Natural history of ankle function during gait in youth with Charcot-Marie-Tooth disease types 1 and 2

Charcot-Marie-Tooth disease (CMT) can cause progressive muscle weakness and contracture, leading to gait abnormalities such as increased and delayed peak ankle dorsiflexion and reduced ankle power generation in terminal stance. Understanding strength loss on ankle function during gait is important for interpreting treatment outcomes and evaluating new therapies designed to improve gait.

Do ankle kinematics and kinetics vary as a function of age, disease progression with associated loss of muscle strength and CMT type in youth with CMT types 1 and 2?

A prospective convenience sample of 45 participants with CMT1 and 2, ages 7-22 years, underwent comprehensive gait analysis. Seventeen patients underwent repeat analyses totaling 67 tests. Generalized mixed effects linear modeling was used to compare CMT1 versus CMT2 and to examine the effects of age on ankle strength, range of motion, kinematics, and kinetics within each CMT type.

Plantarflexor and dorsiflexor strength were less in CMT2 compared with CMT1 (p ≤ 0.05), while peak dorsiflexion in terminal stance (TST) was greater (p = 0.02). Peak plantarflexion moment and power generation were also less in CMT2 (p ≤ 0.02). In CMT1, peak dorsiflexion in TST increased with age through 13 years (p = 0.004); then plateaued in the normal range (p = 0.73). Peak ankle angle in mid-swing was closely related to the angle in TST (p < 0.001) following a similar pattern with age. In CMT2, no significant associations were observed between age, peak dorsiflexion in TST, and peak ankle angle in mid-swing (p ≥ 0.19). There were no consistent trends with age for individual patients with repeat tests.

The heterogeneity of joint level impairments and gait kinematics and kinetics point to the importance of having an in-depth understanding of gait at the individual patient level using comprehensive gait analysis including valid and reliable strength measures.