Search Results (890)

Wearable data gloves often suffer from electromagnetic interference, insufficient substrate stability, and limited capability for multi-degree-of-freedom motion measurement. To address these limitations, a flexible glove incorporating a hybrid POF-FBG sensing scheme was designed and fabricated. Plastic optical fibers (POFs) were side-polished and patterned with long-period gratings to improve sensitivity to wrist flexion-extension and abduction-adduction. Then fiber Bragg gratings (FBGs) were embedded in a polydimethylsiloxane substrate and encapsulated using thermoplastic polyurethane fixtures to reduce the influence of skin stretching and improve measurement accuracy of finger-joint angle. Moreover, a thermoplastic polyurethane skeleton with an adaptive sliding-rail structure was 3D printed to maintain the stability of the sensor placement at the joints. Experimental results demonstrated the mean absolute errors of 4.06°, 1.38° and 1.70° for wrist flexion-extension, abduction-adduction and finger-joint bending, respectively, along with excellent gesture classification using a support vector machine algorithm, which indicates great potential in virtual reality interaction and hand rehabilitation applications. Full article

Patellar maltracking is among the most common causes of anterior knee pain after total knee arthroplasty (TKA), underscoring the need for accurate prevention and treatment. Therefore, the purpose of this narrative review is to provide a comprehensive overview of current evidence on post-TKA tracking, focusing on component alignment, preoperative patient assessment, and revision treatment options. A PubMed database search was performed, leveraging the literature from the last 20 years, and the results were qualitatively synthesized. According to current studies, several precautions should be taken to prevent patellofemoral stress and, consequently, patellar maltracking, such as avoiding internal rotation, valgus alignment, and excessive flexion of the femoral component and internal rotation of the tibial component. Regarding alignment strategies, kinematic alignment appears to offer potential benefits over mechanical alignment in certain functional outcomes and patient satisfaction scores. However, these differences should be interpreted cautiously as they may not always exceed the minimal clinically important difference. Furthermore, recent evidence indicates that quadriceps biomechanics influence TKA outcomes, potentially suggesting that conventional surgical approaches may need to be individualized, though these preliminary findings require prospective validation. Currently, robotic-assisted surgery represents a developmental direction for patient-tailored interventions and offers great promise for better prosthesis customization to the individual patient. Integration of imaging data with dynamic soft-tissue assessment enables more predictable reconstruction of joint kinematics. Regarding surgical treatment, the selection of specific methods requires a prior clinical and radiographic assessment. Indications range from patellar maltracking direction and component malrotation to patient preferences and rehabilitation potential. Ultimately, the future of TKA relies on personalized interventions to prevent complications and improve patient outcomes. This evolution is driven by the shift from mechanical alignment to kinematic alignment, alongside quadriceps tendon assessment and intraoperative robotic-assisted measurement, all aimed at optimizing the accuracy of implant positioning. Full article

Brain–machine interfaces (BMIs) aim to decode motor intentions from neural activity to enable direct control of external devices. However, most existing decoders rely on monolithic architectures that fail to capture the distinct neural representations of different joint movement directions, limiting their generalizability. In this work, we propose a Single-Direction CNN-LSTM decoder inspired by motor cortex encoding mechanisms, which separately models extension and flexion dynamics through parallel CNN-LSTM branches. Each branch extracts spatial–temporal features from neural spike data and predicts directional joint variables, which are then combined by subtraction to yield the net angular velocity and torque of upper-limb joints. Using invasive recordings from a macaque during a 2D center-out reaching task, we demonstrate that our decoder achieves comparable performance to a conventional CNN-LSTM when trained on all tasks, while significantly outperforming both CNN-LSTM and linear regression baselines in cross-target generalization scenarios. Moreover, the model can capture physiologically meaningful co-contraction patterns, providing richer insights into motor control. These results suggest that incorporating neuroscience-inspired modular decoding into deep neural architectures enhances robustness and adaptability across tasks, offering a promising pathway for BMI applications in prosthetics and rehabilitation. Full article

