Search Results (40)

Background/Objectives: Considering that the kinematics of the temporomandibular joints (TMJs) is concomitant with head movements and that temporomandibular joint disorders (TMDs) are frequently associated with neck pain in clinics but seldom or never investigated, the aim of this study was to develop a reliable in vivo measurement protocol of the simultaneous amplitudes of the mandible and of the skull. The development of such a protocol is part of a project to build an accurate kinematic assessment tool for clinicians in the orofacial field who treat patients suffering from TMD. Methods: Mouth opening, laterotrusion and protrusion movements for three different positions of the head (neutral, slouched and military) on 12 asymptomatic voluntary subjects (5 men and 7 women, mean 33.6 yo +/− 11.1) were recorded using 20 markers palpated and taped and 14 optoelectronic cameras. The acquisition frequency was set at 150 hertz. The inter- and intra-examiner reliability of marker palpation in mm was calculated using standard deviation (SD), mean difference (MD) and standard error (SE). Amplitudes of movement according to axes defined by the International Society of Biomechanics (ISB) are given for the mandible and skull segments. The propagation of error on the amplitudes was calculated with the root mean square propagation error (RMSPE) in degrees. Repeated-measures ANOVA or Friedman tests were used to assess the influence of the position of the head on the amplitudes of the jaw. Power analysis of the sample size was estimated with Cohen’s f3 size effect test. Steady-state plots (SSPs) and normalized motion graphs between the skull and the mandible motion were performed to study the coordination of their maximum amplitude over time. Results: The protocol demonstrated good intra-examiner reliability (1.5 < MD < 5.8; 2.6 < SD < 7.8; 2.0 < SE < 3.8), good inter-examiner reproducibility (0.2 < MD < 4.0; 3.5 < SD < 4.6; 2.0 < SE < 2.5) and small error propagation (0.0 < RMSPE intra < 2.8; 0.0 < RMSPE inter < 1.0). The amplitudes of the jaw and head found during the three types of movements correspond to the values reported in the literature. Head positions did not appear to significantly influence the amplitudes of jaw movements, which could be explained by the power estimation of our sample (Type II error β = 0.692). The participation of head movements in those of the jaw, for all motions and in all positions, was demonstrated and discussed in detail. Conclusions: The accuracy, test–retest reliability, and intra-individual variability of the TMJ kinematic analysis, including head movements, was ensured. The small sample size and the absence of standardized head positions for the subjects limit the scope of the intra- and inter-group analysis results. Given the natural biological and complex coordination of jaw–head movement, the authors consider its evaluation useful in clinical intervention and would like to further develop the present protocol. The next step should be to test the feasibility of its clinical application with a larger group of asymptomatic subjects compared to patients suffering from TMD. Full article

Objective: The purpose of this study is to develop a mechatronic device capable of characterizing the kinematics of the knee joint, based on the acquisition and analysis of data focused on the knee joint point. Methods: A mechatronic device was designed using dimensional data from a participant’s lower limb (1.59 m, 57 kg), obtained through 3D scanning. The device, based on a proportional mechanism aligned with anatomical reference points, allows the evolution of the knee joint pivot point (PPKJ) to be recorded. Ten healthy subjects (aged 22–26 years, height 1.50–1.63 m, body mass 48–59 kg) were selected for testing. The device was placed on each knee to record joint trajectories during squats. The trajectories were classified into two groups: extension to flexion and flexion to extension. For each group, the average trajectory was calculated. Results: Forty PPKJ trajectories were obtained, divided into two sets: extension to flexion with a range of 8° to 51.3° and flexion to extension with a range of 6.7° to 56.83°, which allowed the mean trajectory and cubic polynomial regression to be calculated as the best approximation for characterizing the trajectory of the instantaneous center of rotation of the knee joint. Conclusions: The developed mechatronic device offers an accessible and non-invasive solution for recording the trajectory of the knee joint pivot point in individuals with characteristics like those in the study. This alternative approach could improve the representation of knee kinematics in the design of customized prostheses, exoskeletons, and rehabilitation devices for lower limbs. Full article

