Average Joint Research Articles

Understanding US adolescents’ and emerging adults’ overestimation of their cannabis use quantity

Cannabis is the most used federally illicit drug in the United States (U.S). Understanding how accurate adolescents and emerging adults are at estimating their cannabis use quantity is important, as this lays the groundwork for understanding and studying the outcomes associated with cannabis use. This study aimed to assess the accuracy of cannabis quantity in grams for a typical joint and identify predictors of accuracy among U.S. adolescents and emerging adults. Participants (n = 50; aged 14–21) who reported using joints in the past 30 days completed measures of cannabis use characteristics and problems, were asked to “eyeball” the amount of cannabis in their average joint using a cannabis substitute and estimated the number of grams. The cannabis substitute was then weighed in grams. Paired samples t-tests indicated that participants estimated significantly more grams in a joint (M=.82; SD = 0.46) than the actual amount of the surrogate substance (M=.47; SD = 0.21; t(49) = 6.32, p < 0.001, d = 0.89). A linear regression analysis indicated that the age of cannabis initiation (B = -0.13, p=.002) and cannabis use problems (B = -0.03, p=.009) were negatively and significantly associated with discrepancies in estimated grams. Specifically, being older when first using cannabis and reporting more cannabis use problems were linked to less overestimation of grams per joint. These findings align with previous research demonstrating a tendency to overestimate cannabis quantity and contribute novel insights by identifying predictors of estimation accuracy. This study underscores the importance of considering age and cannabis-related problems when assessing the reliability of self-reported cannabis use quantities among adolescents and emerging adults.

Pressure distribution based 2D in-bed keypoint prediction under interfered scenes

In-bed pose estimation holds significant potential in various domains, including healthcare, sleep studies, and smart homes. Pressure-sensitive bed sheets have emerged as a promising solution for addressing this task considering the advantages of convenience, comfort, and privacy protection. However, existing studies primarily rely on ideal datasets that do not consider the presence of common daily objects such as pillows and quilts referred to as interference, which can significantly impact the pressure distribution. As a result, there is still a gap between the models trained with ideal data and the real-life application. Besides the end-to-end training approach, one potential solution is to recognize the interference and fuse the interference information to the model during training. In this study, we created a well-annotated dataset, consisting of eight in-bed scenes and four common types of interference: pillows, quilts, a laptop, and a package. To facilitate the analysis, the pixels in the pressure image were categorized into five classes based on the relative position between the interference and the human. We then evaluated the performance of five neural network models for pixel-level interference recognition. The best-performing model achieved an accuracy of 80.0% in recognizing the five categories. Subsequently, we validated the utility of interference recognition in improving pose estimation accuracy. The ideal model initially shows an average joint position error of up to 30.59 cm and a Percentage of Correct Keypoints (PCK) of 0.332 on data from scenes with interferences. After retraining on data including interference, the error is reduced to 13.54 cm and the PCK increases to 0.747. By integrating interference recognition information, either by excluding the parts of the interference or using the recognition results as input, the error can be further minimized to 12.44 cm and the PCK can be maximized up to 0.777. Our findings represent an initial step towards the practical deployment of pressure-sensitive bed sheets in everyday life.

An efficient synergistic double-sided friction stir spot welding method: A case study on process optimization, interfacial characteristics and mechanical properties of 2198-T8 aluminum‑lithium alloy joints

