Stemmed femoral knee prostheses: Effects of prosthetic design and fixation on bone loss

Although the revision rates for modern knee prostheses have decreased drastically, the total number of revisions a year is increasing because many more primary knee replacements are being done. At the time of revision, bone loss is common, which compromises prosthetic stability. To improve stability, intramedullary stems are often used. The aim of this study was to estimate the effects of a stem, its diameter and the interface bonding conditions on patterns of the bone remodeling in the distal femur.

We created finite element models of the distal half of a femur in which 4 types of knee prostheses were placed. The bone remodeling process was simulated using a strain-adaptive bone remodeling theory. The amount of such remodeling was determined by calculating the changes in bone mineral density in 9 regions of interest from simulated DEXA scans.

The computer simulation model showed that revision prostheses tend to cause more bone resorption than primary ones, especially in the most distal regions. Predicted long-term bone loss due to a revision prosthesis with a thin stem equalled that around a prosthesis with an intercondylar box. However, strong regional differences were found- the stemmed prostheses having more bone loss in the most distal areas and some bone gain in the more proximal ones. A prosthesis with a thick stem led to an increase in bone loss. When the prosthesis-cement interface was bonded, more bone loss was predicted than with an unbonded interface. These results suggest that a stem which increases stability initially may reduce stability in the long term. This is due to an increase in stress shielding and bone resorption.     

Catechol oxidation by peroxidase-positive astrocytes in primary culture: an electron spin resonance study.

In rodents, chronic estrogenization has been shown to induce degeneration of dendrites and myelin figures in the hypothalamic arcuate nucleus adjacent to peroxidase-positive astrocyte processes. Because in this brain region estradiol is metabolized to 2-hydroxyestradiol (catecholestrogen), we hypothesized that the latter may be oxidized by the astrocytic peroxidase activity to cytotoxic ortho-semiquinones as occurs in peripheral tissues. Cysteamine induces nonenzymatic peroxidase activity in cultured astroglia identical to that observed in vivo. Using electron spin resonance, we demonstrate robust peroxidase-catalyzed oxidation of 2-hydroxyestradiol and dopamine by cysteamine-pretreated astrocyte cultures relative to untreated controls. These results implicate the peroxidase-positive astrocytes in the pathogenesis of estradiol-related hypothalamic damage, parkinsonism, and other free-radical-related neurologic disorders.     

Profiles of Neurological Outcome Prediction Among Intensivists

Background  

Advances in intensive care medicine have increased survival rates of patients with critical neurological conditions. The focus of prognostication for such patients is therefore shifting from predicting chances of survival to meaningful neurological recovery. This study assessed the variability in long-term outcome predictions among physicians and aimed to identify factors that may account for this variability.     

Guidelines for Cardiac Management in Noncardiac Surgery Are Poorly Implemented in Clinical Practice: Results from a Peripheral Vascular Survey in The Netherlands

Background: The American College of Cardiology (ACC)/American Heart Association (AHA) guidelines for Perioperative Cardiovascular Evaluation for Noncardiac Surgery recommend an algorithm for a stepwise approach to preoperative cardiac assessment in vascular surgery patients. The authors' main objective was to determine adherence to the ACC/AHA guidelines on perioperative care in daily clinical practice.

Methods: Between May and December 2004, data on 711 consecutive peripheral vascular surgery patients were collected from 11 hospitals in The Netherlands. This survey was conducted within the infrastructure of the Euro Heart Survey Programme. The authors retrospectively applied the ACC/AHA guideline algorithm to each patient in their data set and subsequently compared observed clinical practice data with these recommendations.

Results: Although 185 of the total 711 patients (26%) fulfilled the ACC/AHA guideline criteria to recommend preoperative noninvasive cardiac testing, clinicians had performed testing in only 38 of those cases (21%). Conversely, of the 526 patients for whom noninvasive testing was not recommended, guidelines were followed in 467 patients (89%). Overall, patients who had not been tested, irrespective of guideline recommendation, received less cardioprotective medications, whereas patients who underwent noninvasive testing were significantly more often treated with cardiovascular drugs ([beta]-blockers 43% vs. 77%, statins 52% vs. 83%, platelet inhibitors 80% vs. 85%, respectively; all P < 0.05). Moreover, the authors did not observe significant differences in cardiovascular medical therapy between patients with a normal test result and patients with an abnormal test result.     

