High risk of elevated metal concentrations with 9/10-mm stem trunnions and highly cross-linked polyethylene grafted with poly(2-methacryloyloxyethyl phosphorylcholine) in total hip arthroplasty

Background: The risks of metal release due to fretting and corrosion at the head–neck junction and consequent adverse local tissue reaction (ALTR) have concerns in metal-on-polyethylene (MoP) total hip arthroplasty (THA). Although trunnions have become thinner in diameter to increase the range of motion, it has remained unclear whether this change affects metal release and ALTR in vivo. This study aimed to investigate serum metal concentrations and the prevalence of ALTR in MoP THA with a 9/10-mm stem trunnion.Patients and methods: A consecutive series of 37 hips that underwent THA using MoP grafted with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) with a 9/10-mm trunnion stem were retrospectively reviewed. Serum metal levels were assessed and compared with those in MoP THA with a 10/12-mm trunnion stem. ALTR was diagnosed with serum metal levels and cross-sectional images. The factors associated with serum metal levels were also assessed.Results: The median serum cobalt and chromium levels were 1.5 μg/L and 1.0 μg/L in the 9/10-mm group and 0.2 μg/L and 0.4 μg/L in the 10/12-mm group, respectively. ALTR was found in 5 hips of 3 patients. Revision surgery was performed in 4 hips, and all stem trunnions and femoral heads showed severe corrosion. Postoperative walking ability was associated with serum metal levels.Conclusion: It was found that a 9/10-mm stem trunnion with MoP grafted with PMPC had high risks of metal release in primary THA. Careful follow-up and cross-sectional imaging are needed to detect ALTR for early revision

Inhibition of bone erosion, determined by high-resolution peripheral quantitative computed tomography (HR-pQCT), in rheumatoid arthritis patients receiving a conventional synthetic disease-modifying anti-rheumatic drug (csDMARD) plus denosumab vs csDMARD therapy alone: an open-label, randomized, parallel-group study

Background: This exploratory study compared the inhibition of bone erosion progression in rheumatoid arthritis (RA) patients treated with a conventional synthetic disease-modifying anti-rheumatic drug (csDMARD) plus denosumab versus csDMARD therapy alone and investigated the effects of denosumab on bone micro-architecture and other bone-related parameters using high-resolution peripheral quantitative computed tomography (HR-pQCT).Methods: In this open-label, randomized, parallel-group study, patients with RA undergoing treatment with a csDMARD were randomly assigned (1:1) to continue csDMARD therapy alone or to continue csDMARDs with denosumab (60-mg subcutaneous injection once every 6 months) for 12 months. The primary endpoint was the change from baseline in the depth of bone erosion, measured by HR-pQCT, in the second and third metacarpal heads at 6 months after starting treatment. Exploratory endpoints were also evaluated, and adverse events (AEs) were monitored for safety.Results: In total, 46 patients were enrolled, and 43 were included in the full analysis set (csDMARDs plus denosumab, N = 21; csDMARD therapy alone, N = 22). Most patients were female (88.4%), and the mean age was 65.3 years. The adjusted mean (95% confidence interval) change from baseline in the depth of bone erosion, measured by HR-pQCT, in the 2–3 metacarpal heads at 6 months was − 0.57 mm (− 1.52, 0.39 mm) in the csDMARDs plus denosumab group vs − 0.22 mm (− 0.97, 0.53 mm) in the csDMARD therapy alone group (between-group difference: − 0.35 mm [− 1.00, 0.31]; P = 0.2716). Similar results were shown for the adjusted mean between-group difference in the width and volume of bone erosion of the 2–3 metacarpal heads. Significant improvements in bone micro-architecture parameters were shown. The incidence of AEs and serious AEs was similar between the csDMARDs plus denosumab and the csDMARD therapy alone groups (AEs: 52.2% vs 56.5%; serious AEs: 4.3% vs 8.7%).Conclusions: Although the addition of denosumab to csDMARDs did not find statistically significant improvements in bone erosion after 6 months of treatment, numerical improvements in these parameters suggest that the addition of denosumab to csDMARDs may be effective in inhibiting the progression of bone erosion and improving bone micro-architecture

Proposal and Evaluation of Detour Path Suppression Method in PS Reinforcement Learning

Profit sharing (PS) is well known as a kind of reinforcement learning. In a PS method, a reward is generally distributed with a geometrically decreasing function, and the common ratio of the function is called a discount rate. A large discount rate increases the learning speed, but a non-optimal policy may be learned. On the other hand, a small discount rate improves the performance of the policy, but the learning may not proceed smoothly because of the shallow learning depth. In this paper, in order to cope with these problems, we propose a method that reinforces both the detour path and the non-detour path with different discount rates. Finally, this method is applied to a maze problem and an altruistic multi-agent environment to confirm its effectiveness

Global and Spatial Compartmental Interrelationships of Bone Density, Microstructure, Geometry and Biomechanics in the Distal Radius in a Colles' Fracture Study Using HR-pQCT.

