Accurate analysis of wear debris is essential in understanding the processes that produce debris and a key step in development of more durable and biocompatible implants.

Aims Loosening of the tibial component after total knee arthroplasty (TKA) is a common indication for revision. Increasing the strength of the initial tibial implant/cement interface is desirable. There is little information about the surgical techniques that lead to the highest strength. We investigated the effects of eight variables on the strength of the initial tibial baseplate/cement interface. Materials and Methods A total of 48 tibial trays were cemented into acrylic holders using cement from two manufacturers, at three different times (early, normal, and late) using two techniques: cementing the tibial plateau or the plateau and the keel; and involving two conditions of contamination with marrow fat (at the metal/cement and cement/cement interfaces). Push-out tests were performed with load continuously recorded. Results Compared with normal conditions, early cementing increased the mean strength of the interface when using the two cements, Simplex and Palacos, by 48% and 72%, respectively. Late cementing reduced the strength by 47% and 73%, respectively. Cementing the keel increased the mean strength by 153% and 147%, respectively, for the two cements. Contamination of the metal/cement interface with fat reduced the mean strength by 99% and 94% for the two cements but adding cement to the underside of the tibial tray prior to insertion resulted in the mean strength being lowered by only 65% and 43%, respectively. Conclusion In order to maximize the strength of the tibial tray/cement interface, cement should be applied to the component soon after mixing, contamination of the interface should be avoided, and the keel and the plateau should be cemented.

The conservation of bone stock and the decrease of intraoperative acetabular fracture risk associated with revision surgery is a primary goal to improve the outcome of the procedure. The objective of this study was to evaluate and compare the performance of the Explant Acetabular Cup Removal System and the EZout Powered Acetabular Revision System in an in vitro model. Acetabular components were implanted into instrumented composite hemipelvises and divided into 2 groups, EZout System and Explant System. One experienced orthopedic surgeon and 1 orthopedic resident physician performed the removal procedures. The strains at various points in the periacetabular bone, the temperature at the implant-bone interface, the total time to removal, the torque applied to the implant and the amount of acetabular foam on each cup after extraction, as a surrogate for cavitary acetabular bone stock loss, were calculated for each test. Statistical analysis was conducted using 2-way multivariate analysis of variance followed by Tukey honestly significant difference multiple comparisons. The EZout System required an overall lower force and torque (P < 0.0001, both) during removal, producing lower strains in the surrounding composite bone. The procedure was faster (P < 0.0001) and less energy demanding with the EZout compared with the Explant. The amount of foam on the cup was on average less for the EZout than for the Explant (P < 0.05).We found that the EZout System is effective in achieving safe removal of a well-fixed acetabular component in an in vitro model of cementless fixation. This system should be considered as a reasonable alternative to manual removal techniques.

Background Numerous studies indicate highly crosslinked polyethylenes reduce the wear debris volume generated by hip arthroplasty acetabular liners. This, in turns, requires new methods to isolate and characterize them. Questions/purposes We describe a method for extracting polyethylene wear particles from bovine serum typically used in wear tests and for characterizing their size, distribution, and morphology.Methods Serum proteins were completely digested using an optimized enzymatic digestion method that prevented the loss of the smallest particles and minimized their clumping. Density-gradient ultracentrifugation was designed to remove contaminants and recover the particles without filtration, depositing them directly onto a silicon wafer. This provided uniform distribution of the particles and high contrast against the background, facilitating accurate, automated, morphometric image analysis. The accuracy and precision of the new protocol were assessed by recovering and characterizing particles from wear tests of three types of polyethylene acetabular cups (no crosslinking and 5 Mrads and 7.5 Mrads of gamma irradiation crosslinking). Results The new method demonstrated important differences in the particle size distributions and morphologic parameters among the three types of polyethylene that could not be detected using prior isolation methods. Conclusion The new protocol overcomes a number of limitations, such as loss of nanometer-sized particles and artifactual clumping, among others. Clinical Relevance The analysis of polyethylene wear particles produced in joint simulator wear tests of prosthetic joints is a key tool to identify the wear mechanisms that produce the particles and predict and evaluate their effects on periprosthetic tissues.

Background Recent evidence shows that despite high incidence of dementia in the very old, they exhibit significantly lower levels of AD neuropathology relative to younger persons with dementia. The levels and distributions of some synaptic proteins have been found to be associated with dementia severity, even in the oldest-old, but the molecular and functional nature of these deficits have not been studied in detail. Objective To assess the relationship of dementia with gene and protein expression of a panel of synaptic markers associated with different synaptic functions in young-, middle-, and oldest-old individuals. Design The protein and mRNA levels of seven synaptic markers (complexin-1, complexin-2, synaptophysin, synaptobrevin, syntaxin, SNAP-25, and septin-5) were compared in the brains of non-demented and demented individuals ranging from 70 to 103 years of age. Participants 111 brains were selected to have either no significant neuropathology or only AD-associated pathology (neuritic plaques (NPs) and neurofibrillary tangles (NFTs)). The cohort was then stratified into tertiles as young-old (70-81 years-old), middle-old (82-88), and oldest-old (89-103). Results The brains of persons with dementia evidenced significantly lower levels of gene and protein expression of synaptic markers regardless of age. Importantly, dementia was associated with reductions in all measured synaptic markers irrespective of their role(s) in synaptic function. Conclusions Although other dementia-associated hallmarks of AD neuropathology (NPs and NFTs) become less prominent with increasing age, synaptic marker abnormalities in dementia remain constant with increasing age and may represent an independent substrate of dementia spanning all ages.