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Biomedical subjects

J M Penrose

Publications and source records attributed to J M Penrose.

12 recordsLinked to original sources
PubMed2000

Computer model analysis of the Swanson and Sutter metacarpophalangeal joint implants.

A representative model which mimics the behaviour of Silastic finger metacarpophalangeal joint implants was constructed using a finite element software package. The modelled implants were moved through a range of flexion, lateral deviation and a combination of both. Pistoning of both implants stems occurred within the modelled medullary cavities. For equivalent flexion angles, the Sutter implant produced a higher stress field than the Swanson implant, and the field was positioned at the central hinge mechanism. In both implants, lateral deviation increased the internal stress concentrations more than when pure flexion was applied. Overall the Swanson style of implant had lower stress magnitudes than the Sutter implant, and it is predicted that the Sutter implant will be more likely to fail than the Swanson. The failure mode for the Sutter implant would be at the central hinge region. The Swanson implant is likely to fail at the central hinge-stem interface regions.

Computer Simulation↗
PubMed2000

A goniometric glove for clinical hand assessment. Construction, calibration and validation.

The construction of a goniometric glove is described. Each of the sensors in the glove was calibrated over a custom built metal hand using blocks of known angles as angular references. The digital data output from each sensor of the glove were converted into angular displacements at each joint. The glove was validated for consistency of measurement and accuracy over a custom built metal jig and in the human hand. The accuracy of the glove was found to be within the limits of traditional goniometry. It is proposed that goniometric gloves could be useful in the assessment of hand function.

Calibration↗
PubMed1999

An impact analysis of a flexible bat using an iterative solver.

Although technology has now infiltrated and prompted evolution in most mass participation sports, the advances in bat technology in such sports as baseball and cricket have been relatively minor. In this study, we used a simple finite element modelling approach to try to shed new light upon the underlying mechanics of the bat-ball impact, with a view to the future optimization of bat design. The analysis of a flexible bat showed that the point of impact that produced the maximum post-impact ball velocity was a function of the bat's vibrational properties and was not necessarily at the centre of percussion. The details of the analysis agreed well with traditional Hertzian impact theory, and broadly with empirical data. An inspection of the relative modal contributions to the deformations during impact also showed that the position of the node of the first flexure mode was important. In conclusion, considerable importance should be attached to the bat's vibrational properties in future design and analysis.

Baseball↗
PubMed1997

In-situ simulation of one-piece metacarpophalangeal joint implants using finite element analysis.

Generally, reconstruction of the rheumatoid metacarpophalangeal (MCP) joint is achieved by means of implantation of a hinged silastic prosthesis. Whereas these implants restore some degree of mobility to the joint, they are prone to failure after a relatively short life-span, and little is known about their dynamical behaviour within the joint. In this study, the Swanson and Sutter designs of MCP implant were examined in an idealized joint environment by means of two-dimensional finite element analysis. The purpose was to assess how the differing geometry affected their behaviour as replacement joints, and whether they were inherently prone to abrasion and high stress concentrations during flexion. The results revealed the changing points of contact between the implant and the bone ends, and clearly showed the implant stems 'pistoning' in the intramedullary canals. This was found to be an effective way to provide preliminary information on the dynamic behaviour of an implant in a simulated joint. This would facilitate further optimization of design in advance of fabrication.

Computer Simulation↗
PubMed1996

The virtual gamma camera room.

The installation of a gamma camera is time-consuming and costly and, once installed, the camera position is unlikely to be altered during its working life. Poor choice of camera position therefore has long-term consequences. Additional equipment such as collimators and carts, the operator's workstation and wall-mounted display monitors must also be situated to maximize access and ease of use. The layout of a gamma camera room can be optimized prior to installation by creating a virtual environment. Super-Scape VRT software running on an upgraded 486 PC microprocessor was used to create a 'virtual camera room'. The simulation included an operator's viewpoint and a controlled tour of the room. Equipment could be repositioned as required, allowing potential problems to be identified at the design stage. Access for bed-ridden patients, operator ergonomics, operator and patient visibility were addressed. The display can also be used for patient education. Creation of a virtual environment is a valuable tool which allows different camera systems to be compared interactively in terms of dimensions, extent of movement and use of a defined space. Such a system also has applications in radiopharmacy design and simulation.

