Reliability and validity of using the Lokomat to assess lower limb joint position sense in people with incomplete spinal cord injury.

Antoinette Domingo,Tania Lam

doi:10.1186/1743-0003-11-167

Abstract

BackgroundProprioceptive sense (knowing where the limbs are in space) is critical for motor control during posture and walking, and is often compromised after spinal cord injury (SCI). The purpose of this study was to assess the reliability and validity of using the Lokomat, a robotic exoskeleton used for gait rehabilitation, to quantitatively measure static position sense of the legs in persons with incomplete SCI.MethodsWe used the Lokomat and custom software to assess static position sense in 23 able-bodied (AB) subjects and 23 persons with incomplete SCI (American Spinal Injury Association Impairment Scale level B, C or D). The subject’s leg was placed into a target position (joint angle) at either the hip or knee and asked to memorize that position. The Lokomat then moved the test joint to a “distractor” position. The subject then used a joystick controller to bring the joint back into the memorized target position. The final joint angle was compared to the target angle and the absolute difference was recorded as an error. All movements were passive. Known-groups validity was determined by the ability of the measure to discriminate between able-bodied and SCI subjects. To evaluate test-retest reliability, subjects were tested twice and intra-class correlation coefficients comparing errors from the two sessions were calculated. We also performed a traditional clinical test of proprioception in subjects with SCI and compared these scores to the robotic assessment.ResultsThe robot-based assessment test was reliable at the hip and knee in persons with SCI (P ≤ 0.001). Hip and knee angle errors in subjects with SCI were significantly greater (P ≤ 0.001) and more variable (P < 0.0001) than in AB subjects. Error scores were significantly correlated to clinical measure of joint position sense (r ≥ 0.507, P ≤ 0.013).ConclusionsThis study shows that the Lokomat may be used as a reliable and valid clinical measurement tool for assessing joint position sense in persons with incomplete SCI. Quantitative assessments of proprioceptive deficits after neurological injury will help in understanding its role in the recovery of skilled walking and in the development of interventions to aid in the return to safe community ambulation.Electronic supplementary materialThe online version of this article (doi:10.1186/1743-0003-11-167) contains supplementary material, which is available to authorized users.

Highlights

Proprioceptive sense is critical for motor control during posture and walking, and is often compromised after spinal cord injury (SCI)
The AB and SCI groups were not significantly different in terms of age (P = 0.51), but the proportion of males and females were different between groups
Comparison of absolute errors between groups, target angles, and repetitions Able bodied subjects had an overall average absolute error of 2.63° ± 0.17 at the hip and 4.05° ± 0.28 at the knee, while participants with SCI had an overall average of 6.64° ± 1.18 at the hip and 13.31° ± 1.75 at the knee across 20 trials (5 repetitions of 4 different target angles, Day 1) (Figure 2A)

Summary

Introduction

Proprioceptive sense (knowing where the limbs are in space) is critical for motor control during posture and walking, and is often compromised after spinal cord injury (SCI). Spinal cord injury (SCI) often results in complete or partial paralysis, affecting the ability to walk and participate in physical activity. Because of this diminished mobility, people with SCI are at high risk of secondary complications such as compromised cardiovascular health, pressure sores, and osteoporosis [1,2]. Task-specific gait retraining strategies that provide repeated practice of walking movements have been shown to improve walking function [4,5,6]. It is thought that the sensory information provided by the repeated practice of movements promotes neural plasticity through use-dependent mechanisms [4,7].

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