Joint Motion Research Articles

Comparison of IMU-Based Knee Kinematics with and without Harness Fixation against an Optical Marker-Based System.

The use of inertial measurement units (IMUs) as an alternative to optical marker-based systems has the potential to make gait analysis part of the clinical standard of care. Previously, an IMU-based system leveraging Rauch-Tung-Striebel smoothing to estimate knee angles was assessed using a six-degrees-of-freedom joint simulator. In a clinical setting, however, accurately measuring abduction/adduction and external/internal rotation of the knee joint is particularly challenging, especially in the presence of soft tissue artefacts. In this study, the in vivo IMU-based joint angles of 40 asymptomatic knees were assessed during level walking, under two distinct sensor placement configurations: (1) IMUs fixed to a rigid harness, and (2) IMUs mounted on the skin using elastic hook-and-loop bands (from here on referred to as "skin-mounted IMUs"). Estimates were compared against values obtained from a harness-mounted optical marker-based system. The comparison of these three sets of kinematic signals (IMUs on harness, IMUs on skin, and optical markers on harness) was performed before and after implementation of a REference FRame Alignment MEthod (REFRAME) to account for the effects of differences in coordinate system orientations. Prior to the implementation of REFRAME, in comparison to optical estimates, skin-mounted IMU-based angles displayed mean root-mean-square errors (RMSEs) up to 6.5°, while mean RMSEs for angles based on harness-mounted IMUs peaked at 5.1°. After REFRAME implementation, peak mean RMSEs were reduced to 4.1°, and 1.5°, respectively. The negligible differences between harness-mounted IMUs and the optical system after REFRAME revealed that the IMU-based system was capable of capturing the same underlying motion pattern as the optical reference. In contrast, obvious differences between the skin-mounted IMUs and the optical reference indicated that the use of a harness led to fundamentally different joint motion being measured, even after accounting for reference frame misalignments. Fluctuations in the kinematic signals associated with harness use suggested the rigid device oscillated upon heel strike, likely due to inertial effects from its additional mass. Our study proposes that optical systems can be successfully replaced by more cost-effective IMUs with similar accuracy, but further investigation (especially in vivo and upon heel strike) against moving videofluoroscopy is recommended.

Correction to: An improved methodology to restrict the range of motion of mechanical joints

Correction to: An improved methodology to restrict the range of motion of mechanical joints

A new contact force model for revolute joints considering elastic layer characteristics effects

The contact forces generated during the motion of revolute joints with clearances significantly impact the dynamic performance of mechanisms, making it essential to develop an accurate contact force model. Traditional contact models often neglect the influence of elastic layers or assume that the bushing thickness is equal to its radius, which limits their applicability. To address the dynamic contact problem in revolute joints with small clearances, this study employs an improved Winkler elastic foundation model and introduces an elastic layer correction coefficient to refine the static contact model. The model's validity is verified using the finite element method. Building on this, a new contact force model is proposed, incorporating the optimal damping term from multiple continuous contact models. Finally, experimental validation is conducted using the crank-slider mechanism and typical applications in the Variable Stator Vane (VSV) mechanism. The results demonstrate that the proposed contact force model effectively predicts the dynamic characteristics of mechanisms with clearances.

A retrospective study on two different surgical robots to assist total knee arthroplasty

