Background and Objectives: In long-term treated patients with neurological Wilson's disease, the ability to perform single-leg hopping was analyzed to quantify motor deficits. Materials and Methods: Twenty-nine long-term treated Wilson patients had to stand on one leg for at least 3 s and then perform at least five consecutive hops on this leg. Ground reaction forces and temporal patterns of hopping were recorded using an Infotronic® walking system, which consists of soft tissue shoes with a solid, but flexible plate containing eight force transducers allowing measurement of ground reaction forces (GRF) and temporal patterns of foot ground contact. Parameters of hopping were correlated with clinical scores and parameters of copper metabolism and liver enzymes. Patients' hopping data were compared with those of an age- and sex-matched control group. Results: Five severely affected Wilson patients were unable to hop. Time to the peak was significantly (p < 0.03) shorter in the remaining 24 patients compared to controls, but there was no difference in hopping frequency, the amplitude of ground forces and duration of foot contact. Twelve patients produced a second, sharp, initial "impact" force peak during ground contact in addition to the usual "active" force peak. Variability of the amplitude of the "active" peak was significantly inversely correlated with urinary copper elimination. Conclusions: The majority of long-term treated patients with neurological Wilson's disease was able to perform single-leg hopping. The presence of a sharp initial "impact" peak in the GRF-curves of hopping may indicate a mild deficit of limb/trunk coordination and subclinical cerebellar impairment.
Keywords: Wilson’s disease; ground reaction forces; limb/trunk coordination; optimization of therapy; single-leg hopping.