POSITIONING DEVICE FOR OPTIMAL ACTIVE KINEMATIC REAL-TIME MAGNETIC-RESONANCE-IMAGING OF THE KNEE-JOINT - A TECHNICAL NOTE

Objective. A prototype of a positioning device created especially for the diagnostic imaging of the patellofemoral joint was developed in or der to achieve reproducible examination conditions. Design. For this p urpose a clinical trial on healthy test persons was carried out under real examination conditions. Background. A special real-time MRI techn ique (Local-Look-technique) makes the analysis of active functional mo tion images possible, A prerequisite for this technique is accurate re producible positioning of the knee joint in the MRI unit. Methods. Thi s positioning device was evaluated during a total of 50 examinations o f the knee joints of five healthy test persons. The right patellofemor al joint of each test person was examined twice at different time poin ts in order to check the reproducibility of all examination conditions . Comparing two examination series from the same individual, reproduci bility of MRI slices was guaranteed by using identical anatomical land marks. Image quality and test-retest reliability were analyzed on the computer screen. Results. Optimal desired fixation of the leg in the M RI tube using the device was accomplished in all cases. The extent of motion of the knee joints ranged from 38 degrees (n = 2) to 40 degrees (n = 3) of flexion to full extension, which was satisfactory for the evaluation of the patellofemoral joint. Free movement of the patella a nd the lower leg was observed. The active functional MRI examination u sing this device was satisfactory and reproducible as assessed by test -retest reliability. Conclusions. The positioning device is a useful d evelopment in achieving active functional real-time MRI evaluation of the knee and patellofemoral joint. Using this diagnostic tool, reprodu cible quantitative examinations can now be easily per: The reproducibi lity and high reliability as well as its simplicity of operation rende r this diagnostic tool suitable for orthopedics and traumatology.