Biomedical subjects
Publications and source records attributed to T J Joyce.
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Six metacarpophalangeal prostheses were each wear tested to five million cycles. Each prosthesis consisted of a metacarpal component with an approximately hemispherical shell on a titanium body, articulating against a titanium phalangeal component. Four prostheses had a shell made from ultra-high molecular weight polyethylene (UHMWPE) and two had a shell made from polyether ether ketone (PEEK). The tests were undertaken using a finger wear simulator. Despite pre-soaking and the use of control components, lubricant uptake by the metacarpal components was significant. Gravimetrically, the UHMWPE test components showed a greater weight gain than the UHMWPE control components. Therefore there was no apparent wear of any of the UHMWPE test metacarpal components. The original concentric machining marks of the UHMWPE components could still be seen after five million cycles of testing. For the metacarpal components with PEEK shells, gravimetric wear could be measured. Gravimetrically, all of the titanium phalangeal components showed little or no wear. Light scratches in the direction of sliding appeared on the articulating faces of all metacarpal and phalangeal test components, indicating slight abrasive wear.
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Forty-one Sutter metacarpophalangeal prostheses were implanted into 11 hands of nine patients. Twelve of these prostheses were revised from three patients after a mean period of 42 months. Of the 12 prostheses, 11 showed fracture at the junction of the distal stem and the central hinge region. Two Sutter metacarpophalangeal prostheses were tested on a single station finger simulator and both failed due to fracture at the junction of the hinge and the distal stem.
This paper reviews the use of the Swanson finger prosthesis, concentrating on clinical results from the metacarpophalangeal (MCP) joint and modes of prosthetic "failure". While "failure" is generally associated with fracture, it is recognised that fracture does not always necessitate replacement of the Swanson prosthesis. Fracture tends to occur at the junction of the distal stem and hinge of the prosthesis. Initial improvements in ulnar deviation and range of motion (ROM) tend to be gradually reduced over the duration of implantation, and there is little evidence to suggest any long-term improvement in hand strength. Bone erosion and silicone synovitis have been seen but at a much lesser incidence than in other joints implanted with silicone spacers. An evaluation of retrieved Swanson prostheses, tied in with patient history and hand measurements might provide additional information to improve the design of the Swanson prosthesis itself and of other finger prostheses.
This paper highlights the lack of an agreed testing standard for artificial finger joints. It reviews the anatomy, pathology and biomechanics of finger joints as well as the various designs of finger prostheses and the machines used to test them. While pre-implantation testing should be fundamental, increasing regulation of the biomedical engineering industry will further demand testing of prostheses to pre-agreed standards. Standards relating to the testing of other artificial joints are reviewed before possible parameters for testing finger prostheses are offered.
OBJECTIVE: Between 1989 and 1995, expansions in Medicaid eligibility provided publicly financed health insurance to an additional 7 million poor and near-poor children. It is not known whether these expansions affected children's insurance coverage, use of health care services, or health status differently, depending on their race/ethnicity. The objective of this study was to examine, by race/ethnicity, the impact of the recent Medicaid expansions on levels of uninsured individuals, health care service utilization, and health status of the targeted groups of children. METHODS: Using a stratified set of longitudinal data from the National Health Interview Surveys of 1989 and 1995, we compared changes in measures of health insurance coverage, health services utilization, and health status for poor white, black, and Hispanic 1- to 12-year-old children. To control for underlying trends over time, we subtracted 1989 to 1995 changes in these outcomes among nonpoor children from changes among the poor children for each race/ethnicity group. Measures of coverage included uninsured rates and Medicaid rates. Utilization measures included annual probability of visiting a doctor, annual number of doctor visits, and annual probability of hospitalization. Health status measures included self-reported health status and number of restricted-activity days in the 2 weeks before the interview. Differences in means were analyzed with the use of Student's t tests accounting for the clustering sample design of the National Health Interview Surveys. RESULTS: Among poor children between 1989 and 1995, uninsured rates declined by 4 percentage points for whites, 11 percentage points for blacks, and 19 percentage points for Hispanics. Medicaid rates for these groups increased by 16 percentage points, 22 percentage points, and 23 percentage points, respectively. With respect to utilization, the annual probability of seeing a physician increased 7 percentage points among poor blacks and Hispanics but only 1 percentage point among poor whites (not significant) for children in good, fair, or poor health. Among those in excellent or very good health, the respective increases were 1 percentage point for poor whites (not significant), 7 percentage points for poor blacks, and 3 percentage points for poor Hispanics (not significant). Significant increases in numbers of doctor visits per year were recorded only for poor Hispanics who were in excellent or very good health, whereas significant decreases in hospitalizations were recorded for Hispanics who were in good fair or poor health. Measures of health status remained unchanged for poor children over time. The recorded decreases in uninsured rates and increases in Medicaid coverage remained robust to adjustments for underlying trends for all 3 race/ethnicity groups. With respect to adjusted measures of utilization and health status, the only significant differences found were among poor blacks who were in good, fair, or poor health and who registered increases in the likelihood of hospitalization and in poor Hispanics who were in excellent or very good health and who registered decreases in the numbers of restricted-activity days. CONCLUSIONS: Recent expansions in the Medicaid program from 1989 to 1995 produced greater reductions in uninsured rates among poor minority children than among poor white children. Regardless of race/ethnicity, poor children did not seem to experience significant changes during the period of the expansions in either their level of health service utilization or their health status.Medicaid, health insurance, health status, health services.