Understanding knee kinematics during gait is essential for the design of prostheses, orthoses, and biomimetic mechanisms. In many biomechanical analyses, tibiofemoral motion is simplified to the sagittal plane, allowing the locus of the instantaneous center of rotation (ICR) to describe joint kinematics derived from the instantaneous axis of rotation (IAR). However, it remains unclear whether ICR trajectories obtained from simplified flexion–extension tasks can represent those observed during gait. This study analyzes the sagittal-plane trajectory of the tibiofemoral ICR during gait swing, standing swing, seated swing, and squat. Motion data from 21 healthy participants were captured using videogrammetry, and the instantaneous axis of rotation (IAR) was computed from homogeneous transformation matrices using the Mozzi–Chasles theorem. Sagittal-plane ICR trajectories were derived and compared within subjects across tasks. Significant differences were found between gait and all other movements in both trajectory shape and spatial position. The shape metric (S), which quantifies differences in trajectory geometry, showed mean values ranging from 0.82 to 1.04 with very large effect sizes (Cohen’s d = 2.90 to 4.47, p < 0.0001). The centroid distance metric (M), which measures the overall spatial displacement between trajectories, indicated positional differences ranging from 8.15 mm to 12.37 mm between trajectories also showing very large effect sizes (Cohen’s = 1.72–3.40, p < 0.0001). Additionally, the mean deviation of the IAR from the sagittal plane ranged from 14° to 18° during gait, whereas smaller deviations were observed in non–weight-bearing swing movements. These results demonstrate that tibiofemoral ICR trajectories are task-dependent and that simplified flexion–extension tasks do not fully reproduce the knee kinematics observed during gait. Consequently, the use of gait-derived ICR trajectories, together with their variability, provides a more suitable basis for the design and optimization of polycentric mechanisms, enabling the development of devices that more closely replicate real biomechanics and are potentially better adapted to the user. Full article

Background: Acute posterior cruciate ligament (PCL) injuries are uncommon and often challenging to treat. While conservative treatment is frequently proposed in the acute phase, conventional rigid bracing may lead to complications such as joint stiffness and quadriceps atrophy. Dynamic braces applying posterior to anterior force during flexion have been proposed as a more functional alternative. Purpose: To evaluate the biomechanical efficacy of a dynamic PCL brace in reducing posterior tibial translation during the acute post-traumatic phase using standardized stress radiographs. Methods: The study was conducted on 11 patients with acute PCL injuries (four isolated, seven multiligamentous) treated within 15 days from trauma. Posterior tibial translation was measured with X-rays at 90° of flexion under four conditions: static (resting), stress (150 N), brace unloaded, and brace loaded (50 N posterior force). Three blinded orthopedic surgeons performed all measurements independently. Results: The dynamic brace significantly reduced posterior tibial translation across all conditions. Translation under stress was reduced from a mean of 7.1 mm to 2.68 mm with the loaded brace (p < 0.001). Conclusions: The study demonstrates that dynamic bracing provides effective biomechanical control of posterior tibial translation in the acute PCL injury. These findings support the potential role of dynamic bracing in conservative treatment protocols. Full article

This study compared the kinematic and neuromuscular characteristics of the tennis forehand drive between high-performance (HP) and intermediate (INT) players. Eighteen right-handed male players (HP: n = 9; INT: n = 9) performed cross-court forehands while three-dimensional motion capture and surface electromyography (EMG) were recorded from the dominant upper limb and trunk. Kinematic and EMG data were time-normalized to the forward swing. One-dimensional statistical parametric mapping two-sample t-tests were used to compare joint angles, angular and linear velocities, and EMG amplitude waveforms between groups. Bonferroni-corrected significance levels were set at α = 0.0017 for kinematic variables and α = 0.0063 for EMG data. HP players exhibited greater racket linear velocity during the final part of the forward swing, accompanied by higher shoulder, elbow and wrist linear velocities, whereas hip linear velocity did not differ between groups. Joint angles were broadly similar, with SPM revealing only slightly greater early knee flexion in HP players. In contrast, HP players showed higher hip and knee angular velocities and greater wrist angular velocities in both flexion/extension and radial/ulnar deviation towards impact. EMG patterns were generally comparable, but HP players displayed higher biceps brachii activation in two significant clusters during the mid-to-late forward swing and greater triceps brachii activation in the late forward swing. No significant differences were observed for deltoid, pectoralis major, latissimus dorsi, flexor carpi radialis or extensor carpi radialis. These findings indicate that superior forehand performance in HP players is associated primarily with refined segmental coordination, greater lower-limb and distal segment velocities, and locally increased elbow muscle activation, rather than with widespread increases in upper-limb or trunk muscle activity. Full article