To compare early clinical and imaging results of domestic HURWA and imported Brainlab Knee3 surgical robot-assisted knee replacement. A retrospective analysis was performed on 93 patients with knee osteoarthritis (KOA) who underwent robot-assisted descending total knee arthroplasty(TKA) from January 2021 to July 2023, and they were divided into BRATKA group and HRATKA group according to use of robotic system. There were 40 patients in BRATKA group, including 16 males and 24 females, aged from 55 to 90 years old with an average of (64.3±7.0) years old;27 patients with grade Ⅲ and 13 patients with grade Ⅳ according to Kellgren-Lawrence(K-L);18 patients on the right side and 22 patients on the left side;the courses of disease ranged from 1 to 30 years with an average of (15.3±7.6) years;imported Brainlab Knee3 surgical robot assisted system was adopted. There were 53 patients in HRATKA group, including 18 males and 35 females, aged from 52 to 81 years old with an average of (64.4±8.5) years old;30 patients with grade Ⅲ and 23 patients with grade Ⅳ;21 patients on the right side and 32 patients on the left side;the courses of disease ranged from 1 to 32 years with an average of (16.4±7.9) years;HURWA surgical robot assisted system was adopted. Operation time, perioperative total blood loss, incision length and postoperative complications were compared between two groups. Deviation angle of hip-knee-ankle angle(HKAA) before operation and on the first day after operation was compared between two groups. Later tibal component (LTC), frontal femoral component (FFC), later femoral component (LFC) and frontal tibal component(FTC) at 1 day after on the first day after operation was compared between two groups. Knee Society score(KSS), visual analogue scale (VAS) and range of motion (ROM) of knee joint were compared between two groups before operation and on the 3rd and 90th day after operation. Both groups were followed up for 11 to 18 months with an average of (14.4±2.1) months, and the wounds of all patients healed well. Operation time and incision length of BRATKA group were (132.1±34.6) min and (12.9±1.9) cm, while (94.1±10.8) min and (14.8±2.1) cm in HRATKA group, respectively, and the differences between two groups were statistically significant(P<0.05). There were no significant difference in perioperative total blood loss and preoperative deviation angle of HKAA between two groups(P>0.05). Deviation angle of HKAA, FFC angle and LFC angle in BRATKA group were (1.90±0.91) °, (87.90±1.51) ° and(9.00±3.2) °, respectively;while (0.93±1.04) °, (89.03±0.96) ° and (7.63±0.59) ° in HRATKA group, respectively, and the differences between two groups were statistically significant (P<0.05). There were no significant differences in FTC and LTC between two groups(P>0.05). There were no significant differences in VAS of knee rest and exercise, KSS score and ROM of knee joint between two groups before operation and 3 days and 90 days after operation(P>0.05). There was no significant difference in complications between two groups (P>0.05). Postoperative imaging of two robot systems showed good lower limb force line. The domestic HRATKA group had better LFC, FFC angle and HKA deviation angle than the imported BRATKA group, but there were no significant difference in postoperative knee function and pain relief.

Multivariate analysis of influencing functional recovery after ankle fracture of typeⅡand above supination-external rotation

To explore influencing factors of functional recovery after ankle fracture of typeⅡdegree and above supination-external rotation. Clinical data of 120 patients with ankle fractures of typeⅡdegree and above supination-external rotation admitted from February 2019 to April 2021 were retrospectively analyzed. According to American Orthopaedic Foot and Ankle Society (AOFAS), patients were divided into excellent group with 73 patients (90 to 100 points), good group with 35 patients (75 to 89 points), and fair group with 12 patients(<50 points). The differences of ankle active range of motion (ROM) and AOFAS score were compared among three groups at the latest follow-up. Multivariate Logistic regression analysis was performed to analyze the factors related to functional recovery after ankle fracture of supination-external rotation. There were significant differences in postoperative ROM (dorsoextension, plantar flexion, varus and valgus) and complications between excellent group and good and acceptable group (P<0.05). Univariate analysis showed there were differences in age above 50 years old, Ⅳ degree of supination-external rotation fracture, lower tibiofibular ligament injury, posterior ankle fracture, no drainage tube placed, infection, antibiotic use time above 7 days (P<0.05). Multivariate Logistic regression analysis showed age above 50 years old[OR=2.829, 95%CI(1.049, 7.628), P=0.040], Ⅳ degree fracture of supination-external rotation[OR=6.13, 95%CI(1.153, 32.593), P=0.033], lower tibiofibular ligament injury[OR=10.785, 95%CI(3.338, 34.894), P=0.000], and posterior ankle fracture[OR=6.349, 95%CI(1.869, 21.560), P=0.003] were independent risk factors for functional recovery after ankle fracture of supination-external rotation (P<0.05). The postoperative excellent outcome of ankle fracture was good, and the recovery of joint motion was better. The older age of patient, Ⅳ degree of supination-external rotation fracture, the lower tibiofibular ligament injury, and posterior ankle fracture are all adverse factors affecting functional recovery after supination-external rotation ankle fracture. In clinical, effective measures should be taken to deal with these influencing factors, and strive to improve the functional recovery after the operation of this type of fracture and reduce the occurrence of related complications.

