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Purpose: To evaluate the biomechanical behavior of implants with different neck designs.Materials and Methods: Finite element models of implants with two different neck designs (OsseoSpeed EV and OsseoSpeed Profile EV) were generated. Implants and abutments were subjected to buccally and lingually directed 30-degree oblique loads of 200 N.Results: Under buccally angulated load, the Profile implant model showed lower minimum principal stress when compared to the standard implant model (-63.4 vs -91.9 MPa), whereas the von Mises stress value of the Profile implant model was higher (342 MPa).Conclusion: This preliminary study showed that Profile implants placed in alveolar ridges with buccolingual bone height discrepancy showed similar stress distribution and stress value outcomes when compared to standard implants. [ABSTRACT FROM AUTHOR]

Background: Individuals with nonspecific chronic neck pain (NP) walk with a stiffer spine. However, there is a lack of understanding on kinematic similarities on the limbs during gait between individuals with and without NP.Research Question: Are there differences in gait parameters and the kinematic similarity index (SI) between individuals with and without NP?Methods: Eighteen individuals with NP and 17 controls participated in this study. A three-dimensional motion capture system and two force plates were utilized to measure kinematic changes of the upper and lower limbs during gait. The gait parameters included cadence, speed, stride length, and step width. The SI calculations were compared based on the response vectors from the NP group and the prototype response vectors from the control participants. The SI values at 5% intervals of the entire gait cycle were compared between groups.Results: Although the gait parameters were not significantly different between groups, the SI values of the control group were significantly higher than the NP group during gait (0.98 ± 0.02 vs. 0.95 ± 0.03), especially at the midstance (10-30 %) and swing (80-90 %) phases. Also, the standard deviation of the SI decreased in the control group when compared to the NP group (0.02 ± 0.01 vs. 0.04 ± 0.02).Significance: The SI was a useful measure to differentiate similarities between groups in the gait cycle at specific phases. These results indicated that the NP group demonstrated a greater variation of walking patterns during the midstance and swing phases and displayed altered compensatory gait. Clinicians need to consider the similarities of the kinematic changes for the NP group to aid in detection of limb motion differences and the resulting gait dysfunction. [ABSTRACT FROM AUTHOR]

Background: The Rizzoli Foot Model (RFM) and Oxford Foot Model (OFM) are used to analyze segmented foot kinematics with independent tracking markers. Alternatively, rigid marker clusters can be used to improve markers' visualization and facilitate analyzing shod gait.Research Question: Are there differences in angles from the RFM and OFM, obtained with independent and clustered tracking markers, during the stance phase of walking?Methods: Walking kinematics of 14 non-disabled participants (25.2 years (SD 2.8)) were measured at self-selected speed. Rearfoot-shank and forefoot-rearfoot angles were measured from two models with two tracking methods: RFM, OFM, RFM-cluster, and OFM-cluster. In RFM-cluster and OFM-cluster, the rearfoot and forefoot tracking markers were rigidly clustered, fixed on rods' tips attached to a metallic base. Statistical Parametric Mapping (SPM) One-Way Repeated Measures ANOVAs and SPM Paired t-tests were used to compare waveforms. Coefficients of Multiple Correlation (CMC) quantified the similarity between waveforms. One-way Repeated Measures ANOVAs were conducted to compare the ranges of motion (ROMs), and pre-planned contrasts investigated differences between the models and tracking methods. Intraclass Correlation Coefficients (ICC) were computed to verify the similarity between ROMs.Results: Differences occurred mostly in small parts of the stance phase for the cluster vs. non-cluster comparisons and the RFM vs. OFM comparisons. ROMs were slightly different between the models and tracking methods in most comparisons. The curves (CMC ≥ 0.71) were highly similar between the models and tracking methods. The ROMs (ICC ≥ 0.67) were moderatetly to highly similar in most comparisons. RFM vs. RFM-cluster (forefoot-rearfoot angle - transverse plane), OFM vs. OFM-cluster and RFM vs. OFM (forefoot-rearfoot angle - frontal plane) were not similar (non-significant).Significance: Rigid clusters are an alternative for tracking rearfoot-shank and forefoot-rearfoot angles during the stance phase of walking. However, specific differences should be considered to contrast results from different models and tracking methods. [ABSTRACT FROM AUTHOR]

Background: Cadaveric models demonstrate that failure of hip capsular repair is dependent on the robustness of the repair construct. In vivo data on capsular repair construct efficacy are limited. We investigated the effect of a figure-of-8 capsular repair on hip distraction resistance relative to native and post-capsulotomy states. We hypothesized that an unrepaired capsulotomy would demonstrate increased axial distraction compared with the native state and that capsular repair would restore distraction resistance to native levels.Methods: Patients undergoing primary hip arthroscopy by a single surgeon were prospectively enrolled between March 2020 and June 2020. Prior to any instrumentation, fluoroscopic images of the operative hip were obtained at 12.5-lbs (5.7-kg) traction intervals, up to 100 lbs (45.4 kg). Anterolateral, modified anterior, and distal anterolateral portals were established. Following interportal capsulotomy, labral repair, and osteochondroplasty, fluoroscopic images were reobtained at each traction interval. Capsular repair was performed with use of a figure-of-8 suture configuration. Traction was reapplied and fluoroscopic images were again obtained. Joint distraction distance was measured at each traction interval for all 3 capsular states. Anteroposterior pelvic radiographs were utilized to scale fluoroscopic images to obtain joint space measurements in millimeters.Results: A total of 31 hips in 31 patients were included. Capsulotomy resulted in significant increases in distraction distance from 25 (11.3 kg) to 100 lbs of traction compared with both native and capsular repair states (all comparisons, p ≤ 0.017). Capsular repair yielded a significantly greater distraction distance compared with the native state at 37.5 lbs (17.0 kg; 5.49 versus 4.98 mm, respectively; p = 0.012) and 50 lbs (22.7 kg; 6.08 versus 5.35 mm; p < 0.001). The mean difference in distraction distance between native and capsular repair states from 25 to 100 lbs of traction was 0.01 mm.Conclusions: This in vivo model demonstrates that an unrepaired interportal capsulotomy significantly increases axial distraction distance compared with the native, intact hip capsule. Performing a complete capsular closure reconstitutes resistance to axial distraction intraoperatively. Future research should evaluate the in vivo effects and associated clinical outcomes of other published capsular repair techniques and assess the durability of capsular repairs over time. [ABSTRACT FROM AUTHOR]

Introduction: The purpose of this study was to investigate sex-specific lower limb biomechanical adaptations during a standardized load carriage task in response to a targeted physical training program.Materials and Methods: Twenty-five healthy civilians (males [n = 13] and females [n = 12]) completed a load carriage task (5 km at 5.5 km·h-1, wearing a 23 kg vest) before and after a 10-week lower-body-focused training program. Kinematics and ground reaction force data were collected during the task and were used to estimate lower limb joint kinematics and kinetics (i.e., moments and powers). Direct statistical comparisons were not conducted due to different data collection protocols between sexes. A two-way repeated measures ANOVA tested for significant interactions between, and main effects of training and distance marched for male and female data, respectively.Results: Primary kinematic and kinetic changes were observed at the knee and ankle joints for males and at the hip and knee joints for females. Knee joint moments increased for both sexes over the 5 km distance marched (P > .05), with males demonstrating significant reductions in peak knee joint extension after training. Hip adduction, internal rotation, and knee internal rotation angles significantly increased after the 5 km load carriage task for females but not males.Conclusion: Differences in adaptive gait strategies between sexes indicate that physical training needs to be tailored to sex-specific requirements to meet standardized load carriage task demands. The findings highlighted previously unfound sex-specific responses that could inform military training and facilitate the integration of female soldiers into physically demanding military roles. [ABSTRACT FROM AUTHOR]

Introduction: While running is a popular activity because of the health and fitness benefits it provides, the yearly incidence of running-related injuries (RRI) is high across all populations of runners, including military members. The etiology of RRI is multifactorial, and despite the numerous studies on risk factors for RRI, there is no clear consensus in the literature on the relative contribution of several intrinsic or extrinsic risk factors to the development of RRI. Furthermore, little is known on RRI profile and running parameters among Canadian military members. The objectives of this study were to (1) describe the clinical presentation of lower limb RRI and running profile among military members and (2) explore any association between recent changes in running parameters (volume or intensity) and specific RRI diagnoses.Materials and Methods: This cross-sectional study was conducted in 107 military members from the Canadian Armed Forces (Valcartier Military Base) who presented with a restriction or interruption of running because of lower limb running-related pain. The following variables were collected during a physiotherapy evaluation: injury location and diagnosis, running kinematics (foot strike pattern and step rate), degree of minimalism of running shoes, running parameters in the last 3 months before consultation (volume, duration, frequency, and intensity), and recent changes in training before pain onset. Descriptive statistical analyses were conducted to describe the clinical presentation and running profile, while chi-square tests and multiple correspondence analysis were used to explore the association between recent changes in running parameters and diagnosis. This study was approved by the institutional ethics committee, and participants signed a detailed consent form.Results: Among the 107 participants included in the study (mean age: 30.7 ± 8.9 years; 13 females), the most common diagnoses were patellofemoral pain (26.2%), medial tibial stress syndrome (11.2%), plantar fasciopathy (9.3%), and sciatica (9.3%). The average Minimalist Index of running shoes was 27.6 ± 18.5%. Step rate was 161.7 ± 10.3 steps per minute, and 73.3% of the participants used a rearfoot strike pattern. The majority of military runners reported previous RRI, gradual onset of symptoms, and recent changes in their training parameters (75.7%) before injury onset. No association was found between recent changes in running volume ((χ2(4) = 2.849; P = .606)) or intensity ((χ2(4) = 1.381; P = .855)) and diagnosis.Conclusion: This is the first study to specifically investigate RRI and running profile among Canadian military members. The most common injuries were located at the knee, and the most frequent diagnosis was patellofemoral pain. The majority of military runners reported previous RRI as well as recent changes in their running parameters before injury onset, but unique types of recent changes were not associated with specific diagnoses. This study illustrates the need to further investigate the impact of training loads on the development of RRI. [ABSTRACT FROM AUTHOR]

