Prosthetic Ankle Motion in Bilateral Transfemoral Amputees

In able-bodied (non-disabled) individuals, the ankle joint primarily functions to reduce shock absorption, aid in foot clearance during the swing phase, and serve as an axis of rotation for the foot. Prosthetic ankles that are currently available for use in lower limb prostheses provide considerably less function than their anatomical counterparts. Increased ankle motion in the sagittal plane may improve the gait of persons with lower limb amputations while providing a more versatile prosthesis. The primary aim of this study was to examine and quantify changes in the gait of four male bilateral transfemoral amputees who walked with different prosthetic ankle configurations. The two configurations examined included: (1) Baseline with only two Seattle LightFoot2 prosthetic feet, and (2) Endolite Multiflex Ankle units and Seattle LightFoot2 prosthetic feet. Gait analyses performed while the amputee subjects wore each prosthetic ankle configuration were compared between prosthetic configurations and with a control group of able-bodied subjects. The amputee group's mean (SD) freely-selected walking speeds, 0.74 (0.19) m/s and 0.81 (0.15) m/s, while wearing the Baseline and Multiflex Ankle units, respectively, were less than that of the control subjects, 1.35 (0.10) m/s. However, no difference in walking speed, step length, cadence, or ankle, knee, and hip joint moments and powers among the amputee subjects were observed while wearing the two ankle configurations. Sagittal plane ankle range of motion increased in all subjects, while the amputee group increased power generation at their hips to compensate for reduced energy return at their prosthetic ankles. The amputee subjects noted in subjective questionnaires following each gait analysis that the Multiflex Ankles provided more comfort than the Baseline configuration when walking but did not increase the perceived effort to walk. Therefore, since our data indicate that the addition of the Multiflex Ankles increased the versatility and comfort of the prosthesis without considerably altering the amputee group's gait characteristics, we recommend that prosthetic ankle mechanisms be considered when fitting prostheses on persons with transfemoral amputations.