Finger Joints Research Articles

Minimalist Design for Multi-Dimensional Pressure-Sensing and Feedback Glove with Variable Perception Communication

Immersive human–machine interaction relies on comprehensive sensing and feedback systems, which enable transmission of multiple pieces of information. However, the integration of increasing numbers of feedback actuators and sensors causes a severe issue in terms of system complexity. In this work, we propose a pressure-sensing and feedback glove that enables multi-dimensional pressure sensing and feedback with a minimalist design of the functional units. The proposed glove consists of modular strain and pressure sensors based on films of liquid metal microchannels and coin vibrators. Strain sensors located at the finger joints can simultaneously project the bending motion of the individual joint into the virtual space or robotic hand. For subsequent tactile interactions, the design of two symmetrically distributed pressure sensors and vibrators at the fingertips possesses capabilities for multi-directional pressure sensing and feedback by evaluating the relationship of the signal variations between two sensors and tuning the feedback intensities of two vibrators. Consequently, both dynamic and static multi-dimensional pressure communication can be realized, and the vibrational actuation can be monitored by a liquid-metal-based sensor via a triboelectric sensing mechanism. A demonstration of object interaction indicates that the proposed glove can effectively detect dynamic force in varied directions at the fingertip while offering the reconstruction of a similar perception via the haptic feedback function. This device introduces an approach that adopts a minimalist design to achieve a multi-functional system, and it can benefit commercial applications in a more cost-effective way.

Anthropomorphic modular gripper finger actuated by antagonistic wire and shape-memory alloy (SMA) springs

Abstract. The traditional underactuated grippers can only passively adapt to the contour of the object, and the passive contact process may lead to the object slipping, affecting the stability of the grasping process. In this paper, an anthropomorphic modular gripper finger actuated by antagonistic wire and shape-memory alloy (SMA) springs, which can actively control the grasping morphology according to the characteristics of the objects to be grasped, is proposed. The wire drive simulates the flexor muscle, and the SMA and reset springs simulate the extensor muscles of the finger, which antagonistically control the grasping morphology of the finger. It is more in line with the grasping characteristics of the human hand. According to the moment equilibrium principle of the finger joints, the deformation model of the gripper is established, the influence of the wire tension and the equivalent stiffness of the finger joints on the grasping morphology is analyzed, and the theoretical joint angle results are verified by the Adams simulation; finally, the experimental system of the gripper is constructed, and the verification of the deformation morphology of the single finger and the gripper's enveloping–grasping experiments is completed. The results show that according to the contour size of the object, by actively controlling the wire force of the gripper and the equivalent stiffness of the interphalangeal joints, the enveloping–grasping action of different objects can be completed and the stable grasping of objects of different shapes and sizes can be realized.

Application of ergonomics in the design of desks and chairs for primary school students in Ho Chi Minh City

The application of ergonomics in the product design is currently of great interest, especially for products used in schools, to reduce school-related health issues. This article presented statistical data on the body size of male and female primary school students, aged 7 - 8 years old in Ho Chi Minh City including average body size, size in standing and sitting position. Additionally, the article also gave the specifications of sawn acacia wood, acacia finger joint wood used for the production of student desks and chairs. By integrating the students'body dimensions, ergonomic parameters, Ministry of Health guidelines, and the selection of acacia wood materials, the author devised a set of desks and chairs suitable for elementary school students up to grade 3. The desk dimensions were as follows: height 570 mm, desk width 450 mm, desk length 600 mm; for the chair: height 650 mm, seat height 340 mm, seat width 310 mm, seat depth 264 mm. The angle between the backrest and the chair surface was 95o. As a result, a desk and chair set was designed, followed by trial production, and a proposed manufacturing process for student desks and chairs.

