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Biomedical subjects

S D Waldman

Publications and source records attributed to S D Waldman.

At least 19 recordsLinked to original sources
PubMed2005

Effect of zoledronate on bone quality in the treatment of aseptic loosening of hip arthroplasty in the dog.

Periprosthetic bone loss, which is a direct cause of aseptic loosening in total hip arthroplasty (THA), can be suppressed by bisphosphonates. It is unknown how the quality of this bone is affected in the presence of both wear debris (from implant) and bisphosphonates. The objective of this study was to evaluate the effect of zoledronate (ZLN) on bone quality in the presence of wear debris [polyethylene (PE) particles] in a canine model of uncemented THA. Thirty dogs underwent THA, and aseptic loosening was induced via implantation of PE particles packed into the femoral component. For 26 weeks until sacrifice, two groups (each n = 10) received weekly injections of ZLN (low dose 2 mug/kg, high dose 10 mug/kg) and the third group (control) received saline. Histological and radiographic examinations were performed to evaluate the degree of implant reaction. Histomorphometry (static/dynamic) was performed to evaluate bone turnover. Back-scattered electron imaging was used to quantify the newly formed bone and to evaluate the mineralization distribution. Density fractionation and X-ray diffraction were used to evaluate mineral properties, while four-point bending was used to determine mechanical properties. A dose-dependent presence of newly formed subperiosteal bone was found, which appeared to be less mineralized than the adjacent cortical bone. The high-dose ZLN group showed decreased cortical porosity and turnover and increased mineralization profile, failure strength, and modulus. We conclude that ZLN affects some of the material properties of cortical bone and allows the newly formed subperiosteal bone to remain and therefore affect the overall quality of the bone.

Animals↗
PubMed2005

A single application of cyclic loading can accelerate matrix deposition and enhance the properties of tissue-engineered cartilage.

OBJECTIVE: Mechanical stimulation is a widely used method to enhance the formation and properties of tissue-engineered cartilage. While studies have evaluated the responsiveness of chondrocytes to mechanical stimuli, little is known about how much stimulation is actually required. Thus, the purpose of this study was to investigate the effect of a single application of cyclic loading to chondrocytes on the formation and properties of in vitro-formed tissue. DESIGN: Isolated bovine articular chondrocytes were seeded on ceramic substrates in 3D culture and subjected to a single application of compressive cyclic loading at 1, 8 or 15 days after seeding. Once the time at which the chondrocytes were most sensitive to mechanical loading was determined, the effect of a single application on the synthesis and accumulation of matrix molecules as well as the mechanical properties of the in vitro-formed cartilage tissue was evaluated. RESULTS: Chondrocytes were more responsive to cyclic loading applied early in culture. Cyclic forces applied 24 h after the cultures were established increased collagen and proteoglycan syntheses (48 +/- 11% and 49 +/- 11%, respectively). This single application of cyclic loading also increased the accumulation of collagen (stimulated: 207 +/- 20 microg, control: 173 +/- 9 microg) and proteoglycans (stimulated: 302 +/- 24 microg, control: 270 +/- 14 microg) as well as improved the mechanical properties of the in vitro-formed tissue (twofold increase in equilibrium stress and modulus) determined 4 weeks after the applied stimulus. CONCLUSIONS: A single application of cyclic loading to chondrocytes early in culture increased matrix accumulation and enhanced the mechanical properties of the in vitro-formed tissue. This suggests that mechanical forces do not have to be applied intermittently over long periods of time to accelerate in vitro tissue formation.

Animals↗
PubMed2004

The steroidal aromatase inhibitor exemestane prevents bone loss in ovariectomized rats.

