S M Kurtz

..Although infection can be a devastating complication, due to its rarity it is difficult to characterize infection risk except in large patient populations...

..2%. The results of this interlaboratory research will be a useful basis for the development of a new oxidation index standard for the orthopedics community...

..The data collected in this study will be used to develop constitutive models based on the physics of polymer systems for predicting the thermomechanical behavior of conventional and crosslinked UHMWPE used in total joint replacements...

..The distinction between waviness and roughness is expected to be crucial for the comprehensive evaluation of wear surfaces after short-term implantation, when machining marks may be partially worn away or plastically deformed in vivo...

..However, even at 50 degrees C over a year of in vitro aqueous aging will be necessary to reproduce the oxidation levels observed in long-term implanted acetabular retrievals. (..

..The results of this experiment therefore supported our hypotheses that trace concentrations of Vitamin E, coupled with radiation treatment-but not resin grade-influence the mechanical and oxidative degradation behavior of UHMWPE...

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..For mature fields, such as total joint replacements and fracture fixation implants, radiolucency is an attractive but not necessarily critical material feature...

..The data support the use of both parametric and nonparametric methods to bracket the lower-bound failure prediction in order to simulate the failure threshold for UHMWPE...

..Polyethylene (PE) has been used in total disc replacements (TDRs) in Europe since the 1980s. However, the extent of surface damage of PE, including rim fracture and wear, after long-term implantation remains poorly understood...

..Although total disc replacements have been performed in Europe since the 1980s, this type of surgery is still new in the United States. The clinical performance of polyethylene in total disc replacements is still not well understood...

..g., age, gender) vary internationally? (3) How have the rates of TKA utilization changed over time?..

..Thus, the shear punch test represents an effective and complementary new tool in the armamentarium of miniature specimen mechanical testing methods for UHMWPE used in total joint replacement components...

..Therefore, both the 1370-cm(-1) and the 2022-cm(-1) reference peaks appear equally suitable for use in defining a standard method for calculating an oxidation index for UHMWPE...

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..In the future, the small punch test can be used to directly measure mechanical properties near the articulating surface of retrieved components...

..The data also illustrate the sensitivity of large deformation mechanical behavior and crystalline morphology to the method of crosslinking and resin of polyethylene...

..The results of this study suggest that with a polished metal shell, the presence of screw holes does not substantially increase abrasive backside wear when compared with the effects of backside nonconformity...

..Finally, the fourth part reviews the development and properties of crosslinked UHMWPE, a promising alternate biomaterial for total joint replacements...

..Thus, the results of this study support the hypothesis that the clinical performance of UHMWPE tibial inserts is related to the large-deformation mechanical behavior measured near the articulating surface...

..01, r(2) = 0.54-0.81). The results support the hypothesis that wear mechanisms of acetabular liners during hip simulator testing are related to surface morphology in conjunction with the mechanical behavior of the polymeric materials...

..However, the large interinstitutional variation suggests that absolute performance standards for the oxidation index of UHMWPE after accelerated aging may not be practical at the present time...

..Overall, our findings suggest that the Bionate 80A material has greater oxidative stability than ultra-high molecular weight polyethylene following gamma irradiation in air and exposure to a severe oxidative challenge...

..The oxidative stability observed in ArComXL suggests that the deformation-processed material may be suitable for air-permeable packaging and gas sterilization, which has thus far been reserved for remelted highly crosslinked UHMWPE...

..Consequently, the results of this study demonstrate that backside nonconformity and locking restraints substantially influence backside relative motion as well as load transfer at the liner/shell interface...

..Forty-eight CHARITE TDRs were retrieved from 41 patients after 7.8 years of average implantation. All implants were removed because of intractable back pain and/or facet degeneration. Three unimplanted implants served as controls...

..The augmented hybrid constitutive model will be used as a critical building block in future studies of fatigue, failure, and wear of UHMWPE...

..The ultimate goal of this research is to develop the capability to perform local measurements of material tensile and static fracture properties in as-manufactured, as-sterilized and as-retrieved UHMWPE components...

..Most importantly, from a practical perspective, these four key material properties for the Hybrid constitutive model can be measured by relatively simple uniaxial tension or compression tests...

..In addition a new hybrid model is proposed, which incorporates many features of the previous theories. This hybrid model is shown to most effectively predict the experimentally observed mechanical behavior of UHMWPE...

..The purpose of this study was to quantify the extent to which the mechanical properties and oxidation of conventional polyethylene acetabular liners treated with gamma sterilization in air change in vivo...

..Advances in these types of implants have the potential for major clinical impact in the coming decade, due to the large number of patients seeking treatment of knee arthritis as well as back pain, neck pain, and radiculopathy...

..These results lay the foundation for future developments of damage and wear models capable of predicting multiaxial failure under cyclic loading conditions...

..Rim surface damage, however, was observed in only 3 (5%) of 60 cases. Retrieval analysis of the 3 rim-damaged liners did not reveal an association between surface damage and the reasons for revision...

..The presence of bone cement immediately following kyphoplasty has only a slight effect on the stress magnitudes or distributions in adjacent vertebrae...

..Our long-term goal in this research is to develop miniature-specimen fatigue testing techniques for characterization of retrieved UHMWPE inserts...

