Biomechanical and Clinical Correlates of Swing-Phase Knee Flexion in Individuals With Spastic Cerebral Palsy Who Walk With Flexed-Knee Gait
ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION
2015; 96 (3): 511-517
To identify clinical and biomechanical parameters that influence swing-phase knee flexion and contribute to stiff-knee gait in individuals with spastic cerebral palsy (CP) and flexed-knee gait.Retrospective analysis of clinical data and gait kinematics collected from 2010 to 2013.Motion and gait analysis laboratory at a children's hospital.Individuals with spastic CP (N=34; 20 boys, 14 girls; mean age ± SD, 10.1±4.1y [range, 5-20y]; Gross Motor Function Classification System I-III) who walked with flexed-knee gait ≥20° at initial contact and had no prior surgery were included; the more-involved limb was analyzed.Not applicable.The magnitude and timing of peak knee flexion (PKF) during swing were analyzed with respect to clinical data, including passive range of motion and Selective Control Assessment of the Lower Extremity, and biomechanical data, including joint kinematics and hamstring, rectus femoris, and gastrocnemius muscle-tendon length during gait.Data from participants demonstrated that achieving a higher magnitude of PKF during swing correlated with a higher maximum knee flexion velocity in swing (ρ=.582, P<0.001) and a longer maximum length of the rectus femoris (ρ=.491, P=.003). In contrast, attaining earlier timing of PKF during swing correlated with a higher knee flexion velocity at toe-off (ρ=-.576, P<.001), a longer maximum length of the gastrocnemius (ρ=-.355, P=.039), and a greater peak knee extension during single-limb support phase (ρ=-.354, P=.040).Results indicate that the magnitude and timing of PKF during swing were independent, and their biomechanical correlates differed, suggesting important treatment implications for both stiff-knee and flexed-knee gait.
View details for DOI 10.1016/j.apmr.2014.09.039
View details for Web of Science ID 000350265400019
View details for PubMedID 25450128
Etiology of impaired selective motor control: emerging evidence and its implications for research and treatment in cerebral palsy
DEVELOPMENTAL MEDICINE AND CHILD NEUROLOGY
2014; 56 (6): 522-528
Selective motor control (SMC) impairment involves movement patterns dominated by flexor or extensor synergies that interfere with functional movements in children with cerebral palsy (CP). Emerging evidence on neural correlates of impaired SMC has important implications for etiology and for the treatment for children with CP. Early evidence on the microstructure of brain white matter assessed with diffusion tensor imaging in adult patients after stroke suggests that the rubrospinal tract may compensate for injury to the corticospinal tract. Furthermore, the observed changes on diffusion tensor imaging corresponded to the degree of SMC impairment. The rubrospinal tract may provide imperfect compensation in response to corticospinal tract injury, resulting in diminished SMC. Cortical mapping evidence in stroke patients indicates that loss of SMC is also associated with increased overlap of joint representation in the sensorimotor cortices. The severity of SMC impairment can be assessed with the recently developed Selective Control Assessment of the Lower Extremity, a validated observation-based measure designed for children with spastic CP. Recent advances in neuroimaging and assessment of SMC provide an opportunity to better understand the etiology and impact of impaired SMC, which may ultimately guide strategic treatment for children with CP.
View details for DOI 10.1111/dmcn.12355
View details for Web of Science ID 000335507500009
Functional Task Kinematics of the Thumb Carpometacarpal Joint
CLINICAL ORTHOPAEDICS AND RELATED RESEARCH
2014; 472 (4): 1123-1129
Abnormal biomechanical loading has been identified as an associated risk factor of osteoarthritis in the wrist and hand. Empirical data to date are insufficient to describe the role of altered biomechanics in thumb carpometacarpal (CMC) arthritis.This is a pilot study to evaluate motion analysis of the upper extremity while performing functional tasks. We wished to describe the in vivo kinematics of the thumb and hand in relation to the larger joints of the upper extremity in subjects without arthritis in functional positions at rest and while loading the CMC joint. If reproducible, we then planned to compare kinematics between these subjects and a subject with advanced thumb CMC arthritis.In vivo kinematics of the hand and upper extremity during the functional tasks of grasp, jar opening, and pinch with and without loading of the CMC joint were evaluated using cameras and a motion-capture system in four asymptomatic female subjects and one female subject with advanced radiographic (Eaton Stage IV) osteoarthritis.Kinematics of the hand and upper extremity can be reliably quantified. Loading of the CMC joint did not alter the hand and forearm kinematics in control subjects. In the subject with osteoarthritis, the adduction-extension deformity at the CMC joint resulted in kinematic alterations as compared with the four control subjects.This study represents preliminary steps in defining thumb CMC position, motion, and loading associated with activities of daily living. These findings enhance our understanding of motion at the CMC joint and how it differs in arthritic patients.Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
View details for DOI 10.1007/s11999-013-2964-0
View details for Web of Science ID 000332576400013
Brain microstructural development at near-term age in very-low-birth-weight preterm infants: An atlas-based diffusion imaging study
2014; 86: 244-256
