Bionic Leg for Active Robotic Stroke Rehabilitation

A couple years ago Medgadget wrote about a powered knee orthosis from Tibion Bionic Technologies developed for people with muscle problems, arthritis, and those post surgery to regain missing strength. A potential use of the Tibion bionic leg that was considered in the past was to help those suffering from the residual effects of a stroke to regain walking skills. Two years since, the company has reinvented its strategy, redesigned the device, and discovered that stroke patients can benefit greatly from the therapeutic advantages of the system.

The device is now indicated in the US for use by rehabilitation centers as a training aid in helping recover a proper walking gait. Software that controls the knee has been rewritten specifically to work for stroke rehab. The company says that its system is currently undergoing a 24 patient trial at New York Presbyterian hospital.

The key components of the Tibion Bionic Leg are:

  • A pressure-sensing shoe insert that detects and measures the amount of weight a patient is applying to his/her affected leg
  • A computer into which the therapist programs the amount of support to be provided to the patient’s affected leg during different tasks
  • Two motors within the Bionic Leg to provide that support
  • An angle sensor in the knee, which informs the computer what the patient is doing or likely to do.

Much of the therapeutic benefit of the Tibion Bionic Leg can be traced to its demand for active effort by the patient. The sensor in the patient’s shoe must detect a set amount of PT-chosen force applied by the patient before its motors can be activated. Information from the foot sensor, and an angle sensor in the knee, provide the onboard computer with information on whether the patient is applying force to the heel or ball of the foot, in what proportion, and in what sequence – and, based on algorithms programmed into that computer, determines what the patient is likely to be trying to do.

Because so much of gait and stepping is repetitive, the onboard computer can “think ahead” and assure the Tibion Bionic Leg is ready to provide expected assistance. Before the patient uses the Leg, the therapist asks the patient to stand, sit down and take steps. This adds information from sensors in the knee region to those transmitted from the foot, essentially “customizing” its sensor network to the patient’s way of walking.

When the patient puts no weight on the foot pressure sensor, a low-torque/high-speed motor within the Bionic Leg allows free-swinging operation, tracking the patient’s motions without impeding them. As soon as the patient applies pressure to the foot pressure sensor, and the knee angle decreases (knee extends, as when rising from a chair or climbing stairs), a high-torque/low-speed motor within the Tibion Bionic Leg provides lifting assistance (extending the knee), based on the degree of assistance dialed in by the therapist.

Conversely, when the patient applies weight to the foot pressure sensors and knee angle increases (as when sitting down or descending stairs), the high-torque motor provides braking assistance (resisting gravity while allowing knee to flex), based on the dialed-in degree of resistance

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