Friction stir spot welding has important applications in the joining of thin metallic plates. However, the asymmetric thermomechanical action inherent in the single-sided friction stir spot welding inevitably generates the hook defect at the joint interface, and the defect deteriorates with the improvement of the interfacial metallurgical bonding, which causes the irreconcilable contradiction and significantly restricts the breakthrough of the process stability and welding efficiency. The synergistic double-sided probeless friction stir spot welding (SDP-FSSW) technology proposed in this study adopts a dual-axis synergistic control system, which introduces intense plastic deformation from both sides of the interface to form a wavy hook by accurate axial motion during the welding process. This innovative process solves the problem of hook warpage while realizing rapid metallurgical bonding and mechanical interlocking at the interface, thus obtaining AA2198-T8 aluminum‑lithium alloy spot joints with a tensile/shear strength exceeding 9kN in a short dwell time (0–3 s). Through response surface methodology, the optimal process parameters are identified, i.e. rotation speed of 603 rpm, dwell time of 3 s, and plunge depth of 0.26 mm, at which condition the average joint strength is 13.0 ± 0.5kN, a 47 % increase compared to an optimized joint of single-sided probeless friction stir spot welding (8.9kN). The optical microscope examination shows that the wavy hook can be adjusted by the rotation speed and the higher rotation speeds will make the wave disappear and produce an approximately straight interface. The fractographic analysis shows that the wavy hook can inhibit crack propagation and has good mechanical interlocking effect, but the flat hook at high rotation speeds leads to crack propagation directly along the interface, and the failure mode is changed from plug-pull fracture to interfacial fracture. Therefore, the joint strength at 1000 rpm is only 7.0kN, which decreases by about 47 % compared with the optimal strength. The electron backscattering diffraction analysis shows that continuous dynamic recrystallization occurs in the hook region and good metallurgical bonding is formed, and there are also some discontinuous dynamic recrystallized grains distributed between the large grains due to the larger strain rates and lower temperature at the interface during the SDP-FSSW process. It has been found that the wavy hook with good metallurgical bonding and mechanical interlocking can be introduced in spot welded joints by controlling the interface forming, which is a viable method to create high quality, efficient and reliable spot joints.

A Dual‐Mode, Scalable, Machine‐Learning‐Enhanced Wearable Sensing System for Synergetic Muscular Activity Monitoring

AbstractSimultaneously detecting muscular deformation and biopotential signals provides comprehensive insights of the muscle activity. However, the substantial size and weight of detecting equipment result in reduced wearer benefits and comfort. It remains a challenge to establish a flexible and lightweight wearable system for mapping muscular morphological parameters while collecting biopotentials. Herein, a fully integrated dual‐mode wearable system for monitoring lower‐extremity muscular activity is introduced. The system utilizes an iontronic pressure sensing matrix (16 channels) for precise mapping of force myography (FMG) within a single muscle, while simultaneously capturing the muscular electrophysiological signals using a self‐customized electromyography (EMG) sensing module. Experimental results show that the bimodal sensing system is capable of capturing complementary and comprehensive aspects of muscular activity, which reflect activation and architectural changes of the muscle. By leveraging machine learning techniques, the integrated system significantly (p &lt; 0.05) enhances the average gait phase recognition accuracy to 96.35%, and reduces the average ankle joint angle estimation error to 1.44°. This work establishes a foundation for lightweight and bimodal muscular sensing front‐ends, which is promising in applications of human–machine interfaces and wearable robotics.

Experimental and numerical investigation on failure behaviour of aluminum-polymer friction stir composite joints

Friction stir composite joints between an aluminum alloy (AA6082-T6) and reinforced polymer (NorylTM GFN2) were studied regarding their failure characteristics. A comprehensive analysis on the mechanical behaviour of the joints was carried out, assessing the resulting deformed shape, the associated strain field and the observed failure modes using a digital image correlation (DIC) system and comparing with a finite elements method (FEM) model. The numerical model evidenced a good fitness to the experimental results since both the displacements and strain fields were found to be very similar. Both numerical and experimental strain fields in the longitudinal direction exhibited a localized spot of highly strained material, clearly indicating the nucleation site. Since secondary bending occurs in structural elements under tension due to geometrical and stiffness asymmetries, as is the case of overlap composite joints, a bending stress is induced, increasing the local stress compared to the nominal tension stress values. The ultimate tensile stress of the joints was found to range between 60.2 and 70.4 MPa, leading to an average joint efficiency of 82.6 %. The bending factor (kb) at the failure region was found to be 2.0, which means that the bending stress accounts for 2/3 of the total stress, acting as main failure catalyst.

Kinematic network of joint motion provides insight on gait coordination: An observational study on Parkinson's disease

The analysis of gait kinematics requires to encode and collapse multidimensional information from multiple anatomical elements. In this study, we address this issue by analyzing the joints' coordination during gait, borrowing from the framework of network theory. We recruited twenty-three patients with Parkinson's disease and twenty-three matched controls that were recorded during linear gait using a stereophotogrammetric motion analysis system. The three-dimensional angular velocity of the joints was used to build a kinematic network for each participant, and both global (average whole-body synchronization) and nodal (individual joint synchronization, i.e., nodal strength) were extracted. By comparing the two groups, the results showed lower coordination in patients, both at global and nodal levels (neck, shoulders, elbows, and hips). Furthermore, the nodal strength of the left elbow and right hip in the patients, as well as the average joints' nodal strength were significantly correlated with the clinical motor condition and were predictive of it. Our study highlights the importance of integrating whole-body information in kinematic analyses and the advantages of using network theory. Finally, the identification of altered network properties of specific joints, and their relationship with the motor impairment in the patients, suggests a potential clinical relevance for our approach.

