Stance and Swing Phase Ankle Phenotypes in Youth with Charcot-Marie-Tooth Type 1: an Evaluation Using Comprehensive Gait Analysis Techniques

Background: Charcot-Marie-Tooth disease (CMT) results in muscle weakness and contracture leading to a wide variety of gait issues including atypical ankle kinematics in both stance and swing. Knowledge of the stance and swing phase kinematic patterns for CMT type 1 (CMT1), the most common CMT type, will improve our un-derstanding of expected gait outcomes and treatment needs to improve gait function. Research question: What are the stance/swing phase ankle phenotypes in CMT1?Methods: A prospective convenience sample of 25 participants with CMT1, ages 7-19 years, underwent comprehensive gait analysis following standard procedures. Ankle phenotypes based on peak ankle dorsiflexion in terminal stance and mid-swing were defined and compared using linear mixed models.Results: Patients with CMT1 presented with three stance phase ankle phenotypes: 21 limbs (42 %) with reduced (mean 5 degrees, SD 2 degrees), 19 limbs (38 %) with typical (mean 11 degrees, SD 1 degrees) and 10 limbs (20 %) with excessive (mean 15 degrees, SD 2 degrees) peak dorsiflexion in terminal stance (p < 0.05). There were two swing phase phenotypes: 19 limbs (38 %) with typical (mean-1.7 degrees, SD 1.5 degrees) and 31 limbs (62 %) with excessive (mean-5.6 degrees, SD 1.4 degrees) plantarflexion in mid-swing (p < 0.002). Eleven patients (44 %) had ankles that were classified into different stance groups, and 9 patients (36 %) had ankles that were classified into different swing groups. The most common combination of stance/swing ankle phenotypes was decreased dorsiflexion in terminal stance with increased plantarflexion in mid-swing (16 sides, 32 %).Significance: This study shows that youth with CMT1 have multiple combinations of combined ankle kinematics for stance and swing. The ankle phenotypes identified in this study reflect contributions of both dorsi/plantar-flexor weakness and plantarflexor contracture, which require different treatment approaches. Comprehensive gait analysis can distinguish between multiple ankle phenotypes to assist in determining the most appropriate treatment to improve gait for individual patients.