Majority of ultra-high molecular weight polyethylene (UHMWPE) medical devices used in total joint arthroplasty are crosslinked using gamma radiation to improve wear resistance. Alternative methods of crosslinking are urgently needed to replace gamma radiation due to rapid decline in its supply. Peroxide crosslinking is a candidate method with widespread industrial applications. Oxidative stability and biocompatibility, which are critical requirements for medical device applications, can be achieved using vitamin-E as an additive and by removing peroxide by-products through high temperature melting, respectively. We investigated compression molded UHMWPE/vitamin-E/di-cumyl peroxide blends followed by high-temperature melting in inert gas as a material candidate for tibial knee inserts. Wear resistance increased and mechanical properties remained largely unchanged. Oxidation induction time was higher than most of the other clinically available formulations. The material passed the local-end point biocompatibility tests per ISO 10993. Compounds found in exhaustive extraction were of no concern with margin-of-safety values well above the accepted level, indicating a desirable toxicological risk profile. Peroxide crosslinked, vitamin-E stabilized, and high temperature melted UHMWPE has recently been cleared for clinical use in tibial knee inserts. With all the salient characteristics needed in a material that can provide superior long-term performance in total joint patients, peroxide crosslinking can replace gamma radiation crosslinking of UHMWPE for use in all total joint replacement implant including acetabular liners.
Ultra-high molecular weight polyethylene (UHMWPE) can provide local sustained delivery of therapeutics1,2. For example, it can deliver analgesics to address post-arthroplasty pain2. Given that several analgesics, such as bupivacaine (anesthetic) and tolfenamic acid (NSAID), were shown to possess antibacterial activity against Bupivacaine and tolfenamic acid were incorporated into UHMWPE via phase-separated compression molding. Drug release from the prepared samples was measured using high-performance liquid chromatography. Antibacterial studies of the obtained materials were conducted against methicillin-sensitive, and methicillin-resistant Introduction
Methods
Vitamin E-diffused, highly crosslinked polyethylene (VEPE) and porous titanium-coated (PTC) shells were introduced in total hip arthroplasty (THA) to reduce the risk of aseptic loosening. The purpose of this study was: 1) to compare the wear properties of VEPE to moderately crosslinked polyethylene; 2) to assess the stability of PTC shells; and 3) to report their clinical outcomes at seven years. A total of 89 patients were enrolled into a prospective study. All patients received a PTC shell and were randomized to receive a VEPE liner (n = 44) or a moderately crosslinked polyethylene (ModXLPE) liner (n = 45). Radiostereometric analysis (RSA) was used to measure polyethylene wear and component migration. Differences in wear were assessed while adjusting for body mass index, activity level, acetabular inclination, anteversion, and head size. Plain radiographs were assessed for radiolucency and patient-reported outcome measures (PROMs) were administered at each follow-up.Aims
Patients and Methods
Periprosthetic osteolysis (PPO) gradually became the single dominant late failure mechanism of total hip replacements. It afflicted 1 million patients worldwide, leading to countless, difficult revision operations. The widespread adoption of highly cross-linked polyethylene (XLPE) drastically reduced that disease. But going beyond that remarkable reversal, two further substantial consequences have resulted: A) a major reduction in revision operations and B) a major reduction in aggregate costs of total replacement surgery. This paper assembles data on the decrease in revision rates and uses them to estimate the massive reduction in total hip surgery costs. Review the literature produced registry data and controlled studies data establishing that XLPE reduced the “all cause” revision rate over the first 15 years of follow-up of total hip replacements at least in half, and often more. A conservative estimate of the number of revisions annually in the United States is 50,000. A conservative estimate of the average, integrated cost for a THR revision in the United States is $50,000, meaning that the costs of these revisions annually is at least $2.5 billion. Using a very conservative figure of just 40% for the percent reduction in revision surgery resulting from the use of XLPE reduces this burden by at least $1 billion annually.Introduction
Methods
Ceramic heads are used in hip revision surgery to mitigate corrosion concerns. Manufacturers recommend using a pristine titanium sleeve in conjunction with a well-fixed metal stem to prevent early failure of the ceramic head. However, the influence of impact force, head size, and sleeve offset on pull-off strength and seating displacement of a revision head assembly is not fully understood. Therefore, the purpose of this study was to investigate the pull-off strength and displacement of commercially available revision ceramic heads and titanium taper sleeve offsets (BIOLOX OPTION, CeramTec GmbH, Plochingen, Germany) while covering a range of clinically relevant impaction forces. Two head sizes (28 mm, n = 12 and 36 mm, n = 12) and two taper adapter sleeve offsets (small, n = 12 and extra-large, n = 12) were tested in this study. A dynamic impaction rig was constructed to seat the head, sleeve, and stem assembly (Fig. 1). Consistent impaction forces were achieved by dropping a hammer fixed to a lever arm from a pre-determined height onto a standard impactor instrumented with a piezoelectric force sensor (PCB Piezotronics Inc.). Axially applied forces of 2 kN and 6 kN were used to cover a range of typical impaction forces. Three non-contact differential variable reluctance transducers (LORD Sensing Systems) were used to track the displacement of the head relative to the stem. Subsequently, samples were transferred to a servo hydraulic testing machine, and a pull-off test was carried out per ISO 7206–10 to measure the disassembly force.Introduction
Methods