Predictive value of joint fluid volume on advanced pre-procedure imaging related to success of arthrocentesis and presence of septic arthritis.

Septic arthritis is a dangerous medical condition requiring prompt diagnosis, often via arthrocentesis. A "dry tap" occurs when no fluid is aspirated. We hypothesized that the absence of a joint effusion on pre-procedure advanced imaging would reliably predict a dry tap and exclude septic arthritis. A cohort of 217 arthrocentesis cases of large joints (hips, shoulders, knees) from our institution, with pre-procedure advanced imaging (CT, MR, US) of the same joint performed within the previous 48h, was analyzed. Exclusion criteria included non-native joints or inadequate imaging of the affected joint. These cases underwent blinded review by 4 radiologists who measured the deepest pocket of joint fluid on the pre-procedure imaging. Wilcoxon rank-sum test was performed comparing joint fluid pocket size to outcomes of successful aspiration and final diagnosis. A smaller average joint pocket fluid size was present on advanced imaging in both dry taps compared with successful arthrocenteses (p < .0001), and in uninfected joints compared with septic joints (p = .0001). However, the overlap of values was too great to allow for a perfectly predictive cutoff. 29% (5/17) of patients with no visible joint fluid on pre-aspiration imaging underwent successful arthrocentesis, one case representing septic arthritis. Volume of joint fluid on advanced pre-arthrocentesis imaging cannot reliably predict subsequent dry tap nor exclude septic arthritis.

Pins and Rubber Band Traction System Combined with Internal Fixation for Intra-articular Fractures of the Proximal Interphalangeal Joints.

Background: Intra-articular fractures of the proximal interphalangeal joint (PIPJ) can result in poor outcomes if inadequately treated. Dynamic external fixation and internal fixation with plates and/or screws are two treatment options. The role of combining these two methods is unclear. The aim of this study is to determine the outcomes of patients with intra-articular fractures of the PIPJ treated with a combination of dynamic external fixation with a plate and/or screws. Methods: A retrospective review was conducted on 18 consecutive cases of intra-articular fractures of the PIPJ treated with pins and rubber band traction system (PRTS) combined with dorsal internal fixation with plates and/or screws. The patients' average age was 51 years (range: 20-81 years). The fracture patterns were volar-type (n=2), dorsal-type (n=4) and pilon-type (n=12). Data with regard to time to surgery, interphalangeal joint range of motion, grip strength, VAS for pain, Quick DASH score, complications, duration of follow-up and return to work were collected. Results: The levels of articular involvement were stable (n=1), tenuous (n=5) and unstable (n=12). The average time to surgery was 9 days, and the average follow-up period was 15 months. The fracture was fixed with a dorsal plate and screws in 10 patients and with only screws in eight patients. All patients had PRTS. All patients returned to their original occupation and the fractures united in good alignment. The average grip strength was 86% of that of the unaffected side. The average active PIPJ motion was 85° (range: 50°-106°), and the average active distal interphalangeal joint (DIPJ) motion was 48° (range: 10°-90°). Conclusions: Our results show that a combination of PRTS and open reduction and fixation with plate and/or screws achieved a good range of motion and articular reduction. Level of Evidence: Level IV (Therapeutic).

Effect of die design on microstructure and mechanical joint strength in friction self-piercing riveted AA7055-T76 and AA7055-T76

