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Background: Children with cerebral palsy (CP) often exhibit altered selective motor control during gait (SMCg). Ankle-foot-orthoses (AFOs) are used in this population to improve gait, by reducing the degrees of freedom at the ankle joint. However, the specific impact of AFOs on SMCg and whether this effect is more related to gait deviations or motor development remains unclear., Research Question: Do AFOs impact SMCg, and is the change related to joint kinematics or age?, Methods: Gait analysis data from 53 children and adolescents with spastic CP, walking both barefoot and with AFOs, were included. Electromyography data from six lower-limb muscles, and lower limb joint kinematics were analyzed for both walking conditions. SMCg was quantified by the total variance in electromyography activity accounted for by one synergy (tVAF 1 ), where an increase in tVAF 1 indicates a decrease in SMCg. Kinematic gait deviation was assessed using the Gait-Profile-Score (GPS) and sagittal plane ankle Gait-Variable-Score (ankle-GVS). All analyses were performed for the more clinically involved leg only., Results: Walking with AFOs resulted in a mean increase in tVAF 1 of 0.02±0.07 (p=0.015) and a median increase in ankle-GVS of 3.4º (p>0.001). No significant changes were observed in GPS, and no correlation was found between the changes in tVAF 1 and ankle-GVS. A significant positive moderate correlation was found between the change in tVAF 1 and age, even with ankle-GVS as a covariate (r=0.45; p>0.001)., Significance: Walking with an AFO resulted in a small decrease in SMCg, with large inter-participant variability. Younger participants showed a greater decrease in SMCg, which may indicate greater neuromuscular plasticity in early developmental stages., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Introduction: Individuals with cerebral palsy (CP) often present with altered motor control. This can be assessed selectively during sitting/lying with the Selective Control Assessment of the Lower Extremity (SCALE), or dynamically with the dynamic motor control index during walking (walk-DMC). Both approaches suggest that altered selective motor control relate to larger gait deviations., Research Question: Does the walk-DMC provide valuable information in addition to the SCALE for estimating gait deviations in individuals with CP., Methods: Retrospective, treadmill-based gait analysis data of 157 children with spastic CP (mean 11.4±3.5 years) and Gross Motor Function Classification System levels I (n=45), II (n=88) or III (n=24) were extracted. Gait kinematic deviations were evaluated using the Gait Profile Score (GPS). The SCALE, walk-DMC and GPS were extracted for the more clinically involved leg (unilateral-analysis), and for both legs together (bilateral-analysis)., Results: GPS moderately correlated with both SCALE and walk-DMC scores, unilaterally and bilaterally (r≥0.4; p<0.001). Multivariate linear regression analyses were conducted, taking into account potential confounding factors. In the unilateral analysis, 54% of the GPS variance was explained (p<0.001), with both walk-DMC and SCALE significantly contributing to the GPS variance (p=0.006 and p=0.008, respectively). In the bilateral analysis, 61% of the GPS variance was explained (p<0.001), with both walk-DMC and SCALE significantly contributing to the GPS variance (p=0.006 and p<0.001, respectively). Dimensionless walking speed and use of assistive devices were the only confounding factors included in each analysis., Significance: Both SCALE and walk-DMC significantly contribute to GPS variance, suggesting that they likely measure different components of motor control, and both may be useful in understanding the underlying relationship between motor control and deviations in gait kinematics., Competing Interests: Declaration of Competing Interest The authors whose names are listed immediately below certify that they have NO affiliations with or involvement in any organization or entity with any financial interest (such as honoraria; educational grants; participation in speakers’ bureaus; membership, employment, consultancies, stock ownership, or other equity interest; and expert testimony or patent-licensing arrangements), or non-financial interest (such as personal or professional relationships, affiliations, knowledge or beliefs) in the subject matter or materials discussed in this manuscript., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Individuals with cerebral-palsy commonly present with altered kinematics and selective-motor-control during gait, and may also experience musculoskeletal pain. This pilot study aims to investigate if the immediate experience of musculoskeletal pain during gait influences kinematics and selective-motor-control in individuals with spastic cerebral-palsy., Methods: Retrospective treadmill-based gait-analysis data for 145 individuals with spastic cerebral-palsy were screened. Participants were asked about experiencing lower-extremity musculoskeletal pain immediately during gait, with 26 individuals (18%) reporting this was the case (pain-group; mean 11.55 ± 3.15 years, Gross-Motor-Function-Classification-System levels I/II/III n = 5/13/8, Uni/bilateral involvement n = 11/15). Of the 77 individuals who did not report any pain, a no-pain group (n = 26) was individually matched. Kinematics were evaluated using the Gait-Profile-Score and spatiotemporal parameters (dimensionless-walking-speed, single-leg-support percentage and step-time). Selective-motor-control was assessed using the Walking-Dynamic-Motor-Control index., Findings: In the pain-group, 58% reported experiencing pain in their more-involved leg, 8% in the less-involved leg and 34% in both legs. Regarding the pain location, 38% of the pain-group reported experiencing pain in multiple locations. On a more specific level, 35%, 46% and 