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The sources of fluids and metals in porphyry systems of continental-collision settings are poorly constrained. Mercury isotopes display unique mass-independent fractionation (expressed as Δ 199 Hg) and may provide important constraints on metal and volatile sources given that Hg is a highly volatile metal. Here, we report Hg isotope data on ore-forming porphyries, barren magmatic rocks, and mantle-derived mafic magmas from southern Tibet. The fertile porphyries and coeval mafic magmas display mainly positive Δ 199 Hg values (up to +0.25 per mil), while Δ 199 Hg values in barren magmatic rocks and mafic magmas are largely negative (-0.54 to 0.00 per mil). The positive Δ 199 Hg values observed here are consistent with seawater and marine sediments, suggesting that the ultimate source of fluids involved in the genesis of post-subduction porphyry copper deposits was the mantle lithosphere metasomatized by previous oceanic plate subduction. Our Hg isotope data provide an alternative view to current metallogenetic models on collisional porphyry systems that focus on melting of the lower continental crust.

Our nanomineralogical investigation of melt inclusions in corundum xenocrysts from the Mt. Carmel area, Israel has revealed seven IMA-approved new minerals since 2021. We report here four new oxide minerals and one new alloy mineral. Magnéliite (Ti 3+ 2 Ti 4+ 2 O 7 ; IMA 2021-111) occurs as subhedral crystals, ~4 μm in size, with alabandite, zirconolite, Ti,Al,Zr-oxide, and hibonite in corundum Grain 767-1. Magnéliite has an empirical formula (Ti 3+ 1.66 Al 0.13 Ti 4+ 0.15 Mg 0.10 Ca 0.01 Sc 0.01 ) Σ2.06 (Ti 4+ 1.93 Zr 0.08 ) Σ2.01 O 7 and the triclinic P 1¯ Ti 4 O 7 -type structure with the cell parameters: a = 5.60(1) Å, b = 7.13(1) Å, c = 12.47(1) Å, α = 95.1(1)°, β = 95.2(1)°, γ = 108.7(1)°, V = 466(2) Å 3 , Z = 4. Ziroite (ZrO 2 ; IMA 2022-013) occurs as irregular crystals, ~1-4 μm in size, with baddeleyite, hibonite, and Ti,Al,Zr-oxide in corundum Grain 479-1a. Ziroite has an empirical formula (Zr 0.72 Ti 4+ 0.26 Mg 0.02 Al 0.02 Hf 0.01 ) Σ1.03 O 2 and the tetragonal P 4 2 / nmc zirconia(HT)-type structure with the cell parameters: a = 3.60(1) Å, c = 5.18(1) Å, V = 67.1(3) Å 3 , Z = 2. Sassite (Ti 3+ 2 Ti 4+ O 5 ; IMA 2022-014) occurs as subhedral-euhedral crystals, ~4-16 μm in size, with Ti,Al,Zr-oxide, mullite, osbornite, baddeleyite, alabandite, and glass in corundum Grain 1125C1. Sassite has an empirical formula (Ti 3+ 1.35 Al 0.49 Ti 4+ 0.08 Mg 0.07 ) Σ1.99 (Ti 4+ 0.93 Zr 0.06 Si 0.01 ) Σ1.00 O 5 and the orthorhombic Cmcm pseudobrookite-type structure with the cell parameters: a = 3.80(1) Å, b = 9.85(1) Å, c = 9.99(1) Å, V = 374(1) Å 3 , Z = 4. Mizraite-(Ce) (Ce(Al 11 Mg)O 19 ; IMA 2022-027) occurs as euhedral crystals, <1-14 μm in size, with Ce-silicate, Ti-sulfide, Ti,Al,Zr-oxide, ziroite, and thorianite in corundum Grain 198-8. Mizraite-(Ce) has an empirical formula (Ce 0.76 Ca 0.10 La 0.07 Nd 0.01 ) Σ0.94 (Al 10.43 Mg 0.84 Ti 3+ 0.60 Si 0.09 Zr 0.04 ) Σ12.00 O 19 and the hexagonal P 6 3 / mmc magnetoplumbite-type structure with the cell parameters: a = 5.61(1) Å, c = 22.29(1) Å, V = 608(2) Å 3 , Z = 2. Yeite (TiSi; IMA 2022-079) occurs as irregular-subhedral crystals, 1.2-3.5 μm in size, along with wenjiite (Ti 5 Si 3 ) and zhiqinite (TiSi 2 ) in Ti-Si alloy inclusions in corundum Grain 198c. Yeite has an empirical formula (Ti 0.995 Mn 0.003 V 0.001 Cr 0.001 )(Si 0.996 P 0.004 ) and the orthorhombic Pnma FeB-type structure with the cell parameters: a = 6.55(1) Å, b = 3.64(1) Å, c = 4.99(1) Å, V = 119.0(4) Å 3 , Z = 4. The five minerals are high-temperature oxide or alloy phases, formed in melt pockets in corundum xenocrysts derived from the upper mantle beneath Mt. Carmel.

Kimberlites are volatile-rich, occasionally diamond-bearing magmas that have erupted explosively at Earth's surface in the geologic past 1-3 . These enigmatic magmas, originating from depths exceeding 150 km in Earth's mantle 1 , occur in stable cratons and in pulses broadly synchronous with supercontinent cyclicity 4 . Whether their mobilization is driven by mantle plumes 5 or by mechanical weakening of cratonic lithosphere 4,6 remains unclear. Here we show that most kimberlites spanning the past billion years erupted about 30 million years (Myr) after continental breakup, suggesting an association with rifting processes. Our dynamical and analytical models show that physically steep lithosphere-asthenosphere boundaries (LABs) formed during rifting generate convective instabilities in the asthenosphere that slowly migrate many hundreds to thousands of kilometres inboard of rift zones. These instabilities endure many tens of millions of years after continental breakup and destabilize the basal tens of kilometres of the cratonic lithosphere, or keel. Displaced keel is replaced by a hot, upwelling mixture of asthenosphere and recycled volatile-rich keel in the return flow, causing decompressional partial melting. Our calculations show that this process can generate small-volume, low-degree, volatile-rich melts, closely matching the characteristics expected of kimberlites 1-3 . Together, these results provide a quantitative and mechanistic link between kimberlite episodicity and supercontinent cycles through progressive disruption of cratonic keels., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)

Decompressional melting of asthenosphere under spreading centers has been accepted to produce oceanic lithospheric mantle with vertical compositional variations, but these gradients are much smaller than those observed from ophiolites, which clearly require additional causes. Here we conduct high-density sampling and whole-rock and mineral analyses of peridotites across a Tibetan ophiolitic mantle section (~2 km thick), which shows a primary upward depletion (~12% difference) and local more-depleted anomalies. Thermodynamic modeling demonstrates that these features cannot be produced by decompressional melting or proportional compression of residual mantle, but can be explained by melt-peridotite reaction with lateral melt/rock ratio variations in an upwelling asthenospheric column, producing stronger depletion in the melt-focusing center and local zones. This column splits symmetrically and flows to become the horizontal uppermost lithospheric mantle, characterized by upward depletion and local anomalies. This model provides insights into melt extraction and uppermost-mantle origin beneath spreading centers with high melt fluxes., (© 2022. The Author(s).)