Assessing the reliability of a digital inclinometer app for measuring hip, knee, and ankle proprioception.

Proprioception can be defined as the ability of an individual to detect motion and position of the various joints in their bodies. Current tools for measuring proprioception lack consensus on their accuracy and validity; they also each have their own limitations, and, furthermore, present barriers to use for clinicians. We propose a new and reliable method for evaluating hip, knee, and ankle proprioception by utilizing a digital inclinometer app to measure joint position sense. The digital inclinometer app recorded the active joint position sense error after each of five trials for the hip and knee joint and ten trials for the ankle joint. To quantify the reliability of the digital inclinometer app, single-measurement and average-measurement intra-class correlation coefficients (ICC) along with the associated 95% confidence intervals (95% CI) were calculated for each joint's position sense error across trials. Both the hip (ICC (2,k) = 0.849 (95% CI = [0.783-0.897])) and knee joint (ICC (2,k) = 0.837 (95% CI = [0.750-0.897])) were found to have moderate to good reliability when the middle three of five trials were analyzed. Unlike the hip and knee, moderate to good reliability for ankle proprioception (ICC (2,k) = 0.785 (95% CI = [0.539-0.893])) was only achieved with the middle eight of ten trials. The results of this study indicate that this digital inclinometer app is able to accurately record joint position sense at the hip, knee, and ankle when the appropriate number of trials are collected; thus, allowing this tool and methodology to be considered for use in both clinical and research environments to measure proprioception, and furthermore, quantify proprioceptive deficits.

Comparison of joint kinematics from optical marker-based and inertial sensor-based motion capture during change-of-direction movements

The development of inertial measurement units (IMUs) has opened up possibilities to test kinematics of sports movements in natural environments (Di Paolo et al., 2023). This advantage over lab-based optical motion capture (OMC) comes at the cost of inherent inaccuracies. Especially, fast multidirectional movements including de- and accelerations pose a challenge for inertial-based movement reconstruction with limited task-specific validation research available (Heuvelmans et al., 2022). Therefore, we aimed to test the validity of IMU-based kinematics in a 180° change of direction (COD) task to provide insight into the applicability for future on-field ACL injury risk research. Twenty-six sports science students were equipped with eight IMU sensors of the Noraxon Ultium Motion System and an adaption of the Plug-in-Gait markerset (53 markers) recorded by a VICON OMC system. They performed five 180° anti-clockwise CODs at their maximum speed. As an example for sagittal and frontal plane angles relevant for ACL injury risk, the knee flexion and abduction angle at the initial contact of the cutting step (right leg) were calculated using the Noraxon MyoMotion software for IMU-recorded data and OpenSim for marker-based OMC data. At the time of abstract submission, the data of five (randomly chosen) participants had been analysed. More participants and more joint angle outcomes will be included in follow-up analyses. Deviations between IMU-generated and OMC-generated joint angles are depicted in Figure 1. Within subjects, deviations below 1.5 standard deviations were observed. Between subjects, deviations ranged from 0° and 22° in knee flexion angles and 0° and 11° in knee abduction angles. A general trend towards higher joint angles measured by the IMU system is noticeable, suggesting a possible off-set error. For four out of five participants, the knee flexion deviation was below 10°, which can be considered an accuracy which is tolerable but requires consideration in the interpretation (&lt; 2°: good accuracy, 2-5°: acceptable accuracy, 5-10°: tolerable accuracy, &gt; 10° unbearable accuracy; Bessone et al., 2022). Deviations in knee abduction angles appear too large given the small physiological joint range and motion in this plane. This preliminary analysis of individual deviations suggests acceptable deviations between IMU and OMC measurements regarding knee flexion but problematic deviations for knee abduction. Prospectively, we aim to investigate possible off-set corrections, e.g. through a better alignment of the underlying biomechanical models, and alternative approaches for IMU-based movement reconstruction, e.g. through optimal control simulations (Nitschke et al., 2024).

