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How Uneven Surfaces Affect Below-Knee Prosthetic Users and What Can Be Done About It

    Navigating uneven surfaces can be a common obstacle, particularly when outdoors. However, individuals with below-knee limb loss face even more significant challenges when dealing with uneven terrain.

     Uneven surfaces have a more significant biomechanical impact on below-knee prosthetic users.

    Outdoor falls are frequent among those with lower-limb amputations, with 73% of all falls attributed to environmental factors—such as uneven surfaces. These falls can result in injuries and often lead to reduced activity levels due to the fear of another fall. Therefore, it is essential to understand how these individuals navigate such terrains to better inform prosthetic designs and rehabilitation strategies. 

    So, researchers examined how individuals with unilateral below-knee amputation respond biomechanically when stepping on uneven surfaces. The study was published in the June 2023 issue of the Journal of Biomechanics.

    For most people, encountering holes, bumps, curbs, tilted sidewalks, and driveways leads to a moment of imbalance. But for someone with below-knee limb loss, it's a significantly greater biomechanical challenge.

    The study  

    The researchers used a walkway equipped with sensors and a force plate that could rotate up to 15 degrees in the coronal plane. This plate was hidden so that the tilt was unexpected. Then, the researchers compared how people with below-knee limb loss (who were using their prescribed prosthetic limbs) navigated this uneven terrain with those who didn't have any mobility impairments (the control group).

    Findings  

    The researchers observed that individuals with below-knee amputations exhibited more hip abduction, which refers to the movement of the leg away from the body. This was noted across all conditions, but particularly during unexpected inversions. Additionally, below-knee amputees displayed a wider recovery step after unexpected eversion, which may suggest challenges with balance.

    The study participants with below-knee limb loss showed more hip abduction and a wider recovery step after unexpected eversion, suggesting possible balance challenges.

    Despite these changes, the control group and the participants with below-knee amputation showed similar vertical Ground Reaction Force impulses, indicating that individuals with below-knee amputations could support their bodies effectively even on uneven ground. 

    Why this matters  

    Prosthetic feet that are currently prescribed for below-knee amputations are designed to store and return energy. They try to simulate a natural foot's shock absorption and propulsion, but they have limitations. These limitations become even more apparent on uneven surfaces.

    Prosthetic feet currently prescribed for below-knee limb loss are designed to simulate the shock absorption and propulsion of a natural foot, but they have limitations. These limitations become even more evident on uneven surfaces.

    Understanding the biomechanical responses is crucial in influencing rehabilitation methods and prosthetic designs. The study highlighted that individuals with below-knee amputation can support their bodies on uneven surfaces, but noticeable biomechanical differences can lead to increased energy expenditure.

    Additionally, walking on a sudden uneven surface caused a different biomechanical response for those with below-knee limb loss than when walking on a continuously uneven path. Insights from these findings can be critical for physical therapists, prosthetists, and even urban planners when designing inclusive spaces.

    The bottom line  

    Living in this world, we cannot expect smooth pavements everywhere. For those with below-knee amputations, every step can be a challenge. This recently concluded study provides essential information about their biomechanical responses and highlights the necessity for personalized rehabilitation approaches and prosthetic designs. As we strive for more inclusive communities, it becomes necessary to recognize and address such nuances.