A new walking orthosis for paraplegics: hip and ankle linkage system.

For paraplegics, two major disadvantages of hip-knee-ankle-foot orthotic systems that have a medial single hip joint are the short stride and horizontal rotation of the pelvis. The authors consider the pelvic rotation is caused by two factors; one is the lack of a mechanism to assist hip flexion, and the other is fixed ankle joints that cause instability when the step length becomes longer. Users must rotate their pelvis to initiate a swing in their legs and to achieve stability by making their two legs as parallel as possible in order to avoid losing balance. To overcome those disadvantages, the authors developed a new orthosis named "HALO" (Hip and Ankle Linked Orthosis), which has a linking mechanism that connects both ankle joints with a medial single hip joint. This new orthosis allows users to keep both feet always parallel to the floor while walking, and assists the swinging of the leg when the contralateral ankle is flexed dorsally by loading. Gait analysis revealed that the pelvic rotation with "HALO" either in parallel bars or with Lofstrand crutches was within 20 degrees, which was within the physiologically normal level.