Evaluation of split flexor carpi ulnaris tendon transfer for fingers and thumb extension, pronator teres transfer for wrist extension in high radial nerve palsy

Background: The radial nerve is the largest terminal branch of the brachial plexus. Loss of radial nerve function creates a significant disability in the hand. The grip is severely impaired following loss of radial nerve function as a result of loss of extension of wrist, metacarpophalangeal joints of fingers and interphalangeal joints of the thumb. Methods: Prospective, quasi experimental study carried out for 3 years at National Institute of Traumatology and Orthopaedic Rehabilitation (NITOR). Forty-eight patients of high radial nerve palsy were selected for tendon transfer (split FCU tendon to EDC and EPL) and PT transferred to ECRB. Results: Mean age of the patients was 28.92 years (range 15-45 years), significantly higher in 26-35 years age group. There was preponderance of injury to the dominant right side (58.33%) than the none-dominant left side (41.67%). Motor vehicle accident (66.67%) was the common cause of injury followed by assault (33.33%). Out of 48 patients, 28 patients score 8-9 (excellent), 16 patients score 7 (good), 4 patients scores 5 (fair). So that, total 44 patients achieved satisfactory outcome (91.67%) and 4 patients achieved unsatisfactory outcome (8.33%). All patients can extend their wrist, fingers and thumb. Beyond this, all patients can flex their fingers up to mid palmar crease and thumb can be extended separately-independent of EDC function. Conclusions: Transfer of split FCU tendon to EDC and EPL for fingers and thumb extension in irreparable and neglected long standing high radial nerve palsy results significant functional outcome.

Effect of groove splint fixation on early swelling and blood flow velocity of the injury limb in elderly patients with distal radius fractures

To observe the effects of groove splint fixation on early hand swelling, blood flow velocity, and clinical function in elderly patients with distal radius fractures. Between March 2021 and February 2022, 64 patients of unilateral closed distal radius fractures were treated with manual reduction and external fixation with splints. There were 10 males and 54 females, the age ranged from 60 to 78 years old, with an average age of (67.7±4.7) years old. According to the order of admission, the patients were divided into the groove splint group and the conventional splint group, with 32 cases in each group. In the groove splint group, there were 4 males and 28 females, with an average age of (68.6±4.8) years old. There were 13 patients with left-sided fractures, and 19 patients with right-sided fractures, with 22 cases classified as AO type A and 10 cases as AO type C. The mean time from injury to treatment was 3.0 (2.0, 4.0) h. In the conventional splint group, there were 6 males and 26 females, with an average age of (66.9 ± 4.4) years old. There were 17 patients with left-sided fractures and 15 patients with right-sided fractures, with 20 cases classified as AO type A and 12 cases as AO type C. The mean time from injury to treatment was 3.0 (2.0, 5.0) h. After manual reduction, patients were treated with groove splint or conventional splint. Swelling, assessed by the difference in limb circumference between the injured and healthy limbs, was measured at 1, 3, 7, and 14 days post-treatment. Blood flow velocities in the superficial palmar arch and dorsal metacarpal veins were measured at 1, 3, and 7 days post-treatment. Radiographic evaluations of radial styloid height, palmar tilt, and ulnar variance were performed preoperatively and 3 months post-treatment. Functional outcomes were assessed using the DASH (Disabilities of the Arm, Shoulder, and Hand) score 3 and 12 months post-treatment. Statistical analyses were conducted to compare the outcomes between the two groups. All 64 patients were followed up for the least 12 months. The swelling value of the palm in the groove splint group [(1.897±0.071) cm, (1.200±0.169) cm, (0.994±0.085) cm] was significantly improved compared to the conventional splint group[(2.283±0.268) cm, (1.893±0.269) cm, (1.183±0.126) cm] on days 3, 7, and 14 days posttreatment, with a statistically significant difference (P<0.001). On the first and third day after splint fixation, the difference in blood flow velocity of the superficial palmar arch in the groove splint group(0.017±0.009), (0.018±0.011) L·min-1 were lower than that in the conventional splint group(0.023±0.011), (0.025±0.013) L·min-1, with statistical significance (P<0.05). On the 3rd and 7th days, the difference was not statistically significant (P>0.05). Comparison of blood flow velocity differences between the dorsal metacarpal vein and the two groups showed no statistically significant difference on the first day after splint fixation (P>0.05). On the 3rd and 7th days, the blood flow velocity difference between the groove splint group[(0.037±0.019), (0.021±0.013) L·min-1] decreased compared to the conventional splint group[(0.062±0.033), (0.037±0.022) L·min-1], and the difference was statistically significant (P<0.05). There was no statistically significant difference in the palm angle, ulnar deviation angle, and radius height of the distal radius before and after reduction (P>0.05). The DASH score showed a statistically significant difference at follow-up 3-month[(6.1±2.8) scores vs (8.2±3.7) scores] , P<0.05, but no statistically significant difference at follow-up 12-month (P>0.05). Fixing distal radius fractures with groove splints in the early stage can reduce the impact on the blood flow velocity of the superficial palmar arch and dorsal palmar vein, reduce venous reflux obstruction and swelling of injury limb, alleviate wrist and finger joint stiffness, and improve early clinical efficacy of the affected limb. However, it has no significant impact on clinical function one year after injury.

