NSC Assistive Technology Research: Reciprocating Gait Orthoses for Paraplegia Patients

Background: Ambulation is a rehabilitation priority for many paraplegic patients, either for the psychological reasons or with the aim to achieve partial or full independence. It also provides the therapeutic benefits which are widely acknowledged to improve urinary drainage, to improve peripheral circulation, and to prevent the complication caused from bedridden, such as contracture, osteoporosis, urinary tract infection, and constipation etc. Some studies also found that ambulation will increase cardiopulmonary function. For those pediatric spinal cord-injured patients, the upright posture also profits the development of trunk and head control. There are a number of reciprocating gait orthoses (RGOs) available in practice for paraplegics, the problems of which have been slow, heavy and high energy-consumption. The biomechanical causes are not fully understood. Despite all the benefits that RGOs can offer, research and clinical experience indicated that most paraplegia patients choose wheelchair mobility after discharge to the community because it is faster, safer and needs less energy expenditure. Therefore, a biomechanical study of the pathological gait of paraplegia patients with RGOs is critically needed. The problems of currently applied RGOs need to be analyzed and remedial means to be proposed. In addition, a new RGOs system is also needed to serve as a research tool and a platform proving the remedial ideas.

Literature Review: There are many kinds of gait orthoses prescribed for paraplegics, which can be grouped according to the patterns of propulsion. The first type is a group of swing-through gait orthoses which include the Knee-Ankle-Foot orthoses (KAFO), Hip-Knee-Ankle-Foot orthoses (HKAFO), and the parapodium. The swing-through gait has high energy cost and users give up the orthoses easily. Swivel walkers belong to the second group, which enables paraplegic patients to ambulate in an upright position without the use of crutches or other walking aids. Patients progress by shifting the center of gravity; and increase the walking speed by swing their arms and by the rotation of the trunk. Loretta et al. compared the swivel gait with the swing gait, which shows the swivel gait has slower speed but more efficient gait which implies that lower metabolic cost and oxygen consumption are needed. Although the swivel walker has the advantages of providing low energy and hand-free walking, it was most criticized for its low walking speed and for its inability to ambulate on an uneven surface. The third one is a group of reciprocating gait orthoses which were developed with a belief that they would provide a more energy efficient gait than other gait orthoses. The LSU RGOs developed in the early 1980's has hip joints that are linked to act in a reciprocal pattern. In the early 1990s, there were two revised version of the LSU RGOs developed, ARGOs (Advanced RGOs using one cable and IRGOs (Isocentric RGOs) using a solid rocker bar. The hip guidance orthosis (HGOs) that provides friction-free hip joint also allows patients to walk reciprocally. WO, walkabout orthosis, is an infraperineal structure that also facilitates reciprocating walking. Comparing with HKAFO, RGOs was heavier, slower, and the energy cost (mL/kg/m) was higher although the energy consumption rate (mL/kg/min) was significantly higher for children in HKAFOs.

To achieve an efficient gait and to overcome the problem to be slow, the hybrid system, that is the combination of the FES and RGOs , had shown the possibility for improvement. Because this system used both the RGOs structural stability and muscle power stimulated by FES to decrease the activity of the trunk muscles in prevention from fatigue, it can provide more energy-efficient gait that increases the aerobic-anaerobic threshold of the patients in the long term.

Many orthotic options for paraplegia are available but only to provide limited walking functions with great energy consumption, which has been the reason for the frequent abandonment or the low utilization of the RGOs. To improve the design reducing the energy expenditure, it requires biomechanical analysis of the pathological gait such that the gait deviations and energy consuming mechanisms can be identified and remedial means can be implemented. There has been a recent research on the biomechanical analysis of an ARGOs user's gait and some possible mechanisms contributing to the high energy consumption were discussed. However, no further remedial action in terms of design parameters was suggested in their work. It is obvious that more research on the biomechanical study are needed to advance the development of orthotic solutions for paraplegia patients.

Gait determinants were to identify the sources which affect the energy expenditure. The determinants include pelvic rotation, pelvic list, knee flexion at mid-stance, foot and ankle motion, knee motion and lateral pelvic displacement. There were studies to evaluate the effects of these kinematic gait determinants on reduction of the vertical displacement of the Body Center of mass (BCOM). Gard and Childress found that the magnitude of the trunk's vertical excursion was virtually unaffected by pelvic list. Kerrigan pointed out the there are other primary gait determinants needed to explain the actual reduction in BCOM vertical displacement. A reduction of BCOM vertical excursion may have significant energy implications, but it requires kinetic consideration to prove the gait determinants do affect the energy expenditure.