Design & Development of a Novel Continuous Passive Motion (CPM) Device for GAIT Rehabilitation

Abstract

Human leg is one of the most important part in the human body. It helps a person in travelling from one place to desired destination and thus, act as primary vehicle for mobility. This process of locomotion is either achieved through walking or running. Also, it has been proven that this process of locomotion induces stress in the person’s body. By maintaining healthy legs and adopting correct walking methods, the generated stress can be reduced. The most important part in the human leg is the knee joint. It is a hinge joint which governs flexion – extension of the human leg and thus helps a person in locomotion. These actions can only be performed correctly by a healthy human leg (knee joint). Though the human leg plays such an important role in the locomotion of the human body, it is subjected to many injuries in this process like sprains, strains, burning sensation, calf pain, leg cramps, swelling and numbness of the limb. These injuries can be treated easily at home and does not require special treatment from a doctor. These injuries can be avoided by implementing the correct walking method of humans called bipedal human gait pattern. Adopting the bipedal human gait pattern in walking not only reduces the efforts in locomotion but also corrects the walking posture of the concerned person. Using this bipedal human gait pattern ensures the person of having the correct posture of thigh, lower leg and the heel.
To relieve a person from the problems of incorrect walking and post-treatment process, an inhome device was required. This indicated the need of a device which could ease out the posttreatment process for the patients. Therefore, this work presents the design and development of an orthotic device which integrates the bipedal human gait pattern in a continuous passive motion device. The most significant feature of the developed device will be its ability to involve bipedal human gait pattern while being light-weight, portable and cost-effective at the same time. The proposed device will be used in the first phase of rehabilitation during the post-treatment process or during no weight-bearing period. Controlling post-operative pain, reducing inflammation, providing passive motion in a specific plane of movement and protecting the healing tissue are the main aims of the first phase of rehabilitation. A CPM device helps in moving a joint through a controlled range of motion; the exact range is dependent upon the joint, but in most cases this range of motion is increased over time.
Procuring the bipedal human gait pattern involves a lot of complications and requires high level skills to guarantee perfection. Qualisys Track Manager (QTM) made this task easier with its four high speed cameras, clocking at 100Hz. QTM was used to capture the bipedal human gait pattern. In addition to retrieving the bipedal human gait pattern, incorporating it in a CPM device further raised the complexity of the project. Besides retrieving the bipedal human gait pattern, validating its imitation in the proposed CPM device was also done by QTM.
The research was carried out in two phases. The first phase of research involves the collection of data and the concept designing was done in Computer Aided Design (CAD) environment in Computer Aided Three Dimensional Interactive Application (CATIA) V6 software. The initial concept designs showed the need to provide proper rest to patient’s leg and that the usage of the designed CPM device must not induce any kind of stress or fatigue. For this very purpose, proper cushioning in the designed CPM device has been provided at all the contact points / surfaces of the patient’s body with the CPM device. The second phase involves the manufacturing the prototype of the CPM device. This phase also involves to program the CPM device to make it follow bipedal human gait pattern.