Clustering of tropical species through multivariate analysis of the bonding properties of edge-glued panels (EGP)

Tropical woods have high added value, and the use of waste for panel production is an initiative to add more value to this material, typically consisting of various species. The use of raw materials from tropical solid wood waste in the Amazon region contributes to the reduction of carbon emissions associated with the burning of this material. In this context, this study aimed to cluster species based on the bonding properties of Amazonian woods by applying multivariate analysis. The apparent density 12% and strength of finger joint and edge-glued joints of Cedrela odorata, Enterolobium schomburgkii, Erisma uncinatum and Qualea paraensis was evaluated which were joined in homogeneous and hybrid configurations with the adhesives PVA and EPI, as spreading rate of 180 g/m2. The treatments were compared by multivariate analysis of variance and discriminant analysis. The discrimination of species and combinations based on wood density (low, medium, and high) revealed that this is the most important characteristic for grouping different species that make up tropical hardwood waste for the production of EGP panels. In practice, the separation of species into groups according to wood densities can contribute to a better definition of the indications for use of edge glued panels of each density class, and assertive targeting for applications according to the strength ranges required. In the static bending, parallel tensile and shear tests all species and their combinations met the minimum requirements normative, indicating the approval of species and combinations studied for the production of EGP panels.

Development of Self-Powered Prosthetic Finger with Pneumatic Passive Joints for Distal Interphalangeal Joint Amputees

Myoelectric prosthetic hands and fingers with grasping functions have challenges such as weight, cost, and grasping performance of flexible objects owing to the use of electric actuators. To resolve these problems, we propose a self-powered movable prosthetic finger using pneumatic pressure. This prosthetic finger utilizes the flexion/extension of the remaining finger of the user to drive a wire and flex or extend the finger joints. The use of a tendon (wire) and belt drives reduces the space occupied by the prosthetic finger unit compared with conventional linked prosthetic fingers. Furthermore, a sealed-air bellows is used for the joint for flexible grasping owing to passive variable-compliance and damping, which is impossible with only a tendon drive. These features have resulted in the stable grasping of various objects that are difficult to grasp using prosthetic fingers based on conventional technologies.

Surgical correction of posttraumatic triphalangeal joint flexion contractures of the fingers (systematic literature review)