In the present study, a unique friction self-piercing riveting (F-SPR) was applied to join high-strength, low-ductility aluminum alloy (AA) 7055-T76 and AA7055-T76 to mitigate a cracking issue. Also, the effect of die design on both joint formation and the mechanical joint performance were investigated. A crack-free joint was achieved when joining AA7055-T76 and AA7055-T76 by F-SPR. As the bottom diameter of the die increased, the mechanical interlocking distance initially increased then became almost saturated. At the same time, the solid-state bonding gradually disappeared, and the lap-shear fracture changed from bottom aluminum fracture to rivet pull-out with partial bottom aluminum fracture. The average maximum lap-shear joint strength of 11.57 kN and cross tension of 5.65 kN were achieved from the D2 die design owing to the combined contributions from high mechanical interlocking distance and good solid-state bonding at the joint interface. Ultrafine grain refinement was observed at the region next to the rivet shank outer surface and along the materials flow line between the top and bottom aluminum sheet in the rivet cavity. Because of the same joint-process parameters, the hardness profile at the joints made by different dies did not show obvious differences. As the distance from the base metal to the rivet outer surface decreased, frictional heat caused the hardness to initially decrease from 190 to 150 HV in the heat-affected zone. Hardness increased up to 175 HV in the thermomechanical affected zone (TMAZ-I) owing to large plastic deformation.

The Effect of Unequal Crank Arm Lengths and Cycling-Specific Prostheses for Recreational Riders with a Transtibial Amputation.

We determined the effects of shorter affected side (AS) crank arm lengths and cycling with two different prostheses on joint and crank power, asymmetry, and net efficiency. Twelve participants with a TTA rode at 1.5 W·kg -1 with equal (175 mm) and shorter AS crank arms (160, 165, 170 mm) using a daily-use prosthesis and CSP. We used statistical parametric mapping to determine differences in instantaneous joint and crank power between prostheses and linear mixed-effects models to compare average joint and crank power, asymmetry, and net efficiency. Shorter AS crank arm lengths reduced the magnitude of peak positive ( P ≤ 0.001) and negative ( P < 0.001) crank power on the AS. Use of a CSP increased the magnitude of peak positive knee power ( P < 0.001) and decreased the magnitude of peak negative crank power ( P < 0.001) on the AS compared with a daily-use prosthesis. Shorter AS crank arm lengths while using a CSP reduced average hip joint ( P = 0.014) and hip transfer ( P = 0.025) power asymmetry from 35% to 20% and 118% to 62%, respectively. However, we found no significant differences in AS average joint or crank power, knee joint or crank power asymmetry, or net efficiency. Cycling at 1.5 W·kg -1 with unequal crank arm lengths and CSP improves hip joint power and hip transfer power asymmetry but does not alter crank asymmetry or net efficiency for recreational cyclists with a TTA.

Stroke walking and balance characteristics via principal component analysis

Balance impairment is associated gait dysfunction with several quantitative spatiotemporal gait parameters in patients with stroke. However, the link between balance impairments and joint kinematics during walking remains unclear. Clinical assessments and gait measurements using motion analysis system was conducted in 44 stroke patients. This study utilised principal component analysis to identify key joint kinematics characteristics of patients with stroke during walking using average joint angles of pelvis and bilateral lower limbs in every gait-cycle percentile related to balance impairments. Reconstructed kinematics showed the differences in joint kinematics in both paretic and nonparetic lower limbs that can be distinguished by balance impairment, particularly in the sagittal planes during swing phase. The impaired balance group exhibited greater joint variability in both the paretic and nonparetic limbs in the sagittal plane during entire gait phase and during terminal swing phase respectively compared with those with high balance scores. This study provides a more comprehensive understanding of stroke hemiparesis gait patterns and suggests considering both nonparetic and paretic limb function, as well as bilateral coordination in clinical practice. Principal component analysis can be a useful assessment tool to distinguish differences in balance impairment and dynamic symmetry during gait in patients with stroke.

W-Leg Jumping Robot: Mechanical Design, Dynamical Analysis and Simulation of Jumping Dual Wheel-Leg Hybrid Robot

This study primarily focuses on design, mathematically model and simulate a novel two wheel-legged hybrid robot called W-Leg Jumping robot, which has a unique ability to overcome step-like obstacles efficiently. In general, in transformable wheel-leg robot studies, the leg and wheel structure perform their movements in an interdependent manner. However, in this study, it is aimed to design a robot in which the leg and wheel structure can move independently of each other and to develop a robot that can easily overcome obstacles on flat surfaces with the wheel mode and with the leg mode. The robot can fold its legs hidden within the wheels and deploy its two degree of freedom (DoF) legs when it detects step-like obstacles. This mechanism allows the robot to overcome an obstacle with a height of twice the radius of the robot's open/close mechanism of the legs, along with the two-dimensional kinematic and dynamic analyzes of the legs, are presented in detail within the scope of this study proportional-integral-derivative (PID) controller is designed to control the joint angles of the legs. The reference angle values to be followed according to the height of the obstacle are determined using artificial neural network (ANN). Additionally, motion simulations of the robot are conducted for four different obstacle heights (20, 30, 40, and 50 cm). As a result of the PID controller, when exceeding the highest obstacle of 50 cm, the average absolute joint angular tracking error is max. 1.8829°, average tracking error max. 0.265 s and max.

