Exponent

About: Exponent is a company organization based out in Menlo Park, California, United States. It is known for research contribution in the topics: Population & Risk assessment. The organization has 1589 authors who have published 2680 publications receiving 88140 citations.

In Vivo Oxidation Contributes to Delamination but not Pitting in Polyethylene Components for Total Knee Arthroplasty

Abstract: The aim of this study was to better understand how in vivo oxidation contributes to fatigue damage in total knee arthroplasty (TKA). A total of 119 tibial inserts were consecutively collected after revision surgery. Of the 119 polyethylene retrievals, 29 were gamma sterilized in air (historical), whereas the remaining 90 were gamma sterilized in nitrogen (conventional). Surface damage assessment and characterization of oxidation were performed on all the retrievals. Delamination was significantly more prevalent and extensive in the longer-term, highly oxidized, historical tibial inserts. Pitting damage, in contrast, seemed to be equally prevalent between both retrieval groups and was not correlated with in vivo oxidation. Our findings support our hypothesis that in vivo oxidation is a contributing factor to delamination, but not pitting, in TKA. Despite the lower oxidation displayed by conventional retrievals, this study provides strong evidence that delamination secondary to in vivo oxidation may occur during the second decade of implantation.

Evaluation of exposure to arsenic in residential soil.

Abstract: In response to concerns regarding arsenic in soil from a pesticide manufacturing plant, we conducted a biomonitoring study on children younger than 7 years of age, the age category of children most exposed to soil. Urine samples from 77 children (47% participation rate) were analyzed for total arsenic and arsenic species related to ingestion of inorganic arsenic. Older individuals also provided urine (n = 362) and toenail (n = 67) samples. Speciated urinary arsenic levels were similar between children (geometric mean, geometric SD, and range: 4.0, 2.2, and 0.89-17.7 microg/L, respectively) and older participants (3.8, 1.9, 0.91-19.9 microg/L) and consistent with unexposed populations. Toenail samples were < 1 mg/kg. Correlations between speciated urinary arsenic and arsenic in soil (r = 0.137, p = 0.39; n = 41) or house dust (r = 0.049, p = 0.73; n = 52) were not significant for children. Similarly, questionnaire responses indicating soil exposure were not associated with increased urinary arsenic levels. Relatively low soil arsenic exposure likely precluded quantification of arsenic exposure above background.

Which Design and Biomaterial Factors Affect Clinical Wear Performance of Total Disc Replacements? A Systematic Review

Abstract: Background Total disc replacement was clinically introduced to reduce pain and preserve segmental motion of the lumbar and cervical spine. Previous case studies have reported on the wear and adverse local tissue reactions around artificial prostheses, but it is unclear how design and biomaterials affect clinical outcomes.

What is the correlation of in vivo wear and damage patterns with in vitro TDR motion response

Abstract: STUDY DESIGN This study combined the evaluation of retrieved total disc replacements (TDRs) with a biomechanical study using human lumbar spines. Thirty-eight CHARITE TDRs were retrieved from 32 patients after 7.3 years average implantation. All implants were removed because of intractable back pain and/or facet degeneration. In parallel, 20 new implants were evaluated at L4-L5 and L5-S1 in an in vitro lumbar spine model. OBJECTIVE The purpose of this study was to correlate wear and damage patterns in retrieved TDRs with motion patterns observed in an in vitro lumbar spine model. We also sought to determine whether one-sided wear and motion patterns were associated with greater in vivo wear. SUMMARY OF BACKGROUND DATA The comparison of polyethylene wear in TDRs after long-term implantation to those tested using an in vitro model had not yet been investigated. METHODS The wear patterns of each retrieved PE core was analyzed at the rim and dome. Thirty-five cores were further analyzed using MicroCT to determine the penetration symmetry. For the in vitro study the implants were tested under physiologic loads using a validated cadaveric model. Motion patterns of the in vitro-tested implants were tracked using sequential video-fluoroscopy. RESULTS Fifteen of 35 retrieved cores (43%) displayed one-sided wear patterns. Significant correlations were observed between implantation time and penetration and penetration rate. In the in vitro study, there was evidence of motion at both articulations, motion at both articulation but predominantly at the top articulation, and solelyat the top articulation. Core entrapment and pinching was observed and associated with visual evidence of core bending or deformation. CONCLUSION This is the first study to directly compare the long-term PE wear and damage mechanisms in TDR retrievals with the motion patterns generated by a validated in vitro cadaveric testing model. The retrievals exhibited wear patterns consistent with the in vitro testing.