The influence of frontal alignment in the advanced reciprocating gait orthosis on energy cost and crutch force requirements during paraplegic gait

Reduction of energy cost and upper body load during paraplegic walking is considered to be an important criterion in future developments of walking systems. A high energy cost limits the maximum walking distance in the current devices, whereas wrist and shoulder pathology can deteriorate because of the high upper body load. A change in alignment of the mechanical brace in the frontal plane, i.e. abduction, can contribute to a more efficient gait pattern with sufficient foot clearance with less pelvic lateral sway. A decrease in pelvic lateral sway after aligning in abduction results in a shift of the centre of mass to the swing leg crutch which may result in a decrease in required crutch force on stance side to maintain foot clearance. Five paraplegic subjects were provided with a standard Advanced Reciprocating Gait Orthosis (ARGO) and an ARGO aligned in 4 different degrees of abduction (0°, 3°, 6° and 9°). After determining an optimal abduction angle for each of the subjects, a cross over design was used to compare the ARGO with the individually optimised abducted orthosis. An abduction angle between 0° and 3° was chosen as optimal abduction angle. Subjects were not able to walk satisfactory with abduction angles 6° and 9°. A significant reduction in crutch peak force on stance side was found (approx. 12% , p < 0.01) in the abducted orthosis. Reduction in crutch force time integral (15%) as well as crutch peak force on swing side (5%) was not significant. No differences in oxygen uptake as well as oxygen cost was found. We concluded that an abduction angle between 0° and 3° is beneficial with respect to upper boHy load, whereas energy requirements did not change

FES-supported standing up by independent control of three global variables - a modelling study

According to the work of Jacobs [1], we propose to control standing-up by applying independent controllers of three global variables (length l and orientation ϕ of the vector between ankle and body center of mass (CoM) and the orientation θ of the trunk). Furthermore, we propose to control l by modulating the activation of mono-articular muscles and to control ϕ and θ by modulating the activation of biarticular muscles (see also [1]). This division of tasks between mono-and biarticular muscles was found in postural control in cats [2]. Our simulations indicate that effective and well co-ordinated standing up may be achieved using this concept, allowing for a range of initial postures and arm support forces

The influence of frontal alignment in the advanced reciprocating gait orthosis on energy cost during paraplegic gait

Reduction of energy cost and upper body load during paraplegic walking is considered to be an important criterion in future developments of walking systems. A high energy cost limits the maximum walking distance in the current devices, whereas wrist and shoulder pathology can deteriorate because of the high upper body load. A change in alignment of the mechanical brace in the frontal plane, i.e. abduction, can contribute to a more efficient gait pattern with sufficient foot clearance with less pelvic lateral sway. A decrease in pelvic lateral sway after aligning in abduction results in a shift of the centre of mass to the swing leg crutch which may result in a decrease in required crutch force on stance side to maintain foot clearance. Five paraplegic subjects were provided with a standard Advanced Reciprocating Gait Orthosis (ARGO) and an ARGO aligned in 4 different degrees of abduction (0°, 3°, 6° and 9°). After determining an optimal abduction angle for each of the subjects, a cross over design was used to compare the ARGO with the individually optimised abducted orthosis. An abduction angle between 0° and 3° was chosen as optimal abduction angle. Subjects were not able to walk satisfactory with abduction angles 6° and 9°. A significant reduction in crutch peak force on stance side was found (approx. 12% , p < 0.01) in the abducted orthosis. Reduction in crutch force time integral (15%) as well as crutch peak force on swing side (5%) was not significant. No differences in oxygen uptake as well as oxygen cost was found. We concluded that an abduction angle between 0° and 3° is beneficial with respect to upper boHy load, whereas energy requirements did not change

Speed dependence of crutch force and oxygen uptake: Implications for design of comparative trials on orthoses for people with paraplegia

Objective: To determine speed dependence of crutch force and oxygen uptake, and to discuss the implications of differences in self-selected walking speed between orthoses in a comparative trial.\ud Design: Cross-sectional comparison.\ud Setting: Treadmill experiments and gait laboratory experiments were performed at five and three different imposed walking speeds, respectively.\ud Patients: Five paraplegic subjects with lesions between T9 and T12 were included. All subjects had experience with ambulation using the advanced reciprocating gait orthosis (ARGO) as well as walking on a treadmill.\ud Main Outcome Measures: Crutch force time integral (CFTI), crutch peak force on stance and swing side (CPFstance and CPFswing), oxygen uptake (Vo2), oxygen cost (Eo2).\ud Results: Vo2, Eo2, and CFTI were strongly dependent on walking speed. CPFstance and CPFswing were less dependent. However, depending on the clinically relevant difference that should be detected in a comparative trial, the peak forces can still be confounded by walking speed.\ud Conclusion: CFTI, CPFswing, Vo2, and Eo2 should be adjusted for walking speed if differences in walking speed between orthoses are found, but this correction is relevant only if there is no effect modification. Such modification (different slopes between orthoses) cannot be excluded for the studied outcome measures. In addition, because determination of effect modification is difficult in small studies, standardization of walking speed, by means of a three-point design, is recommended.\ud \u

Validity and reproducibility of crutch force and heart rate measurements to assess energy expenditure of paraplegic gait

Objective: To determine the validity and reproducibility of heart rate (HR) and crutch force measurements to estimate energy expenditure during paraplegic walking. Usefulness of these outcome measures in comparative trials was assessed in terms of responsiveness.\ud Design: Cross-sectional validity was determined using one single (first) measurement. Longitudinal validity as well as reproducibility were calculated using repeated measurements.\ud Setting: Oxygen uptake and HR during steady state as well as axial crutch load were measured at subjects' self-selected walking speeds.\ud Patients: Ten subjects with thoracic-level spinal cord injury were included in the study. All subjects had considerable experience with ambulation in the advanced reciprocating gait orthosis (ARGO).\ud Main Outcome Measures: Oxygen uptake ( O2, mL/min) and oxygen cost (Eo2, mL/m) were used as criterion standards. Crutch peak force (CPF), crutch force time integral (CFTI), HR, and physiological cost index (PCI) were used to estimate energy expenditure.\ud Results: The PCI was found to be sensitive to detect differences between sessions in criterion standard (r = .86). Smallest detectable difference (ie, point where difference exceeds measurement error) ranged from approximately 15% for CPF to 33.7% and 41.8% for Eo2 and PCI, respectively.\ud Conclusions: Although PCI is expected to be a valid measure for within-patient differences in O2, responsiveness was lower compared to Eo2 and CPR. The limited number of patients who can be included in studies on paraplegic locomotion requires reproducible outcome measures. Therefore, CPF and Eo2 are advocated in favor of PCI.\ud \u