Introduction Triphalangeal joint flexion contracture of the fingers is a common and challeging posttraumatic hand condition. The goal of surgical treatment is to correct finger deformity and increase interphalangeal range of motion.The objective was to systematize data on the causes of post-traumatic triphalangeal joint flexion contracture of the fingers and methods of surgical correction.Material and methods The original literature search was conducted on key resources including Scientific Electronic Library (www.elibrary.ru), the National Library of Medicine (www.pubmed.org), ScienceDirect, Google Scholar, Ovid databases according to PRISMA recommendations. Literature searches included both Russian and English studies, with one or more cases of post-traumatic triphalangeal joint flexion contracture of the fingers with the deformity surgically corrected. Cases of non-traumatic flexion contractures were excluded. Etiological factors of flexion contractures, heterogeneity of definitions and methods for recording the range of motion in the joint, anatomical features, surgical correction of flexion contractures and postoperative complications were reviewed.Results Common causes of flexion contractures included burns (32.3 %), dislocations and fracturedislocations of the finger joints (23.5 %). The median postoperative follow-up period was 13.5 months after surgical treatment. Surgical correction was produced with external fixation device (EFD) in 40 % of cases, open procedures performed in 50 % and a combined technique employed in one case (10 %). Based on calculations of the odds ratios of postoperative complications, a weak positive linear relationship was revealed between EFD and pain syndrome, and a weak negative linear relationship was observed between the open procedure and pain.Discussion There is heterogeneity of approaches regarding methods for correcting flexion contractures, surgical approaches, techniques for mobilizing joints and releasing the anatomical structures of the finger with open procedures, the distraction rate with EFD, methods for repair of soft tissue defects following the treatment of flexion contractures of interphalangeal joint of a finger.Conclusion Open procedures are commonly used for precise elimination of all components of flexion contracture of the joint and repair of soft tissue defects of the finger. A weak positive linear relationship was revealed between EF and pain syndrome. There was no significant correlation between open techniques and complications. There were no correlations between the treatment method and the contracture type; there are no treatment regimens for patients with this pathology.

Tensile and Bending Strength of Birch and Beech Lamellas Finger Jointed with Conventional and Newly Developed Finger-Joint Profiles.

In this study, the tensile and bending strength of birch and beech lamellas finger jointed with conventional (Standard) and newly developed finger-joint profiles (New) are presented. Polyurethane (PUR), Melamine-Urea-Formaldehyde (MUF) and Phenol-Resorcinol-Formaldehyde (PRF) adhesive systems were used to bond the finger joints. The objective of the New profiles was to reduce the stress concentrations within the finger joint by cutting the cross-grooved fingers perpendicular to the main orientation of the finger-joint profile. In the first trials of the development, larger cross-grooved fingers were cut with the aim to improve the stress distribution and to reinforce the finger joint by filling gaps in the finger joint with adhesive. As the study progressed, initial optimisations of the New profile were made. Smaller cross-grooved fingers were cut as it was assumed that they are beneficial for the manufacturing and integrity of the New profile. In combination with the MUF adhesive system, the New profile achieved the highest increase in the bending and tensile strengths compared to the Standard profile. In addition to the increased strength, other advantages such as reduced cracking in the finger joint were observed when using the New profile. The high strength and stiffness of hardwoods or other high-performance materials used in timber construction can probably be better exploited in combination with the New profile. Further tests will be carried out by considering different configurations of the New profile and different materials.

Multimodal, Ultrasensitive, and Biomimetic Electronic Skin Based on Gradient Micro‐Frustum Ionogel for Imaginary Keyboard and Haptic Cognition

AbstractElectronic skins (E‐skins) are poised to revolutionize human interaction not only with one another but also with machines, electronics, and surrounding environment. However, the wearable E‐skin that simultaneously offers multiple sensing capabilities, high sensitivity, and broad sensing ranges remains a great challenge. Here, drawing inspiration from human haptic perception, a multimodal, ultrasensitive, and biomimetic E‐skin (MES) founded on micro‐frustum ionogel is developed based on iontronic capacitive and triboelectric effects for imaginary keyboard and multifunctional haptic cognition. Leveraging simultaneously the ionogel as capacitive layer and triboelectric layer, the MES enables human‐dermis perception performances of high sensitivity (357.56 kPa−1), low limit of detection (0.47 Pa), and broad linear detection range (0–500 kPa). Moreover, human finger joint movements can be precisely monitored by the attached MES and be transferred into accurate typed letter information on an imaginary keyboard. More importantly, by harnessing signal acquisition/processing circuits and machine learning, the real‐time haptic cognition of different materials, surface roughness, and contact pressure can be achieved by the MES, which endows the advancement of interaction between next‐generation intelligent robot and physical environment. Consequently, the proposed MES demonstrates impressive potentials in the fields of wearable electronics, human–machine interaction (HMI), and Artificial Intelligence (AI).

