School of Health and Welfare, Jönköping University, Box 1026, 55111, Jönköping, Sweden.
School of Science and Technology, Nottingham Trent University, Nottingham, UK.
Sci Rep. 2021 Apr 15;11(1):8263. doi: 10.1038/s41598-021-87657-2.
Methods used to assess quiet standing in unilateral prosthesis users often assume validity of an inverted pendulum model despite this being shown as invalid in some instances. The aim of the current study was to evaluate the validity of a proposed unilaterally-constrained pin-controller model in explaining postural control in unilateral prosthesis users. Prosthesis users were contrasted against the theoretical model as were able-bodied controls that stood on a platform which unilaterally constrained movement of the CoP. All participants completed bouts of quiet standing with eyes open, eyes closed and with feedback on inter-limb weight bearing asymmetry. Correlation coefficients were used to infer inverted pendulum behavior in both the anteroposterior and mediolateral directions and were derived from both kinematic (body attached markers) and kinetic (centre of pressure) experimental data. Larger, negative correlation coefficients reflected better model adherence, whilst low or no correlation reflected poorer model adherence. Inverted pendulum behavior derived from kinematic data, indicated coefficients of high magnitude in both mediolateral (all cases range 0.71-0.78) and anteroposterior (0.88-0.91) directions, irrespective of groups. Inverted pendulum behavior derived from kinetic data in the anteroposterior direction indicated validity of the model with large negative coefficients associated with the unconstrained/intact limbs (prosthesis users: - 0.45 to - 0.65, control group: - 0.43 to - 0.72), small coefficients in constrained/prosthetic limbs (prosthesis users: - 0.02 to 0.07, control group: 0.13-0.26) and large negative coefficients in combined conditions (prosthesis users: - 0.36 to - 0.56, control group: - 0.71 to - 0.82). For the mediolateral direction, coefficients were negligible for individual limbs (0.03-0.17) and moderate to large negative correlations, irrespective of group (- 0.31 to - 0.73). Data suggested both prosthesis users' and able-bodied individuals' postural control conforms well to that predicted by a unilaterally-constrained pin-controller model, which has implications for the fundamental control of posture in transtibial prosthesis users.
方法用于评估在单侧假体用户中的安静站立通常假设倒立摆模型的有效性，尽管在某些情况下已证明其无效。本研究的目的是评估拟议的单侧约束销控制器模型在解释单侧假体使用者姿势控制中的有效性。将假体使用者与理论模型进行对比，并与站立在平台上的健全对照者进行对比，该平台单侧限制 CoP 的运动。所有参与者均完成了睁眼、闭眼和反馈双侧负重不对称的安静站立。相关系数用于推断在前后方向和左右方向的倒立摆行为，并且源自运动学（附在身体上的标记）和动力学（中心压力）实验数据。较大的负相关系数反映了更好的模型依从性，而低或无相关性则反映了较差的模型依从性。源自运动学数据的倒立摆行为表明，在左右方向（所有情况下范围为 0.71-0.78）和前后方向（0.88-0.91）中，系数都很大，无论组别如何。源自前后方向动力学数据的倒立摆行为表明该模型具有有效性，与未约束/完整肢体相关的大负系数（假体使用者：-0.45 至-0.65，对照组：-0.43 至-0.72），与约束/假体肢体相关的小系数（假体使用者：0.02 至 0.07，对照组：0.13-0.26）以及与综合条件相关的大负系数（假体使用者：-0.36 至-0.56，对照组：-0.71 至-0.82）。对于左右方向，个体肢体的系数可以忽略不计（0.03-0.17），并且不论组别如何，相关系数均为中等至较大的负相关（-0.31 至-0.73）。数据表明，假体使用者和健全个体的姿势控制都很好地符合单侧约束销控制器模型的预测，这对胫骨假体使用者的基本姿势控制具有影响。
