A visual tracking range of motion assessment system for lower limb joint

Abstract

Accurate range of motion (ROM) measurement of lower limb joint motion is important for assessing the severity of human lower limb injuries. It is essential for assisting the medical doctor and physiotherapist to determine the suitable treatment and rehabilitation exercises that are required for lower limb injury patient specifically. Current medical measurement systems such as Universal Goniometer (UGM) has a large resolution of 1° which may cause to have observation error while Electrogoniometer (EGM) is affected by the inaccurate sensor’s position and detachment when moving due to its mechanical properties limitation. Thus, a visual tracking ROM assessment system (VTS) for lower limb joint measurement is proposed. The purpose of this investigation was to develop a method to quantify a ROM of the lower limb joint and examine the ROM obtained between the VTS with EGM and UGM, for the measurement of lower limb joint angles. There were three major experiments conducted i.e., Validation Experiment, Clinical Test and Clinical Case Study. Validation experiment was done on the developed visual tracking system before being applied on the real human subject to ensure the system performance and safety to be acceptable. The system had been tested under the several of light intensity level, camera distance, camera elevation angle and markers location to determine the optimum operating condition. In clinical test, there were two tests carried out; they were Healthy Control Test and Injured Subject Test. A total of 20 healthy control subjects’ findings proved that the left and right lower limbs of human were similar (99.80% ~ 97.64% of similarity) for the normal healthy subjects. Comparison between VTS, EGM and UGM found that the accuracy for each two systems compared to each other was significantly different for the VTS vs. EGM and the EGM vs. UGM. The VTS vs. UGM produced the highest accuracy for all the joint motions compared to VTS vs. EGM and the EGM vs. UGM; it was 99.46% for left knee flexion. In addition, total of 70 injured subjects (included ankle joint, knee joint, and hip joint) had undergone injured subject test to compare its severity level between illness and three measurement systems. In the injured subject test, VTS yielded the smallest coefficient of variation (CV) compared to the EGM and UGM for Knee flexion for moderate injuries which was 2.45%.