Introduction: The U.S. Army conducts airborne operations in order to insert soldiers into combat. Military airborne operations are physically demanding activities with a unique loading environment compared with normal duties. A significant amount of research surrounding airborne operations has focused on assessing the incidence and type of associated injuries as well as the potential risk factors for injuries. During parachute opening shock and other high-acceleration events (e.g., fixed wing flight or vehicle crashes), the neck may be vulnerable to injury if inertial loads overcome the voluntary muscular control of the cervical spine and soft tissue structures. A recent epidemiological survey of sport skydivers showed that the neck, shoulders, and back were the most frequently reported sites of musculoskeletal pain. In addition, the survey indicated that wing loading (a measure of the jumper's weight divided by the size of the parachute canopy) was a potential contributing factor for developing musculoskeletal pain. Recently, there have been efforts to measure the severity of parachute opening shock as an additional potential risk factor for injury; however, no studies have measured both head and body accelerations and no studies have measured head or body angular rate during parachute opening shock. The purpose of this study was to measure and characterize the accelerations and angular rates of both the head and body during parachute opening shock as well as investigate potential factors contributing to higher severity opening shock, which may link to the development of musculoskeletal pain or injury.Materials and Methods: Data were collected from the U.S. Army Parachute Team, The Golden Knights, under an approved Medical Research and Material Command Institutional Review Board protocol. Subjects were instrumented with a helmet- and body-mounted sensor package, which included three angular rate sensors and three single-axis accelerometers each. Data were collected at 2,500 samples per second. Kruskal-Wallis tests were used to determine if helmet-mounted equipment (e.g., cameras), neck length, neck circumference, or wing loading (the ratio of jump weight to the size of the main parachute canopy) affected the accelerations or angular rates of the head or body.Results: A total of 54 jumps conducted by 19 experienced free-fall jumpers were analyzed. For the head, the mean (± SD) resultant accelerations and angular rates were 5.8 (± 1.6) g and 255.9 (± 74.2) degrees per second (deg/s), respectively. For the body, the resultant accelerations and angular rates were 4.3 (± 1.5) g and 181.3 (± 61.2) deg/s, respectively. A wing loading above 1.4 pounds per square foot (lb/ft2) was found to have a significant effect on head (P = .001) and body (P = .001) resultant acceleration as well as body angular rate about the Y-axis (P = .001).Conclusions: There is evidence to suggest that wing loading has an influence on individual head and body resultant accelerations. However, no significant effects were found for the other variables (e.g., neck length and circumference, helmet-mounted equipment, etc.). Future research should focus on identifying additional factors that result in changes in accelerations and angular rates of the head and body during parachute opening shock events. [ABSTRACT FROM AUTHOR]

Aim: To determine whether a running intervention utilising plyometric activities improved leg stiffness in youth with cerebral palsy (CP), GMFCS levels I and II.Method: This stratified randomised controlled trial examined the lower limb kinetics and kinematics of a sample of youths with CP during sub-maximal hopping and running, prior to and immediately following a 12-week running intervention that incorporated low load plyometric training. Included participants were 13 in the control group (mean age 13 years 2 months [SD 2 years 7 months]; six males; nine GMFCS level I; six unilateral) and 18 in the intervention group (mean age 12 years 9 months [SD 2 years 10 months]; 13 males; 11 GMFCS level I; nine unilateral). Derived variables included three-dimensional leg stiffness as well as resultant ground reaction force and change in leg length. Generalised linear mixed models were developed for statistical analysis.Results: At follow-up the intervention group had greater leg stiffness than the control group during submaximal hopping (Intervention median = 3278Nm-1; Control median = 1556Nm-1; p < 0.01). At follow-up, participants in the intervention group in GMFCS Level I had greater leg stiffness than the control group during jogging (Intervention mean=38.84 (SD=25.55); Control mean=29.38 (SD=11.11); t = 2.61 p = 0.01).Interpretation: A running training intervention which includes plyometric activities can improve leg stiffness in young people with CP, especially those in GMFCS level I. [ABSTRACT FROM AUTHOR]

Background: Functional resistance training is frequently applied to rehabilitate individuals with neuromusculoskeletal injuries. It is performed by applying resistance in conjunction with a task-specific training, such as walking. However, the benefits of this training may be limited by motor slacking, a phenomenon in which the human body attempts to reduce muscle activation levels or movement excursions to minimize metabolic- or movement-related costs. While kinematic feedback could reduce one's tendency to minimize effort during training, this has not been verified experimentally.Research Question: Does functional resistance training during walking lead to motor slacking, and can techniques such as visual feedback be used to reduce these effects?Methods: Fourteen able-bodied individuals participated in this experiment. Participants were trained by walking on a treadmill while a bidirectional resistance was applied to the knee using a robotic knee exoskeleton. During training, participants were either instructed to walk in a manner that felt natural or were provided real-time visual feedback of their kinematics. Electromyography and knee kinematics were measured to determine if adding resistance to the limb induced slacking and if feedback could reduce slacking behavior. Kinematic aftereffects were measured after training bouts to gauge adaptation.Results: Functional resistance training without feedback significantly reduced knee flexion when compared to baseline walking, indicating that participants were slacking. This reduction in knee flexion did not improve with continued training. Providing visual feedback of knee joint kinematics during training significantly increased knee muscle activation and kinematic aftereffects.Significance: The findings indicate that individuals are susceptible to motor slacking during functional resistance training, which could affect outcomes of this training. However, motor slacking can be reduced if training is provided in conjunction with a feedback paradigm. This finding underscores the importance of using additional methods that externally motivate motor adaptation when the body is not intrinsically motivated to do so. [ABSTRACT FROM AUTHOR]

Background: Walking speed is a functional vital sign affecting mechanical parameters individually. Further, there is a tendency for pathological gait to occur at slower speeds, which does not always allow for an adequate comparison with normal gait. Therefore, recognizing the influence of spatiotemporal adjustments on healthy gait can broaden our understanding of the applicability of gait quality markers.Research Question: This study aimed to identify the causal relationship between the stride length-frequency walking ratio index (R_SL/SF) at the self-selected walking speed (SSWS) and optimal walking speed (OWS) and the locomotor rehabilitation index (LRI) in healthy adults.Materials and Methods: Healthy adults (n = 68) of both sexes aged 20-59 years were included in this study. The SSWS was determined using a 30-m walkway. The OWS and LRI were predicted by equations proposed in the literature. The volunteers walked on the treadmill at speeds corresponding to the OWS and SSWS in two bouts of 60 s each, with a break in between. The spatiotemporal parameters were recorded using a high-speed digital video camera, digitalized, and mathematically processed. Multiple linear regression was applied using the forced regression method.Results: Significant correlations were found between the LRI and R_SL/SF at the SSWS (R = 0.397; p < 0.001) and OWS (R = 0.266; p = 0.014). The regression model showed that 16 % of the variability in the LRI was attributable to the R_SL/SF variability at the SSWS. The average and 95 % confidence interval LRI were 94.7 % (91.6 %-97.8 %).Conclusion: The LRI average is around 95 % for healthy and young adults and the R_SL/SF explained just 16 % of the variance in LRI. [ABSTRACT FROM AUTHOR]

Introduction: Rocker profile shoes with a proximally placed apex are currently one of the most prescribed shoe modifications for treatment and prevention of lower leg deficits. Three geometrical rocker design parameters apex position (AP), apex angle (AA) and rocker radius (RR) influence both plantar pressure redistribution and kinetic and kinematic alterations of the lower leg. In addition, longitudinal bending stiffness (LBS) of the outsole influences these parameters as well. This study aims to investigate the effects of the LBS in combination with different forefoot radii of rocker shoes on kinematics and kinetics of the lower limb.Methods: 10 participants walked in standard shoes and six experimental shoe conditions with high and low LBS and three different forefoot rocker radii with the same (proximal) AP and AA. Lower extremity kinematics and kinetics were collected while walking on an instrumented treadmill at preferred walking speed and analysed with a repeated measures ANOVA and Statistical Parametric Mapping (SPM) (α = .05; post hoc α = .05/6).Results: SPM analyses revealed no significant differences for LBS and interaction LBS*RR for most research variables in terminal stance (ankle angle, ankle moment, ankle power, foot-to-horizontal angle, shank-to-vertical angle, external ankle moment, ground reaction force angle). A significant LBS effect was found for anterior-posterior position of the centre of pressure during pre-swing and peak ankle dorsiflexion angle. No relevant significant differences were found in spatio-temporal parameters and total work at the ankle between low and high LBS.Conclusion: This study showed that longitudinal bending stiffness does not affect the biomechanical working mechanism of rocker profile shoes as long as toe plantarflexion is restricted. Providing that the forefoot rocker radius supports at least a normal foot-to-horizontal angle at toe-off, there is no reason to increase sole stiffness to change ankle kinematics and kinetics. [ABSTRACT FROM AUTHOR]

Background: Understanding the kinematic characteristics of relapse clubfoot compared to successfully treated clubfoot could aid early identification of a relapse and improve treatment planning. The usage of a multi segment foot model is essential in order to grasp the full complexity of the multi-planar and multi-joint deformity of the clubfoot.Research Question: The purpose of this study was to identify differences in foot kinematics, using a multi-segment foot model, during gait between patients with Ponseti treated clubfoot with and without a relapse and age-matched healthy controls.Methods: A cross-sectional study was carried out including 11 patients with relapse clubfoot, 11 patients with clubfoot and 15 controls. Gait analysis was performed using an extended Helen Hayes model combined with the Oxford Foot Model. Statistical analysis included statistical parametric mapping and discrete analysis of kinematic gait parameters of the pelvis, hip, knee, ankle, hindfoot and forefoot in the sagittal, frontal and transversal plane.Results: The relapse group showed significantly increased forefoot adduction in relation with the hindfoot and the tibia. Furthermore, this group showed increased forefoot supination in relation with the tibia during stance, whereas during swing increased forefoot supination in relation with the hindfoot was found in patients with relapse clubfoot compared with non-relapse clubfoot.Significance: Forefoot adduction and forefoot supination could be kinematic indicators of relapse clubfoot, which might be useful in early identification of a relapse clubfoot. Subsequently, this could aid the optimization of clinical decision making and treatment planning for children with clubfoot. [ABSTRACT FROM AUTHOR]

