Quantifying repeatability of the Wartenberg pendulum test parameters in children with spasticity

The Wartenberg (pendulum) test is commonly used in a variety of studies involving healthy subjects, patients with CP, stroke patients, and other neurological conditions. There is some evidence that the Wartenberg test may be able to differentiate healthy people from patients with spasticity. The aim of the study was to explore the within-session repeatability of primary outcome measures, i.e. relaxation indices derived from the Wartenberg test when test was performed by single investigator. Patients were lying supine, thigh along the horizontal line. The lower legs were allowed to hang freely over the table edge, and the knee motion in response to leg drop from the horizontal position was measured using motion system VICON with external markers attached to each leg at greater trochanter, lateral knee epicondyle, and lateral malleolus. Data from four consecutive trials were collected at 1 min intervals. The set of relaxation indices and maximum velocity was calculated for each trial. Data of 21 children (42 limbs) who underwent the evaluation due to spasticity problem were analysed. The repeated measure ANOVA test, one way analysis of variance, coefficients of correlation and determination were used to determine the repeatability of the relaxation indices, the association between the indices in time, and influence of the spasticity origin on the variability. The results show that relaxation indices, did not differ between the trails in statistically significant way in our group of patients with spasticity, however they exhibited high within-session variability in the individual patients (16-90%). Therefore the variability of the relaxation indices may restrict the clinical usefulness of the indices to monitor the changes of spasticity over time. Further, our findings do not seem to conform to the earlier reports demonstrating a systematic, time-dependent, change in the relaxation indices when repeated measures were taken within a session. In conclusion, this study demonstrates that although the Wartenberg test is repeatable in groups of patients, it does not provide us with repeatable measures in individual patients, thus if it is to be used as a replacement for other clinical tests of spasticity further investigations are needed to explain the substantial variability of the indices.