Tadashi Yasui

Development of an ankle – foot orthosis with an oil damper

The purpose of the present study was to develop an ankle – foot orthosis (AFO) that satisfies the requirements for an AFO for patients with hemiplegia as determined in a previous study. An oil damper has been introduced as an assistive device. The oil damper provides a resistive moment to plantar flexion of the ankle joint during initial stance on the paretic side. This function improves the insufficient eccentric contraction of the dorsiflexors. The magnitude of the resistive moment generated by this newly developed AFO can be changed easily to adjust its properties in accordance with the requirements of each patient. The mechanical properties of the AFO were measured, and the results showed that the AFO generated a sufficient resistive moment. Hemiplegic gaits with various types of AFOs were assessed, and it was found that the properties of the AFO affected the movements of the ankle, the knee, and the hip joints. The effects of the resistive moment on the alignment of the shank to the floor during initial stance are also discussed. Based on the results of this study, it is concluded that adjustability will be an essential feature for future AFOs.

Change of rocker function in the gait of stroke patients using an ankle foot orthosis with an oil damper: immediate changes and the short-term effects

Background: An ankle foot orthosis (AFO) using an oil damper (AFO-OD) to assist the first rocker during gait was previously developed but the effect on the other rocker functions has not been clarified. Objectives: The immediate and short-term effects on the gait of stroke patients with the AFO-OD were investigated from the viewpoint of the rocker function. Study Design: Crossover study. Methods: The gait of eight stroke patients in chronic phase without an AFO, with the AFO-OD, and the gait with AFO-OD after three weeks of continuous use and gait training were measured by 3D motion analysis. Results: Immediate changes observed on use of the AFO-OD were improvements in walking speed, the spatiotemporal parameters, and the angular change of dorsiflexion of the ankle joint. Three weeks of continuous AFO-OD use and gait training showed further improvements in walking speed and the spatiotemporal parameters as well as an increase in dorsiflexion angle and plantar flexor moment of the ankle joint of the paretic limb in stance. Conclusions: These changes produced improvement of the second rocker function, but improvement of the third rocker was insufficient. Results show the importance of gait training to take full advantage of an AFO.

Effects of plantar flexion resistive moment generated by an ankle-foot orthosis with an oil damper on the gait of stroke patients: a pilot study

Background: An ankle-foot orthosis with an oil damper was previously developed to assist the first rocker function during gait, but the effects of the amount of resistive moment generated on gait have not been clarified. Objectives: To measure the amount of resistive moment generated by the ankle-foot orthosis with an oil damper during gait and determine its effect on the gait of patients with stroke. Study Design: Preliminary cross-sectional study. Methods: The gait of four patients with stroke in the chronic phase was measured in four conditions: without an ankle-foot orthosis and with the ankle-foot orthosis with an oil damper generating three different amounts of resistive moment. Measurements were taken with a three-dimensional motion analysis system and a specially designed device to determine the resistive moment. Results: The resistive moment was observed in the former half in stance of the paretic limb, and its magnitude was less than 10 N m. Some gait parameters related to terminal stance and preswing were affected by the amount of resistive moment. The forward component of floor reaction force and the shank vertical angle showed peak values when the patients reported feeling most comfortable during gait. Conclusion: Although the resistive moment generated by the ankle-foot orthosis with an oil damper was small, it was sufficient to alter gait. Clinical relevance To maximize the effectiveness of ankle-foot orthoses, it is necessary to know the effects of resistive moment on the gait of patients with stroke. The ankle-foot orthosis with an oil damper assists the first rocker function in gait and also affects the gait in a later phase in stance. The peak values of some gait parameters coincided with patients reporting gait to be most comfortable. It is important to know that ankle-foot orthosis with an oil damper assistance in the first rocker alters the weight acceptance on the paretic limb and affects the gait parameters related to propulsion ability in stance.

Immediate-term effects of use of an ankle-foot orthosis with an oil damper on the gait of stroke patients when walking without the device.

