Factors Associated with Revision Surgery after Internal Fixation of Hip Fractures

Background: Femoral neck fractures are associated with high rates of revision surgery after management with internal fixation. Using data from the Fixation using Alternative Implants for the Treatment of Hip fractures (FAITH) trial evaluating methods of internal fixation in patients with femoral neck fractures, we investigated associations between baseline and surgical factors and the need for revision surgery to promote healing, relieve pain, treat infection or improve function over 24 months postsurgery. Additionally, we investigated factors associated with (1) hardware removal and (2) implant exchange from cancellous screws (CS) or sliding hip screw (SHS) to total hip arthroplasty, hemiarthroplasty, or another internal fixation device. Methods: We identified 15 potential factors a priori that may be associated with revision surgery, 7 with hardware removal, and 14 with implant exchange. We used multivariable Cox proportional hazards analyses in our investigation. Results: Factors associated with increased risk of revision surgery included: female sex, [hazard ratio (HR) 1.79, 95% confidence interval (CI) 1.25-2.50; P = 0.001], higher body mass index (fo

Photopolymerization of Pigmented Thiol-ene Systems

Photopolymerization kinetics and optical properties of pigmented thiol-ene coatings were investigated using photo-DSC, real-time FTIR, colorimetry, and AFM. Pigment has no deleterious effect on the unique ability of thiol-ene systems to photopolymerize in air. When trimethylolpropane tris-(3-mercaptopropionate) is incrementally added to tripropylene glycol diacrylate with and without calcium lithol rubine, a red organic pigment, the photopolymerization rate in nitrogen steadily decreases due to a shift in the polymerization mechanism from an acrylate homopolymerization to a thiol-ene copolymerization. However, the photopolymerization rate of pigmented and nonpigmented systems in air significantly increases with increasing thiol concentration, ultimately reaching a maximum at approximately 35 mole percent trifunctional thiol. The increase in rate is due to chain transfer from the non-reactive peroxy radical to the thiol. Thiol groups reduce oxygen inhibition to a greater degree than standard additives such as N-methyldiethanolamine, N-vinyl pyrrolidinone, and thioether containing trifunctional vinyl esters. For a typical acrylate based pigmented photocurable system, greater than 10 wt% photoinitiator is required to achieve a photopolymerization rate equivalent to a comparable thiol-ene system with 1 wt% photoinitiator in air. AFM and colorimetric data indicate that addition of trifunctional thiol has no deleterious effect on pigment dispersion and may in fact increase dispersion quality. (C) 2004 Elsevier Ltd. All rights reserved

Copolymerization Mechanism of Photoinitiator Free Thiol-Vinyl Acrylate Systems

The photoinitiator-free copolymerization of trifunctional thiol/vinyl acrylate mixtures as a function of thiol content has been investigated using real-time FTIR in the presence and absence of oxygen. Even without external photoinitiators, the thiol/vinyl acrylate mixtures polymerize rapidly. The addition of a multifunctional thiol to vinyl acrylate results in the conversion of the vinyl double bond of vinyl acrylate due to the preferential addition of the thiyl radical to the vinyl double bond. Both the chain transfer reaction of the carbon centered radicals to thiol and subsequent addition of the thiyl radicals to vinyl double bonds during copolymerization strongly affect the copolymerization kinetics of this system. The effect of thiol on vinyl acrylate polymerization in the presence of oxygen is particularly significant due to the role of thiol in reducing oxygen inhibition. Two free-radical chain processes occur in both the presence and absence of oxygen

Photoinduced Free Radical Polymerization Using Self-Initiating Monomers

Historically, a number of self photo-initiating carbon-carbon double bond (C=C) containing monomers have examined during a fairly long period of time with respect to their relative efficiencies in initiating free radical polymerization and these findings are well documented in the literature [S.E. Jonsson, RE. Sundell, J. Hultgren, D. Sheng, C.E. Hoyle, Prog. Org. Coat. 27 (1996) 107-122; S.E. Jonsson, M. Shimose, S. Clark, C.E. Hoyle, Polymer Communications, 38 (22) (1997) 5695-5697; S. Katogi, C.W. Miller, S.E. Jonsson, C.E. Hoyle, Polymer 39 (13) (1997) 2709; C.E. Hoyle, S.E. Jonsson, RE. Sundell, M. Shimose, S.C. Clark, C. Miller, J. Owens, F. Morel, C. Decker Nucl. Instrum. Methods Phys. Res., B2 (1997)]. Traditional monomer systems involve maleimides and alpha,beta-substituted maleimides and maleates/fumarates mostly in vinyl ether combinations [F. Morel, C. Decker, S.E. Jonsson, S.C. Clark, C.E. Hoyle, Polymer 40 (1999) 2447; C.E. Hoyle, S.E. Jonsson, C. Miller, K. Viswanathan, F. Morel, C. Decker, S.C. Clark, Nucl. Instrum. Methods Phys. Res. B, 151 (1999) 268; S.E. Jonsson, K. Viswanathan, C.E. Hoyle, S.C. Clark, C. Miller, C. Nguyen, W. Shao, L. Shao, F. Morel, C. Decker, J. Photopolym. Sci. Technol. 13 (1) (2000) 125-143; C. Decker, C. Bianchi, F. Morel, S.E. Jonsson, C.E. Hoyle, Macromol. Chem. Phys. 201 (2000) 1493-1503]. In this paper, a comprehensive study has been undertaken in investigating the initiating efficiencies of alpha,beta-substituted alkenyl acrylates (X-1-C=C(Y-1)COO(X-2-C=C-Y-2)). In order to evaluate the photochemistry involved in the excitation process, focus has been emphasized on vinyl acrylate (VA) as a model compound. VA exhibits fast rates of polymerization and high degrees of conversion are obtained. Real Time Infra Red analysis (RTIR) was used throughout the investigation in recording the kinetics of the home, and co-polymerization of VA and in combinations with various co-monomers in the presence and absence of PhI. In the homopolymerization of VA, the acrylate C=C was found to polymerize much faster than the vinyl ester C=C. The enhanced reactivity of the acrylate C=C in VA is mainly due to the very close proximity of the two C=C bonds exhibiting large differences in electron densities over the two C=C bonds within the same molecule. Modeling studies are compared to real time recorded kinetics, showing good correlation. Furthermore, a mechanistic investigation of the nature of the excited state conformation in VA also indicates fundamental differences in the efficiencies of initiation , which can be caused by a biradical versus a conventional monoradical pathway of initiation seen by the use of commercially available PHI\u27s. Finally, useful future implications in the use of VA and derivatives thereof as initiating monomers in practical acrylate based formulations will be discussed in the paper. (C) 2004 Published by Elsevier B.V