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Biomedical subjects

H A Paul

Publications and source records attributed to H A Paul.

At least 19 recordsLinked to original sources
PubMed2006

Shear banding in twinned structure of copper deformed at 77 K.

The local crystallography and microstructure within shear bands has been examined in single crystals of {112}<111> orientation of pure copper deformed at 77 K by channel-die compression to true strains of about 1. Setting up a system for making high-resolution orientation maps using transmission electron microscopy has provided advantageous circumstances for the analysis of orientation changes within shear bands. The present work shows that, despite the plane strain deformation mode, the mechanism of lattice rotation within emerging shear bands may lead to Goss {110}< 001> and Brass{110}<112> texture components.

Journal Article↗
PubMed1993

Management of bone loss in revision total hip arthroplasty using custom cementless femoral components.

Forty-seven consecutive revision total hip arthroplasties were performed using porous ingrowth custom-made prostheses designed from plain radiographs and computed tomography scans. At an average follow-up period of 30 months (range, 2-4 years), one revision has been required for loosening. The average Harris pain score was 39 and the average total score was 84 at the last follow-up evaluation. Complications included nine cases (19%) with intraoperatively detected fractures of the proximal femur treated with cerclage wires and seven cases (15%) with subsidence greater than 3 mm. There were no postoperative infections and only two dislocations. At the time of surgery local particulate bone graft was used in all cases. Thirty-four percent required structural graft to restore bone stock; no case required grafting for prosthesis stability. Management of bone loss in total hip arthroplasty using a custom cementless prosthesis appears to provide an attractive alternative to massive bone grafting.

Adult↗
PubMed1992

Using a database to analyze core basic science content in a problem-based curriculum.

As medical schools critically reevaluate their methods of instruction and as the number of innovative programs increases, the content delivered across disciplines must be carefully reviewed. However, few methods of content analysis have been applied to problem-based programs. In 1989-90 and 1990-91, the authors analyzed the distribution of basic science content in the 53 cases in the problem-based curriculum of Rush Medical College of Rush University. They developed a content vocabulary and created a database using a widely available computer software program. The content areas specific to each case were identified by faculty using the content vocabulary. To determine whether these content areas were actually identified by the students participating in the problem-solving sessions, the authors surveyed the 36 student participants in the classes of 1993 and 1994 and also interviewed the 15 faculty facilitators of the sessions. The surveys and interviews demonstrated that over 90% of the content areas identified by the faculty were actually covered by the students. The authors conclude that the database assists in their review of the curriculum for omission and redundancy. Other uses and limitations of this method are also discussed.

Biological Science Disciplines↗
PubMed1992

Development of a surgical robot for cementless total hip arthroplasty.

The long-term success of cementless total hip arthroplasty (THA) may depend on bone ingrowth into the porous-fixation surfaces of the implant. The ingrowth process is facilitated when the surgeon achieves a satisfactory fit for the prosthesis. Clinically or roentgenographically visible failure and persistent thigh pain after cementless THA remain significant problems, both of which may be alleviated by more precise preparation of the femoral canal and selection of an appropriately sized prosthesis. The objective of this study was to obtain an exact fit for the prosthesis through the use of an image-directed surgical robot for femoral canal preparation.

Arthroplasty↗
PubMed1991

An experiment in medical education. A critical analysis using traditional criteria.

In 1984, in addition to its standard traditional curriculum, Rush Medical College (Chicago, Ill) developed a Socratic problem-based method of teaching basic science material called the alternative curriculum. As part of an evaluation of this new curriculum, students in the two curricula were compared using three traditional measurements: (1) test scores from the National Board of Medical Examiners, Part I; (2) test scores from the National Board of Medical Examiners, Part II; and (3) performance on an oral examination. Alternative curriculum students did not differ significantly from their traditional curriculum classmates on National Board of Medical Examiners, Part I and Part II total scores, although their subset scores on Part I did tend to be lower, reaching significance in one subset area. Differences in performance favoring the traditional curriculum were primarily seen in the early years of the program. Alternative curriculum students in the class matriculated in 1987 scored significantly higher in three of five categories on the oral examination.