Routine follow-up approximately every 2 to 5 years after total hip arthroplasty (THA) is a common practice. However, although patients are informed of the importance of follow-up, our mean follow-up rate for patients after standard non-metal-on-metal (MOM) THA is only 19%. The US Food and Drug Administration has released several statements on the importance of follow-up every 2 years after MOM THA. With the potential risks of MOM THA apparently widely known, we report on our ability to obtain timely follow-up at 2 separate centers. Two separate centers performed 570 MOM THA procedures between 2002 and 2010. An attempt was made to reach every patient by either telephone or letter to obtain ion levels, radiographs, and examinations. Repeat telephone calls and/or letters to those not reached were made annually. Patients were told of the unique importance of follow-up at each contact. Of the patients, 43% had not been seen within the past 5 years, and only 26% had been seen within the past 2 years. Only 61% had their first measurement of ion levels, and only 30% of patients had a second set of measurement of ion levels. A total of 48 revisions occurred in this group, and 36 patients died. Despite the apparent widespread dissemination of information regarding the potential risks of MOM THA and concerted efforts to contact patients for follow-up, we have been able to achieve a follow-up rate of only 26%. This rate is only marginally better than the mean follow-up for non-MOM THA in our practices. The implications of this poor follow-up are unknown. [ Orthopedics . 2022;45(4):e196-e200.].

Background: Standard treatment for periprosthetic joint infection (PJI) involves 2-stage exchange with placement of an antibiotic-impregnated cement spacer (ACS). Conflicting evidence exists on the role of ACS in development of acute kidney injury (AKI) after first-stage surgery. In this randomized clinical trial, we aimed to compare the incidence of AKI between the first-stage of a planned 2-stage exchange vs 1-stage exchange. This study design isolates the effect of the ACS in otherwise identical treatment groups., Methods: The primary outcome variable was AKI, defined as a creatinine ≥1.5 times baseline or an increase of ≥0.3 mg/dL. Risk factors for AKI were evaluated using bivariate statistical tests and multivariable logistic regression., Results: Patients who underwent the first stage of a planned 2-stage exchange were significantly more likely to develop AKI compared with the 1-stage exchange group (15 [22.7%] vs 4 [6.6%], P = .011). On multivariable regression analysis, ACS placement (odds ratio 7.48, 95% confidence limit 1.77-31.56) and chronic kidney disease (odds ratio 3.84, 95% confidence limit 1.22-12.08) were independent risk factors for AKI., Conclusion: Our study provides evidence that high-dose antibiotic cement spacers for treatment of PJI are an independent risk factor for AKI. Therefore, efforts to minimize nephrotoxicity should be employed in revision for PJI when possible., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Earth's carbon cycle is strongly influenced by subduction of sedimentary material into the mantle. The composition of the sedimentary subduction flux has changed considerably over Earth's history, but the impact of these changes on the mantle carbon cycle is unclear. Here, we show that the carbon isotopes of kimberlite magmas record a fundamental change in their deep-mantle source compositions during the Phanerozoic Eon. The 13 C/ 12 C of kimberlites before ~250 Ma preserves typical mantle values, whereas younger kimberlites exhibit lower and more variable ratios-a switch coincident with a recognized surge in kimberlite magmatism. We attribute these changes to increased deep subduction of organic carbon with low 13 C/ 12 C following the Cambrian Explosion when organic carbon deposition in marine sediments increased significantly. These observations demonstrate that biogeochemical processes at Earth's surface have a profound influence on the deep mantle, revealing an integral link between the deep and shallow carbon cycles.

Oxygen isotope ratios in mantle-derived magmas that differ from typical mantle values are generally attributed to crustal contamination, deeply subducted crustal material in the mantle source or primordial heterogeneities. Here we provide an alternative view for the origin of light oxygen-isotope signatures in mantle-derived magmas using kimberlites, carbonate-rich magmas that assimilate mantle debris during ascent. Olivine grains in kimberlites are commonly zoned between a mantle-derived core and a magmatic rim, thus constraining the compositions of both mantle wall-rocks and melt phase. Secondary ion mass spectrometry (SIMS) analyses of olivine in worldwide kimberlites show a remarkable correlation between mean oxygen-isotope compositions of cores and rims from mantle-like 18 O/ 16 O to lower 'crustal' values. This observation indicates that kimberlites entraining low- 18 O/ 16 O olivine xenocrysts are modified by assimilation of low- 18 O/ 16 O sub-continental lithospheric mantle material. Interaction with geochemically-enriched domains of the sub-continental lithospheric mantle can therefore be an important source of apparently 'crustal' signatures in mantle-derived magmas., (© 2021. The Author(s).)

Aggregates of corundum crystals with skeletal to hopper morphology occur in pyroclastic rocks erupted from Cretaceous basaltic volcanoes on Mt Carmel, N. Israel. The rapid growth of the crystals trapped volumes of the parental Al 2 O 3 -supersaturated melt; phenocrysts of tistarite (Ti 2 O 3 ) in the trapped melts indicate crystallization at oxygen fugacities 6-7 log units below the Iron-Wüstite buffer (fO 2  = ΔIW - 6 to - 7), induced by fluxes of mantle-derived CH 4 -H 2 fluids. Cathodoluminescence images reveal growth zoning within the individual crystals of the aggregates, related to the substitution of Ti 3+ in the corundum structure. Ti contents are < 0.3 wt% initially, then increase first linearly, then exponentially, toward adjacent melt pockets to reach values > 2 wt%. Numerical modelling indicates that the first skeletal crystals grew in an open system, from a moving magma. The subsequent linear increase in Ti reflects growth in a partially closed system, with decreasing porosity; the exponential increase in Ti close to melt pockets reflects closed-system growth, leading to dramatic increases in incompatible-element concentrations in the residual melts. We suggest that the corundum aggregates grew in melt/fluid conduits; diffusion modelling implies timescales of days to years before crystallization was terminated by explosive eruption. These processes probably operate in explosive volcanic systems in several tectonic settings.

