Influence of plunge depth on microstructural evolution and mechanical performance of Al/steel friction stir riveted joints

Component-on-component impingement following total hip arthroplasty (THA) can lead to postoperative complications, but its prevalence in nonfailed hips remains unclear due to dynamic factors and limited measurement methodologies. Mechanisms of impingement are mostly thought to be due to component malalignment, such as acetabular cups placed outside of the Lewinnek safe zones, or component sizing, such as the use of large head sizes. However, it is known that early migration of implant components does occur following THA, which may potentially impact postoperative impingement risk. The objective of this study was therefore to evaluate component-on-component impingement risk in patients who have undergone THA over a 5-year postoperative timeline and to evaluate positional impact by comparing impingement risk in the supine and standing positions. There were 24 anterior-approach THA participants who underwent radiostereometric analysis at multiple time points: on the day of surgery, at two weeks, four weeks, six weeks, three months, six months, one year, two years, and five years. Impingement risk was calculated as per a custom computational tool, which measures the closest distance between the femoral stem and the polyethylene liner based on the 3-dimensional poses extracted from radiostereometric analysis. A threshold of one mm was defined to classify impingement, with distances approaching one mm being considered at higher impingement risk. Supine distances remained stable, though standing measurements showed significantly lower mean distances (P < 0.001). Smaller femoral heads (32 mm) had lower distances than larger heads (36 mm; P < 0.0001). Offset stems had significantly greater (P values = 0.016 to 0.046) neck-liner distances. There were no differences observed between collared and collarless stems. Our findings indicate that component-on-component impingement risk remains stable in the supine position, but increases in the standing position, suggesting that functional weight-bearing evaluations are critical for assessing postoperative impingement risk.

Reverse total shoulder arthroplasty (rTSA) lacks an anatomy-based framework for individualized implant planning. We hypothesized that native humeral head size (HHS) could serve as a patient-specific anatomical reference to guide lateralization in rTSA. The purpose of this study was to determine whether HHS predicts the amount of baseplate lateralization required to preserve near-anatomic posterosuperior rotator cuff muscle length, and whether muscle lengths can be reliably estimated in deformed joints using a statistical shape model (SSM). In this computational study, 83 pre-operative computed tomography scans were analyzed using a validated SSM to estimate rotator cuff muscle-tendon lengths. Five rTSA implantation strategies were modeled while controlling implant geometry, ranging from a medialized Grammont-type configuration to lateralized Frankle-type and hybrid strategies. Best-fit humeral head size was correlated with patient-specific lateralization quantified by overlap-based graft thickness and with posterosuperior cuff muscle length. Best-fit humeral head size demonstrated an excellent correlation with graft thickness required for near-anatomic overlap (r = 0.93) and strong correlations with posterosuperior cuff muscle length, particularly the infraspinatus (r = 0.88), as well as the subscapularis (r = 0.76) and teres minor (r = 0.62). Among implantation strategies, the Frankle-type configuration most closely reproduced near-anatomic graft thickness and posterosuperior cuff muscle length. Implantation strategy produced large to very large differences in baseline muscle-tendon length across configurations (Kendall W ≈ 0.9-0.97). The SSM reliably reconstructed muscle-tendon geometry across a broad spectrum of degenerative pathology. HHS predicts the lateralization required to preserve near-anatomic posterosuperior cuff muscle length in rTSA. A Frankle-type lateralization strategy most closely reproduced the overlap-based anatomic reference, while alternative strategies produced systematic deviations in muscle length. These findings support HHS as an anatomy-based, patient-specific guide for lateralization planning. This framework is geometric and conceptual in nature and requires future clinical validation.

Minimum Two-Year Survivorship of Large Femoral Heads with Titanium Sleeves in Primary Total Hip Arthroplasty: An Analysis from the American Joint Replacement Registry.