The irreversible steroidal aromatase inhibitor exemestane (EXE) is one of three third generation aromatase inhibitors currently prescribed for advanced breast cancer in postmenopausal women. Its principal mechanism of action is to reduce estrogen by inhibiting its synthesis. In addition to its efficacy against breast cancer, its effects on other organs are important, especially when given to women with good-prognosis breast cancer or potentially to healthy women at increased risk of developing breast cancer. The purpose of this study was to evaluate the effects of EXE on bone and lipid metabolism in ovariectomized (OVX) rats. Ten-month-old Sprague-Dawley female rats were sorted into intact controls, intact + EXE, OVX controls, and OVX + EXE groups, and treated by weekly intramuscular injection with vehicle or 100 mg/kg EXE for 16 weeks. The bone mineral density (BMD), mechanical testing, histomorphometry, bone resorption marker-serum pyridinoline (PYD), and bone formation marker-serum osteocalcin (OC) were used to determine the effects of treatment on bone. In addition, total serum cholesterol, triglyceride, high-density lipoprotein (HDL), and low-density lipoprotein (LDL) were determined. BMD of the lumbar spine and femur were 11% and 7%, respectively, higher in OVX animals given EXE than in OVX controls (all Ps<0.001). Significant increases in the bending strength and toughness of the femora as well as the compressive strength and elastic modulus of the vertebrae were observed in OVX rats given EXE (all Ps<0.02 vs. OVX controls). Trabecular bone volume (BV) was significantly higher in OVX rats treated with EXE than in OVX controls (P<0.0001). In OVX animals, EXE reduced the OVX-induced increase of serum PYD by 96% (P<0.0001), and the OVX-induced increase of serum OC was completely prevented by treatment with EXE. In OVX animals, EXE resulted in a 28% reduction of serum cholesterol (P<0.0001) and reduced LDL by 64% compared with OVX controls (P<0.0001). The positive results of EXE on bone and lipid metabolism in the OVX rat model merit further investigation of the effects of EXE in postmenopausal women.

Androstadienes↗
PubMed2002

Polycyclic aromatic hydrocarbons present in cigarette smoke cause bone loss in an ovariectomized rat model.

A number of epidemiological studies have suggested that cigarette smoking is a risk factor for osteoporosis. Benzo(a)pyrene (BaP) and 7,12-dimethylbenz(a)anthracene (DMBA) are polycyclic aromatic hydrocarbons (PAHs) found in the tar fraction of cigarette smoke, as well as in car exhaust and furnace gases. We hypothesized that BaP and DMBA are responsible, through interaction with the aryl hydrocarbon receptor (AhR), for the bone loss and fragility seen in smoking-related osteoporosis. In this study four groups of 9-month-old Sprague-Dawley rats were examined. An intact group served as controls. A second control was the ovariectomized (ovx) group. The third group (ovx + E(2)) were ovariectomized and also given a continuous basal dose of estrogen by implanted estrogen pellet (0.085 mg of 17beta-estradiol per rat). The fourth group (ovx + E(2) + BaP/DMBA) was ovariectomized with an estradiol pellet, and received subcutaneous injections of 250 microg/kg of BaP/DMBA weekly for 15 weeks. The loss of ovarian function allowed the study of a direct effect of BaP/DMBA on bone while the concomitant estrogen repletion prevented ovx-related bone loss. Dual-energy X-ray absorptiometry (DEXA), histomorphometry, image analysis, and mechanical testing were used to determine the effect of the treatments on bone. The DEXA results showed a significant (p < 0.05) decrease in bone mineral density compared with intact controls with both ovx alone and with ovx + E(2) + BaP/DMBA treatment. The ovx + E(2) rats were similar to the intact controls. The osteoid parameters showed a significant increase (p < 0.05) with BaP/DMBA addition vs. intact controls, mimicking the ovx rats. The ovx + E(2) rats had osteoid parameters comparable to those of intact rats. Bone connectivity was decreased in the ovx and ovx + E(2) + BaP/DMBA animals. Connectivity of the ovx + E(2) rats was comparable to that of intact animals. A decrease in failure force was seen in three-point bending for the ovx + E(2) + BaP/DMBA group and in vertebral compression in both the ovx and ovx + E(2) + BaP/DMBA groups vs. intact controls. The mechanical properties of the ovx + E(2) rats were similar to those of intact rats. These results demonstrate that BaP/DMBA causes a loss of bone mass and bone strength, possibly through an increase in bone turnover. This is the first in vivo study linking environmental toxicants, found in the tar fraction of cigarette smoke and in urban air pollution, to loss of bone mass and strength in estrogen-replete ovx rats.

Animals↗
PubMed2001

Nasal morphology and shape parameters as predictors of nasal esthetics in individuals with complete unilateral cleft lip and palate.

