截癱與雙癱病患矯具髖關節之運動學分析與設計

Abstract

傳統的交替式步行矯具，其髖關節機構為一鉸鏈機構，限制了人體的髖關節運動，使其只能提供屈曲/伸展方向的運動但不容許髖關節的內外轉及內收/外展運動，這樣的限制將導致在正常行走時，由於無法像正常步態下做出骨盆旋轉的運動，而產生了非必要的補償運動。這補償運動將會影響所有的下肢旋轉運動，產生「之」字型的前進方式，且犧牲了正常的前進方式。我們認為，這「之」字型的前進方式，和所有下肢的不正常旋轉運動，是造成下肢癱瘓病人穿戴交替式步行矯具行走時，有較高的耗能的主要原因。 交替式步行矯具的過度耗能，在過去的文獻中有很廣泛的討論，但是卻沒有人仔細討論過往復步行矯具的髖關節機構，對下肢癱瘓的病人的下肢運動和步行效率的影響。 本研究目的為將機械手臂設計方式應用在設計矯具上，並且改善交替式步行矯具及髖矯具其髖部的運動，我們將機構固定在骨盆及大腿來引導並矯正髖關節的運動，利用逆運動學(Inverse Kinematics)來計算並設計其機構，而利用正向運動學(Forward Kinematics)來模擬預測穿戴不同的矯具機構時髖部的運動。 我們用Denavit-Hartenberg convention來表示從骨盆到大腿間其座標的旋轉及運動關係，並假設一正常人的步態行走時，將機構中心點決定在身側靠近解剖學上的髖關節，或是將中心點決定在腹部，此機構包含兩個方向的旋轉運動(flexion/extension, abduction/adduction)及一個方向的直線運動，用逆運動學的方式求得機構的相對運動關係，將其所得的參數設計出一「外展凸輪」，並將其裝置在往復式步行矯具的髖關節機構上，來模擬預測穿戴之後的行走方式。 結果發現，模擬穿戴之後的大腿引導、髖關節的運動、以及所模擬出的骨盆運動，相較於市售傾軸髖關節矯具的設計來的好，尤其是大腿在擺盪階段的引導上，能較接近正常人。 總結而言，本研究提出一髖關節設計方法，並模擬與討論其對下肢的運動與影響。外展凸輪在屈曲時病人可以產生適合的外展動作，但是在髖伸直時無法提供內收的動作。同時在髖伸直時站在足部的觀點來觀查，發現外展凸輪提供外展力矩給髖關節，就如同在行走時，初始單腳站立時，外展肌發動來支撐體重。而這會提供給病人多的外展力矩，對病人行走時能量消耗是很好的幫助。 未來的研究可將此設計概念化為產品，來做臨床實驗證實並比較其功效。

Conventional reciprocal gait orthosis (RGOs) configuration contains hinge hip joints, which restrict the anatomical hip joint to perform abduction/adduction and internal/external rotation. The restriction leads to an unwanted compensatory movement in order to achieve a pelvic rotation that is required in normal gait. The compensation generates a zig-zag progression through a whole lower limb rotation and sacrifices a normal gait straight progression. The abnormal progression and lower limb rotation are thought to be the cause of high energy cost for the paraplegic patients when wearing RGOs. The excessive energy consumption of RGOs has been comprehensively discussed in the past literature. Yet, there were few discussions about the effects of RGOs’ hip mechanism on gait dynamics and efficiency in paraplegic and diplegic patients. The purpose of this study was to apply robotics to orthotic joint designs. The results were used to improve the hip joint of RGOs and hip orthoses. The designed joint determined the movement of the pelvic and the thigh to guide the movement of the anatomical hip joint. The inverse and forward kinematics were used to design orthotic joints and simulate the movements of anatomical hip joint in RGOs and hip orthosis applications, respectively. Denavit-Hartenberg convention was used to present the relationship of orientations and position from pelvis to thigh. And the robotic mechanisms were assumed to be fixed on the body side near human’s anatomical hip joint or be fixed on body anterior during a normal walking, and the mechanism allowed two rotations (flexion/extension and abduction/adduction) and one translation. An “abduction cam” was designed by the results of inverse kinematics. The RGO’s hip joint mechanism was replaced by the abduction cam mechanism and used to simulate and predict the orthotics gait. The kinematics of hip joint movement with the abduction cam is much closer to normal than with the inclined-axis hinge joint system that is commercially available. The guidance of thigh and pelvic rotation movements in swing is particularly better. In conclusion, this study laid out theoretical work for the design of a new hip orthosis, and the effect of the mechanism on the lower limb movement was simulated and discussed. The abduction cam could guide well in flexion phase and generate appropriate abduction for patients, but the abduction is not satisfied in extension phase. In extension phase, as a view from the foot, the abduction cam supplies abduction moments for hip, as abductor firing at the initial of the single stance. The energy consumption will be saved by the external hip abduction moment, and will be very helpful for paraplegia patients. Future studies are needed to develop a prototype of the abduction cam, and to prove the effectiveness by carrying out clinical experiments.