Identifying The Pattern of Material Loss at the Head-Neck Junction Wear Helps Determine the Mechanism of Failure of Metal on Metal Total Hip Replacements

Material loss at the Head-Neck junction accounts for a third of the total volume material loss in contemporary metal-on-metal total hip replacements. It is speculated that the material loss is the result of corrosion and mechanical wear (fretting). High volumes of material loss have been reported, especially from the head taper. There is only one report on characterizing the pattern of material loss and this was in a very small number of cases (n=5). Our aim was to identify the different material loss patterns at the head taper and their corresponding mechanisms We retrospectively analysed a series of retrieved Large Head Metal on Metal Total Hip Replacements (155 cups, 155 femoral heads and 4 stems). We measured material loss on the bearing surfaces and the head-neck junction using well-published metrology methods. Furthermore we collected patient (age, gender and time of primary/revision operations), pre-revision (cobalt and chromium blood metal ion, oxford hip score, cup orientation and implant position) implant (cup and head size, manufacturer and corrosion severity) data. Finally we used surface analysis techniques (microscopy and spectroscopy) to identify fretting, imprinting and the material composition of debris. We devised a novel four-group classification and two blinded engineers classified the material loss patterns using wear maps derived from the metrology analysis We observed four distinct patterns of taper surface material loss at our retrieval centre and we set out to characterize these types and relate them to patient, implant and clinical variables. The four groups of material loss patterns were defined as: (1) Low wear (n= 63), (2) Open-end band (n=32), (3) Stripped material loss (n=54) and (4) Coup-Countercoup (n=6) (Figure). The Interobserver Reliability Kappa score was 0.78 (p<0.001) indicating substantial agreement between the two examiners. Analysis of variables between the groups identified significantly different head sizes (highest: Group 2, p=0.000), corrosion severity (highest: Group 2, p=0.004) and time to revision (highest: Group 3, p=0.040). We identified four different material loss patterns each with its own mechanism. Corrosion was identified as the principal mechanism in Groups 1 and 3. Group 1 head-neck junctions are thought to have a better seal with less fluid ingress in the junction. Group 3 head-neck junctions are attacked by corrosion either circumferentially, or unilaterally, along the whole engagement length. Mechanically assisted corrosion was the principal mechanism in Group 2. The higher friction torque opens up the open-end part of the junction and the ingressing fluid accelerates the corrosion. Extensive fretting was also observed under the scanning electron microscope. Intra-operative surgical damage was identified as the principal mechanism in Group 4, with only 6 components. The patterns and the mechanisms of material loss at the head-neck junction contribute to the understanding of large head metal-on-metal hip replacements. As a result, better implants can be designed in the future. Clinically, these findings suggest that head size and head taper-trunnion fit are the main factors that determine the longevity of the head-neck junction. On the other hand, patients selection does not influence the integrity of the junction

Charactering taper junction wear helps understand the mechanism of failure of metal on metal hip replacements.

Introduction: Taper junction material loss is the result of corrosion and mechanical wear. The significance of the taper junction material loss is highlighted by studies that compared resurfacing and total hip replacements of the same type and size. High volumes of material loss are reported, especially from the head taper, but the pattern of wear is unknown. One report characterized the material loss pattern of five tapers (n=5) into axisymmetrical and asymmetrical, along the long axis of the taper. We noticed more than two patterns on our retrievals and we set out to characterize these types and relate them to clinical variables. Methods: We retrospectively analysed retrieved cobalt-chromium tapers (n=146) using a roundness measurement machine. We also performed a corrosion classification and collected clinical data (metal ion levels, time to revision, component sizes). A non-blinded author devised a four-group classification (table). Two blinded authors classified the material loss patterns derived from the roundness measurement machine. Results: The four groups of material loss patterns Low wear (n= 62), Open-end band (n=29), Stripped material loss (n=51) and Coup-Countercoup (n=4). Kappa was 0.78 (p<0.001) in the assessment of interobserver reliability. Kruskal-Wallis test revealed: - Significantly higher volumes of wear on the taper of Stripped material loss compared to Low wear (p<0.001) and Open-end band compared to Low wear (p<0.001) groups. - Significantly higher chromium ion blood levels in the open-end band compared to the Stripped material loss group. - Significantly higher Cobalt ion blood levels in the Stripped material loss compared to the Low wear group - Significantly higher Cobalt/Chromium ration in the Open-end band compared to the Low wear group One-way ANOVA analysis revealed: - Significant difference between in the head sizes between the groups (p=0.01). Post-hoc analysis located the difference between the Low wear (median=40, range=20) and Open-end band (median=49, range=20) groups (p<0.001). - Significantly higher time to revision in the Stripped material loss compared to the Low wear group (p=0.05), in the post-hoc analysis. - Significantly higher corrosion scores in the Stripped material loss compared to the Low wear group (p<0.001) and the Open-end band compared to the Low wear group (p<0.001). Discussion: The results suggests that corrosion becomes worse over time and that the material loss pattern evolves gradually from the Low wear to Open-end band and finally to Stripped. Further analysis is required to assess the factors that affect the Coup-countercoup group

