Patient and surgery related factors associated with fatigue type polyethylene wear on 49 PCA and DURACON retrievals at autopsy and revision

<p>Abstract</p> <p>Background</p> <p>Polyethylene wear is an important factor for longevity of total knee arthroplasty. Proven and suspicious factors causing wear can be grouped as material, patient and surgery related. There are more studies correlating design and/or biomaterial factors to in vivo wear than those to patient and surgery related factors. Many retrieval studies just include revision implants and therefore may not be representative. This study is aimed to correlate patient- and surgery- related factors to visual wear score by minimizing design influence and include both autopsy and revision implants. Comparison between the groups was expected to unmask patient and surgery-related factors responsible for wear.</p> <p>Methods</p> <p>The amount of joint side wear on polyethylene retrievals was measured using a modification of an established visual wear score. Fatigue type wear was defined as summation of the most severe wear modes of delamination, pitting and cracks. Analysis of patient and surgery related variables suspicious to cause wear included prospectively sampled patient activity which was measured by self reported walking capacity. Statistical analysis was done by univariate analysis of variance. Activity level and implantation time were merged to an index of use and correlated to the wear score.</p> <p>Results</p> <p>Wear score after comparable implantation time was significantly less in the autopsy group. Even so, fatigue type wear accounted for 84 and 93 % of total wear score on autopsy and revision implants respectively. A highly significant influence on wear score was found in time of implantation (p = 0.002), level of activity (p = 0.025) and inserts belonging to revision group (p = 0.006). No influence was found for the kind of patella replacement (p = 0.483). Body mass index and accuracy of component alignment had no significant influence on visual wear score. Fatigue-type wear in the medial compartment was closely correlated to the index of use in the autopsy (R²= 0.383) and the revision group (R²= 0.813).</p> <p>Conclusion</p> <p>The present study's finding of substantial fatigue type wear in both autopsy and revision retrievals supports the theory that polyethylene fatigue strength is generally exceeded in this type of prosthesis. Furthermore, this study correlated fatigue-type polyethylene wear to an index of use as calculated by activity over time. Future retrieval studies may use activity over time as an important patient related factor correlated to the visual wear score. When evaluating total knee arthroplasty routine follow up, the surgeon must think of substantial wear present even without major clinical signs.</p

Two-photon laser spectroscopy of Ce3+ in LiYF4

One-color two-photon excitation spectra of the 4f1 → 5d1 transitions of Ce3+ in LiYF4 have been investigated at 5 K from 33 400 to 44 000 cm−1. A sharp lorentzian line peaking at 33 439.4 cm−1 with a width of 2.6 cm−1 is observed on the low energy side of a band extending up to 35 200 cm−1. The line and the band are observed to exhibit different polarization dependences. A second band with a maximum peaking around 41 977 cm−1 is observed to extend from 40 000 up to 44 000 cm−1. No sharp line associated to this band is seen

7F0→5DJ two-photon-absorption transitions of Sm2+ in SrF2

One-color two-photon excitation spectra of the 7F0→5D0 and 7F0→5D2 transitions of Sm2+ in SrF2 have been measured at low temperature and their dependences upon photon polarization analyzed. Linewidths on the order of 0.2, 0.6, and 1.0 cm-1 are obtained for the 7F0→5D0(A1g), 7F0→5D2(Eg), and 7F0→5D2(T2g) Stark components observed at 15 K, respectively. The 7F0→5D0(A1g) transition is observed to be isotropic within experimental error, while the Eg and T2g components of the 7F0→5D2 transition exhibit the anisotropic patterns expected in Oh symmetry. Calculations of two-photon transition intensities are conducted within the framework of the phenomenological model previously used for Sm2+ in MClF (M=Ba,Sr) and Eu3+ in LuPO4, where the rare-earth ion occupies sites of C4v and D2d symmetries, respectively. The present results are compared and contrasted with those obtained in these previous cases

An insulinoma nuclear factor binding to GGGCCC motifs in human insulin gene.

Cell specific expression of the insulin gene is achieved through transcriptional mechanisms operating on 5' flanking DNA elements. In the enhancer of rat I insulin gene, two elements, the Nir and Far boxes, located at positions -104 and -233 respectively and containing the same octameric motif are essential for B cell specific transcription activity. Homologous sequences are present in the human insulin gene. While studying the binding of nuclear proteins from insulinoma cells to the -258/+241 region of the human insulin gene, we observed a previously undetected protein binding site in the intron I region between nucleotides +160 and +175. The binding activity was present in insulin producing cells such as RIN and HIT insulinoma cells but not in fibroblasts or insulin negative fibroblast x RIN hybrid cells. DNAse I footprinting and gel retardation/methylation interference experiments allowed us to define the core binding site of the intron binding factor as a GGGCCC hexamer. This factor is also capable to bind to a related sequence, contiguous to the Far-like element in rat and human insulin genes. The binding of the GGGCCC binding factor in this critical region of the insulin gene enhancer may participate in the regulation of insulin gene expression