The modular endoprosthesis for mandibular body replacement. Part 1: Mechanical testing of the reconstruction

IntroductionIn this paper we present the results of the mechanical testing of a new generation modular endoprosthesis, which has been designed to improve the results of mandibular reconstruction.Materials and methodsThe new cementless endoprosthesis consists of a male part, a female part (both with screws on the stems), connected via a dove-tailed connection and secured with a coronal screw.The endoprosthesis was fitted into standardized blocks of synthetic bone (Synbone AG, Malans, Switzerland). The set-up was fixed to an ElectroPuls testing machine at one end and loaded at the other end 25 mm away. Three specimens were loaded continuously until failure to determine the average load to failure of the construct. Five specimens were then loaded cyclically between 10 and 150 N until either failure or 500,000 cycles. A finite element analysis was also performed on the set-up.ResultsOf the five specimens in the fatigue testing, only one survived while the other four either were bent or fractured at the stem of the clamped portion. The specimen that survived had very good bony contact with the prosthesis at the lower border. The connection of the modules via the dove-tailed design did not show any loosening. Finite element analysis showed areas of stress concentration at the superior surface of the stems to 188.8 MPa. This was well below the yield strength of titanium alloy of 897 MPa. Statistical analysis performed for specimens 1 to 4 to calculated lower tolerance bounds on cycles to failure, representing the estimated minimum achievable cycles to failure at 90, 95, and 99% of the population at 90 and 95% confidence levels, showed that the estimated mean cycles to failure was 10,132 cycles at the mean, minimum and maximum loads of 120 N and 18.4 N respectively.ConclusionGood bony contact seems to be essential at the lower border for long-term survival of the reconstruction. Small gaps increase the bending forces and thus shear stresses at the stem. The new design of the modular endoprosthesis is prone to stress concentrations at the superior surface of the stems. This is accentuated by the sharp screw threads of the stems. The loosening of the module connection seemed to have been stopped with the dove-tailed design.     

Predicting health-related quality of life in dialysis patients: Factors related to negative outcome expectancies and social support

ObjectivesDialysis patients report a low health-related quality of life (HRQOL) due to high disease burden and far-reaching consequences of dialysis treatment. This study examined several cognitive-behavioral and social factors, with a focus on negative outcome expectancies, that might be relevant for HRQOL in end-stage kidney disease (ESKD) patients treated with dialysis.MethodsPatients treated with hemodialysis or peritoneal dialysis were recruited from Dutch hospitals and dialysis centers. Patients completed self-report questionnaires at baseline (n = 175) and six months follow-up (n = 130). Multiple regression analyses were performed.ResultsHigher scores on factors related to negative outcome expectancies at baseline, especially helplessness and worrying, and less perceived social support were significantly related to worse HRQOL six months later. When controlling for baseline HRQOL, besides sex and comorbidity, helplessness remained significantly predictive of worse HRQOL six months later, indicating that helplessness is associated with changes in HRQOL over time.ConclusionsNegative outcome expectancies and social support are relevant markers for HRQOL and/or changes in HRQOL over time.Practice implicationsNegative outcome expectancies could be prevented or diminished by enhanced treatment information, an improved patient-clinician relationship, and interventions that promote adaptive and realistic expectations. Additionally, increasing supportive social relationships could be a relevant treatment focus.     

Elliptical localization with pulsed second‐order fields (ECLIPSE) for robust lipid suppression in proton MRSI

Proton MRSI has great clinical potential for metabolic mapping of the healthy and pathological human brain. Unfortunately, the promise has not yet been fully achieved due to numerous technical challenges related to insufficient spectral quality caused by magnetic field inhomogeneity, insufficient RF transmit power and incomplete lipid suppression. Here a robust, novel method for lipid suppression in ¹H MRSI is presented. The method is based on 2D spatial localization of an elliptical region of interest using pulsed second‐order spherical harmonic (SH) magnetic fields. A dedicated, high‐amplitude second‐order SH gradient setup was designed and constructed, containing coils to generate Z2, X2Y2 and XY magnetic fields. Simulations and phantom MRI results are used to demonstrate the principles of the method and illustrate the manifestation of chemical shift displacement. ¹H MRSI on human brain in vivo demonstrates high quality, robust suppression of extracranial lipids. The method allows a wide range of inner or outer volume selection or suppression and should find application in MRSI, reduced‐field‐of‐view MRI and single‐volume MRS.     

Coccidioidomycosis Infection of a Total Knee Arthroplasty in a Nonendemic Region

Fungal prosthetic joint infections are rare and difficult to treat. There is an ongoing discussion about the type and duration of antifungal treatment and the necessity of prosthesis removal. We report the first European case of an infected total knee arthroplasty with Coccidioides immitis. Treatment consisted of lifelong treatment with oral fluconazole at a dose of 400 mg/d, without total knee arthroplasty removal. After 6 months, the initial complaints of pain and swelling were completely resolved. This case report clearly states that a travel history and culturing for fungi are helpful in patients with persisting complaints after joint arthroplasty.     

Toxicity of Coarse and Fine Particulate Matter from Sites with Contrasting Traffic Profiles

Residence in urban areas with much traffic has been associated with various negative health effects. However, the contribution of traffic emissions to these adverse health effects has not been fully determined. Therefore, the objective of this in vivo study is to compare the pulmonary and systemic responses of rats exposed to particulate matter (PM) obtained from various locations with contrasting traffic profiles. Samples of coarse (2.5 μm–10 μm) and fine (0.1 μm–2.5 μm) PM were simultaneously collected at nine sites across Europe with a high-volume cascade impactor. Six PM samples from various locations were selected on the basis of contrast in in vitro analysis, chemical composition, and traffic profiles. We exposed spontaneously hypertensive (SH) rats to a single dose (3 mg PM/kg body weight or 10 mg PM/kg body weight) of either coarse or fine PM by intratracheal instillation. We assessed changes in biochemical markers, cell differentials, and histopathological changes in the lungs and blood 24 h postexposure. The dose-related adverse effects that both coarse and fine PM induced in the lungs and vascular system were mainly related to cytotoxicity, inflammation, and blood viscosity. We observed clear differences in the extent of these responses to PM from the various locations at equivalent dose levels. There was a trend that suggests that samples from high-traffic sites were the most toxic. It is likely that the toxicological responses of SH rats were associated with specific PM components derived from brake wear (copper and barium), tire wear (zinc), and wood smoke (potassium).