Markerless motion capture provides repeatable gait outcomes in patients with knee osteoarthritis

Motion analysis has seen minimal adoption for orthopaedic clinical assessments. Markerless motion capture solutions, namely Theia3D, address limitations of previous methods and provide gait outcomes that are robust to clothing choice and repeatable in healthy adults. Repeatability in orthopaedic populations has not been investigated and is important for clinical utility and adoption. The purpose of this study was to evaluate the repeatability of Theia3D for gait analysis in a knee osteoarthritis population. Ten orthopaedic patients with knee osteoarthritis underwent gait analysis on three visits, with an average of 8 days between. Participants were recorded during one-minute overground walking trials at self-selected typical and fast speeds by 8 synchronized video cameras. Video data were processed using Theia3D. Intraclass correlations were used to examine the repeatability of temporal distance metrics as well as segment lengths of the underlying kinematic model. Inter-trial and inter-session variability of lower extremity joint angles were estimated for each point of the gait cycle. Intraclass correlations were greater than 0.98 for all temporal distance metrics for both speeds. Lower body segment lengths had intraclass correlations above 0.90. Participant average joint angle waveforms displayed consistent patterns between visits. The average inter-trial and inter-session variability in joint angles across speeds were 1.17 and 1.45 degrees, respectively. The variability in joint angles between visits was less than typically reported for marker-based methods. Gait outcomes measured with Theia3D were highly repeatable in patients with knee osteoarthritis providing further validation for its use in clinical assessment and longitudinal studies.

Hybrid joints consisting of pre-tensioned bolts and a bonded connection—The influence of adhesives on the load-bearing capacity

This study explores the intricate mechanics of hybrid joints, which combine prestressed bolts and adhesive bonding, with a focus on increasing the joint capacity of steel structures. Despite their potential, the fundamental behaviour of these joints is not fully understood. The research focuses on unravelling the load-bearing capacity of these hybrid joints, emphasising the influence of the adhesive properties. The unique manufacturing process, involving the pre-tensioning of bolts while the adhesive is uncured, introduces additional dependencies not present in conventional adhesive joints. Analysis of the mechanical and physical properties of five adhesives provides key insights into the mechanics of load transfer and failure modes in hybrid joints, providing a comprehensive understanding. The study shows that load transfer occurs through micron-thin adhesive layers, highlighting the significant influence of adhesive properties on joint performance. Epoxies emerge as the top performers, with 2.5 times the average friction joint and more than five times the average bonded joint capacity, indicating their superiority in hybrid joint applications. Hybrid joints show significantly less variation than adhesive and friction joints, underlining their consistency and reliability in structural applications. When comparing hybrid and bonded joints with the same adhesive (SW7240), the variance was suppressed to one seventh by the application of preloaded bolts, with practical implications for design values based on quantiles. The study establishes correlations between joint strength and adhesive properties, emphasising the critical role of Young's modulus and tensile strength. It also finds that the elongation of hybrid joints at break is almost entirely dependent on load capacity, with viscosity having a lesser effect. Fracture surface investigations provide insight into the failure modes of hybrid joints, highlighting differences from those observed in frictional or purely bonded joints. This comprehensive study, combining experimental campaigns and in-depth analysis, provides valuable insights into the intricate relationships between joint capacity and adhesive properties in hybrid joints. The findings guide the selection of appropriate adhesives and provide the basis for the development of accurate load prediction methods, unlocking the full potential of hybrid joints and overcoming the limitations of conventional joining techniques in steel structures. Further research is encouraged to investigate the influence of adhesive class, post-tensioning stability and the nuanced mechanics of load transfer in these innovative joints.

