Is the Kinect system suitable for evaluation of the hip joint range of motion and as a screening tool for femoroacetabular impingement (FAI)

BACKGROUND: In the clinical evaluation of femoroacetabular impingement (FAI), there is a lack of quantitative, reliable and informative assessment methods for the overall functional capability of an individual.OBJECTIVE: We compared clinical and radiological measurements of the hip joint with a new methodology based on the concept of 3-dimensional reachable workspace using Microsoft Kinect. METHODS: We assessed the correlation between the alpha angle of Notzli on full-length radiographs and the clinical internal rotation. We evaluated the accuracy of joint positions and angles of the hip between the Kinect system and clinical examination including range of motion (ROM).RESULTS: The results of our clinical trial with 24 study participants showed a significant difference between normal internal rotation (> 21°) and reduced internal rotation (≤ 21°) in comparison to the radiological alpha angle of Notzli (P=0.026). The acquired reachable Kinect data demonstrated a moderate agreement between the Kinect and clinical examination (correlation coefficients between 0.230 and 0.375).CONCLUSIONS: The findings suggest that a higher grade alpha angle of Notzli accompanies reduced clinical internal rotation. The Kinect system provides reliable results of hip ROM. However, further test series must be performed for the application of Kinect in the clinical evaluation of FAI.