A dual-cycle finger wear simulator has been designed, manufactured and commissioned. The simulator interspersed dynamic flexion-extension motion under light load with a heavier static 'pinch' load to a test prosthesis immersed in a lubricant heated to 37 degrees C. A validation test was undertaken on a size 2 Swanson prosthesis, leading to prosthesis failure in less than 1 million cycles. A second test was carried out on a Durham metacarpophalangeal prosthesis. After 4.8 million cycles a total wear factor for the joint of 0.60 x 10(-6) mm3/N m was calculated, with no cracks or damage visible. Both test results compare well with earlier tests undertaken on the Stokoe finger wear simulator.
In this paper, we use data from the National Longitudinal Survey of Youth to investigate the empirical link between unintended pregnancy and child health and development. An important contribution of our study is the use of information on siblings to control for unmeasured factors that may confound estimates of the effect of pregnancy intentions on infant and child outcomes. Results from our study indicate that unwanted pregnancy is associated with prenatal and postpartum maternal behaviors that adversely affect infant and child health, but that unwanted pregnancy has little association with birth weight and child cognitive outcomes. Estimates of the association between unwanted pregnancy and maternal behaviors were greatly reduced after controls for unmeasured family background were included in the model. Our results also indicate that there are no significant differences in maternal behaviors or child outcomes between mistimed and wanted pregnancies.
This paper describes the design of a pin on plate rig which has been modified to give multi-directional motion to the test pins, resulting in elliptical and quasi-elliptical wear paths. Such paths are closer to those seen in vivo by a femoral head articulating against an acetabular cup. The description of the rig is augmented by the results of a test of ultra high molecular weight polyethylene pins rubbing against stainless steel plates. with dilute bovine serum at 37 degrees C being used as the lubricant. With standard reciprocating motion, a mean wear factor of 0.085 x 10(-6) mm3/N m was found, but with multi-directional motion, the mean wear factor increased to 1.10 x 10(-6) mm3/N m, which is very similar to in vivo wear factors.
BACKGROUND: Although infant mortality rates have declined gradually in New York City for many years, the rate of that decline began to accelerate dramatically at the end of the 1980s. OBJECTIVE: To analyze the recent accelerated decline in infant mortality for three race/ethnicity designations in New York City and to investigate whether shifts in birth weight distribution or changes in birth weight-specific death rates were more important in determining these declines between 1988 to 1989 and 1992 to 1993. METHODS: Two complete cohorts of linked birth-death certificate files consisting of all live births in New York City in 1988 to 1989 and 1992 to 1993 were examined. For each cohort, separate multinomial logistic regressions were estimated by race/ethnicity to analyze the probability of a neonatal or postneonatal death relative to survival as a function of a spectrum of covariates. The coefficients from these regressions were used to construct direct and indirect standardization exercises to predict changes in infant mortality holding characteristics of the cohort, including birth weight distribution, constant over time, or holding the influence of determinants, including birth weight-specific death rates, constant over time. RESULTS: For whites, Hispanics, and blacks, infant mortality rates declined by 27.4%, 24.8%, and 22.7%, respectively, between 1988 to 1989 and 1992 to 1993. For whites and blacks, the largest decreases occurred for neonatal mortality rates, whereas for Hispanics, postneonatal rates fell the greatest. Although infant mortality rates among very low birth weight infants (<1500 g) fell by 27.8%, 19.3%, and 16.6% for whites, Hispanics, and blacks, the greatest decreases in rates were seen among normal birth weight infants (>2500 g). Infant mortality rate declines for this category of infants reached 31%, 31.7%, and 31.3%, respectively, for whites, Hispanics, and blacks. Direct and indirect standardization exercises indicated that the most important factor in determining these declines were decreases in birth weight-specific death rates, not improvements in the birth weight distribution over time. CONCLUSIONS: We conclude that the large decreases in infant mortality rates witnessed in New York City between 1988 to 1989 and 1992 to 1993 were attributable not to improvements in birth weight distribution of the population but to declines in birth weight-specific death rates and that normal birth weight infants showed the greatest improvement.
Cross-linked polyethylene (XLPE) may have an application as a material for an all-plastic surface replacement finger joint. It is inexpensive, biocompatible and can be injection-moulded into the complex shapes that are found on the ends of the finger bones. Further, the cross-linking of polyethylene has significantly improved its mechanical properties. Therefore, the opportunity exists for an all-XLPE joint, and so the wear characteristics of XLPE sliding against itself have been investigated. Wear tests were carried out on both reciprocating pin-on-plate machines and a finger function simulator. The reciprocating pin-on-plate machines had pins loaded at 10 N and 40 N. All pin-on-plate tests show wear factors from the plates very much greater than those of the pins. After 349 km of sliding, a mean wear factor of 0.46 x 10(-6) mm3/N m was found for the plates compared with 0.021 x 10(-6) mm3/N m for the pins. A fatigue mechanism may be causing this phenomenon of greater plate wear. Tests using the finger function simulator give an average wear rate of 0.22 x 10(-6) mm3/N m after 368 km. This sliding distance is equivalent to 12.5 years of use in vivo. The wear factors found were comparable with those of ultra-high molecular weight polyethylene (UHMWPE) against a metallic counterface and, therefore, as the loads across the finger joint are much less than those across the knee or the hip, it is probable that an all-XLPE finger joint will be viable from a wear point of view.