Numerical and Experimental Study of a Wearable Exo-Glove for Telerehabilitation Application Using Shape Memory Alloy Actuators

Hand paralysis, caused by conditions such as spinal cord injuries, strokes, and arthritis, significantly hinders daily activities. Wearable exo-gloves and telerehabilitation offer effective hand training solutions to aid the recovery process. This study presents the development of lightweight wearable exo-gloves designed for finger telerehabilitation. The prototype uses NiTi shape memory alloy (SMA) actuators to control five fingers. Specialized end effectors target the metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints, mimicking human finger tendon actions. A variable structure controller, managed through a web-based Human–Machine Interface (HMI), allows remote adjustments. Thermal behavior, dynamics, and overall performance were modeled in MATLAB Simulink, with experimental validation confirming the model’s efficacy. The phase transformation characteristics of NiTi shape memory wire were studied using the Souza–Auricchio model within COMSOL Multiphysics 6.2 software. Comparing the simulation to trial data showed an average error of 2.76°. The range of motion for the MCP, PIP, and DIP joints was 21°, 65°, and 60.3°, respectively. Additionally, a minimum torque of 0.2 Nm at each finger joint was observed, which is sufficient to overcome resistance and meet the torque requirements. Results demonstrate that integrating SMA actuators with telerehabilitation addresses the need for compact and efficient wearable devices, potentially improving patient outcomes through remote therapy.

A multimodal multistream multilevel fusion network for finger joint angle estimation with hybrid sEMG and FMG sensing

Finger joint angle (FJA) estimation, as a dynamic and fine-grained decoding mode, can support intuitive and natural human–machine interactions. This study is pioneering work dedicated to achieving accurate and clinically friendly FJA estimation. In this context, a novel surface electromyography and force myography-based multimodal multistream multilevel fusion network (MMMFNet) is proposed. MMMFNet utilises gate-recurrent units (GRU) networks to capture spatial dependencies among features and adopts a multilevel fusion strategy to extract more comprehensive representations from information sources than a single-level fusion. A cross-stream interaction (CSI) block is added between the GRU networks to focus on important information in the prediction and optimise the learning process and representation capability by facilitating information interaction among branch networks. The experimental results suggest that the MMMFNet has higher estimation accuracy (RMSE: 6.225±0.276 vs. 6.953±0.282, R2: 0.879±0.019 vs 0.846±0.021), shorter training time (4.146±0.074 min vs. 16.536±0.430 min), and lower computational complexity (5.4×106 FLOPs vs 8.8×106 FLOPs) than state-of-the-art fusion methods. Moreover, MMMFNet, which quantifies feature importance using attention weights, is the first explainable multimodal model for hand movement intention decoding. In summary, compared with state-of-the-art methods, MMMFNet can not only estimate FJAs more accurately but is also more clinically friendly.

Fingers and finger joints - recording of small findings

Fingers and finger joints - recording of small findings

ThermoGrasp: Enabling Localized Thermal Feedback on Fingers for Precision Grasps in Virtual Reality

The increasing interest in thermal haptic feedback devices, particularly for virtual reality (VR) applications, highlights the need for more immersive user experiences. However, replicating precise thermal sensations on the fingers remains challenging due to the complexity of finger joints and movements. In this paper, we introduce ThermoGrasp, a novel thermal display designed to enhance VR experiences by providing realistic thermal feedback during precision object grasping. ThermoGrasp is a modular wearable device that targets controlled thermal feedback on the distal phalanges. The implications of designing its VR application were assessed through two experimental studies. The first study focused on the device's ability to accurately convey thermal sensations across different fingers during various precision grasps. The second study investigated the overall haptic experience in VR, examining the impact of thermal feedback on user immersion and realism during interactions with objects of varying temperatures. Participants' subjective responses were analyzed based on factors such as autotelicity, expressiveness, immersion, realism, and harmony. The findings indicate that precise, localized thermal feedback significantly enhances the VR experience, offering a marked improvement over traditional haptic feedback methods.

