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Biomedical subjects

E A Patterson

Publications and source records attributed to E A Patterson.

6 recordsLinked to original sources
PubMed1992

Breast cancer recurrence after lumpectomy and irradiation: role of mammography in detection.

Between 1977 and 1989, 102 of 1,145 patients treated with lumpectomy and radiation as an alternative to mastectomy required subsequent biopsy for suspected ipsilateral recurrence. The authors reviewed the mammograms of 58 of those patients for whom at least two sets of mammograms were available, including one set obtained within 3 months of the subsequent repeated biopsy. Of 38 biopsy-proved recurrences, 13 (34%) were detected with mammography alone, 17 (45%) with palpation alone, and eight (21%) with both mammography and palpation. While standard mammographic criteria for biopsy were followed, distortions and calcifications inherent to posttreatment appearances necessitated judicious modifications. As anticipated, sensitivities and positive predictive values showed more impairment within the lumpectomy quadrant. In addition, all cases of purely in situ cancer were detected solely with mammography. Mammography plays an important complementary role to physical examination in posttreatment follow-up. On the basis of these findings, a follow-up algorithm for the ongoing evaluation of these patients was developed.

Adult↗
PubMed1992

Theoretical analysis of the fatigue life of fixture screws in osseointegrated dental implants.

Metal fatigue failure of the gold screw used to retain a fixed prosthesis to Brånemark osseointegrated fixtures/abutments has been analyzed theoretically. Mechanical engineering principles show the importance of appropriate preload being applied through the gold screw to the gold cylinder and abutment. The significance of the screw design and necessity of applying the correct torque to achieve a long fatigue life for the screw are also described. The consequence of misalignment of a gold cylinder to an abutment is discussed.

Dental Abutments↗
PubMed1991

A three-dimensional analysis of a bioprosthetic heart valve.

A three-dimensional finite element model of the leaflets of a bicuspid bioprosthetic heart valve is presented. The model is based on a non-linear elastic representation of the tissue behaviour which closely simulates that found in experiments. The geometry of the model is based on measurements from a real valve. Shell elements which permit bending have been used in the analysis. The results indicate that bending stresses in the leaflets make a significant contribution to their deformation. This confirms earlier two-dimensional work which had suggested that analyses, where only membrane stresses were modelled, were likely to produce significant errors in the stress states. The analysis also predicts peak stresses close to, but not at, the attachment of the leaflet to the stent post.

Biomechanical Phenomena↗
PubMed1991

Assessment of osteoporosis at autopsy: mechanical methods compared to radiological and histological techniques.

Osteoporosis is a common problem in the elderly female population and pathological fractures are a frequent complication, but how should the pathologist assess the severity of the disease at autopsy? In this study we have compared subjective, semi-quantitative assessments of rib fracturability, vertebral compressibility, Singh index and histomorphometric methods against a 'gold standard' assessment, namely the force required to fracture the femoral neck. We have shown good correlations between rib fracturability. Singh index and the standard chosen. Poor correlation was shown between histomorphometric techniques and the standard. Our findings suggest that gross rib fracturability is a good indicator of osteoporosis in as far as bone fragility is an indicator of the severity of osteoporosis. However, as the population under examination was small, further studies in this area are clearly warranted in order to extend these findings.

Aged↗
PubMed1990

A two-dimensional finite element analysis of a bioprosthetic heart valve.

A finite element scheme has been developed using total Lagrangian techniques for the two-dimensional analysis of bioprosthetic heart valve leaflets undergoing large deformation. Two models of a leaflet, namely a radial and a circumferential slice, have been analysed. The attachment of the slice to the stent was simulated by progressive contact on a circular former and the coaptation of the leaflets in the centre of a heart valve by a straight line of contact. For the circumferential model, different initial configurations have been considered. The prolapse pressure under which the heart valve closes has been shown to be small in comparison with the normal pressure a heart valve sustains. The regions of the valve that are most heavily stressed are subjected to a strong component of bending. The amount is sensitive to the details of the boundary conditions and to the initial configuration of the valve. These observations are likely to be significant in the use of this kind of stress analysis to improve the design of this type of valve.

Bioprosthesis↗