54% reported pain around the hip/thigh, knee/calf and ankle/ft, respectively. No significant differences were observed between the pain and no-pain groups for any of the outcome measures, in each leg or bilaterally., Interpretation: No significant differences in kinematics and selective-motor-control during gait were found between individuals with spastic cerebral-palsy, with and without musculoskeletal pain. This suggests that the individuals in this study may not present with obvious antalgic gait patterns, which may relate to the pre-existing altered kinematics and selective-motor-control., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Objective: To investigate longitudinal changes in selective motor control during gait (SMCg) in individuals with cerebral palsy (CP), and to assess if they are related to changes in gait deviations., Method: Twenty-three children/adolescents with spastic CP (mean ± SD age = 9.0±2.5 years) and two 3D gait assessments (separated by 590±202 days) with no interim surgical intervention, were included. SMCg was assessed using muscle synergy analysis to determine the dynamic motor control index (walk-DMC). Gait deviation was assessed using the Gait profile score (GPS) and Gait variable scores (GVS)., Results: There were no mean changes in walk-DMC score, GPS or GVS between assessments. However, changes in walk-DMC scores in the more involved leg related to changes in hip flexion-extension and hip internal-external GVS (rp = -0.56; p = 0.017 and rp = 0.65; p = 0.004, respectively)., Conclusions: On average, there were no significant longitudinal changes in SMCg. However, there was considerable variability between individuals, which may relate to changes in hip joint kinematics. This suggests that a combination of neural capacity and biomechanical factors influence lower limb muscle co-activation in individuals with CP, with a potential important role for the hip muscles. These findings highlight the importance of taking an individualized approach when evaluating SMCg in individuals with CP., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2023 Sorek et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Objective: To evaluate the influence of the number of muscles and strides on estimating motor control accuracy during treadmill-gait, in individuals with cerebral palsy (CP)., Methods: Bilateral lower limb electromyography data were extracted for 44 children/adolescents with CP. The number of synergy solutions required to explain 90 % of the variance (tVAF-threshold) and the total variance accounted for by one synergy (tVAF 1 ) were calculated for a different number of strides (between 5 and 50) and muscles both unilaterally (four to seven) and bilaterally (eight to 14). The kappa and intraclass correlation coefficients were used to assess similarities in tVAF-threshold and tVAF 1 between the different number of strides and muscle sets., Results: In both analyses, the number of muscles influenced the tVAF-threshold. Additionally, using <30 strides led to only substantial-moderate agreement with 50 strides (k < 0.80). In both analyses, the mean tVAF 1 values demonstrated high-agreement between the different number of muscles (intraclass-correlations = 0.88-0.93) and strides (intraclass-correlations = 0.96-0.99); In the group level, it may result in an error of ≤2.3 %. However, in the individual level, using different number of muscles or <40 strides may result in an error of ≥6 %., Conclusion: Differing numbers of muscles and strides did not influence the group mean tVAF 1 value, but it influenced the tVAF-threshold value. In addition, using different number of muscles or strides can lead to a large measurement error in the individual tVAF 1 value., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Background: Ultrasound imaging combined with 3D motion analysis allows for in-vivo assessment of muscle-tendon unit lengths during gait. The clinical relevance of analysing the medial gastrocnemius (MG) and Achilles muscle-tendon junction (MTJ), MG mid-muscle belly fascicles (FAS) and muscle thickness was shown. However, their reliability error estimations over the gait cycle is unknown., Research Question: What are the intra- and inter-session errors associated with extracting MG belly, thickness, FAS and tendon lengths using ultrasound during gait in healthy participants?, Methods: 3D gait analysis was carried out in ten healthy adults as they walked on an instrumented treadmill at a comfortable walking speed. An ultrasound probe was secured on the leg and tracked by 3D motion analysis. Images were collected during two walking trials with the probe on the MG muscle-belly to estimate FAS lengths and muscle thickness, and during two trials with the probe on the MTJ to estimate muscle-belly and tendon lengths. A second session was performed after 5 ± 4 days where a different operator placed the ultrasound probe. The standard deviation (SD) of absolute and relative lengths changes during the gait cycle over different trials were calculated per participant. SD values averaged over participants represented intra- and inter-session errors., Results: For all assessed variables, the intra-session errors were <2.2 mm, except for the FAS lengths (3.1 mm). The inter-session errors were larger than the intra-session, with the highest values found for the absolute muscle-tendon unit lengths (5.6 mm). Relative length errors were smaller than absolute length errors., Significance: Intra-session errors, which may reflect natural variability and data processing errors, seem more critical when extracting absolute FAS than muscle-tendon lengths. Standardized probe positioning on the MTJ between sessions may improve the inter-session reliability. Expressing the lengths relative to their lengths as the beginning of the gait cycle reduces the inter-session errors., (Copyright © 2021 Elsevier B.V. All rights reserved.)