OBJECTIVE: The purpose of this study was to assess the ability of shape parameters of nasal morphology to predict esthetics in individuals with complete unilateral cleft lip and palate (CUCLP). METHODS: This retrospective study involved 28 patients with repaired CUCLP. Nostril morphology was analyzed using nose casts and a video-imaging technique. Calculated shape parameters included area, perimeter, centroid, angle of the principal axis, major and minor moments of area, anisometry, bulkiness, lateral offset, and three-dimensional internostril angles. Esthetics was assessed using a panel of six orthodontists who rated nasal esthetics from frontal, lateral, basal, and three-quarters view slides and from nose casts. Correlations between esthetics and the shape parameters were completed using the entire group as well as using two statistically determined subsets: those with the best and those with the worst esthetics. RESULTS: Nasal esthetics was related to only the perimeter and bulkiness parameter ratios. Symmetry of the perimeters between the right and left nostrils positively correlated with better esthetics using the entire sample group while symmetry of bulkiness between the right and left nostrils positively correlated with better esthetics using both the entire sample group and the best and worst subsets. CONCLUSIONS: Only perimeter and bulkiness showed positive correlations with nasal esthetics. The group of parameters used to assess nostril morphology had neither significant correlation with-nor predictive power for-esthetics. Thus, an assessment of the entire nasal surface topography in three dimensions needs to be completed and assessed with respect to predictability of nasal esthetics.

Adolescent↗
PubMed2000

Diabetic neuropathy: diagnosis and treatment for the pain management specialist.

Diabetic neuropathy is the name used by clinicians to describe a heterogeneous group of diseases that affect the autonomic and peripheral nervous systems of patients suffering from diabetes mellitus. This article provides the pain management specialist with an overview of the pathophysiology and current trends in the diagnosis and treatment of these diseases. Because of the significant morbidity and suffering associated with diabetic neuropathy, this article emphasizes practical steps to prevent, treat, and manage diabetic neuropathy to assist the pain management specialist in caring for patients suffering from this common malady.

Diabetic Neuropathies↗
PubMed2000

Video-imaging assessment of nasal morphology in individuals with complete unilateral cleft lip and palate.

OBJECTIVE: The purpose of this study was to develop a video-imaging mathematical method to assess nostril morphology. DESIGN: This retrospective study involved two age-matched groups: 28 subjects with complete unilateral cleft lip and palate (CUCLP) and 19 noncleft controls. Nose casts were reproducibly oriented in a jig such that the casts could be rotated about the coronal axis. Video images of the nostrils were captured and then analyzed for area, perimeter, centroid, principal axis, moments about the major and minor axes (I11, I22), anisometry, bulkiness, lateral offset, internostril angle, and rotational angle. RESULTS: All parameters identified nostril asymmetry in both groups. The results of the analyses using anisometry, I11, and I22 showed that, in both groups, one nostril was rounder and one was more elliptical. This asymmetry, however, differed between the two groups, and the difference was primarily based on the degree of ellipticity of the nostrils. Maximum dimension, perimeter, lateral offset, I11, and I22 were more asymmetric in the cleft group. In the control group, the right nostril was more elliptical and had a greater perimeter, and the left-side nostril had a greater bulkiness (enfolding). CONCLUSIONS: The method developed was validated for assessment of nasal morphology in cleft and noncleft samples. Nostril morphology was asymmetric in both groups but more asymmetric in the cleft group than the control group. The dominant influence of the cleft resulted in more elliptical noncleft nostrils and greater nostril shape asymmetry in the cleft group. The validated video-imaging method can now be used to assess the efficacy of treatment on nasal morphology.

Adolescent↗
PubMed1999

Imposed state of deformation determines local collagen fibre orientation but not apparent mechanical properties.