Automated Deep Learning-Based Finger Joint Segmentation in 3-D Ultrasound Images With Limited Dataset.

Ultrasound imaging has shown promise in assessing synovium inflammation associated early stages of rheumatoid arthritis (RA). The precise identification of the synovium and the quantification of inflammation-specific imaging biomarkers is a crucial aspect of accurately quantifying and grading RA. In this study, a deep learning-based approach is presented that automates the segmentation of the synovium in ultrasound images of finger joints affected by RA. Two convolutional neural network architectures for image segmentation were trained and validated in a limited number of 2-D images, extracted from N = 18 3-D ultrasound volumes acquired from N = 9 RA patients, with sparse ground truth annotations of the synovium. Various augmentation strategies were employed to enhance the diversity and size of the training dataset. The utilization of geometric and noise augmentation transforms resulted in the highest dice score (0.768 0.040, N = 6), as determined via six-fold cross-validation. In addition, the segmentation model is used to generate dense 3-D segmentation maps in the ultrasound volumes, based on the available sparse annotations. The developed technique shows promise in facilitating more efficient and standardized workflow for RA screening using ultrasound imaging.

Ergonomic glove pattern drafting method for hand assistive devices: considering 3D hand dimensions and finger mobility

Recently, interest has surged in glove-type assistive devices for relieving hand muscle stiffness caused by brain lesions. This study aims to develop an ergonomic method for drafting glove patterns intended for hand-assistive devices. To facilitate pattern development, we acquired three-dimensional (3D) scan data from the four hemiplegic patients while their hands were in a relaxed posture, which was subsequently transformed into two-dimensional (2D) data. Based on the 3D shape data, we analyzed the finger joint range of motion (ROM) and change ratio of skin surface length resulting from flexion and extension movements of the paralyzed hand. Incisions were strategically applied to regions displaying significant variations in these parameters. These flattened 2D patterns were then integrated into revised pattern blocks to enhance the shading data related to the 3D shape, resulting in the development of four glove patterns. We found that gloves prototyped using this innovative pattern-drafting method did not impede joint ROM when worn. Changes in clothing pressure inside the glove at the joints corresponded to the bending angles of the fingers, and the pressure did not exceed the discomfort threshold during hand flexion and extension movements. Importantly, participants provided positive subjective feedback concerning the comfort of the gloves. Our findings yield fundamental data for developing a foundational glove design for hand-assisted devices for patients with paralysis, achieved through the utilization of this novel ergonomic glove pattern-drafting method.

Passive Realization of Object Spatial Compliance by a Hand Having Multiple Four-Joint Hard Fingers

Abstract This paper presents an approach to passively realize any specified object spatial compliance using the grasp of a robotic hand. The kinematically anthropomorphic hands considered have multiple 4-joint fingers making hard point contact with the held object, and the joints of each finger have selectable passive elastic behavior. It is shown that the space of passively realizable compliances is restricted by the kinematic structure of the anthropomorphic hand. To achieve an arbitrary compliant behavior, fingers must be able to adjust their orientation. Synthesis procedures for grasps having 3, 4, and 5 or more fingers are developed. These procedures identify the finger configurations and the individual finger joint compliances needed to passively achieve any specified spatial object compliance matrix in the 20-dimensional subspace of grasp-realizable behaviors.

Finger Multi-Joint Trajectory Measurement and Kinematics Analysis Based on Machine Vision

A method for measuring multi-joint finger trajectories is proposed using MediaPipe. In this method, a high-speed camera is used to record finger movements. Subsequently, the recorded finger movement data are input into MediaPipe, where the system automatically extracts the coordinate data of the key points in the finger movements. From this, we obtain data pertaining to the trajectory of the finger movements. In order to verify the accuracy and effectiveness of this experimental method, we compared it with the DH method and the Artificial keypoint alignment method in terms of metrics such as MAPE (Mean Absolute Percentage Error), maximum distance error, and the time taken to process 500 images. The results demonstrated that our method can detect multiple finger joints in a natural, efficient, and accurate manner. Then, we measured posture for three selected hand movements. We determined the position coordinates of the joints and calculated the angular acceleration of the joint rotation. We observed that the angular acceleration can fluctuate significantly over a very short period of time (less than 100 ms), in some cases increasing to more than ten times the initial acceleration. This finding underscores the complexity of finger joint movements. This study can provide support and reference for the design of finger rehabilitation robots and dexterous hands.

