Development of an active ankle foot orthosis for the prevention of foot drop and toe drag

In this study, we developed an active ankle-foot orthosis (AAFO) which can control the dorsi/ plantarflexion of the ankle joint to prevent foot drop and toe drag during walking. To prevent slapping foot after heel strike, ankle joint has to be controlled actively to minimize fore foot collision with the ground. In the late stance, ankle joint also has to be controlled to provide the toe clearance and help the push-off. 3D gait analyses were performed on five healthy subjects (age: 27.5plusmn2.1 years, height: 169.4plusmn4.3 cm, weight: 66.4plusmn2.3 kg) using a near-infrared 3D motion analysis system (Vicon 612, VICON, U.S.A.). Three different gait conditions were compared: the normal gait without AFO, the SAFO gait with the conventional plastic AFO, the AAFO gait with the developed AFO. As a result, the developed AAFO could preeminently induce the normal gait compared with SAFO. Additionally, AAFO can prevent the foot drop by proper plantarflexion during loading response and provide enough plantarflexion moment as driving force to walk forward by the sufficient push-off during pre-swing. AAFO also can prevent the toe drag by proper dorsiflexion during swing phase. In addition, SAFO can bring a very inefficient gait by the abnormal pelvic movement with a compensation for the limited movement of ankle joint. On the other hand, the AAFO can induce an efficient gait with the similar movement as in the normal gait. These results indicate that the developed AAFO may have more clinical benefits to treat foot drop and toe drag, compared with conventional AFOs, and also could be useful in polio patients or patients with other orthotic devices.

[1]  J. Barbenel,et al.  Peroneal stimulator; evaluation for the correction of spastic drop foot in hemiplegia. , 1996, Archives of physical medicine and rehabilitation.

[2]  R. B. Davis,et al.  A gait analysis data collection and reduction technique , 1991 .

[3]  J. Lehmann,et al.  Gait abnormalities in hemiplegia: their correction by ankle-foot orthoses. , 1987, Archives of physical medicine and rehabilitation.

[4]  J H Burridge,et al.  Indices to describe different muscle activation patterns, identified during treadmill walking, in people with spastic drop-foot. , 2001, Medical engineering & physics.

[5]  C L Vaughan,et al.  Orthotic management of gait in spastic diplegia. , 1997, American journal of physical medicine & rehabilitation.

[6]  Kim Young Ho,et al.  Development and Evaluation of a New Gait Phase Detection System using FSR Sensors and a Gyrosensor , 2004 .

[7]  S. Simon.  Gait Analysis, Normal and Pathological Function. , 1993 .

[8]  C. Sackley,et al.  The use of a balance performance monitor in the treatment of weight-bearing and weight-transference problems after stroke , 1992 .

[9]  R W Bohannon,et al.  Walking after stroke: comfortable versus maximum safe speed , 1992, International journal of rehabilitation research. Internationale Zeitschrift fur Rehabilitationsforschung. Revue internationale de recherches de readaptation.

[10]  J. Lehmann,et al.  Gait abnormalities in peroneal nerve paralysis and their corrections by orthoses: a biomechanical study. , 1986, Archives of physical medicine and rehabilitation.

[11]  J. Carr,et al.  Investigation of a new motor assessment scale for stroke patients. , 1985, Physical therapy.

[12]  Hans Jakob Christoph von Grimmelshausen.  Applications and design with analog integrated circuits , 1982 .

[13]  D. Wood,et al.  The effects of common peroneal stimulation on the effort and speed of walking: a randomized controlled trial with chronic hemiplegic patients , 1997, Clinical rehabilitation.

[14]  H. Herr,et al.  Adaptive control of a variable-impedance ankle-foot orthosis to assist drop-foot gait , 2004, IEEE Transactions on Neural Systems and Rehabilitation Engineering.