Chlamydia pneumoniae in atherosclerotic tissue

The majority of almost 30 publications from 1992 to 1999 describe Chlamydia pneumoniae organisms in atherosclerotic lesions of various major arteries. In the first study in the United Kingdom, C. pneumoniae was found in the aorta and femoral and iliac arteries. In a subsequent study, the organism was detected in arteries of subjects as young as 15 years. In a collaborative investigation, 71% of atheromatous arteries taken at autopsy from white South African subjects were C. pneumoniae positive compared with 9% of nonatheromatous arteries. Of interest, the organisms were detected in 67% of vessels that showed only early atherosclerotic lesions (fatty streaks). C. pneumoniae was also found in the ruptured coronary artery plaque of a black South African who died of myocardial infarction, a rare event. The presence of C. pneumoniae organisms within foam and smooth muscle cells of atherosclerotic plaques is beyond doubt, but their role in atherosclerosis remains enigmatic.

Early diagnosis of lymphedema in postsurgery breast cancer patients

Lymphedema is an accumulation of lymph fluid in the limb resulting from an insufficiency of the lymphatic system. It is commonly associated with surgical or radiotherapy treatment for breast cancer. As with many progressively debilitating disorders, the effectiveness of treatment is significantly improved by earlier intervention. Multiple frequency bioelectrical impedance analysis (MFBIA) previously was shown to provide accurate relative measures of lymphedema in the upper limb in patients after treatment for breast cancer. This presentation reports progress to date on a three-year prospective study to evaluate the efficacy of MFBIA to predict the early onset of lymphedema in breast cancer patients following treatment. Bioelectrical impedance measurements of each upper limb were recorded in a group of healthy control subjects (n = 50) to determine the ratio of extracellular limb-fluid volumes. From this population, the expected normal range of asymmetry (99.7% confidence) between the limbs was determined. Patients undergoing surgery to treat breast cancer were recruited into the study, and MFBIA measurements were recorded presurgery, at one month and three months after surgery, and then at two-month intervals for up to 24 months postsurgery. When patients had an MFBIA measure outside the 99.7% range of the control group, they were referred to their physician for clinical assessment. Results to date: Over 100 patients were recruited into the study over the past two years; at present, 19 have developed lymphedema and, of these, 12 are receiving treatment. In each of these 19 cases, MFBIA predicted the onset of the condition up to four months before it could be clinically diagnosed. The false-negative rate currently is zero. The study will continue to monitor patients over the remaining year to accurately ascertain estimates of specificity and sensitivity of the procedure.

Comparison of whole body and segmental bioimpedance methodologies for estimating total body water

We compared the whole body (WB) and segmental bioelectrical impedance analysis (BIA) methodologies in a group of healthy adults (n = 25). It has been suggested that the segmental methodology may overcome the difficulty in generating a single algorithm to predict total body water (TBW) in all groups whether healthy or not. We measured TBW, using D2O dilution, and WB and segmental BIA parameters. Cole-Cole analysis was used to determine the impedance at the characteristic frequency (Zc). The correlation between TBW (by D2O dilution) and segmental BIA measures (multiple regression, r = 0.90, p < 0.001, SEE = 3.1 L) was not significantly higher than the correlation between TBW (D2O dilution) and WB BIA measures (simple regression, r = 0.85, p < 0.001, SEE = 3.6 L). Others have observed this "lack of improvement" in a group of healthy subjects. The true value of the segmental BIA methodology may lie in applications involving groups with altered distributions of segmental and compartmental fluid.

KRN2391: dual action on rat pulmonary artery and no loss of potency in pulmonary hypertension

1. The pulmonary vasorelaxant properties of KRN2391 (N-cyano-N'-(2-nitroxyethyl)-3-pyridinecarboximidamide) were examined in isolated ring preparations of main (MPA) and intralobar (IPA) pulmonary artery from control and pulmonary hypertensive rats (exposure to hypoxia, 10% oxygen, for 1 week). 2. On both MPA and IPA, pulmonary vasorelaxant responses were inhibited by methylene blue (10 micromol/L) or glibenclamide (1 or 10 micromol/L). Thus, KRN2391 has the properties of both a nitric oxide (NO) donor and a K(ATP) channel opener on rat pulmonary arteries. 3. KRN2391 was more potent and gave a greater maximum relaxation on MPA (-log EC(50) 6.47; maximum 92% reversal of induced contraction) than on IPA (-log EC(50) 6.09; maximum 58% reversal of induced contraction). Comparable differences between MPA and IPA were seen for SIN-1 (NO donor) and levcromakalim (K(ATP) channel opener). 4. KRN2391 was equipotent in MPA from control and pulmonary hypertensive rats but, when glibenclamide (10 micromol/L) was present, KRN2391 was six-fold less potent in preparations from pulmonary hypertensive than control rats. An eight-fold reduction in potency was seen for SIN-1 (no glibenclamide) in arteries from pulmonary hypertensive rats, confirming previous findings with other NO donors. 5. It is concluded that the dual mechanism of action of KRN2391 accounts for the finding that this drug is equally potent in pulmonary arteries from pulmonary hypertensive and control rats. In the context of pulmonary hypertension, this property of the drug could give it an advantage over drugs that act solely as NO donors because these decline in potency, at least in animal models of this disease.

Nutritional status of children with cystic fibrosis measured by total body potassium as a marker of body cell mass: lack of sensitivity of anthropometric measures

OBJECTIVE

To investigate measures aimed at defining the nutritional status of cystic fibrosis (CF) populations, this study compared standard anthropometric measurements and total body potassium (TBK) as indicators of malnutrition.

METHODS

Height, weight, and TBK measurements of 226 children with CF from Royal Children's Hospital, Brisbane, Australia, were analyzed. Z scores for height for age, weight for age, and weight for height were analyzed by means of the National Centre for Health Statistics reference. TBK was measured by means of whole body counting and compared with predicted TBK for age. Two criteria were evaluated with respect to malnutrition: (1) a z score < -2.0 and (2) a TBK for age <80% of predicted.

RESULTS

Males and females with CF had lower mean height-for-age and weight-for-age z scores than the National Centre for Health Statistics reference (P <.01), but mean weight-for-height z score was not significantly different. There were no significant gender differences. According to anthropometry, only 7.5% of this population were underweight and 7.6% were stunted. However, with TBK as an indicator of nutritional status, 29.9% of males and 22.0% of females were malnourished.