Ca2+ homeostasis is essential for cellular functions, with regulation by store-operated Ca2+ entry (SOCE) omnipresent. Due to a lower affinity for endoplasmic reticulum (ER)-luminal Ca2+, STIM2 regulates basal cytosolic Ca2+ but also increases interaction and activation of ORAI proteins at ER-plasma membrane junctions after stimulation, whereas STIM1 requires stronger store depletion. In brain, STIM2 is highly expressed in hippocampal neurons. Here, we describe a short STIM2 splice variant, STIM2.3 (also known as STIM2G), that is present only in Old World monkeys, apes and humans, with expression mostly in brain. In contrast to other variants and despite lack of the polybasic domain, expression of STIM2.3 increased SOCE. Structure-function analysis delineated the role of the C-terminal motifs of STIM2 for Ca2+ entry as well as for basal and induced activation of the NFAT transcription factor NFATc1. STIM2.3 displayed reduced interaction with AMPK and with activated AMPK. Neuronal expression of STIM2.3, in comparison to STIM2.2, increased the size of dendritic spine heads, suggesting a specific regulatory role in spine maintenance. Regulated splicing of STIM2.3 in brain might present a rapid mechanism to increase STIM2-mediated effects on gene expression, spine morphology or spontaneous excitability, potentially facilitating an evolutionarily recent expansion of brain complexity.

Whether bigger brains provide enhanced cognitive capacities is a long-lasting and controversial question. While big brains may not be required for producing sophisticated behavior, they could facilitate information processing and memory storage. Here, we report a positive relationship between head size and learning performance in two model bee species, using data from 2,141 individuals. Among honey bees, head size varied by about 30%, and those with larger heads showed higher olfactory learning performance for associative tasks that varied in difficulty. Microcomputed tomography measures indicated that this relationship was linked to brain size variation: The best odor learners had the largest antennal lobes. We made similar observations in bumblebees, suggesting that natural brain size variation is associated with individual cognitive variation in these social bees.

Dislocation remains a common reason for revision after total hip arthroplasty (THA), and adverse spinopelvic mobility is increasingly recognized as a major contributor to instability. Whether its prevalence differs between surgical approaches is unclear. This study compared adverse spinopelvic mobility and associated risk factors in patients who sustained a dislocation after a posterior approach (PA) or a direct anterior approach (DAA), and evaluated whether implant positioning differed between groups. A retrospective analysis was performed on 133 patients with post-operative dislocation and available functional lateral radiographs and low-dose CT scans, including 85 PA and 48 DAA dislocations. Spinopelvic parameters, dynamic pelvic motion between standing, sitting, and supine postures, and established spinopelvic risk factors were assessed. Cup orientation, femoral version, combined anteversion, limb length, and global offset were compared. Spinopelvic morphology was similar, with no significant differences in standing spinopelvic tilt, pelvic incidence, PI-LL mismatch, lumbar lordosis, or lumbar flexion. However, dynamic motion differed markedly. A change in spinopelvic tilt (SPT) of ≥ 20° from standing to seated occurred in 41.3% of DAA dislocations versus 21.1% after PA (p = 0.029). A change in SPT ≤ - 13° from supine to standing occurred in 17.8% after DAA compared with 4.7% after PA (p = 0.048). Other spinopelvic risk factors showed no significant differences. Implant positioning was largely comparable; femoral and combined anteversion, cup inclination, and limb length were similar. Although femoral head size and global offset differed between groups, the association between surgical approach and adverse spinopelvic mobility persisted after accounting for these implant-related factors. Patients dislocating after DAA demonstrated a substantially higher prevalence of adverse spinopelvic mobility despite similar implant orientation and hip restoration. These findings suggest that dynamic pelvic behavior may contribute to anterior instability patterns and highlight the potential relevance of hip-spine assessment in patients undergoing anterior-approach THA. Retrospectively registered, CNIL MR004 2,225,508.

