Distribution of uranium in rats implanted with depleted uranium pellets. (1/121)

During the Persian Gulf War, soldiers were injured with depleted uranium (DU) fragments. To assess the potential health risks associated with chronic exposure to DU, Sprague Dawley rats were surgically implanted with DU pellets at 3 dose levels (low, medium and high). Biologically inert tantalum (Ta) pellets were used as controls. At 1 day and 6, 12, and 18 months after implantation, the rats were euthanized and tissue samples collected. Using kinetic phosphorimetry, uranium levels were measured. As early as 1 day after pellet implantation and at all subsequent sample times, the greatest concentrations of uranium were in the kidney and tibia. At all time points, uranium concentrations in kidney and bone (tibia and skull) were significantly greater in the high-dose rats than in the Ta-control group. By 18 months post-implantation, the uranium concentration in kidney and bone of low-dose animals was significantly different from that in the Ta controls. Significant concentrations of uranium were excreted in the urine throughout the 18 months of the study (224 +/- 32 ng U/ml urine in low-dose rats and 1010 +/- 87 ng U/ml urine in high-dose rats at 12 months). Many other tissues (muscle, spleen, liver, heart, lung, brain, lymph nodes, and testicles) contained significant concentrations of uranium in the implanted animals. From these results, we conclude that kidney and bone are the primary reservoirs for uranium redistributed from intramuscularly embedded fragments. The accumulations in brain, lymph nodes, and testicles suggest the potential for unanticipated physiological consequences of exposure to uranium through this route.  (+info)

Characteristics of bone ingrowth and interface mechanics of a new porous tantalum biomaterial. (2/121)

We have studied the characteristics of bone ingrowth of a new porous tantalum biomaterial in a simple transcortical canine model using cylindrical implants 5 x 10 mm in size. The material was 75% to 80% porous by volume and had a repeating arrangement of slender interconnecting struts which formed a regular array of dodecahedron-shaped pores. We performed histological studies on two types of material, one with a smaller pore size averaging 430 microm at 4, 16 and 52 weeks and the other with a larger pore size averaging 650 microm at 2, 3, 4, 16 and 52 weeks. Mechanical push-out tests at 4 and 16 weeks were used to assess the shear strength of the bone-implant interface on implants of the smaller pore size. The extent of filling of the pores of the tantalum material with new bone increased from 13% at two weeks to between 42% and 53% at four weeks. By 16 and 52 weeks the average extent of bone ingrowth ranged from 63% to 80%. The tissue response to the small and large pore sizes was similar, with regions of contact between bone and implant increasing with time and with evidence of Haversian remodelling within the pores at later periods. Mechanical tests at four weeks indicated a minimum shear fixation strength of 18.5 MPa, substantially higher than has been obtained with other porous materials with less volumetric porosity. This porous tantalum biomaterial has desirable characteristics for bone ingrowth; further studies are warranted to ascertain its potential for clinical reconstructive orthopaedics.  (+info)

Tracheal size following tracheostomy with cuffed tracheostomy tubes: an experimental study. (3/121)

In view of the severe damage caused by unyielding, low residual volume cuffs, various modifications to the cuff of an intratracheal tube have been introduced. The merits of two low-pressure cuffs were assessed in an experimental study in dogs; both cuffs produced little visible damage to the tracheal wall in dogs intubated continuously over a two-week period. A modified technique of producing tantalum tracheobronchograms without distrubing the mucous blanket or traumatizing the tracheal wall is described. These tantalum radiological studies demonstrated a progressive temporary increase in size of the trachea at cuff level over the period of intubation with these cuffs. The implications of such a progressive weakness occurring in the tracheal muscle are discussed.  (+info)

Evaluation of accuracy and precision of bone markers for the measurement of migration of hip prostheses. A comparison of conventional measurements. (4/121)

Our aim was to determine whether tantalum m arkers improved the accuracy and/or precision of methods for the measurement of migration in total hip replacement based on conventional measurements without mathematical correction of the data, and with Ein Bild Roentgen Analyse - Femoral Component Analysis (EBRA-FCA) which allows a computerised correction. Three observers independently analysed 13 series of roentgen-stereophotogrammetric-analysis (RSA)-compatible radiographs (88). Data were obtained from conventional measurements, EBRA-FCA and the RSA method and all the results were compared with the RSA data. Radiological evaluation was also used to quantify in how many radiographs the intraosseous position of the bone markers had been simulated. The results showed that tantalum markers improve reliability whereas they do not affect accuracy for conventional measurements and for EBRA-FCA. Because of the danger of third-body wear their implantation should be avoided unless they are an integral part of the method.  (+info)

