Fig 1.
Transfemoral amputee subjects wearing the powered knee and ankle prosthesis.
Fig 2.
A partial factorial design was used to evaluate the contributions of three factors: powered plantarflexion, increasing ankle stiffness and knee swing initiation.
Fig 3.
Diagram of the finite state machine used to control walking.
Fig 4.
Impedance parameters modified across conditions.
A) Knee equilibrium angle, B) ankle equilibrium angle, and C) ankle stiffness were modified in early to mid-stance and late stance. Increasing ankle stiffness was initiated in early to mid-stance when the ankle angle (solid black line) began to dorsiflex. Swing initiation and powered plantarflexion were initiated in late stance when the vertical load (dashed black line) began to decrease.
Table 1.
Stride spatiotemporal parameters.
Fig 5.
Anterior/posterior (A/P) GRF for amputated and intact limbs.
Average positive and negative A/P GRF values are shown. Main significant effects of swing initiation (▲), powered plantarflexion (†), and increasing ankle stiffness (§) are denoted. Significant pairwise t-test results are indicated with brackets.
Fig 6.
Kinematics for hip, knee, and ankle joints of the amputated and intact limbs.
Group average results shown. Main significant effects of swing initiation (▲) and powered plantarflexion (†) are denoted.
Fig 7.
Stance phase joint moments for hip, knee, and ankle of the amputated and intact limbs.
Group average traces and average positive and negative values of joint moments are shown. Significant main effects of swing initiation (▲), powered plantarflexion (†), and significant interaction effects of powered plantar flexion and increasing stiffness (†*§) are denoted. Significant pairwise t-test results are indicated with brackets.
Fig 8.
Stance phase joint power for hip, knee, and ankle of the amputated and intact limbs.
Group average traces and average positive and negative values of joint power are shown. Significant main effects of powered plantarflexion (†) and significant interaction effects of powered plantar flexion and increasing stiffness (†*§) are denoted. Significant pairwise t-test results are indicated with brackets.
Fig 9.
Swing phase hip moment and power of the amputated and intact limbs.
Group average traces and average positive and negative values of hip moment and power are shown. Significant main effects of swing initiation (▲), powered plantarflexion (†), and increasing ankle stiffness (§), and significant interaction effects of powered plantar flexion and increasing stiffness (†*§) are denoted. Significant pairwise t-test results are indicated with brackets.
Fig 10.
Stance phase intact knee abduction moment.
Group average traces and average positive values of knee abduction moment are shown. Significant interaction effects of powered plantar flexion and increasing stiffness (†*§) are denoted. Significant pairwise t-test results are indicated with brackets.