Kirby R L, McLean A D, Eastwood B J
Department of Medicine, University, Halifax, Nova Scotia, Canada.
Arch Phys Med Rehabil. 1992 Jan;73(1):73-7.
The hypothesis that the static and dynamic forward stability of an occupied wheelchair would increase as a function of the caster diameter was tested in 20 able-bodied subjects. A device was attached to the wheelchair frame so that casters with different diameters could be used. With platform testing of static stability, the occupied wheelchair equipped with casters with diameters of 10.2, 20.3, 25.4, and 33.0cm, tipped at mean (+/- 1SD) angles of 23.8 degrees (+/- 1.3 degrees), 25.2 degrees (+/- 1.4 degrees), 26.1 degrees (+/- 1.4 degrees), and 28.2 degrees (+/- 1.9 degrees), respectively. The relationship between static stability (y, in degrees) and caster diameter (x, in cm) can be expressed by the equation y = 23.5-.0196 chi + .00484 x2 (p = .0001). Dynamic stability was tested by having subjects descend a 5 degree ramp, by gravity alone, from progressively farther up the ramp until a full forward tip occurred (footrests contacted the floor) when the wheelchair struck a 5-cm-high obstruction with sufficient speed. The mean tipping speeds for the dynamic tests were .85 (+/- .08), .85 (+/- .08), .89 (+/-.07), and 1.04 (+/- .14) m/sec for the wheelchair fitted with the caster diameters ranging from smallest to largest, respectively. The relationship between dynamic stability (y, tipping speed in m/sec) and caster diameter (chi, in cm) can be expressed by the equation y = .788 + .0139 chi-.00110 chi 2 + .0000276 chi 3 (p = .0001). The relationship between caster diameter and forward wheelchair stability should be considered in wheelchair design and prescription.
在20名身体健全的受试者中，对占用轮椅的静态和动态向前稳定性会随着脚轮直径的变化而增加这一假设进行了测试。在轮椅框架上连接了一个装置，以便能够使用不同直径的脚轮。通过平台测试静态稳定性，配备直径为10.2、20.3、25.4和33.0厘米脚轮的占用轮椅，分别以平均（±1标准差）23.8度（±1.3度）、25.2度（±1.4度）、26.1度（±1.4度）和28.2度（±1.9度）的角度倾斜。静态稳定性（y，单位为度）与脚轮直径（x，单位为厘米）之间的关系可以用方程y = 23.5 - 0.0196x + 0.00484x²表示（p = 0.0001）。动态稳定性通过让受试者仅靠重力从斜坡上越来越远的位置下降一个5度的斜坡来测试，直到当轮椅以足够的速度撞上一个5厘米高障碍物时发生完全向前倾倒（脚凳接触地面）。对于配备从最小到最大直径脚轮的轮椅，动态测试的平均倾倒速度分别为0.85（±0.08）、0.85（±0.08）、0.89（±0.07）和1.04（±0.14）米/秒。动态稳定性（y，倾倒速度，单位为米/秒）与脚轮直径（x，单位为厘米）之间的关系可以用方程y = 0.788 + 0.0139x - 0.00110x² + 0.0000276x³表示（p = 0.0001）。在轮椅设计和处方中应考虑脚轮直径与轮椅向前稳定性之间的关系。
