Stair ascent with an innovative microprocessor-controlled exoprosthetic knee joint

Abstract

Climbing stairs can pose a major challenge for above-knee amputees as a result of compromised motor performance and limitations to prosthetic design. A new, innovative microprocessor-controlled prosthetic knee joint, the Genium, incorporates a function that allows an above-knee amputee to climb stairs step over step. To execute this function, a number of different sensors and complex switching algorithms were integrated into the prosthetic knee joint. The function is intuitive for the user. A biomechanical study was conducted to assess objective gait measurements and calculate joint kinematics and kinetics as subjects ascended stairs. Results demonstrated that climbing stairs step over step is more biomechanically efficient for an amputee using the Genium prosthetic knee than the previously possible conventional method where the extended prosthesis is trailed as the amputee executes one or two steps at a time. There is a natural amount of stress on the residual musculoskeletal system, and it has been shown that the healthy contralateral side supports the movements of the amputated side. The mechanical power that the healthy contralateral knee joint needs to generate during the extension phase is also reduced. Similarly, there is near normal loading of the hip joint on the amputated side.

Does a Microprocessor-controlled Prosthetic Knee Affect Stair Ascent Strategies in Persons With Transfemoral Amputation?

“…Unlike Bellmann et al [4,5], we observed greater prosthetic limb hip extension power during pull-up than individuals without amputation. However, we also observed greater between-subject variability in both prosthetic limb hip extension power during pull-up and knee flexion angle at initial contact.…”

“…While using either device, decreased peak prosthetic ankle plantarflexion power at push-up and decreased peak prosthetic knee extension power during pull-up were observed relative to the intact limb and individuals without amputation due to the inability of the prosthetic ankle and knee to generate power. Similar to previous studies examining other microprocessor-controlled knees [4,5], peak intact ankle plantarflexion power was greater than the passive prosthetic ankle and much larger than the ankle of individuals without amputation. This large intact ankle power generation observed in individuals with transfemoral amputation is likely used to elevate the body while transitioning from the trailing intact limb to the leading prosthetic limb [19] and a compensation for the inability of the prosthetic knee to produce positive power during pullup.…”

“…Peak values for lower-extremity kinematics with the X2 1 knee were similar to those previously reported with civilians using a comparable prosthetic knee called the Genium 1 [4,5]. On average, participants had 30°more knee flexion at initial contact and 60°more knee flexion during swing while using the X2 1 device than while using a conventional microprocessorcontrolled knee.…”

“…However, we also observed greater between-subject variability in both prosthetic limb hip extension power during pull-up and knee flexion angle at initial contact. Similar to the work of Bellmann et al [4,5], participants in this study that contacted the stair in 35°to 40°of prosthetic knee flexion while using the X2 1 knee used a similar amount of hip power to extend the knee as individuals without amputation. However, when our participants contacted the stair with a prosthetic knee flexion angle similar to individuals without amputation (approximately 65°), they used approximately five times more hip power to extend the knee than individuals without amputation.…”

“…The X2 1 uses activity recognition and variable flexion/ extension resistance during step-over-step stair ascent to allow individuals with transfemoral amputation to load the knee while flexed without collapsing. Body elevation is achieved through prosthetic limb hip extension and contralateral intact ankle plantarflexion [5,6]. Previous microprocessor-controlled knees, such as the C-Leg 1 (Ottobock), do not provide sufficient resistance to prevent the knee from buckling while loaded in a flexed position.…”