Walking speed differentially alters spinal loads in persons with traumatic lower limb amputation.

Persons with lower limb amputation (LLA) perceive altered motions of the trunk/pelvis during activities of daily living as contributing factors for low back pain. When walking (at a singular speed), larger trunk motions among persons with vs. without LLA are associated with larger spinal loads; however, modulating walking speed is necessary in daily life and thus understanding the influences of walking speed on spinal loads in persons with LLA is of particular interest here. Three-dimensional trunk-pelvic kinematics, collected during level-ground walking at self-selected (SSW) and two controlled speeds (∼1.0 and ∼1.4 m/s), were obtained for seventy-eight participants: 26 with transfemoral and 26 with transtibial amputation, and 26 uninjured controls (CTR). Using a kinematics-driven, non-linear finite element model of the lower back, the resultant compressive and mediolateral/anteroposterior shear loads at the L5/S1 spinal level were estimated. Peak values were extracted and compiled. Despite walking slower at SSW speeds (∼0.21 m/s), spinal loads were 8-14% larger among persons with transfemoral amputation vs. CTR. Across all participants, peak compressive, mediolateral, and anteroposterior shear loads increased with increasing walking speed. At the fastest (vs. slowest) controlled speed, these increases were respectively 24-84% and 29-77% larger among persons with LLA relative to CTR. Over time, repeated exposures to these increased spinal loads, particularly at faster walking speeds, may contribute to the elevated risk for low back pain among persons with LLA. Future work should more completely characterize relative risk in daily life between persons with vs. without LLA by analyzing additional activities and tissue-level responses.

Hendershot BD ，Shojaei I ，Acasio JC ，Dearth CL ，Bazrgari B ... -  《-》

Trunk-Pelvis motions and spinal loads during upslope and downslope walking among persons with transfemoral amputation.

Larger trunk and pelvic motions in persons with (vs. without) lower limb amputation during activities of daily living (ADLs) adversely affect the mechanical demands on the lower back. Building on evidence that such altered motions result in larger spinal loads during level-ground walking, here we characterize trunk-pelvic motions, trunk muscle forces, and resultant spinal loads among sixteen males with unilateral, transfemoral amputation (TFA) walking at a self-selected speed both up ("upslope"; 1.06 ± 0.14 m/s) and down ("downslope"; 0.98 ± 0.20 m/s) a 10-degree ramp. Tri-planar trunk and pelvic motions were obtained (and ranges-of-motion [ROM] computed) as inputs for a non-linear finite element model of the spine to estimate global and local muscle (i.e., trunk movers and stabilizers, respectively) forces, and resultant spinal loads. Sagittal- (p = 0.001), frontal- (p = 0.004), and transverse-plane (p < 0.001) trunk ROM, and peak mediolateral shear (p = 0.011) and local muscle forces (p = 0.010) were larger (respectively 45, 35, 98, 70, and 11%) in upslope vs. downslope walking. Peak anteroposterior shear (p = 0.33), compression (p = 0.28), and global muscle (p = 0.35) forces were similar between inclinations. Compared to previous reports of persons with TFA walking on level ground, 5-60% larger anteroposterior and mediolateral shear observed here (despite ∼0.25 m/s slower walking speeds) suggest greater mechanical demands on the low back in sloped walking, particularly upslope. Continued characterization of trunk motions and spinal loads during ADLs support the notion that repeated exposures to these larger-than-normal (i.e., vs. level-ground walking in TFA and uninjured cohorts) spinal loads contribute to an increased risk for low back injury following lower limb amputation.

Acasio JC ，Shojaei I ，Banerjee R ，Dearth CL ，Bazrgari B ，Hendershot BD ... -  《-》

Comparing spinal loads in individuals with unilateral transtibial amputation with and without chronic low back pain: An EMG-informed approach.