Cold crucible levitation melting of biomedical Ti-30 wt%Ta alloy. (5/121)

Recently, titanium-tantalum alloys have been studied as implant materials for dental and orthopedic surgery. However, titanium and tantalum are difficult to mix by common arc melting and induction melting, because of their high melting point and the marked difference between their densities (Ti: 1,680 degrees C, 4.5 g/cm3, Ta: 2,990 degrees C, 16.6 g/cm3). Thus, the Cold Crucible Levitation Melting (CCLM) method was chosen to produce a Ti-30 wt%Ta binary alloy in the present study. The CCLM furnace, with 1 kg capacity, consisted of a water-cooled crucible comprising oxygen-free high purity copper segments and coils wrapped around the crucible and connected to a frequency inverter power supply. A qualified ingot of 1.0 kg of Ti-30 wt%Ta alloy was obtained. The ingot was characterized from the surface quality, chemical composition distribution and microstructure, and finally the melting process was discussed.  (+info)

Cost implications of introducing an alternative treatment for patients with osteoarthritis of the knee in a managed care setting. (6/121)

OBJECTIVES: To illustrate the current cost of treating osteoarthritis (OA) of the knee and to demonstrate potential savings associated with the new treatment modality of viscosupplementation in a managed care setting. STUDY DESIGN: Pharmacoeconomic model with inputs obtained from peer-reviewed medical literature, clinical trial data, clinical expert opinion, and claims data. METHODS: A spreadsheet-based model was developed to define a treatment pathway for OA of the knee, illustrate the current costs of treating patients with the condition, and demonstrate the potential savings associated with introduction of Hylan G-F 20. A hypothetical cohort of patients categorized as having mild, moderate, or severe OA of the knee was followed over a 3-year time period. The analysis was conducted from the perspective of a managed care plan with a large Medicare population. RESULTS: The 3-year savings associated with adding 1 or more courses of Hylan G-F 20 therapy to the standard treatment pathway for OA of the knee was $8,810,771. The total savings per OA patient receiving Hylan G-F 20 was $4706. The number of total knee replacements (TKRs) avoided was 808. The model was highly sensitive to the durability of Hylan G-F 20; increasing and decreasing durability within a reasonable range resulted in 3-year savings of $9,131,879 and $2,012,082, respectively. CONCLUSIONS: Hylan G-F 20 has proven to be an effective treatment for patients with OA of the knee. Appropriate use of Hylan G-F 20 could delay the need for TKRs and generate savings in the managed care setting.  (+info)

Bronchial hysteresis in excised lungs. (7/121)

1. Intrapulmonary bronchi in excised dog lungs were outlined with tantalum dust and stereoscopic radiographs taken during deflation and inflation of the lung with air, saline, Ringer or EDTA solutions. Dimensions of airways as a percentage of their values at full inflation were calculated from measurements of the stereoscopic X-ray images. 2. The mean deflation-inflation diameter difference at a transpulmonary pressure of 5 cm H2O was 20% in the air-filled lung, 9% in the saline filled preparation and 2% after filling with EDTA in saline. 3. These results show that the intrapulmonary bronchi have an intrinsic hysteresis separate from the hysteresis imposed on them by the expansion of the surrounding parenchyma. This intrinsic hysteresis is mainly due to the tone of the smooth muscle in the bronchial wall.  (+info)

Local ablative procedures designed to destroy squamous-cell carcinoma. (8/121)

In a series of experiments in dogs, the bronchial mucosa was either excised or destroyed prior to closure of a bronchial stump following a lobectomy or the reanastomosis of a divided bronchus. The experiments were designed to simulate the clinical situation in which focal areas of squamous-cell carcinoma in situ in the bronchial margin would be managed by local ablation of the mucosa rather than by excision of additional bronchus. The experiments demonstrated that the bronchial mucosa is not necessary for bronchial healing. They also demonstrated that functionally and morphologically normal bronchial epithelium regenerates across the denuded bronchus. The source of this regenerated epithelium appears to be the submucosal glands which remain in the bronchial wall after a variety of local ablative procedures. Since our clinical experience has demonstrated that these submucosal glands frequently contain small foci of squamous-cell carcinoma in situ, we have concluded that either excision or thermal destruction of the bronchial mucosa has very limited clinical application and should be considered only in patients who cannot tolerate excision of more than one lobe of the lung.  (+info)