Preoperative 2D digital templating aids surgical planning in total hip arthroplasty (THA). We evaluated template accuracy by comparing preoperative templated measurements with postoperative findings and final implant sizes. We retrospectively reviewed a consecutive series of 100 patients who underwent fluoroscopy-guided direct anterior approach (DAA) THA by a single surgeon from November 2022 to September 2024. All patients received an Emphasys femoral stem with a Pinnacle acetabular cup. A single arthroplasty surgeon used Traumacad™ software for preoperative templating, which was compared to postoperative measurements and implants. Preoperative template averages were: cup size (55.1mm), femur size (5.8), head size (36mm), and inclination (41.0°). Delta values (difference between postoperative and templated measurements) were: neck cut length (5.6mm), neck cut angle (2.8°), LLD (0.1mm), cup size (1.3mm), femur size (0.7), head size (0mm), and inclination (2.9°). Cup size was perfectly predicted in 56% of cases, 95% within two sizes; femur size was perfect in 52% of cases, 88% within one size, and 95% within two sizes. Stem offset was 94% accurate. Regression analysis found that higher BMI and male gender were associated with less accurate predictions for neck angle and cup size, respectively. While variables such as higher BMI and male gender may influence the accuracy of templating, our findings suggest that 2D templating for DAA THA offers reliable predictions within a narrow range for final implant sizes, neck cut, and planned leg length changes.

Primary Total Hip Arthroplasty in Patients Who Have Morbid Obesity: A Propensity-Weighted Analysis of Dual Mobility and Standard Fixed-Bearing Implants.

Registry and industry data show increasing utilization of large (36 mm) heads in primary total hip arthroplasty (THA). Recent analysis of the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR) has reported reduced dislocation rates with 36 mm heads compared to 32- and 28-mm heads; however, the effect of age, fixation, approach, cup size, and bearing surface upon revision risk and head size has not been examined, with little data on all-cause revision. The AOANJRR data were examined for all ceramic and metal head THA with highly crosslinked polyethylene between September 1999 and December 2022. There were 272,258 THAs identified. Cumulative percent revision (CPR) following THA was examined with further subanalysis of age, fixation, approach, cup size, and bearing surface for 32- and 36-mm heads. The CPR was higher for 36 mm heads from 1 month (HR [hazard ratio] 1.14 (1.08 to 1.20), P < 0.001). Subgroup analysis showed these differences varied depending on age, sex, approach, cup size, and bearing surface. There were differences in reasons for revision between head sizes, with significantly more revisions with 36 mm heads for fracture (HR 1.30 (1.18 to 1.42), P < 0.001), particularly for ≥ 65-year-olds, and loosening (HR 1.21 (1.09 to 1.34, P < 0.001), and significantly more revisions for dislocation (to a lesser degree) with 32 mm heads (HR 1.18 (1.07 to 1.30), P < 0.001). Our study shows an association between larger head size and increased CPR. This difference is most clearly seen in metal-on-highly crosslinked polyethylene articulations, anterior approach, and 54- to 55-mm cup size in men < 65 years, although it still exists to a lesser extent in men ≥ 65 years. For women, the pattern was similar, although not as apparent. Comparing 36- to 32-mm heads, 36 mm showed reduced early dislocation; however, revision for fracture and loosening was increased. With an increasing trend toward larger head sizes both in the AOANJRR and elsewhere, consideration must be given in these particular subgroups as to whether larger head size confers the intended survival advantages.