This investigation assessed the processer reliability of estimating muscle volume and echo-intensity of the rectus femoris, tibialis anterior and semitendinosus. The muscles of 10 typically developing children (8.15 [1.40] y) and 15 children with spastic cerebral palsy (7.67 [3.80] y; Gross Motor Function Classification System I = 5, II = 5, III = 5) were scanned with 3-D freehand ultrasonography. For the intra-processer analysis, the intra-class correlations coefficients (ICCs) for muscle volume ranged from 0.943-0.997, with relative standard errors of measurement (SEM%) ranging from 1.24%-8.97%. For the inter-processer analysis, these values were 0.853 to 0.988 and 3.47% to 14.02%, respectively. Echo-intensity had ICCs >0.947 and relative SEMs <4% for both analyses. Muscle volume and echo-intensity can be reliably extracted for the rectus femoris, semitendinosus and tibialis anterior in typically developing children and children with cerebral palsy. The need for a single processer to analyze all data is dependent on the size of the expected changes or differences., Competing Interests: Declaration of Competing Interest The authors declare that they have no affiliations with or involvement in any organization with any financial or non-financial interest in the subject matter and materials discussed in this article., (Copyright © 2021 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.)

Botulinum NeuroToxin-A (BoNT-A) injections to the medial gastrocnemius (MG) and lower-leg casts are commonly combined to treat ankle equinus in children with spastic cerebral palsy (CP). However, the decomposed treatment effects on muscle or tendon structure, stretch reflexes, and joint are unknown. In this study, BoNT-A injections to the MG and casting of the lower legs were applied separately to gain insight into the working mechanisms of the isolated treatments on joint, muscle, and tendon levels. Thirty-one children with spastic CP (GMFCS I-III, age 7.4 ± 2.6 years) received either two weeks of lower-leg casts or MG BoNT-A injections. During full range of motion slow and fast passive ankle rotations, joint resistance and MG stretch reflexes were measured. MG muscle and tendon lengths were assessed at resting and at maximum dorsiflexion ankle angles using 3D-freehand ultrasound. Treatment effects were compared using non-parametric statistics. Associations between the effects on joint and muscle or tendon levels were performed using Spearman correlation coefficients ( p < 0.05). Increased joint resistance, measured during slow ankle rotations, was not significantly reduced after either treatment. Additional joint resistance assessed during fast rotations only reduced in the BoNT-A group (-37.6%, p = 0.013, effect size = 0.47), accompanied by a reduction in MG stretch reflexes (-70.7%, p = 0.003, effect size = 0.56). BoNT-A increased the muscle length measured at the resting ankle angle (6.9%, p = 0.013, effect size = 0.53). Joint angles shifted toward greater dorsiflexion after casting (32.4%, p = 0.004, effect size = 0.56), accompanied by increases in tendon length (5.7%, p = 0.039, effect size = 0.57; r = 0.40). No associations between the changes in muscle or tendon lengths and the changes in the stretch reflexes were found. We conclude that intramuscular BoNT-A injections reduced stretch reflexes in the MG accompanied by an increase in resting muscle belly length, whereas casting resulted in increased dorsiflexion without any changes to the muscle length. This supports the need for further investigation on the effect of the combined treatments and the development of treatments that more effectively lengthen the muscle., (Copyright © 2020 Peeters, Van Campenhout, Hanssen, Cenni, Schless, Van den Broeck, Desloovere and Bar-On.)

