This study investigated the effects of axillary crutch length on trunk muscle activity and lumbo-pelvic-hip complex movements during crutch gait. Eleven healthy men participated in this study. The participants performed a three-point gait with optimal, shorter, and longer crutch lengths. Weight-bearing (WB) side was determined as the dominant leg side. The electromyography (EMG) activity of the bilateral rectus abdominis (RA) and erector spinae (ES) muscles and lumbo-pelvic-hip complex movements were monitored using a three-dimensional motion system with wireless surface EMG. Differences in the EMG activity of RA and ES muscles and range of motion (ROM) of lumbar spine, pelvis, and hip among conditions were analyzed using one-way repeated-measures analysis of variance, and a Bonferroni correction was conducted. There was less RA muscle activity on the WB side under the optimal crutch length condition compared with shorter and longer crutch length conditions (p<.05). The EMG activity of the RA muscle on the non-WB side and ES muscle on the WB side were significantly decreased under the optimal crutch length condition compared with shorter crutch length condition (p<.05). No significant differences in the EMG activity of the ES muscle on the non-WB side and ROM of lumbo-pelvic-hip complex were found among conditions (p>.05). These findings indicate that the optimal crutch length improves the trunk muscle efficiency during crutch gait.

The purpose of this study was to determine which of several crutch-fitting techniques best predicts ideal crutch length. Ideal crutch length is defined as the length of the crutch, including accessories, obtained during stance when the crutch tip is 6 inches (15.2 cm) lateral and 6 inches(15.2 cm) anterior to the fifth toe and the axillary pad is 2.5 inches(6.4 cm) below the axillary fold. Forty four volunteers were measured for crutches using each of the following methods:(1) 77% of actual height, (2) actual height minus 40.6 cm, (3) actual height minus 45.7 cm, (4) olecranon to opposite third finger tip, (5) olecranon to opposite fifth finger tip, (6) 77% of arm span, (7) arm span minus 40.6 cm, (8) anterior axillary fold to heel plus 5.1 cm, (9) anterior axillary fold to heel plus 10.2 cm, (10) ideal crutch length. Of the techniques studied, the two involving anterior axillary fold to heel were found to be good predictors: anterior axillary fold to heel plus 5.1 cm and anterior axillary fold to heel plus 10.2 cm. Finally, two additional length estimates were derived using linear regression analyses. These estimates provided the best overall predictors based on anterior axillary fold to heel and actual height.

This paper proposes a wearable and motorized crutch control system for the patients using the conventional crutches. The conventional crutches have a few disadvantages such as the inconvenience caused by the direct contact between the ground and the armpit of the patients, and unstable gait patterns. In order to resolve these problems, the motorized crutch is designed as a wearable type on an injured lower limb. In other words, the crutch makes the lower limb to be moved forward while supporting the body weight, protecting the lower limb with frames, and rotating a roller equipped on the bottom of the frames. Also the crutch is controlled using the electromyography and two force sensing resistor (FSR) sensors. The electromyography is used to extract the walking intention from the patient and the FSR sensors to classify the stance and swing phases while walking. As a result, the developed crutch makes the patients walk enabling both hands to be free, as if normal people do.