Peripheral quantitative computed tomography (pQCT) is an established diagnostic method for assessment of bone mineral density in the diagnosis of osteoporosis. However, the capacity of structural ...parameters of cancellous bone measured by high-resolution computed tomography remains to be explored. In 33 patients, bone mineral density (BMD) of the proximal femur was measured in vitro by pQCT using cylindrical biopsies from the intertrochanteric region harvested before the implantation of an artificial hip joint. By digital image analysis of CT scans, parameters derived from histomorphometry describing the microarchitecture of cancellous bone were measured. The biopsies were also loaded to failure by an uniaxial compression test to determine the biomechanical parameters, Young’s modulus, strength, and maximum energy absorption (E
max). Strong correlations were found for BMD vs. mechanical parameters (
r = 0.73 for Young’s modulus,
r = 0.82 for strength, and
r = 0.79 for E
max;
p < 0.001, n = 29). The morphological parameters, bone volume per trabecular volume (BV/TV), apparent trabecular thickness (app.Tb.Th), apparent trabecular separation (app.Tb.Sp), and trabecular number (Tb.N), correlated significantly with all mechanical parameters. The combination of morphological parameters with BMD in a multivariate regression model led to an overall, but only moderate, increase in
R
2 in all cases. Our data confirm the high predictive value of BMD for the mechanical competence of cancellous bone of the intertrochanteric region. However, quantification of cancellous bone structure by image analysis of CT scans may provide additional qualitative information for the analysis of bone strength.
As Dynan, Elmendorf, and Sichel (henceforth DES) note, the volatility of economic activity fell substantially sometime from the middle of the 1980s to the early 1990s. This decline is documented by ...McConnell and Perez-Quiros (2000) and Kim and Nelson (1999). Indeed, as shown in Table 1 of DES, the standard deviation of quarterly GDP growth was 4.4% in the 1960-1984 period, but 2.1% in the 1985-2004 period. Among the explanations given for the decline in macroeconomic volatility are a shift in the economy from production to services, changes in monetary policy, and changes in inventory management. It is also possible that the lower volatility is largely a consequence of luck: the economy has been favored by smaller shocks, as emphasized by Stock and Watson (2002). DES propose a different explanation: that financial innovation has led to this decline.
Ulnar nerve injuries can cause deficient hand movement patterns. Their assessment is important for diagnosis and rehabilitation in hand surgery cases. The purpose of this study was to quantify the ...changes in temporal coordination of the finger joints during different power grips with an ulnar nerve block by means of a sensor glove. In 21 healthy subjects, the onset and end of the active flexion of the 14 finger joints when gripping objects of different diameters was recorded by a sensor glove. The measurement was repeated after an ulnar nerve block was applied in a standardized setting. The change in the temporal coordination of the metacarpophalangeal (MCP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints with and without the nerve block was calculated within the same subject. In healthy subjects, the MCP joints started their movement prior to the PIP joints in the middle and ring finger, whereas this occurred in the reverse order at the index and little finger. The DIP joint onset was significantly delayed (P<0.01). With the ulnar nerve block, this coordination shifted towards simultaneous onset of all joints, independent of the grip diameter. The thumb and index finger were affected the least. With an ulnar nerve block, the PIP joints completed their movement prior to the MCP joints when gripping small objects (G1 and G2), whereas the order was reversed with larger objects (G3 and G4). The alterations with ulnar nerve block affected mainly the little finger when gripping small objects. With larger diameter objects, all fingers had a significant delay at the end of the PIP joint movement relative to the MCP and DIP joints, and the PIP and DIP joint sequence was reversed (P<0.01). Based on the significant changes in temporal coordination of finger flexion during different power grips, there are biomechanical effects of loss of function of the intrinsic muscles caused by an ulnar nerve block on the fine motor skills of the hand. This can be important for the diagnosis and rehabilitation of ulnar nerve lesions of the hand.
Les lésions du nerf ulnaire sont responsables de schémas pathologiques dans les mouvements de la main. Leur évaluation est un important problème en chirurgie de la main, tant pour le diagnostic que pour la rééducation. Le but de cette étude était la quantification des modifications de coordination temporelle des articulations digitales lors de différentes prises de force après bloc du nerf ulnaire, au moyen d’un gant sensible. Chez 21 sujets saints, le début et la fin de la flexion active des 14 articulations digitales au cours de prise de force d’objet de différents diamètres ont été enregistrés à l’aide d’un gant sensible. Les mesures furent répétées après qu’un bloc du nerf ulnaire fut réalisé selon un protocole standardisé. La modification de la coordination temporelle des articulations métacarpophalangiennes (MCP), interphalangiennes proximales (IPP) et interphalangiennes distales (IPD) avant et après bloc a été calculée chez le même sujet. Chez les sujets saints, les articulations MCP commençaient leur mouvement avant les articulations IPP au majeur et à l’annulaire, alors que pour l’index et le petit doigt, on observait un ordre inverse. La mise en jeu des articulations IPD était significativement retardée (p<0,01). Après bloc du nerf ulnaire, cette coordination était significativement modifiée vers la mise en jeu simultanée de toutes les articulations, indépendamment du diamètre de la prise. Le pouce et l’index étaient les doigts les moins affectés. Après bloc du nerf ulnaire, les articulations IPP terminaient leur mouvement significativement avant les articulations MCP pour les petites prises (G1 et G2), alors que pour les prises plus importantes (G3 et G4), l’ordre était significativement inversé. Les modifications observées après le bloc du nerf ulnaire concernaient plutôt le petit doigt lors des prises de force d’objet de petite taille. Pour des plus grands diamètres, tous les doigts étaient affectés avec un retard significatif de la fin du mouvement des articulations IPP par rapport aux articulations MCP et IPD et la séquence des articulations IPP et IPD était inversée (p<0,01). De ces modifications significatives de la coordination temporelle de la flexion des doigts pour différentes prises de force, des conclusions peuvent être tirées sur les effets biomécaniques d’une perte de fonction des muscles intrinsèques dûe à un bloc du nerf ulnaire sur les fines compétences motrices de la main. Ce peut être important dans le diagnostic et la rééducation de la main lors des lésions du nerf ulnaire.