Ergonomics↗
PubMed1976

Effect of sera from immunologically altered mice on phytohemagglutinin-induced mouse lymphocyte transformation.

The DNA-synthetic response of mouse spleen cells to phytohemagglutinin in vitro is depressed by the addition of normal mouse serum. The effects of sera from mice that had been modified immunologically were examined. Increased depressive activity was found in sera from nude mice and from mice recently treated with anti-thymocyte globulin, but no change was found in sera from thymectomized, irradiated, bone marrow-reconstituted mice, nor from lethally or sublethally irradiated or cyclophosphamide-treated mice. Base line DNA synthesis was, however, less inhibited by sera from irradiated or cyclophosphamide-treated mice. Increased depressive activity was found in sera from mice with graft-versus-host reaction and from mice injected with Salmonella enteritidis 11RX, in which macrophage stimulation occurred. Increased depressive activity was also found in the sera of mice injected with sheep erythrocytes. T cells do not appear to be a source of depressive activity but B cells, macrophages and nonlymphoid cells may be sources.

Animals↗
PubMed1975

Further observations on the immunological induction of DNA synthesis in mouse peritoneal macrophages. Role of products of activated lymphocytes.

Subcutaneous injection of ovalbumin (OA) into mice immunized with OA in Freund's complete adjuvant was followed by an increase in the numbers of peritoneal macrophages synthesizing DNA, determined by autoradiography. The effect was immunologically specific. The increase was followed by an increase in the numbers of peritoneal macrophages; the numbers of peritoneal lymphocytes also increased. Injection of OA into immunized or normal mice was followed by a blood monocytosis. Increased DNA synthesis, determined by liquid scintillation counting, occurred in spleen or lymph node cells from immunized mice, cultured with OA. Diluted supernatants from such cultures, injected intravenously into normal mice, caused increases in the numbers of DNA-synthesizing peritoneal macrophages. Similarly, supernatants from concanavalin A stimulated spleen cells, freed of Con A, also caused an increase in DNA-synthesizing macrophages.

Animals↗
PubMed1975

Depressive effect of serum from patients with leprosy on mixed lymphocyte reactions. Influence of anti-leprosy treatment.

Mixed leucocyte cultures, from two normal donors, were set up in media containing human serum from one of the following sources: (a) a pool of normal group AB donors; (b) Chinese, Malay or Indian patients with untreated leprosy; (c) the same patients after effective anti-leprosy treatment; (d) control Chinese, Malay or Indian subjects. Transformation was estimated by measuring the incorporation of tritiated thymidine in the last 24 hr of a 7-day culture period. Transformation was impaired in sera from treated lepromatous patients, but was less impaired or not impaired at all in sera from treated lepromatous patients. The loss of depressive activity after treatment was more marked in Chinese and Indian than in Malay patients. Transformation was also impaired, though to a lesser extent, in sera from patients with untreated tuberculoid leprosy; it was still impaired in sera from treated tuberculoid patients. There was no evidence of specificity in impairment of mixed lymphocyte reactivity and lymphocytotoxic antibodies appeared to play no role. The incidences of hepatitis B antigen and antibody and of anti-nuclear factor were not notably high.

Adolescent↗
PubMedDate not supplied

An examination of one-piece metacarpophalangeal joint implants using finite element analysis.

Reconstruction of the rheumatoid metacarpophalangeal (MCP) joint is generally achieved by means of implantation of a hinged silastic prosthesis. These implants reduce the pain in joint and restore some degree of mobility. However, they are prone to failure after a relatively short life-span. In this study, two popular designs of MCP implant, the Swanson and the Sutter, were compared by means of three-dimensional finite element analysis. The aim was to examine how the differing geometry effected their relative stiffness as replacement joints, and whether they were inherently prone to high stress concentrations during flexion. Although the Swanson design implant exhibited relatively greater resistance to flexion, both designs showed regions of high stress concentration and it was noted that neither was without its limitations. The use of the finite element technique was found to be an excellent way to provide preliminary design evaluation information, allowing further evolution before clinical trials.

Arthritis, Rheumatoid↗