The cartilage hair hypoplasia-anauxetic dysplasia (CHH-AD) spectrum represents a group of rare autosomal recessive skeletal dysplasias with significant phenotypic heterogeneity. These disorders are classified based on pathogenic variants in the RMRP, POP1, and NEPRO genes. Among these, anauxetic dysplasia type 3 (ANXD3), associated with NEPRO variants, manifests as severe skeletal dysplasia characterized by short stature, brachydactyly, skin laxity, and joint hypermobility, with distinct radiographic findings such as ovoid vertebrae, hypoplastic ilia, narrow acetabular angles, and irregular metaphyses. Unlike other CHH-AD subtypes, ANXD3 lacks immunological or gastrointestinal involvement. This study reports three new ANXD3 cases from a consanguineous Iranian family, carrying the homozygous pathogenic variant Chr3:113014014G>A; exon3; c.280C>T; p.Arg94Cys in the NEPRO gene. The clinical phenotypes expand the known spectrum of ANXD3, including unique features such as microcephaly, clubfoot, cataracts, urolithiasis, and hearing impairments, whi12-18ch suggest systemic involvement beyond skeletal abnormalities. Diagnostic whole-exome sequencing, supported by Sanger validation, confirmed the autosomal recessive inheritance pattern. A comparative analysis with previously reported ANXD3 cases revealed shared characteristics, including short stature, brachydactyly, and thoracolumbar kyphoscoliosis, while highlighting variability in head size, scalp hair, and systemic features. Microcephaly was observed in our patients, same as previously reported cases, underscoring the phenotypic variability of ANXD3. This study also emphasizes the importance of genetic counseling and early interventions for associated complications, such as orthopedic, renal, and ophthalmological management.

The impact of subject weight and activity level on over-inserted cemented acetabular cups after Total HIP Arthroplasty (THA).

In Vivo Wear Analysis of Third- versus Second-Generation Moderately Crosslinked Polyethylene Liners in Total Hip Arthroplasty.

Macrocephaly, defined as a large head size, has a very broad differential and sometimes can be challenging to differentiate as benign versus indicative of pathology. In this review, we outline a stepwise approach to improving diagnosis of neurogenetic disorders versus other causes using the example of PTEN (phosphatase and TENsin homolog) Hamartoma Tumor Syndrome (PHTS). PHTS is a multiple hamartoma syndrome with medical management implications including the need for tumor surveillance, but often cases are not diagnosed until later in adulthood. Our review emphasizes the utility of using head circumference z scores in combination with other features as a triage tool for genetic identification of disorders such as PHTS.

Abstract Background Over 60 000 metal-on-metal (MoM) hip implants have been implanted in the UK. Since 2017, MHRA guidelines have mandated broad surveillance, classifying any risk factor as high risk. This approach places major demands on services and risks over-surveillance. We aimed to develop a risk-adapted, three-tier pathway to safely reduce unnecessary follow-up. Methods We analysed 845 patients with MoM hip resurfacing and large-head total hip arthroplasty. The primary outcome was abnormal MRI or revision. Logistic regression identified independent predictors, translated into a clinical risk score, and ranked by each predictor relative contribution. Kaplan–Meier survival and interval-specific revision rates guided long-term risk estimates and follow-up intervals. Results Tier-1 predictors (adjusted OR) were female sex (2.0), bilateral (1.7) GFR &amp;lt; 60 (1.6), age &amp;lt; 50y (1.4), head size &amp;lt; 48 mm (1.2), and high-risk implant (1.2). Tier-2 predictors were abnormal X-ray (9.6), pain (2.8), abnormal metal-ion level (2.6), and other symptoms (1.4). The hierarchical model achieved sensitivity 0.69, specificity 0.73, and AUROC 0.71 at the Youden threshold. The MHRA approach had sensitivity 0.85, specificity 0.33, and AUROC 0.68. At 20 years, survival was 91.2% overall, 86.8% in high-risk, and 92.7% in low-risk groups. Beyond 10 years, cumulative revision risk was higher in high-risk patients (9.4 versus 4.1%); notably, 73.9% of late revisions in the low-risk group were symptomatic. Conclusions We propose a three-tier pathway: (1) baseline stratification; (2) surveillance of high-risk patients every 3 years with symptoms, radiographs, and optional metal ions; (3) MRI for Tier-2 abnormalities. Low-risk patients have limited benefits from follow-up beyond 10 years unless symptomatic.