Damage patterns at the head-stem taper junction helps understand the mechanisms of material loss

Background: Material loss at the taper junction of metal-on-metal total hip replacements (MOM THRs) has been implicated in their early failure. The mechanisms of material loss are not fully understood; analysis of the patterns of damage at the taper can help us better understand why material loss occurs at this junction. Methods: We mapped the patterns of material loss in a series of 155 MOM-THRs received at our centre by scanning the taper surface using a roundness-measuring machine. We examined these material loss maps to develop a five-tier classification system based on visual differences between different patterns. We correlated these patterns to surgical, implant and patient factors known to be important for head-stem taper damage. Results: We found that 63 implants had ‘minimal damage’ at the taper (material loss <1mm3 ) and the remaining 92 implants could be categorised by four distinct patterns of taper material loss. We found that (1) head diameter and (2) time to revision were key significant variables separating the groups. Conclusion: These material loss maps allow us to suggest different mechanisms that dominate the cause of the material loss in each pattern: (a) corrosion, (b) mechanically assisted corrosion or (c) intra-operative damage or poor size tolerances leading to toggling of trunnion in taper

Segmentectomy versus lobectomy. Which factors are decisive for an optimal oncological outcome?

Low-dose computed tomography is being used for lung cancer screening in high-risk groups. Detecting lung cancer at an early stage improves the chance of optimal treatment and increases overall survival. This article compares segmentectomy vs. lobectomy as surgical options, in the case of stage I non-small cell lung carcinoma, ideally IA. To compare the 2 previously referred strategies, data were collected from articles (40 studies were reviewed), reviews, and systematic analyses in PubMed Central, as well as reviewing recent literature. Segmentectomy could be an equal alternative to lobectomy in early-stage NSCLC (tumour < 2 cm). It could be preferred for patients with a low cardiopulmonary reserve, who struggle to survive a lobectomy. As far as early-stage NSCLC is concerned, anatomic segmentectomy is an acceptable procedure in a selective group of patients. For better tumour and stage classification, a systematic lymph node dissection should be performed

The geodynamic and limnological evolution of Balkan Lake Ohrid, possibly the oldest extant lake in Europe

Studies of the upper 447 m of the DEEP site sediment succession from central Lake Ohrid, Balkan Peninsula, North Macedonia and Albania provided important insights into the regional climate history and evolutionary dynamics since permanent lacustrine conditions established at 1.36 million years ago (Ma). This paper focuses on the entire 584-m-long DEEP sediment succession and a comparison to a 197-m-long sediment succession from the Pestani site ~5 km to the east in the lake, where drilling ended close to the bedrock, to unravel the earliest history of Lake Ohrid and its basin development. 26Al/10Be dating of clasts from the base of the DEEP sediment succession implies that the sedimentation in the modern basin started at c. 2 Ma. Geophysical, sedimentological and micropalaeontological data allow for chronological information to be transposed from the DEEP to the Pestani succession. Fluvial conditions, slack water conditions, peat formation and/or complete desiccation prevailed at the DEEP and Pestani sites until 1.36 and 1.21 Ma, respectively, before a larger lake extended over both sites. Activation of karst aquifers to the east probably by tectonic activity and a potential existence of neighbouring Lake Prespa supported filling of Lake Ohrid. The lake deepened gradually, with a relatively constant vertical displacement rate of ~0.2 mm a−1 between the central and the eastern lateral basin and with greater water depth presumably during interglacial periods. Although the dynamic environment characterized by local processes and the fragmentary chronology of the basal sediment successions from both sites hamper palaeoclimatic significance prior to the existence of a larger lake, the new data provide an unprecedented and detailed picture of the geodynamic evolution of the basin and lake that is Europe’s presumed oldest extant freshwater lake

Modulation of the vertical particle transfer efficiency in the oxygen minimum zone off Peru

The fate of the organic matter (OM) produced by marine life controls the major biogeochemical cycles of the Earth's system. The OM produced through photosynthesis is either preserved, exported towards sediments or degraded through remineralisation in the water column. The productive eastern boundary upwelling systems (EBUSs) associated with oxygen minimum zones (OMZs) would be expected to foster OM preservation due to low O2 conditions. But their intense and diverse microbial activity should enhance OM degradation. To investigate this contradiction, sediment traps were deployed near the oxycline and in the OMZ core on an instrumented moored line off Peru. Data provided high-temporal-resolution O2 series characterising two seasonal steady states at the upper trap: suboxic ([O2]  50%) and remineralisation (intermediate Teff 20  50%) has been reported in summer and winter associated with extreme limitation in O2 concentrations or OM quantity for OM degradation. However, higher levels of O2 or OM, or less refractory OM, at the oxycline, even in a co-limitation context, can decrease the OMZ transfer efficiency to below 50%. This is especially true in summer during intraseasonal wind-driven oxygenation events. In late winter and early spring, high oxygenation conditions together with high fluxes of sinking particles trigger a shutdown of the OMZ transfer (Teff < 6%). Transfer efficiency of chemical elements composing the majority of the flux (nitrogen, phosphorus, silica, calcium carbonate) follows the same trend as for carbon, with the lowest transfer level being in late winter and early spring. Regarding particulate isotopes, vertical transfer of δ15N suggests a complex pattern of 15N impoverishment or enrichment according to Teff modulation. This sensitivity of OM to O2 fluctuations and particle concentration calls for further investigation into OM and O2-driven remineralisation processes. This should include consideration of the intermittent behaviour of OMZ towards OM demonstrated in past studies and climate projections