Adult↗
PubMed1988

Effects of estrogen deficiency on the growth of tissue into porous titanium implants.

The effect of systemic deficiency of estrogen on the growth of tissue into porous titanium-fiber implants was studied in ovariectomized Beagle dogs. Five dogs were ovariectomized and five dogs had a sham operation. After waiting four months to allow the levels of circulating estrogen to decline, a titanium-alloy implant that contained four surface pads of titanium-alloy mesh was implanted in the proximal part of the humerus of each dog bilaterally. Two months later, the implants were harvested and subjected to a mechanical push-out test and quantitative histological study. The push-out strength of the implants from the ovariectomized dogs was 31 per cent less than in the control animals. Ovariectomy caused no difference in the amount of ingrowth of bone but resulted in a significant increase in the amount of fibrous connective tissue within the porous pads. The presence of this fibrous tissue appeared to have an important effect on bone-implant fixation: in the control dogs, strength correlated positively with ingrowth of bone and negatively with ingrowth of fibrous tissue, whereas in the ovariectomized dogs, strength correlated positively with ingrowth of fibrous tissue and not at all with ingrowth of bone.

Animals↗
PubMed1987

Histologic changes in the dog acetabulum following total hip replacement with current cementing techniques.

Histologic changes in the acetabuli of adult dogs were studied following total hip replacement with current cementing techniques. Active bone remodeling was evident throughout the acetabulum by 2 weeks after operation and continued throughout the 6 months of the study, leading to considerable hypertrophy of the trabecular bone of the acetabulum. By 6 months after operation, a thick (average, 0.4 mm), fibrous membrane had formed at the bone-cement interface in 83 of 84 sections examined. Direct apposition of bone to cement was seen only within the 2-mm fixation holes. Formation of a fibrous membrane appears to be intrinsic to the cementing of the acetabular component, perhaps because geometry of the acetabulum precludes effective pressurization of the cement.

Acetabulum↗
PubMed1987

Efficacy of bone staples for fixation.

The pull-out strength of two types of bone staples (A, Techmedica; B, Richards) was evaluated in a canine model and compared with a control of 6.5 mm cancellous bone screw (Synthes). Fifteen adult mongrel dogs were divided into three groups of five animals each. The implants were placed in the lateral femoral condyle and proximal humerus on the right side at time zero, and on the left side 3 weeks later. The dogs were killed at 6 weeks. In addition a third site, the tibial tubercle, was used to examine the effectiveness of each device for patellar tendon reattachment. The strength of the reattached patellar tendon was measured and compared with a control intact patellar tendon insertion. The pull-out loads from bone of the two staple types are not statistically different. The displacement to failure, however, was found to be 71% greater (p less than 0.007), and the work to failure 128% greater (p less than 0.010) for staple A as compared with staple B. This may be of clinical relevance in avoiding staple back-out. Both staples were inferior to the screw for pull-out load displacement and work to failure (p less than 0.0001). All reattached tendons were significantly weaker (mean 202 N) than the intact tendon (mean 1,448 N) regardless of implant type. The dissected specimens uniformly showed necrosis of the tendon under the implant. Healing was by massive scar formation surrounding the implant.

Animals↗
PubMed1986

In vivo versus in vitro polymerization of acrylic bone cement: effect on material properties.

Flexural strength and molecular weight of polymethylmethacrylate bone cement were determined for cement polymerized in vivo in a canine total hip replacement and cement from the same batch polymerized in vitro. Both in vivo and in vitro samples showed a slight increase in flexural strength and modulus at 2 weeks, followed by a nearly equivalent decline at 8 weeks. In vitro and in vivo samples exhibit a comparable stress to failure, but the in vivo samples show a significantly increased strain and decreased modulus. Cement from the proximal region of the prosthesis has significantly decreased flexural strength, lower modulus, and lower molecular weight than cement from the distal region and plug, suggesting that failures in the proximal region of a prosthesis may be due to inferior physical and mechanical properties of the bone cement in that region.

