Test–retest reliability for performance-based outcome measures among individuals with arthrogryposis multiplex congenita

Abstract Background Most individuals with arthrogryposis multiplex congenita, a rare condition characterized by joint contractures in ≥ 2 body regions, have foot and ankle involvement leading to compromised gait and balance. The purpose of this study was to establish between-days, test–retest reliability for performance-based outcome measures evaluating gait and balance, i.e., the 10-m Walk Test, Figure-of-8 Walk Test, 360-degree Turn Test, and modified Four Square Step Test, among adolescents and adults with arthrogryposis multiplex congenita. Methods This reliability study included ambulatory participants, aged 10 to 50 years, with a medical diagnosis of arthrogryposis multiplex congenita. Participants completed performance-based measures, in a randomized order, on two separate occasions. Intraclass correlation coefficients with 95% confidence intervals and minimal detectable changes at the 90% and 95% confidence level were calculated. Results Participants included 38 community-ambulators with a median of 13 out of 14 upper and lower joint regions affected. Intraclass correlation coefficient point estimates and 95% confidence intervals ranged from .85-.97 and .70-.98, respectively. Minimal detectable changes were 10 to 39% of sample means and were largest for the modified Four Square Step Test. Conclusions Among individuals with arthrogryposis, gait speed per the 10-m Walk Test, as well as non-linear walking and dynamic balance assessment per the Figure-of-8 Walk and 360 Degree Turn Tests, have adequate test–retest reliability enabling evaluation of individual patient changes. Changes in groups of ambulatory individuals with arthrogryposis multiplex congenita may be reliably evaluated with all of the studied outcome measures.