ABSTRACT
BACKGROUND: Attempts to improve proximal load transfer and minimize stress shielding have included reducing the stiffness of femoral stems and using alternative stem materials, including carbon fiber composites. An uncemented implant (SR71) composed of a carbon-fiber-composite distal section and a porous-coated titanium-alloy proximal section, designed to improve proximal load transfer and provide good fixation, was clinically evaluated in a prospective randomized study. METHODS: Sixty patients were enrolled and randomized to receive either the SR71 stem or an all-metal stem (Stability). All patients received a cemented all-polyethylene acetabular component and a 28-mm metal femoral head. All uncemented stems were implanted by the same surgeon. Patients were followed for up to ten years with repeated assessments of bone mineral density, radiographs, Harris hip scores (HHS), and visual analog scale (VAS) pain scores. RESULTS: Ten years postoperatively, nineteen patients who had been treated with the SR71 stem and not lost to follow-up showed a significantly greater increase in proximal bone mineral density (Gruen zones 1 [p = 0.003] and 7 [p = 0.0007]) from baseline than did the twenty-two who had been treated with the Stability stem and not lost to follow-up. In contrast, the Stability group showed a significantly greater increase in distal bone mineral density (Gruen zones 2 [p = 0.0004], 3 [p = 0.0001], and 5 [p = 0.0035]) compared with the SR71 group. Radiographs demonstrated one case of progressive migration of an acetabular component used with an SR71 stem and one case of bone resorption in Gruen zones 7 and 14 in a patient treated with a Stability stem. There was no significant difference between the SR71 and Stability stems in terms of changes in the total HHS, HHS for pain, HHS for range of motion, or VAS pain scores ten years postoperatively relative to preoperative levels. There was one reported revision of an SR71 femoral stem at the ten-year review. CONCLUSIONS: The investigational SR71 implant provided increased proximal bone density and reduced distal bone density. The implant showed promising results at the time of early follow-up, and the clinical outcomes were similar to those of an all-metal stem at the time of a ten-year follow-up.
Subject(s)
Arthroplasty, Replacement, Hip , Hip Prosthesis , Osteoarthritis, Hip/surgery , Aged , Bone Density , Carbon , Carbon Fiber , Female , Follow-Up Studies , Humans , Male , Metals , Middle Aged , Prospective Studies , Prosthesis Design , Treatment OutcomeSubject(s)
Angioplasty, Balloon , Fluoroscopy , Radiation Monitoring , Humans , Radiation Dosage , Risk , Thermoluminescent DosimetryABSTRACT
The use of intravenous xenon- 133 for determination of radionuclide first pass right ventricular ejection fraction is described. First pass determinations of right ventricular ejection fraction were made with both xenon- 133 and technetium-99m in 13 subjects (15 right ventricular ejection fraction determinations); results obtained with xenon- 133 show an excellent correlation (r = 0.98, p less than 0.002) with results obtained using technetium-99m. Because of rapid pulmonary elimination of xenon- 133 from the body, the use of this radioisotope allows multiple first pass right ventricular ejection fraction determinations within a short period of time, without significant radiation exposure for the patient.
Subject(s)
Heart Ventricles/diagnostic imaging , Technetium , Xenon Radioisotopes , Acute Disease , Angina Pectoris/diagnostic imaging , Chronic Disease , Coronary Disease/diagnostic imaging , Heart Failure , Humans , Hypertension, Pulmonary/diagnostic imaging , Lung Diseases, Obstructive/diagnostic imaging , Myocardial Infarction/diagnostic imaging , Radionuclide ImagingSubject(s)
Radiology/instrumentation , Humans , Radiography/instrumentation , Technology, Radiologic , X-RaysABSTRACT
The depth-dose characteristics of the Toshiba LMR-16 linear accelerator for 14-MeV x rays have been measured at an SSD of 100 cm using diodes and ion chambers. The surface dose and build-up depth both exhibit a considerable variation with field size. A new central axis model has been developed which takes account of these variations, and the agreement between the measured and computed data using this model is found to be excellent. Formulas are also presented to estimate the surface dose, buildup depth, and output factor as a function of field size.
Subject(s)
Particle Accelerators/instrumentation , Radiation Dosage , Models, TheoreticalABSTRACT
A study of single-plane right anterior oblique left ventricular angiography was undertaken to determine the importance of obtaining correct positioning of a magnification grid and to develop a simple but accurate technique to minimize magnification errors. Theoretical and experimental volume determinations demonstrated 3% to 28% volume errors for grid placement errors ranging from 1 centimeter to 5 centimeters. An experiment was designed whereby cross table lateral radiographs of the chest were taken during contrast injections of the left ventricle. The relative position of the left ventricular center was found at a point 66% of the distance from the anterior to the posterior margin of the heart. Finding this point on noncontrast lateral films of the chest for positioning of a square centimeter grid should yield a more accurate determination of the magnification factor than other current emperic methods.
Subject(s)
Cardiac Volume , Cineangiography/methods , Ventricular Function , Heart Ventricles/diagnostic imaging , HumansSubject(s)
Blood Circulation , Krypton , Radioisotopes , Respiratory Function Tests/methods , Animals , DogsABSTRACT
The authors describe a coordinate measuring device developed to simplify manual acquisition of the digital information required for computerized three-dimensional treatment planning. This system has been used for two years and shown to be both fast and accurate. The time needed to digitize contour data is reduced to approximately one-tenth of that required for manual methods in most cases.
