Development of a Technique to Quantify Stance Phase Kinematics in the Forefoot and Tibia
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Lower limb orthoses are relatively common devices used to restore functional mobility to individuals with pathologies that afflict the foot and ankle complex. In some instances, the foot shell may have to extend distal to the metatarsophalangeal joints consequentially imposing undesirable perturbations for portions of the gait cycle. While the importance of stance phase movements and the function of third rocker are well appreciated, the literature is sparse on actual kinematic data describing forefoot and tibia movements during walking in each of the three anatomical planes. This topic area of study was selected as an appropriate area in which we could develop a kinematic measurement system suitable for clinical use. Three specific design metrics were established for the measurement system. The first was quantifying movements in the three anatomical planes as well as the timing of stance phase. The second metric was that the system be capable of collecting repeatable data kinetic and kinematic. The third and final metric was that the system possesses design features suitable for clinical use. Inertial Measurement Units (IMU's) were selected for motion capture to quantify forefoot and tibia movements. The IMU sensors were affixed to custom molded interface shells for the tibia and foot respectively. Force resistive sensors were placed on the plantar surface of the foot at the calcaneus and the first MTP joint, allowing third rocker to be accurately defined. Both measurement devices were synchronized so that all data output could be integrated and analyzed. To test the system we designed a fundamental study to evaluate the movements of the forefoot and tibia during terminal and pre-swing phases of gait. The results appear to support the concept of a forefoot rocker during barefoot walking but further reveal that the "rocker-like" motion is multi-planar in nature. As expected there was variability in the timing, magnitude, and duration of movement between different subjects in each of the three planes of motion. Ultimately the knowledge acquired from this line of research could prove useful in a clinical setting; allowing analysis of patients' gait patterns for more accurate interpretation of alignment and performance of lower limb orthoses and prostheses.