Chronic low back pain (cLBP) is highly prevalent after lower limb amputation (LLA), likely due in part to biomechanical factors. Here, three-dimensional full-body kinematics and kinetics during level-ground walking, at a self-selected and three controlled speeds (1.0, 1.3, and 1.6 m/s), were collected from twenty-one persons with unilateral transtibial LLA, with (n = 9) and without cLBP (n = 12). Peak compressive, mediolateral, and anteroposterior L5-S1 spinal loads were estimated from a full-body, transtibial amputation-specific OpenSim model and compared between groups. Predicted lumbar joint torques from muscle activations were compared to inverse dynamics and predicted and measured electromyographic muscle activations were compared for model evaluation and verification. There were no group differences in compressive or anterior shear forces (p > 0.466). During intact stance, peak ipsilateral loads increased with speed to a greater extent in the cLBP group vs. no cLBP group (p=0.023), while during prosthetic stance, peak contralateral loads were larger in the no cLBP group (p=0.047) and increased to a greater extent with walking speed compared to the cLBP group (p=0.008). During intact stance, intact side external obliques had higher activations in the no cLBP group (p=0.039), and internal obliques had higher activations in the cLBP group at faster walking speeds compared to the no cLBP group. Predicted muscle activations demonstrated similar activation patterns to electromyographic-measured activations (r = 0.56-0.96), and error between inverse dynamics and simulated spinal moments was low (0.08 Nm RMS error). Persons with transtibial LLA and cLBP may adopt movement strategies during walking to reduce mediolateral shear forces at the L5-S1 joint, particularly as walking speed increases. However, future work is needed to understand the time course from pain onset to chronification and the cumulative influence of increased spinal loads over time.

Butowicz CM ，Golyski PR ，Acasio JC ，Hendershot BD ... -  《-》

Trunk muscle forces and spinal loads while walking in persons with lower limb amputation: Influences of chronic low back pain.

Persons with lower limb amputation (LLA) are at high risk for developing chronic low back pain (LBP), often with biomechanical factors considered as likely contributors. Here, trunk and pelvis kinematics, muscle forces, and resultant spinal loads were characterized in persons with LLA, with and without chronic LBP. Thirty-five persons with unilateral LLA - 19 with chronic LBP ("LLA-cLBP"), 16 without LBP ("LLA-nLBP") - and 15 (uninjured) persons without LBP ("CTR-nLBP") walked overground (1.3 m/s) while thorax and pelvis kinematics were tracked (and ranges of motion [ROM] computed), and used as inputs for a non-linear finite element model of the spine to estimate global and local muscle forces, and resultant spinal loads. In the frontal and transverse planes, thorax ROM were up to 66.6% smaller in LLA-nLBP versus LLA-cLBP (P < 0.001) and CTR-nLBP (P < 0.001). In the sagittal plane, pelvis ROM was 50.4% smaller in LLA-nLBP versus LLA-cLBP (P = 0.014). LLA-cLBP exhibited 45.5% and 34.2% greater peak local and global muscle forces, respectively, versus CTR-nLBP (P < 0.011). Up to 48.1% greater spinal loads were observed in LLA-cLBP versus CTR-nLBP (P < 0.013); peak compression and local muscle forces were respectively 20.2% and 41.0% larger in LLA-nLBP versus CTR-nLBP (P < 0.005). Despite differences in trunk and pelvis kinematics between LLA-cLBP and LLA-nLBP, trunk muscle forces and spinal loads were similar (P > 0.101) between these groups. Similar loading parameters regardless of LBP presence, while highly dependent on trunk muscle activation strategies, may mitigate further accumulation of mechanical fatigue. It remains important to understand the temporality of loading with respect to LBP onset following LLA.

Acasio JC ，Butowicz CM ，Dearth CL ，Bazrgari B ，Hendershot BD ... -  《-》

Trunk muscle activation patterns during walking among persons with lower limb loss: Influences of walking speed.

Persons with lower limb amputation (LLA) walk with altered trunk-pelvic motions. The underlying trunk muscle activation patterns associated with these motions may provide insight into neuromuscular control strategies post LLA and the increased incidence of low back pain (LBP). Eight males with unilateral LLA and ten able-bodied controls (CTR) walked over ground at 1.0 m/s, 1.3 m/s, 1.6 m/s, and self-selected speeds. Trunk muscle onsets/offsets were determined from electromyographic activity of bilateral thoracic (TES) and lumbar (LES) erector spinae. Trunk-pelvic kinematics were simultaneously recorded. There were no differences in TES onset times between groups; however, LLA demonstrated a second TES onset during mid-to-terminal swing (not seen in CTR), and activation for a larger percentage of the gait cycle. LLA (vs. CTR) demonstrated an earlier onset of LES and activation for a larger percentage of the gait cycle at most speeds. LLA walked with increased frontal plane trunk ROM, and a more in-phase inter-segmental coordination at all speeds. These data collectively suggest that trunk neuromuscular control strategies secondary to LLA are driven by functional needs to generate torque proximally to advance the affected limb during gait, though this strategy may have unintended deleterious consequences such as increasing LBP risk over time.

Butowicz CM ，Acasio JC ，Dearth CL ，Hendershot BD ... -  《-》