Developmental trajectories for young children with 16p11.2 copy number variation.

Copy number variation at 16p11.2 is associated with diverse phenotypes but little is known about the early developmental trajectories and emergence of the phenotype. This longitudinal study followed 56 children with the 16p11.2 BP4-BP5 deletion or duplication between the ages of 6 months and 8 years with diagnostic characterization and dimensional assessment across cognitive, adaptive, and behavioral domains. Linear mixed modeling revealed distinct developmental trajectories with deletions showing VIQ gains but declines in motor and social abilities while duplications showed VIQ gains and steady development across other domains. Nonparametric analyses suggest distinct trajectories and early cognitive abilities for deletion carriers who are ultimately diagnosed with intellectual disability and developmental coordination disorder as well as distinct trajectories and early social communication and cognitive abilities for duplication carriers diagnosed with ASD and intellectual disability. Findings provide predictions for patient developmental trajectories, insight into mean functioning of individuals with 16p11.2 at early ages, and highlight the need for ongoing monitoring of social and motor functioning and behavioral symptomatology to improve treatment planning. © 2017 Wiley Periodicals, Inc.

Determination of the optimal locations of surface-mounted markers on the tibial segment.

This study aims to determine optimal locations on the lower limbs for skin-mounted markers representing the tibial segment in three-dimensional (3D) gait analysis. It was predicted that markers located on the anterior tibial crest and malleoli would be least susceptible to soft tissue movement. Ten retro-reflective markers were attached to each tibial segment for 20 participants. Participants performed 10 walking trials and two different range-of-movement tasks (knee flexion/extension and ankle plantarflexion/dorsiflexion). The results showed a subset of four markers with inter-marker pair distances on the tibia have less than 1.6 mm variation (standard deviation (S.D.)) during walking. Minimal variation was also found in isolated ROM tasks, where marker pairs showed variability of less than 2.2 mm. Other marker locations, the femoral epicondyles and the tibial tuberosity varied up to 4 mm during walking and up to 11 mm during the isolated ROM tasks. The four marker locations that are optimal for defining the tibia are the proximal anterior tibial crest, the distal anterior tibial crest, the lateral malleolus and the medial malleolus.

A comparison of hip joint centre localisation techniques with 3-DUS for clinical gait analysis in children with cerebral palsy.

Functional calibration techniques have been proposed as an alternative to regression equations for estimating the position of the hip within the pelvic co-ordinate system for clinical gait analysis. So far validation of such techniques has focussed on healthy adults. This study evaluated a range of techniques based on regression equations or functional calibration procedures techniques in 46 children representative of those attending a major clinical gait analysis service against previously validated 3-D ultrasound techniques for determining the hip joint centre. Best agreement with ultrasound for the position of the hip within the pelvic coordinate system was found for the Harrington equations (mean 14 mm, sd 8 mm). Sphere fitting (mean≈22 mm, sd 11 mm) performed better than transformational techniques applied locally (mean≈33 mm, sd 12 mm) or globally (mean=30 mm, sd 14 mm). The participants with cerebral palsy showed reduced range of movement compared with healthy adults. Differences between these results and studies modelling the effects of simulated noise on functional techniques can probably be attributed to differences between that noise and the soft tissue displacements that are actually occurring.

Hip joint centre localization: Evaluation on normal subjects in the context of gait analysis.

Locating the position of the hip joint centre (HJC) is an important part of lower limb modeling for gait analysis. Regression equations have been used in the past but a range of functional calibration methods are now available. This study compared the accuracy of HJC localization from two sets of regression equations and five different functional calibration methods against three dimensional ultrasound (3-DUS) on a population of 19 able bodied subjects. Results show that the geometric sphere fitting technique was the best performer with mean absolute distance error of 15mm and 85% of measurements being within 20mm. The results also show that widely used regression equations perform particularly badly whereas the most recent equations performed very closely to the best functional method with a mean absolute error of 16mm and 88% of measurements being within 20mm. In vivo results are more than an order of magnitude worse than predictions using synthetic data suggesting that additional work is required before soft tissue artifact can be effectively modelled.

Validation of 3-D freehand ultrasound for the determination of the hip joint centre.

This paper describes the calibration process for 3-D free hand ultrasound (3-DUS). The Cambridge calibration technique was determined to produce the most repeatable and accurate results when determining the location of a reference object within a water bath. This note additionally validates 3-DUS as a potential measurement tool for the determination of the hip joint centre. It shows that 3-DUS can accurately determine the inter-HJC distance to within 4+/-2mm. This indicates potential for 3-DUS to be used as a gold standard measurement tool in the identification of the hip joint centre.

Quantification of soft tissue artifact in lower limb human motion analysis: a systematic review.

This systematic review critically evaluates the quantification of soft tissue artifact (STA) in lower limb human motion analysis. It has a specific focus on assessing the quality of previous studies and comparing quantitative results. A specific search strategy identified 20 published articles or abstracts that fulfilled the selection criteria. The quality of the articles was evaluated using a customised critical appraisal tool. Data extraction tools were used to identify key aspects reported in the articles. Most studies had small sample sizes of mostly young, slim participants. Eleven of the reviewed articles used physically invasive techniques to assess STA. STA was found to reach magnitudes of greater than 30 mm on the thigh segment, and up to 15 mm on the tibia. The range of soft tissue artifact reached greater than 25 mm in some cases when comparing the results of reviewed studies.

Obstacle crossing deficits in older adults: a systematic review.

This systematic review and critical evaluation of the literature investigates whether advanced age compromises obstacle crossing for unconstrained and time-constrained conditions. Eight electronic databases were searched for articles with terms relating to obstacle crossing during walking in their title, abstract or keywords. 15 articles were reviewed from an initial yield of 727 articles. The methodological quality of each article was critiqued and data extracted by two reviewers. Young and older adults were shown to contact obstacles infrequently when adequate time was available to adapt foot placement in relation to the obstacle. When less time was available to adjust the foot trajectory, older adults contacted obstacles more often than younger people. Older adults adopted a slower, more conservative obstacle crossing strategy. They demonstrated greater hip flexion during the swing phase of gait for the lead and trail limbs as well as greater hip flexion, hip adduction and ankle dorsiflexion during the stance phase for the lead and trail limbs. There was also evidence of reduced internal moments across the hip and ankle during key events in the obstacle crossing gait cycle in older adults. Despite using a more conservative obstacle crossing strategy, older adults are at greater risk of contacting obstacles for time-constrained conditions.