Understanding how ageing affects brain function remains a central challenge in neuroscience. Electrophysiological brain imaging techniques provide a near-direct measure of neuronal activity, which is useful for characterising neurophysiological health. They offer us the ability to track large-scale networks of functional activity with high temporal precision. The effects of healthy ageing on these networks remain poorly understood, in part due to small sample sizes and limited control for confounding factors in previous studies. Here, we analysed resting-state source-reconstructed magnetoencephalography (MEG) data from a large cross-sectional cohort of healthy adults ( = 612, 18-88 years old) to characterise the effect of age using not only time-averaged (static), but also transient (dynamic) network activity. We examined time-averaged power and coherence across canonical frequency bands ( , , , , ), as well as transient network dynamics identified using Hidden Markov Modelling. We included many confounding variables known to be affected by age, such as brain volume, as well as head size and position, which have previously been overlooked. Ageing was associated with frequency-specific changes in oscillatory power, with decreases in low-frequency ( , ) power and increases in high-frequency ( ) power. Coherence increased across all frequency bands and was positively associated with cognitive performance. Transient network analyses additionally revealed that frontal network occurrences declined with age, with evidence suggesting a compensatory role in supporting cognition. These findings provide a more comprehensive electrophysiological signature for healthy ageing and establish a baseline for detecting pathological change.

Very preterm infants born before 32 weeks of gestation remain vulnerable to postnatal growth impairment. However, longitudinal data focusing on appropriate-for-gestational-age (AGA) infants are limited. Standard growth references may inadequately reflect the developmental trajectories of this population. We constructed sex-specific growth curves for height, weight, body mass index, and head circumference from term-equivalent age to 6 years postmenstrual age in AGA infants born at <32 weeks of gestation without neurodevelopmental impairments. These trajectories were compared with Japanese national growth standards. Infants born before 28 weeks of gestation demonstrated significantly reduced growth relative to national standards, with the greatest deviation occurring between 40 and 60 weeks postmenstrual age. While gradual catch-up growth was observed thereafter, full alignment with standard curves was not achieved. Lower gestational age correlated with more pronounced deficits across all anthropometric parameters. Head circumference remained notably reduced among infants born before 25 weeks, raising concern for potential neurodevelopmental implications. Extremely preterm AGA infants experience persistent growth deficits through early childhood. These findings underscore the importance of long-term growth surveillance and early intervention strategies to support optimal physical and neurological outcomes in this high-risk population. Many extremely preterm infants grow more slowly than expected well into early childhood. Babies born earlier in pregnancy show more delayed physical growth across all measures. Infants born before 25 weeks may have a smaller head size, raising concerns for brain development.

In the early days of artificial joint replacement, the choice of bearing material was a decisive factor for the long-term success of an artificial joint. Through intensive research and development over more than three decades, the materials and their processing and sterilisation have been continuously improved. The materials used today all offer a high degree of safety and durability. As a result - In combination with the strict approval guidelines - the choice of a specific material is no longer as important as it was when artificial joint replacement was first introduced.This article focuses on the results of primary hip arthroplasty in eight established registries. In all of the registries examined, ceramic-ceramic bearings and bearings with cross-linked polyethylene cups or liners in combination with heads made of all common head materials, show very good long-term results with a low revision risk. The choice of head size varies considerably in the individual registries. In America, large (36 mm diameter) or very large ceramic heads (over 36 mm) tend to be used, even though the country's own registry warns against very large heads. In Australia, also mainly large heads are used. However, recent analyses indicate that large heads (36 mm) have a higher risk of revision in the long term. In Scandinavian countries, the Netherlands, and New Zealand, smaller heads (32 mm diameter) tend to be predominantly used. The situation in the other countries whose registries were analysed lies somewhere in between, with each country having its own special features. In England, the results of surface replacement are being closely monitored. The results are inconspicuous for the recommended patient population. The further performance of the newly introduced ceramic surface replacement is being followed with great interest. In Germany, the proportion of heads with a diameter of 36 mm is growing continuously, which should be critically questioned when considering the results from Australia. Ceramic-ceramic bearings are being used less and less frequently, even though they perform similarly well overall to hard-soft bearings and even better in some settings. Switzerland is the only country where this bearing still accounts for more than 10 % of treatments. Sweden no longer differentiates between materials in its annual report, but instead provides a ranking of the 74 Swedish clinics in terms of revision risk. In the Netherlands, the 32 mm head diameter is still the most frequently chosen. The German registry has the highest granularity of all registries. The use of dual mobility systems in primary endoprosthetics varies greatly between registries.Despite the differences in head materials and diameters, the results for hip replacements using HXLPE or ceramic cup inlays, show a comparable overall survival rate of approximately 96 % to 98 % after 5 years. What is noteworthy is the approach taken by the Swedish mother of all endoprosthesis registries, which no longer reports results for the different bearing combinations or head sizes, but instead reports the individual results for each facility. The overall good results for all currently used bearing materials in combination with appropriate patient selection make this a comprehensible step. Consequently, the respective clinical care quality is becoming increasingly important.

