No abstract

IFN (2, 3). The crosslinking of 125I-IFNa to several human cell lines indicates that the IFNa/P receptor is a multiprotein complex, consisting of 95-, 115-, and 135-kDa subunits (3-5).Type I IFNs induce the transcription of specific early genes, the IFN-stimulated genes (ISGs), through the activation of the Jakl and Tyk2 protein-tyrosine kinases (PTKs) (6,7). PTK activation mediates the IFN-induced rapid tyrosine phosphorylation of the multiprotein latent cytosolic transcription factor ISGF3, which consequently translocates to the nucleus, where it interacts with conserved promoter elements in ISGs (8,9). This model of PTK activation resulting in the tyrosine phosphorylation of specific transcription factors and gene activation has been described for several cytokines (6,10,11) and serves as a paradigm for cytokine signaling. In contrast, the early events triggered by IFNa receptor occupancy and the functions of the various subunits are poorly characterized.A cDNA coding for one subunit (IFNaRl) of the human

Object Instrumentation of the osteoporotic spine can be fraught with complications such as hardware failure. A cadaver study was performed to determine the biomechanical performance of polymethylmethacrylate (PMMA)–augmented pedicle screws. Methods Three osteoporotic human cadaveric specimens with a mean bone mineral density of 0.70 g/cm2 were used to evaluate the performance of a novel fenestrated bone tap in pedicle screw augmentation. On this device, tap threads serve a dual purpose in preventing backflow of cement toward neural elements while allowing for a custom form for subsequent screw placement. The tap was used to inject a mean volume of 3.7 ml PMMA/pedicle (range 2–8.0 ml PMMA/pedicle) followed by pedicle screw placement between L-5 and T-5, alternating between augmented and nonaugmented instrumentation. Axial pullout testing was then performed. Results Pedicle screw pullout strength was increased in both primary and salvage procedures by 119% (p = 0.001) and 162% (p = 0.01), respectively, after PMMA augmentation. Additionally, the injected cement volumes were divided into two groups, a low-cement group (≤ 2.8 ml/pedicle) and a high-cement group (≥ 5.5 ml/pedicle). Interestingly, the pullout strength did not significantly change with increased cement usage between the two groups (p > 0.05 for all comparisons). Conclusions Polymethylmethacrylate-augmented pedicle screw fixation results in a significant increase in the axial pullout strength of augmented pedicle screws in both primary and revision procedures. This technique may be a valuable adjunct in cases in which bolstering of the screw–bone interface is necessary.

Polymethylmethacrylate-augmented pedicle screw fixation reduces the likelihood of pedicle screw loosening and pullout in patients with osteoporosis requiring instrumented arthrodesis.