A biomechanical analysis of loading patterns in children with cerebral palsy using the UpSee

SP7

D Meyer, J Angeli, M Kiefer, M Garcia, J Long

Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA

Background and Objective(s): Cerebral palsy (CP) often leads to secondary deficits including altered gait mechanics and musculoskeletal abnormalities (NIH, 2006). As a result, CP has been associated with limitations in physical activity (i.e., Raghavendra, 2011; Fauconnier, 2009; Orlin, 2014). While traditional physical therapy services can facilitate gains in these areas, solutions for increasing the amount and intensity of physical activity at home must also be explored. The UpSee is an upright mobility system that enables coupled walking for young children who cannot stand or walk independently. The system uses a shared sandal which allows a caregiver to facilitate supported stance and stepping patterns, and is a practical and low-cost solution to home activity programs emphasizing mobility for activities of daily living. To date, no description of the device's biomechanical impact has been published. Despite this, the popularity of the UpSee is evident, with more than 7,000 UpSee systems sold in the global market. The purpose of this study was to generate a preliminary understanding of loading patterns associated with UpSee use to inform clinical practice, as many therapy interventions enjoy only small to moderate effect sizes.

Study Design: Cross-sectional study design.

Study Participants & Setting: Force distributions associated with UpSee use were examined in 14 participants with Cerebral Palsy (6.7±1.5 years, GMFCS II/III=10 participants, GMFCS IV/V=4 participants) who were recruited from a volunteer sample at an academic medical center. Children were excluded based on height and weight (safe participation in the UpSee requires that the child participant's shoulders are below the naval of the adult-partner and that the weight of the child participant does not exceed 55 pounds).

Materials/Methods: All biomechanics data were gathered during a single visit to the medical center's motion analysis laboratory. Loading patterns were collected during 5 walking trials in the UpSee, using the Pedar insole pedobarography system (Novel GMBH). Trial data were averaged and compared to loading patterns collected during 5 “typical” gait trials, which included the use of orthotics and/or assistive devices when required. Novel software was used to calculate weight distribution in different regions of the foot (hindfoot, midfoot, forefoot) and the total foot, with data reported as maximum force normalized to percent body weight.

Results: Analysis with the Wilcoxon signed rank test found that total foot force was significantly lower when participants were in the UpSee system (M=54.2, SD=15.7) vs. in typical walking conditions (M=62.7, SD=23.1; z=−2.0251, p<0.05). This appears to be due to a significant decrease in force occurring in the midfoot during UpSee-assisted gait (M=13.8, SD=8.4; typical walking M=17.1, SD=14.5; z=−2.3084, p<0.05). Trends toward decreased hindfoot force and increased forefoot force were also observed in the UpSee condition relative to typical walking condition, but did not meet thresholds for statistical significance.

Conclusions/Significance: Typical walking conditions appear to be associated with greater total force and a pattern of forces that more closely approximate a physiologically “healthy” walking pattern (i.e. heel-toe gait). However, the UpSee also promoted active participation during ambulation, as participants did accept load through the lower extremities during UpSee-assisted stepping. Accordingly, this system affords a weight-bearing opportunity in the home/community that may provide a muscle and bone loading benefit over sedentary behavior.