Explantation and placement of an antibiotic spacer is a well-recognized treatment for periprosthetic infection after total knee replacement. Although static spacers may be occasionally indicated, many patients benefit from an articulating spacer that preserves the function and range of motion. However, many articulating spacer techniques provide an imbalanced cement-on-cement articulating knee that cannot tolerate full weight-bearing or provide adequate stability for daily function. A more durable articulating spacer may be ideal by permitting unrestricted weight-bearing, a functional range of motion, and potentially delayed reimplantation for medically complex patients. We present our evolved and reproducible technique for gap-balanced articulating spacers using cement augments and dowel stems. The result is a stable construct that permits full weight-bearing and a functional range of motion., (© 2020 The Authors.)

The occurrence of moissanite (SiC), as xenocrysts in mantle-derived basaltic and kimberlitic rocks sheds light on the interplay between carbon, hydrogen and oxygen in the lithospheric and sublithospheric mantle. SiC is stable only at ƒ O 2  < ΔIW-6, while the lithospheric mantle and related melts commonly are considered to be much more oxidized. SiC grains from both basaltic volcanoclastic rocks and kimberlites contain metallic inclusions whose shapes suggest they were entrapped as melts. The inclusions consist of Si 0  + Fe 3 Si 7  ± FeSi 2 Ti ± CaSi 2 Al 2  ± FeSi 2 Al 3  ± CaSi 2 , and some of the phases show euhedral shapes toward Si 0 . Crystallographically-oriented cavities are common in SiC, suggesting the former presence of volatile phase(s), and the volatiles extracted from crushed SiC grains contain H 2  + CH 4  ± CO 2  ± CO . Our observations suggest that SiC crystalized from metallic melts (Si-Fe-Ti-C ± Al ± Ca), with dissolved H 2  + CH 4  ± CO 2  ± CO derived from the sublithospheric mantle and concentrated around interfaces such as the lithosphere-asthenosphere and crust-mantle boundaries. When mafic/ultramafic magmas are continuously fluxed with H 2  + CH 4 they can be progressively reduced, to a point where silicide melts become immiscible, and crystallize phases such as SiC. The occurrence of SiC in explosive volcanic rocks from different tectonic settings indicates that the delivery of H 2  + CH 4 from depth may commonly accompany explosive volcanism and modify the redox condition of some lithospheric mantle volumes. The heterogeneity of redox states further influences geochemical reactions such as melting and geophysical properties such as seismic velocity and the viscosity of mantle rocks., Competing Interests: Conflict of interest The authors declare that they have no conflict of interest., (Copyright © 2020 Science China Press. Published by Elsevier B.V. All rights reserved.)

Background: Irrigation and debridement is an attractive treatment option for acute perioperative and acute hematogenous periprosthetic hip infections. We ask the following questions: (1) What are the results of a two-stage reimplantation if preceded by debridement, antibiotics, and implant retention (DAIR) compared with two-stage reimplantation without an antecedent DAIR? and (2) Do McPherson Musculoskeletal Infection Society (MSIS) host criteria influence results?, Methods: A total of 114 patients were treated with two-stage exchange for periprosthetic hip infection. Sixty-five patients were treated initially with a two-stage exchange, whereas 49 patients underwent an antecedent DAIR before a two-stage exchange. Patients were classified based on MSIS host criteria. Demographics demonstrated homogeneity between cohorts. Failure was defined as return to the operating room for infection, draining sinus, or systemic infection., Results: Treatment failure occurred in 42.9% (21 of 49) of patients treated with an antecedent DAIR. In contrast, treatment failure occurred in only 12.3% (8 of 65) of two-stage only procedures ( P < .001). Relative risk of return to the operating room after a two-stage reimplantation with an antecedent DAIR compared with initial resection was 4.52 (95% confidence interval: 1.71, 11.9). MSIS host grading was similar between groups and did not influence the rate of failure in a regression model. The DAIR cohort was also found to consume more resources in terms of hospitalization length and operative procedures ( P < .001)., Conclusions: Two-stage exchange procedures for prosthetic hip infections have a higher failure rate and consume more health-care resources when preceded by a failed DAIR. Surgeons and patients should be aware that a failed DAIR may compromise the results of future two-stage procedures., (© 2020 The Authors.)

Introduction: Screening protocols for asymptomatic patients with metal on metal (MoM) total hip arthroplasty (THA) are evolving. Most surgeons began screening patients around 2010 by obtaining cobalt (Co) and chromium (Cr) metal ion levels. There is currently no data available to guide repeat screening in this familiar clinical scenario. Therefore, the following study evaluated how metal ion levels change after an initial metal ion level in patients with MoM THAs., Materials and Methods: 171 consecutive patients (265 hips) underwent primary MoM THA. All patients had at least one Co and Cr ion level draw. 84 patients (136 hips) had 2 ion level draws. Ion levels were divided into elevated levels (⩾4.5 ppb) and normal levels (<4.5 ppb). The probability of an ion level returning elevated after an initial normal level was identified. Additionally, a threshold value was determined that reliably identified every patient that did not subsequently rise above 4.5 ppb., Results: 12 metal ion levels were ⩾4.5 ppb on the first lab draw. On the second draw, all 12 remained ⩾4.5 ppb. Of the 121 hips with initial metal ion levels <4.5 ppb, 5 metal ion levels became ⩾4.5 ppb. Utilising an initial screening cutoff of 3.0 ppb, no patient was identified with a second lab value ⩾4.5 ppb., Discussion: Initial metal ion levels reliably predicted those that would remain elevated or remain normal with a subsequent metal ion level. An initial metal ion level above 3.0 ppb may represent a cutoff at which further workup is necessary.

Quantifying the compositional evolution of mantle-derived melts from source to surface is fundamental for constraining the nature of primary melts and deep Earth composition. Despite abundant evidence for interaction between carbonate-rich melts, including diamondiferous kimberlites, and mantle wall rocks en route to surface, the effects of this interaction on melt compositions are poorly constrained. Here, we demonstrate a robust linear correlation between the Mg/Si ratios of kimberlites and their entrained mantle components and between Mg/Fe ratios of mantle-derived olivine cores and magmatic olivine rims in kimberlites worldwide. Combined with numerical modeling, these findings indicate that kimberlite melts with highly variable composition were broadly similar before lithosphere assimilation. This implies that kimberlites worldwide originated by partial melting of compositionally similar convective mantle sources under comparable physical conditions. We conclude that mantle assimilation markedly alters the major element composition of carbonate-rich melts and is a major process in the evolution of mantle-derived magmas., (Copyright © 2020 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).)