In a previous study, we have shown that the observed biaxial material behaviour of planar connective tissues is influenced by the sample gripping method. Commonly used suture attachments produced an apparently more compliant and extensible material compared to the same sample with clamped edges. We hypothesized that these differences were due to the imposed collagen fibre constraint under each method. In this study, we have directly compared the collagen fibre orientations which result under both gripping schemes. Small angle light scattering (SALS) was used to determine collagen fibre orientations in square bovine pericardial samples, before and after a 10% equibiaxial stretch. Local fibre distributions were determined at the sample centre and at the grip-sample interface. Resulting scattering patterns were statistically compared using repeated measures ANOVA. After stretch, collagen fibre distributions were identical at the sample centre where deformation is measured--but not at the sample boundaries. Therefore, the central fibre orientation distribution appears to be exclusively determined by the imposed deformation state. However, it is important to note that the loads necessary to achieve a given deformation depended strongly on gripping method. The resulting apparent differences in mechanical properties must be due to the method of load transmission. Indeed, fibres were observed to arc around suture attachment points, suggesting a discontinuous load transfer to the specimen which produced an apparent increase in extensibility and compliance. By contrast, only smooth transitions were observed at the clamped edges. Direct transmission of load from grip-to-grip in clamped samples (away from the sample centre) increased apparent stiffness.

Animals↗
PubMed1997

Dynamic contact stress and rolling resistance model for total knee arthroplasties.

Problems associated with premature failure of total knee replacements (TKR's) include: wear, creep, and oxidation of ultrahigh-molecular-weight polyethylene (UHMWPe) as well as adverse tissue reactions to polyethylene wear debris. These problems are associated in part with the mechanical behavior of UHMWPe. In TKR's, contact stress analyses have been performed on the UHMWPe tibial component; however, most have employed simplified material properties and not accounted for joint kinematics. A nonlinear viscoelastic rolling model was developed for TKR's to predict the contact stress and rolling friction for varying rolling speed, conformity, applied load, and tibial plateau thickness. Results indicated that the contact stress increased and rolling friction decreased with increasing rolling speed. Effects of conformity, applied load, and tibial plateau thickness were consistent with previous models. At large rolling speeds, predicted peak contact stresses were almost twice their static value, resulting in a compound fatigue problem in UHMWPe components due to normal cyclic loading, moving point of contact, and velocity-dependent stresses.

Elasticity↗
PubMed1994

Compressive stress relaxation behavior of irradiated ultra-high molecular weight polyethylene at 37 degrees C.

The preconditioned stress relaxation behavior of irradiated ultra-high molecular weight polyethylene (UHMWPE), a commonly used bearing surface in total joint replacements (TJR), was modelled in uniaxial compression at 37 degrees C. Twenty cylindrical specimens (10 mm dia. x 27 mm length) were machined from a compression molded plate of medical grade UHMWPE and gamma-irradiated to a minimum dose of 2.5 Mrad. At an initial strain rate 1000%/s, five specimens were each tested at constant strains of 1, 2, 5, and 10%. The modified superposition principle provided a good agreement of the nonlinear viscoelastic (stress relaxation) behavior of UHMWPE (standard error of 0.0753 MPa).

Biocompatible Materials↗
PubMed1992

Acute and postoperative pain. Management from a primary care perspective.

Most pain is controllable. Patient education and careful intraoperative technique are useful prophylactic measures. Simple analgesics and non-steroidal anti-inflammatory drugs reduce pain, fever, and inflammation and are well tolerated when dosing guidelines are followed carefully. In patients whose pain is not controlled with these measures, the addition of a weak narcotic analgesic is reasonable. If relief is still inadequate, a stronger narcotic alone or in combination with another analgesic may be needed. The advent of patient-controlled analgesia has diminished some of the objections to continuous intravenous infusion of narcotics. Various acute-pain syndromes respond to blockade of the sympathetic or somatic neural pathways. Knowledge of the appropriate anatomic structures and careful technique are mandatory with this method. Moreover, it should be considered only one part of a comprehensive treatment plan.

Acute Disease↗
PubMed1991

Issues in the selection of local anesthetics.

Several factors influence the safety with which neural blockade is performed, and something as simple as proper packaging can make a significant difference. For example, bulk packaging, individual boxes, and labels all should be color coded for easy identification and to alert the prescriber of ingredients requiring particular caution. One must also take care not to confuse single-use with multiple-use products, if the latter cannot be eliminated from formulary. Furthermore, substitutions must be made properly, particularly to avoid complications associated with products that contain preservatives.

Anesthetics, Local↗