Background: Individuals with chronic ankle instability (CAI) exhibit altered vertical ground reaction forces (vGRF), a laterally shifted center of pressure, and an inverted foot position during walking. These neuromechanical alterations are linked with altered ankle joint loading in this population. Vibration-based gait retraining improves center of pressure positioning but effects on neuromechanical variables influencing joint loading remains unknown.Research Question: Do patients with CAI exhibit altered vGRF and ankle joint contact forces (JCF) after receiving a single session of vibration-based gait retraining?Methods: Ten individuals with CAI underwent a single session of vibration-based gait retraining. Kinematic and kinetic data were collected during walking on an instrumental treadmill with force plates embedded in it. Following a baseline gait assessment without feedback, participants walked at a self-selected speed for 10 minutes while receiving feedback. Data was collected during an early (1 st and 2 nd minute) and late adaptation phase (9 th and 10 th minute) and, compared to baseline values. Impact and propulsive vGRF variables (i.e. peak, time to peak, and loading rate) were obtained. Musculoskeletal modeling was used to calculate ankle JCF variables (peak, impulse, and loading rate) during stance phase.Results: Propulsive vGRF and ankle JCF outcomes were significantly reduced during the early and late adaptation phases (p ≤ 0.039).Significance: These results indicate that vibration-based gait retraining can immediately reduce propulsive vGRF and ankle JCF and may represent a modality that could help restore appropriate ankle joint loading patterns in those with CAI. [ABSTRACT FROM AUTHOR]

Background: Increasing cadence in running has been advocated as a means to improve performance and reduce impact forces. Although acoustic pacing can be used for this purpose, it might by itself lead to an increased impact force, which would counteract the decrease in impact force that is being pursued by increasing the cadence with acoustic pacing and thus have a counterproductive effect.Research Question: What are the effects of acoustic pacing and cadence on peak impact force and loading rate during running?Methods: Unpublished data from a previous study, in which 16 participants ran on an instrumented treadmill with various forms of acoustic pacing, were analyzed to address the research question. Peak impact force and loading rate while running with and without pacing, at three different cadences were extracted from the ground reaction force data and compared statistically between these two main conditions. In addition, we compared step-based and stride-based pacing, and paced and unpaced steps within stride-based pacing conditions.Results: As expected, increasing the cadence was accompanied by a significant reduction in peak impact force and instantaneous vertical loading rate, whereas acoustic pacing had no significant effect on the impact forces compared to unpaced running with similar cadence, both before and after pacing. There were also no significant differences in this regard between step-based and stride-based pacing.Significance: Acoustic pacing does not adversely affect impact force when used to increase cadence in running with the aim of reducing the impact force and can thus be used for this purpose without introducing a counterproductive effect. [ABSTRACT FROM AUTHOR]

Background: Despite strong evidence that walking speed and forward propulsion decline with increasing age, their relationship is still poorly understood. While changes in the ankle and hip mechanics have been described, few studies have reported the effect of ageing on the whole leg's contribution to propulsion.Research Question: The aim of this study was to investigate age-related changes in the work performed by the leg on the center of mass (COM) push-off power during walking in adults aged 20-86 years. Specifically, we evaluated how deterioration in COM push-off power relates to changes in ankle and hip kinetics as well as age and walking speed.Methods: Motion, ground reaction forces and gastrocnemius muscle activity were recorded in 138 adults during overground walking at self-selected speed. Age-related differences in variables between decades were analyzed with an ANOVA, while the relation between COM push-off power and joint kinetic variables, as well as walking speed and biological age, was evaluated using correlations and multiple regression analysis.Results: From the age of 70 years and onwards, COM push-off power was significantly decreased. The decline in COM push-off power was mostly explained by a decline in average ankle push-off power (72 %), and to a lesser extent by peak hip extension moment (3 %). There was no re-distribution of ankle-to-hip push-off power. The decline in COM push-off power seemed more related to walking speed (explaining 54 % of the variance) than biological age (only 4 %).Significance: Findings indicate that age-related decline in COM push-off power in able-bodied adults starts from the age of 70 years, which is before changes have been found in kinematics, but still later than generally presumed. This decrease in push-off power was more related to walking speed than biological age, which emphasizes the need to better understand the reason for speed decline in older adults. [ABSTRACT FROM AUTHOR]

Background: Although functional methods determining the hip joint center (HJC) are becoming increasingly popular, no systematic investigation has been conducted yet to assess the reliability of functional hip joint calibration in patients with cerebral palsy (CP).Research Question: What is the most reliable way to conduct functional calibration motions for estimating HJC location in children with CP and movement disorders?Methods: Twenty-two patients with CP were included in the study. A marker set for Plug-in Gait with additional cluster markers was used. Two functional calibration movements, including a new movement, were proposed and tested with one and three repetitions each. Functional HJCs were determined using the SCoRE approach and compared to results obtained by applying the conventional regression method for assessing face validity.Results: The choice of calibration movement had significant impact on SCoRE residuals and HJC location. Increasingly repeating calibration movements did not improve results. A modified star movement by allowing the toes to tip the ground provided the most reliable data and is feasible for children with GMFCS level I-III. The feasibility of the method is further improved by analyzing hip motion in the contralateral stance limb and, among the calibration movements, gave the most precise HJC estimation.Significance: Type and performance of the functional calibration movement is one key factor for determining a robust HJC. Analyzing the data in the stance leg via the modified star motion yielded robust and reasonable results for the HJC location, which should be validated in further studies that include imaging methods. Using one repetition instead of three seems promising in terms of feasibility for patients with movement disorder. [ABSTRACT FROM AUTHOR]

Background: The analysis of biomechanical parameters derived from the body center of mass (BCoM) 3D motion allows for the characterization of gait impairments in people with lower-limb amputation, assisting in their rehabilitation. In this context, magneto-inertial measurement units are promising as they allow to measure the motion of body segments, and therefore potentially of the BCoM, directly in the field. Finding a compromise between the accuracy of computed parameters and the number of required sensors is paramount to transfer this technology in clinical routine.Research Question: Is there a reduced subset of instrumented segments (BSN) allowing a reliable and accurate estimation of the 3D BCoM acceleration transfemoral amputees?Methods: The contribution of each body segment to the BCoM acceleration was quantified in terms of weight and similarity in ten people with transfemoral amputation. First, body segments and BCoM accelerations were obtained using an optoelectronic system and a full-body inertial model. Based on these findings, different scenarios were explored where the use of one sensor at pelvis/trunk level and of different networks of segment-mounted sensors for the BCoM acceleration estimation was simulated and assessed against force plate-based reference acceleration.Results: Trunk, pelvis and lower-limb segments are the main contributors to the BCoM acceleration in transfemoral amputees. The trunk and shanks BSN allows for an accurate estimation of the sagittal BCoM acceleration (Normalized RMSE ≤ 13.1 %, Pearson's correlations r ≥ 0.86), while five segments are necessary when the 3D BCoM acceleration is targeted (Normalized RMSE ≤ 13.2 %, Pearson's correlations r ≥ 0.91).Significance: A network of three-to-five segments (trunk and lower limbs) allows for an accurate estimation of 2D and 3D BCoM accelerations. The use of a single pelvis- or trunk-mounted sensor does not seem advisable. Future studies should be performed to confirm these results where inertial sensor measured accelerations are considered. [ABSTRACT FROM AUTHOR]

Background: Previous work has linked the eccentricity of the net ground reaction force (GRFnet) to increased mediolateral instability during single-step voluntary and compensatory stepping responses. The present work sought to understand the extent to which such control mechanisms for mediolateral stability are present during gait.Research Question: How do gait velocity and step width constraints influence the kinetic control of mediolateral stability control among healthy participants?Methods: 25 participants performed three walking conditions - normal walking with self-selected speed and foot-placement, fast walking with self-selected foot-placement, and narrowbase walking - across a 10-meter walkway. Lateral instability was quantified by the mediolateral margin of stability (MoSML). The frontal-plane eccentricity of the GRFnet was calculated as the difference between GRFnet vector orientation and that of a line joining the coordinates of COPnet and COM. Two discrete time-points (P1 and P2) following foot-contact were examined, as they have been suggested to be indicative of proactive and reactive COM control, respectively. Task-related differences in the magnitude and timing of kinematic and kinetic outcome variables were analysed using one-way ANOVAs with repeated-measures.Results: With constraints on step-width in narrow-base walking, participants exhibited reduced stability as evidenced by reduced MoSML, alongside reductions in the peak GRFnet eccentricity (θd) at P1. Participants exhibited no reduction in stability during fast walking, as revealed by the MoSML in part because of a similar onset of P1 within the gait cycle. P2 magnitude was larger in narrow-base walking relative to fast-walking, and occurred at an earlier point in the gait cycle.Significance: Findings suggest proactive mechanisms (i.e. P1) may predominantly regulate mediolateral stability during walking. Reactive mechanisms (i.e. P2), however, may be capable of offsetting instability in situations where proactive mechanisms are insufficient. [ABSTRACT FROM AUTHOR]

Background: Prostheses can help persons with trans-femoral amputation (TFA) regain normal function, but such individuals still exhibit gait deviations expressed in gait asymmetries. We apply a specialised tool, the Symmetry Function (SF), to evaluate the symmetry of walking in terms of kinematic and dynamic variables and to identify areas with large side deviations (exceeding defined ±5% threshold) in the movement cycle.Research Question: Which movements and joints or GRF components revealed the most significant side deviations in the movement cycle? When exactly are they located in the gate cycle?Methods: In this retrospective observational study, an instrumented motion analysis system was used to register the gait of fourteen patients after unilateral TFA. Measurements involved evaluating the time series of gait variables characterising a range of motion and the ground reaction force components. Comparison of the prosthetic (involved) limb with the sound (uninvolved) limb in TFA patients was carried out on the basis of the Symmetry Function values.Results: The Symmetry Function proved to be an effective tool to localise the regions of asymmetry and limb dominance in the full gait cycle. The difference between sides revealed by the Symmetry Function was the highest for the pelvis and the hip. In the sagittal plane, the pelvis was asymmetrically tilted, reaching the highest SF value of more than 25 % at 60 % cycle time. In the transverse plane, the pelvis was even more asymmetrically positioned throughout the entire gait cycle (50 % difference). The hip in the frontal plane reached a 60 % difference throughout the single support phase for the involved and then for the uninvolved limb.Significance: The Symmetry Function allows for the detection of gait asymmetries, temporal shifts in the gait phases and may assess the precise in time adaptation of prostheses and rehabilitation monitoring, especially in unilateral impairments. [ABSTRACT FROM AUTHOR]