Background: Posterior-stabilized total knee arthroplasty (TKA) with gradually variable radii (G-curve) femoral condylar geometry is now available. It is believed that a G-curve design would lead to more mid-flexion stability leading to reduced incidence of paradoxical anterior slide. The objective of this study was to assess the in vivo kinematics for subjects implanted with this type of TKA under various conditions of daily living., Methods: Tibiofemoral kinematics of 35 patients having posterior-stabilized TKA with G-curve design were analyzed using fluoroscopy while performing three activities: weight-bearing deep knee bend, gait, and walking down a ramp. The subjects were assessed for range of motion, condylar translation, axial rotation, cam-spine engagement, and condylar lift-off., Results: The average weight-bearing flexion during deep knee bend was 111.4°. On average, the subjects exhibited 5.4 mm of posterior rollback of the lateral condyle and 2.0 mm of the medial condyle from full extension to maximum knee flexion. The femur consistently rotated externally with flexion, and the average axial rotation was 5.2°. Overall movement of the condyles during gait and ramp-down activity was small. No incidence of condylar lift-off was observed., Conclusion: Subjects in this study experienced consistent magnitudes of posterior femoral rollback and external rotation of the femur with weight-bearing flexion. The variation is similar to that previously reported for normal knee where the lateral condyle moves consistently posterior compared to the medial condyle. Subjects experienced low overall mid-flexion paradoxical anterior sliding and no incidence of condylar lift-off leading to mid-flexion stability., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Here, we document a detailed characterisation of two zircon gemstones, GZ7 and GZ8. Both stones had the same mass at 19.2 carats (3.84 g) each; both came from placer deposits in the Ratnapura district, Sri Lanka. The U-Pb data are in both cases concordant within the uncertainties of decay constants and yield weighted mean 206 Pb/ 238 U ages (95% confidence uncertainty) of 530.26 Ma ± 0.05 Ma (GZ7) and 543.92 Ma ± 0.06 Ma (GZ8). Neither GZ7 nor GZ8 have been subjected to any gem enhancement by heating. Structure-related parameters correspond well with the calculated alpha doses of 1.48 × 10 18  g -1 (GZ7) and 2.53 × 10 18  g -1 (GZ8), respectively, and the (U-Th)/He ages of 438 Ma ± 3 Ma (2 s ) for GZ7 and 426 Ma ± 9 Ma (2 s ) for GZ8 are typical of unheated zircon from Sri Lanka. The mean U mass fractions are 680 μg g -1 (GZ7) and 1305 μg g -1 (GZ8). The two zircon samples are proposed as reference materials for SIMS (secondary ion mass spectrometry) U-Pb geochronology. In addition, GZ7 (Ti mass fractions 25.08 μg g -1  ± 0.18 μg g -1 ; 95% confidence uncertainty) may prove useful as reference material for Ti-in-zircon temperature estimates.

Background: We sought to evaluate the outcomes of cementless acetabular components used in patients with Crowe II and III dysplasia, and to compare outcomes between cups placed within vs outside of an "anatomic" zone. Our specific aims were to (1) plot hip centers in these patients at our institution to characterize "anatomic" vs "nonanatomic" positions, (2) evaluate the association between hip center and radiographic loosening, (3) determine whether hip center was associated with acetabular component revision, and (4) compare patient-reported outcome scores between groups., Methods: We retrospectively reviewed 88 primary cementless total hip arthroplasties at a mean follow-up of 10 years (range 2-26 years). Patients were 85% female, with a mean age of 44 years (range 28-61 years) and a body mass index of 27 kg/m 2 (range 19-42 kg/m 2 ). Medical records and radiographs were reviewed, and a survey was conducted for all patients. Anatomic hip center was defined using the 4-zone system, wherein centers are "anatomic" if they are <1 cm superior and <1 cm lateral to the approximate femoral head center. Cox proportional analyses were used to compare outcomes between groups., Results: Seventy hips (80%) had an anatomic hip center. Anatomic hips had a lower incidence of radiographic acetabular loosening (0% vs 17%, P = .007) and cup revision (0% vs 28%, P = .0002). There were no differences in Hip Disability and Osteoarthritis Outcome and Joint Replacement Scores (96.2 ± 5 vs 91.9 ± 12, P = .7)., Conclusion: The incidence of aseptic loosening and cup revision were lower when hip center was <1 cm superior and 1 cm lateral to the approximate femoral head center., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Tibetan ophiolites are shallow mantle material and crustal slabs that were subducted as deep as the mantle transition zone, a conclusion supported by the discovery of high-pressure phases like inverse ringwoodite in these sequences. Ringwoodite, Mg 2 SiO 4 , exhibits the normal spinel structure, with Mg in the octahedral A site and Si in the tetrahedral B site. Through A and B site-disorder, the inverse spinel has four-coordinated A cations and the six-coordinated site hosts a mixture of A and B cations. This process affects the density and impedance contrasts across the boundaries in the transition zone and seismic-wave velocities in this portion of the Earth. We report the first synthesis at high pressure (20 GPa) and high temperature (1600 °C) of a Cr-bearing ringwoodite with a completely inverse-spinel structure. Chemical, structural, and computational analysis confirm the stability of inverse ringwoodite and add further constraints to the subduction history of the Luobusa peridotite of the Tibetan ophiolites.

Gold enrichment at the crustal or mantle source has been proposed as a key ingredient in the production of giant gold deposits and districts. However, the lithospheric-scale processes controlling gold endowment in a given metallogenic province remain unclear. Here we provide the first direct evidence of native gold in the mantle beneath the Deseado Massif in Patagonia that links an enriched mantle source to the occurrence of a large auriferous province in the overlying crust. A precursor stage of mantle refertilisation by plume-derived melts generated a gold-rich mantle source during the Early Jurassic. The interplay of this enriched mantle domain and subduction-related fluids released during the Middle-Late Jurassic resulted in optimal conditions to produce the ore-forming magmas that generated the gold deposits. Our study highlights that refertilisation of the subcontinental lithospheric mantle is a key factor in forming large metallogenic provinces in the Earth's crust, thus providing an alternative view to current crust-related enrichment models.The lithospheric controls on giant gold deposits remain unclear. Here, the authors show evidence for native gold in the mantle from the Deseado Massif in Patagonia demonstrating that refertilisation of the lithospheric mantle is key in forming metallogenic provinces.