Dislocation is a common complication after total hip arthroplasty (THA). Previously, we found that different liner models provided varying degrees of articulating head coverage. Jumping distance (JD) is a key indicator of joint stability. Therefore, we aimed to investigate the differences in JD values among various liner models. JD values were determined using previously published articulating head coverage data for 25 modular polyethylene liners used in 6 uncemented cup designs from 4 major manufacturers using a mathematical model. For each liner, the average values corresponding to each femoral head size within each cup size were used in the analysis. Within the safe zone (5–25° anteversion and 30–50° inclination), average JD values ranged from 10.79 to 17.29 mm, depending on cup positioning, liner design, and femoral head size. On average, enlarging the femoral head size from 28 to 36 mm resulted in a 3.53 mm increase in JD within the safe zone. The JD variation between different liner designs was of the same magnitude as the effect of increasing the femoral head size from 28 to 36 mm: 3.16 mm with 32 mm and 3.32 mm with 36 mm femoral heads. The JD of the liner with the lowest coverage combined with a 36 mm femoral head was lower than that of the liner providing the greatest coverage, even when coupled with a 28 mm femoral head. Liner design can influence JD to a degree comparable to increasing femoral head size from 28 to 36 mm. Among the evaluated designs, liners providing greater coverage, such as the X3, yielded higher JD values for the same femoral head size. As optimal joint stability cannot be ensured solely by selecting a larger head size, liner geometry should be carefully considered alongside head size in THA component selection.

The aim of this work was to investigate the effect of an air layer of different thicknesses on the design of high-permittivity materials (HPM) helmets for ultrahigh field (UHF) magnetic resonance imaging (MRI). We used a recently proposed analytical formulation of scattering from layered spheres to model an MRI experiment with a variable air layer between a homogenous human head and an HPM helmet. Such model expresses the fields as a superposition of progressive and regressive traveling waves by exploiting the theory of inhomogeneous transmission. Analytical results were compared with numerical simulations, in terms of changes in the radiofrequency (RF) magnetic induction field employing a surface and volume coil, to validate the proposed method. The presence of an air layer, due to differences in head size, results in a slight variation in the optimal permittivity value required to optimize the performance of the helmet, with a maximum relative variation of no more than 12%. This can be explained by the invariance of the impedance at the outer air-HPM interface, due to the high conductivity typical of biological tissues. In both cases, a clear increase in the magnetic induction field is observed, suggesting that the HPM design is robust to the introduction of a small dielectric insulating layer. Also, good agreement was found between the analytical and numerical results suggesting that the model could be employed to optimize the HPM also in real experiments, particularly when canonical geometries, such as cylindrical or spherical shapes, are employed to design the helmet.