Animals↗
PubMed1986

Histologic changes in the dog femur following total hip replacement with current cementing techniques.

Histologic changes in the femurs of adult dogs were studied following total hip replacement using current cementing techniques. In the diaphyseal region, remodeling was initiated in the periosteum and progressed centripetally over 3 months. In the proximal (metaphyseal) region, remodeling was seen throughout the section by the second week. No fibrous membrane was formed at the bone-cement interface in the proximal region, and only isolated, non-progressive patches of fibrous membrane were formed in the distal region of the implant. The authors attribute the absence of membrane formation to careful preparation of the cement bed and use of pressurized cement injection. The exact congruence of vascularization and remodeling indicates a vascular etiology for the reaction of bone to cemented implantation. Vascular compromise at the time of operation leads to bone necrosis in the affected regions, and subsequent revascularization is a necessary precursor to bone remodeling. Thermal effects and monomer toxicity are considered unimportant.

Animals↗
PubMed1986

The calcar bone graft.

A canine model was developed to investigate the use of an autogeneic iliac bone graft to treat the calcar deficiency commonly found at the time of revision surgery for femoral component loosening. Five large male mixed-breed dogs had bilateral total hip arthroplasty staged at three-month intervals, and were sacrificed at six months. Prior to cementing the femoral component, an experimental calcar defect was made, and a bicortical iliac bone graft was fashioned to fill the defect. Serial roentgenograms showed the grafts had united with no resorption. Technetium-99 bone scans showed more uptake at three months than at six months in the graft region. Disulfine blue injection indicated all grafts were perfused at both three and six months. Thin section histology, fluorochromes, and microradiographs confirmed graft viability in all dogs. Semiquantitative grading of the fluorochromes indicated new bone deposition in 20%-50% of each graft at three months and 50%-80% at six months. Although the calcar bone graft was uniformly successful in this canine study, the clinical application of this technique should be evaluated by long-term results in humans.

Animals↗
PubMed1985

Infection rates in clean surgical procedures: a comparison of ampicillin prophylaxis vs a placebo.

A total of 122 dogs and 7 cats were included in a prospective, randomized, blind trial to determine the frequency of wound infection after clean surgical procedures and to compare the infection rates in dogs and cats given ampicillin (group 1) with those given a placebo (group 2). The 2 groups were similar in terms of mean age, sex ratio, duration of hospital stay, and types of surgical procedures. A wound infection developed in one of the dogs given ampicillin; there were no wound infections in the animals given the placebo. The infection rates in the 2 groups were not significantly different.

Ampicillin↗
PubMed1985

Determination of reference intervals for 10 serum proteins measured by rate nephelometry, taking into consideration different sample groups and different distribution functions.

Reference intervals were established for 10 serum proteins (IgA, IgG, IgM, transferrin, haptoglobin, complement C3, complement C4, alpha 1-acid-glycoprotein, alpha 1-antitrypsin, alpha 2-macroglobulin) measured by rate nephelometry. The reference individuals - 200 blood donors - were divided into 5 subgroups: men aged 19-39 and 40-60 years, women aged 19-39 and 40-60 years and women aged 19-48 years using oral contraceptives. Where possible, two or more subgroups were combined to give reference sample groups. Criteria for this procedure are given. The reference limits of the sample groups were estimated by parametric methods. Assuming that for a specified serum protein the type of distribution is the same in each subgroup, the data were standardized with estimated group specific parameter values and combined into one big sample. This permitted an improved determination of the underlying type of distribution. As a possible form of distribution we also considered the normal distribution truncated on the left side at c greater than or equal to 0. In some cases, after determination of an optimal c, this unusual distribution fitted the data significantly better than the generally used normal or log-normal distribution.

Adult↗