Background: An ankle–foot orthosis using an oil damper is designed to enable natural movement of the ankle joint. Wearing an ankle–foot orthosis using an oil damper has been demonstrated to assist the first rocker in stroke patients, but its effect on their gait when not wearing it is unclear. Objectives: To determine the effect of use of ankle–foot orthosis using an oil damper on the gait of stroke patients with hemiparesis when not wearing the ankle–foot orthosis. Study design: Crossover study. Methods: The gait of eight stroke patients in the chronic phase when not wearing an ankle–foot orthosis was measured, using a three-dimensional motion analysis system, before using the ankle–foot orthosis using an oil damper and then without and with using the ankle–foot orthosis using an oil damper after 3 weeks of use. Differences in gait were compared between the three measurement conditions. Results: Use of ankle–foot orthosis using an oil damper significantly decreased preswing time and significantly increased the positive ankle joint power in stance when not wearing the ankle–foot orthosis using an oil damper. Conclusions: These changes indicate the promising therapeutic effects of ankle–foot orthosis using an oil damper use and suggest the ankle–foot orthosis using an oil damper’s potential as a therapeutic device. Clinical relevance After 3 weeks of use of an ankle–foot orthosis using an oil damper, which assists the first rocker, the gait of stroke patients in the chronic phase when not wearing the ankle–foot orthosis using an oil damper was improved. Preswing time was significantly decreased and positive ankle joint power was significantly increased. The ankle–foot orthosis using an oil damper, which assists the first rocker function with natural movement of the ankle joint during gait, has the potential to improve the gait of stroke patients after immediate-term use.

Gait improvement of hemiplegic patients using an ankle-foot orthosis with assistance of heel rocker function

The ankle-foot orthosis (AFO) with oil damper, GaitSolution (GS), was previously developed to make heel rocker function possible during the gait of hemiplegic patients. To clarify the characteristics of patients who show adaptation to GS use, a questionnaire was completed by the clinicians responsible for 99 patients with hemiplegia who participated in this study. Clinicians completed items concerning gait data of patients without AFO use and with GS use, adaptation to the use of GS, and patient opinion of GS use. Approximately 60% of patients achieved heel rocker function during the loading response of the paretic limb and improved gait when using GS. A comparison of the patients whose gaits were improved by GS more than by other AFOs revealed the use of GS was well suited to the gait of patients with a relatively higher Brunnstrom stage and a slightly flexed knee joint during the stance phase. Approximately 60% of patients reported feeling comfortable using GS, although patient comfort did not necessarily coincide with the results of gait assessment by clinicians. Patient comfort mainly depended on trunk posture and hip joint outward rotation; hip joint outward rotation could be improved using GS in the recovery phase but not in the maintenance phase. This result implies the importance of gait training in the early stage of rehabilitation.

Efficacy of a newly designed trunk orthosis with joints providing resistive force in adults with post-stroke hemiparesis

Background: Few studies have examined the efficacy of trunk orthoses that support the upper trunk and a paretic limb in stroke patients. To improve stability and alignment of the trunk and pelvis in hemiparetic patients, we developed a newly designed trunk orthosis that provides resistive force through spring joints. Objectives: This study aimed to determine the newly designed trunk orthosis’s biomechanical effects during level walking. Study design: Before-after trials must be better. Methods: Measurements were taken for nine chronic-phase (>2 years post-onset) stroke patients using a three-dimensional motion capture system and force plates under three experimental conditions: self-selected gait speed without the newly designed trunk orthosis, with the newly designed trunk orthosis, and after newly designed trunk orthosis removal. We analyzed and compared spatiotemporal and kinetic parameters of the paretic and non-paretic limbs and kinematic parameters of the trunk and bilateral limbs. Results: Several pre-swing gait parameters (e.g. hip joint flexion moment and ankle joint plantar flexion angle) after newly designed trunk orthosis removal were significantly increased compared to those without newly designed trunk orthosis. Step length of the paretic limb tended to increase after newly designed trunk orthosis removal. Conclusion: The newly designed trunk orthosis effectively modified trunk alignment, but larger improvements in kinetic and kinematic parameters were observed in the bilateral limbs after newly designed trunk orthosis removal than with the newly designed trunk orthosis. Clinical relevance Stroke patients improved only trunk malalignment while wearing the newly designed trunk orthosis. Gait after newly designed trunk orthosis removal was better than with the newly designed trunk orthosis. Positive changes after removal were mostly observed in pre-swing of the hemiparetic limb. The newly designed trunk orthosis might be effective for gait training in stroke patients.