Starch/polyacrylamide hydrogels with flexibility, conductivity and sensitivity enhanced by two imidazolium-based ionic liquids for wearable electronics: Effect of anion structure

To meet the growing demands for sustainable and eco-friendly wearable electronics, biopolymer-based hydrogels have attracted much attention. As one of the most abundant sources of biopolymers, starch has the advantages of low-cost, renewability, biocompatibility and biodegradability. However, mechanical fragility, low conductivity and low sensitivity limited the application of starch-based hydrogels. Herein, two imidazolium-based ionic liquids with different anions (chloridion and acetate) were introduced into corn starch/polyacrylamide hydrogels. The mechanical properties (the maximum elongation: 515.4 %), conductivity (the maximum value: 3.1 S·m−1) and sensitivity (the maximum gauge factor value: 9.3) of the hydrogel were enhanced by the two ionic liquids and proved by the microcosmic characterizations and theoretical simulations (DFT). The two ionic liquids varied in their impacts on the above properties of the hydrogels due to the different anion structure. In mechanical properties, acetate was dominant over chloridion, while the opposite was true for conductivity. Based on the above properties of the starch-based hydrogels, wearable electronics were constructed for detecting human joint motions, subtle expressions, temperature and touch screen operations. This work not only provides novel starch-based hydrogels as candidates for the wearable electronics, but also lays a theoretical foundation for the application of ionic liquids in biopolymer-based materials.

Effects of functional training on tennis-specific physical fitness and functional movement screen in junior tennis players

Objectives Functional training mimics the coordinated motions of multiple muscle groups and joints performed during exercise. The purpose of this study was to compare the effects of a 12-week functional training and traditional resistance training on the performance in junior tennis players. Methods Trained tennis players (mean age: 16.6 years) were assigned to a traditional training group (n = 20) or functional training group (n = 20). The traditional training group received a resistance training program by their coach, while the functional training group was given Santana’s Racket Sport Program. At baseline, after six weeks, and after 12 weeks (T12), the participants’ tennis-specific physical fitness and functional movement screen (FMS) were evaluated. Results At T12, both training improved the values for multistage fitness test, hexagon test, planned agility test, sit and reach, and 20 metre sprint (p &lt; 0.05); except the flexibility, functional training provided no additional advantages. At T12, functional training enhanced (p &lt; 0.01) all seven components of the FMS, and there is a 100% probability that the total score of the FMS would be enhanced. In contrast, for the traditional training group, shoulder mobility of the FMS decreased (p = 0.03), and there was no changes in other FMS components at T12. Conclusions Functional training is not only effective in improving tennis-specific physical fitness, but it also provides greater functional movement advantages for junior tennis players compared to traditional resistance training.

Research on the Safety Design and Trajectory Planning for a New Dual Upper Limb Rehabilitation Robot

The increasing utilization of upper limb rehabilitation robots in rehabilitation therapy has brought to light significant safety concerns regarding their mechanical structures and control systems. This study focuses on a six degrees of freedom (DOF) upper limb rehabilitation robot, which has been designed with an emphasis on safety through careful consideration of its mechanical structure and trajectory planning. Various parameter schemes for the shoulder joint angles were proposed, and the robotic arm’s structure was developed by analyzing the spatial motion trajectories of the shoulder joint motor. This design successfully achieves the objective of minimizing the installation space while maximizing the range of motion. Additionally, an enhanced artificial field method is introduced to facilitate the planning of self-collision avoidance trajectories for dual-arm movements. This approach effectively mitigates the risk of collisions between the robotic arm and the human body, as well as between the two robotic arms, during movement. The efficacy of this method has been validated through experimental testing.