New Findings: What is the central question of this study? Is the proposed semi-automatic algorithm suitable for tracking the medial gastrocnemius muscle-tendon junction in ultrasound images collected during passive and active conditions? What is the main finding and its importance? The validation of a method allowing efficient tracking of the muscle-tendon junction in both passive and active conditions, in healthy as well as in pathological conditions. This method was tested in common acquisition conditions and the developed software made freely available., Abstract: Clinically relevant information can be extracted from ultrasound (US) images by tracking the displacement of the junction between muscle and tendon. This paper validated automatic methods for tracking the location of muscle-tendon junction (MTJ) between the medial gastrocnemius and the Achilles tendon during passive slow and fast stretches, and active ankle rotations while walking on a treadmill. First, an automatic algorithm based on an optical flow approach was applied on collected US images. Second, results of the automatic algorithm were evaluated and corrected using a quality measure that indicated which critical images need to be manually corrected. US images from 12 typically developed (TD) children, 12 children with spastic cerebral palsy (SCP) and eight healthy adults were analysed. Automatic and semi-automatic tracking methods were compared to manual tracking using root mean square errors (RMSE). For the automatic tracking, RMSE was less than 3.1 mm for the slow stretch and 5.2 mm for the fast stretch, the worst case being for SCP. The tracking results in the fast stretch condition were improved (especially in SCP) by using the semi-automatic approach, with an RMSE reduction of about 30%. During walking, the semi-automatic method also reduced errors, with a final RMSE of 3.6 mm. In all cases, data processing was considerably shorter using the semi-automatic method (2 min) compared to manual tracking (20 min). A quick manual correction considerably improves tracking of the MTJ during gait and allows to achieve results suitable for further analyses. The proposed algorithm is freely available., (© 2019 The Authors. Experimental Physiology © 2019 The Physiological Society.)

Aim: This cross-sectional investigation evaluated whether recurrent botulinum neurotoxin A (BoNT-A) interventions to the medial gastrocnemius have an influence on muscle morphology, beyond Gross Motor Function Classification System (GMFCS) level., Method: A cohort of typically developing children (n=67; 43 males, 24 females; median age 9y 11mo [range 7y 10mo-11y 6mo]), a cohort of children with spastic cerebral palsy (CP) naive to BoNT-A interventions (No-BoNT-A; n=19; 10 males, nine females; median age 9y 3mo [range 8y 5mo-10y 10mo]) and a cohort of children with spastic CP with a minimum of three recurrent BoNT-A interventions to the medial gastrocnemius (BoNT-A; n=19; 13 males, six females; median age 9y 8mo [range 7y 3mo-10y 7mo]) were recruited. Three-dimensional freehand ultrasound was used to estimate medial gastrocnemius volume normalized to body mass and echo-intensity., Results: Normalized medial gastrocnemius volume and echo-intensity significantly differed between the two spastic CP cohorts (p≤0.05), with the BoNT-A cohort having larger alterations. Associations between normalized medial gastrocnemius volume and echo-intensity were highest in the No-BoNT-A cohort, followed by the BoNT-A cohort. Multiple regression analyses revealed that both GMFCS level and BoNT-A intervention history were significantly associated with smaller normalized medial gastrocnemius volume and higher echo-intensity., Interpretation: Recurrent BoNT-A interventions may induce alterations to medial gastrocnemius volume and echo-intensity beyond the natural history of the spastic CP pathology., What This Paper Adds: In spastic cerebral palsy, medial gastrocnemius volumes are smaller and echo-intensities higher compared with typical development. Alterations after botulinum neurotoxin A intervention (BoNT-A) are larger than in no BoNT-A intervention. Gross Motor Function Classification System level and BoNT-A history significantly associate with medial gastrocnemius and echo-intensity alterations., (© 2018 Mac Keith Press.)