At near-term age the brain undergoes rapid growth and development. Abnormalities identified during this period have been recognized as potential predictors of neurodevelopment in children born preterm. This study used diffusion tensor imaging (DTI) to examine white matter (WM) microstructure in very-low-birth-weight (VLBW) preterm infants to better understand regional WM developmental trajectories at near-term age. DTI scans were analyzed in a cross-sectional sample of 45 VLBW preterm infants (BW≤1500g, GA≤32weeks) within a cohort of 102 neonates admitted to the NICU and recruited to participate prior to standard-of-care MRI, from 2010 to 2011, 66/102 also had DTI. For inclusion in this analysis, 45 infants had DTI, no evidence of brain abnormality on MRI, and were scanned at PMA ≤40weeks (34.7-38.6). White matter microstructure was analyzed in 19 subcortical regions defined by DiffeoMap neonatal brain atlas, using threshold values of trace <0.006mm(2)s(-1) and FA >0.15. Regional fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated and temporal-spatial trajectories of development were examined in relation to PMA and brain region location. Posterior regions within the corona radiata (CR), corpus callosum (CC), and internal capsule (IC) demonstrated significantly higher mean FA values compared to anterior regions. Posterior regions of the CR and IC demonstrated significantly lower RD values compared to anterior regions. Centrally located projection fibers demonstrated higher mean FA and lower RD values than peripheral regions including the posterior limb of the internal capsule (PLIC), cerebral peduncle, retrolenticular part of the IC, posterior thalamic radiation, and sagittal stratum. Centrally located association fibers of the external capsule had higher FA and lower RD than the more peripherally-located superior longitudinal fasciculus (SLF). A significant relationship between PMA-at-scan and FA, MD, and RD was demonstrated by a majority of regions, the strongest correlations were observed in the anterior limb of the internal capsule, a region undergoing early stages of myelination at near-term age, in which FA increased (r=.433, p=.003) and MD (r=-.545, p=.000) and RD (r=-.540, p=.000) decreased with PMA-at-scan. No correlation with PMA-at-scan was observed in the CC or SLF, regions that myelinate later in infancy. Regional patterns of higher FA and lower RD were observed at this near-term age, suggestive of more advanced microstructural development in posterior compared to anterior regions within the CR, CC, and IC and in central compared to peripheral WM structures. Evidence of region-specific rates of microstructural development was observed. Temporal-spatial patterns of WM microstructure development at near-term age have important implications for interpretation of near-term DTI and for identification of aberrations in typical developmental trajectories that may signal future impairment.
View details for DOI 10.1016/j.neuroimage2013.09.053
View details for Web of Science ID 000330335300026
View details for PubMedID 24091089
Neonatal physiological correlates of near-term brain development on MRI and DTI in very-low-birth-weight preterm infants
2014; 5: 169-177
Structural brain abnormalities identified at near-term age have been recognized as potential predictors of neurodevelopment in children born preterm. The aim of this study was to examine the relationship between neonatal physiological risk factors and early brain structure in very-low-birth-weight (VLBW) preterm infants using structural MRI and diffusion tensor imaging (DTI) at near-term age. Structural brain MRI, diffusion-weighted scans, and neonatal physiological risk factors were analyzed in a cross-sectional sample of 102 VLBW preterm infants (BW ≤ 1500 g, gestational age (GA) ≤ 32 weeks), who were admitted to the Lucile Packard Children's Hospital, Stanford NICU and recruited to participate prior to routine near-term brain MRI conducted at 36.6 ± 1.8 weeks postmenstrual age (PMA) from 2010 to 2011; 66/102 also underwent a diffusion-weighted scan. Brain abnormalities were assessed qualitatively on structural MRI, and white matter (WM) microstructure was analyzed quantitatively on DTI in six subcortical regions defined by DiffeoMap neonatal brain atlas. Specific regions of interest included the genu and splenium of the corpus callosum, anterior and posterior limbs of the internal capsule, the thalamus, and the globus pallidus. Regional fractional anisotropy (FA) and mean diffusivity (MD) were calculated using DTI data and examined in relation to neonatal physiological risk factors including gestational age (GA), bronchopulmonary dysplasia (BPD), necrotizing enterocolitis (NEC), retinopathy of prematurity (ROP), and sepsis, as well as serum levels of C-reactive protein (CRP), glucose, albumin, and total bilirubin. Brain abnormalities were observed on structural MRI in 38/102 infants including 35% of females and 40% of males. Infants with brain abnormalities observed on MRI had higher incidence of BPD (42% vs. 25%) and sepsis (21% vs. 6%) and higher mean and peak serum CRP levels, respectively, (0.64 vs. 0.34 mg/dL, p = .008; 1.57 vs. 0.67 mg/dL, p= .006) compared to those without. The number of signal abnormalities observed on structural MRI correlated to mean and peak CRP (rho = .316, p = .002; rho = .318, p= .002). The number of signal abnormalities observed on MRI correlated with thalamus MD (left: r= .382, p= .002; right: r= .400, p= .001), controlling for PMA-at-scan. Thalamus WM microstructure demonstrated the strongest associations with neonatal risk factors. Higher thalamus MD on the left and right, respectively, was associated with lower GA (r = -.322, p = .009; r= -.381, p= .002), lower mean albumin (r = -.276, p= .029; r= -.385, p= .002), and lower mean bilirubin (r = -.293, p= .020; r= -.337 p= .007). Results suggest that at near-term age, thalamus WM microstructure may be particularly vulnerable to certain neonatal risk factors. Interactions between albumin, bilirubin, phototherapy, and brain development warrant further investigation. Identification of physiological risk factors associated with selective vulnerability of certain brain regions at near-term age may clarify the etiology of neurodevelopmental impairment and inform neuroprotective treatment for VLBW preterm infants.
View details for DOI 10.1016/j.nicl.2014.05.013
View details for Web of Science ID 000349667800020
View details for PubMedID 25068107