Research on the Motion Control Strategy of a Lower-Limb Exoskeleton Rehabilitation Robot Using the Twin Delayed Deep Deterministic Policy Gradient Algorithm.

The motion control system of a lower-limb exoskeleton rehabilitation robot (LLERR) is designed to assist patients in lower-limb rehabilitation exercises. This research designed a motion controller for an LLERR-based on the Twin Delayed Deep Deterministic policy gradient (TD3) algorithm to control the lower-limb exoskeleton for gait training in a staircase environment. Commencing with the establishment of a mathematical model of the LLERR, the dynamics during its movement are systematically described. The TD3 algorithm is employed to plan the motion trajectory of the LLERR's right-foot sole, and the target motion curve of the hip (knee) joint is deduced inversely to ensure adherence to human physiological principles during motion execution. The control strategy of the TD3 algorithm ensures that the movement of each joint of the LLERR is consistent with the target motion trajectory. The experimental results indicate that the trajectory tracking errors of the hip (knee) joints are all within 5°, confirming that the LLERR successfully assists patient in completing lower-limb rehabilitation training in a staircase environment. The primary contribution of this study is to propose a non-linear control strategy tailored for the staircase environment, enabling the planning and control of the lower-limb joint motions facilitated by the LLERR.

Application of tuberosity suture combined with autogenous bone grafting in reverse total shoulder arthroplasty for elderly patients with proximal humeral fractures

To analyze the effectiveness of tuberosity suture combined with autogenous bone grafting in reverse total shoulder arthroplasty for elderly patients with proximal humerus fracture. A clinical data of 28 patients with fresh proximal humerus fractures, who met the selection criteria and admitted between June 2014 and April 2022, was retrospectively analyzed. There were 7 males and 21 females. Age ranged from 65 to 81 years, with an average of 73.8 years. The causes of injury were 21 cases of fall, 6 cases of traffic accident, and 1 case of falling from height. The time from injury to operation ranged from 5 to 20 days with an average of 9.2 days. There were 8 cases of Neer three-part fracture and 20 cases of four-part fracture. The reverse total shoulder arthroplasty was performed, and the greater and lesser tuberosities were sutered and reconstructed with autogenous bone grafting. After operation, the Constant score, American Society for Shoulder Surgery (ASES) score, and visual analogue scale (VAS) score were used to evaluate shoulder function and pain; and the active range of motion of the shoulder joint was recorded, including flexion, external rotation, and internal rotation. X-ray films were taken to observe the position of prosthesis. According to the evaluation criteria proposed by Boileau, the healing of greater tuberosity was evaluated, and the effectiveness was compared between the patients with healed and non-healed (displacement and absorption) greater tuberosity. All incisions healed by first intention after operation. All patients were followed up 24-106 months, with an average of 60.9 months. At last follow-up, the VAS score of shoulder joint ranged from 0 to 6 (mean, 1.1). The Constant score ranged from 45 to 100 (mean, 80.1). The ASES score ranged from 57 to 100 (mean, 84.7). The active range of motions of shoulder joint were 60°-160° (mean, 118°) in flexion, 0°-50° (mean, 30°) in external rotation, and corresponding to reaching the S 5-T 8 vertebral body level in internal rotation. During follow-up, no shoulder joint re-dislocation or severe shoulder instability occurred, and no revision surgery was performed. X-ray film reexamination showed that there was no loosening of the prosthesis. According to the evaluation criteria proposed by Boileau, the greater tuberosity fused in 22 cases (78.6%), displaced in 3 cases (10.7%), and absorbed in 3 cases (10.7%). The shoulder joint function and pain related evaluation indicators in the healed group were significantly better than those in the non-healed group ( P<0.05). Tuberosity suture combined with autogenous bone grafting is a relatively simple procedure that provides a reliable fixation for the anatomic recovery of greater and lesser tuberosities and is beneficial for the recovery of shoulder function in elderly patients with proximal humeral fractures.

The role of limb alignment on natural tibiofemoral kinematics and kinetics.

