Arnold Allison S, Liu May Q, Schwartz Michael H, Ounpuu Sylvia, Dias Luciano S, Delp Scott L
Department of Mechanical Engineering, Stanford University, Stanford, CA, USA.
J Biomech. 2006;39(8):1498-506. doi: 10.1016/j.jbiomech.2005.03.026. Epub 2005 May 31.
Children with crouch gait frequently walk with improved knee extension during the terminal swing and stance phases following hamstrings lengthening surgery; however, the mechanisms responsible for these improvements are unclear. This study tested the hypothesis that surgical lengthening enables the hamstrings of persons with cerebral palsy to operate at longer muscle-tendon lengths or lengthen at faster muscle-tendon velocities during walking. Sixty-nine subjects who had improved knee extension after surgery were retrospectively examined. The muscle-tendon lengths and velocities of the subjects' semimembranosus muscles were estimated by combining kinematic data from gait analysis with a three-dimensional computer model of the lower extremity. Log-linear analyses confirmed that the subjects who walked with abnormally short muscle-tendon lengths and/or slow muscle-tendon velocities preoperatively tended to walk with longer lengths (21 of 29 subjects, p<0.01) or faster velocities (30 of 40 subjects, p<0.01) postoperatively. In these cases, surgical lengthening may have slackened the subjects' tight hamstrings and/or diminished the hamstrings' spastic response to stretch. Other subjects walked with muscle-tendon lengths and velocities that were neither shorter nor slower than normal preoperatively (22 of 69 subjects), and the semimembranosus muscles of most of these subjects did not operate at increased lengths or velocities after surgery; in these cases, the subjects' postsurgical improvements in knee extension may have been unrelated to the hamstrings surgery. Analyses of muscle-tendon lengths and velocities may help to distinguish individuals who have "short" or "spastic" hamstrings from those who do not, and thus may augment conventional methods used to describe patients' neuromusculoskeletal impairments and gait abnormalities.
蹲伏步态的儿童在腘绳肌延长手术后，在摆动末期和站立期行走时膝关节伸展通常会改善；然而，这些改善的机制尚不清楚。本研究检验了以下假设：手术延长使脑瘫患者的腘绳肌在行走时能够在更长的肌腱长度下运作或在更快的肌腱速度下延长。对69名术后膝关节伸展得到改善的受试者进行了回顾性检查。通过将步态分析的运动学数据与下肢三维计算机模型相结合，估计受试者半膜肌的肌腱长度和速度。对数线性分析证实，术前肌腱长度异常短和/或肌腱速度慢的受试者术后倾向于以更长的长度行走（29名受试者中的21名，p<0.01）或更快的速度行走（40名受试者中的30名，p<0.01）。在这些情况下，手术延长可能松弛了受试者紧绷的腘绳肌和/或减少了腘绳肌对拉伸的痉挛反应。其他受试者术前行走时的肌腱长度和速度既不比正常情况短也不比正常情况慢（69名受试者中的22名），并且这些受试者中的大多数半膜肌在术后并没有在增加的长度或速度下运作；在这些情况下，受试者术后膝关节伸展的改善可能与腘绳肌手术无关。对肌腱长度和速度的分析可能有助于区分有“短”或“痉挛性”腘绳肌的个体与没有的个体，因此可能增强用于描述患者神经肌肉骨骼损伤和步态异常的传统方法。
