Background: The L-STIFF tool of the Lokomat evaluates the hip and knee flexors and extensors spasticity in a standing position. It moves the lower limb at a controlled velocity, measuring joint resistance to passive movements. Since its reliability in children with cerebral palsy remains unknown, our goal was to evaluate the relative and absolute reliability of L-STIFF in children with cerebral palsy.
Methods: Reliability was determined in 16 children with cerebral palsy by two experienced therapists. The changes in resistive torque in hip and knee in both flexion and extension were measured. Relative and absolute reliability were estimated using the intraclass correlation coefficient, standard error of measurement, and minimal detectable change. Reliability was assessed on three levels: (1) intra- and (2) inter-tester within session, and (3) intra-tester between sessions.
Results: Intraclass correlation coefficients were moderate to excellent for intra-tester reliability (all p ≤ 0.01). The standard error of measurement ranged from 0.005 to 0.021 Nm/° (i.e., 7-16%) and minimal detectable change from 0.014 to 0.059 Nm/°. Inter-tester intraclass correlation coefficients ranged from 0.32 to 0.70 (all p ≤ 0.01), standard error of measurement ranged from 0.012 to 0.029 Nm/° (i.e., 6-39%), and minimal detectable change ranged from 0.033 to 0.082 Nm/°. L-STIFF reliability was better during fast and medium movement speeds compared to slow speeds.
Conclusions: The assessment tool L-STIFF is a promising tool for quantifying lower limb spasticity in children with cerebral palsy in a standing position. However, the results should be interpreted carefully.Implications for RehabilitationL-STIFF is a promising tool for evaluating lower limb spasticity in standing position.A special care must be given to the installation and alignment of the participant into the Lokomat to minimize erroneous spasticity measurement.Relative standard error of measurement and minimal detectable change should be used to analyze changes spasticity.
Keywords: Lokomat; Psychometric properties; cerebral palsy; mobility; muscle tone.