This study aimed to analyze kinematics and kinetics of the tibiofemoral joint in healthy subjects with valgus, neutral, and varus limb alignment throughout multiple gait activities using dynamic videofluoroscopy. Five subjects with valgus, 12 with neutral, and ten with varus limb alignment were assessed during multiple complete cycles of level walking, downhill walking, and stair descent using a combination of dynamic videofluoroscopy, ground reaction force plates, and optical motion capture. Following 2D/3D registration, tibiofemoral kinematics and kinetics were compared between the three limb alignment groups. No significant differences for the rotational or translational patterns between the different limb alignment groups were found for level walking, downhill walking, or stair descent. Neutral and varus aligned subjects showed a mean centre of rotation located on the medial condyle for the loaded stance phase of all three gait activities. Valgus alignment, however, resulted in a centrally located centre of rotation for level and downhill walking, but a more medial centre of rotation during stair descent. Knee adduction/abduction moments were significantly influenced by limb alignment, with an increasing knee adduction moment from valgus through neutral to varus. Limb alignment was not reflected in the condylar kinematics, but did significantly affect the knee adduction moment. Variations in frontal plane limb alignment seem not to be a main modulator of condylar kinematics. The presented data provide insights into the influence of anatomical parameters on tibiofemoral kinematics and kinetics towards enhancing clinical decision-making and surgical restoration of natural knee joint motion and loading.

Influence of whole-body vibration and drop jump on the range of motion in the ankle joint and running parameters-Arandomized crossover study.

Warm-up (WU) is a commonly practiced technique aimed at preparing athletes for physical activity. Although coaches and athletes consider WU essential, there is still an ongoing debate about its effectiveness. This might be due to the fact that WU procedures often rely on experiences rather than scientific research. During WU, athletes may pursue intermediate goals such as ensuring proper ranges of motion in joints, which seem crucial particularly for runners' ankle joints. Hence, the aim of this study was to evaluate influence of whole-body vibration (WBV), drop jump (DJ), and a combination of both (WBV+DJ) in terms of ankle dorsiflexion and running parameters among recreational runners. Sixteen runners performed as a WU: five sets of 30s calf raises without WBV (CTRL), five sets of 30s calf raises during WBV, five sets of six DJ, five sets of 30s calf raises during WBV followed by 6 DJ. Range of motion (ROM) of the ankle joint was measured in a prone position using an inclinometer for the soleus and gastrocnemius muscles, separately. Measurements were conducted before and after WU, and after a 3000m run. There was no interaction for time and WU for left (p=0.926) and right (p=0.738) soleus muscle as well as for left (p=0.748) and right (p=0.197) gastrocnemius muscles. No difference (p=0.914) for the running time was found. WBV, drop jumps, or a combination of both did not affect ankle dorsiflexion and running time.

Extracorporeal Shock Wave and Melatonin Alleviate Joint Capsule Fibrosis after Knee Trauma in Rats by Regulating Autophagy.

Joint contracture is a common clinical problem affecting joint function. Capsule fibrosis plays a pivotal role in the progression of Joint contracture. Previous studies have reported that autophagy plays a regulatory role in visceral fibrosis. This study aimed to investigate whether extracorporeal shock wave therapy (ESWT) and melatonin alleviate joint capsule fibrosis in rats with extended knee joint contracture by regulating autophagy. A rat knee joint extension contracture model was made. Then, the rats were treated with ESWT, melatonin, ESWT + melatonin, or ESWT + melatonin + mTOR agonist for 4 weeks. The range of motion (ROM) of the knee joints was measured. Joint capsules were collected and observed for pathological changes by H&E and Masson staining. LC3B protein expression was evaluated by immunofluorescence staining. TGF-β1, MMP-1, Col-Ⅰ, Col-Ⅲ, LC3, ATG7, Beclin1, p-AMPK, p-mTOR and p-ULK1 protein expressions were measured by Western blot assay. The intervention groups had significantly improved ROM of knee joint (P < 0.05), significantly improved pathological changes on HE and Masson staining, significantly decreased protein expressions of TGF-β1, MMP-1, Col-Ⅰ, Col-Ⅲ and pmTOR (P < 0.05), and significantly increased protein expressions of LC3B, LC3II/LC3I ratio, ATG7, Beclin1, p-AMPK, and p-ULK1 (P < 0.05). Among these groups, the effects demonstrated by the ESWT + melatonin group were the best. With the mTOR agonist supplement, the therapeutic effects of extracorporeal shock waves and melatonin were significantly reduced. ESWT plus melatonin alleviated knee joint capsule fibrosis in rats by regulating autophagy.