Background: Surgical management of adult patients with post-dysplastic coxarthrosis using total hip arthroplasty is technically demanding and carries an increased risk of complications. In cases of high iliac dislocation classified as Crowe type IV, restoring the acetabular component to the anatomical hip centre often requires femoral shortening osteotomy to enable safe reduction in the prosthetic joint. Nevertheless, long-term evidence on functional outcomes and prosthesis survival with this approach is limited. Methods: A retrospective cohort study included 19 patients with 22 cases of Crowe type IV post-dysplastic hip osteoarthritis treated with uncemented total hip arthroplasty (Pinnacle/S-ROM, DePuy, Warsaw, IN, USA) combined with transverse subtrochanteric femoral shortening osteotomy. Patients underwent serial clinical follow-up, including assessment of range of motion, measurement of limb-length discrepancy, and functional evaluation using the Harris Hip Score and the WOMAC questionnaire. Radiological assessment included evaluation of osteotomy union, implant positioning, and osteolysis on standardized radiographs. Vertical distances of the centre of rotation (CR), the tip of the greater trochanter (GT), and the tip of the lesser trochanter (LT) from both reference lines were measured bilaterally, and inter-side differences were calculated. The reference lines consisted of the line connecting the inferior margins of the ischial bones and the teardrop (TD) line. Results: All osteotomies united at a mean of 5.57 months, with a mean follow-up of 129 months. Mean limb-length discrepancy decreased from 5.27 cm to 1.5 cm, and mean hip flexion improved from 82.9° to 106°. Functional outcomes improved significantly, with mean WOMAC increasing from 55.4 to 80.1 (p < 0.001) and mean Harris Hip Score from 49.8 to 84.66 at up to 3 years of follow-up (p < 0.001). Osteotomy length correlated strongly with lesser trochanter–teardrop distance (p = 0.00000048). Complications included distal femoral fissure (27.3%) and revision (18%), with no infection or permanent neurological deficit. Conclusions: Total hip arthroplasty combined with subtrochanteric femoral shortening osteotomy for Crowe type IV post-dysplastic hip osteoarthritis appears to be a feasible and effective procedure in an experienced centre, providing reliable osteotomy healing and significant early functional improvement that is sustained over time. Limb-length discrepancy was reduced and satisfactory biomechanical restoration was achieved, with an acceptable complication profile and implant survival of 81.3% at long-term follow-up. The LT–TD parameter was identified as a potential predictor of osteotomy length, enabling the proposal of a preoperative planning equation. However, given the limited sample size and lack of validation, these findings should be interpreted cautiously. Further studies are needed to confirm their broader applicability. Full article