Wear tests were carried out on reciprocating pin-on-plate machines which had pins loaded at 10 N and 40 N. The materials tested were irradiated cross-linked polyethylene sliding against itself, irradiated ultra-high molecular weight polyethylene sliding against itself and non-irradiated ultra-high molecular weight polyethylene sliding against itself. After 153.5 km of sliding, the non-irradiated ultra-high molecular weight polyethylene plates and pins showed mean wear factors under 10 N loads, or a nominal contact stress of 0.51 MPa, of 84.0 x 10(-6) mm3/N m for the plates and 81.3 x 10(-6) mm3/N m for the pins. Under 40 N loads, or a nominal contact stress of 2.04 MPa, the non-irradiated ultra-high molecular weight polyethylene pins sheared at 22.3 km. At the last measurement point prior to this failure, 19.1 km, wear factors of 158 x 10(-6) mm3/N m for the plates and 85.0 x 10(-6) mm3/N m for the pins had been measured. After 152.8 km. the irradiated ultra-high molecular weight polyethylene plates and pins showed mean wear factors under 10 N loads of 59.8 x 10(-6) mm3/N m for the plates and 31.1 x 10(-6) mm3/N m for the pins. In contrast, after 150.2 km, a mean wear factor of 0.72 x 10(-6) mm3/N m was found for the irradiated cross-linked polyethylene plates compared with 0.053 x 10(-6) mm3/N m for the irradiated cross-linked polyethylene pins.
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Antisera were raised towards the putative N-terminal sequence of the canine precursor to neurotensin (NT) and neuromedin N (NMN), residues 24-35 in the pre-prohormone, as well as its C-terminal TAIL, residues 164-170. These were used in conjunction with previously developed immunoassays towards NT and NMN to characterize the precursor and to study its processing in feline brain, heart, adrenal and intestine. The precursor was identified as a 18 kDa protein that reacted with both the N- and C-terminal antisera and yielded NT3-13 and NT4-13 upon treatment with pepsin. It represented 5-10% of the NT activity in ileum. Processing was found to be tissue-specific, yielding primarily NT, NMN and TAIL in most tissues but also giving rise to N-terminally extended forms of these peptides, which were particularly evident in extracts of adrenal and intestine. Two of the four molecular forms detected using the TAIL immunoassay were tenatively identified as NT-TAIL and Gly-Ser-Tyr-Tyr-Tyr based upon chromatographic evidence. Western blotting indicated that ileal extracts contained large molecular forms of NT (17 kDa) and NMN (16 kDa), whereas brain extracts contained primarily the N-terminal of the precursor without NT and NMN attached (14.3 kDa). It was concluded that the structure of the feline precursor in its N- and C-terminal regions, and the positioning of the signal peptide cleavage site were as predicted from cDNA work in the dog. On the other hand, processing of the precursor was complex, occurring in a tissue-specific manner.
Substance-P (SP) and its metabolites, SP-(1-7) and SP-(5-11), were quantitated in arthritic synovial fluids and plasma using a validated procedure. This process involved collection into appropriate enzyme inhibitors, extraction with acid-acetone, high pressure liquid chromatography, and RIA using region-specific antisera. Our results demonstrate that the levels of authentic SP in these fluids are less than 3.5 pmol/L, which is 50- to 10,000-fold less than those previously reported by others. These discrepant findings were not attributable to degradation, because added SP was recovered in good yield, and the measured levels of the metabolites SP-(1-7) and SP-(5-11) were also extremely low. In search of an explanation, we noted that many of the earlier reports involved direct assay of these fluids (without extraction and chromatography). Further work indicated that proteolytic enzymes (e.g. protease 24.11) present in these unextracted fluids can give rise to artifactually high SP measurements. We conclude that if SP is released within the joint space and if it participates in the inflammatory reaction and/or healing process, it most likely does so in a local fashion, which would not involve its accumulation in synovial fluid or plasma.
In this paper we estimate the impact on adolescent childbearing of the liberalization of the New York State abortion law in 1970. Using Box-Jenkins time series techniques to analyze monthly data on the number of births to White and Black adolescents from January 1963 to December 1987, we found that the level of births to Black adolescents living in New York City fell 18.7 percent, approximately 142 fewer births per month, after the law became effective; the level of White births fell 14.1 percent, approximately 111 fewer births per month. Projections based on the fitted model suggest that a ban on legalized abortion today would have a major impact on adolescent childbearing in New York City as well as other parts of the country, although the magnitude of the change would vary according to local conditions.