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Total knee arthroplasty (TKA) alignment has recently become a hot topic in the orthopedics arthroplasty literature. Coronal plane alignment especially has gained increasing attention since it is considered a cornerstone for improved clinical outcomes. Various alignment techniques have been described, but none proved to be optimal and there is a lack of general consensus on which alignment provides best results. The aim of this narrative review is to describe the different types of coronal alignments in TKA, correctly defining the main principles and terms.

Treatment of complex proximal humeral fractures in the elderly is a challenge and reverse shoulder arthroplasty (RTSA) is now an important alternative to open reduction internal fixation (ORIF) with angular stable plate. The purpose of this study is to compare clinical and radiological outcomes of RTSA and ORIF in the elderly. We retrospectively analyzed patients treated for three- or four-part displaced fractures of the proximal humerus. Range of motion, disabilities of the arm, shoulder and hand (DASH) and Constant scores were recorded. X-ray exam in three projections completed the clinical observation at follow-up. Forty-eight patients were enrolled after a mean follow-up of 37 months: 22 RTSA and 26 ORIF. Mean age at trauma was 74 years. Compared with RTSA patients, ORIF patients had significantly higher mean external rotation (28° vs. 14°) and better results in modal internal rotation (hand at D7 vs. hand at L5-S1). No significant differences were seen in DASH and Constant scores. Avascular necrosis and loss of reduction with varus dislocation of the humeral head were the most frequent causes of revision surgery in ORIF (34.6%) while the revision rate of the RTSA was 9.1%. In this study, both treatments showed good clinical outcomes, but RTSA resulted in lower revision rate than ORIF. Even if external and internal rotation in RTSA patients were worse than ORIF, they did not affect the patient’s quality of life. So, the reverse arthroplasty seems to be a more reliable treatment.

Treatment of complex proximal humeral fractures in the elderly is a challenge and reverse shoulder arthroplasty (RTSA) is now an important alternative to open reduction internal fixation (ORIF) with angular stable plate. The purpose of this study is to compare clinical and radiological outcomes of RTSA and ORIF in the elderly.We retrospectively analyzed patients treated for three- or four-part displaced fractures of the proximal humerus. Range of motion, disabilities of the arm, shoulder and hand (DASH) and Constant scores were recorded. X-ray exam in three projections completed the clinical observation at follow-up.Forty-eight patients were enrolled after a mean follow-up of 37 months: 22 RTSA and 26 ORIF. Mean age at trauma was 74 years. Compared with RTSA patients, ORIF patients had significantly higher mean external rotation (28° vs. 14°) and better results in modal internal rotation (hand at D7 vs. hand at L5-S1). No significant differences were seen in DASH and Constant scores. Avascular necrosis and loss of reduction with varus dislocation of the humeral head were the most frequent causes of revision surgery in ORIF (34.6%) while the revision rate of the RTSA was 9.1%.In this study, both treatments showed good clinical outcomes, but RTSA resulted in lower revision rate than ORIF. Even if external and internal rotation in RTSA patients were worse than ORIF, they did not affect the patient's quality of life. So, the reverse arthroplasty seems to be a more reliable treatment.

Polycrystalline NR3 nickel-based superalloy is a new-generation alloys produced by powder metallurgy for application as turbine disks of a future supersonic airplane. A special heat treatment is used to form a bimodal size distribution of γ′ precipitates. Post mortem transmission electron microscopy is used to observe dislocation structures obtained after creep around 700 °C and 650 MPa, up to 0.2% of plastic deformation. The deformation within a grain is heterogeneous and is principally due to the shearing of both types of precipitates by two different processes which where analysed. The smaller precipitates, called tertiary, are shown to play a major role in the hardening processes. In the proximity of serrated grain boundaries, where perfect dislocations are located, the deformation is higher, which is attributed to an enhanced internal stress in the middle of the grain.