The ultrasound (US) probe spatial calibration is a key prerequisite for enabling the use of the 3D freehand US technique. Several methods have been proposed for achieving an accurate and precise calibration, although these methods still require specialised equipment. This equipment is often not available in research or clinical facilities. Therefore, the present investigation aimed to propose an efficient US probe calibration method that is accessible in terms of cost, easy to apply and capable of achieving results suitable for clinical applications. The data acquisition was carried out by performing two perpendicular US sweeps over water filled balloon phantoms. The data analysis was carried out by computing the similarity measures between 2D images from the first sweep and the corresponding images of the 3D reconstruction of the second sweep. These measures were maximized by using the Nelder-Mead algorithm, to find the optimal solution for the calibration parameters. The calibration results were evaluated in terms of accuracy and precision by comparing known phantom geometries with those extracted from the US images. The accuracy and the precision after applying the calibration method were improved. By using the parameters obtained from the plane phantom method as initialization of the calibration parameters, the accuracy and the precision in the best scenario was 0.4 mm and 1.5 mm, respectively. These results were in line with the methods requiring specialised equipment. However, the applied method was unable to consistently produce this level of accuracy and precision. The calibration parameters were also tested in a musculoskeletal application, revealing sufficient matching of the relevant anatomical features when multiple US sweeps are combined in a 3D reconstruction. To improve the current results and increase the reproducibility of this research, the developed software is made available., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Background: Individuals with spastic cerebral palsy (CP) have neuromotor symptoms contributing towards their gait patterns. However, the role of altered muscle morphology alongside these symptoms is yet to be fully investigated., Research Question: To what extent can medial gastrocnemius and tibialis anterior volume and echo-intensity, plantar/dorsiflexion strength and selective motor control, plantarflexion spasticity and passive ankle dorsiflexion explain abnormal ankle gait., Method: In thirty children and adolescents with spastic CP (8.6 ± 3.4 y/mo) and ten typically developing peers (9.9 ± 2.4 y/mo), normalised muscle volume and echo-intensity were estimated. Both cohorts also underwent three-dimensional gait analysis, whilst for participants with spastic CP, plantar/dorsi-flexion strength and selective motor control, plantarflexion spasticity and maximum ankle dorsiflexion were also measured. The combined contribution of these parameters towards five clinically meaningful features of gait were evaluated, using backwards multiple regression analyses., Results: With respect to the typically developing cohort, the participants with spastic CP had deficits in normalised medial gastrocnemius and tibialis anterior volume of 40% and 33%, and increased echo-intensity values of 19% and 16%, respectively. The backwards multiple regression analyses revealed that the combination of reduced ankle dorsiflexion, muscle volume, plantarflexion strength and dorsiflexion selective motor control could account for 12-62% of the variance in the chosen features of gait., Significance: The combination of altered muscle morphology and neuromotor symptoms partly explained abnormal gait at the ankle in children with spastic CP. Both should be considered as important measures for informed treatment decision-making, but further work is required to better unravel the complex pathophysiology., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Ultrasound imaging modalities offer a clinically viable method to visualize musculoskeletal structures. However, proper data comparison between investigations is compromised because of a lack of measurement error documentation and method standardization. This investigation analyzes the reliability and validity of extracting medial gastrocnemius belly and fascicle lengths and pennation angles in different ankle joint positions, across the full range of motion, in a cohort of 11 children with spastic cerebral palsy and 11 typically developed children. Each of these parameters was extracted from two consecutive acquisitions, using both 2-D and 3-D ultrasound images. The findings suggest that the muscle tendon junction extraction in 2-D images can be a suitable parameter for analyzing medial gastrocnemius muscle length in typically developed children and children with spastic cerebral palsy, although averaging over multiple measurements is recommended to reduce variability. More caution should be taken when performing analyses based on fascicle length., (Crown Copyright © 2018. Published by Elsevier Inc. All rights reserved.)

Stretch reflex hyperactivity in the gastrocnemius of children with spastic cerebral palsy (CP) is commonly evaluated by passively rotating the ankle joint into dorsiflexion at different velocities, such as applied in conventional clinical spasticity assessments. However, surface electromyography (sEMG) collected from the medial gastrocnemius (MG) during such examination reveals unexplained heterogeneity in muscle activation between patients. Recent literature also highlights altered muscle tensile behavior in children with spastic CP. We aimed to document MG muscle and tendon lengthening during passive ankle motion at slow and fast velocity and explore its interdependence with the elicited hyperactive stretch reflex. The ankle of 15 children with CP (11 ± 3 years, GMFCS 9I 6II, 8 bilateral, 7 unilateral) and 16 typically developing children (TDC) was passively rotated over its full range of motion at slow and fast velocity. Ultrasound, synchronized with motion-analysis, was used to track the movement of the MG muscle-tendon junction and extract the relative lengthening of muscle and tendon during joint rotation. Simultaneously, MG sEMG was measured. Outcome parameters included the angular and muscle lengthening velocities 30 ms before EMG onset and the gain in root mean square EMG during stretch, as a measure of stretch reflex activity. Compared to slow rotation, the muscle lengthened less and stretch reflex activity was higher during fast rotation. These velocity-induced changes were more marked in CP compared to TDC. In the CP group, muscle-lengthening velocity had higher correlation coefficients with stretch reflex hyperactivity than joint angular velocity. Muscles with greater relative muscle lengthening during slow rotation had earlier and stronger stretch reflexes during fast rotation. These initial results suggest that ankle angular velocity is not representative of MG muscle lengthening velocity and is less related to stretch reflex hyperactivity than MG muscle lengthening. In addition, muscles that lengthened more during slow joint rotation were more likely to show a velocity-dependent stretch reflex. This interdependence of muscle lengthening and stretch reflexes may be important to consider when administering treatment. However, muscle and tendon lengthening properties alone could not fully explain the variability in stretch reflexes, indicating that other factors should also be investigated.