Cavernous Malformations of the Central Nervous System: An International Consensus Statement

Introduction: Cavernous malformations (CM) of the central nervous system constitute rare vascular lesions. They are usually asymptomatic, which has allowed their management to become quite debatable. Even when they become symptomatic their optimal mode and timing of treatment remains controversial. Research question: A consensus may navigate neurosurgeons through the decision-making process of selecting the optimal treatment for asymptomatic and symptomatic CMs. Material and methods: A 17-item questionnaire was developed to address controversial issues in relation to aspects of the treatment, surgical planning, optimal surgical strategy for specific age groups, the role of stereotactic radiosurgery, as well as a follow-up pattern. Consequently, a three-stage Delphi process was ran through 19 invited experts with the goal of reaching a consensus. The agreement rate for reaching a consensus was set at 70%. Results: A consensus for surgical intervention was reached on the importance of the patient’s age, symptomatology, and hemorrhagic recurrence; and the CM’s location and size. The employment of advanced MRI techniques is considered of value for surgical planning. Observation for asymptomatic eloquent or deep-seated CMs represents the commonest practice among our panel. Surgical resection is considered when a deep-seated CM becomes symptomatic or after a second bleeding episode. Asymptomatic, image-proven hemorrhages constituted no indication for surgical resection for our panelists. Consensus was also reached on not resecting any developmental venous anomalies, and on resecting the associated hemosiderin rim only in epilepsy cases. Discussion and conclusion: Our Delphi consensus provides an expert common practice for specific controversial issues of CM patient management

The geodynamic and limnological evolution of Balkan Lake Ohrid, possibly the oldest extant lake in Europe

Studies of the upper 447 m of the DEEP site sediment succession from central Lake Ohrid, Balkan Peninsula, North Macedonia and Albania provided important insights into the regional climate history and evolutionary dynamics since permanent lacustrine conditions established at 1.36 million years ago (Ma). This paper focuses on the entire 584-m-long DEEP sediment succession and a comparison to a 197-m-long sediment succession from the Pestani site ~5 km to the east in the lake, where drilling ended close to the bedrock, to unravel the earliest history of Lake Ohrid and its basin development. 26Al/10Be dating of clasts from the base of the DEEP sediment succession implies that the sedimentation in the modern basin started at c. 2 Ma. Geophysical, sedimentological and micropalaeontological data allow for chronological information to be transposed from the DEEP to the Pestani succession. Fluvial conditions, slack water conditions, peat formation and/or complete desiccation prevailed at the DEEP and Pestani sites until 1.36 and 1.21 Ma, respectively, before a larger lake extended over both sites. Activation of karst aquifers to the east probably by tectonic activity and a potential existence of neighbouring Lake Prespa supported filling of Lake Ohrid. The lake deepened gradually, with a relatively constant vertical displacement rate of ~0.2 mm a−1 between the central and the eastern lateral basin and with greater water depth presumably during interglacial periods. Although the dynamic environment characterized by local processes and the fragmentary chronology of the basal sediment successions from both sites hamper palaeoclimatic significance prior to the existence of a larger lake, the new data provide an unprecedented and detailed picture of the geodynamic evolution of the basin and lake that is Europe’s presumed oldest extant freshwater lake

Mediterranean winter rainfall in phase with African monsoons during the past 1.36 million years

Mediterranean climates are characterized by strong seasonal contrasts between dry summers and wet winters. Changes in winter rainfall are critical for regional socioeconomic development, but are difficult to simulate accurately1 and reconstruct on Quaternary timescales. This is partly because regional hydroclimate records that cover multiple glacial–interglacial cycles2,3 with different orbital geometries, global ice volume and atmospheric greenhouse gas concentrations are scarce. Moreover, the underlying mechanisms of change and their persistence remain unexplored. Here we show that, over the past 1.36 million years, wet winters in the northcentral Mediterranean tend to occur with high contrasts in local, seasonal insolation and a vigorous African summer monsoon. Our proxy time series from Lake Ohrid on the Balkan Peninsula, together with a 784,000-year transient climate model hindcast, suggest that increased sea surface temperatures amplify local cyclone development and refuel North Atlantic low-pressure systems that enter the Mediterranean during phases of low continental ice volume and high concentrations of atmospheric greenhouse gases. A comparison with modern reanalysis data shows that current drivers of the amount of rainfall in the Mediterranean share some similarities to those that drive the reconstructed increases in precipitation. Our data cover multiple insolation maxima and are therefore an important benchmark for testing climate model performance