Upper-extremity spasticity can be an obstacle during standing and walking because it aggravates hemiplegic posture and may interfere with stable balance and safe gait. Thus, changes in the mechanical properties of muscle tissue components and spasticity in the upper extremities can lead to impaired balance and gait characteristics. We determined that BTx injection in the hemiplegic spastic upper-extremity has a positive effect on postural balance and gait function in stroke patients. Our study quantitatively proved this hypothesis using plantar pressure and postural balance analysis. We also attempted to specify and present a possible explanation for the relationship between improvement in spasticity of the upper extremities and balance control with gait ability. Finally, as upper-extremity spasticity decreased, postural balance and gait function improved. A previous study suggested an association between upper-extremity BTx injection and stride time and ankle and knee range of motion (ROM) of the paretic leg in stroke patients using a 3D computerized motion analysis system. 26 The authors reported that injection of BTx reduced stride time in all stroke patients. In addition, when participants were stratified according to fast or slow stride time, a pronounced effect on ankle and knee ROM in slow-striding participants was observed.
Naturally, improvement in spasticity measured by MAS and MTS in the upper-extremity muscles was observed after BTxA injection. In foot pressure analysis, the overall load on the plantar side of the affected side was significantly reduced. Along with spatiotemporal parameters, we considered the symmetry index and symmetry ratio. 27 We found a numerical improvement in these symmetric parameters, however, we failed to determine any statistical significance. Further large-scale studies are needed to diversify the severity of spasticity to determine a clear link between these two different results. On the other hand, in postural balance analysis, the mean X-speed and horizontal distance in the eyes-opened test were significantly decreased at the post-intervention and follow-up evaluations compared to the baseline. In the correlation analysis, changes in upper extremities-y spasticity were significantly correlated with mean X-speed, mean Y-speed in the eye-closed test, task-performing time, distance in the ML direction, and total distance in the dynamic study. Postural balance analysis consistently demonstrated decreased movement speed in the ML and AP directions and shortened ML distance while standing. This meant that motion swing control was improved, therefore, we could speculate the possibility of improvement in balance with decreased asymmetry between the affected and less affected sides.
Since there was a statistically significant improvement in the ML distance in postural balance analysis, which has a similar meaning to symmetric parameters in the foot pressure analysis, it can be considered as indirect evidence that improving the flexion posture of the affected arm while walking may improve mediolateral balance.
The previously used MAS and MTS are methods used to evaluate patients in the resting state, therefore, dynamic evaluation was not available. It becomes possible to clarify functional and comprehensive effect of BTx by performing balance and gait evaluation. Efforts have been made to evaluate these aspects in a previous study, in particular, there was an attempt to analyze the angle of the elbow flexors during gait. 28 As mentioned above, our study would be clinically meaningful because of further attempts to evaluate postural balance. A few studies have already investigated this subject and have focused on upper trunk posture. Hefter at el. demonstrated that injections of BTx into the affected arm of hemiplegic patients improved abnormal lateral trunk flexion. This shift of the center of mass of the upper body toward the midline improves various gait parameters, including faster gait speed, reduced pre-swing duration of both legs, and increased step length of the non-affected leg. 29
Moreover, in plantar pressure analysis, gait speed (m/s) and stride length (m) increased post-injection. The DLSD (s) gradually decreased after injection. The SPD (s) on the hemiplegic side decreased post-injection. The single limb support duration (SLSD) (s) on the hemiplegic side decreased. These spatiotemporal gait parameters in foot pressure analysis might be improved because postural balance parameters were improved after BTxA injection, however, this finding was not statistically significant. However, in the correlation analysis, changes in upper-extremity spasticity were significantly correlated with spatiotemporal parameters such as DLSD, relative speed, stride length, relative stride length change, and SPD change on the affected side between pre- and post-injection. This could be explained by the small study population, which might have influenced the differences between the two types of analyses.
A recent systemic review suggested that instrumental and laboratory measures of gait improved after BTx injections in different muscle groups of the upper and lower extremities. 30 Gait changes were presented using various methods, including spatiotemporal, kinematics, kinetics, and electromyography. In particular, our study selected not only spatiotemporal parameters but also plantar pressure loading for gait measurements and additionally calculated gait symmetry. Furthermore, we considered a balance component which had significantly contributed to the overall walking function by further analysis of postural balance and confirmed the correlation between improvement in these parameters and improvement in upper-extremity spasticity.
This study has several limitations. First, an insole-type pressure analysis system has inherent limitations in measuring spatial parameters such as step length. Therefore, studies using other methods to examine the spatial parameters should be conducted. Second, there may be confounding factors such as age, sex, location of the stroke lesion, and functional aspects related to gait speed. Further research to investigate these confounding factors should be conducted to clarify the metrics of post-stroke gait. Third, the sample size was small. We expected that there would be a significant improvement in spatiotemporal parameters, however, the sample size was insufficient to determine the clear difference in the three points of evaluation. This finding should be supplemented by further studies.