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Gait Posture. 2014 Sep;40(4):545-8. doi: 10.1016/j.gaitpost.2014.06.013. Epub 2014 Jul 2.

A 3D mathematical model to predict spinal joint and hip joint force for trans-tibial amputees with different SACH foot pylon adjustments.

Author information

1
Department of Physical Therapy and Assistive Technology, National Yang Ming University, Taipei, Taiwan, ROC.
2
Rehabilitation Center, Taipei Veterans General Hospital, Taiwan, ROC.
3
Department of Physical Therapy, Chang Gung University, Taoyuan, Taiwan, ROC.
4
Department of Biomedical Research, Mackay Memorial Hospital, Tamshui, Taipei County, Taiwan.
5
Department of Physical Therapy and Assistive Technology, National Yang Ming University, Taipei, Taiwan, ROC. Electronic address: cschen@ym.edu.tw.

Abstract

A solid-ankle cushioned heel (SACH) foot is a non-joint foot without natural ankle function. Trans-tibial amputees may occur toe scuffing in the late swing phase due to a lack of active dorsiflexion. To address this problem, clinical guidelines suggests shortening the pylon to produce a smooth gait. However, this causes a leg length discrepancy, induces asymmetry in the hip joint, and causes an overload of L5/S1 joint force. Therefore, this study aimed to investigate the influence of different prosthesis pylons on the hip joint and L5/S1 joint forces. Ten subjects were recruited using leg length for normalisation. Four different pylon reductions (0%, 1%, 2%, and 3%) were used for gait analysis. A Vicon system and force plates were used to collect kinematic data and ground reaction force, respectively. The software package MATLAB was used to create a mathematical model for evaluating the symmetry and force of the hip joint and the low back force of the L5/S1 joint. The model was validated by the correlation coefficient (CC=0.947) and root mean square (RMS=0.028 BW). The model estimated that the 1% group had a symmetrical hip joint force and a lower L5/S1 joint force in the vertical direction. This study indicates that a 1% pylon shortening on a SACH prosthesis is appropriate for a trans-tibial amputee.

KEYWORDS:

Gait analysis; Low back force; Mathematic model; SACH foot; Trans-tibial amputee

PMID:
25042463
DOI:
10.1016/j.gaitpost.2014.06.013
[Indexed for MEDLINE]
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