Background: The relationship between varus thrust (VT) during gait and static limb alignment on radiography in knee osteoarthritis (OA) remains unclear. Therefore, the present study investigated the association between the tibial inclination angle (TA), which was noninvasively measured from the body surface, and radiographic parameters. In Addition, this study analyzed how TA changes under different loading conditions (ΔTA) relate to VT acceleration (VTA) during early stance using an inertial measurement unit (IMU) sensor. Methods: Nineteen female patients (mean age: 63.5 ± 8.6 years) with knee OA or medial meniscus injury were included. The TA was defined as the angle between the tibial mechanical axis and a vertical line from the floor, which was measured in standardized standing and supine positions. The ΔTA was calculated as the difference between these positions. To assess lower limb alignment, the femorotibial angle (FTA) and joint line convergence angle (JLCA) were measured. The VTA was measured using IMU sensors on the thigh and tibia, and the differences between lateral and medial VTA were defined as femoral and tibial ΔVTA, respectively. Spearman’s correlation coefficient and linear regression were used for analysis. Results: The standing TA was significantly correlated with the FTA (ρ = 0.47, p = 0.04) and JLCA (ρ = 0.80, p < 0.01). The ΔTA was significantly associated with femoral ΔVTA (β = 0.70, p < 0.01) and tibial ΔVTA (β = 0.67, p < 0.01). Conclusions: Surface-measured TA reflects radiographic alignment. The ΔTA also captures dynamic instability not explained by static measures, suggesting its potential utility as an assessment indicator, although further validation is warranted. Full article

Background: Children with spastic hand impairments resulting from cerebral palsy or neuromuscular disorders often exhibit a restricted range of motion and diminished functional use. Rehabilitation devices that assist joint mobilization can enhance therapeutic outcomes, yet few solutions target pediatric populations. Methods: This study aimed to design, implement, and preliminarily evaluate a biomechanical device tailored to promote flexo-extension, radial–ulnar deviation, and supination movements in spastic hands of school-aged children. A prototype combining a motor-driven actuation system, adjustable wrist and finger supports, and a MATLAB-based graphical user interface was developed. Two participants (aged 8 and 10) with clinically diagnosed spastic hemiparesis underwent 25-minute sessions over 15 consecutive days. Joint angles were recorded before and after each session using an electro-goniometer. Data normality was assessed via the Shapiro–Wilk test, and pre–post differences were analyzed with the Wilcoxon signed-rank test (α = 0.05). Results: Both participants demonstrated consistent increases in their active range of motion across all measured planes. Median flexo-extension improved by 12.5° (p = 0.001), ulnar–radial deviation by 7.3° (p = 0.002), and supination by 9.1° (p = 0.001). No adverse events occurred, and device tolerance remained high throughout the intervention. Conclusions: The device facilitated statistically significant enhancements in joint mobility in a small pediatric cohort, supporting its feasibility and safety in spastic hand rehabilitation. These preliminary findings warrant larger controlled trials to confirm the device’s efficacy, optimize treatment protocols, and assess its long-term functional benefits. Full article

Background: Respiratory exercises play a key role in rehabilitation programs, especially for older adults and individuals with chronic pulmonary conditions. Despite growing interest in wearable sensors for home-based care, structured reference metrics to quantitatively characterize respiratory exercises are still limited. This study aimed to provide a quantitative characterization of respiratory exercises and evaluate the level of agreement between a low-cost prototypical sensor and a commercial one. Methods: Eleven older adults (9 females; age = 72.6 ± 5.0 years; height = 1.66 ± 0.09 m; mass = 68 ± 10 kg) performed a structured respiratory exercises protocol. Algorithms were developed to identify respiratory cycles, their execution time, and parameters related to respiratory capacity, using accelerometer signals from the two wearable sensors placed on the rib cage. Results: The average respiratory cycle duration ranged from 2.8 to 4.3 s, with normalized inspiratory and expiratory peaks. Tidal volume variability was minimal, confirming consistency in breathing patterns across exercises. User comfort was high (mean VAS = 8.7). Sensor comparison confirmed strong agreement between the two sensors in detecting respiratory cycles, though some variability was observed in timing and tidal volume estimation. Conclusions: These findings suggest that even simple accelerometers can reliably capture key respiratory parameters, supporting the feasibility of using wearable sensors to monitor structured respiratory exercises performed in home-based settings. Full article