BackgroundBone parameters derived from HR-pQCT have been investigated on a parameter-by-parameter basis for different clinical conditions. However, little is known regarding the interrelationships of bone parameters and the spatial distribution of these interrelationships. In this work: 1) we investigate compartmental interrelationships of bone parameters; 2) assess the spatial distribution of interrelationships of bone parameters; and 3) compare interrelationships of bone parameters between postmenopausal women with and without a recent Colles' fracture.MethodsImages from the unaffected radius in fracture cases (n=84), and from the non-dominant radius of controls (n=98) were obtained using HR-pQCT. Trabecular voxel-based maps of local bone volume fraction (L.Tb.BV/TV), homogenized volumetric bone mineral density (H.Tb.BMD), homogenized μFEA-derived strain energy density (H.Tb.SED), and homogenized inter-trabecular distances (H.Tb.1/N) were generated; as well as surface-based maps of apparent cortical bone thickness (Surf.app.Ct.Th), porosity-weighted cortical bone thickness (Surf.Ct.SIT), mean cortical BMD (Surf.Ct.BMD), and mean cortical SED (Surf.Ct.SED). Anatomical correspondences across the parametric maps in the study were established via spatial normalization to a common template. Mean values of the parametric maps before spatial normalization were used to assess compartmental Spearman's rank partial correlations of bone parameters (e.g., between H.Tb.BMD and L.Tb.BV/TV or between Surf.Ct.BMD and Surf.app.Ct.Th). Spearman's rank partial correlations were also assessed for each voxel and vertex of the spatially normalized parametric maps, thus generating maps of Spearman's rank partial correlation coefficients. Correlations were performed independently within each group, and compared between groups using the Fisher's Z transformation.ResultsAll within-group global trabecular and cortical Spearman's rank partial correlations were significant; and the correlations of H.Tb.BMD-L.Tb.BV/TV, H.Tb.BMD-H.Tb.1/N, L.Tb.BV/TV-H.Tb.1/N, Surf.Ct.BMD-Surf.Ct.SED and Surf.Ct.SIT-Surf.Ct.SED were significantly different between controls and fracture cases. The spatial analyses revealed significant heterogeneous voxel- and surface-based correlation coefficient maps across the distal radius for both groups; and the correlation maps of H.Tb.BMD-L.Tb.BV/TV, H.Tb.BMD-H.Tb.1/N, L.Tb.BV/TV-H.Tb.1/N, H.Tb.1/N-H.Tb.SED and Surf.app.Ct.Th - Surf.Ct.SIT yielded small clusters of significant correlation differences between groups.DiscussionThe heterogeneous spatial distribution of interrelationships of bone parameters assessing density, microstructure, geometry and biomechanics, along with their global and local differences between controls and fracture cases, may help us further understand different bone mechanisms of bone fracture

High risk of elevated metal concentrations with 9/10-mm stem trunnions and highly cross-linked polyethylene grafted with poly(2-methacryloyloxyethyl phosphorylcholine) in total hip arthroplasty

Abstract Background The risks of metal release due to fretting and corrosion at the head–neck junction and consequent adverse local tissue reaction (ALTR) have concerns in metal-on-polyethylene (MoP) total hip arthroplasty (THA). Although trunnions have become thinner in diameter to increase the range of motion, it has remained unclear whether this change affects metal release and ALTR in vivo. This study aimed to investigate serum metal concentrations and the prevalence of ALTR in MoP THA with a 9/10-mm stem trunnion. Patients and methods A consecutive series of 37 hips that underwent THA using MoP grafted with poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) with a 9/10-mm trunnion stem were retrospectively reviewed. Serum metal levels were assessed and compared with those in MoP THA with a 10/12-mm trunnion stem. ALTR was diagnosed with serum metal levels and cross-sectional images. The factors associated with serum metal levels were also assessed. Results The median serum cobalt and chromium levels were 1.5 μg/L and 1.0 μg/L in the 9/10-mm group and 0.2 μg/L and 0.4 μg/L in the 10/12-mm group, respectively. ALTR was found in 5 hips of 3 patients. Revision surgery was performed in 4 hips, and all stem trunnions and femoral heads showed severe corrosion. Postoperative walking ability was associated with serum metal levels. Conclusion It was found that a 9/10-mm stem trunnion with MoP grafted with PMPC had high risks of metal release in primary THA. Careful follow-up and cross-sectional imaging are needed to detect ALTR for early revision

Analysis of bone erosions in rheumatoid arthritis using HR-pQCT: Development of a measurement algorithm and assessment of longitudinal changes.

PurposeThe purpose of this study was to establish an algorithm for measuring bone erosions at metacarpophalangeal (MCP) joints using high-resolution peripheral quantitative computed tomography (HR-pQCT), to investigate the precision of measurements, and to assess longitudinal changes in bone erosions among patients with rheumatoid arthritis (RA).MethodsThe 2nd and 3rd MCP joints were scanned at a voxel size of 60.7 μm using second-generation HR-pQCT. Bone erosions on MCP joints were identified using a semi-automated algorithm we developed, and each erosion parameter was measured. Measurement reproducibility was evaluated in 19 healthy subjects using intraclass correlation coefficients (ICCs) and root mean square percent coefficient of variance (RMS%CV). Finally, longitudinal changes in bone erosions over a period of 12 months were assessed in 26 patients with RA based on the calculated least significant change (LSC).ResultsReproducibilities for measurement parameters regarding bone erosions with our algorithm were good (all ICCs ≥ 0.98; all RMS%CVs ConclusionsThe measurement algorithm developed for bone erosions at MCP joints showed good reproducibility. Both progression and repair of bone erosions were observed in patients with RA even after 12 months of appropriate treatment. Our algorithm may be useful to investigate the etiology of RA and assess drug efficacy