CONCLUSION

There are large differences in the percentage of patients with CF identified as malnourished depending on whether anthropometry or body composition data are used as the nutritional indicator. At an individual level, weight-based indicators are not sensitive indicators of suboptimal nutritional status in CF, significantly underestimating the extent of malnutrition. Current recommendations in which anthropometry is used as the indicator of malnutrition in CF should be revised.

The accuracy of assessing total hip arthroplasty outcomes: a prospective correlation study of walking ability and 2 validated measurement devices

The Western Ontario and McMaster University Osteoarthritis Index (WOMAC) and the SF-36 are used to assess subjective outcome after total hip arthroplasty (THA). Although these indices have been validated, neither the WOMAC nor the SF-36 has been tested for accuracy against objective data in this clinical setting. Thirty osteoarthritic patients undergoing elective primary THA were subjectively evaluated preoperatively and 1 year postoperatively with the WOMAC and the SF-36 and objectively evaluated at the same interval with basic stride analysis and the 6-minute walk test. Correlation analysis of the subjective and objective data (both perioperative improvement and postoperative absolute scores) yielded Pearson coefficients of r = 0.50-0.81. This work demonstrates a sound statistical relationship between walking ability and the functional aspects of the WOMAC and the SF-36, supporting the use of these instruments in assessing the functional outcome after THA.

Pharmaceutical and biological properties of poly(amino acid)/DNA polyplexes

Physicochemical properties of polyplexes formed between pRSVlacZ and poly(amino acid)s were investigated as a paradigm of more complex, synthetic virus-like, DNA delivery systems, that are of interest to many gene delivery laboratories. We observed the interaction between polymer and DNA using ethidium exclusion, and determined the size distributions and the zeta potentials of polyplexes. We correlated these properties with their fundamental interactions with cultured B16 murine melanoma cells, and the resulting efficiency of transfection. A variety of poly(amino acid)s each condensed DNA to produce particles with mean hydrodynamic diameters of approximately 100 nm (a typical span of a population was 80-120nm). Poly(amino acid) polyplexes were unstable in electrolyte solutions such as cell culture media. The apparent particle size increased in electrolyte, depending on the charge ratio, to diameters up to 700 nm. This was thought to be due to aggregation, since neutral particles were most sensitive. When the charge ratio (+/-) exceeded unity polyplexes had positive zeta potentials (which peaked at approximately +30 mV), bound non-specifically to cells, were internalised and in the presence of an endosomolytic agent were able to transfect cells. Though all cationic poly(amino acid)s investigated formed polyplexes with similar physical properties, their biological properties were significantly different. Polyplexes prepared with poly-L-ornithine were the most effective transfection agents, but poly(lys-co-ala, 1: 1) systems appeared to be inactive. This may reflect the differences in uncoupling of DNA and polymer, which is expected to be necessary for passage through the nuclear pore. Uncoupling of polycation and DNA was investigated by exposing the complexes to dextran sulphate. Release of DNA was detected by increased fluorescence at 600 nm in the presence of ethidium. Release of DNA was incomplete from polyplexes formed with high molecular weight polylysine. This may explain the lower levels of transfection observed with high molecular weight polylysine. The significance of these observations for design of advanced non-viral gene delivery systems is discussed.

Estimation of cumulative lead releases (lead flux) from the maternal skeleton during pregnancy and lactation

Recent longitudinal studies with human subjects and nonhuman primates using high-precision stable lead isotopes show that lead is mobilized from the maternal skeleton during pregnancy and the postpartum period. We have now calculated the cumulative lead release (lead flux in micrograms) mobilized from the skeleton during these periods by means of analysis of monthly PbB samples from recent immigrants to Australia. Results included a statistically significant inverse relationship (P = .006) between the lead flux and the time of conception after the arrival of the subjects in Australia. By using an area-under-the-curve approach to determine the added lead inputs to blood during pregnancy and nursing versus a baseline value, the net lead release to blood varied from 0.9 to 10.1 microg/d, which is equivalent to 0.3 to 4.03 mg of lead. With group PbB concentrations usually less than 3 microg/dL, the observed releases imply a high skeletal turnover of greater than 10% and possibly greater than 30% in some subjects during pregnancy and the postpartum period. These elevated rates in some subjects may partly arise from low daily calcium intakes, being one half to two thirds of that of recommended daily requirements. The lead flux calculated from a cumulative approach was compared with other approaches: first-order kinetics, bone turnover, bone x-ray fluorescence measurements, and the International Commission for Radiological Protection lead pharmacokinetic model. Calculated lead releases and remaining bone lead concentrations would likely not be detectable by current x-ray fluorescence methods.

Multiple frequency bioelectrical impedance analysis: a cross-validation study of the inductor circuit and Cole models

It has been proposed that multiple frequency bioelectrical impedance models of the human body should include an inductive property for the circulatory system, the inductor circuit model (ICM), and that such a model, when coupled with a new method of data analysis, can improve the predictive power of multiple frequency bioelectrical impedance analysis (MFBIA). This hypothesis was tested using MFBIA measurements and gold standard measures of total body and extracellular water volumes in a cross-validation study in two subject groups (viz. controls and HIV). The MFBIA measurements were analysed using the current, widely accepted Cole model and the alternative ICM model which includes an inductive component. Correlations in the range 0.75 to 0.92 (for TBW) and 0.46 to 0.79 (for ECW) for impedance quotients versus gold standard measures within the subject groups were observed. These decreased, to as low as r = 0.50 for TBW and r = 0.29 for ECW, when the derived algorithms were applied to the alternative subject group. These results suggest that lack of portability of MFBIA algorithms between subject groups is not due to an inadequacy of the analogue circuit model per se but is possibly due more to fundamental flaws in the principles associated with its application. These include assuming a constant proportionality of body segment geometries and tissue fluid resistivities. This study has also demonstrated that this inadequacy cannot be overcome by simply introducing an inductive component into the analogue electrical circuit.

Sensitivity of multiple frequency bioelectrical impedance analysis to changes in ion status

Bioelectrical impedance analysis has found extensive application as a simple noninvasive method for the assessment of body fluid volumes. The measured impedance is, however, not only related to the volume of fluid but also to its inherent resistivity. The primary determinant of the resistivities of body fluids is the concentration of ions. The aim of this study was to investigate the sensitivity of bioelectrical impedance analysis to bodily ion status. Whole body impedance over a range of frequencies (4-1012 kHz) of rats was measured during infusion of various concentrations of saline into rats concomitant with measurement of total body and intracellular water by tracer dilution techniques. Extracellular resistance (R0), intracellular resistance (R(i)) and impedance at the characteristic frequency (Z(c)) were calculated. R0 and Z(c) were used to predict extracellular and total body water respectively using previously published formulae. The results showed that whilst R0 and Z(c) decreased proportionately to the amount of NaCl infused, R(i) increased only slightly. Impedances at the end of infusion predicted increases in TBW and ECW of approximately 4-6% despite a volume increase of less than 0.5% in TBW due to the volume of fluid infused. These data are discussed in relation to the assumption of constant resistivity in the prediction of fluid volumes from impedance data.