Patterns of osteoarthritis in long finger joints: an observational cadaveric study with potential biomechanical considerations

PurposeTo explore the distribution and prevalence of osteoarthritis in metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints in long fingers in a cadaveric study, and to discuss potential biomechanical influences on these patterns. MethodsThis cadaveric study evaluated 144 metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints from 12 embalmed cadaver hands. A dorsal dissection approach was used to expose the joints, which were then marked with color-coded pegs for consistent orientation during imaging. High-resolution digital images of the distal articular surfaces were captured for analysis. The images were analyzed using custom software to quantify osteoarthritic areas, distinguishing between radial and ulnar aspects. Percentage affected joint surface was calculated using pixel-based measurements. Statistical analysis was used the Student t-test and ANOVA, with the significance threshold set at p < 0.05 and 95% confidence intervals ResultsThe ulnar side of the proximal interphalangeal joint in digits 2 and 3 showed higher prevalence of osteoarthritis (59.31% ± 15.48%) than the radial side (40.68% ± 15.48%), p = 0.007; in contrast, for digits 4 and 5, prevalence was greater on the radial (54.3% ± 10.99%) than the ulnar side (45.7% ± 10.99%), p = 0.007. No significant differences were noted in osteoarthritis distribution between the radial and ulnar aspects of the metacarpophalangeal and distal interphalangeal joints. ConclusionsThis study identified distinct patterns of osteoarthritis distribution in long-finger joints, with greater prevalence in the proximal interphalangeal joints. Although there were differences between stable (digits 2 and 3) and mobile (digits 4 and 5) fingers, further research is necessary to conclusively determine the role of biomechanical forces in the development of osteoarthritis. These findings lay the groundwork for future studies of the pathophysiology of osteoarthritis in the hand, and could guide the development of preventive and therapeutic interventions.

Theoretical and experimental studies on the bending properties of glued laminated timber manufactured with Chinese fir

China has been increasingly promoting the use of prefabricated timber structure buildings in recent years. However, unlike other countries, China lacks a diverse range of local tree species and engineered wood products suitable for load-bearing components in timber structures. This shortage poses a risk to the sustainable development of timber structures in China. This issue is addressed in this study, which focuses on the development and manufacture of glued laminated timber (GLT) using Chinese fir from plantation forests. The dynamic elastic modulus of 549 laminae was evaluated using the FAKOPP stress wave approach. A total of 28 laminae were randomly selected from Classes I, II, and III to assess the influence of stress grading on bending performance. This study included an analysis of failure modes, bending capacity, and the prediction model for bending stiffness of GLT with different layups and cross-sectional heights. The findings showed that the dynamic elastic modulus of the laminae followed a normal distribution. The bending strength and modulus of elasticity of finger-jointed laminae across different grades were 29.59 MPa to 37.05 MPa and 8.13 GPa to 10.94 GPa, respectively. The mechanical properties of both same-grade and mixed-grade composition GLT manufactured from Chinese fir met the TCT28 (MOR≥28 MPa, MOE≥8000 MPa) and TCYD24 (MOR ≥ 24 MPa, MOE ≥ 8000 MPa) garde requirements in GB/T26889, respectively. Failure modes in the GLT specimens typically began at the knots or finger joints of the bottom layer laminae. The cross-sectional height had no significant effect on the modulus of elasticity of GLT but exerted a significant effect on bending strength. The prediction model for bending stiffness, developed using the transformed section method, agreed with the experimental results. The outcome of this research provides a scientific and data-driven foundation for the application of Chinese fir in the field of structural materials.