Development of an Automatic Instrument for Efficient Measuring the Joint’s Range of Motion

A range of motion (ROM) has been measured using several indices to judge the progress of ankylosing spondylitis (AS). However, measuring and calculating the ROM is time-consuming & labor-intensive and it would be even difficult to measure accurately. Thus, an automated measurement system (AMS) is proposed & developed to measure the ROM more easily without any restraint sensor, and to recognize changes in the ROM more constantly with the same standard of measurement. The measurement items are neck cervical rotation, cervical lateral flexion, finger-to-floor distance, intermalleolar distance, and lumbar side flexion. Data from 30 healthy subjects were collected by the AMS and their motions were recorded simultaneously by installed webcams to acquire gold-standard data compared with the measurement value of the AMS. The accuracy was determined by calculating the standard error of estimation (SEE) and a possibility of replacement of measurement obtained by a physician using a protractor & ruler has been assessed by pattern recognition of Bland-Airman plots. These statistical results exhibit a significant degree of agreement with the novel AMS. The total measurement time for the 5 items using the proposed AMS was less than 5 min, which is faster than manual measurement. However, the measurement was conducted against only healthy subjects; therefore additional tests with AS patients will be required for utilization in clinical practice.