Subsidence of an uncemented canine femoral stem

Factors contributing to subsidence were analyzed by radiographic evaluation and mechanical testing of 36 canine cadaver femora during and after insertion of an uncemented porous-coated femoral stem and by radiographic evaluation of 35 canine total hip arthroplasties. Mean percentage of canal fill in immediate postoperative radiographs, and percentage of canal fill at midimplant and distal implant locations, were accurate predictors of subsidence. Force required to implant the femoral stem was strongly correlated with force required for implant subsidence. Femoral morphology and percentage of canal fill at the middle and distal sites were accurate predictors of subsidence. Implants in femora with a stovepipe morphology (canal flare index less than or equal to 1.8) were six times more likely to subside than implants in femora that had a normal appearance (canal flare index 1.8 to 2.5), and 72 times more likely to subside than implants in champagne-fluted femora (canal flare index greater than or equal to 2.5). Femora with more than 85% mean, middle, or distal canal fill were less likely to subside.     

St.Agnes--the first year as the team sees it

The St. Agnes Community Health Centre was established in October 1974, in the rapidly growing area of Tea Tree Gully, South Australia. It was built to provide additional facilities to an already existing comprehensive medical centre. The embryo centre is described during the first year of operation through the eyes of the health team.     

Group education after myocardial infarction: Is it effective?

An analysis of the results of a study of a group of post-infarction patients who had received group instruction concerning the nature of myocardial infarction, compared with patients not so instructed, is presented. Contrary to expectation, anxiety levels as measured by the Catel IPTA Anxiety Scale were significantly higher in patients who experienced group education. Regardless of this finding, patients were subjectively appreciative of education.     

Demyelinating disease versus tumor in surgical neuropathology. Clues to a correct pathological diagnosis

Clinical presentations as well as radiological and histopathological findings in biopsies from patients with multiple sclerosis (MS) or other demyelinating disorders of the central nervous system are sometimes misleading, resulting in an erroneous diagnosis of brain or spinal cord tumor. We report 17 patients who presented with symptoms mimicking those of brain (14 cases) or spinal cord (three cases) tumors. Computerized tomography or magnetic resonance imaging studies or both were interpreted as consistent with a tumor in each case. All patients underwent surgery, and all 17 pathological specimens were eventually diagnosed as showing demyelinating disease, usually consistent with MS. In each case we examined a variety of histological features and immunohistochemical studies and addressed their relative importance in considering the diagnosis of MS. All cases showed perivascular lymphocytic inflammation with variable amounts of macrophage infiltration, necrosis, and edema. The hypercellularity of the lesions and the presence of atypical reactive astrocytes with mitotic figures were the disturbing features that might have led to the erroneous diagnosis of an astrocytic neoplasm. Immunohistochemistry for astrocytic (glial fibrillary acidic protein) and macrophage (HAM-56) markers are helpful in evaluating biopsies. Our results emphasize the need to perform special stains (i.e., for myelin and axons) that demonstrate myelin loss and relative preservation of axons and allow a correct diagnosis.     

Three-dimensional elastic finite element study of the skid resistance of grooved pavement

A three-dimensional finite element model has been developed to simulate the sliding of a rubber block over a grooved road surface. The model makes use of the symmetries of the problem to simplify the analysis, so that two-dimensional isoparametric elements of both rectangular and triangular configuration have been extended into the third dimension. A procedure for analysing the behaviour of any one groove to groove unit of the pavement is also developed, and this is extended so that the contact between the sliding rubber block and the leading edge of each raised pavement section is analysed. Preliminary comparisons between theoretical calculations and experimental measurements indicate that the finite element procedure provides an accurate and economical estimate of the behaviour of the rubber slider as it is pressed into a grooved pavement. Elastic predictions of sliding resistance seem reasonable at low sliding speeds, but viscoelastic rubber analysis appears necessary if higher speed skid resistance is to be predicted.     

Cellular and metabolic engineering. An overview

Metabolic engineering is defined as the purposeful modification of intermediary metabolism using recombinant DNA techniques. Cellular engineering, a more inclusive term, is defined as the purposeful modification of cell properties using the same techniques. Examples of cellular and metabolic engineering are divided into five categories: 1. Improved production of chemicals already produced by the host organism; 2. Extended substrate range for growth and product formation; 3. Addition of new catabolic activities for degradation of toxic chemicals; 4. Production of chemicals new to the host organism; and 5. Modification of cell properties. Over 100 examples of cellular and metabolic engineering are summarized. Several molecular biological, analytical chemistry, and mathematical and computational tools of relevance to cellular and metabolic engineering are reviewed. The importance of host selection and gene selection is emphasized. Finally, some future directions and emerging areas are presented.