Background: While gait termination is challenging for children with spastic cerebral palsy (CCP), few studies have quantitatively assessed this issue.Research Question: What are the characteristics of center of mass (COM) and center of pressure (COP) displacement during gait termination in CCP, and how do they compare with those in children with typical development (CTD)?Methods: This cross-sectional study included 13 adults with typical development (19.85 ± 0.52 years), 12 CTD (10.41 ± 2.98 years), and 16 CCP (11.15 ± 2.71 years). Participants were instructed to immediately stop walking when a stop sign appeared on a screen, which was placed at the end of an 8-m walkway. COM and COP were determined via 3-dimensional motion analysis and force plate data. Differences between the groups were assessed using the two sample t-test or Wilcoxon rank sum test. The level of statistical significance was set at P < 0.05.Results: The normalized time for stopping in CCP (4.556 ± 0.602) was higher than that in CTD (3.617 ± 0.545, P < 0.001). The normalized COP displacement (P < 0.001) and divergence between COM and COP (P < 0.001) in the mediolateral (ML) direction were significantly higher in CCP than CTD. However, the normalized divergence between COM and COP in the anteroposterior (AP) direction in CCP was lower than that in CTD (P = 0.034).Significance: The more minor divergence between COM and COP in the AP direction and the more significant COP displacement in the ML direction cause difficulty to exert braking force during gait termination. Thus, CCP require a longer time for gait termination. This finding may facilitate the development of interventions for improving gait in CCP. [ABSTRACT FROM AUTHOR]

Rationale: Prolonged mechanical ventilation (MV) is often associated either with a decrease (known atrophy) or an increase (supposed injury) in diaphragmatic thickness. Shear wave elastography is a non-invasive technique that measures shear modulus, a surrogate of tissue stiffness and mechanical properties.Objectives: To describe changes in shear modulus (SM) during the ICU stay and the relationship with alterations in muscle thickness. To perform a comprehensive ultrasound-based characterization of histological and force production changes occurring in the diaphragm.Methods: Translational study using critically ill patients and mechanically ventilated piglets. Serial ultrasound examination of the diaphragm collecting thickness and SM was performed in both patients and piglets. Transdiaphragmatic pressure and diaphragmatic biopsies were collected in piglets.Measurements and Main Results: We enrolled 102 patients, 88 of whom were invasively mechanically ventilated. At baseline, SM was 14.3+/-4.3 kPa and diaphragm end-expiratory thickness was 2.0+/-0.5 mm. Decrease or increase by more than 10% from baseline was reported in 86% of the patients for thickness and in 92% of the patients for shear modulus. An increase in diaphragmatic thickness during the stay was associated with a decrease in SM (β=-9.34±4.41; p=0.03) after multivariable analysis. In the piglet sample, a decrease in SM over 3 days of MV was associated with loss of force production, slow and fast fiber atrophy and increased lipid droplets accumulation.Conclusions: Increases in diaphragm thickness during critical illness is associated with decreased tissue stiffness as demonstrated by shear wave ultrasound elastography, consistent with the development of muscle injury and weakness. [ABSTRACT FROM AUTHOR]

Purpose: Root fracture is a common and serious cause of abutment tooth loss. No studies to date have comprehensively assessed the individual contributions of the factors that increase stress on abutment teeth. The purpose of this study was to analyze the stress distribution in abutment teeth based on a three-dimensional finite element model and to analyze the factors that affect stress distribution.Materials and Methods: Models were generated from the computed tomography data of a single patient, consisting of a mandibular second premolar abutment tooth, bone, residual mucous membrane, and a partial removable dental prosthesis (PRDP). Four models were prepared using different types of endodontic posts and cores. Akers clasps were used for the simulated PRDPs, and a vertical load was applied to the occlusal surface of the PRDPs. Debonding between the post and root was simulated. The Young modulus of the residual ridge was reduced to simulate a poor fit between the denture base and the residual ridge. Stress distribution in the abutment tooth root was observed, and the maximum principal stress was evaluated.Results: The nonmetal post model and the mesial rest model reduced stress concentration in the root. The stress increased in models simulating debonding and poor fit. The results of the multiple linear regression analysis confirmed that debonding and poor fit were significantly associated with root stress.Conclusion: Within the limitations of this study, it is suggested that the bonding integrity of posts and adequate fit of the denture base are important factors affecting the longevity of abutment teeth for PRDPs. [ABSTRACT FROM AUTHOR]

Background: While running, the human body absorbs repetitive shocks with every step. These shocks can be quantified by the peak vertical ground reaction force (Fv,max). To measure so, using a force plate is the gold standard method (GSM), but not always at hand. In this case, a motion capture system might be an alternative if it accurately estimates Fv,max.Research Question: The purpose of this study was to estimate Fv,max based on motion capture data and validate the obtained estimates with force plate-based measures.Methods: One hundred and fifteen runners participated at this study and ran at 9, 11, and 13 km/h. Force data (1000 Hz) and whole-body kinematics (200 Hz) were acquired with an instrumented treadmill and an optoelectronic system, respectively. The vertical ground reaction force was reconstructed from either the whole-body center of mass (COM-M) or sacral marker (SACR-M) accelerations, calculated as the second derivative of their respective positions, and further low-pass filtered using several cutoff frequencies (2-20 Hz) and a fourth-order Butterworth filter.Results: The most accurate estimations of Fv,max were obtained using 5 and 4 Hz cutoff frequencies for the filtering of COM and sacral marker accelerations, respectively. GSM, COM-M, and SACR-M were not significantly different at 11 km/h but were at 9 and 13 km/h. The comparison between GSM and COM-M or SACR-M for each speed depicted root mean square error (RMSE) smaller or equal to 0.17BW (≤6.5 %) and no systematic bias at 11 km/h but small systematic biases at 9 and 13 km/h (≤0.09 BW). COM-M gave systematic biases three times smaller than SACR-M and two times smaller RMSE.Significance: The findings of this study support the use of either COM-M or SACR-M using data filtered at 5 and 4 Hz, respectively, to estimate Fv,max during level treadmill runs at endurance speeds. [ABSTRACT FROM AUTHOR]

Background: Patients with hip osteoarthritis (OA) exhibit an increased step width (SW) during walking before and up to 2 years after total hip arthroplasty. Wider SW is associated with a reduction in the external knee adduction moment (KAM), but there is a lack of research regarding the effect of SW on the hip adduction moment (HAM).Research Question: Is a wider SW an effective compensatory mechanism to reduce the hip joint loading? We hypothesized that (1) an increased SW reduces, (2) a decreased SW increases the KAM/HAM, and (3) secondary kinematic gait changes have an effect on the KAM/HAM.Methods: Twenty healthy individuals (24.0 ± 2.5 years of age) underwent instrumented gait analyses with 4 different subject-specific SW modifications (habitual, halved, double, and triple SW). The resulting external KAMs and HAMs were compared using statistical parametric mapping (SPM).Results: Post hoc testing demonstrated significantly lower HAM for both the double (p < 0.001, 15-31 % and 61-98 % of the stance phase) and the triple SW (p < 0.001, 1-36 % and 58-98 %) compared to the habitual SW. The extent of the reduction at the first and second peak was comparable for HAM (15-25 % reduction) and less pronounced at the first peak of KAM (9-11 % reduction) compared to the second peak of KAM (19-28 % reduction). In contrast, halving the SW did not lead to a significant change in KAM or HAM compared to the habitual SW (p > 0.009).Significance: An increase in SW is an effective and simple gait mechanism to reduce the frontal plane knee and hip joint moments. However, hypothesis 2 could not be confirmed, as halving the SW did not cause a significant change in KAM or HAM. Given the results of the present study, gait retraining with regard to an increased SW may be an adequate, noninvasive option for the treatment of patients with hip OA. [ABSTRACT FROM AUTHOR]

Background: Not all pregnant women seem to select the more curved lumbopelvic posture that their sexual dimorphic anatomy allows even though many previous researchers have assumed lumbopelvic curvature to be standard during pregnancy. This study is vital to understanding coevolution of lumbopelvic sexual dimorphism and bipedalism, and understanding some clinical implications of intervening in gestational posture changes.Research Questions: Are there anthropometric changes that correspond with selection of lumbopelvic curvature change during pregnancy? What are the biomechanical costs and benefits of gestational lumbopelvic curvature change?Methods: Twenty pregnant women were tested at five different times in the 2nd and 3rd trimesters of pregnancy. Lumbopelvic posture, standing kinetics and gait kinetics were measured longitudinally. Additionally, we modeled the effects on standing and gait without lumbopelvic postural changes, but with anthropometric changes, for each individual.Results: We found greater lumbopelvic angulation to correspond with a shorter body height (6 cm difference between groups, p = 0.048) and deeper 2nd trimester abdomen (2 cm difference between groups, p = 0.013). Lumbopelvic angulation lowers support requirements (in standing and walking (6% lower support impulse, p = 0.056), but at the cost of shifting the propulsive actions to a less efficient pulling action rather than pushoff (13 % reduction in pushoff time, p = 0.001). We observed minimal effects on walking kinematics and balance control.Significance: Our findings suggest the evolutionary advantage of the female lumbopelvic unit is the adaptability it provides to adjust for the individual needs of the pregnant woman. We discuss multiple potential contributing factors that may have shaped hominin female lumbopelvic evolution and are involved in self-selecting lumbopelvic posture. [ABSTRACT FROM AUTHOR]