Background: Data addressing risk factors predictive of mortality and reoperation after periprosthetic femur fractures (PPFxs) are lacking. This study examined survivorship and risk ratios for mortality and reoperation after surgical treatment for PPFx and associated clinical risk factors., Methods: A retrospective review was performed for 291 patients treated surgically for PPFx between 2004 and 2013. Primary outcomes were death and reoperation., Results: Mortality at 1 year was 13%, whereas the rate of reoperation was 12%. Greater span of fixation and revision arthroplasty (vs open reduction internal fixation) trended toward a lower likelihood of reoperation., Conclusion: After PPFx, patients have a 24% risk of either death or reoperation at 1 year. Factors contributing to increased mortality are nonmodifiable. Risk of reoperation is minimized with greater span of fixation and performance of revision arthroplasty., (Copyright © 2015 Elsevier Inc. All rights reserved.)

To understand the behavior of Li in zircon, we have analyzed the abundance and isotopic composition of Li in three zircon standards (Plešovice, Qinghu and Temora) widely used for microbeam analysis of U-Pb ages and O-Hf isotopes. We have mapped Li concentration ([Li]) on large grains, using a Cameca 1280HR Secondary Ion Mass Spectrometer (SIMS). All zircons have a rim 5-20 μm wide in which [Li] is 5 to 20 times higher than in the core. Up to ~20‰ isotopic fractionation is observed on a small scale in the rims of a single zircon grain. The measured δ(7)Li values range from -14.3 to 3.7‰ for Plešovice, -22.8 to 1.4‰ for Qinghu and -4.7 to 16.1‰ for Temora zircon. The [Li] and δ(7)Li are highly variable at the rims, but relatively homogenous in the cores of the grains. From zircon rim to core, [Li] decreases rapidly, while δ(7)Li increases, suggesting that the large isotopic variation of Li in zircons could be caused by diffusion. Our data demonstrate that homogeneous δ(7)Li in the cores of zircon can retain the original isotopic signatures of the magmas, while the bulk analysis of Li isotopes in mineral separates and in bulk-rock samples may produce misleading data.

Investigations of the Mantle Transition Zone (MTZ; 410-660 km deep) by deformation experiments and geophysical methods suggest that the MTZ has distinct rheological properties, but their exact cause is still unclear due to the lack of natural samples. Here we present the first direct evidence for crystal-plastic deformation by dislocation creep in the MTZ using a chromitite from the Luobusa peridotite (E. Tibet). Chromite grains show exsolution of diopside and SiO2, suggesting previous equilibration in the MTZ. Electron backscattered diffraction (EBSD) analysis reveals that olivine grains co-existing with exsolved phases inside chromite grains and occurring on chromite grain boundaries have a single pronounced crystallographic preferred orientation (CPO). This suggests that olivine preserves the CPO of a high-pressure polymorph (wadsleyite) before the high-pressure polymorph of chromite began to invert and exsolve. Chromite also shows a significant CPO. Thus, the fine-grained high-pressure phases were deformed by dislocation creep in the MTZ. Grain growth in inverted chromite produced an equilibrated microstructure during exhumation to the surface, masking at first sight its MTZ deformation history. These unique observations provide a window into the deep Earth, and constraints for interpreting geophysical signals and their geodynamic implications in a geologically robust context.

The diagnosis of adverse local tissue reaction (ALTR) after metal-on-metal total hip arthroplasty (MoMTHA) presents a significant challenge. No single biomarker is specific for ALTR. The purpose of this study was to determine if the ratio of cobalt to chromium ions is useful for diagnosing ALTR in MoMTHA. In 89 bearing-related revision THAs, preoperative cobalt and chromium ion levels were compared to an intraoperative soft tissue damage grading scale. The average cobalt to chromium ratio was 2.96 (0-20). There was no correlation between the tissue scale and the cobalt to chromium ratio (R=0.095; P=0.41). Many variables affecting ion production/excretion mitigate the use of the ion ratio. The cobalt to chromium ratio is not a predictive biomarker for ALTR in MoMTHA., (Copyright © 2015 Elsevier Inc. All rights reserved.)

We conducted a randomized controlled trial to compare efficacy of an occlusive antimicrobial barrier dressing and a standard surgical dressing in patients who underwent primary total joint arthroplasty. Two hundred sixty-two patients were randomized to receive either an occlusive dressing or a standard dressing. Wounds were closed in identical fashion. Outcomes included wound complications, dressing changes, and patient satisfaction. With use of occlusive dressing (vs standard dressing), wound complications (including skin blistering) were significantly (P = 0.15) reduced; there were significantly (P < .0001) fewer dressing changes; and patient satisfaction was significantly (P < .0001) higher. Use of occlusive dressings can reduce wound complications and promote wound healing after total joint arthroplasty.

The magmatic activity (0-16 Ma) in Iceland is linked to a deep mantle plume that has been active for the past 62 My. Icelandic and northeast Atlantic basalts contain variable proportions of two enriched components, interpreted as recycled oceanic crust supplied by the plume, and subcontinental lithospheric mantle derived from the nearby continental margins. A restricted area in southeast Iceland--and especially the Öræfajökull volcano--is characterized by a unique enriched-mantle component (EM2-like) with elevated (87)Sr/(86)Sr and (207)Pb/(204)Pb. Here, we demonstrate through modeling of Sr-Nd-Pb abundances and isotope ratios that the primitive Öræfajökull melts could have assimilated 2-6% of underlying continental crust before differentiating to more evolved melts. From inversion of gravity anomaly data (crustal thickness), analysis of regional magnetic data, and plate reconstructions, we propose that continental crust beneath southeast Iceland is part of ∼350-km-long and 70-km-wide extension of the Jan Mayen Microcontinent (JMM). The extended JMM was marginal to East Greenland but detached in the Early Eocene (between 52 and 47 Mya); by the Oligocene (27 Mya), all parts of the JMM permanently became part of the Eurasian plate following a westward ridge jump in the direction of the Iceland plume.

Ion levels have been shown to reliably predict abnormal function of the bearing surface with increased wear, but ion levels should not be used alone as a trigger for when to proceed with revision surgery with metal-metal articulations. Risk stratification strategies help determine which patients should be monitored more closely with serial ion levels, cross-sectional imaging with a MARS MRI, or proceed on to revision. Based on the current data available, an ion level greater than 4.5 ppb (Cr or Co) may serve as a threshold for when abnormal wear is occurring, and is suggested as a trigger for a MARS MRI scan., (Copyright © 2014 Elsevier Inc. All rights reserved.)

