Transtibial amputees can and do use the same strategies and to the same extent as able-bodied individuals when dealing with challenges of gait stability and adaptability, according to recently published study results.

“One important condition for stable walking is that we keep our body’s center of mass within the boundaries of our continuously changing base of support,” Han Houdijk, PhD, assistant professor at the Faculty of Human Movement Sciences and the Research Institute MOVE of the VU University Amsterdam, the Netherlands, told O&P Business News. “In our previous studies we found that people adapt their gait pattern in terms of gait speed, step length and step frequency to ensure a sufficient margin of stability — ie, sufficient distance between the moving center of mass and boundaries of the base of support — during normal gait and during situations in which stability was challenged. The purpose of this study was to test whether people walking with lower limb prostheses were able to use similar strategies as able-bodied people to regulate walking stability during perturbed and unperturbed walking.”

Gait stability in transtibial amputees

Ten individuals with unilateral transtibial prostheses and nine age-matched controls walked in a Computer Assisted Rehabilitation Environment (CAREN). To manipulate gait stability, researchers imposed medio-lateral (ML) translations, while a gait adaptability task (GA-task) was used in which patients had to hit virtual targets with markers guided by their knees to provoke an adaptive gait pattern. Main outcome measures included walking speed, step length, step frequency, step width and selected measures of gait stability, including backward and ML margins of stability (MoS).

 

Han Houdijk

Overall, researchers found that amputees walked more slowly vs. able-bodied individuals, with wider steps and a lower step frequency, resulting in larger ML MoS, but smaller backward MoS for amputees. Both groups decreased step length and increased step frequency and step width in response to the balance perturbation, according to study results, while walking speed did not change significantly in response to the perturbation. These adaptations to perturbation increased ML and backward MoS. Study results showed that both groups decreased step length and increased step width to perform the GA-task, but did not change step frequency and walking speed. ML and backward MoS were maintained in both groups.

“Despite the limitations of their prosthesis, people with transtibial amputation can and do preserve and enhance gait stability using similar stepping strategies compared with able-bodied people, resulting in similar margins of stability between both groups,” Houdijk said. “Training these stepping strategies might be an effective intervention to enhance gait stability in amputees with lower degrees of walking ability compared with those in this study.”

The researchers were surprised by the results because it is generally believed lower limb amputees have limitations in their walking patterns that limit their gait stability, Houdijk said. Not only were the transtibial amputees able to successfully withstand the perturbations like able-bodied individuals, but they also did not need to use extra or alternative strategies to ensure sufficient margins of stability.

Researchers were also surprised to find that the lower self-selected walking speed of the amputees did not seem to contribute to enhanced margins of stability. Their lower walking speed is thus probably not a strategy to be more stable but occurs for other reasons.

“It should be noted, however, that these conclusions apply to this specific group of transtibial amputees who all had a relatively high level of walking ability,” Houdijk said. “Generalization of these results to people with higher levels of amputations or lower levels of walking ability is not necessarily warranted and needs to be investigated in the future.”

Future of clinical practice

With help from the CAREN system, Houdijk and colleagues hope to learn how patients with challenges of gait stability adapt walking strategies, which could help them develop training interventions.

“Now that we know which strategies are required for obtaining a stable gait pattern and that these strategies can be exploited successfully by people with a lower limb amputation, we can develop adequate training interventions aimed at improving gait stability,” Houdijk said.

Houdijk told O&P Business News that they are currently investigating whether the results from their current study apply to other patient populations, specifically to patients post-stroke. They are also interested in investigating whether they can train patients with inferior walking ability to use stable walking strategies with the CAREN system. — by Casey Murphy