Objectives: To quantify the effects of geared wheelchair wheels on energy expenditure during manual wheelchair propulsion in individuals with spinal cord injury (SCI). Methods: Eleven adult manual wheelchair users with SCI propelled their personal manual wheelchairs, which were equipped with a pair of geared wheels, on a passive wheelchair ergometer in low-gear and standard-gear conditions for six minutes. The energy cost of transport, distance traveled, rate of oxygen consumption (SCI MET), rate of perceived exertion, heart rate, and stroke cycle frequency were measured and compared across the gear conditions. Results: The distance traveled and SCI MET were significantly lower (p = 0.003) and cost of transport was significantly higher under the low-gear condition compared with the standard-gear condition. Gear condition exerted a moderate effect on the level of exertion; however, the decrease in the rate of perceived exertion under the low-gear condition was not statistically significant. Gear condition did not significantly affect heart rate and stroke cycle frequency. Conclusions: Geared manual wheelchair propulsion was significantly more energy-demanding, but less intense (easier) under the low-gear condition than the standard-gear condition. Using geared wheels may be beneficial for manual wheelchair users to independently accomplish strenuous propulsion tasks during typical activities of daily living, such as propulsion on carpeted floor. However, the small sample size and inclusion of only male participants limit the generalizability of these findings, and future studies with larger and more diverse cohorts are warranted. Full article

Limb amputation causes significant challenges for patients in achieving effective mobility and functionality through prosthetic limbs. The prosthetic socket plays a pivotal role in the success of rehabilitation. This review explores the current advancements in prosthetic socket design and fabrication, focusing on traditional techniques like casting and lamination, and emerging technologies such as 3D printing and computer-aided design (CAD). By comparing these methods, this review highlights the advantages, limitations, and suitability for different clinical needs. This article discusses the importance of pressure distribution in socket design, emphasizing the need to relieve pressure in sensitive areas to prevent skin complications. It also examines the materials used in socket fabrication, from high-density polymers to advanced composites, assessing their impact on patient comfort and prosthetic performance. Additionally, we discuss the challenges practitioners face in prosthetic care, particularly in low-resource settings, and propose potential solutions through innovative techniques and materials. Advancements in computational modeling improved socket design and validation, enhancing patient comfort and improving the overall biomechanical interaction between the prosthesis and the user. The manuscript concludes by identifying future research opportunities, particularly in personalized prosthetic design and the integration of smart materials, to further enhance the comfort, functionality, and accessibility of prosthetic sockets. Full article

Background/Objectives: In recent years, 3D shape models of the human body have been used for various purposes. In principle, CT and MRI tomographic images are necessary to create such models. However, CT imaging and MRI generally impose heavy physical and financial burdens on the person being imaged, the model creator, and the hospital where the imaging facility is located. To reduce these burdens, the purpose of this study was to propose a method of creating individually adapted models by using simple X-ray images, which provide relatively little information and can therefore be easily acquired, and by transforming an existing base model. Methods: From medical images, anatomical feature values and scanning feature values that use the points that compose the contour line that can represent the shape of the femoral knee joint area were acquired, and deformed by free-form deformation. Free-form deformations were automatically performed to match the feature values using optimization calculations based on the confidence region method. The accuracy of the deformed model was evaluated by the distance between surfaces of the deformed model and the node points of the reference model. Results: Deformation and evaluation were performed for 13 cases, with a mean error of 1.54 mm and a maximum error of 12.88 mm. In addition, the deformation using scanning feature points was more accurate than the deformation using anatomical feature points. Conclusions: This method is useful because it requires only the acquisition of feature points from two medical images to create the model, and overall average accuracy is considered acceptable for applications in biomechanical modeling and motion analysis. Full article

Background/Objectives: The simulation of human movement offers transformative potential for the design of medical devices, particularly in understanding the cause–effect dynamics in individuals with neurological or musculoskeletal impairments. This study presents a simulation-driven framework to determine the optimal ankle–foot orthosis (AFO) stiffness for mitigating the risk of ankle sprains due to excessive subtalar inversion during high-impact activities, such as landing from a free fall. Methods: We employed biomechanical simulations to assess the influence of translational stiffness on subtalar inversion control, given that inversion angles exceeding 25 degrees are strongly correlated with injury risk. Simulations were conducted using a musculoskeletal model with and without a passive AFO; the stiffness varied in three anatomical directions. A Design of Experiments (DoE) approach was utilized to capture nonlinear interactions among stiffness parameters. Results: The results indicated that increased translational stiffness significantly reduced inversion angles to safer levels, though direction–dependent effects were noted. Based on these insights, we developed a 4D visualization tool that integrates simulation data with an interactive color–coded interface to depict ”safe design” zones for various AFO stiffness configurations. This tool supports clinicians in selecting stiffness values that optimize both safety and functional performance. Conclusions: The proposed framework enhances clinical decision-making and engineering processes by enabling more accurate and individualized AFO designs. Full article