Australian isolates of ryegrass mosaic rymovirus and their relationships

The sequences of the 3'-terminal 1.8 kb of the genomes of three Australian and three Welsh isolates of ryegrass mosaic rymovirus (RGMV) were determined, as too were the virion protein genes of two New Zealand isolates of RGMV. They were compared with each other and with the published sequences of a Danish and a South African isolate by distance and maximum likelihood methods, and found to be very closely related (mean nucleotide difference 5.5%). All three Australian isolates and one from North Island of New Zealand formed one consistent cluster, and the Danish and South African isolates formed another. However the relationships between these two clusters and the other isolates were not consistent; they depended on the method of comparison used, and on the protein, gene or codon position compared. Nonetheless the European (Welsh and Danish) sequences were 2-4 times more different from one another than those from the Antipodes, suggesting that the European RGMV population may be older than the Antipodean. The Danish isolate has 39 nucleotides of the 5'-terminal region of its virion protein gene frameshifted -1 relative to the 'common' sequence. Interestingly the South African isolate has a similar frameshift, but sequence comparisons indicate that this frameshift must have occurred independently; a possible example of 'convergent frameshifting'.

Optimizing electrode sites for segmental bioimpedance measurements

Recent advances in the application of bioelectrical impedance analysis (BIA) have indicated that a more accurate approach to the estimation of total body water is to consider the impedance of the various body segments rather than simply that of the whole body. The segmental approach necessitates defining and locating the physical demarcation between both the trunk and leg and the trunk and arm. Despite the use of anatomical markers, these points of demarcation are difficult to locate with precision between subjects. There are also technical problems associated with the regional dispersion of the current distribution from one segment (cylinder) to another of different cross-sectional area. The concept of equipotentials in line with the proximal aspects of the upper (and lower) limbs along the contralateral limbs was investigated and, in particular, the utility of this concept in the measurement of segmental bioimpedance. The variation of measured segmental impedance using electrode sites along these equipotentials was less than 2.0% for all of the commonly used impedance parameters. This variation is approximately equal to that expected from biological variation over the measurement time. It is recommended that the electrode sites, for the measurement of segmental bioelectrical impedance in humans, described herein are adopted in accordance with the proposals of the NIH Technology Assessment Conference Statement.

A fly's eye view of biology

Determining how genes function in developmentally complex multicellular organisms can be a formidable task. Obstacles arise from the fact that inactivation of most genes results in subtle or undetectable phenotypic alterations, and when phenotypes are observed they are often difficult to interpret because most genes play multiple roles in development. New techniques that have been applied to studying genes in the developing Drosophila eye promise to circumvent these obstacles. The advent of these techniques combined with the existing wealth of information about cellular pattern formation in the Drosophila eye make the eye a powerful model system for deciphering the function of genes in biological processes.

Bioimpedance: is it a predictor of true water volume?

Bioelectrical impedance analysis (BIA) has been reported to be insensitive to changes in water volumes in individual subjects. This study was designed to investigate the effect on the intra- and extracellular resistances (Ri and Re) of the segments of subjects for whom body water was changed without significant change to the total amount of electrolyte in the respective fluids. Twelve healthy adult subjects were recruited. Ri and Re of the leg, trunk, and arm of the subjects were determined from BIA measures prior to commencement of two separate studies that involved intervention, resulting in a loss/gain of body water effected either by a sauna followed by water intake (study 1) or by ingestion (study 2). Ri and Re of the segments were also determined at a number of times following these interventions. The mean change in body water, expressed as a percentage of body weight, was 0.9% in study 1 and 1.25% in study 2. For each study, the results for each subject were normalized for each limb to the initial (prestudy) value and then the normalized results for each segment were pooled for all subjects. ANOVA of these pooled results failed to demonstrate any significant differences between the normalized mean values of Ri or Re of the segments measured through the course of each study. The failure to detect a change in Ri or Re is explained in terms of the basic theory of BIA.

Chlamydia pneumoniae in atheroma: consideration of criteria for causality

AIMS

(1) To seek evidence of the existence of Chlamydia pneumoniae in a spectrum of atheromatous lesions in different types of arteries from individuals of different ages, using a polymerase chain reaction (PCR) assay supported by electron microscopy and immunocytochemistry; (2) to use electron microscopy to examine interactions between C pneumoniae and the cells present in the arterial tissue; (3) to assess the extent to which the data fulfil the criteria for causality.

METHODS

At necropsy examination, 35 arterial specimens were taken from 25 subjects. The grade of atheroma was determined macroscopically and microscopically and the tissues coded and examined by the three techniques.

RESULTS

Of the 35 specimens, 24 had macroscopic or microscopic atheromatous lesions of varying degree. Twenty two of the 35 specimens were examined by electron microscopy, C pneumoniae-like bodies being found in 11 (50%); seven specimens were examined by the immunocytochemical method, positive staining being detected in three; and all specimens were examined by the PCR technique, 15 (43%) being PCR positive. Overall, of the 24 specimens with lesions, 17 (71%) were positive by at least one of the three tests, whereas of the 11 specimens without lesions, only one was positive. The positive specimens comprised 10 of 19 aortas, three of six iliac arteries, and one coronary and one pulmonary artery. C pneumoniae was detected in four of six specimens in which there were early changes and in a 20 year old subject. Concerning the 25 subjects, of 17 who had atheromatous arteries, 14 (82%) were C pneumoniae positive and of the eight who had normal arteries, none was positive.

CONCLUSIONS

There is a strong correlation between C pneumoniae and arterial atheromatous lesions. The organism may contribute to the disease process by damaging smooth muscle cells.