..In the future, the material model data presented in this study will enable more accurate prediction of the stresses and strains in UHMWPE components following gamma sterilization in air and subsequent in vivo degradation...

..This study provides improved understanding of well-consolidated Poly II long-term retrievals and also motivation to revisit carbon fiber-reinforced polymeric bearings for joint replacement in the twenty-first century...

..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...

..Increased pain incidence for short-stem patients may be related to decreased implant instability and increased interface relative motion...

..Photogrammetry has a broad range of applicability since it is size- and design-independent. A minimal amount of off-the-shelf equipment is needed for the procedure and no proprietary knowledge of the implant is needed...

..The remodelling of bone seen during revision of failed Birmingham hip resurfacing implants appears to be consistent with the predictions of our finite element analysis...

..We conclude that in vivo degradation should be included among the list of potential long-term failure modes for modular polyethylene components for total hip arthroplasty...

..These data show bone loading and interface fixation trends emanating from valgus and varus implant positions that will be of interest to practicing physicians...

..The results of this study strongly support the hypothesis that the degradation of mechanical properties for the liners occurred during implantation...

..The model was implanted with a fixed-bearing TDR (ProDisc-L) at 2 surgically relevant positions and exercised about the 3 anatomic axes. Facet forces, range of motion (RoM), and vertebral body strains were evaluated...

..In addition, this review is based on an understanding of the causes of failure of revision hip resurfacing arthroplasty, which is essential to help guide research, implant design, and clinical decision-making...

..9 and 3.8 mm-thick liners, respectively. Although pinching increases liner stresses, polyethylene fracture is highly unlikely, and the volumetric wear rates are likely to be low compared to conventional polyethylene...

..A validated nonlinear three-dimensional finite element model of a single lumbar motion segment (L3-L4) was used to evaluate a range of moduli for ideally conforming nucleus replacement devices...

..In addition, the potential influence of the different sterilization processes on the wear performance of the polyethylene components was examined...

..OBJECTIVES/PURPOSES: We therefore evaluated the risk of subsequent revision after primary and revision TJA in the elderly (65 years or older) patient population and identified corresponding patient risk factors...

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..Epidemiological study using national administrative data...

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..Therefore, subsequent adjacent level fractures may be related to the underlying etiology (weakening of the bone) rather than the surgical intervention...

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..Kyphoplasty patients had a 34% greater adjusted life expectancy than vertebroplasty patients...

..Furthermore, infrared spectroscopy alone appeared to provide excellent insight into the oxidation and crystallization state of the in vivo oxidized polyethylene...

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..Our findings support the general belief that longer procedures are associated with the greater probability of complications...

..This is the first study to establish the incidence and risk factors associated with early onset and delayed periprosthetic joint infection in the Medicare patient population...

..LEVEL OF EVIDENCE: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence...

..Level of Evidence: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence...

..26% for knees compared to rural (0.61% for hips and 0.69% for knees) and urban-teaching hospitals (0.73% for hips and 0.77% for knees). We found an increasing number of joint arthroplasties being diagnosed with periprosthetic infection...

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..We conclude that the variability in polyethylene properties observed in this small study was not clinically significant for these short-term-implanted, annealed cross-linked liners...

..Level of Evidence: Prognostic study, level II-1 (retrospective study). See Guidelines for Authors for a complete description of levels of evidence...

..This analysis provides baseline data for future investigation of the influence of procedure duration on total joint arthroplasty outcomes from a national perspective...

..The revision caseload of surgeons has increased over time, particularly for surgeons with the highest caseloads...

..We evaluated the national trends for the implantation of PMs and ICDs including the burden of device replacement...

..Scanning electron microscopy examination of the fracture surfaces demonstrated that the virgin treatment group failed in a more ductile manner than the two highly crosslinked treatment groups...

..Radical changes in implant design may be necessary for long-term maintenance of supporting structures in the reconstructed acetabulum...

..To the authors' knowledge, this is the first study that relates elevated oxidation and hydroperoxide content in gamma-sterilized PE components to certain types of contemporary, polymeric barrier packaging...

..Thus, the role of laboratory studies is to isolate relevant aspects of performance by cup design and to predict the risk-benefit ratios in patients requiring total hip replacement...

..Newer second-generation methods of cross-linking polyethylene include the use of vitamin E, which quenches free radicals and demonstrates promise in providing low wear and desirable mechanical properties...

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..Mechanical tests as well as computational material and structural models should be developed to evaluate the combined effect of material and geometry (structure) on fracture resistance under clinically relevant loading conditions...

..However, untoward complexities occurring in vivo, such as impingement or third-body challenge, can appreciably compromise wear performance even for implants that are well-designed in terms of bearing surface stress minimization...

..Removal of the SB Charité artificial disc is feasible but with inherent risks. Removal of the disc prosthesis gives slightly better results than posterior fusion alone after a follow-up of at least 1 year...

..The findings of this study support that microstructural evolution during compressive deformation is a function of UHMWPE formulation, as affected by irradiation and post-irradiation heat treatment...

..A clinical case series of 4 patients undergoing anterior lumbar revision due to failure of total disc replacement surgery...

..We examined the association between hospital and surgeon procedure volume and total hip arthroplasty revision rates in the Medicare population at six months to eight years postoperatively...