A New Instrument to Assess Dynamic Balance in Children with Duchenne Muscular Dystrophy: Four Square Step Test and Its Validity, Reliability and Feasibility.

Aim: The aim of this study was to investigate validity, reliability and feasibility of the Four Square Step Test (FSST) in children with Duchenne Muscular Dystrophy (DMD).
Methods: The study included 44 children with DMD aged 5-12 years. The functional level of the children was determined by using the Brooke Lower Extremity Functional Classification (BLEFC). The concurrent validity of the FSST, a dynamic balance assessment, was investigated by analyzing the association between FSST and Timed Up and Go Test (TUG), North Star Ambulatory Assessment (NSAA) and Six-Minute Walk Test (6MWT) distance. The intra- and inter-rater reliability of the FSST was determined by using the Intra Class Correlation Coefficient (ICC) while the feasibility of the test was determined by calculating the percentage of children who successfully completed the test in accordance with the test instructions.
Results: The FSST score of the children (mean age 9.25 ± 2.14 years) was 11.91 ± 3.43 and the BLEFC level ranged from Level 1 (65.9%) to Level 3 (9.1%). FSST had positive, moderate relation with BLEFC (r = 0.447; p = .002); positive, strong relation with TUG (r _s  = 0.623), and negative, moderate correlations with NSAA (r _s  = -0.529) and 6MWT distance (r _s  = -0.592) (p < .001). Intra-rater (ICC: 0.965) and inter-rater (ICC: 0.991) reliability was "excellent," and the test was feasible with successful performance of 88% children.
Discussion: The FSST is a valid, reliable and feasible instrument to assess dynamic balance as well as having the ability to reflect falling risk and different functional levels of children with DMD.