3d Gait Analysis of Kinematic Pattern of Posterior Leaf Spring Orthosis

3D Gait Analysis of Kinematic Pattern of Posterior Leaf Spring Orthosis

Introduction:

Gait analysis can be as rudimentary as qualitatively assessing a patient's gait by visual assessment, or it can be as scientific as using sophisticated equipment like accelerometers, high-speed video cameras and optoelectric systems. Sophisticated gait analysis allows us to study human motion and even quantify it into data that can be analyzed and researched. This data can be useful in determining effectiveness of a variety of treatments including the application of a lower extremity orthosis like a PLS AFO (posterior-leaf-spring, ankle-foot-orthosis).

Collecting kinematic data involves "marking" the patient with strategically placed reflectors to identify important articulating skeletal landmarks. These markers reflect light to cameras fixed on the border of the walking runway. Even though the cameras only capture two-dimensional data, they use many computer-driven operations including direct linear transformation to create three-dimensional results from multiple 2-D cameras. Most kinematic gait laboratories sample movement from 60Hz to 120Hz, with some even reaching 10,000Hz (10,000 frames per second).

Most PLS AFOs are prescribed to limit excessive plantarflexion or to assist dorsiflexion at the foot. When muscle contractures or spastic muscles force a foot into plantarflexion, the PLS limits motion by using its solid shell design that fits on the posterior side of the leg and foot. It can be very effective in preventing and correcting deformities in the lower leg. The PLS can also aid weak or inoperable dorsiflexors, whether from muscle atrophy or a severed or damaged peroneal nerve, which innervates the dorsiflexor muscles. Without dorsiflexion, the foot would drag on the ground during swing phase without compensating by hip-hiking, vaulting, or circumduction mechanisms. It also positions the foot correctly to strike the heel first during initial contact, then progress to the ball of the foot during the loading response. During the midstance phase, its rigidity also limits excessive dorsiflexion but allows enough flexion for the knee to pass over the ankle. The final, terminal stance is characterized by a toe off, or plantarflexion, which the PLS allows to a certain extent. The PLS is different from the solid AFO in that it is semi-flexible to allow ankle dorsiflexion during the stance phase of walking, where as the solid AFO provides much more support but no flexibility during ambulation.

The purpose of this study is to explore three-dimensional gait analysis techniques and to use them to quantify and analyze the kinematic pattern of a PLS type AFO. One healthy subject's gait was analyzed with and without the PLS, to illuminate the effectiveness and changes the PLS type AFO had on the subject's ambulation.

3D Gait Analysis of Posterior Leaf Spring Orthosis Kinematic Pattern

Methods:

This study was conducted at the Baylor University Medical Center