Determinants of liver damage associated with intravenous methylprednisolone pulse therapy in Graves' ophthalmopathy.

BACKGROUND: Intravenous methylprednisolone pulses (IVMP) are more efficacious and better tolerated than oral prednisone in Graves' ophthalmopathy (GO) patients. However, acute and severe liver damage has been reported in sporadic cases during IVMP, resulting in fatal acute liver failure in four patients so far. The mechanism causing the liver damage is incompletely understood. DESIGN: We performed a prospective observational study in 13 patients with dysthyroid optic neuropathy (group A) and in 14 patients with moderately severe GO (group B) who were treated with high-dose (group A) or low-dose (group B) IVMP; cumulative steroid doses were 8.45 g in group A and 4.5 g in group B, and follow-up time was 24 weeks. MAIN OUTCOME: Slight increases in serum aminotransferases (in alanine aminotransferase [ALAT] more than in aspartate aminotransferase [ASAT]) were observed, in seven patients exceeding the upper normal limit of 40 U/L. These changes were more prominent in group A than in group B as was also evident from a decrease in ASAT/ALAT ratio in group A but not in group B. Changes in serum aminotransferases occurred especially in the first 6 weeks of IVMP, becoming smaller thereafter with the decrease in steroid dosage. Pretreatment liver steatosis or diabetes were not related to liver damage, but preexistent viral hepatitis was. CONCLUSION: IVMP in GO patients causes dose-dependent liver damage by a direct toxic effect of glucocorticoids on hepatocytes. Nevertheless, IVMP seems to be pretty safe if cumulative doses exceeding 8 g are avoided and liver function is checked before and at regular intervals during pulse therapy.     

How Can and Do Australian Doctors Promote Physical Activity?

Background.Physical inactivity is recognized as an important public health issue. Yet little is known about doctors' knowledge, attitude, skills, and resources specifically relating to the promotion of physical activity. Our survey assessed the current practice, perceived desirable practice, confidence, and barriers related to the promotion of physical activity in family practice.Methods.A questionnaire was developed and distributed to all 1,228 family practitioners in Perth, Western Australia.Results.We received a 71% response (n= 789). Family practitioners are most likely to recommend walking to sedentary adults to improve fitness and they are aware of the major barriers to patients participating in physical activity. Doctors are less confident at providing specific advice on exercise and may require further skills, knowledge, and experience. Although they promote exercise to patients through verbal advice in the consultation, few use written materials or referral systems.Conclusions.There are significant differences between self-reports of current practice and perceived desirable practice in the promotion of physical activity by doctors. Future strategies need to address the self-efficacy of family physicians and involve resources of proven effectiveness. The potential of referral systems for supporting efforts to increase physical activity by Australians should be explored.     

Rotational tomography of the normal and reconstructed middle ear in temporal bones: an experimental study

Imaging is an essential diagnostic tool in reconstructive middle ear surgery, especially in pre-operative planning. Due to ongoing improvement of imaging quality and development of new imaging techniques like e.g. rotational tomography (RT) post-operative follow-up and immediate evaluation of surgical results may become more important. The aim of this experimental study was to evaluate RT as a new tool for postoperative determination of middle ear anatomy and implant position in temporal bones. RT was performed in ten temporal bone specimen after insertion of different middle ear prostheses concerning material, shape and length (PORP; TORP; Stapes piston). An implantable hearing device (Symphonix Soundbridge®) was also implanted and visualized. For comparison some specimen additionally underwent conventional computed tomography (CT), including the newest technology. Characterization of anatomical structures of the temporal bone using RT was of comparable quality to conventional CT-scans in all investigated specimen while requiring approximately 30% of the CT’s irradiation exposure. Unlike CT the RT showed almost no problems due to metallic artefacts of the implanted prostheses. Furthermore RT enabled a 3-dimensional view of the temporal bone and angle determination of inserted prostheses towards the tympanic membrane and/or the malleus handle. Detailed imaging of the prostheses allowed determination of shape, material and localization within the specimen’s reconstructed middle ear. The new imaging technique of RT allows precise presentation of anatomical structures and middle ear implants in temporal bones. Following these experimental results it will be our future work to evaluate this method in clinical practise.     