Geometric Co-Ordinate Feature Point Estimation (Gfpe): A Novel Approach to Analyse Of Kinematic Characteristics of Yoga Asanas Based on Anybody Simulation Software

The kinematic characteristics of yoga asanas is crucial for comprehending the biomechanical demands and benefits associated with these postures. Utilizing AnyBody simulation software, researchers delve into the intricate movements and alignments involved in various yoga poses. Through advanced biomechanical modeling, AnyBody allows for the analysis of joint angles, muscle activations, and forces exerted on the body during asana practice. This paper presented an analysis of the kinematic characteristics of yoga asanas using AnyBody Simulation in conjunction with Geometric Co-ordinate Feature Point Estimation (GFPE). By integrating advanced biomechanical modelling capabilities of AnyBody with GFPE’s precision in identifying geometric features, this study aims to elucidate the intricate movements and alignments inherent in various yoga poses. Through comprehensive simulations, joint angles, muscle activations, and forces exerted on the body during asana practice are meticulously analyzed. The examination of body posture with GFPE in the downward-facing dog pose, the average joint angles of the shoulder, elbow, and wrist were found to be 130°, 150°, and 160°, respectively. Additionally, muscle activation levels were measured, with the triceps brachii exhibiting an average activation of 70% of maximum voluntary contraction during the pose.

The Effect of Different Weight Plate Widths (Bumper vs. Standard) on the Biomechanics of the Bench Press.

Fiedler, MJ, Triplett, NT, Hamilton, KC, Needle, AR, and van Werkhoven, H. The effect of different weight plate widths (bumper vs. standard) on the biomechanics of the bench press. J Strength Cond Res 38(4): e143-e149, 2024-Anecdotal evidence suggests that bumper plates impact lifts in powerlifting and weightlifting differently than standard cast iron plates, but whether biomechanical differences exist between lifts using bumper versus standard plates has not been investigated. Eleven resistance-trained subjects performed the bench press at 70, 80, and 90% of their 1 repetition maximum (1RM) while being blinded to whether they were lifting with bumper or standard plates. Motion data were captured by an 8-camera motion capture system, and electromyography (EMG) data were recorded for the anterior deltoid, pectoralis major, and triceps brachii. Repeated-measures analysis of variances showed a significant main weight effect for time under tension (p < 0.001), total work (p < 0.001), and muscle activity through EMG (across all muscles; p < 0.001) and a significant weight × joint interaction effect for average joint moment (p < 0.001) and peak joint moment (p < 0.001). However, there were no significant differences observed between the different weight plates for any of the measures. The main finding of the study suggests that there are no biomechanical differences between using bumper plates compared with standard plates during the bench press lift.

Minimal but potentially clinically relevant anteroinferior position of the humeral head following traumatic anterior shoulder dislocations: A 3D-CT analysis.

In unstable shoulders, excessive anteroinferior position of the humeral head relative to the glenoid can lead to a dislocation. Measuring humeral head position could therefore be valuable in quantifying shoulder laxity. The aim of this study was to measure (1) position of the humeral head relative to the glenoid and (2) joint space thickness during passive motion in unstable shoulders caused by traumatic anterior dislocations and in contralateral uninjured shoulders. A prospective cross-sectional CT-study was performed in patients with unilateral anterior shoulder instability. Patients underwent CT scanning of both injured and uninjured side in supine position (0° abduction and 0° external rotation) and in 60°, 90°, and 120° of abduction with 90° of external rotation without an external load. Subsequently, 3D virtual models were created of the humerus and the scapula to create a glenoid coordinate system to identify poster-anterior, inferior-superior, and lateral-medial position of the humeral head relative to the glenoid. Joint space thickness was defined as the average distance between the subchondral bone surfaces of the humeral head and glenoid. Fifteen consecutive patients were included. In supine position, the humeral head was positioned more anteriorly (p = 0.004), inferiorly (p = 0.019), and laterally (p = 0.021) in the injured compared to the uninjured shoulder. No differences were observed in any of the other positions. A joint-space thickness map, showing the bone-to-bone distances, identified the Hill-Sachs lesion footprint on the glenoid surface in external rotation and abduction, but no differences on average joint space thickness were observed in any position.

