A VIDEOFLUOROSCOPY METHOD FOR OPTICAL DISTORTION CORRECTION AND MEASUREMENT OF KNEE-JOINT KINEMATICS

Image distortion in video and image intensifier X-ray systems requires appropriate distortion correction meth ods to obtain accurate biomech anical quantitative measurements for joint kinematics applications. Th is paper presents an algorithm for coordinate reconstruction and disto rtion correction using a modified polynomial method. This algorithm wa s used for the measurement of patellar tendon moment arm, tibial plate au-tibial axis angle and patellar tendon-tibial axis angle during knee extension using videofluoroscopy in vivo. These parameters allow the determination of a two-dimensional biomechanical model of the knee for the measurement of muscle and joint forces during dynamic activities. Five males without knee joint injury history participated in the stud y. The mean measurement error obtained using an image intensifier-vide o system was 0.246 +/- 0.111 mm over a 180-mm x 180-mm field of view. The mean maximum patellar tendon moment arm was 39.87 mm at 44.9 degre es of knee flexion, The patellar tendon-tibial plateau angle was 112.9 degrees at full extension and decreased linearly to 87.6 degrees at 9 0 degrees of knee flexion. The mean angle between the tibial plateau a nd the tibial long axis was 84.8 degrees. Applications of the method i nclude motion analysis using video and X-ray fluoroscopy systems with non-linear distortion problems. Relevance Accurate measurement of anat omical parameters from videofluoroscopy systems is important for the d etermination of joint biomechanical models and measurement of muscular and joint forces.