The purpose of this study was to determine if cobalt and chromium ion levels can predict soft tissue damage at total hip revision. This study included 90 metal-on-metal total hip patients with preoperative cobalt and chromium ion levels. Tissue damage noted at revision surgery was graded on a 4-point scale. Sensitivity, specificity, and predictive values were calculated for various threshold values. Receiver operating characteristic analysis was conducted. Using 7 ppb as a threshold, cobalt and chromium ion levels had poor sensitivity and specificity (Co, 65% and 56%; Cr, 29% and 75%). Positive predictive values for cobalt and chromium were only 48% and 26% respectively. The area under the curve was 0.37 for cobalt and 0.44 for chromium. The length of time to revision significantly correlated with tissue damage (P = .001). Ion levels are unreliable predictors of periarticular soft tissue damage and should not be used in isolation as surgical intervention triggers., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The success of metal bearings is dependent on several parameters. The effects of in vivo forces on the deformation of monoblock acetabular components have yet to be determined. The purpose of our study was to assess the amount of deformation with press-fit fixation of 1-piece metal acetabular components. Four manufacturers provided 1-piece metal acetabular components in each size (30 cups). Testing was conducted using a custom vise to simulate press-fit fixation, and measurements were performed with a Mitutoyo Test device (Aurora, Ill). Previously determined in vivo forces were used in the press-fit simulation. All components deformed under simulated in vivo applied loads. Component deformation ranged from 15 to 300 µm. Larger cups with thinner walls to accommodate larger heads had the greatest deformation and often exceeded the range of reported clearances from the manufacturers (76-227 µm)., (Copyright © 2012 Elsevier Inc. All rights reserved.)

With the demand for total joint arthroplasty and overall life expectancy increasing, there will be an increase in the need for revision arthroplasty surgeries. Given that revision joint surgeries are more demanding for both surgeon and patient with longer operative times, increased blood loss, and multiple patient comorbidities, the current mindset is that older patients who undergo a total hip revision or total knee revision have higher mortality rates than younger patients. We identified 1737 revision total joint patients who were at least 2 years postoperative for inclusion in the study. The overall perioperative mortality rate (defined as deaths occurring between 0 and 3 months following revision joint surgery) was calculated and then stratified by revision knee surgery, revision hip surgery, and age. In addition, mortality rates were compared for patients younger than 70 years, between 70 and 80 years and older than 80 years. The overall perioperative mortality rate after revision total hip or knee surgery was 0.7%. After stratifying by age, the perioperative mortality rate was 0.2% in patients younger than 70 years, 0.8% in patients 70 to 79 years, and 2.63% in patients older than 80 years. Of the 1737 patients, 541 died >1 year following their revision surgery at an average time to death of 6.9 years. The observed perioperative mortality rates following revision total joint surgery at a single center were extremely low among all age groups. Therefore, the age of patients undergoing revision surgery should not be the sole determinant of perioperative survival. Additionally, it appears that the mean postoperative survival noted here seems to justify the additional resources used in revision surgery regardless of age. As limited resources exert pressure on an already overburdened healthcare system, rationing of care for certain procedures may ensue using age as a specific criteria. This study should add clarity to this issue., (Copyright 2010, SLACK Incorporated.)

Background: Despite the clinical success of modern metal-on-metal articulations, concerns with wear-related release of metal ions persist. Evidence suggests metal ion release is related to the effective coverage of the head in the metal shell (the cup's functional articular arc). A recent study suggests a reduced functional articular arc is associated with increased ion release and the arc is a function of component design, size, and the abduction angle., Questions/purposes: The purposes of this study were to (1) measure the functional articular arc in different sizes of currently available one-piece metal shells from several different manufacturers; and (2) compare the functional articular arc of these one-piece metal shells with the 180 masculine arc of conventional hip arthroplasty acetabular components., Methods: We calculated the available articular surface arc for 33 one-piece metal cups using measurements of cup depth and internal cup radius., Results: The arc of the articular surface varied among manufacturers and generally decreased with decreasing shell diameter. The mean functional articular arc was 160.5 degrees +/- 3.6 degrees (range, 151.8 degrees -165.8 degrees), which was less than the 180 degrees arc of a conventional acetabular component., Conclusions: Our data show certain cup designs are at higher risk for failure as a result of the decreased articular surface arc. This, along with analysis of abduction angles, supports the recent findings of bearing failure with vertically placed implants. Care must be taken when implanting these shells to ensure they are placed in less abduction to avoid edge loading and the potential for early bearing failure.

The study purpose was to analyze current results of modern cementless femoral components in young patients having total hip arthroplasty (THA) or hip resurfacing. Twenty-two studies (n = 5907; hips = 6408) evaluating modern cementless THA in young patients and 15 studies evaluating hip resurfacing (n = 3002; hips = 3269) were included. Meta-analysis techniques were used to pool failure rates. The pooled failure rate for THA using femoral revision for mechanical failure as an end point was 1.3% (95% confidence interval [CI], 1.0%-1.7%) at a mean 8.4 years of follow-up. At a mean of 3.9 years of follow-up, the pooled mechanical failure rate of the femoral component for hip resurfacing was 2.6% (95% CI, 2.0-3.4). In conclusion, the enthusiasm for hip resurfacing should be tempered by these data. Longer follow-up and direct comparison trials are required to confirm these findings.

Knee instability is a common cause of prosthetic knee failure. This study sought to determine if synovial fluid analysis is a useful tool in diagnosing prosthetic knee instability. Aspirations were performed in 42 knees in which the diagnosis of instability was in doubt. This group was compared to 120 aspirated knees performed for other diagnoses, excluding infection. The average red blood cell count for the instability group was 79,365 (range, 300-960,000). The median red blood cell count was 9175 (interquartile range, 37,750-2337). In patients with other diagnoses, the average red blood cell count was 60,965 (range, 30-2,079,000). The median red blood cell count was 6200 (interquartile range, 27,525-2512; P=.56). This study confirms that unstable total knees have bloody effusions. The prognostic significance of this finding must be questioned, as patients with other diagnoses have similar findings. Physical examinations and stress radiographs remain the key determinants of prosthetic knee instability.