Background: Supported standing is widely used in children and adolescents with severe cerebral palsy (CP) as part of rehabilitation programs aimed at maintaining musculoskeletal health and enabling participation. Despite its frequent clinical use, quantitative biomechanical evidence describing knee joint loading under different positioning conditions remains limited, particularly in individuals classified as GMFCS IV–V. The primary objective of this study was to quantify knee joint loading during supported standing across predefined combinations of verticalization angle and hip/knee flexion. The secondary objective was to investigate interaction effects between these variables and to assess whether increasing hip/knee flexion is associated with a linear reduction in knee joint loading. Methods: Twenty-six children and adolescents with CP (GMFCS IV–V; age 6–17 years) participated in the study. Measurements were performed using a standardized back-supported standing device. Knee joint loading was measured using integrated pressure sensors across six verticalization angles (0°, 30°, 45°, 60°, 75°, 90°) combined with four hip/knee flexion angles (0°, 15°, 30°, 45°). Forces were normalized to body weight (%BW). Statistical analysis was performed using repeated-measures analysis of variance. Results: Knee joint loading increased consistently with greater verticalization across all tested hip/knee flexion conditions (p < 0.001). A non-linear pattern was observed across flexion angles. Interaction effects between verticalization and hip/knee flexion were observed. Knee joint loading did not decrease linearly with increasing flexion; instead, the lowest loading was observed at approximately 15° hip/knee flexion, whereas both full extension and 45° flexion resulted in higher loads. Conclusions: Verticalization angle represents a key factor influencing knee joint loading during supported standing in children and adolescents with severe CP. Knee joint loading increases with greater verticalization, while hip/knee position shows a non-linear influence. The absence of a linear reduction in loading with increasing flexion highlights the presence of interaction effects between positioning variables and supports individualized positioning strategies in supported standing programs. Full article

To investigate how knee joint protector design affects the biomechanical characteristics of knee motion under various activities, this pilot study (n = 5) examined how knee joint protector design modulates knee biomechanics across walking, jogging, squatting, and sit-to-stand tasks using optical motion capture and AnyBody musculoskeletal modeling (FullBody_GRFPrediction). We quantified knee flexion kinematics, model-estimated joint reaction forces and moments, and model-estimated muscle activity of eight lower-limb muscles under four conditions with different levels of structural constraint: no protector (Pro.off), a conventional sleeve-type protector (Pro.a), a segmented support protector (Pro.b), and a wrapping fixation protector (Pro.c). The biomechanical protective performance of the knee joint protector was task- and phase-dependent. The results showed that Pro.a optimized muscle activation. Pro.b increased sagittal-plane design but increased joint loading and muscle activity. Pro.c induced noticeable distal compensation along the kinetic chain. The findings revealed that protector effects were task-dependent. Dynamic tasks mainly affected coronal-plane stability parameters, whereas quasi-static tasks more clearly altered sagittal load distribution. In this study, biomechanical protective performance is defined as reduced knee joint loading without disproportionate increases in model-estimated muscle activity or excessive loss of functional knee flexion range. Under this definition, greater structural constraint did not consistently produce a more favorable biomechanical profile. These results provide a feasibility baseline for task-specific protector evaluation and motivate confirmatory studies with larger cohorts and experimental validation. This study provides theoretical and methodological insights to guide future design and optimization of knee joint protectors. Full article

(1) Background: Gait analysis provides quantitative information on walking patterns and has proven invaluable for assessing motor function in rehabilitation programmes. A markerless motion capture system combining computer vision techniques provides low-cost, real-time, portable gait analysis. (2) Methods: The kinematics of the knee and ankle of twenty-seven healthy volunteers were assessed using a single smartphone camera combined with the MediaPipe human pose estimation framework. The system was validated using the OPAL wearable sensor system by APDM Wearable Technologies. (3) Results: Findings showed close correspondence between the two systems for knee kinematics showing a mean absolute error of 4.10° ± 2.32° and 3.15° ± 3.10° for right and left knee flexion, respectively, and a mean absolute error of 2.30° ± 2.01° and 3.12° ± 2.63° for right and left knee extension, respectively. The mean absolute error for right and left knee range of motion was found to be 4.55° ± 3.12° and 4.15° ± 3.01°, respectively. Moreover, Bland–Altman plots indicated minimal bias (average 0.6 for flexion, average 0.47 for the extension, and 0.30 for the range of motion) and excellent correlation for knee flexion bilaterally (0.916 and 0.845 for the right and left side, respectively), with slightly lower but still satisfactory agreement for knee extension (0.862 and 0.845 for the right and left side, respectively). Conversely, ankle measurements revealed poor concordance: dorsiflexion and range of motion presented significant differences and systematic errors, while plantarflexion showed no statistical difference but weak correlation. (4) Conclusions: This study demonstrated that combining a smartphone camera with a human pose estimation framework allows for low-cost, real-time, portable gait analysis, particularly of the knee joint. Full article

