Abstract
Objectives: To understand the residual locomotor effects of a traumatic brain injury (TBI) on unobstructed and obstructed walking.
Participants: Eight young, high-functioning adults with TBI and 4 healthy subjects.
Main outcome measures: Spatiotemporal gait parameters and their relation to specific clinical measures of severity and locomotor and balance abilities.
Results: Subjects with TBI walked slower and showed a tendency for greater foot clearances in all conditions. Slower walking was due to decreased stride lengths and not cadence, while higher foot clearances were due to placing the trailing foot farther from the obstacle and increasing hip flexion angles during avoidance.
Conclusions: The results suggest that this highly functional TBI population used increased caution. Measures of injury severity did not provide simple predictions of locomotor ability, but the one-legged stance test with eyes closed correlated to walking capacity.
THE PRIMARY and secondary effects of a traumatic brain injury (TBI) often result in combined physical and neuropsychological sequelae that greatly challenge the affected person's autonomy. In contrast to the vast literature on disruptions to cognitive and executive functions following a TBI, the study of motor deficits is relatively sparse. Some work has highlighted the equilibrium problems, particular during standing, in persons with a TBI. 1-4 Greenwald et al 5 have shown direct relations between sitting and standing posture at the time of admission (acute stage) and severity ratings including the initial Glasgow Coma Scale (GCS) score, posttraumatic amnesia (PTA), and coma duration. However, as pointed out by Esquenazi, 6 there is still an urgent need for gait-related studies in this population.
With respect to healthy individuals, biomechanical studies of gait have provided much information on the basic patterns for walking on the level (cf reference 7). Work that does exist on gait following a TBI has shown that general locomotor capacity recovers, at least partially, fairly quickly. Wade et al 4 showed significant increases in gait speed and step and stride lengths for severely impaired subjects with TBI after 2 to 6 weeks of rehabilitation. Hawkins et al 8 found that 92% of subjects with severe TBI returned home only 3 months following discharge, and locomotor ability, as rated with the subscale from the Functional Independence Measure, showed great improvements. Swaine and Sullivan 9 reported that at 6 weeks postinjury, approximately 50% of a group of 16 adults with a severe TBI were able to walk independently for 25 m on both even and uneven (outdoors) ground. Yet, despite these encouraging results, the same authors showed that 60% to 65% of subjects were found to be unable to run, hop, or jump without falling, suggesting that more complex locomotor activity can be still greatly affected following injury.
In terms of more detailed biomechanical analyses, it was shown 10 that a TBI group walked slower than healthy subjects, but, as compared to persons with a stroke, had greater average walking speeds and shorter single and double support phases as a proportion of the gait cycle. However, even subjects with TBI who walked with speeds over 1.0 m/s showed decreased stride lengths overall as compared to healthy subjects. Decreased walking speeds, but greater medial-lateral centre of mass velocities, have been recently interpreted 11 as showing increased instability in subjects with varying levels of TBI.
Level walking, however, only makes up a portion of our daily locomotor activity. Natural environments frequently require that we adjust our walking in order to avoid obstacles. Such activity is crucial to one's autonomy. Over the last decade, research has allowed us to begin to understand the more complex situation of gait adaptations for environmental obstructions. It is now known that level gait patterns, particularly the net knee moment of force patterns, are always reorganized to an active knee flexion at toe-off for obstacle avoidance. 12-14 In terms of more visually observable gait behavior, obstacle crossing speeds have been found to decrease monotonically with increasing obstacle heights, while step lengths increase from unobstructed walking but remain unchanged across obstacle heights. 15-17 Foot clearances over obstructions vary around 10 cm for moderate obstacles (ie, heights ranging from 5 to 20 cm), showing increases with increasing obstacle height. 16,17 Overall, although the muscular control for obstacle avoidance is the same for both limbs, 18 the challenge for safe foot trajectories is different between the leading and trailing limbs. Some studies have shown that the closer the foot is to the obstacle the lower the clearance. 18,19 Chen et al 16 have specifically shown that elderly subjects tend to place the foot further from the obstacle in order to exploit a higher point during the foot trajectory and, therefore, optimize foot clearance above the obstacle. Patla et al 20 showed that the trailing foot passes closer to the obstacle as compared to the leading foot for smaller and moderate obstacles, although trailing toe clearances were found to be similar on average, and more variable, to that of the leading toe with higher obstacles (around 26 cm high).
There are very few studies of anticipatory locomotor strategies of obstacle avoidance behavior in populations with neurological impairments. Two studies by Said and colleagues 21,22 have looked at obstacle avoidance by the leading limb in stroke survivors. While gait speed was not directly reported, Said et al 22 showed that stroke subjects had longer stepping times during the clearance of obstacles ranging from 1 to 8 cm. No data were reported for unobstructed walking. The same authors found higher clearances by stroke subjects for all obstacles, with no changes in foot proximity prior to clearance, but closer proximity after clearance. Therefore, because of their shorter stride lengths, subjects with stroke could exploit a higher part of the foot trajectory by using a greater proportion of swing prior to clearance (similar to what was mentioned above by the work of Chen et al 16).
Given the general scarcity of gait analyses, as well as clinical measures of gait capacity, following a TBI, much more work is needed to provide information important to improve diagnostics, to focus gait retraining, and to evaluate rehabilitation interventions for such a population. With this in mind, a high functioning population (able to walk at least 1 m/s and able to ambulate autonomously in the community without assistance) was chosen for this first project with the purpose of understanding the basic residual locomotor effects that follow a TBI as compared to known normal patterns. It was hypothesized that subjects with a TBI who are autonomous and highly functional would still show locomotor deficits in both unobstructed and obstructed walking.