Quantification of Chlamydia trachomatis in cervical and urine specimens from women attending a genitourinary medicine clinic: implications for screening strategies

Population screening and intervention programmes can reduce the prevalence and incidence of infection with Chlamydia trachomatis, especially if sensitive molecular diagnostic tests are used. However, diagnostic tests that perform well on genitourinary medicine (GUM) clinic populations may be less useful for screening, particularly if the majority of infected subjects are asymptomatic and their samples contain fewer organisms. We have compared the extent of low organism load in cervical and urine samples from symptomatic and asymptomatic chlamydia-positive women, by using a direct fluorescent antibody staining method and counting the chlamydial elementary bodies (EBs). We have investigated the ability of an enzyme immunoassay (EIA; MicroTrak) and a DNA amplification (ligase chain reaction; LCR) assay to detect low numbers of organisms in cervical samples and the ability of the LCR assay to detect low numbers of organisms in urine. A low organism load (< 10 EBs) was seen by direct fluorescent antibody (DFA) staining in about 30% of cervical samples and in about 75% of urines from chlamydia-positive women; the proportions in symptomatic women were not significantly different from those in asymptomatic women. The EIA identified only 16% of cervical samples that contained < 10 EBs by DFA staining; the LCR identified 100% of cervical samples and 93% of urine samples that contained < 10 EBs by DFA staining. The findings suggest that the ability of chlamydial diagnostic tests to identify positive women should be similar among patients attending a GUM clinic and those taking part in a population screening programme, and that sensitive molecular assays such as the LCR should identify subjects with a low organism load in both groups.

Bioimpedance spectrometry in the determination of body water compartments: accuracy and clinical significance

Bioelectrical impedance analysis (BIA) offers the potential for a simple, portable and relatively inexpensive technique for the in vivo measurement of total body water (TBW). The potential of BIA as a technique of body composition analysis is even greater when one considers that body water can be used as a surrogate measure of lean body mass. However, BIA has not found universal acceptance even with the introduction of multi-frequency BIA (MFBIA) which, potentially, may improve the predictive accuracy of the measurement. There are a number of reasons for this lack of acceptance, although perhaps the major reason is that no single algorithm has been developed which can be applied to all subject groups. This may be due, in part, to the commonly used wrist-to-ankle protocol which is not indicated by the basic theory of bioimpedance, where the body is considered as five interconnecting cylinders. Several workers have suggested the use of segmental BIA measurements to provide a protocol more in keeping with basic theory. However, there are other difficulties associated with the application of BIA, such as effects of hydration and ion status, posture and fluid distribution. A further putative advantage of MFBIA is the independent assessment not only of TBW but also of the extracellular fluid volume (ECW), hence heralding the possibility of being able to assess the fluid distribution between these compartments. Results of studies in this area have been, to date, mixed. Whereas strong relationships of impedance values at low frequencies with ECW, and at high frequencies with TBW, have been reported, changes in impedance are not always well correlated with changes in the size of the fluid compartments (assessed by alternative and more direct means) in pathological conditions. Furthermore, the theoretical advantages of Cole-Cole modelling over selected frequency prediction have not always been apparent. This review will consider the principles, methodology and applications of BIA. The principles and methodology will be considered in relation to the basic theory of BIA and difficulties experienced in its application. The relative merits of single and multiple frequency BIA will be addressed, with particular attention to the latter's role in the assessment of compartmental fluid volumes.

Bioimpedance spectrometry in the determination of body water compartments: accuracy and clinical significance

Bioelectrical impedance analysis (BIA) offers the potential for a simple, portable and relatively inexpensive technique for the in vivo measurement of total body water (TBW). The potential of BIA as a technique of body composition analysis is even greater when one considers that body water can be used as a surrogate measure of lean body mass. However, BIA has not found universal acceptance even with the introduction of multi-frequency BIA (MFBIA) which, potentially, may improve the predictive accuracy of the measurement. There are a number of reasons for this lack of acceptance, although perhaps the major reason is that no single algorithm has been developed which can be applied to all subject groups. This may be due, in part, to the commonly used wrist-to-ankle protocol which is not indicated by the basic theory of bioimpedance, where the body is considered as five interconnecting cylinders. Several workers have suggested the use of segmental BIA measurements to provide a protocol more in keeping with basic theory. However, there are other difficulties associated with the application of BIA, such as effects of hydration and ion status, posture and fluid distribution. A further putative advantage of MFBIA is the independent assessment not only of TBW but also of the extracellular fluid volume (ECW), hence heralding the possibility of being able to assess the fluid distribution between these compartments. Results of studies in this area have been, to date, mixed. Whereas strong relationships of impedance values at low frequencies with ECW, and at high frequencies with TBW, have been reported, changes in impedance are not always well correlated with changes in the size of the fluid compartments (assessed by alternative and more direct means) in pathological conditions. Furthermore, the theoretical advantages of Cole-Cole modelling over selected frequency prediction have not always been apparent. This review will consider the principles, methodology and applications of BIA. The principles and methodology will be considered in relation to the basic theory of BIA and difficulties experienced in its application. The relative merits of single and multiple frequency BIA will be addressed, with particular attention to the latter's role in the assessment of compartmental fluid volumes.

A comparison of segmental and wrist-to-ankle methodologies of bioimpedance analysis

The common approach of bioelectrical impedance analysis to estimate body water uses a wrist-to-ankle methodology which, although not indicated by theory, has the advantage of ease of application particularly for clinical studies involving patients with debilitating diseases. A number of authors have suggested the use of a segmental protocol in which the impedances of the trunk and limbs are measured separately to provide a methodology more in keeping with basic theory. The segmental protocol has not, however, been generally adopted, partly because of the increased complexity involved in its application, and partly because studies comparing the two methodologies have not clearly demonstrated a significant improvement from the segmental methodology. We have conducted a small pilot study involving ten subjects to investigate the efficacy of the two methodologies in a group of normal subjects. The study did not require the independent measure of body water, by for example isotope dilution, as the subjects were maintained in a state of constant hydration with only the distribution between limbs and trunk changing as a result of change in posture. The results demonstrate a significant difference between the two methodologies in predicting the expected constancy of body water in this study, with the segmental methodology indicating a mean percentage change in extracellular water of -2.2%, which was not significantly different from the expected null result, whereas the wrist-to-ankle methodology indicated a mean percentage change in extracellular water of -6.6%. This is significantly different from the null result, and from the value obtained from the segmental methodology (p = 0.006). Similar results were obtained using estimates of total body water from the two methodologies.

Effect of temperature and sweating on bioimpedance measurements

The effect of skin temperature and hydration status has been suggested by some researchers as a common cause of variation in bioimpedance measurements of the body. This paper details a simple method of measuring the transverse impedance of the skin. The measured resistance and reactance was found to decrease by 35% and 18% for an increase of 20 degrees C. Similarly a decrease in resistance and reactance of 20% and 25% respectively was detected after hydration of the skin. However, the changes in skin temperature and hydration were found to have no significant effect on the whole body bioimpedance measurements using the standard tetra-polar electrode technique.