Unlabelled: Current outcomes data on revision total hip arthroplasty focuses on specific implants and techniques rather than more general outcomes. We therefore examined a large consecutive series of failed THAs undergoing revision to determine if survivorship and modes of failure differ in comparison to the current data. We retrospectively reviewed the medical records of 1100 revision THAs. The minimum followup was 2 years (mean, 6 years; range, 0-20.4 years). Eighty-seven percent of revision total hips required no further surgery; however, 141 hips (13%) underwent a second revision at a mean of 3.7 years (range, 0.025-15.9 years). Seventy percent (98 hips) had a second revision for a diagnosis different from that of their index revision, while 30% (43 hips) had a second revision for the same diagnosis. The most common reasons for failure were instability (49 of 141 hips, 35%), aseptic loosening (42 of 141 hips, 30%), osteolysis and/or wear (17 of 141 hips, 12%), infection (17 of 141 hips, 12%), miscellaneous (13 of 141 hips, 9%), and periprosthetic fracture (three of 141 hips, 2%). Survivorship for revision total hip arthroplasty using second revision as endpoint was 82% at 10 years. Aseptic loosening and instability accounted for 65% of these failures., Level of Evidence: Level IV, therapeutic (retrospective) study. See the Guidelines for Authors for a complete description of levels of evidence.

The purpose of this study was to asses the fate of incomplete seating of press-fit acetabular components. From 1990 to 2002, 587 hip arthroplasties were performed using a single-design acetabular component inserted with a press-fit technique with no additional fixation. Complete radiographic follow-up at a mean 9.2 years was available for 343 cases. One hundred thirty-three acetabular components had incomplete seating on the initial postoperative radiograph and 210 cases had complete seating. Of 133 components, 125 (94%) had evidence of complete zone 2 filling. Zone 2 focal osteolysis was present in 22 patients. There were no intraoperative fractures. No acetabular components were revised for loosening. Incomplete seating of press-fit acetabular components is safe and effective in achieving initial and long-term fixation. Zone 2 lucencies when present initially are not associated with increased failure risks. Vigorous attempts to completely seat the acetabular component appear to be unwarranted.

Infection is an unfortunate complication of total knee arthroplasty. Current literature supports 2-stage reimplantation as the gold standard. Controversy exists whether static or articulating spacers are the best interim treatment method. Seventy-six 2-stage reimplantation procedures met the study inclusion criteria. There were 28 static spacers and 48 articulating spacers. The eradication rate was 94.7% in the articulating group compared with 92.1% in the static group (P = 0.7). There were no significant differences in postoperative Knee Society Scores pain scores. There were 28 (58%) good to excellent function scores in the articulating group and 10 (36%) in the static group (P = .05). Interim use of an articulating spacer maintains excellent infection eradication rates and may improve function over the use of static spacers.

Unlabelled: We compared the incidence of wear-related failures between two large cohorts of patients undergoing total knee arthroplasty implanted with identical modular tibial trays and polyethylene inserts sterilized by different methods. A total of 1183 second-generation press-fit condylar prostheses having inserts packaged and sterilized in an oxygen-free environment were assessed at a minimum 5-year followup (mean, 7.0 years). Wear-related failure was defined as (1) osteolysis greater than 100 mm2 or (2) revision of the implant resulting from osteolysis, polyethylene wear, chronic synovitis, and/or effusion. Wear-related survivorship was calculated using Kaplan-Meier survival analysis. Results were compared with our previously published study of 1287 first-generation press-fit condylar modular knees having inserts sterilized by gamma irradiation in air at 5-year minimum followup (mean, 7.8 years). The wear-related failure rate for the second-generation design was 1.1% and 10-year survivorship was 97.0% compared with 8.3% failure and 87.7% 10-year survival for the first-generation design. For second-generation components, patient age was the only variable correlated with wear-related failure. For first-generation components sterilized in air, several variables were correlated to wear-related failure with shelf age of the polyethylene insert being the most important factor. These data emphasize the dramatic effect improvements in polyethylene manufacturing, specifically sterilization methods, can have on implant survivorship., Level of Evidence: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Unlabelled: Wear and osteolysis have been successfully treated by modular polyethylene exchange in revision hip arthroplasty. However, studies of the same approach in revision knee arthroplasty have not provided similar results. We evaluated the results of isolated polyethylene exchange for wear and/or osteolysis in 68 press-fit condylar TKAs from four centers. At a minimum of 24 months after polyethylene exchange surgery (average, 44 months; range, 24-83 months), there were 11 failures (16.2%). Failures included aseptic loosening in 10 knees and infection in one. With the relatively small cohort size we were unable to identify factors that predicted which knees were more likely to fail: we observed no correlation between failure and patient demographics, component design, or use of cement versus bone graft augmentation. Radiographic review demonstrated no progression of osteolytic lesions in 97% of knees in the study. While the short-term followup limits the conclusions, we believe the 84% success rate with modular polyethylene exchange for wear and osteolysis and the lack of progression of osteolytic lesions in the majority of the knees are encouraging. Full revision of well-fixed total knee components can lead to substantial bone loss, particularly in the face of osteolysis and we therefore consider modular polyethylene exchange in press-fit condylar knees a reasonable option for wear and osteolysis., Level of Evidence: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence

Hip instability is a common postoperative complication after revision surgery. This study sought to define the prevalence of hip instability after 2-stage reimplantation without an articulating spacer. A joint registry review identified 110 patients undergoing 2-stage reimplantation. Fifty-five patients (56 hips) were alive at the time of data collection. Instability was documented and risk factors were analyzed. Of the 56 hips, 14 (25%) dislocated. Five of these 14 patients had chronic abduction insufficiency. Six patients required rerevision to attain stability. There were no significant differences between dislocators and nondislocators in abduction angle, head size, cup size, liner type, or leg length. The 25% (14/56) dislocation rate reported here is unacceptable. Interim articulating spacers, postoperative bracing, large head technology, and constrained liners are treatment methods that should be considered in this group of patients.

The goal of knee arthroplasty is to relieve pain and normalize range of motion while providing stability through the gait cycle. Postoperative, significant (>15 degrees ) flexion contractures can cause persistent pain and altered gait mechanics. This study evaluated the efficacy of revision surgery for painful flexion contractures. Of the 14 patients included in the study, 10 had complete resolution of their flexion contracture. There was significant improvement in extension (P < .0001), flexion (P = .002), and total arc of motion (P < .0001). Knee Society (KSS) pain scores improved significantly (P < .001), whereas KSS function scores did not significantly improve (P = .66). Revision surgery for symptomatic flexion contractures can improve range of motion and diminish pain. The best form of treatment is avoidance through careful flexion and extension gap balancing during primary surgery.

