Quantitative analysis of knee joint mobility in adult with Down syndrome

gravity is extremely relevant for the design and evaluation of the rehabilitative process. The level of gravity can be quantified by the Brunnstrom scale, which is mainly based on the evaluation of the attitude, joint mobility and muscle strength. The analysis of the ground reaction forces (GRF) can provide an estimation of walking in hemiplegic patients, providing a measurement of the loading and progression ability. According to Bowden et al. [1], the hemiplegic gravity should correlate significantly with propulsive impulse. The whole propulsion ratio generated by the paretic limb [1] was related to the Brunnstrom classification, providing to an organization in three hemiplegic classes: light with a mean propulsion ratio of 49%, mild with 36%, severe with 16% [1]. Differently from Brunnstrom scale, the quantification of GRF during locomotion allows analysing the motion function, but the mean values of the different groups do not allow performing a classification. The aim of the present study is to evaluate the possibility to determine a quantitative relationship between hemiplegic gravity and the contribution of the paretic limb during locomotion, based on an objective measurement of the GRF. Materials and methods: Two groups of subjects were analysed: 14 normal and 34 hemiplegic subjects. For the hemiplegic subjects, the inclusion criteria were: unilateral weakness and a minimum of 12 months after stroke. Subjects were excluded if: more than one stroke occurred, bilateral weakness was present, functional surgery had been performed. Hemiplegic subjects were classified according to Brunnstrom scale in light, mild and severe. All the subjects were analysed while walking and GRF were acquired by means of force platforms (Bertec by DEIS-LIB, Kistler by LAMB). For each subject, the whole propulsive ratio of the paretic limb was calculated as the ratio between the forward propulsion at the paretic limb and the sum of the two propulsive impulses [1]. A cluster analysis was performed, based on the propulsion ratio, aiming to the identification of thresholds for the classification and p < 0.01; VF1, p < 0.05; AF1, p < 0.01). Surface EMGs of muscle rectus femoris recorded during the first flexion exhibited large phasic activity in persons with DS, whereas the EMGs of controls were characterized by low tonic activity. Thus, the values of total EMG area measured in DS subject were higher with respect the values observed in control group (p < 0.05). We compared the total area of EMG with the mean values of acceleration during the first swing and we found that the reduction of acceleration detected in DS persons contributed for a large fraction of the variance of EMG area (R2 = 0.65); on the contrary, control group showed a significant smaller correlation (R2 = 0.12). With respect to the first three oscillations, DS persons showed values of damping coefficient lower than control subjects (p < 0.05). The values of stiffness coefficients in DS persons were higher than in controls across the first three swings but only for the first flexion it was statistical different between the two groups (p < 0.05). Discussion: The limited range of motion during the first knee flexion and the parallel increase of muscular activation observed in DS persons, indicate a possible neuronal compensatory mechanism performed by these subjects in order to increase stiffness and to improve joint stability [2]. References [1] Shumway-Cook A, Woollacott MH. Phys Ther 1985;65:1315–22. [2] Aruin AS, et al. Am J Ment Retard 1996;101:256–68. [3] Wartenberg R. Neurology 1951;1:18–24.