Friction stir extrusion of thin AA 7075-T6 into low-carbon steel: Effects of low weld pitch value

Friction stir extrusion, a derivative process of friction stir welding, forms a mechanical joint between workpieces by forging one into a prefabricated geometry within the other. Thin sheet AA7075-T651 extrusion joints were made into an O-ring dovetail channel within a low-carbon steel workpiece. The effects of low weld pitch process parameters on joint characteristics between the extruded thin sheet AA7075-T651 and low-carbon steel were observed. The weld pitch was varied from 0.02 to 0.05 mm rev−1. No material mixing was observed. Tensile-shear test results were normalised by sample width. The 0.04 mm rev−1 weld pitch group yielded the highest average joint strength at 493 N mm−1. The weld pitch parameters reduced machine in-process forces without a large decrease in joint strength.

Morphological Evaluation of Lumbar Facet Joints in Professional Baseball Players.

Many professional baseball players experience low back pain, a major cause of which is lumbar facet joint arthropathy. To evaluate the relationship between the dominant hand side and facet joint morphology in baseball movement. Cross-sectional study; Level of evidence, 3. Participants were 25 Japanese professional baseball players (11 pitchers and 14 fielders) with low back pain and lower limb symptoms. Player age, hand dominance, and length of professional playing experience were recorded, and the lateral diameter of all lumbar facet joints was determined from the axial computed tomography scans. We defined the facet joints ipsilateral and contralateral to the dominant hand as dominant and nondominant, respectively. The nondominant-to-dominant (N/D) ratio of the lateral diameter was calculated, and differences between the pitchers and fielders were analyzed using the unpaired t test. The average player age and length of professional playing experience were 26.9 years (range, 19-37 years) and 7.2 years (range, 1-15 years), respectively. The right hand was dominant in 9 pitchers and 5 fielders, while the left hand was dominant in 2 pitchers and 9 fielders. In pitchers, the average lateral facet joint diameter on the nondominant side was significantly larger than on the dominant side at all vertebral levels except L1 to L2 (P < .05 for all). The N/D ratio for each facet joint was 1.06 (L1-L2), 1.11 (L2-L3), 1.10 (L3-L4), 1.12 (L4-L5), and 1.12 (L5-S1). In fielders, the average lateral facet joint diameter on the dominant side was significantly larger than on the nondominant side at L3 to L4 (P < .05), with N/D ratios of 0.98 (L1-L2), 0.96 (L2-L3), 0.94 (L3-L4), 0.97 (L4-L5), and 0.98 (L5-S1). The N/D ratio was significantly larger in pitchers than in fielders at all levels (P < .05 for all). The facet joints of professional baseball players were enlarged asymmetrically, with different tendencies observed between pitchers and fielders. Although pitching and batting are movements that transmit the rotation from the lower limbs to the upper limbs, the effects of rotation and lateral flexion were associated significantly with facet joint hypertrophy.

Alternative Surgical Treatment Method for 5th Metacarpal Neck Fractures: Comparison of Clinical Outcomes of Intramedullary and Transverse K-Wire Fixations with Additional Antirotational K-Wire.

The purpose of this study was to assess the clinical outcomes and complications associated with intramedullary and transverse K-wire fixations of 5th metacarpal neck fractures. Patients who were operated for 5th metacarpal neck fractures between 2019 and 2022 were evaluated retrospectively. Regarding the surgical treatment methods, patients were assessed by dividing them into two groups. The first group comprised patients who underwent treatment with an intramedullary K-wire. The second group comprises patients who underwent transverse K-wire fixation. The average quick DASH score of all patients was 5.6±4.7 in the intramedullary K-wire fixation group and 5.9±5.1 in the transverse K-wire fixation group. An average 5th finger metacarpophalangeal joint extension limitation was 6.2±5.7° in the intramedullary fixation group and 6.1±5.8° in the transverse K-wire group. The mean radiological union time was 4.9±0.7 weeks in the intramedullary fixation group and 5.1±0.7 weeks in the transverse K-wire group. No statistically significant difference was found between the quick DASH scores and degrees of the MCP joint extension limitation ( p=0.785). Intramedullary fixation and transverse K-wire fixations are effective surgical treatment methods for metacarpal neck fractures. It has been reported that the intramedullary fixation method in metacarpal bone fractures is more effective than the fixation methods with cross and transverse K-wire. But our results revealed no difference in clinical outcomes between the two surgical fixation methods. We observed no statistically significant difference between the two fixation techniques with regard to union, clinical outcomes, or complications. intramedullary fixation; metacarpal neck fracture; transverse K-wire fixation.