The effect of lower-limb prosthetic alignment on muscle activity during sit-to-stand.

People with a transtibial amputation (TTA) have altered motion during daily tasks, which may be influenced by prosthetic alignment. This study aimed to determine the effect of medial/lateral prosthetic alignment shifts on muscle activity, measured by integrated electromyography (iEMG), and to compare muscle activity between people with and without TTA during sit-to-stand. We quantified ground reaction forces and three-dimensional center-of-mass position to interpret muscle activity results. Compared to the prescribed alignment, the bilateral knee extensors had greater activity in the medial alignment (p < 0.001) and the amputated side gluteus medius and less activity in the lateral alignment (p = 0.035), which may be a result of altered muscular requirements for postural control. In people with TTA, smaller intact side gluteus medius activity was associated with frontal plane motion of the center-of-mass, which was not observed in non-amputees. Compared to non-amputees, people with TTA had greater iEMG in the intact side tibialis anterior (p = 0.031) and amputated side rectus femoris (p < 0.001), which may be required to brake the body center-of-mass in the absence of amputated side tibialis anterior. These results suggest that lateral alignment shifts may reduce muscle activity during sit-to-stand for people with TTA and emphasize the importance of analyzing sit-to-stand in three dimensions.

Wagner KE ，Nolasco LA ，Morgenroth DC ，Gates DH ，Silverman AK ... -  《-》

Effects of anterior-posterior shifts in prosthetic alignment on the sit-to-stand movement in people with a unilateral transtibial amputation.

The sit-to-stand movement can be challenging for people with a transtibial amputation (TTA). The alignment of the prosthesis may influence the movement strategies people with TTA use to transfer from sit-to-stand by affecting foot placement. The purpose of this study was to determine how shifting the prosthetic foot anterior and posterior relative to the socket affects movement strategies used to transfer from sit-to-stand. To aid in interpretation, we compared movement strategies between people with and without TTA. Nine people with TTA and nine sex-, and age-matched non-amputee controls completed five self-paced sit-to-stand trials. With the posterior alignment, participants with TTA had 1) smaller braking GRF impulse on the prosthetic side and greater impulse on the intact side compared to the anterior alignment, 2) no significant differences between sides, which suggests greater braking impulse symmetry compared to anterior and prescribed alignments, and 3) smaller axial trunk range of motion compared to the prescribed alignment. There were also differences between participants with TTA and controls in braking GRF impulse, knee extension moment, anterior/posterior center of pressure position, and lateral and axial trunk range of motion. Based on these results, shifting the prosthetic foot posterior to the socket may be a useful tool to reduce braking impulse asymmetry and trunk motion in people with TTA during sit-to-stand. Thus, prosthetic alignment can have important implications for the comfort and ability of people with TTA to transfer from sit-to-stand as well as for development of secondary health conditions like low back pain, which is associated with compensatory movements.

Nolasco LA ，Morgenroth DC ，Silverman AK ，Gates DH ... -  《-》

Transtibial prosthetic alignment has small effects on whole-body angular momentum during functional tasks.

Due to the loss of ankle function, many people with a transtibial amputation (TTA) have difficulty maintaining balance during functional tasks. Prosthetic alignment may affect how people with TTA maintain balance as it affects ground reaction forces (GRFs) and centers of pressure. We quantified the effect of prosthetic alignment on dynamic balance during several functional tasks. Ten people with TTA and 10 controls without TTA completed tasks including walking and transitioning from a chair. Participants with TTA completed all tasks with their prescribed alignment and six shifted alignments, including ±10 mm anterior/posterior, medial/lateral, and ±20 mm in the vertical direction. For each task, we quantified dynamic balance as the range of whole-body angular momentum (H→WB) and quantified trunk range of motion (ROM) and peak GRFs. Compared to controls, participants with TTA using their prescribed alignment had a greater range of H→WB in the sagittal plane during walking, in all planes during sit-to-stand, and in the transverse plane during stand-to-sit. These results were associated with GRF and trunk ROM differences between participant groups. Alignment only affected the range of H→WB in the frontal plane during walking. The larger range for the tall alignment coincided with a greater difference in vertical GRF between intact and amputated legs compared to other alignments. Our findings suggest that people with TTA can adapt to small, translational, alignment changes to maintain similar levels of dynamic balance during chair transitions. Future work should investigate alignment changes during other tasks and in lower functioning individuals.

Nolasco LA ，Silverman AK ，Gates DH 《-》

Running-specific prostheses reduce lower-limb muscle activity compared to daily-use prostheses in people with unilateral transtibial amputations.

People with unilateral transtibial amputation (TTA) have biomechanical differences between the amputated and intact legs and compared to people without TTA during running. Additional biomechanical differences emerge between running with running-specific (RSPs) and daily-use prostheses (DUPs), but the associated underlying muscle activity is unclear. We collected surface electromyography from the biceps femoris long head, rectus femoris, vastus lateralis, and gastrocnemius as well as body kinematics and ground reaction forces in six people with and six people without TTA. We compared stance phase muscle activity and peak activation timing in people with and without TTA and between people using RSPs compared to DUPs during running at 3.5 m/s. Peak amputated leg hamstring activity occurred 34% (RSP) and 31% (DUP) earlier in stance phase compared to the intact leg. Peak amputated leg rectus femoris activity of people wearing DUPs occurred 8% and 9% later in stance phase than the intact leg of people wearing DUPs and amputated leg of people wearing RSPs, respectively. People with TTA had 45% (DUP) and 61% (RSP) smaller peak amputated leg knee extension moments compared to people without TTA, consistent with observations of quadriceps muscle activity. Using RSPs decreased overall muscle activity compared to DUPs.

Sepp LA ，Nelson-Wong E ，Baum BS ，Silverman AK ... -  《-》

Lumbar loads and trunk kinematics in people with a transtibial amputation during sit-to-stand.

People with a transtibial amputation have numerous secondary health conditions, including an increased prevalence of low back pain. This increased prevalence may be partially explained by altered low back biomechanics during movement. The purpose of this study was to compare trunk kinematics and L4-L5 lumbar loads in people with and without a transtibial amputation during sit-to-stand. Motion capture, ground reaction force and electromyographic data were collected from eight people with a unilateral transtibial amputation and eight people without an amputation during five self-paced sit-to-stand motions. A musculoskeletal model of the torso, lumbar spine, pelvis, lower limbs, and 294 muscles was used in a static optimization framework to quantify L4-L5 loads, low back muscle forces, and trunk kinematics. Participants with an amputation had greater peak and average L4-L5 loading in compression compared to control participants, with peak loading occurring shortly after liftoff from the chair. At the instant of peak loading, participants with an amputation had significantly greater segmental trunk lateral bending and trunk-pelvis axial rotation toward the intact side, and significantly greater segmental trunk axial rotation toward the prosthetic side compared to control participants. Participants with an amputation also had greater peak frontal plane and transverse plane segmental trunk angular velocity. The postural differences observed in people with a transtibial amputation were consistent with their ground reaction force asymmetry. The cumulative effects of the altered movement strategy used by people with an amputation may result in an increased risk for low back pain development over time.

Actis JA ，Nolasco LA ，Gates DH ，Silverman AK ... -  《-》