Statistical kinematic modelling: concepts and model validity.

Data reduction techniques are applied to reduce the volume of data while maintaining its integrity. For cyclic motion data, a reliable overview comparing these methods is lacking. Therefore, this study aims to evaluate the features of the different data reduction techniques by applying them to large public data sets. The periodicity of cyclic motion can be exploited by either analysing a single cycle or studying a series of cycles. Analysing single cycles requires a pre-processing step to isolate the amplitude variability. Three different alignment techniques were evaluated, namely Linear length normalisation (LLN), piecewise LLN (PLLN) and continuous registration (CR). CR showed to remove the most phase variation. For the data reduction, three techniques were assessed (i.e., principal component analysis (PCA), principal polynomial analysis (PPA) and multivariate functional PCA (MFPCA)) based on the in- and out-of-sample error, the compactness and the computation time. The differences were found to be minimal. From our results, PPA appeared to be most useful for data compression. Further, we recommend PCA and MFPCA for classification and feature extraction purposes. We suggest the use of PCA when computation time is key and we advise the use of MFPCA when the inclusion of different data sources is desired. In contrast, the analysis of a series of cycles requires a pre-processing step to decompose the series. Further, a regression model was used to compensate for the difference in fundamental frequency. PCA on FC and MFPCA with splines were applied on the frequency compensated curves. Both methods performed as good.

Mobility and gait in adults with cerebral palsy: Evaluating change from adolescence.

BACKGROUND: Previous studies have looked at the short-term effectiveness of conservative and surgical treatment of children with cerebral palsy (CP), but few have explored the long-term outcomes into adulthood using gait analysis and patient-reported outcome measures. RESEARCH QUESTION: How do gait, mobility, and patient-reported outcomes in adults with CP who received specialized pediatric orthopedic care change from adolescence? METHODS: We identified 645 adults with 1) CP, 2) age 25-45 years, and 3) an adolescent instrumented gait analysis (IGA) at our center. Measurement outcomes included physical examination, IGA, and select domains of the Patient-Reported Outcomes Measurement Information System (PROMIS). RESULTS: Participants included 136 adults with CP; Gross Motor Function Classification System levels I (21 %), II (51 %), III (22 %), and IV (7%); 57 % males; and average age 16 ± 3/29 ± 3 years (adolescent/adult visits). There was no significant difference in gait deviation index, stride length, or gross motor function between adolescent and adult visits. There were statistically significant but not clinically meaningful declines in gait velocity. At adulthood, PROMIS results revealed limitations in physical function compared with a normative sample but no differences in depression, participation, or pain interference. SIGNIFICANCE: In this relatively homogeneous group of adults with CP who received orthopedic care from one center, gait and gross motor function showed no clinically meaningful change from adolescence, which differs from recent reports of declining mobility in adulthood. Expert orthopedic care, guided by IGA, may prevent losses in functional mobility for adults with CP.