Background: Wrist–forearm orthoses used during self-feeding may alter scapular and shoulder mechanics and increase proximal load, but this has not been quantified. Methods: Seventeen right-hand-dominant young adults performed a spoon-feeding task under free and restricted conditions. A thermoplastic wrist–forearm orthosis positioned the wrist at approximately 30° dorsiflexion at rest and was intended to constrain wrist motion during the task without rigidly immobilizing forearm pronation–supination. Three-dimensional kinematics (scapula, shoulder, trunk, and distal joints) were recorded using inertial sensors, and surface electromyography was obtained from the upper trapezius, middle deltoid, and biceps brachii. Maximum joint angles and mean %MVC over the feeding cycle were compared between conditions (α = 0.05). Results: The restriction condition resulted in a more anteriorly tilted and downwardly rotated scapular posture, greater shoulder abduction and external rotation, and increased thoracic flexion, whereas maximum distal joint angles did not differ, suggesting a functional distal constraint rather than rigid immobilization. Middle deltoid and biceps brachii activities increased significantly, with a nonsignificant trend toward higher upper trapezius activation. Conclusions: In healthy young adults, limited wrist motion and forearm rotation during spoon-feeding were associated with altered proximal coordination, including scapular, shoulder/trunk, and proximal muscle changes. Full article

(1) Achilles tendon rupture is one of the most severe lower-limb injuries, frequently occurring during movements involving maximal dorsiflexion with the knee at near-full extension. Preventive strategies are crucial, particularly for athletes engaged in high-risk sports such as basketball. (2) In this work, we examined the effect of a novel Achilles brace on Achilles tendon loading during concentric and eccentric mechanisms associated with tendon rupture. (3) Twenty-eight young basketball players performed tests under two conditions: with the adaptive brace and without it (control). Participants were divided into two groups (n = 14 in both). The first group assessed concentric Achilles loading by performing three plantar-flexor strength tests in three different joint configurations: maximal dorsiflexion with the knee flexed (FKF); injury mechanism position—full plantar flexion with the knee extended (FKE); and neutral ankle position with the knee extended (NKE). The number of maximal heel-raise repetitions performed before onset of fatigue was recorded. The second group assessed eccentric tendon loading by performing single-leg forced maximal-velocity dorsiflexion with the knee extended. In all tests, the time between maximal plantar flexion and maximal dorsiflexion, as well as the ankle range of motion, was analyzed using 2D video. Paired t-tests were used to compare braced and control conditions. In all tests, the ankle range of motion (ROM) did not differ significantly between brace and control conditions. Wearing the brace significantly improved plantar-flexor muscle strength only in the FKE test (31 ± 1.3 repetitions with brace vs. 21 ± 1.3 in control, p < 0.05). No significant differences were found for the FKF (27 ± 1.3 vs. 25 ± 1.3) or NKE (25 ± 1.3 vs. 24 ± 1.3) positions. During drop eccentric loading, wearing the brace resulted in a significantly slower transition time from plantar flexion to dorsiflexion (460 ± 60 ms with brace vs. 320 ± 30 ms in control, p < 0.001). (4) In brief, the novel Achilles brace was found to significantly reduces Achilles tendon load during both concentric and eccentric activities, but only in high-risk joint positions. These findings suggest that the brace provides mechanical protection, and may reduce the risk of Achilles tendon rupture, in athletes exposed to high tendon stress. Full article