Self-powered strain sensing devices with wireless transmission: DIW-printed conductive hydrogel electrodes featuring stretchable and self-healing properties

With rapid advancements in health and human–computer interaction, wearable electronic skins (e-skins) designed for application on the human body provide a platform for real-time detection of physiological signals. Wearable strain sensors, integral functional units within e-skins, can be integrated with Internet of Things (IoT) technology to broaden the applications for human body monitoring. A significant challenge lies in the reliance of most existing wearable strain sensors on rigid external power supplies, limiting their practical flexibility. In this study, we present an innovative strategy to fabricate glutaraldehyde (GA)-poly(vinyl alcohol) (PVA)/cellulose nanocrystals (CNC)/Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) conductive hydrogels through multiple hydrogen bonding systems. Combining the advantageous rheological properties of the precursor solution and the high specific surface area after freeze–thaw cycling, we have created a self-powered sensing system prepared by large-area printing using direct ink writing (DIW) printing. The resulting conductive hydrogel exhibits commendable mechanical properties (411 KPa), impressive stretchability (580 %), and robust self-healing capabilities (>98.3 %). The strain sensor, derived from the conductive hydrogel, demonstrates a gauge factor (GF) of 2.5 within a stretching range of 0–580 %. Additionally, the resultant supercapacitor displays a peak energy density of 0.131 mWh/cm3 at a power density of 3.6 mW/cm3. Benefiting from its elevated strain response and remarkable power density features, this self-powered strain sensing system enables the real-time monitoring of human joint motion. The incorporation of a 5G transmission module enhances its capabilities for remote data monitoring, thereby contributing to the progress of wireless tracking technologies for self-powered electronic skin.

A new method called MiKneeSoTA to minimize knee soft-tissue artifacts in kinematic analysis

The use of marker-based optical motion capture to estimate joint kinematics during gait is currently limited by errors associated with soft-tissue-induced motion artefacts (STIMA) and ambiguity in landmark palpation. This study therefore presents a novel protocol aiming to Minimize Knee Soft-Tissue Artefacts (MiKneeSoTA) and their effect on kinematic estimates. Relying on an augmented marker set and a new inverse kinematics approach, our method leverages frame-by-frame optimization to adjust best-fit cylinders that have been automatically generated based on the relative position of lower limb markers during an initial static trial. Tibiofemoral rotations and translations are then calculated along the anatomical joint axes based on the relative 3D motion of these cylinders. When compared against the conventional Helen-Hayes approach, in vivo assessment of fifteen healthy subjects revealed the MiKneeSoTA approach led to kinematic profiles with significantly lower standard deviations in joint rotations across trials, and even visibly reduced the presence of high frequency fluctuations presumably associated with e.g. soft-tissue vibration. In addition to agreeing with previously published bone pin and fluoroscopy datasets, our results illustrate MiKneeSoTA’s ability to abate the effect of STIMA induced by lateral knee ligaments. Our findings indicate that MiKneeSoTA is in fact a promising approach to mitigate knee joint STIMA and thus enable the previously unattainable accurate estimation of translational knee joint motion with an optoelectronic system.

Polyethylene liner dissociation in cementless total hip arthroplasty: Ensuring accurate diagnosis.