Background: 3D freehand ultrasound enables the creation of volumetric data. The acquisition of morphological features, such as muscle volume, is influenced by the variations in force applied to the skin with the ultrasound probe. To minimise the deformations, a concave-shaped plastic mount combined with a custom-shaped gel pad was developed for the ultrasound head, named Portico. This study analyses to what extent the Portico reduces muscle deformation and corresponding errors in estimating muscle volume., Method: Twenty medial gastrocnemius (MG) muscles were assessed (10 from typically developing children; 10 from children with spastic cerebral palsy). Two repetitions were acquired in each of the following approaches: (1) with the lower leg submerged in a water tank as a non-deformed reference; (2) probe-on-skin (PoS) as the conventional approach and (3) the newly introduced Portico. PoS and Portico data were registered with respect to the ones corresponding in a water tank. An in-house software package (Py3DFreeHandUS) was used to process the data and MG volume was estimated using MeVisLab. The minimal detectable change (MDC) was calculated., Results: With respect to the PoS approach, the Portico reduced muscle deformation by 46%. For both the typically developing and spastic cerebral palsy cohorts, lower MDCs were found when using the Portico., Discussion: Despite the improvements, the Portico did not yield statistically more reliable MG volume estimations than the traditional PoS approach. Further improvement can be attained by optimising the fit between the gel pad and the curvature of the limb, using a larger choice of Portico geometries., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background and Objective: 3D freehand Ultrasonography is a medical imaging technique that can be used to measure muscle and tendon morphological and structural properties, including volume, lengths and echo-intensity. These properties are clinically relevant in neurological disorders such as spastic cerebral palsy to monitor disease progression and evaluate the effect of treatment. This study presents a methodology for extracting these parameters along with a clinical reliability analysis for the data acquisition and processing., Methods: The medial gastrocnemius muscles and Achilles tendon of 10 typically developing children and 10 children with spastic cerebral palsy were assessed. An open-source in-house software library developed in Python (Py3DFreeHandUS) was used to reconstruct, into one 3D data set, the data simultaneously acquired from an US machine and a motion tracking system. US images were manually segmented and linearly interpolated by means of a new simplified approach which involved sequentially decreasing the total number of images used for muscle border segmentation from 100% to 5%. Acquisition and processing reliability was defined based on repeated measures from different data processers and from different data acquirers, respectively., Results: When only 10% of the US images were outlined, there was an average underestimation of muscle volume of 1.1% and 1.6% with respect the computation of all the available images, for the typically developing and spastic cerebral palsy groups, respectively. For both groups, the reliability was higher for data processing than for data acquisition. High inter-class correlation coefficient values were found for processing and acquisition reliability, with worst case values of 0.89 and 0.61, respectively. The standard error of measurement, expressed as a percentage of the average volumes, was smaller than 2.6 ml (4.8%) in all cases., Conclusions: The present analysis demonstrates the effectiveness of applying 3D freehand ultrasonography in a clinical setting for analysing healthy and pathological paediatric muscle., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Aim: The main goal of this validation study was to evaluate whether lower limb muscle weakness and plantar flexor rate of force development (RFD) related to altered gait parameters in children with cerebral palsy (CP), when weakness was assessed with maximal voluntary isometric contractions (MVICs) in a gait related test position. As a subgoal, we analyzed intra- and intertester reliability of this new strength measurement method., Methods: Part 1 -Intra- and intertester reliability were determined with the intra-class correlation coefficient (ICC2,1) in 10 typical developing (TD) children (age: 5-15). We collected MVICs in four lower limb muscle groups to define maximum joint torques, as well as plantar flexor RFD. Part 2 -Validity of the strength assessment was explored by analyzing the relations of lower limb joint torques and RFD to a series of kinematic- and kinetic gait features, the GDI (gait deviation index), and the GDI-kinetic in 23 children with CP (GMFCS I-II; age: 5-15) and 23 TD children (age: 5-15) with Spearman's rank correlation coefficients., Results: Part 1 -The best reliability was found for the torque data (Nm), with the highest ICC2,1 (0.951) for knee extension strength (inter) and the lowest (0.693) for dorsiflexion strength (intra). For plantar flexor RFD, the most reliable window size was 300 milliseconds (ICC2,1: 0.828 (inter) and 0.692 (intra)). Part 2 -The children with CP were significantly weaker than the TD children (p <0.001). Weakness of the dorsiflexors and plantar flexors associated with delayed and decreased knee flexion angle during swing, respectively. No other significant correlations were found., Conclusion: While our new strength assessment was reliable, intra-joint correlations between weakness, RFD, and gait deviations were low. However, we found inter-joint associations, reflected by a strong association between plantar- and dorsiflexor weakness, and decreased and delayed knee flexion angle during swing.