Several aspects on the stacking fault energy (SFE) in short-range ordered -phase model alloys of new nickel based superalloys are discussed. Using transmission electron microscope weak beam observations and computer simulated images of dissociation widths, the SFE was determined as a function of temperature. The values for both alloys are close (31 4m J m −2 for the Re-containing alloy and 28 6m J m − 2 for the Ru-containing alloy). In both cases, the dissociation widths remain quite constant up to 350 °C and a slight decrease is observed at higher temperature. The deformation micromechanisms and the constancy of the SFE up to 750 °C are analysed in connection with short-range order. The deformation at low temperature is characterised by dislocation pile ups, the influence on the dissociation widths of the internal stress due to such configuration is analysed. The calculation reveals a strong effect on the leading dislocation of the pile-up whose dissociation distance can be reduced at most by 50%. © 2002 Elsevier Science B.V. All rights reserved.

Different γ phase model alloys of nickel base superalloys are investigated as a function of temperature using elastic diffuse neutron scattering, macroscopic tensile tests, TEM post mortem observations and in situ straining experiments. Short Range Order (SRO) of (1 1/2 0) type resulting from nano-domains with correlation lengths of 0.5–1 nm is observed in all alloys. The dislocation distribution confirms the presence of short-range ordered nano-domains with a size of about 0.7 nm. In all the alloys, the influence of SRO on the deformation mechanisms is clear at low and medium temperature and thus explains the similarities of the deformation behaviour observed in this temperature range. From 750°C to 1000°C, the deformation microstructure becomes progressively homogeneous which suggests the decrease of SRO as illustrated by a decrease of diffuse scattering intensities at the (1 1/2 0) positions on heating. The various techniques applied prove to be complementary in the investigation of complex solid solutions.

Le but de ce travail est d’etudier l’influence de trois solutes (W, Re et Ru) sur le comportement en traction d’alliages modeles de phase γ de superalliages a base de nickel, et de comparer leurs proprietes a celles de la phase γ du superalliage industriel MC2. Des essais de traction effectues a differentes temperatures ainsi que des observations post mortem realisees dans un M.E.T. font apparaitre des caracteristiques de la deformation similaires. De petites differences apparaissent toutefois selon la nature des solutes. Les raisons physiques controlant l’existence et la disparition des empilements et des paires de dislocations en fonction de la temperature sont discutees.

In-situ deformation experiments were performed on single crystals of the short-range-order-containing γ phase of a nickel-based superalloy. The dislocation pile-ups moving under stress are used as a probe exploring this complex solid solution and giving precise information on the local glide resistance encountered. Their analysis gives access for the first time to several contributions to this glide resistance. The threshold friction stress, which pile-ups must overcome in order to move is equal to the dynamic friction stress, which the pile-up experiences when propagating at a constant velocity. In comparison, the glide resistances deduced from the analysis of relaxed configurations are shown to be significantly underestimated. The softening effect due to the destruction of short-range order is also quantitatively determined.

Both ‘in situ’ experiments and ‘post mortem’ observations have been performed on single crystals from MC2 superalloy γ matrix. Based on the measurement of the dislocation positions within the observed pile ups, a method is proposed that allows the evaluation of friction stresses from the head to the tail of the moving or relaxed pile ups. It appears that friction stresses must be measured on mobile pile ups, when they are deduced from relaxed pile ups they are considerably underestimated.

Short-range order (SRO) in model γ-phases of several Ni-based superalloys is investigated by elastic diffuse neutron scattering as a function of temperature. The composition of the single-crystalline samples has been modified by small amounts of additional elements like Mo, Re, Ru and W in order to study their influence on SRO, which is clearly dominated by peaks of the {1 1/2 0} type. The intensity of SRO scattering remains nearly unchanged up to 600 °C, above this temperature SRO decreases gradually and finally vanishes around 1000 °C. Correlation lengths do not change significantly with temperature.

Several examples of recent studies by in situ straining experiments in a transmission electron microscope performed in the Toulouse group (France) are presented. In particular, quantitative measurements of the features of the dislocation motion are described. These examples deal with individual or collective propagation of dislocations, which are submitted to various types of obstacle. Different metallic materials are investigated: magnesium, intermetallics, aluminium alloys and gamma phase of a superalloy.