Uncemented acetabular components are widely used in modern total hip arthroplasty (THA). Modularity has numerous advantages including the ability to use supplementary screw fixation for the shell, and allow to switch from ceramic to polyethylene (PE) bearings and vice versa, and the use of lipped and face-changing liners. Despite these advantages, a problem with modular PE liners is dissociation. This is a rare complication in modern implants. The rate of liner dissociation is reported to be very low between 0.17% and 0.8%. Typical symptoms are sudden onset of groin pain in a previously well-functioning hip joint, followed by grinding or clicking sensations during hip joint motions indicating, that the femoral head is articulating with the metal acetabular shell rather than with the PE liner. Any newly observed noise or squeaking from a THA should undergo radiographic investigation to exclude liner dissociation. We present the case of an 88-yearold male patient who developed PE liner dissociation in a cementless THA with a Pinnacle acetabular component six years after the index operation. We recommended revision of the left hip, which was performed two days later. In the interim, the patient was advised to use a pair of crutches. During revision surgery, it was observed that the metal head made contact with the cementless cup shell without damaging it from a macroscopic standpoint. Consequently, a simple exchange of the PE liner was conducted, and a 36 mm metal head was implanted due to scratches on the original head. Early diagnosis facilitates a straightforward exchange of the liner along with the head, potentially preserving the osseous integrated cup shell and stem integrity. Routine radiologic follow-up allows to distinguish between PE liner dissociation and severe PE wear.

Smooth joint motion planning for redundant fiber placement manipulator based on improved RRT*

In automated fiber placement (AFP), addressing the continuous motion planning challenge of redundant layup manipulators in complex environments, this paper proposes an offline redundancy optimization algorithm based on improved RRT* (Rapidly-exploring Random Trees). This algorithm maximizes the utilization of kinematic redundancy to derive smooth joint trajectories devoid of collisions and singularities. Firstly, the algorithm entails constructing a search map by eliminating joint configurations that violate constraints, and subsequently planning and optimizing the joint path by minimizing a multi-objective cost under the map constraint. Furthermore, several strategies are introduced to enhance RRT* for redundancy optimization. These strategies include a piecewise Gaussian sampling strategy (PGSS) to guide efficient tree growth within complex channels and enable joint sampling constrained by task coordinates. Additionally, the improved Steering and Local Optimization method are proposed to plan joint motion while considering intermediate task sequences. The effectiveness of the proposed algorithm is demonstrated in handling complex motion planning scenarios, such as layup involving complex path curves or dense obstacles. Experimental results validate the algorithm's capability to find feasible collision-free and singularity-free paths in relevant scenarios, provided such paths exist. Moreover, trajectory smoothness is optimized with increasing iterations.

A lateral approach allows accurate and stable total elbow replacement in dogs.

Evaluate whether total elbow replacement (TER) through a lateral approach is accurate and stable. 12 skeletally mature large-breed dog cadavers were used. Limb alignment, elbow joint motion, and collateral ligament laxity were evaluated preoperatively. The order of surgery (left or right) and the approach (lateral or medial) were randomly selected for TER in each dog. The other approach was used in the contralateral elbow. Intraoperative technical difficulties, duration of surgery, and anatomic complications were recorded. Limb alignment, elbow joint motion, collateral ligament laxity, and prosthetic component alignment were evaluated after surgery. Data were collected from June 11 to 15, 2023. The duration of surgery using a lateral or medial approach did not differ (P = .499). Anatomic complications were not observed. The lateral approach resulted in 8° more elbow extension (P = .003), 1.58° less lateral collateral ligament constraint (P = .033), 2.80° less medial collateral ligament constraint (P = .002), 4.38° less frontal plane constraint (P = .004), 8° greater humeral component inclination (P = .033), and 5.6° greater radioulnar component varus (P = .001) than the medial approach. Varus of the radius, mechanical axis deviation, limb supination, elbow flexion, mediolateral humeral component and craniocaudal radioulnar component orientation did not differ among joints operated using a lateral or medial approach. In normal cadaveric elbows, a lateral approach for TER appears feasible, producing equivalent limb alignment, joint laxity, and joint motion to normal elbows and to TER placed using a medial approach. In dogs, TER can be performed using a lateral surgical approach.