Polycation-DNA complexes for gene delivery: a comparison of the biopharmaceutical properties of cationic polypeptides and cationic lipids

DNA plasmids formed particulate complexes with a variety of cationic polyamino acids and cationic lipids, which were used to transfect mammalian cells in culture. Complexation was studied by assaying for exclusion of ethidium using a fluorometric assay, which indicated that complexation with cationic polyamino acids took place with utilisation of the majority of charged functional groups. The particle sizes and zeta potentials of a range of complexes were determined. Generally polyamino acids formed uniform particles 80-120 nm in diameter in water, but their particle size increased on dilution of the particles in electrolytes or cell culture media. The efficiency of transfection was compared using complexes of pRSVlacZ, a reporter construct which expressed beta-galactosidase under the control of the Rous sarcoma virus promoter. Positively charged DNA/polyamino acid complexes were taken up by cells but required an endosomolytic agent, such as chloroquine, to facilitate transfection. Polyornithine complexes resulted in the highest levels of expression, in comparison with other homopolyamino acids (polyornithine>poly-L-lysine=poly-D-lysine>polyarginine). Copolyamino acids of lysine and alanine condensed DNA but were less active in transfection experiments. Copoly(L-Lys, L-Ala 1:1) was inactive even in the presence of chloroquine. In contrast DNA/cationic lipid complexes transfected cells spontaneously, and chloroquine did not improve the extent of expression, rather it usually reduced efficiency. There was little correlation between comparative efficiencies of lipid complexes between cell lines suggesting that the nature of the cell membrane and differences in mechanisms of internalisation were determinants of efficiency. In an effort to explore better cell culture models for gene delivery, monolayers of Caco-2 cells were transfected in filter culture. As the cells differentiated and formed a polarized monolayer, expression of beta-galactosidase was reduced until at day 27 expression was not significantly different from basal activity. The Caco-2 filter culture model merits further attention as a model of gene delivery to epithelial surfaces, such as would be encountered in the lung after inhalation.

Sensitivity of the ligase chain reaction assay for detecting Chlamydia trachomatis in vaginal swabs from women who are infected at other sites

OBJECTIVE

To assess the sensitivity of the ligase chain reaction (LCR) assay for Chlamydia trachomatis in vaginal swabs from women who were positive in cervical samples and/or urines.

SUBJECTS

413 women attending the genitourinary medicine clinic, St. Mary's Hospital, Paddington.

METHODS

The LCR assay was used to test vaginal swabs from 46 women who were C trachomatis positive at one or both of the other sites by direct fluorescent antibody (DFA) staining, by an enzyme immunoassay (EIA), or by the LCR assay.

RESULTS

The LCR assay of vaginal swabs had the following sensitivity values using confirmed positive results: 93% (41/44) compared with DFA staining of cervical deposits, 93% (41/44) compared with the LCR assay of cervical samples, 93% (28/30) compared with an EIA for cervical samples, 91% (39/43) compared with DFA staining of urine deposits, and 93% (39/42) compared with the LCR assay of urine. Four women had vaginal swab samples negative by the LCR assay; one was positive only in the urine and two had cervical samples containing a small number of chlamydial elementary bodies.

CONCLUSION

Testing vaginal swabs by the LCR assay is a sensitive method of detecting chlamydial infection; the results suggest that this procedure could be used as an alternative to examining urines in a screening programme for chlamydial infection in the community.

Prediction of the chemical composition of lamb carcasses from multi-frequency impedance data

Multi-frequency bioimpedance analysis (MFBIA) was used to determine the impedance, reactance and resistance of 103 lamb carcasses (17.1-34.2 kg) immediately after slaughter and evisceration. Carcasses were halved, frozen and one half subsequently homogenized and analysed for water, crude protein and fat content. Three measures of carcass length were obtained. Diagonal length between the electrodes (right side biceps femoris to left side of neck) explained a greater proportion of the variance in water mass than did estimates of spinal length and was selected for use in the index L2/Z to predict the mass of chemical components in the carcass. Use of impedance (Z) measured at the characteristic frequency (Zc) instead of 50 kHz (Z50) did not improve the power of the model to predict the mass of water, protein or fat in the carcass. While L2/Z50 explained a significant proportion of variation in the masses of body water (r(2) 0.64), protein (r(2) 0.34) and fat (r(2) 0.35), its inclusion in multi-variate indices offered small or no increases in predictive capacity when hot carcass weight (HCW) and a measure of rib fat-depth (GR) were present in the model. Optimized equations were able to account for 65-90% of the variance observed in the weight of chemical components in the carcass. It is concluded that single frequency impedance data do not provide better prediction of carcass composition than can be obtained from measures of HCW and GR. Indices of intracellular water mass derived from impedance at zero frequency and the characteristic frequency explained a similar proportion of the variance in carcass protein mass as did the index L2/Z50.

Bioelectrical impedance analysis for the estimation of body composition in rats

Bioelectrical impedance analysis (BIA) was used to assess body composition in rats fed on either standard laboratory diet or on high-fat diet designed to induce obesity. Bioelectrical impedance analysis predictions of total body water and thus fat-free mass (FFM) for the group mean values were generally within 5% of the measured values by tritiated water (3H2O) dilution. The limits of agreement for the procedure were, however, large, approximately +/- 25%, limiting the applicability of the technique for measurement of body composition in individual animals.

An association between non-gonococcal urethritis and bacterial vaginosis and the implications for patients and their sexual partners

OBJECTIVES

The aetiology of non-gonococcal urethritis (NGU) in a considerable proportion of men remains unaccounted for. We wished to investigate the possible aetiological role of bacterial vaginosis (BV), the commonest cause of abnormal discharge in women, in this condition.

METHODS

We carried out two studies. In the first, case-control, study, we recruited men with and without NGU and examined their female partners for evidence of BV. The second, cohort design, study which ran concurrently with the first study involved recruiting women with and without BV and examining their male partners for evidence of NGU. The diagnoses of both NGU and BV were made microscopically to include symptomatic and asymptomatic individuals in both disease categories.