Incretin mimetics as a novel therapeutic option for hepatic steatosis.

BACKGROUND: Fat accumulation in the liver or non-alcoholic fatty liver disease (NAFLD) is regarded as a key pathogenic factor and component of the metabolic syndrome. It was reported that administration of the incretin mimetic exenatide reversed hepatic steatosis in an obese mouse model. We had the opportunity to study the effect of additional exenatide administration on liver fat content in a patient with type 2 diabetes. CASE REPORT: A 59-year-old male with poorly controlled type 2 diabetes was treated with exenatide in addition to metformin monotherapy. Following 44 weeks of exenatide therapy, mean the liver fat measured by liver spectroscopy declined from 15.8% to 4.3%. This dramatic decrease in liver fat was accompanied by significant beneficial changes in several cardiovascular disease risk factors and improvement of all liver enzymes, in particular alanine aminotransferase, the most important marker of liver steatosis. CONCLUSION: This case report suggests that the incretin mimetic exenatide decreases hepatic fat accumulation and may play a role in the future treatment of NAFLD, and the associated insulin resistance and cardiovascular risk factors in an ever-growing high-risk population.     

Testicular dysgenesis and mental retardation in two incompletely masculinized XY-siblings.

Aberrations of fetal sexual development were studied in two retarded phenotypic female 46,XY dysgonadal sisters from a consanguineous marriage. Endocrine evaluation revealed an inadequate response of plasma-testosterone to human chorionic gonadotropin (hCG) stimulation and a normal response to adrenocorticotropic hormone (ACTH) administration. At exploratory laparotomy dysgenetic testes and remnants of the Müllerian and of the Wolffian duct were found. Loss of testicular function, resulting in male pseudohermaphroditism (MPH), can occur at different times during intrauterine development, resulting in a variety of clinical manifestations. A thorough evaluation is warranted in all patients in order to reach a correct diagnosis which is of importance for appropriate gender assignment and genetic counseling.     

The HIV prevalence among pregnant women in the Amsterdam region (1988–1991)

The objective of the study was to monitor the HIV prevalence in the years 1988–1991 among pregnant women in the Amsterdam region, visitors to an abortion clinic and 3 outpatient infertility clinics. All women attending these clinics were asked to participate in the study on a voluntary basis and were tested with informed consent. The women were questioned about risk-bearing behaviour of themselves and their sexual partner(s). In the period 1988–1991, of the 23,827 eligible pregnant women, 22,165 women participated (93.0%). Twenty-seven women were found to be positive for HIV antibodies (0.12%, 95% CI: 0.08%–0.17%), of whom twenty belonged to a known HIV risk group or had a partner who belonged to one of these groups and 7 women had no known HIV risk. Seventeen of the 27 women had a foreign nationality. The annual HIV prevalence among pregnant women was: 1988: 0.28%; 1989: 0.10%; 1990: 0.10%; 1991: 0.11%. In the years 1990 and 1991, of the 1,128 eligible women visiting the abortion clinic 953 (84.5%) were tested. Eleven women were HIV-seropositive (1.15%, 95% CI: 0.6%–2.0%), of whom 9 were from an AIDS endemic region, 1 woman had a partner from this region and 1 woman had no known HIV risk. Four African women had HIV-2 antibodies. At the 3 outpatient infertility clinics 1 woman was found to be HIV-positive (0.13%; 95% CI: 0.02–0.9). She had no other risk than a partner from an AIDS endemic area. In the Amsterdam region there was a steady and low HIV prevalence (0.1%) among pregnant women through the years 1988–1991. The prevalence in the abortion clinic was ten times higher. The program was able to detect possible high risk groups within the population. Migration and travelling can play an important role in the spread of HIV in the general heterosexual population.