Background/Objectives: This study focuses on the motion planning and control of an active ankle–foot orthosis (AFO) that leverages biomechanical insights to mitigate footdrop, a deficit that prevents safe toe clearance during walking. Methods: To adapt the motion of the device to the user’s walking speed, a geometric model was used, together with real-time measurement of the user’s gait cycle. A geometric speed-adaptive model also scales a trapezoidal ankle-velocity profile in real time using the detected gait cycle. The algorithm was tested at three different walking speeds, with a prototype of the AFO worn by a test subject. Results: At walking speeds of 0.44 and 0.61 m/s, reduced tibialis anterior (TA) muscle activity was confirmed by electromyography (EMG) signal measurement during the stance phase of assisted gait. When the AFO was in assistance mode after toe-off (initial and mid-swing phase), it provided an average of 48% of the estimated required power to make up for the deliberate inactivity of the TA muscle. Conclusions: Kinematic analysis of the motion capture data showed that sufficient foot clearance was achieved at all three speeds of the test. No adverse effects or discomfort were reported during the experiment. Future studies should examine the device in populations with footdrop and include a comprehensive evaluation of safety. Full article

Background/Objectives: Artificial tendons offer an alternative to biological tendon grafts and may restore normative biomechanical functions in humans and animals suffering segmental or complete tendon loss. The aim of this study was to quantify movement biomechanics during hopping gait and muscle properties of New Zealand White rabbits with a polyester silicone-coated (PET-SI) artificial tendon. Methods: In five rabbits, the biological Achilles tendon of the left hindlimb was surgically replaced with a PET-SI artificial tendon; five operated control rabbits underwent complete surgical excision of the biological Achilles tendon in the left hindlimb with no replacement (TE). Results: Across both groups at 2 and 8 weeks post-surgery compared to baseline, the maximum ankle angle during stance and swing phases of stride was significantly lower (i.e., more dorsiflexed) (p < 0.001), the peak vertical force was significantly higher (p < 0.001), and the average ground contact area was significantly lower (p < 0.001). At 8 weeks post-surgery, the muscle cross-sectional area of the lateral gastrocnemius was significantly higher in the PET-SI group than in the TE group (p = 0.006). Muscle mass and length were lower in the operated limb compared to the non-operated limb across the two groups (TE and PET-SI), with no significant differences between groups. Conclusions: The artificial Achilles tendon did not appear to provide superior biomechanical support during hopping compared to the TE group. However, the artificial tendon preserved muscle structural properties that correspond to the muscle’s capacity to generate force. Future studies should optimize the tendon–tissue interface. Full article

Background/Objectives: The assessment of relationships between trunk muscle activity and thoraco-lumbar movements during sagittal bending has demonstrated that low back pain (LBP) subgroups (flexion pattern and active extension pattern motor control impairment) reveal distinct relationships that differentiate these subgroups from control groups. The study objective was to establish whether such relationships exist during various daily activities. Methods: Fifty participants with non-specific chronic low back pain (NSCLBP) (27 flexion pattern (FP), 23 active extension pattern (AEP)) and 28 healthy controls were recruited. Spinal kinematics were analysed using 3D motion analysis (Vicon™, Oxford, UK) and the muscle activity recorded via surface electromyography during a range of activities (box lift, box replace, reach up, step up, step down, stand-to-sit, and sit-to-stand). The mean sagittal angles for upper and lower thoracic and lumbar regions were correlated with normalised mean amplitude electromyography of bilateral transversus abdominis/internal oblique (IO), external oblique (EO), superficial lumbar multifidus (LM), and erector spinae (ES). Relationships were assessed via Pearson correlations (significance p < 0.01). Results: In the AEP group, increased spinal extension was associated with altered LM activity during box-replace, reach-up, step-up, and step-down tasks. In the FP group, increased lower lumbar spinal flexion was associated with reduced muscle activation, while increased lower thoracic flexion was associated with increased muscle activation. The control group elicited no significant associations. Correlations ranged between −0.812 and 0.754. Conclusions: Differential relationships between muscle activity and spinal kinematics exist in AEP, FP, and pain-free control groups, reinforcing previous observations that flexion or extension-related LBP involves distinct motor control strategies during different activities. These insights could inform targeted intervention approaches, such as movement-based interventions and wearable technologies, for these groups. Full article