RESULTS

In the case-control study 51 couples were recruited. Of these 39 men had NGU and 12 (31%) of their female contacts had BV. In contrast, of 12 men without NGU, only one (8%) of the female partners had BV (odds ratio 4.89, 95% CI: 0.51-42.27). When only Chlamydia trachomatis negative patients were considered, the odds ratio for an association between BV and NGU was increased to 6.77, 95% CI: 0.73-62.68). Thirty eight couples were recruited to the cohort design study. Of 17 women with BV, 12 (71%) of their male partners had NGU. In contrast, of 21 women without BV, seven (33%) of their male partners had NGU (p = 0.049, odds ratio 4.8). When only C trachomatis negative patients were considered, the significance of the association was increased (p = 0.037; odds ratio 5.42).

CONCLUSIONS

An association exists between NGU and BV, and vice versa. If BV arises de novo the findings could help to explain the development of urethritis in stable sexual relationships.

Outcome after total hip arthroplasty. Comparison of a traditional disease-specific and a quality-of-life measurement of outcome

The purpose of this study was to examine the relationship between the Harris Hip Score (HHS), a traditional method of patient assessment of a total hip arthroplasty (THA), and the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), a commonly used health-related quality-of-life survey. One hundred forty patients returning for routine clinical follow-up evaluation of a primary THA were asked to fill out the SF-36 quality-of-life survey, as well as questions concerning their perceptions of their THA. The patient's surgeon assessed the THA with the traditional HHS. The correlations between the HHS and the SF-36 domains were highest in the physical component summary scores for male patients of all ages and female patients 65 years of age or older. The correlations were lower for the mental component summary scores of all patients, but particularly in female patients younger than 65. When the SF-36 scores were compared with age and sex-matched population norms, both age and sex were found to be important. Men younger than 65 had scores lower than norms in the physical function domains, but were comparable in the mental health domains. The older men had scores comparable to the norms in all domains. Female patients of all ages, however, had lower scores in the physical function domains. The greatest differences were noted in the female patients younger than 65. The HHS is commonly used to assess disease-specific pain and function in THA patients; however, the results of this study suggest that the SF-36 health survey can capture additional important quality-of-life domains that are influenced by a THA and that these domains are influenced by the age and sex of the patient. The combination of a disease-specific scoring system and a quality-of-life survey would allow a more global assessment of a THA in all patients. Studies evaluating the results of THAs should either assess the results of male and female patients separately when sample size is sufficiently large or use sex as a possible covariate in a multivariate analysis.

Impact of declining reimbursement and rising hospital costs on the feasibility of total hip arthroplasty

Total hip arthroplasty, although a very successful clinical treatment, remains an expensive procedure in an era of constrained health care resources. Hospitalization cost, charge, and reimbursement data were compared between all patients who underwent elective, primary, unilateral total hip arthroplasty in 1988 and 1993 at the UCLA Medical Center. Although length of hospitalization decreased by 36%, increases both in unit supply costs and in the intensity of hospital services prevented a statistically significant reduction in total hospitalization cost. Reimbursement declined by 27% after calculating inflation with the Consumer Price Index for Medical Care. Further, the margin by which reimbursement exceeded cost decreased from 66% in 1988 to 8% in 1993. These trends constitute a serious threat to the financial feasibility of total hip arthroplasty.

roughex down-regulates G2 cyclins in G1

Cell cycle arrest in G1 at the onset of patterning in the Drosophila eye is mediated by roughex. In roughex mutants, cells accumulate Cyclin A protein in early G1 and progress into S phase precociously. When Roughex is overexpressed in S/G2 cells, Cyclin A is mislocalized to the nucleus and degraded, preventing mitosis. Whereas Roughex inhibits Cyclin A accumulation, Cyclin E down-regulates Roughex protein in vivo. Roughex binds to Cyclin E and is a substrate for a Cyclin E-Cdk complex in vitro. These data argue that Roughex inhibits Cyclin A accumulation in early G1 by targeting Cyclin A for destruction. In late G1, Roughex is destabilized in a Cyclin E-dependent process, releasing Cyclin A for its role in S/G2.

Massive osteolysis after ceramic on ceramic total hip arthroplasty. A case report

The case of a 66-year-old woman who sustained a pathologic femur fracture secondary to extensive osteolysis distal to a pressfit femoral prosthesis with a ceramic on ceramic bearing surface is reported. The femoral and acetabular bearing surfaces showed signs of visible wear, although the stem showed little evidence of burnishing. Material curetted from the femoral medullary canal in the area of the osteolysis contained extensive amounts of histiocytes and foreign body debris. Qualitative spectrographic analysis of the curetted material showed levels of aluminum to be approximately 10 times more prevalent than either cobalt or chromium. Although there is little understanding of the cellular reactions to ceramic debris products, the extensive osteolysis seen in this patient suggests that alumina ceramic bearings may not be as biologically inert as initially perceived.

Extraction of electrical characteristics from pixels of multifrequency EIT images

Computer modelling has shown that electrical characteristics of individual pixels may be extracted from within multiple-frequency electrical impedance tomography (MFEIT) images formed using a reference data set obtained from a purely resistive, homogeneous medium. In some applications it is desirable to extract the electrical characteristics of individual pixels from images where a purely resistive, homogeneous reference data set is not available. One such application of the technique of MFEIT is to allow the acquisition of in vivo images using reference data sets obtained from a non-homogeneous medium with a reactive component. However, the reactive component of the reference data set introduces difficulties with the extraction of the true electrical characteristics from the image pixels. This study was a preliminary investigation of a technique to extract electrical parameters from multifrequency images when the reference data set has a reactive component. Unlike the situation in which a homogeneous, resistive data set is available, it is not possible to obtain the impedance and phase information directly from the image pixel values of the MFEIT images data set, as the phase of the reactive reference is not known. The method reported here to extract the electrical characteristics (the Cole-Cole plot) initially assumes that this phase angle is zero. With this assumption, an impedance spectrum can be directly extracted from the image set. To obtain the true Cole-Cole plot a correction must be applied to account for the inherent rotation of the extracted impedance spectrum about the origin, which is a result of the assumption. This work shows that the angle of rotation associated with the reactive component of the reference data set may be determined using a priori knowledge of the distribution of frequencies of the Cole-Cole plot. Using this angle of rotation, the true Cole-Cole plot can be obtained from the impedance spectrum extracted from the MFEIT image data set. The method was investigated using simulated data, both with and without noise, and also for image data obtained in vitro. The in vitro studies involved 32 logarithmically spaced frequencies from 4 kHz up to 1 MHz and demonstrated that differences between the true characteristics and those of the impedance spectrum were reduced significantly after application of the correction technique. The differences between the extracted parameters and the true values prior to correction were in the range from 16% to 70%. Following application of the correction technique the differences were reduced to less than 5%. The parameters obtained from the Cole-Cole plot may be useful as a characterization of the nature and health of the imaged tissues.

