PMMA-based bioactive cement: effect of glass bead filler content and histological change with time.

A new bioactive bone cement (designated GBC), which is a polymethyl methacrylate (PMMA)-based composite consisting of bioactive glass beads as an inorganic filler and high molecular-weight PMMA as an organic matrix, has been developed. The purpose of the present study was to evaluate the effect of the filler content on the mechanical properties and osteoconductivity of GBC, to decide the most suitable filler proportion, and to evaluate the degree of cement degradation with time. The bioactive beads, consisting of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) glass, were added to the cement in various proportions (40-70 wt %). The bending strength of GBC did not differ among the proportions (approximately 136 MPa), but the elastic modulus of bending of GBC increased as the glass bead filler content increased (approximately 4.1-7.2 GPa). The all types of GBC were packed into the intramedullary canals of rat tibiae to evaluate osteoconductivity, as determined by an affinity index calculated as the length of bone in direct contact with the cement surface expressed as a percentage of the total length of the cement surface. Rats were sacrificed at 4, 8, 25, and 39 weeks after implantation, and the affinity index was calculated for each type of GBC at each time point. Histologically, new bone had formed along the surface of all types of GBC within 4 weeks, even in GBC containing only 40 wt % of glass beads. The affinity indices of GBC tended to increase as the proportion of glass bead filler increased and as the implantation period increased. In GBC containing 60 or 70 wt % of glass beads, significant rapid increases in the affinity indices were found from 4 to 8 weeks, and the high values (approximately 70%) were maintained up to 39 weeks. A sign of glass bead degradation was observed at the bone-cement interface in the rat tibiae at 39 weeks. We conclude that, when mechanical properties and osteoconductivity are both taken into consideration, GBC containing 60 or 70 wt % of glass beads is the most suitable formulation, but that further studies are needed to investigate and overcome the degradation.     

Development of early neutropenic fever, with or without bacterial infection, is still a significant complication after reduced-intensity stem cell transplantation.

Little information is available on the clinical characteristics of infectious complications that occur in the early period after reduced-intensity stem cell transplantation (RIST). We retrospectively investigated the clinical features of neutropenic fever and infectious episodes within 30 days after RIST in 76 patients who had received fluoroquinolones as part of their antibacterial prophylaxis. Preparative regimens included cladribine 0.66 mg/kg or fludarabine 180 mg/m2 plus busulfan 8 mg/kg. All but 1 patient survived 30 days after transplantation, and 75 patients (99%) became neutropenic within a median duration of 9 days. Neutropenic fever was observed in 29 patients (38%), and bacterial infection was confirmed in 15 (20%) of these, including bacteremia (n = 13), bacteremia plus pneumonia (n = 1), and urinary tract infection (n = 1). The causative organisms were gram-positive (n = 9) and gram-negative organisms (n = 7), with a mortality rate of 6%. Neither viral nor fungal infection was documented. Multivariate analysis showed that the presence of neutropenia at the initiation of preparative regimens was an independent risk factor for subsequent documented bacterial infections (P =.026; 95% confidence interval, 1.25-35.1). We conclude that neutropenic fever and bacteremia remain common complications in RIST.     

Critical spectral regions for vowel identification

The first two formant frequencies (F1 and F2) are the cues important for vowel identification. In the categorization of the naturally spoken vowels, however, there are overlaps among the vowels in the F1 and F2 plane. The fundamental frequency (F0), the third formant frequency (F3) and the spectral envelope have been proposed as additional cues. In the present study, to investigate the spectral regions essential for the vowel identification, untrained subjects performed the forced-choice identification task in response to Japanese isolated vowels (/a, o, u, e, i/), in which some spectral regions were deleted. Minimum spectral regions needed for correct vowel identification were the two regions including F1 and F2 (the first and fourth in the quadrisected F1-F2 regions in Bark scale). This was true even when phonetically different vowels had a similar combination of F1 and F2 frequency components. F0 and F3 cues were not necessarily needed. It is concluded that the relative importance in the spectral region is not equivalent, but weighted on the two critical spectral regions. The auditory system may identify the vowels by analyzing the information of the spectral shapes and the formant frequencies (F1 and F2) in these critical spectral regions.     

Voxel-based morphometry of human brain with age and cerebrovascular risk factors

The objectives of this study were to evaluate the correlations of the volumes of the gray matter and white matter with age, and the correlations of the tissue probabilities of the gray matter and white matter with age and several cerebrovascular risk factors. We obtained magnetic resonance (MR) images of the brain and clinical information from 769 normal Japanese subjects. We processed the MR images automatically by correcting for inter-individual differences in brain size and shape, and by segmenting the MR images into the gray matter and white matter. Volumetry of the brain revealed a significant negative correlation between the gray matter volume and age, which was not observed between white matter volume and age. Voxel-based morphometry showed that age, systolic blood pressure, and alcohol drinking correlated with the regional tissue probabilities of the gray matter and white matter.     

Total hip arthroplasty using hydroxyapatite-coated cementless cup for rapidly destructive coxarthrosis: Minimum 10-year follow-up

BackgroundPerforming total hip arthroplasty (THA) as early as possible is recommended for rapidly destructive coxarthrosis (RDC) as it causes pain that becomes progressively more severe. However, acetabular bone loss remains an issue in THA. Special devices, such as a Kerboull-type plate, may be used for acetabular bone defects, but the procedure is highly invasive and often the patients are elderly, further complicating matters. We retrospectively investigated the clinical and radiographic results of THA using conventional hydroxyapatite-coated cementless cup in RDC.MethodsA total of 32 patients (35 hips) with RDC were enrolled in the study with a minimum 10-year follow-up. All THAs were performed using conventional hydroxyapatite-coated cementless cup. All patients were evaluated clinically according to the Harris hip score (HHS). Acetabular bone deficiency was classified according to the American Academy of Orthopaedic Surgeons (AAOS) classification.ResultsEleven hips (31%) were AAOS type III, and none were type IV. Total HHS significantly improved from 36.5 to 79.4 (p < 0.01). Two cups exhibited loosening. The overall implant-associated survival rate after 10 years was 91.4%.ConclusionsClinical results of THA using conventional cementless implants for patients with RDC were acceptable. Thus, THA using conventional cementless implant is an effective and safe surgery for patients with RDC, minimizing surgical stress.