Robotic cadaveric testing provides a controlled approach to studying knee ligament biomechanics under continuous motion, addressing limitations in static or mechanical loading testing. Our study describes an alternative method for soft-tissue strain measurement, followed by an investigation of this method on knee ligament strain and joint kinematics using a six-degree-of-freedom robotic system equipped with force and torque sensors. Six cadaveric knee specimens underwent controlled 90° flexion cycles, with uniaxial strain gauges sutured to the ACL, PCL, MCL, and LCL for strain measurement. Results indicate that the LCL exhibited the highest extension at 1.63 mm, while the ACL showed minimal extension at 0.09 mm. The MCL were at −0.76 mm and PCL at −1.76 mm contraction, suggesting a stabilizing function under flexion. Varus torque at 2.18 Nm at 90° flexion correlated with LCL strain, and PCL translation variability reflected its multi-planar engagement. These findings confirm ligament-specific strain responses under dynamic loading, highlighting that the LCL and PCL undergo the most significant length changes. Full article

Introduction: Therapeutic footwear has been often prescribed in clinical practice for accommodating foot deformities and preventing the development of ulceration, yet scientific evidence is limited and outdated. This study aimed to investigate the effects of two types of Orthofeet therapeutic footwear in comparison to low-cost generic as well as participants’ own athletic shoes on plantar pressure as well as lower extremity kinematics and kinetics. Methods: Twenty healthy participants without foot disorders or pain walked at self-paced speeds under each of the four footwear conditions. In-shoe plantar pressures were measured using F-Scan, and the gait kinematics and kinetics in the sagittal plane were obtained. The foot was divided into eight anatomical zones and three combined zones (forefoot, mid-foot, and hind foot), with peak plantar pressures recorded in each zone. Results: The therapeutic footwear showed significantly greater ankle dorsiflexion during late midstance and less ankle plantar flexion during push-off than generic shoes. Similarly, larger ankle plantar flexor torques were shown when wearing therapeutic footwear. Therapeutic footwear modified the plantar pressure distribution, increasing the peak pressure under the big toe while slightly reducing the peak pressure under the medial heel. The participants’ own athletic shoes provided slightly distinct outcome measures yet comparable performance when compared to therapeutic footwear. Conclusions: This study suggests that therapeutic footwear offers some distinct biomechanical modifications compared with generic shoes. Future studies are needed to assess if these changes lead to meaningful clinical outcomes, such as reduced injury risk or improved foot health. Full article

Background/Objectives: The conventional practice in clinical settings involves using multi-use surgical instrumentation (SI). However, there is a growing trend towards transforming these multi-use SIs into disposable surgical instruments, driven by economic and environmental considerations without considering the biomechanical aspects. This study focuses on redesigning an SI kit for implanting cervical spinal facet cages. Understanding the boundary conditions (forces, torques, and bending moments) acting on the SI during surgery is crucial for optimizing its design and materials. Therefore, this study aims to develop a measurement system (MS) to record these loads during implantation and validate it through in vitro testing. Methods: A combined numerical–experimental approach was used to design and calibrate the MS. Finite element analysis (FE) was used to optimize the geometry of the sensitive element of the MS. This was followed by the manufacturing phase using 3D printing and then by calibration tests to determine the stiffness of the system. Finally, the MS was used to measure the boundary conditions applied during SI use during in vitro tests on a cervical Sawbone spine. Results: After designing the measurement system (MS) via finite element analysis, calibration tests determined stiffness values of K_F = 1.2385 N/(µm/m) (axial compression), K_T = −0.0015 Nm/(µm/m) (torque), and K_B = 0.0242 Nm/(µm/m) (non-axial force). In vitro tests identified maximum loads of 40.84 N (compression) and 0.11 Nm (torque). Conclusions: This study developed a measurement system to assess surgical implant boundary conditions. The data will support finite element modeling, guiding the optimization of implant design and materials. Full article