Evaluation of bioelectrical impedance for prospective nutritional assessment in cystic fibrosis

We have compared the use of bioelectrical impedance analysis (BIA) with anthropometry for the prediction of changes in total body potassium (TBK) in a group (n = 31) of children with cystic fibrosis. Linear regression analysis showed that TBK was highly correlated (r > 0.93) with height2/impedance, weight, height, and fat-free mass (FFM) estimated from skin-fold measurements. Changes in TBK were also correlated, but less well, with changes in height2/impedance, weight, height, and FFM (r = 0.69, 0.59, 0.44, and 0.40, respectively). The children were divided into two groups: those who had normal accretion of TBK (> 5%/y) and those who had suboptimal accretion of TBK (< 5%/y). Analysis of variance showed that the significant difference in the change in TBK between the groups was detectable by concomitant changes in impedance and weight but not by changes in height, FFM, or weight and height Z scores. The results of this study suggest that serial BIA measures may be useful as a predictor of progressive undernutrition and poor growth in children with cystic fibrosis.

Association of antibodies to Chlamydia trachomatis heat-shock protein 60 kD with chronic nongonococcal urethritis

Ninety male patients with acute nongonococcal urethritis (NGU) who presented for follow-up 10-92 days after initiation of treatment were evaluated. A polymerase chain reaction assay and direct fluorescence antibody test were used to detect Chlamydia trachomatis at presentation and during follow-up. Chlamydial heat-shock protein 60 kD (hsp60) serology with an enzyme-linked immunosorbent assay and C. trachomatis serology with a microimmunofluoresence test were undertaken. In 62 (69%) of the men, evidence of chronic urethritis was noted during follow-up. C. trachomatis was detected in only two patients during follow-up. Chlamydial hsp60 antibody was associated with the development of chronic urethritis between 10 and 92 days after treatment began (P < .04), that is, at 10-29 days (P < .02) and at 30-92 days (P < .008). These results are consistent with the theory that immune response to hsp60 is important in the development of this chronic disease. The results also suggest that chronic NGU is not a consequence of continued production of hsp60 by C. trachomatis.

The efficacy of prophylaxis with low-dose warfarin for prevention of pulmonary embolism following total hip arthroplasty

The selection of a prophylaxis regimen and its implementation have been influenced considerably by the decreased duration of hospital stays and the pressures of cost containment. The purpose of the present study was to determine the rate of symptomatic pulmonary embolism both before and after discharge, the number of days required to achieve an adequate level of anticoagulation, and the complications associated with the use of low-dose warfarin after total hip arthroplasty. Between 1987 and 1993, 1099 primary and revision total hip arthroplasties were performed in 940 patients who received low-dose warfarin for prophylaxis against thromboembolic disease. The average duration of prophylaxis was fifteen days (range, one to twenty-nine days). The target level of anticoagulation (as indicated by a prothrombin time of fourteen to seventeen seconds) was achieved an average of three days (range, one to sixteen days) after the operation. The level of anticoagulation was lower than the target range at the time of discharge after 257 total hip arthroplasties (23.4 per cent), and the target level was never achieved during the period of hospitalization after fifty-four such procedures (4.9 per cent). Twelve total hip arthroplasties were associated with a symptomatic pulmonary embolism; the over-all prevalence of this complication therefore was 1.1 per cent (95 per cent confidence interval, 0.4 to 1.9 per cent). Four pulmonary emboli were diagnosed before discharge and eight, after discharge. A fatal pulmonary embolism occurred after one procedure (0.1 per cent). Patients who had a history of symptomatic venous thromboembolic disease had a significantly increased risk of symptomatic pulmonary embolism after total hip arthroplasty (p = 0.001, Fisher exact test). A major bleeding episode occurred after thirty-two total hip arthroplasties (2.9 per cent). Patients who had a prothrombin time of more than seventeen seconds had a significantly increased risk of hematoma formation (p = 0.003, chi-square analysis). Prophylaxis with low-dose warfarin is safe and effective for the prevention of pulmonary embolism after total hip arthroplasty.

Low-dose warfarin prophylaxis to prevent symptomatic pulmonary embolism after total knee arthroplasty

Pulmonary embolism poses a risk to patients undergoing total knee arthroplasty. The selection of an appropriate prophylaxis agent and its implementation have been influenced by decreased duration of hospital stay and the pressures of cost containment. The purpose of this study was to determine the inpatient and outpatient pulmonary embolism rates, the number of days required to attain the target level of anticoagulation, and complications associated with the use of a low-dose warfarin prophylaxis protocol after primary and revision total knee arthroplasty. Between 1984 and 1993, there were 815 primary and revision total knee arthroplasties that received low-dose warfarin prophylaxis at our institution. The average time to attainment of the target level of anticoagulation was 3 days. The average duration of warfarin prophylaxis was 12 days. Overall, there were a total of three symptomatic pulmonary embolisms (0.3%; 95% confidence interval, 0.08%-1.1%). There were eight (1%) symptomatic deep vein thromboses (all distal). There were two deaths (0.3%), but neither one was secondary to a pulmonary embolism. Seventeen knees (2.5%) developed a hematoma after surgery, and two of these patients required drainage of the knee. Low-dose warfarin prophylaxis is safe and effective in preventing symptomatic pulmonary embolism after total knee arthroplasty.

Control of G1 in the developing Drosophila eye: rca1 regulates Cyclin A

In the developing eye of Drosophila melanogaster, cells become synchronized in the G1 phase of the cell cycle just prior to the onset of cellular differentiation and morphogenesis. In roughex (rux) mutants, cells enter S phase precociously because of ectopic activation of a Cyclin A/Cdk complex in early G1. This leads to defects in cell fate and pattern formation, and results in abnormalities in the morphology of the adult eye. A screen for dominant suppressors of the rux eye phenotype led to the identification of mutations in cyclin A, string (cdc25), and new cell cycle genes. One of these genes, regulator of cyclin A (rca1), encodes a novel protein required for both mitotic and meiotic cell cycle progression. rca1 mutants arrest in G2 of embryonic cell cycle 16 with a phenotype very similar to cyclin A loss of function mutants. Expression of rca1 transgenes in G1 or in postmitotic neurons promotes Cyclin A protein accumulation and drives cells into S phase in a Cyclin A-dependent fashion.

daughterless is required for Drosophila photoreceptor cell determination, eye morphogenesis, and cell cycle progression

