Discussion
spasticity, thoracic movements, stroke, AFOs, knee flexion phenomenon, knee hyperextension, knee pain, AFO
STROKE
In the current study, we evaluated the effect of two AFOs, namely, AFO-OD and RAFO on the pelvic and thoracic movements in the gait of stroke patients after two weeks of training. Our results proved the hypothesis that there were direct effects on the thorax and pelvis movement using different AFOs in patients with stroke, and the effects were different.When the patient wore the AFO-OD, the pelvis rotated more to the non-paretic side at initial contact, which was followed by an increase in step length, speed, and change of SVA in stance, compared to not wearing the AFO. Some studies also showed that pelvic rotation anteriorly translated the hip, contributing to increased stride length and higher speed [In the RAFO group, the patient walking with AFO instead led to a significantly decreased change of SVA in stance (with AFO:27.91 ± 10.38°, without AFO: 31.29 ± 8.19°), which was even less than when the patient walked without AFO in the AFO-OD group (with AFO: 35.46 ± 12.38°, without AFO: 32.78 ± 11.11°). RAFO generated overlarge plantar flexion and dorsiflexion resistance, stopping ankle dorsiflexion and limiting shank forward inclination in the paretic stance. And the restriction of shank forward progression in the RAFO group also notably provided a control effect on the knee joint and prevented excessive knee flexion phenomenon in late stance. We even observed knee hyperextension (− 1.97°), which could impair walking speed, reduce gait symmetry, decrease gait efficiency, increase use of energy during walking, and might be associated with knee pain [Another notable finding in this study was that the thoracic rotation to non-paretic side at IC and CFO increased in the AFO-OD group and was positively correlated with the pelvic rotation at IC in both groups. The thorax and pelvis rotated synchronously in the same direction, which is called an in-phase rotation. In normal gait, the thorax and pelvis rotated more anti-phase (opposite direction) [The AFO-OD with plantarflexion resistance enabled the gradual movement to plantar flexion in loading response. With the kinematic chain of the lower limb, relatively upright alignment of the lower limb and improved pelvic rotational movement resulted in the improvement in velocity, step length, and shank progression, which meant better performance, although there was still in-phase rotation of the pelvis and thorax. The RAFO with plantarflexion and dorsiflexion stop decreased SVA progression in stance, affecting the forward tilt of the pelvis, and might result in knee hyperextension in late stance. This study suggested that clinicians should give more consideration to the effects of different types of AFOs on trunk posture in clinical gait training for stroke patients, and in the future, we would conduct more studies on AFOs based on this research and explore the correlation between lower limb biomechanics and trunk biomechanics in stroke gait.This study has some limitations. Firstly, the resistive moment of the AFO-OD was the same in this study, but it should probably be adjusted for each patient. The trim line and elasticity might affect the fixed resistance generated by the RAFO, but it could not be assessed in this study. Secondly, this study included a relatively wide range of patients in Brunnstrom stage III–V. Although the degree of spasticity of the patient was controlled by MAS, there might be potential differences in dissociation movements and spasticity of lower limbs among different Brunnstrom stages. Therefore, the gait of patients should be analyzed in each Brunnstrom stage in future studies.