Background: Females are two times more likely to develop patellofemoral pain (PFP) than males. Abnormal trunk and pelvis kinematics are thought to contribute to the pathomechanics of this condition. However, there is a scarcity of evidence investigating proximal segments kinematics in females with PFP.Research Question: The purpose of this study was to investigate whether females with PFP demonstrate altered trunk, pelvis, and knee joint kinematics compared with healthy controls during running.Methods: Thirty-four females (17 PFP, 17 controls) underwent a 3-dimensional motion analysis during treadmill running at preferred and fixed speeds, each trial for 30 s. Variables of interest included magnitudes of peak angles for trunk (forward flexion, ipsilateral trunk lean), pelvis (anterior tilt, contralateral drop), knee (flexion, valgus, internal rotation), range of motion (RoM) of trunk and pelvis in sagittal and frontal planes and RoM of knee joint in the three cardinal planes of motion. Kinematic data were compared between groups using mixed model repeated measure analysis of variance with the trial as the repeated measure.Results: The PFP group displayed significantly less pelvis frontal plane RoM, greater knee frontal plane RoM, and less knee sagittal plane RoM during running compared with controls, irrespective of running trial. No differences were found in peak kinematic variables between PFP and healthy groups.Significance: These results may suggest a rigid stabilization strategy at the pelvis, which the body has adapted to prevent further frontal plane knee malalignment. Less knee sagittal plane RoM may be indicative of another protective strategy in the PFP group to avoid patellofemoral joint reaction force. Clinical assessments and rehabilitative treatments may benefit from considering a global program with focus on pelvis kinematics in addition to the knee joint in females with PFP. [ABSTRACT FROM AUTHOR]

Background: Individuals with lower limb loss are at an increased risk for falls, likely due to impaired balance control. Standing balance is typically explained by double- or single-inverted pendulum models of the hip and/or ankle, neglecting the knee joint. However, recent work suggests knee joint motion contributes toward stabilizing center-of-mass kinematics during standing balance.Research Question: To what extent do hip, knee, and ankle joint motions contribute to postural sway in standing among individuals with lower limb loss?Methods: Forty-two individuals (25 m/17f) with unilateral lower limb loss (30 transtibial, 12 transfemoral) stood quietly with eyes open and eyes closed, for 30 s each, while wearing accelerometers on the pelvis, thigh, shank, and foot. Triaxial inertial measurement units were transformed to inertial anterior-posterior components and sway parameters were computed: ellipse area, root-mean-square, and jerk. A state-space model with a Kalman filter calculated hip, knee, and ankle joint flexion-extension angles and ranges of motion. Multiple linear regression predicted postural sway parameters from intact limb joint ranges of motion, with BMI as a covariate (p < 0.05).Results: With eyes open, intact limb hip flexion predicted larger sway ellipse area, whereas hip flexion and knee extension predicted larger sway root-mean-square, and hip flexion, knee extension, and ankle plantarflexion predicted larger sway jerk. With eyes closed, intact limb hip flexion remained the predictor of sway ellipse area; no other joint motions influenced sway parameters in this condition.Significance: Hip, knee, and ankle motions influence postural sway during standing balance among individuals with lower limb loss. Specifically, increasing intact-side hip flexion, knee extension, and ankle plantarflexion motion increased postural sway. With vision removed, a re-weighting of lower limb joint sensory mechanisms may control postural sway, such that increasing sway may be regulated by proximal coordination strategies and vestibular responses, with implications for fall risk. [ABSTRACT FROM AUTHOR]

Background: Differences in reactive stepping strategy to recover balance have been investigated as a function of age and sex, but to date have been measured using discrete step or joint specific measures. It is unknown how whole-body strategy or underlying motor control objectives differ between age and sex groups in forward reactive stepping.Research Question: Does whole-body movement and/or motor control strategy differ as a function of age or sex in a forward reactive step to maintain balance?Methods: Forty young and older adults (45 females, 35 males) participated in this study. All participants performed five reactive stepping trials in response to a forward balance perturbation while whole-body kinematics and ground reaction forces were collected. Features of whole-body movement strategy were determined using a principal component analysis model. Average principal component (PC) scores were compared between groups as a measure of whole-body movement strategy and within participant relative standard deviation of PC scores were compared to determine if motor control objectives differed across groups.Results: Significant differences in reactive stepping strategy were observed both as a function of age and sex. Older adults had a greater step length and width, greater anterior trunk and pelvis translation, greater knee flexion angles and anterior translation of the hip joint on the stepping leg compared to young participants. Males had lesser step length and width, as well as greater trunk flexion compared to females. No differences in relative standard deviation of PC scores were observed between age or sex-based groups suggesting that motor control objectives were similar between groups.Significance: This study demonstrates how whole-body movement strategy differs as a function of age and sex, which explains why previously reported discrete outcomes occur. Additionally, it does not seem that motor control strategy objectives differ between age or sex groups in forward reactive stepping. [ABSTRACT FROM AUTHOR]

Background: Lower limb assistive devices have been developed to help amputees or stroke patients. To precisely mimic the required function, researchers focused on how to estimate/predict the required knee angle for knee devices.Research Question: The objective is to estimate the motion of the human knee joint during walking using the kinematics of wearer's thigh measured by a single Inertial Measurement Unit (IMU). The hypotheses are that the proposed method can precisely estimate knee angle and have good universality on different subjects, speeds and strides.Method: 8 healthy subjects walked on the level ground at three different speeds. An IMU mounted on the thigh was employed to collect the kinematic information of the thigh including angular velocities and accelerations. A long short-term memory (LSTM) neural network model was adopted to model intra-limb synergy between the motion of thigh and the knee joint. Such that with the trained LSTM model, the knee angle can be precisely predicted.Results: Compared with the existing studies, the proposed approach based on an LSTM model has better estimation performance. The average RMSE for eight subjects can be limited to 3.89°. The proposed method has speed and stride adaptability.Significance: The proposed method is promising to generate a desired and harmonious knee trajectory in line with thigh motion for assistive robotic devices. [ABSTRACT FROM AUTHOR]

Background: The conventional gait model (CGM) is commonly utilised within clinical motion analysis but has a number of inherent limitations. To overcome some of these limitations modifications have been made to the CGM and six-degrees of freedom models (6DoF) have been developed.Research Question: How comparable are lower limb kinematics calculated using modified CGM and 6DoF models and what is the error associated with the output of each model during walking?Methods: Ten healthy males attended two gait analysis sessions, in which they walked at a self-selected pace, while a 10-camera motion capture system recorded lower limb kinematics. Hip, knee and ankle joint kinematics in all three anatomical planes were calculated using a modified CGM, with medial anatomical markers and a three-dimensional foot added, and 6DoF. Mean absolute differences were calculated on a point-by-point basis over the walking gait cycle and interpreted relative to a 5° threshold to explore the comparability of model outputs. The standard error of the measurement (SEM) was also calculated on a point-by-point basis over the walking gait cycle for each model.Results: Mean absolute differences above 5° were reported between the two model outputs in 58-86% of the walking gait cycle at the knee in the frontal plane, and over the entire walking gait cycle at the hip and knee in the transverse plane. SEM was typically larger for the modified CGM compared to the 6DoF, with the highest SEM values reported at the knee in the frontal plane, and the hip and the knee in the transverse plane.Significance: Caution should be taken when looking to compare findings between studies utilising modified CGM and 6DoF outside of the sagittal plane, especially at the hip and knee. The reduced SEM associated with the 6DoF suggests this modelling approach may be preferable. [ABSTRACT FROM AUTHOR]

Objective: The objective of this study was to improve head-neck kinematic predictions of a contemporary finite element (FE) head-neck model, assessed in rear impact scenarios (3-10 g), by including an accurate representation of the skin, adipose tissue, and passive muscle mechanical properties. The soft tissues of the neck have a substantial contribution to kinematic response, with the contribution being inversely proportional to the impact severity. Thus accurate representation of these passive tissues is critical for the assessment of kinematic response and the potential for crash induced injuries. Contemporary Human Body Models (HBMs) often incorporate overly stiff mechanical properties of passive tissues for numerical stability, which can affect the predicted kinematic response of the head and neck.Methods: Soft tissue material properties including non-linearity, compression-tension asymmetry, and viscoelasticity were implemented in constitutive models for the skin, adipose, and passive muscle tissues, based on experimental data in the literature. A quasi-linear viscoelastic formulation was proposed for the skin, while a phenomenological hyper-viscoelastic model was used for the passive muscle and adipose tissues. A head-neck model extracted from a contemporary FE HBM was updated to include the new tissue models and assessed using head rotation angle for rear impact scenarios (3 g, 7 g, and 10 g peak accelerations), and compared to postmortem human surrogate (PMHS) data for 7 g impacts.Results: The head rotation angle increased with the new material models for all three rear impact cases: (3 g: +43%, 7 g: +52%, 10 g: +71%), relative to the original model. The increase in head rotation was primarily attributed to the improved skin model, with the passive muscle being a secondary contributor to the increase in response. A 52% increase in head rotation for the 7 g impact improved the model response with respect to PMHS data, placing it closer to the experimental average, compared to the original model.Conclusions: The improved skin, adipose tissue, and passive muscle material model properties, based on published experimental data, increased the neck compliance in rear impact, with improved correspondence to published PMHS test data for medium severity impacts. Future studies will investigate the coupled effect of passive and active muscle tissue for low severity impacts. [ABSTRACT FROM AUTHOR]

