Russell Esposito Elizabeth, Miller Ross H
Center for the Intrepid, Brooke Army Medical Center, Department of Rehabilitation Medicine, JBSA, Ft. Sam Houston, Texas, United States of America.
Extremity Trauma and Amputation Center of Excellence, Ft. Sam Houston, Texas, United States of America.
PLoS One. 2018 Jan 12;13(1):e0191310. doi: 10.1371/journal.pone.0191310. eCollection 2018.
Recent studies on relatively young and fit individuals with limb loss suggest that maintaining muscle strength after limb loss may mitigate the high metabolic cost of walking typically seen in the larger general limb loss population. However, these data are cross-sectional and the muscle strength prior to limb loss is unknown, and it is therefore difficult to draw causal inferences on changes in strength and gait energetics. Here we used musculoskeletal modeling and optimal control simulations to perform a longitudinal study (25 virtual "subjects") of the metabolic cost of walking pre- and post-limb loss (unilateral transtibial). Simulations of walking were first performed pre-limb loss on a model with two intact biological legs, then post-limb loss on a model with a unilateral transtibial prosthesis, with a cost function that minimized the weighted sum of gait deviations plus metabolic cost. Metabolic costs were compared pre- vs. post-limb loss, with systematic modifications to the muscle strength and prosthesis type (passive, powered) in the post-limb loss model. The metabolic cost prior to limb loss was 3.44±0.13 J/m/kg. After limb loss, with a passive prosthesis the metabolic cost did not increase above the pre-limb loss cost if pre-limb loss muscle strength was maintained (mean -0.6%, p = 0.17, d = 0.17). With 10% strength loss the metabolic cost with the passive prosthesis increased (mean +5.9%, p < 0.001, d = 1.61). With a powered prosthesis, the metabolic cost was at or below the pre-limb loss cost for all subjects with strength losses of 10% and 20%, but increased for all subjects with strength loss of 30% (mean +5.9%, p < 0.001, d = 1.59). The results suggest that maintaining muscle strength may prevent an increase in the metabolic cost of walking following unilateral transtibial limb loss, and that a gait with minimal deviations can be achieved when muscle strength is sufficiently high, even when using a passive prosthesis.
近期针对相对年轻且健康的肢体缺失个体的研究表明，肢体缺失后维持肌肉力量可能会减轻在更大规模的一般肢体缺失人群中通常所见的行走高代谢成本。然而，这些数据是横断面数据，肢体缺失前的肌肉力量未知，因此很难就力量和步态能量学的变化得出因果推断。在此，我们使用肌肉骨骼建模和最优控制模拟对肢体缺失（单侧经胫骨截肢）前后行走的代谢成本进行了一项纵向研究（25个虚拟“受试者”）。首先在具有两条完整生物腿的模型上进行肢体缺失前的行走模拟，然后在具有单侧经胫骨假肢的模型上进行肢体缺失后的模拟，采用一个成本函数来最小化步态偏差加权和与代谢成本之和。比较肢体缺失前后的代谢成本，并对肢体缺失后模型中的肌肉力量和假肢类型（被动、动力）进行系统修改。肢体缺失前的代谢成本为3.44±0.13焦耳/米/千克。肢体缺失后，如果维持肢体缺失前的肌肉力量，使用被动假肢时代谢成本不会高于肢体缺失前的成本（平均 -0.6%，p = 0.17，d = 0.17）。肌肉力量损失10%时，使用被动假肢的代谢成本增加（平均 +5.9%，p < 0.001，d = 1.61）。对于动力假肢，在肌肉力量损失10%和20%的所有受试者中，代谢成本等于或低于肢体缺失前的成本，但在肌肉力量损失30%的所有受试者中代谢成本增加（平均 +5.9%，p < 0.001，d = 1.59）。结果表明，维持肌肉力量可能会防止单侧经胫骨肢体缺失后行走代谢成本增加，并且当肌肉力量足够高时，即使使用被动假肢也能实现偏差最小的步态。