A retrospective review of patients with joint arthroplasty was performed to determine if body mass index has increased with time and if the body mass index of patients with arthroplasty was significantly different than that of the general population. We also sought to determine if reimbursement kept pace with this growing cohort. The number of obese patients increased from 30.4% in 1990 to 52.1% in 2005 (P < .0001). In 2005, 24% of the general population was obese, whereas 52.1% of arthroplasty patients were obese. Physician reimbursement decreased 38% for knee arthroplasty and 46% for hip arthroplasty and the need for total joint arthroplasty because of these confounding variables will increase exponentially beyond scheduled expectations. Patients and health policy forecasters must understand the interrelationship between obesity and the need for arthroplasty.

Acetabular component deformation secondary to forces encountered during insertion is a potential consequence of the press-fit technique. This study characterized the stiffness of Pinnacle 100 cups (DePuy, Warsaw, Ind) via mechanical testing and used this information with intraoperative measurements of cup deformation to calculate the in vivo forces acting on cups inserted during hip arthroplasty in 21 patients. We found that 90.5% of cups had measurable compression deformity, averaging 0.16 +/- 0.16 mm. The corresponding forces acting on these cups averaged 414 +/- 421 N. For hard-on-hard bearing surfaces, such in vivo deformation of acetabular shells may result in negative clinical consequences such as equatorial loading with increased wear and potential seizing of components, chipping of ceramic inserts, or locking mechanism damage.

Unlabelled: We compare the clinical and radiographic results of partial-component versus full-component revision total knee arthroplasty. A retrospective review was used to identify patients who had partial revision total knee arthroplasty. Only isolated femoral or tibial revisions were included. From 1986 to 2000, 448 revision total knee arthroplasties were done. Seventy-seven partial revisions were done. Three were excluded for a diagnosis of infection. The average followup was 63 months. The average Knee Society score for full component revisions was 85 compared with 79 for partial revisions. This difference was significant (p = 0.0001). The average Knee Society score for those patients who had a full revision for instability was 85 compared with 63 for partial revision (p = 0.0001). The average Knee Society score for those patients who had a full revision for wear-related problems was 88 compared with 78 for partial revisions (p = 0.03). Although the advantages of partial revision in hip replacement are well-documented, the efficacy of this treatment strategy has not been established in revision total knee arthroplasty. Care should be taken when considering partial revision for instability or wear-related problems., Level of Evidence: Therapeutic study, Level III (retrospective cohort study). See the Guidelines for Authors for a complete description of levels of evidence.

The appropriate treatment for the young patient with post-collapse avascular necrosis (AVN) of the femoral head continues to be controversial. Femoral surface replacement (FSR) has emerged as a potential strategy to delay total hip arthroplasty in these patients. Between 1997 and 2003, 37 FSR procedures were performed. Success was defined as patients not requiring revision surgery or having a Harris hip pain score of 30 or greater. Failure was defined as patients having revision surgery or a Harris hip pain score of 20 or less. The overall failure rate based on Harris hip pain scores and revision surgery was 64.8% (24/37 procedures). Fifteen (40.5%) procedures required revision surgery, whereas 9 (24.3%) patients were considered failures based on their pain scores. The purpose of this study was to determine if FSR is a viable option for post-collapse AVN. We conclude that hemiresurfacing for AVN is an unpredictable procedure. This procedure is no longer offered as a treatment option for post-collapse AVN at our institution.

This study evaluates the difficult reconstructive challenge of severe proximal femoral bone loss. We present intermediate-term results of 46 hips with extensive proximal femoral bone loss that underwent revision total hip arthroplasty using cementless distal fixation without supplemental allograft. All were evaluated with the Harris hip score at a minimum of 2 years. Radiographs were assessed using the Engh fixation scale. At a mean of 6.4 (range 2-12) years, 43 of the 46 prostheses were functioning well. Two patients required revision for symptomatic loosening, and 1 prosthesis remains radiographically loose with a fair clinical score. Mean Harris hip score was 77 at last follow-up. There were 6 intraoperative femur fractures, 9 dislocations, 10 cases of severe stress shielding, and no infections.

Abyssal peridotites are assumed to represent the mantle residue of mid-ocean-ridge basalts (MORBs). However, the osmium isotopic compositions of abyssal peridotites and MORB do not appear to be in equilibrium, raising questions about the cogenetic relationship between those two reservoirs. However, the cause of this isotopic mismatch is mainly due to a drastic filtering of the data based on the possibility of osmium contamination by sea water. Here we present a detailed study of magmatic sulphides (the main carrier of osmium) in abyssal peridotites and show that the 187Os/188Os ratio of these sulphides is of primary mantle origin and can reach radiogenic values suggesting equilibrium with MORB. Thus, the effect of sea water on the osmium systematics of abyssal peridotites has been overestimated and consequently there is no true osmium isotopic gap between MORBs and abyssal peridotites.

The purpose of this study was to determine the factors influencing wear and osteolysis in patients who have had total knee arthroplasty with the Press-Fit Condylar modular system. Two-thousand ninety-one primary total knee replacements in 1737 patients were done using the Press-Fit Condylar system at three centers. Radiographic and manufacturing data were obtained for 2016 of the 2091 implants (96.4%). For the 1287 of 2016 knees (64%) with more than 5 years of followup, the prevalence of wear-related failure was 8.3%. The 13-year survivorship for all patients was 82.6%. Cox hazards analysis revealed five variables that were correlated with wear-related failure: patient age, patient gender, polyethylene sheet vendor, polyethylene finishing method, and polyethylene shelf age. We were unable to identify one factor as the defining reason for these wear-related failures. The multiple changes in manufacturing methods during the life of this implant may have precluded such a determination. These results may be specific to inserts sterilized in air with gamma irradiation and should not be generalized to current manufacturing techniques. This study emphasizes the potential deleterious effects that small changes in the manufacturing process may have on the outcome of a prosthesis with an initially favorable survivorship.

This study assessed the early morbidity associated with modular component exchange surgery for the treatment of accelerated polyethylene wear and osteolysis in 55 patients. Review of the surgical records revealed no significant intraoperative complications, little intraoperative blood loss (mean 333 mL), no allogenic blood transfusions, and no recorded postoperative deep vein thromboses. Eighteen percent of patients, however, experienced postoperative dislocation. Five patients dislocated multiple times, 3 of which required rerevision surgery. Two patients required rerevision for femoral implant fractures related to osteolysis and 1 additional patient required rerevision due to catastrophic failure of the acetabular component 5 years postoperatively. With an average follow-up of 30 months, 6 of the 55 patients treated with modular exchange required rerevision. The results of this study suggest that instability is the most prevalent early complication associated with modular component exchange. As such, we believe that more stable constructs should be emphasized, possibly at the expense of polyethylene thickness.