Objective: Juvenile idiopathic arthritis (JIA) affects body structure and function outcomes that may increase the risk of acute joint injury. The purpose of this study was to examine single leg squat (SLS) biomechanics for youth with JIA and their healthy peers. The study design was a matched pair cohort study.Methods: Sixty-five youth (JIA n = 30; control n = 35) participated in this ethics-approved study. Participants performed 3 sets of 5 consecutive SLS tasks. Disease activity and functional status were assessed using the Juvenile Arthritis Disease Activity Score and Child Health Assessment Questionnaire. Indexed (most-affected leg [JIA]; dominant leg [control]) and contralateral extremity biomechanics were obtained using a 12-camera system. Outcomes included hip flexion/extension (FE), adduction/abduction (AA), and internal/external (IE) rotation range of motion (ROM). Data were analyzed using a multivariate random coefficient model in R (α⍺ = 0.05).Results: A total of 29 matched pairs were analyzed. Youth with JIA had low disease activity and performed the SLS with a more internally rotated hip (indexed leg P = 0.023, β = -1.9°). Female participants displayed greater hip FE (indexed leg P = 0.015, β = -4.3°; contralateral leg P = 0.005, β = -4.8°) and IE ROM (indexed leg P = 0.021, β = -2.1°) than male participants. Associations were observed for body mass index and hip IE ROM (contralateral leg P = 0.001, β = -0.4°), knee flexion angle, and hip FE ROM (indexed leg P = 0.001, β = 0.4°; contralateral leg P = 0.001, β = 0.5°) and AA (indexed leg P = 0.010, β = 0.1°; contralateral leg P = 0.002, β = 0.2°).Conclusion: This study identified functional alterations for an SLS in youth with JIA. These findings support the use of physical therapy as part of a multidisciplinary management approach, to restore normal hip posture and movement. [ABSTRACT FROM AUTHOR]

Objective: To compare the frequency of joint and tendon disease on ultrasound (US) and clinical examination, and to investigate agreement between US and clinical evaluation in ankles with clinically active juvenile idiopathic arthritis (JIA).Methods: US and clinical evaluation were performed independently in the joint and tendon compartments of 105 ankles. Gray-scale (GS) US and power Doppler (PD) US joint abnormalities were scored on a 4-point semiquantitative scale. A joint with a GS score ≥2 and/or a PD score ≥1 was defined as active on US. Agreement was tested using kappa statistics.Results: A total of 163 joints in 89 ankles had active synovitis on US. The tibiotalar (TT) joint was the most commonly affected joint on US and on clinical evaluation. The intertarsal (IT) joint and the subtalar (ST) joint were the second in frequency on US and on clinical evaluation, respectively. Tenosynovitis was found more commonly on US than on clinical evaluation (70.5% and 32.4%, respectively), and was more frequent in the medial and lateral than in the anterior tendon compartment. Isolated tenosynovitis was detected on US in 12 of 105 ankles. Agreement between US and clinical evaluation for detection of active synovitis and tenosynovitis was less than acceptable (κ <0.4). No correlation was found between any feature of active disease recorded on clinical evaluation (joint swelling, tenderness/pain on motion, and restricted motion) and active synovitis on US in the TT joint, ST joint, and IT joint.Conclusion: Coupling clinical evaluation with US aids in correctly localizing pathology. US training of practitioners is recommended to manage ankle disease in JIA. [ABSTRACT FROM AUTHOR]

Background: Due to disrupted motor and proprioceptive function, lower limb amputation imposes considerable challenges associated with balance and greatly increases risk of falling in presence of perturbations during walking. The aim of this study was to investigate dynamic balancing responses in unilateral transtibial amputees when they were subjected to perturbing pushes to the pelvis in outward direction at the time of foot strike on their non-amputated and amputated side during slow walking.Methods: Fourteen subjects with unilateral transtibial amputation and nine control subjects participated in the study. They were subjected to perturbations that were delivered to the pelvis at the time of foot strike of either the left or right leg. We recorded trajectories of center of pressure and center of mass, durations of in-stance and stepping periods as well as ground reaction forces. Statistical analysis was performed to determine significant differences in dynamic balancing responses between control subjects and subjects with amputation when subjected to outward-directed perturbation upon entering stance phases on their non-amputated or amputated sides.Results: When outward-directed perturbations were delivered at the time of foot strike of the non-amputated leg, subjects with amputation were able to modulate center of pressure and ground reaction force similarly as control subjects which indicates application of in-stance balancing strategies. On the other hand, there was a complete lack of in-stance response when perturbations were delivered when the amputated leg entered the stance phase. Subjects with amputations instead used the stepping strategy and adjusted placement of the non-amputated leg in the ensuing stance phase to make a cross-step. Such response resulted in significantly larger displacement of center of mass.Conclusions: Results of this study suggest that due to the absence of the COP modulation mechanism, which is normally supplied by ankle motor function, people with unilateral transtibial amputation are compelled to choose the stepping strategy over in-stance strategy when they are subjected to outward-directed perturbation on the amputated side. However, the stepping response is less efficient than in-stance response. [ABSTRACT FROM AUTHOR]

Background: Musculoskeletal (MSK) models based on literature data are meant to represent a generic anatomy and are a popular tool employed by biomechanists to estimate the internal loads occurring in the lower limb joints, such as joint reaction forces (JRFs). However, since these models are normally just linearly scaled to an individual's anthropometry, it is unclear how their estimations would be affected by the personalization of key features of the MSK anatomy, one of which is the femoral version angle.Research Question: How are the lower limb JRF magnitudes computed through a generic MSK model affected by changes in the femoral version?Methods: We developed a bone-deformation tool in MATLAB (shared at https://simtk.org/projects/bone_deformity) and used it to create a set of seven OpenSim models spanning from 2˚ femoral retroversion to 40˚ anteversion. We used these models to simulate the gait of an elderly individual with an instrumented prosthesis implanted at their knee joint (5th Grand Challenge dataset) and quantified both the changes in JRFs magnitude due to varying the skeletal anatomy and their accuracy against the correspondent in vivo measurements at the knee joint.Results: Hip and knee JRF magnitudes were affected by the femoral version with variations from the unmodified generic model up to 17.9 ± 4.5% at the hip and 43.4 ± 27.1% at the knee joint. The ankle joint was unaffected by the femoral geometry. The MSK models providing the most accurate knee JRFs (root mean squared error: 0.370 ± 0.068 body weight, coefficient of determination: 0.757 ± 0.104, peak error range: 0.09-0.42 body weight) were those with femoral anteversion angle closer to that measured on the segmented bone of the individual.Significance: Femoral version substantially affects hip and knee JRFs estimated with generic MSK models, suggesting that personalizing key MSK anatomical features might be necessary for accurate estimation of JRFs with these models. [ABSTRACT FROM AUTHOR]

Background: Dysfunction in peripheral and neural structure with spastic cerebral palsy (CP) causes impaired performance and stability of various behaviors. Recent progress of quantification methods for the stability properties, which is based on the uncontrolled manifold hypothesis, has been applied to various neurological disorders. A prior study revealed that the ability for purposeful regulation of stability properties is weakened with CP during finger and hand actions. Successive regulation of stability properties is crucial for human locomotion; therefore, it is imperative to quantify the changes in the intersegmental coordination as to the stable performance in CP individuals during gait.Research Question: We hypothesized that (1) Spastic CP group will show smaller step length and gait velocity with larger variability, and (2) Spastic CP group will show no changes in average stability indices for both the COM and head position stabilization, while the smaller difference between stable and unstable posture during the gait cycle.Methods: Whole-body kinematic data during walking were collected from CP and control subjects. Step length, velocity, and coefficient of variation (CV) were calculated as spatiotemporal parameters. We quantified the intersegmental stability index in time-series during gait for the stabilization of the whole-body COM and head position.Results: The CP subjects showed smaller step length and velocity with larger CV than the controls. However, the CP group showed a significantly less difference in the stability indices between the single- and double-limb support phases as compared to the controls for both the COM and head position stabilization.Significance: Present study is the first to document the quantification of changing intersegmental stability in the spastic CP during locomotion. The dysfunction of intentional modulation of stability properties in CP individuals may be a more common problem, which is not limited to a specific body effector. [ABSTRACT FROM AUTHOR]

Background: The posterior tibialis tendon dysfunction (PTTD) is typically associated with progressive flatfoot deformity, which could be alleviated with foot orthosis. However, the evaluation of tibialis posterior (TP) weakness on lower limb mechanics of flatfoot adults with foot orthoses is scarce and requires further investigation.Research Question: This study aimed to examine the effects of TP weakness on lower limb mechanics in flatfoot adults with foot orthosis through gait analysis and musculoskeletal modelling.Methods: Fifteen young adults with flatfoot were recruited from University to perform a gait experiment with and without foot orthoses. Data collected from the motion capture system were used to drive the musculoskeletal modelling for the estimation of the joint force and extrinsic muscle forces of the lower limb. A parametric analysis was conducted by adjusting the TP muscle strength from 40 % to 100 %. Two-way repeated measures ANOVA was used to compare the peak extrinsic foot muscle forces and joint forces among different levels of TP weakness and insole conditions.Results: TP weakness significantly increased ankle joint force superoinferiorly (F = 125.9, p < 0.001) and decreased anteroposteriorly (F = 125.9, p < 0.001), in addition to a significant increase in the muscle forces of flexor hallucis longus (p < 0.001) and flexor digitorum longus (p < 0.001). Besides, the foot orthosis significantly reduced most peak muscle forces whilst significantly reduced the second peak knee force and peak ankle force compared to the control condition (F = 8.79-30.9, p < 0.05).Significance: The increased extrinsic foot muscle forces (flexor hallucis longus and flexor digitorum longus) and ankle joint forces in the TP weakness condition indicated that TP weakness may induce compensatory muscle activation and attenuated joint load. The abnormal muscle and joint mechanics in flatfoot adults with TP weakness might be restored by the orthosis. [ABSTRACT FROM AUTHOR]

The aim of this work was to determine the feasibility of combined ultrasonography and elastography measurement to characterize the mechanical properties of the intercostal space during breathing. Eighteen asymptomatic participants (ages 13 ± 2 y) and six participants with adolescent idiopathic scoliosis (AIS) were included (Cobb angle 60° ± 12°). Ultrasonographic and elastographic clips were acquired of T8-T9 ribs and the intercostal space. The two adjacent ribs were tracked to infer the breathing cycle. Shear-wave speed (SWS) was measured in the intercostal space at different stages of the breathing cycle. SWS was symmetric in the control group, during both expiration and inspiration. In AIS, the SWS during inspiration was higher in the convex side than in the concave one (p = 0.02). Furthermore, SWS was higher during inspiration than expiration in the control group and in the AIS convex side, but not in the AIS concave side (p > 0.05). This new method combining echography and shear-wave elastography allowed measurement of the mechanical characteristics of the intercostal space at different phases of the breathing cycle and highlighted differences between the AIS and control groups. This approach opens the way to further analyses of the biomechanical characteristics of breathing in severe AIS. [ABSTRACT FROM AUTHOR]