Aim: This cross-sectional investigation evaluates the reliability of estimating medial gastrocnemius anatomical cross-sectional area (aCSA) in typically developing and spastic cerebral palsy (SCP) cohorts. It verifies whether muscle volume estimations based on aCSA improve when aCSA is multiplied by muscle-tendon unit (MTU) or muscle length, and whether the resulting errors in volume estimations are smaller than changes after intervention., Method: Fifteen typically developing children (mean age 8y 2mo [SD 1y 5mo], six males, nine females) and 30 children with SCP (mean age 9y 2mo [SD 2y 5mo], 22 males, eight females, Gross Motor Function Classification System [GMFCS] level I=15, II=15) participated in the investigation. The SCP cohort was divided according to GMFCS level. A three-dimensional freehand ultrasound technique was used to estimate medial gastrocnemius aCSA, muscle volume, MTU, and muscle length. Estimated muscle volume (aCSA×MTU or muscle length) was compared with the measured muscle volume., Results: Anatomical cross-sectional area, muscle volume, and muscle length significantly differed between the typically developing and two SCP cohorts (p≤0.050). aCSA multiplied by either MTU or muscle length improved estimations of medial gastrocnemius volume. Leave-one-out cross-validation revealed an absolute difference with measured muscle volume of 3.77 ml (SD 2.90)., Interpretation: This investigation revealed that medial gastrocnemius muscle volume can be reliably estimated in a clinically feasible manner in typically developing children and those with SCP., What This Paper Adds: Medial gastrocnemius anatomical cross-sectional area (aCSA) can be reliably estimated in children with spastic cerebral palsy. The location of the anatomical cross-section should be taken with respect to muscle and not bone length. Medial gastrocnemius volume can be reliably estimated by multiplying aCSA and muscle length. The errors in volume estimations are smaller than reported differences after interventions., (© 2017 Mac Keith Press.)

A clinically feasible method to reliably estimate muscle-tendon unit (MTU) lengths could provide essential diagnostic and treatment planning information. A 3-D freehand ultrasound (3-DfUS) method was previously validated for extracting in vivo medial gastrocnemius (MG) lengths, although the processing time can be considered substantial for the clinical environment. This investigation analyzed a quicker and simpler method using the US transducer as a spatial pointer (US-PaP), where the within-session reliability of extracting the muscle-tendon unit (MTU) and tendon lengths are estimated. MG MTU lengths were extracted in a group of 14 healthy adults using both 3-DfUS and US-PaP. Two consecutive acquisitions were performed per participant, and the data processed by two researchers independently. The intra-class correlation coefficients were above 0.97, and the standard error of measurements below 3.6 mm (1.5%). This investigation proposes that the simplified US-PaP method is a viable alternative for estimating MG MTU lengths., (Copyright © 2018 World Federation for Ultrasound in Medicine and Biology. Published by Elsevier Inc. All rights reserved.)