Initiation of Drosophila peripheral nervous system (PNS) development requires the achaete-scute complex (AS-C) and the atonal (ato) genes. The AS-C and ato encode basic helix-loop-helix (bHLH) transcription factors that dimerize in vitro with another bHLH protein, daughterless (da). da has many functions during Drosophila embryonic development, as it is required for proper sex determination, oogenesis, and neurogenesis. Here, we examine the expression and function of da within the developing Drosophila eye. The use of a monoclonal antibody to the Da protein revealed that Da levels are modulated across the developing eye disc. Within the morphogenetic furrow (MF) and photoreceptor cell R8, there is a cell-by-cell correspondence between high levels of Da protein expression and Ato protein expression. Mosaic analysis of adult tissue demonstrates that da function is cell autonomous and required within R2, R3, R4, R5, and R8. Examination of gene expression in da- imaginal disc clones reveals that da regulates Ato expression in the MF, affects the progression of the MF, and is necessary for the reestablishment of the G2 and M phases of the synchronized cell cycle posterior to the MF.

Bioelectrical impedance for monitoring the efficacy of lymphoedema treatment programmes

The treatment of lymphoedema includes a combination of massage, compression bandaging, and exercise. To date the most common technique of assessing the efficacy of treatment has involved estimating the total limb volume from circumferential measurements at fixed intervals along the limb. This study investigated the application of multiple frequency bioelectrical impedance analysis, MFBIA, to monitor the volume of lymphoedema in the upper limb of patients who developed this disorder following surgery for cancer of the breast. Daily measurements of both circumference and impedance of both the affected and unaffected limbs were recorded for 20 patients throughout their 4 week treatment programmes. Twenty control subjects were also monitored daily over a similar 4 week period. Prior to the commencement of treatment the bioimpedance technique detected a significant (P < 0.01) asymmetry between the two limbs of the control subjects, associated with handedness (P < 0.001). Circumferential estimates of limb volumes in the control group detected no asymmetry. Impedance measures of extracellular fluid showed all of the patients to lie outside the 95% confidence interval determined from the data of the control group. The trends of the impedance measures and the circumferential estimates of volume throughout the 4 week program were found to be significantly different (P < 0.05); MFBIA exhibiting a greater sensitivity in the detection of lymphoedema. The results demonstrate that MFBIA is significantly more sensitive than circumferential measurement both in the early diagnosis of lymphoedema and in monitoring change.

Differences between patients' and physicians' evaluations of outcome after total hip arthroplasty

The purpose of this study was to compare patients' and physicians' evaluations of the results of 147 total hip arthroplasties. The patients and physicians independently evaluated pain and over-all satisfaction with the outcome of the procedure using a 10.0-centimeter visual-analog scale. They also answered a questionnaire with which they assessed general health, functional ability, and pain. The mean (and standard deviation) analog rating for pain (with 0.0 centimeters indicating no pain and 10.0 centimeters, severe pain) was 1.7 +/- 2.6 centimeters as assessed by the patients and 1.1 +/- 1.8 centimeters as assessed by the physicians (p < 0.001, paired t test). The mean analog rating for over-all satisfaction (with 0.0 centimeters indicating poor and 10.0 centimeters, excellent) was 8.6 +/- 2.1 centimeters as assessed by the patients and 8.8 +/- 1.7 centimeters as assessed by the physicians (p = 0.07, paired t test). There was a marked disparity between the patients' and the physicians' scores when the patients assigned a low score to a particular area. For the thirty patients who rated the pain as more than 4.0 centimeters, the mean analog rating was 6.8 +/- 2.1 centimeters according to the patients, while it was 3.6 +/- 2.7 centimeters according to the physicians (p < 0.001, linear regression). The mean analog rating for over-all satisfaction according to the nineteen patients who rated this parameter as less than 7.0 centimeters was 3.8 +/- 2.0 centimeters, while the mean rating according to the physicians 6.5 +/- 2.8 centimeters (p < 0.001, linear regression). The patients' and physicians' evaluations were similar regarding the results of the total hip arthroplasty when the patients had little or no pain and were satisfied with the result. However, the disparity increased as the patients' ratings for pain increased and their ratings for over-all satisfaction decreased. This study highlights a discrepancy between patients' and physicians' evaluations of the results of total hip arthroplasty. This discrepancy increased when the patient was not satisfied with the outcome. The use of patients' self-administered questionnaires as well as traditional physician-generated assessments may provide a more complete evaluation of the results of total hip arthroplasty.

Isolation of Drosophila cyclin D, a protein expressed in the morphogenetic furrow before entry into S phase

During Drosophila development, nuclear and cell divisions are coordinated in response to developmental signals. In yeast and mammalian cells, signals that control cell division regulate the activity of cyclin-dependent kinases (Cdks) through proteins such as cyclins that interact with the Cdks. Here we describe two Drosophila cyclins identified from a set of Cdk-interacting proteins. One, cyclin J, is of a distinctive sequence type; its exclusive maternal expression pattern suggests that it may regulate oogenesis or the early nuclear divisions of embryogenesis. The other belongs to the D class of cyclins, previously identified in mammalian cells. We show that Drosophila cyclin D is expressed in early embryos and in imaginal disc cells in a pattern that anticipates cell divisions. Expression in the developing eye disc at the anterior edge of the morphogenetic furrow suggests that cyclin D acts early, prior to cyclin E, in inducing G1-arrested cells to enter S phase. Our results also suggest that, although cyclin D may be necessary, its expression alone is not sufficient to initiate the events leading to S phase.

Total hip arthroplasty

Total hip arthroplasty continues to be an extremely successful procedure, with ever-widening indications and regular improvement in technique, materials, and design. In the past year several studies were published evaluating the results of both cemented and cementless total hip arthroplasty at mid- to long-term follow-up. In addition, careful analysis of basic laboratory studies including finite-element analyses have added to our understanding of materials and design. Specific findings in the past year included poor results with cemented hips in younger patients at long-term follow-up of greater than 16 years. A lower incidence of loosening has been found for cobalt chrome-cemented components compared with titanium-cemented components. No difference was found in the results of metal-backed versus non-metal backed cemented acetabular components, and an increasing incidence of loosening was shown for cemented acetabular components with time. The newer cementless hip arthroplasties showed evidence of learning curve, particularly with regard to innovative design such as acetabular screw rings, whereas porous-coated hemispherical cups appeared to do well. Thigh pain continues to be a problem with cementless designs, and the controversy of titanium versus cobalt chrome for cementless femoral stem designs continues at full tilt.