Background Context: Radiographic evaluation in adult spinal deformity (ASD) offers no information on spinopelvic alignment and compensation during dynamic conditions. Motion analysis offers the potential to bridge the gap between static radiographic and dynamic alignment measurement, increasing our understanding on how ASD impacts function.Purpose: This study aimed to explore the changes in sagittal alignment and compensation strategies in ASD between upright standing and walking, compared to control subjects and within different sagittal alignment groups. Ten patients were measured pre- and six months postoperatively to explore the impact of surgical alignment correction on gait.Study Design: Prospective study.Sample Size: Full protocol: 58 ASD and 20 controls; Spinal kinematic analysis: 43 ASD and 18 controls; Postoperative analysis: 10 ASD.Outcome Measures: Standing and walking sagittal spinopelvic (thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvis), and lower limb kinematics, spinopelvic changes between standing and walking (∆ ie, difference between mean dynamic and static angle), lower limb kinetics, spatiotemporal parameters, balance (BESTest), patient-reported outcome scores (SRS-22r, ODI, and FES-I) and radiographic parameters.Methods: Motion analysis was used to assess the standing and walking spinopelvic and lower limb kinematics, as well as the lower limb kinetics during walking. All parameters were compared between controls and patients with ASD, divided in three groups based on their sagittal alignment (ASD 1: decompensated sagittal malalignment; ASD 2: compensated sagittal malalignment; ASD 3: scoliosis and normal sagittal alignment). Ten patients were reassessed 6 months after spinal corrective surgery. Continuous kinematic and kinetic data were analyzed through statistical parametric mapping.Results: All patient groups walked with increased forward trunk tilt (∆SVA=41.43 mm, p<.001) in combination with anterior pelvic tilt (∆Pelvis=2.58°, p<.001) compared to standing, as was also observed in controls (∆SVA=37.86 mm, p<.001; ∆Pelvis=1.62°, p=.012). Patients walked with increased SVA, in combination with decreased LL and alterations in lower limb kinematics during terminal stance and initial swing, as well as altered spatiotemporal parameters. Subgroup analysis could link these alterations in gait to sagittal spinopelvic malalignment (ASD 1 and 2). After surgical correction, lower limb kinematics and spatiotemporal parameters during gait were not significantly improved.Conclusions: To compensate for increased trunk tilt and pelvic anteversion during walking, patients with sagittal malalignment show altered lower limb gait patterns, which have previously been associated with increased risk of falling and secondary lower limb pathology. Since surgical correction of the deformity did not lead to gait improvements, further research on the underlying mechanisms is necessary to improve our understanding of how ASD impacts function. [ABSTRACT FROM AUTHOR]

Background: In people with calf muscle weakness, the stiffness of dorsal leaf spring ankle-foot orthoses (DLS-AFO) needs to be individualized to maximize its effect on walking. Orthotic suppliers may recommend a certain stiffness based on body weight and activity level. However, it is unknown whether these recommendations are sufficient to yield the optimal stiffness for the individual. Therefore, we assessed whether the stiffness following the supplier's recommendation of the Carbon Ankle7 (CA7) dorsal leaf matched the experimentally optimized AFO stiffness.Methods: Thirty-four persons with calf muscle weakness were included and provided a new DLS-AFO of which the stiffness could be varied by changing the CA7® (Ottobock, Duderstadt, Germany) dorsal leaf. For five different stiffness levels, including the supplier recommended stiffness, gait biomechanics, walking energy cost and speed were assessed. Based on these measures, the individual experimentally optimal AFO stiffness was selected.Results: In only 8 of 34 (23%) participants, the supplier recommended stiffness matched the experimentally optimized AFO stiffness, the latter being on average 1.2 ± 1.3 Nm/degree more flexible. The DLS-AFO with an experimentally optimized stiffness resulted in a significantly lower walking energy cost (- 0.21 ± 0.26 J/kg/m, p < 0.001) and a higher speed (+ 0.02 m/s, p = 0.003). Additionally, a larger ankle range of motion (+ 1.3 ± 0.3 degrees, p < 0.001) and higher ankle power (+ 0.16 ± 0.04 W/kg, p < 0.001) were found with the experimentally optimized stiffness compared to the supplier recommended stiffness.Conclusions: In people with calf muscle weakness, current supplier's recommendations for the CA7 stiffness level result in the provision of DLS-AFOs that are too stiff and only achieve 80% of the reduction in energy cost achieved with an individual optimized stiffness. It is recommended to experimentally optimize the CA7 stiffness in people with calf muscle weakness in order to maximize treatment outcomes. Trial registration Nederlands Trial Register 5170. Registration date: May 7th 2015. http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=5170 . [ABSTRACT FROM AUTHOR]

Background: Emphasizing the active use of the arms and coordinating them with the stepping motion of the legs may promote walking recovery in patients with impaired lower limb function. Yet, most approaches use seated devices to allow coupled arm and leg movements. To provide an option during treadmill walking, we designed a rope-pulley system that physically links the arms and legs. This arm-leg pulley system was grounded to the floor and made of commercially available slotted square tubing, solid strut channels, and low-friction pulleys that allowed us to use a rope to connect the subject's wrist to the ipsilateral foot. This set-up was based on our idea that during walking the arm could generate an assistive force during arm swing retraction and, therefore, aid in leg swing.Methods: To test this idea, we compared the mechanical, muscular, and metabolic effects between normal walking and walking with the arm-leg pulley system. We measured rope and ground reaction forces, electromyographic signals of key arm and leg muscles, and rates of metabolic energy consumption while healthy, young subjects walked at 1.25 m/s on a dual-belt instrumented treadmill (n = 8).Results: With our arm-leg pulley system, we found that an assistive force could be generated, reaching peak values of 7% body weight on average. Contrary to our expectation, the force mainly coincided with the propulsive phase of walking and not leg swing. Our findings suggest that subjects actively used their arms to harness the energy from the moving treadmill belt, which helped to propel the whole body via the arm-leg rope linkage. This effectively decreased the muscular and mechanical demands placed on the legs, reducing the propulsive impulse by 43% (p < 0.001), which led to a 17% net reduction in the metabolic power required for walking (p = 0.001).Conclusions: These findings provide the biomechanical and energetic basis for how we might reimagine the use of the arms in gait rehabilitation, opening the opportunity to explore if such a method could help patients regain their walking ability.Trial Registration: Study registered on 09/29/2018 in ClinicalTrials.gov (ID-NCT03689647). [ABSTRACT FROM AUTHOR]

Background: Most previous studies reported biomechanical deficits in individuals with a trans-tibial amputation (TTA) during gait using zero-dimensional analyses. However, these analyses do not allow to precisely determine during which part of the gait cycle these deficits occur. There is a need to use more appropriate methods to map the differences, such as one-dimensional statistical parametric mapping.Research Question: What are the most relevant phases of the gait cycle during which the biomechanical deficits in TTA occur?Methods: Eight TTA and 15 healthy counterparts (CON) underwent one biomechanical gait analysis. Pelvis, hip, knee and ankle kinematics, total support moment (TSM) and gastrocnemius lateralis, vastus lateralis and tibialis anterior muscle activity were compared between the amputated (AmLL), the intact (InLL) and the control (CnLL) lower limbs using one-dimensional statistical parametric mapping.Results: More ankle dorsiflexion and knee flexion were observed for the AmLL compared to the InLL and CnLL (ankle only) from the end of the stance phase to the beginning of the swing phase. Less knee flexion was also found for the AmLL during early stance phase. More pelvis posterior tilt and rotation toward the contralateral limb was observed during most of the gait cycle for the AmLL compared to the InLL. TSM was smaller for the AmLL compared to the CnLL during early stance phase.Significance: Using a one-dimensional statistical parametric mapping approach for TTA gait analysis, this study provides novel insights on their biomechanical gait deficits compared to CON. Greater reliance on the InLL was observed in TTA as suggested by the asymmetric kinematic and kinetic profiles. [ABSTRACT FROM AUTHOR]

Introduction: Although previous studies have contributed to our understanding of the effects of implementing the virtual reality as a rehabilitation tool in patients with Parkinson's disease (PD), additional research is needed to examine the effects of applying balance-based exergaming training on quantitative biomechanical measures of balance.Research Question: To investigate the effects of balance-based conventional and exergaming training on posture parameters.Methods: The study involved 24 patients with PD (Hoehn and Yahr stages II-III).Participants underwent twelve training sessions during the 4-week training period. The experimental group (n=12) was trained with a custom-made exergaming balance based training system, the control group (n=12) underwent a conventional balance training. All objective outcomes were measured before intervention and the day after completion of training program. Postural stability was assessed using the quiet standing test, dynamic balance was assessed using limits of stability (LOS) and functional balance (FBT) tests.Results: After training, participants in both groups showed significantly better results in static balance performance. However, only exergaming training significantly improved LOS performance (higher values of Range of forward lean (p = 0.039, dz = 0.67) and leaning rate (p=0.007, dz=0.96). Also FBT test improved significantly only in experimental group (decrease in time to target hit (p=0.02, dz=0.76) and significant increase of average COP velocity (p=0.008, dz=0.93).Conclusion: This study found that exergaming training created for patients with PD enhanced static and dynamic balance whereas conventional balance training improved static balance. Posturography is sensitive enough to reveal differential effects of training for both groups. These findings support the inclusion of our exergaming training in the exercise program for participants with PD. [ABSTRACT FROM AUTHOR]

