Byl Journal of Medical Case Reports 2012, 6:216 http://www.jmedicalcasereports.com/content/6/1/216 An analysis of the Framingham Study cohort found that as many as 30% of stroke survivors exhibit some kind of gait impairment [6], and after a stroke patients frequently demonstrate knee extensor weakness with decreased voluntary muscle activation [7,8]. Prior work suggests strength training can improve strength, gait speed and transitional movements in older adults [9-11] and using a robotic leg orthosis may enhance mobility [12]. However, the use of a mobile, intention-based ro- botic device designed to supplement knee extensor func- tion in patients post stroke has not been investigated. In this three-case series, we examined the effect of task- oriented mobility training on gait speed, quality and endurance using a novel, mobile, intention-based ro- botic leg orthosis (RLO) after each individual, stable, chronic post stroke, had reached a plateau in gait per- formance following BWSTT [12]. Case presentation The specific aim of this study was to test the hypothesis that use of a RLO during a four-week training trial would improve mobility and balance in patients in a stable chronic state after a stroke who had reached a plateau with BWSTT (that is, cessation of training progress). The protocol was approved by the University of California, San Francisco, Committee on Human Research and par- ticipants gave written informed consent. Key eligibility and inclusion criteria included: 40 to 65 years of age; at least one year post stroke; the ability to walk at least 10 meters with or without an ankle-foot orthosis and/or cane; having reached a plateau in gait performance with BWSTT; and independence in self-care. Participants with medical instability, a major cardiopulmonary defi- ciency, major depression or significant cognitive deficit, or those currently receiving gait training were excluded. Table 1 summarizes baseline characteristics of the three participants, with additional narrative below. Participant 1 was a 59-year-old Caucasian man, who had an ischemic left stroke six years previously with re- sultant right hemiparesis. He ambulated using a single- point cane and a hinged ankle-foot orthosis on his right leg. He used a hip-hike and circumduction strategy to clear his right foot during the swing phase of walking. During sit-to-stand activities he relied heavily on his un- involved left side. He had eight weeks of BWSTT one month before the RLO study and was continuing general post-stroke therapy. During the RLO study he trained three times per week (11 visits). Participant 2 was a 42-year-old Caucasian woman, with left hemiparesis after a right stroke 15 months pre- viously. She ambulated using a wide-based quad cane and a hinged ankle-foot orthosis. She exhibited dimin- ished weight acceptance on her involved left lower ex- tremity and maintained excessive hip and knee flexion Page 2 of 5 Table 1 Bionic neurorehabilitation study: participant baseline characteristics Assessment value Sex Age (years) Ethnicity Left lower extremity strength (lb) Right lower extremity strength (lb) Resting extensor tone (Ashworth scale)a Ankle Knee Affected side Participant 1 2 M F 59 42 2 4 Right 4 3 Left Caucasian Caucasian Caucasian 90a 105a 169 97a 105 138 3 F 62 1 1 Left during a shortened stance phase of gait. She demon- strated a ‘step-to’ gait pattern. During sit-to-stand activ- ities, she relied primarily on the use of her uninvolved right lower extremity. She completed BWSTT training one month before the RLO study and was continuing general therapy twice per week. During the RLO study she trained two times per week (eight visits). Participant 3 was a 62-year-old Caucasian woman with a history of a right middle cerebral artery aneurysm with third degree sub-arachnoid hemorrhage 10 years ago. She had also undergone right knee replacement two years previously. She usually wore a hinged ankle-foot orthosis and used a single-point cane when ambulating in the community, but did not use her cane at home. She exhibited 10 to 15 degrees of genu recurvatum on her left lower extremity during the stance phase of gait. She also had difficulty with eccentric control during stand-to-sit and when descending on stairs. During sit- to-stand, she tended to adduct and internally rotate both hips, creating a valgus angle of her knees. She tended to stand with most of her weight on her less impaired right leg. She had completed BWSTT training several months prior to the RLO study. During the RLO study, she trained four times per week (15 visits). A portable, wearable, battery-powered RLO (Tibion Bionic Leg, Tibion Corporation, Sunnyvale, CA, USA) was used during therapy to actively supplement concen- tric and eccentric quadriceps function on the partici- pants’ impaired side. The device uses internal sensors at the foot and knee joint to detect intention of movement and, once a variable force threshold is passed, it provides appropriate assistive and resistive adjustments (Figure 1). The RLO has three adjustable settings: threshold (the lower limit of force that must be crossed to initiate device assistance), assistance (the percentage of body weight provided through the limb during extension), and resistance (resistance to flexion during stair descent and stand-to-sit transfer). The therapist sets these