to provide anteroposterior stability to the knee. Dislocation can occur if the femoral cam translocates anteriorly and over the tibial spine. A computer model was used to examine the effects of design changes made between the Insall-Burstein I (IB I), Insall-Burstein II (IB II), and revised Insall-Burstein II (IB IIR) knees. The effects of these design changes were determined from their influence on knee stability and maximum obtainable knee flexion. Knee stability was characterized by a dislocation safety factor, defined as the vertical distance from the top of the tibial spine to the bottom of the femoral cam. Our analysis showed that the dislocation safety factor is greatest at approximately 70 degrees of knee flexion for all IB knees. As knee flexion is increased from this angle, the dislocation safety factor decreases, reducing knee stability. The simulations highlighted a trade-off between improving knee flexion and improving knee stability. The geometry of the IB II knee allowed greater knee flexion. The maximum flexion achieved with the IB II knee was 125 degrees compared with 115 degrees and 117 degrees for the IB I and IB IIR knees, respectively. However, the simulations indicate that the IB I and IB IIR knees are less likely to dislocate because they have greater dislocation safety factors than the IB II knees.

Biomechanical Phenomena↗
PubMed1995

Simulation of the upper gastrointestinal fluoroscopic examination for calculation of absorbed dose in tissue.

In order to simulate the upper gastrointestinal fluoroscopic examination, modifications were made to the Monte Carlo radiation-transport code that uses the anthropomorphic, mathematical reference phantoms ADAM and EVA. A set of discrete x-ray field projections of the principal anatomy of clinical interest has been previously defined. This note describes the new features incorporated in the simulations--divergent beams in oblique irradiation geometries, an esophagus and a duodenum, a double contrast medium consisting of a BaSO4-H2O mixture and air in the esophagus, stomach, and duodenum, and clinically representative beam qualities. The absorbed doses in tissues per unit entrance exposure (free-in-air) computed with the modified code appeared in Department of Health and Human Services Publication FDA 92-8282, Handbook of Selected Tissue Doses for the Upper Gastrointestinal Fluoroscopic Examination. A minor correction is described for the previously reported results for the esophagus.

Contrast Media↗
PubMed1995

Analysis of hospital cost in total knee arthroplasty. Does length of stay matter?

In this study, actual hospital total joint expenditures were analyzed, and the effect of decreased length of stay on these actual costs was determined. Expenditures were stratified per hospital and accounting conventions into fixed and variable costs. Hospital costs associated with 15 index knee arthroplasty procedures from fiscal years 1992, 1993, and 1994 were analyzed. Expenditures were standardized to inflation-controlled 1994 dollars. Average length of stay for knee arthroplasty procedures decreased 30% during this period (range, 8.7-6.1 days). Also, expenditures for total knee arthroplasty decreased only 13% (range, $17,415-$15,200) in inflation-controlled 1994 dollars. Using inflation-controlled dollars, analysis of variable costs revealed a continued rise of $278 during this period. Therefore, essentially all the cost reductions achieved were in the fixed component of cost allocated to each patient. Length of stay reductions, although beneficial, did not reduce hospital variable expenses significantly. Expenditure reductions were most exclusively in fixed costs. However, the overall total fixed hospital costs were largely unchanged. Thus, it is necessary to decrease variable costs (implant and supply costs) to significantly reduce hospital expenditures.

Aged↗
PubMed1994

Hematologic and circulatory changes associated with total knee arthroplasty surgical instrumentation.

This study evaluated the effects of intramedullary instrumentation when used on the femur and tibia. Twenty-six patients (52 knees) undergoing bilateral index cemented total knee arthroplasty were analyzed. Bilateral knee arthroplasties were chosen because the increased surgery would theoretically maximize any perioperative hemodynamic or hematologic changes. Patients were randomized into one of two groups depending on the exact form of surgical instrumentation used. Group I (intramedullary) knees were implanted with standard intramedullary fluted instruments. No special measures to vent the entrance holes were made. Group II (extramedullary) knees were implanted with an extramedullary tibial guide, in conjunction with an intramedullary femoral guide placed through a vented femoral hole. All patients manifested significant changes in their hematologic and hemodynamic values after arthroplasty. Leukocytes increased 85% on average, whereas fibrinogen (106%) and erythrocyte sedimentation rates (145%) also showed significant increases. Conversely, patients exhibited a relative thrombocytopenia (63%) nadiring on the second postoperative day. However, there was no significant differences seen between the two instrumentation groups. Hemodynamically, all patients exhibited rises in cardiac index (52%) and pulmonary artery pressures (64%). Analysis of the hemodynamic results in this study does demonstrate subtle evidence of increased pulmonary vascular resistance in the intramedullary group. Specifically, the intramedullary group had lower cardiac indexes, in association with higher pulmonary pressures. This increase in pulmonary vascular resistance with the use of intramedullary instrumentation may represent subtle evidence of increased lung injury in this group. Results point to the continued use of fluted intramedullary rods and vented entrance holes as a reasonable surgical technique in patients undergoing knee arthroplasty.

Aged↗
PubMed1993

Hematologic effects of total knee arthroplasty. A prospective evaluation.

In a prospective evaluation of 41 patients (57 knees) treated with index cemented total knee arthroplasty, perioperative blood testing was performed on blood counts, fibrinogen, and fibrin degradation products (FDP). The preoperative platelet count averaged 314/nl (range, 160-502/nl), whereas postoperatively, the count nadired at an average of 173/nl (range, 60-305/nl). Fibrinogen levels increased from 304 mg/dl (range, 170-442 mg/dl) to an average high of 647 mg/dl (range, 317-1018 mg/dl). Patients were also classified according to whether they had been treated with unilateral or bilateral procedures. Postoperatively, unilateral patients had an average 32% decrease in the platelet count, compared with the 64% decrease seen in bilateral patients. Analysis of fibrin split products revealed a trend toward greater elevation of these degradation products after bilateral procedures. The hematologic changes represented evidence of activation of the coagulation and fibrinolytic systems. These changes tended to be more pronounced in patients treated with bilateral procedures, and were manifested in postoperative elevation of fibrinogen and fibrin degradation products, with reductions in the platelet count. The degree of relative thrombocytopenia raises concerns about careful evaluation of candidates for bilateral arthroplasty, especially when determining the preoperative platelet count.

Aged↗
PubMed1993

Unicondylar knee arthroplasty. An evaluation of selection criteria.

In a prospective evaluation of 165 consecutive patients (228 knees), intraoperative evaluation of the knees was performed at the time of total knee arthroplasty. Each of the three knee compartments was independently graded for arthritic changes depending on the extent of articular degeneration visualized. Patients were believed to be suitable candidates for unicondylar knee arthroplasty (UKA) if they fulfilled the Kozinn and Scott criteria. Specific attention was given to patient age, weight, preoperative range of motion, angular deformity, as well as the extent of intraoperative cartilage erosions seen. Thirty-five knees (15%) were candidates for UKA based solely on inspection of the articular surfaces at the time of surgery. Further analysis revealed that of these 35 knees, 22 failed to meet the other selection criteria. Thus, of the original 228 knees, only 13 knees (6%) fulfilled all of the stringent selection requirements and were considered suitable candidates for UKA. With proper patient selection, the number of UKAs performed could become relatively small.

Adult↗