Background: Individuals with chronic ankle instability (CAI) have an increased risk for recurrent injuries. The preventive effects of external ankle supports are not fully understood. This study aimed to examine the effect of elastic ankle support on running ankle kinematics.Methods: 3D running gait analysis of individuals with and without CAI was conducted at three-minute-running trials at 2.78 m/s with and without elastic ankle support in a randomised order. Ankle kinematics and intra-individual standard deviations (variability) were calculated at each percent of the running gait cycle. Group and ankle support effects were calculated using statistical parameter mapping.Results: Twenty-seven individuals were analysed (CAI: n = 14, controls: n = 13). When wearing ankle support, CAI individuals showed significantly decreased plantarflexion angles at 43-47 % (p = 0.033) and 49-51 % (p = 0.043) of the running gait cycle compared to normal running. In healthy controls, no differences in ankle angles between both conditions were found. Comparisons between CAI individuals and healthy controls showed statistically significant differences in the plantar-/dorsiflexion angles at 38-41 % (p = 0.044) with ankle support and at 34-46 % (p = 0.004) without ankle support. Significant ankle angle variability differences were found for ankle in-/eversion between CAI individuals and healthy controls (p = 0.041) at 32-33 % of the running gait cycle.Conclusions: Elastic ankle support reduces the range of sagittal plane running ankle kinematics of CAI individuals but not of healthy controls. Further research is needed to evaluate the association between ankle support effects and the risk for recurrent ankle sprains. [ABSTRACT FROM AUTHOR]

Background: There is a common perception that poorly fitting footwear will negatively impact a child's foot, however, there is limited evidence to support this.Aim: To determine the effect of shoe size on foot motion, perceived footwear comfort and fit during walking, maximal vertical jump height and maximal standing broad jump distance in children aged 8-12 years.Methods: Fourteen participants completed 3D walking gait analysis and jumping tasks in three different sizes of school shoes (one size bigger, fitted for size, one size smaller). In-shoe motion of the hindfoot, midfoot and 1st metatarsophalangeal joint (1st MTPJ) were calculated using a multi-segment kinematic foot model. Physical performance measures were calculated via maximal vertical jump and maximal standing broad jump. Perceived footwear comfort and fit (heel, toes and overall) was assessed using a 100 mm visual analog scale (VAS). Differences were compared between shoe sizes using repeated measures ANOVA, post-hoc tests and effect sizes (Cohen's d).Results: Compared to the fitted footwear, the smaller sizing restricted hindfoot eversion (-2.5°, p = 0.021, d = 0.82), 1st MTPJ dorsiflexion (-3.9°, p = 0.012, d = 0.54), and compared to the bigger footwear, smaller sizing restricted sagittal plane midfoot range-of-motion during walking (-2.5°, p = 0.047, d = 0.59). The fitted footwear was rated as more comfortable overall with the smaller size rated as too tight in both the heel (mean difference 11.5 mm, p = 0.042, d = 0.58) and toes (mean difference 12.1 mm, p = 0.022, d = 0.59), compared to the fitted size. Vertical and standing broad jump distance were not impacted by footwear size (p = 0.218-0.836).Significance: Footwear that is too small restricts foot motion during walking in children aged 8-12 years. Jump performance was not affected. Children were able to recognise shoes that were not correctly matched to their foot length, reinforcing that comfort is an important part of the fitting process. [ABSTRACT FROM AUTHOR]

Background: The biomechanical mechanisms underlying stair climbing limitations are poorly understood in people with multiple sclerosis (MS).Research Questions: Are trunk and pelvis motion and lower extremity joint moments during step ascent different between MS and control groups? Are step ascent biomechanics and stair climbing performance associated in people with MS?Methods: 20 people with MS (49 ± 12 years, EDSS range: 1.5-5.5) and ten control participants (48 ± 12 years) underwent three-dimensional motion analysis while ascending a 15.2-cm step and also completed a timed Functional Stair Test. Main effects of group (MS vs Control) and limb (Stronger/Dominant vs Weaker/Non-dominant) and interactions were assessed using two-way analyses of variance. Associations between movement patterns during the step ascent and Functional Stair Test performance were performed using Pearson's correlations and backward stepwise linear regression.Results: Significant group main effects were observed in greater sagittal pelvis excursion (p < 0.001), greater sagittal (p = 0.013) and frontal (p = 0.001) trunk excursion, and lower trail limb peak ankle plantar flexion moment (p < 0.001) of the MS group. Significant limb main effects were observed with greater sagittal trunk excursion (p = 0.037) and peak trail limb ankle plantar flexion moment (p = 0.037) in the stronger/dominant limb. A significant interaction was observed in peak knee extensor moment (p = .002). Stair climbing performance in the MS group correlated with sagittal (r = .607, p=<0.001) and frontal pelvis excursions (r = 0.385, p = 0.014), sagittal trunk excursion (r = .411, p = 0.008), and ankle plantar flexion moments (r=-0.415, p = 0.008). Sagittal and frontal pelvis excursion and bilateral handrail use explained a significant amount of variability in stair climbing performance (Adj R2 = 0.775).Significance: In conclusion, despite the presence of proximal and distal lower extremity movement pattern compensations during a step ascent task, larger pelvis angular excursions are associated with impaired stair climbing performance in people with MS and may serve as targets for future rehabilitation interventions. [ABSTRACT FROM AUTHOR]

Background: The clinical utility of motion capture modeling relies on the accurate tracking of segment motions. Soft tissue artefact presents a particular challenge for modeling hip rotation, knee rotation, and knee varus-valgus motions. The integration of a patella marker has been shown to significantly improve hip rotation tracking for models that utilize anatomical definitions of joint axes (e.g. anatomical models). However, these modeling improvements have not been extended to models that use functional segment motion to define joint axes (e.g. functional models).Research Question: How does the positioning of a patella marker influence functional model performance?Methods: A patella functional model (PFM) was created by integrating a patella marker into the functional model (FM) used at our center. Nine distinct versions of the PFM were created using a 3 × 3 grid of markers placed across the patella. Ten typically developing participants performed controlled hip rotation, controlled knee flexion-extension, and free speed walking trials to assess FM and PFM performance differences.Results: The top performing PFM modeled 98 ± 8 % of the reference hip rotation range of motion compared to 71 ± 9 % for the FM. This PFM had low sensitivity to knee flexion-extension motion, 5 ± 10 %. For walking kinematics, this top performing PFM reported 14 % greater hip rotation ROM during stance, 46 % less knee rotation ROM over the entire gait cycle, and 32 % less knee varus-valgus during swing compared to the FM. The differences in modeling are nearly identical to those reported between skin mounted marker and fluoroscopy-based models, indicating that utilization of the patella marker leads to improvements in tracking accuracy.Significance: Utilization of a precisely placed patella marker led to substantial improvements in modeled hip rotation, knee rotation, and knee varus-valgus. These improvements have the potential to positively impact those specialties that rely on motion capture modeling for clinical decision-making, such as orthopedic surgery. [ABSTRACT FROM AUTHOR]

Background: Bilateral plantarflexor muscle weakness is a common impairment in many neuromuscular diseases. However, the way in which severity of plantarflexor weakness affects gait in terms of walking energy cost and speed is not fully understood. Predictive simulations are an attractive alternative to human experiments as simulations allow systematic alterations in muscle weakness. However, simulations of pathological gait have not yet been validated against experimental data, limiting their applicability.Research Question: Our first aim was to validate a predictive simulation framework for walking with bilateral plantarflexor weakness by comparing predicted gait against experimental gait data of patients with bilateral plantarflexor weakness. Secondly, we aimed to evaluate how incremental levels of bilateral plantarflexor weakness affect gait.Methods: We used a planar musculoskeletal model with 9 degrees of freedom and 9 Hill-type muscle-tendon units per leg. A state-dependent reflex-based controller optimized for a function combining energy cost, muscle activation squared and head acceleration was used to simulate gait. For validation, strength of the plantarflexors was reduced by 80 % and simulated gait compared with experimental data of 16 subjects with bilateral plantarflexor weakness. Subsequently, strength of the plantarflexors was reduced stepwise to evaluate its effect on gait kinematics and kinetics, walking energy cost and speed.Results: Simulations with 80 % weakness matched well with experimental hip and ankle kinematics and kinetics (R > 0.64), but less for knee kinetics (R < 0.55). With incremental strength reduction, especially beyond a reduction of 60 %, the maximal ankle moment and power decreased. Walking energy cost and speed showed a strong quadratic relation (R2>0.82) with plantarflexor strength.Significance: Our simulation framework predicted most gait changes due to bilateral plantarflexor weakness, and indicates that pathological gait features emerge especially when bilateral plantarflexor weakness exceeds 60 %. Our framework may support future research into the effect of pathologies or assistive devices on gait. [ABSTRACT FROM AUTHOR]

Background: To navigate through dynamically changing environments and to avoid collisions with stationary and moving obstacles, older adults tend to over rely on their visual system because it is a more reliable source of information. Aging affects both visuomotor integration and visual perception, often resulting in the inability to produce appropriate adaptive locomotor actions in a timely manner.Research Question: Does peripheral visual information in the environment affected older adults' ability to complete a gap-crossing task with a set of closing doors at different rates (0.6-1.2 m/s)?Methods: Fifteen older adults (65-74 years) completed the study inside a virtual environment with three different levels of peripheral visual information: 1) empty; 2) stationary avatars; and 3) moving avatars. Kinematic data was collected using an Optotrak camera system to track the older adults' body movements during the task.Results: The results demonstrated that regardless of the environment or closing door speed, older adults maintained consistent approach speeds. However, older adults collided with the fastest moving doors a significant number of times at the fastest door closing rates for the empty and moving avatar conditions.Significance: Although it appears that older adults are able to attend on a central task (i.e., passing through closing doors) and maintain constant behaviours regardless of the visual information from peripheral environment, richness of the peripheral environment provides accurate feedback about self-motion affects success rates. [ABSTRACT FROM AUTHOR]

Background: This study compared stiffness between two constructs for talonavicular arthrodesis: a dorsomedial plating system and two partially threaded cannulated cancellous screws. We hypothesized that the plate would exhibit greater stiffness and resistance to deformation during cyclic loading.Methods: The constructs were implanted in eight matched pairs of cadaveric feet and subjected to axial torsion, cantilever bending in two directions, and cyclic loading to failure.Results: The two-screw constructs were significantly stiffer in plantar-dorsal bending (p = .025) and trended towards a higher number of cycles before failure than the plate group (p = .087). No significant differences were observed in internal torsion (p = .620), external torsion (p = .165), or medial-lateral bending (p = .686).Conclusions: This study provided the first biomechanical assessment of a plating system with an integrated compression screw, which was significantly less stiff than a two-screw construct when loaded from plantar to dorsal. [ABSTRACT FROM AUTHOR]