Vascular Injury in Total Hip Replacement: Management and Prevention

This chapter analyzed the vascular complications in total hip replacement. Vascular injuries are the uncommon but well recognized and serious issue. During total hip replacement, laceration of major blood vessels has been reported which even cause morbidity and mortality. The injury to vascular structures occurs due to the placement of screws to fix acetabular components, structural grafts, and protrusio cages or rings. Massive hemorrhage resulting in immediate exsanguination may be caused due to the damage of any of these vessels by processes such as drilling, reaming, retraction, or dissection. The majority of these vascular injuries might be better prevented or even more proficiently treated by comprehensive preoperative assessment, better instrumentation, and careful postoperative monitoring

Process for manufacturing ultra high molecular weight polyethylene catalyst

The present invention pertains to a process for manufacturing an ultra-high molecular weight polyethylene, wherein olefin monomers are contacted with a catalytic system under polymerisation conditions under formation of a polyethylene, wherein the catalytic system comprises an active component on a particulate carrier in a site density in the range of 5* 10 (- 9) to 5*10 (-6) mole of catalytic sites per m2 of carrier surface area, the particulate carrier having an average particle diameter in the range of 1-300 nm, wherein the polyethylene has a weight average molecular weight (Mw) of at least 500 000 gram/mole, and an elastic shear modulus G0 N, determined directly after melting at 160°C of at most 1.4 MP a

Laser-flash in-plane thermal analysis: the case of oriented UHMWPE

Laser-flash thermal analysis has been applied to measure the thermal diffusivity of highly oriented samples of Ultra High Molecular Weight Polyethylene. Due to the anisotropy of the sample, in-plane measurements are required instead of through-plane ones

Activation of a bis-(phenoxyimine) titanium (IV) catalyst using different aluminoxane co-catalysts

The activation of a bis-phenoxyimine catalyst based on titanium (IV) using different aluminoxanes (MAO, PMAO and MMAO12) has been studied. The effect of a co-catalyst modifier (BHT) used in combination with the MAO has been also tested. In particular, the effect of the activation time between the catalyst and the different aluminoxanes has been taken into consideration. On increasing the activation time between catalyst and the different aluminoxanes and TMA-free MAO, differences in the catalyst activities have been observed. UHMWPEs having a reduced number of entanglements have been synthesized activating the FI catalyst with MAO and TMA-free MAO. The obtained reactor powders can be solid-state processed below the melting temperature in order to obtain high modulus/high tenacity tapes used for body armor and vehicle protection applications

Metallic-like thermal conductivity in a lightweight insulator: solid-state processed Ultra High Molecular Weight Polyethylene tapes and films

Ultra High Molecular Weight Polyethylene with a reduced number of entanglements can be stretched in the solid state both uni- or biaxially to produce highly oriented tapes and films. The chain orientation, in combination with the reduced number of chain ends, is responsible for the high tensile modulus and tensile strength of the drawn materials, and, as we report here, also for the high thermal conductivity achieved through lattice movements. A property such as thermal conductivity in an electrical insulator makes UHMWPE tapes and films of great applicative interest. In-plane laser-flash thermal analysis has been applied to measure the thermal diffusivity of samples of different molecular weights stretched both uni- and biaxially, and a strong correlation has been found between the drawing ratio and the resulting in-plane thermal conductivity. Values of at least 40 W/m K have been achieved for UHMWPE having Mw comprised between 2 and 10 million, while higher values of 65 W/m K are observed for the higher Mw samples having relatively lesser number of chain ends. Surprisingly the biaxially stretched samples also show in-plane conductivity, with the highest value reaching 18 W/m K, comparable to stainless steel

High-toughness carbon cloth composites for low temperature applications

Carbon Fibre Reinforced Polymers based on a thermoplastic, high performance matrix such as Ultra High Molecular Weight Polyethylene have been produced using two different routes and it was found that in-situ polymerization of the matrix is a possible way forward to achieve a combination of high strength and high toughness in composites

Aluminoxane co-catalysts for the activation of a bis phenoxyimine titanium (IV) catalyst in the synthesis of disentangled ultra-high molecular weight polyethylene

New activation systems for the bis[N-(3-tert-butylsalicylidene)pentafluoroanilinato] Ti (IV) dichloride catalyst (FI) for the synthesis of ultra-high molecular weight polyethylene (UHMWPE) with reduced entanglement density are explored. Together with the well-studied FI catalyst-methylaluminoxane (MAO) catalytic system, different aluminoxanes, namely polymethylaluminoxane-improved performance (PMAO), modified methylaluminoxane type 12 (MMAO12) and type 3A (MMAO3A) have been used. The catalyst activity increases with the addition of a co-catalyst modifier (2,6-di-tert-butyl-4-methylphenol, BHT). For an example when using MMAO3A as co-catalyst in combination with BHT the catalyst activity increases by tenfold. The synthesized UHMWPEs have been characterized via rheology, differential scanning calorimetry and uniaxial solid-state deformation to evaluate the influence that the different co-catalysts have on the catalyst activation and the entangled state of the polymer. Entanglement density increases when PMAO is used as a co-catalyst influencing the rheological response of the polymer melt and melting kinetics of nascent powder. Mechanical properties increase when MMAO12 is used in place of MMAO3A as co-catalyst. However, the earlier reported mechanical properties of UHMWPE synthesized using the FI/MAO are found to be better than those obtained using the co-catalysts investigated in this study

High molecular weight polyethylene

The present invention pertains to a polyethylene polymer characterised by the following properties: A number average molecular weight Mn of at least 2.0* 105 g/mol, a weight average molecular weight of at least 2.0* 10 6 g/mol, a Mw/Mn ratio of above 6, and a strain hardening slope of below 0.10 N/mm at 135°C. It has been found that a polymer with these properties have be converted through solid state processing into films and fibers with good properties. A solid state processing process, films and fibers, and their use are also claimed

Methods and systems for synthesis of an ultra high molecular weight polymer

A method for controlling the physical state of an ultra-high molecular weight polymer to make the ultra-high molecular weight polymer suitable for further processing, and related polymers compositions methods and systems, wherein the method comprises combining a catalyst, monomers, and an additive, for a time and under condition to allow synthesis of a nascent polymer and eo-crystallization of the nascent polymer with the additive