During a Delphi consensus study, a new joint gait classification system was developed for children with cerebral palsy (CP). This system, whose reliability and content validity have previously been established, identified 49 distinct joint patterns. The present study aims to provide a first insight toward the construct validity and clinical relevance of this classification system. The retrospective sample of convenience consisted of 286 patients with spastic CP (3-18 years old, GMFCS levels I-III, 166 with bilateral CP). Kinematic and kinetic trials from three-dimensional gait analysis were classified according to the definitions of the Delphi study, and one classified trial was randomly selected for each included limb ( n = 446). Muscle weakness and spasticity were assessed for different muscle groups acting around the hip, knee, and ankle. Subsequently, Pearson Chi square tests, Cramer's V, and adjusted standardized residuals were calculated to explore the strength and direction of the associations between the joint patterns, and the different patient-specific characteristics (i.e., age, GMFCS level, and topographical classification) or clinical symptoms (muscle weakness and spasticity). Patient-specific characteristics showed several significant associations with the patterns of different joints, but the strength of most identified associations was weak. Apart from the knee during stance phase and the pelvis in the sagittal plane, the results systematically showed that the patterns with "minor gait deviations" were the most frequently observed. These minor deviations were found significantly more often in limbs with a lower level of spasticity and good muscle strength. Several other pathological joint patterns were moderately associated with weakness or spasticity, including but not limited to "outtoeing" for weakness and "intoeing" for spasticity. For the joints in the sagittal plane, significantly stronger associations were found with muscle weakness and spasticity, possibly because most of the evaluated muscles in this study mainly perform sagittal plane motions. Remarkably, the hip patterns in the coronal plane did not associate significantly with any of the investigated variables. Although further validation is warranted, this study contributes to the construct validity of the joint patterns of the Delphi consensus study, by demonstrating their ability to distinguish between clinically relevant subgroups in CP.

Background and Objective: Acquiring large anatomical volumes in a feasible manner is useful for clinical decision-making. A relatively new technique called 3D freehand ultrasonography is capable of this by combining a conventional 2D ultrasonography system. Currently, a thorough analysis of this technique is lacking, as the analyses are dependent on the software implementation details and the choice of measurement systems. Therefore this study starts by making this implementation available under the form of an open-source software library to perform 3D freehand ultrasonography. Following that, reliability and validity analyses of extracting volumes and lengths will be carried out using two independent motion-tracking systems., Methods: A PC-based ultrasonography device and two optical motion-tracking systems were used for data acquisition. An in-house software library called Py3DFreeHandUS was developed to reconstruct (off-line) the corresponding data into one 3D data set. Reliability and validity analyses of the entire experimental set-up were performed by estimating the volumes and lengths of ground truth objects. Ten water-filled balloons and six cross-wires were used. Repeat measurements were also performed by two experienced operators., Results: The software library Py3DFreeHandUS is available online, along with the relevant documentation. The reliability analyses showed high intra- and inter-operator intra-class correlation coefficient results for both volumes and lengths. The accuracy analysis revealed a discrepancy in all cases of around 3%, which corresponded to 3 ml and 1 mm for volume and length measurements, respectively. Similar results were found for both of the motion-tracking systems., Conclusions: The undertaken analyses for estimating volume and lengths acquired with 3D freehand ultrasonography demonstrated reliable design measurements and suitable performance for applications that do not require sub-mm and -ml accuracy., (Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.)

Aim: Despite the impact of spasticity, there is a lack of objective, clinically reliable and valid tools for its assessment. This study aims to evaluate the reliability of various performance- and spasticity-related parameters collected with a manually controlled instrumented spasticity assessment in four lower limb muscles in children with cerebral palsy (CP)., Method: The lateral gastrocnemius, medial hamstrings, rectus femoris and hip adductors of 12 children with spastic CP (12.8 years, ±4.13 years, bilateral/unilateral involvement n=7/5) were passively stretched in the sagittal plane at incremental velocities. Muscle activity, joint motion, and torque were synchronously recorded using electromyography, inertial sensors, and a force/torque load-cell. Reliability was assessed on three levels: (1) intra- and (2) inter-rater within session, and (3) intra-rater between session., Results: Parameters were found to be reliable in all three analyses, with 90% containing intra-class correlation coefficients >0.6, and 70% of standard error of measurement values <20% of the mean values. The most reliable analysis was intra-rater within session, followed by intra-rater between session, and then inter-rater within session. The Adds evaluation had a slightly lower level of reliability than that of the other muscles., Conclusions: Limited intrinsic/extrinsic errors were introduced by repeated stretch repetitions. The parameters were more reliable when the same rater, rather than different raters performed the evaluation. Standardisation and training should be further improved to reduce extrinsic error when different raters perform the measurement. Errors were also muscle specific, or related to the measurement set-up. They need to be accounted for, in particular when assessing pre-post interventions or longitudinal follow-up. The parameters of the instrumented spasticity assessment demonstrate a wide range of applications for both research and clinical environments in the quantification of spasticity.