The single-pion production reactions
pp
d
,
pp
np
and
pp
pp
were measured at a beam momentum of 0.95GeV/c (
T
p
400 MeV) using the short version of the COSY-TOF spectrometer. The central calorimeter ...provided particle identification, energy determination and neutron detection in addition to time-of-flight and angle measurements from other detector parts. Thus all pion production channels were recorded with 1-4 overconstraints. The main emphasis is put on the presentation and discussion of the
np
channel, since the results on the other channels have already been published previously. The total and differential cross-sections obtained are compared to theoretical calculations. In contrast to the
pp
channel we observe in the
np
channel a strong influence of the
excitation. In particular, the pion angular distribution exhibits a (3 cos
2
+ 1) -dependence, typical for a pure
s
-channel
excitation and identical to that observed in the
d
channel. Since the latter is understood by a
s
-channel resonance in the
1
D
2
pn
partial wave, we discuss an analogous scenario for the
pn
channel.
Objective. To test mechanical bone quality and bone mineral density of the femoral head at the day of implantation as indicators for femoral prosthesis loosening.
Methods. Mechanical bone quality of ...a femoral head slice was assessed by destructive compression testing combined with bone mineral density measurements using peripheral quantitative computed tomography. Fourteen patients with walking pains were attainable for a radiographical follow-up mean 7.1 years after implantation.
Results. Radiolucent lines along the stem were evident in 11 of 14 femurs, most of them seen in Gruen zones 7, 6, 1, 3, 14, and showed strong correlations to preoperative bone strength (
r=−0.80;
P<0.001) and axial stiffness (
r=−0.75;
P=0.002), yet not to bone mineral density (
r=−0.67;
P=0.009). Slight varus deviations <3° were noted in six femurs. Preoperative strength was reduced in this femurs to 54% (
P=0.006), and stiffness to 61% (
P=0.038), while bone mineral density did not differ significantly.
Conclusions. Femoral prosthesis loosening after seven years can be predicted by mechanical bone quality of the femoral head at the time of implantation. Bone mineral density measurements may also indicate future stem loosening but have to interpreted carefully, keeping in mind a poorer predictive value.
Relevance Indications and choice of type of hip arthroplasty should be balanced in osteoporotic bones in particular. While preoperative bone mineral density measurement allows the prediction of mechanical bone quality, its relevance in predicting failure in arthroplasty treatment remains unclear.
Stainless steel and commercially pure titanium are widely used materials in orthopedic implants. However, it is still being controversially discussed whether there are significant differences in ...tissue reaction and metallic release, which should result in a recommendation for preferred use in clinical practice.
A comparative study was performed using 14 stainless steel and 8 commercially pure titanium plates retrieved after a 12-month implantation period. To avoid contamination of the tissue with the elements under investigation, surgical instruments made of zirconium dioxide were used. The tissue samples were analyzed histologically and by inductively coupled plasma atomic emission spectrometry (ICP-AES) for accumulation of the metals Fe, Cr, Mo, Ni, and Ti in the local tissues. Implant corrosion was determined by the use of scanning electron microscopy (SEM).
With grades 2 or higher in 9 implants, steel plates revealed a higher extent of corrosion in the SEM compared with titanium, where only one implant showed corrosion grade 2. Metal uptake of all measured ions (Fe, Cr, Mo, Ni) was significantly increased after stainless steel implantation, whereas titanium revealed only high concentrations for Ti. For the two implant materials, a different distribution of the accumulated metals was found by histological examination. Whereas specimens after steel implantation revealed a diffuse siderosis of connective tissue cells, those after titanium exhibited occasionally a focal siderosis due to implantation-associated bleeding. Neither titanium- nor stainless steel-loaded tissues revealed any signs of foreign-body reaction.
We conclude from the increased release of toxic, allergic, and potentially carcinogenic ions adjacent to stainless steel that commercially pure Ti should be treated as the preferred material for osteosyntheses if a removal of the implant is not intended. However, neither material provoked a foreign-body reaction in the local tissues, thus cpTi cannot be recommend as the 'golden standard' for osteosynthesis material in general.
The basic structures for linking squares into polyhedra and networks (reticulation) are enumerated, and corresponding examples are described in which crystals were synthesized by linking paddle wheel ...(square) units into metal-organic frameworks (MOFs)-named MOF-102 to MOF-112.
A wide range of chemical compounds is spanned by heteroatomic ligands from Group 15/16 elements, which in Nature extend from AsS (in realgar) to AsS2−∞ (in sulfosalt minerals). The stabilization of ...labile molecules or those that do not exist in the free state by incorporation into transition metal complexes like Cp*2Fe2(AsSe)2 (1) and the oligomerization of molecular units under the influence of metal ions or complexes to form solids or hybrid clusters with inorganic cores and peripheral organometallic ligands are the main subjects of this article. Cp*=C5Me5.
PDF