Background: Adolescent idiopathic scoliosis (AIS) is often associated with central nervous system disorders and deficits in sensorimotor function. While the Schroth method is a common clinical intervention, research evidence regarding its effectiveness in enhancing sensorimotor control remains limited. This study aimed to evaluate the impact of the Schroth method on sensorimotor control and quality of life (QoL) in AIS patients. Methods: Sixty female participants (mean age 13.4 years) with Cobb angles between 10° and 45° were divided into an intervention group (n = 30), receiving Schroth exercises and bracing for 10 weeks, and a control group (n = 30), receiving bracing alone. Outcome measures included static and dynamic balance, spine lateral flexion joint position sense (JPS), upper-limb functional proprioception, and the GR-BSSQ Brace questionnaire. Results: Statistical analysis using two-way mixed ANOVA revealed significant Group × Time interactions across several parameters. The Schroth group showed significant improvements in static and dynamic balance, with ellipse area reduction (p = 0.005) and reduced Fukuda test distance (p = 0.007), respectively. Significant enhancements were noted in spine lateral flexion JPS (Bilateral p = 0.008) and upper-limb proprioception (Bilateral p = 0.000). Furthermore, the intervention group reported a significant improvement in QoL scores compared to the control (p = 0.000). Conclusions: The findings demonstrate that the Schroth method was associated with enhanced sensorimotor control, supporting its use as a targeted approach to improve functional outcomes in individuals with AIS. These results highlight the clinical value of the method, beyond spinal curve correction. Full article

Background: Knee osteoarthritis (KOA) is one of the leading causes of chronic pain and long-term disability worldwide. Despite its high prevalence, KOA remains underrepresented in repetitive peripheral magnetic stimulation (rPMS) research. While total knee arthroplasty remains the definitive treatment, there is a growing need for non-invasive approaches to reduce symptoms in patients seeking conservative alternatives or awaiting surgery. Methods: Thirty patients with KOA underwent a non-invasive treatment program consisting of eight sessions of double-coil repetitive peripheral magnetic stimulation (rPMS) over three weeks. Outcome measures included pain intensity assessed by the Visual Analog Scale (VAS), functional ability evaluated by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Timed Up and Go test (TUG), and joint mobility measured as knee flexion and extension. Clinical relevance was evaluated using the Minimal Clinically Important Difference (MCID), and subgroup analyses were performed according to Kellgren-Lawrence (KL) grade. Results: Double-coil rPMS was associated with statistically and clinically significant improvements in all outcomes. MCID responder rates exceeded 80% for VAS and TUG, exceeded 70% for WOMAC, and approached 50% for joint mobility outcomes. Subgroup analysis indicated that patients with lower KL grades experienced greater pain reduction, whereas those with higher grades showed greater functional gains. Conclusions: Double-coil rPMS provided preliminary evidence of potential clinical benefit as a non-invasive approach in patients with KOA. Given the single-arm pilot design, the findings should be interpreted cautiously and require confirmation in adequately powered randomized controlled trials with longer follow-up. Full article

Objective: The objective of this study was to explore the motion characteristics and movement strategies of the hip and knee joints in overweight individuals during sit-to-stand (STS) transfers using statistical parametric mapping (SPM). Methods: Twenty subjects were divided into an overweight group (n = 10) and a normal-weight group (n = 10) based on body mass index (BMI). The Qualisys infrared motion capture system and Kistler three-dimensional force platform were used for motion data collection, and Visual 3D and Matlab were used to calculate the angles and torque indicators of the lower limb hip and knee joints. Results: During the STS process, the maximum hip flexion angle of the overweight group was smaller than that of the control group (Z = −1.83, p = 0.043, r = 0.39), while the maximum abduction and external rotation angles were greater than those of the control group (Z = −2.15, p = 0.022, r = 0.46; Z = −2.02, p = 0.028, r = 0.48). SPM analysis showed that during the 0–52% phase of the hip joint in the frontal plane, the abduction amplitude of the overweight population was greater than that of the normal population (p < 0.05). The minimum external rotation angle of the knee joint was less than that of the control group (F(1,18) = 9.135, p = 0.043). The peak internal adduction and abduction torque of the hip joint in the overweight group was greater than that of the control group (Z = 2.37, p = 0.017, r = 0.54). Conclusions: Compared with the normal-weight population, the overweight population exhibited distinct motion characteristics of the hip and knee joints during the STS, with particularly pronounced differences in the hip joint. To maintain stability during STS, the overweight population adopts a compensatory movement strategy featuring a wider base of support via hip abduction and increased muscular torque to control frontal plane stability, which imposes greater functional loads on the hip joint. BMI-related movement characteristics should be studied in young adults under controlled experimental conditions, and future studies are needed to verify whether similar patterns exist in older adults. Full article